tag:blogger.com,1999:blog-69643457133540574062024-03-05T07:06:23.042-08:00Cathodic Protectionall about cathodic protection system, impress current cathodic protection system, sacrificial anode cathodic protection system, design calculation for cathodic protection system etccathodic protection basics
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Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-6964345713354057406.post-75716228561480076252015-07-10T21:32:00.000-07:002015-07-19T21:00:39.458-07:00Thermit welding for easy wayStep by step <a href="http://magnesium-anode.blogspot.com/">Thermit welding</a> :<br />
1. clean the are<br />
2. adjust your wire<br />
3. please watch this video<br />
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081294392672 or 08565305351Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com2tag:blogger.com,1999:blog-6964345713354057406.post-79095389494269456622015-06-12T12:47:00.000-07:002015-07-19T21:01:08.373-07:00CALCULATION CATHODIC PROTECTION SYSTEM FOR PIPELINE<h1 dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 24pt;">
<span style="background-color: transparent; color: black; font-family: 'Arial Bold'; font-size: 14.666666666666666px; font-style: normal; font-variant: small-caps; font-weight: bold; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">CALCULATION <a href="http://magnesium-anode.blogspot.com/">CATHODIC PROTECTION</a> SYSTEM FOR PIPELINE</span></h1>
<h2 dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-top: 18pt;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: bold; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Under Ground Surface Pipe Area </span></h2>
<h1 style="margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 36.0pt; margin-right: 0cm; margin-top: 24.0pt; mso-list: l1 level1 lfo3; tab-stops: list 36.0pt; text-indent: -36.0pt;">
<b style="font-weight: normal;"><ol style="margin-bottom: 0pt; margin-top: 0pt;"><ol style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: bold; list-style-type: decimal; text-decoration: none; vertical-align: baseline;"></li>
</ol>
</ol>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-left: 63pt; margin-top: 3pt; text-align: justify;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The surface pipeline to be protected, as follows:</span></div>
<ul style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="background-color: transparent; color: black; font-family: Arial; font-size: 13.333333333333332px; font-style: normal; font-variant: normal; font-weight: normal; list-style-type: disc; text-decoration: none; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-top: 3pt; text-align: justify;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Length pipeline (L): 4.875 km</span></div>
</li>
<li dir="ltr" style="background-color: transparent; color: black; font-family: Arial; font-size: 13.333333333333332px; font-style: normal; font-variant: normal; font-weight: normal; list-style-type: disc; text-decoration: none; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-top: 3pt; text-align: justify;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Pipeline Diameter (d) : </span><span style="background-color: transparent; color: black; font-family: Symbol; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">∅</span><span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> 12 inch = 323.85 mm = 0.32385 m</span></div>
</li>
</ul>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-left: 63pt; margin-top: 3pt; text-align: justify;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Total surface to be protected (A) = </span><span style="background-color: transparent; color: black; font-family: Symbol; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">π</span><span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> * d * L</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-left: 63pt; margin-top: 3pt; text-align: justify;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A = 4957.33 m</span><span style="background-color: transparent; color: black; font-family: Arial; font-size: 8.799999999999999px; font-style: normal; font-variant: normal; font-weight: normal; text-decoration: none; vertical-align: super; white-space: pre-wrap;">2</span></div>
</b></h1>
<h2 dir="ltr" style="line-height: 1.2; margin-bottom: 3pt; margin-top: 18pt;">
<span style="background-color: transparent; color: black; font-family: Arial; font-size: 14.666666666666666px; font-style: normal; font-variant: normal; font-weight: bold; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> Demand of Current</span></h2>
<h1 style="margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 36.0pt; margin-right: 0cm; margin-top: 24.0pt; mso-list: l1 level1 lfo3; tab-stops: list 36.0pt; text-indent: -36.0pt;">
<span style="font-weight: normal;"><ol start="2" style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="font-family: Arial; font-size: 14.6666666666667px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"></li>
</ol>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Total demand current to given formula:</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="27px;" src="https://lh6.googleusercontent.com/MLqyiK_7FhxgjOR4dOL7N9371xBOGxNloR4slNQWwWBlAzTB4vwKihoZeR5Jm9kl7s0unyz4Zpd0SLbaJw8MrahWW_Km6oCrZN9YZABWmdZUsBo0qwuRTUhgpUMXYIaVUn7O7TXqMYk_f1DL" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="121px;" /></span></div>
<br /><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Where :</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 0pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="23px;" src="https://lh6.googleusercontent.com/X8VMVMvt1EQiU63hTDjSP_z7WmRnUlVKZJltJJ9-oI7xwf5yEACtyPPn3fsS86O-UHMXVM6I09hS7I1k7nrtm4zbThNivX23SORA5YMm9LHUHUntaFOik6BEyKshLT8PRBjrIQ_4FC6mSmFy" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="19px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">= Demand Current (Amp)</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 0pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"><img height="17px;" src="https://lh4.googleusercontent.com/CwsUPs6ThK4UAT1GJkAxkABAPsPNaU9-c6bmL0XFQ63ba-zUkIDFt7-aj67xgLBSp8KDwNm4pbi3iH6vv4rNmrWg0G6Bh8EFPSxiZ6AsWJ_vDKmoUlqvvTaMaaDFkKA-lQM-fBVyfNa99T9G" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="16px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> = Surface area to be protected (m</span><span style="font-family: Arial; font-size: 8.8px; vertical-align: super; white-space: pre-wrap;">2</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">)</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 0pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="23px;" src="https://lh6.googleusercontent.com/Qa7ANmoel5j2bY-Zz63wkgu03KgyIzQO6F9NLhe-bg2sUeoHwOp__0YDVGuTgIkFp4yvBFrFQ9fKp5PQpssGjrZb_Ssnw3VWmj97rMshWZ8tXM7Hy7eIVwfw_aDyFbzEo4GRiYZA4CtzmsGp" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="20px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">= Current density per m</span><span style="font-family: Arial; font-size: 8.8px; vertical-align: super; white-space: pre-wrap;">2</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> (mA)</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 0pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="23px;" src="https://lh6.googleusercontent.com/Ra3a4nIa6uv488Rq7wuZEi37nkTnnrKFJrHKwbA1aGBluggsqENV1klSPSSvSHcTTgcMSqRjd6OHd89qukGxoNdoSrhVtQoRa9dcy_yA1M3mmK8hZgFZfRft0y2BUS-PFdI05W0pgaUcQGfI" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="23px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">= Coating breakdown factor</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Therefore:</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="25px;" src="https://lh6.googleusercontent.com/8fWOnmfDAGBpyGhGg2nTWRbu8lyJ60MOWFsve-mEJQw-Pcv_7PNW1Lgmjn4axIlDR4cPZg0gSzRib-Et_PtuSUMsC1KsSU5aJ137xYvPlPuKPeK8HY7RqIOw4mHdPmVRkhpnvYs_iiDV9V6M" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="185px;" /></span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 63pt; margin-top: 6pt; text-align: justify;">
<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="23px;" src="https://lh6.googleusercontent.com/IAP8Ci5zORa-YtLOPBbsSSqQUrBx3hxWEU_2GhYXztwO3Awq3UgGeZWhxG8z1LEek0fLiB4w8I1CIPhIRSB2efonnGNlu6-1roR8-7XSWqgqlh4V6lPj04zd1BTfb1RhdP9Fy-ksDDV-5M8Q" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="81px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">mA = 0.992 Amp</span></div>
<br /><ol start="3" style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Resistance of Magnesium Anode for Kp 4+500</span></div>
</li>
</ol>
<br /><br /><div style="text-align: center;">
<img height="56px;" src="https://lh4.googleusercontent.com/l4r1xV-CnxbZcu8m1JkLNepBh9gsDqEwqwoGU8HPTiHbaLKNXn7zJ8Rm9g_nGeHTBUGcjpuAqevRSmeKjdcHGcPPxp47IzEe-x_PgIgI8YKRYZWeLYrreXLnRBo-Qi2NSTzOrwIpSOdfPT3-" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="240px;" /></div>
<br /><br /><br /><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">R</span><span style="font-family: Arial; font-size: 8px; vertical-align: sub; white-space: pre-wrap;">mg</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: <a href="http://magnesium-anode.blogspot.com/">Magnesium anode</a> resistance (Ohm)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">L</span><span style="font-family: Arial; font-size: 8px; vertical-align: sub; white-space: pre-wrap;">mg</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Length of prepacked magnesium anode 32lbs (m)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">0,9</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">m</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">D</span><span style="font-family: Arial; font-size: 8px; vertical-align: sub; white-space: pre-wrap;">mg</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Diameter of prepacked magnesium anode 32lbs (m)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">0,195</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">m</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Calibri; font-size: 16px; font-style: italic; vertical-align: baseline; white-space: pre-wrap;">ρ</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Layer Soil resistivity data at depth from survey (Ohm cm)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">5500 ohm.cm</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">R</span><span style="font-family: Arial; font-size: 8px; vertical-align: sub; white-space: pre-wrap;">mg</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= 25.3739 ohm</span></div>
<br /><ol start="4" style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Driving Voltage Anode</span></div>
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</ol>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Net Driving Voltage The net driving voltage between Magnesium anode of -1.6 V</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">(Cu/CuSO4 reference) is 0.75 V (1.6 - 0.85).</span></div>
<div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-left: 70.9pt; margin-top: 0pt;">
<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"> Close circuit potential (Volt) of magnesium is -1.6 volt</span></div>
<br /><ol start="5" style="margin-bottom: 0pt; margin-top: 0pt;">
<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Current of anode For Kp 4+500</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; font-weight: bold; vertical-align: sub; white-space: pre-wrap;"><img height="45px;" src="https://lh5.googleusercontent.com/A2BxDG6pMBqKtmzjBQPlTIJw-xE3AGhA2qT00RZWa8skaNCnA_lDTRcNeR1kfXWjZVRUGvwM6Mz5Maa4QHnjSzP6wheSwB1NKdWPJfAJkQ2Jfof0iatd3A0nTEZ_kicxUslO5lqd8VCNnmbq" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="91px;" /></span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Ia</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Magnesium anode current output (Amp) = (Ec - Ea) : Rmg</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Ipf</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Required current </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Ec</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Protective potential (Volt)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">-0,85</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Volt</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Ea</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">: Close circuit potential (Volt)</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">-1,6</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Volt</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">I = -0.85 – (-1.6) : 25.3739</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">I = 0.0296 A</span></div>
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<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Sacrificial anode requirement</span></div>
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<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Mass Metode </span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Total Sacrificial Anode weight to be given formula:</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="47px;" src="https://lh3.googleusercontent.com/LelBNkV1YcXuwbsk2MnW-DwmE_cpkxk_YlWe0e_FoFRDx2inFP1jnxEbYIJNYYpi1NWnG7OHcu2odHpsi51teolnMjhCdAqj4NCe5UJKzqrT6l6FKncS1hACrw4lpsrRuPPTyNJltrY_wAPG" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="100px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> </span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Where: </span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; font-style: italic; vertical-align: baseline; white-space: pre-wrap;">Y</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> = Design Live Period (year)</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; font-style: italic; vertical-align: baseline; white-space: pre-wrap;">S</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> = Consumption rate (kg/amp-year)</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="23px;" src="https://lh6.googleusercontent.com/X8VMVMvt1EQiU63hTDjSP_z7WmRnUlVKZJltJJ9-oI7xwf5yEACtyPPn3fsS86O-UHMXVM6I09hS7I1k7nrtm4zbThNivX23SORA5YMm9LHUHUntaFOik6BEyKshLT8PRBjrIQ_4FC6mSmFy" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="19px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">= demand current (Amp)</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; font-style: italic; vertical-align: baseline; white-space: pre-wrap;">f </span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> = Utility factor</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">So, total weight;</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="41px;" src="https://lh5.googleusercontent.com/iqk4zHbcIdW1SagaFtjwYBOjRH5EmK8HXia88LAO23bb0mPPF3HblxFDxzm2IVVfx4TvZsgnheruQtnOYMuTJpCn1mKsupGhl5wZ_4j0QmLmdIw7AIW9pWFXQlKLRpKWiMMAWK-KOiOfBlC_" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="123px;" /></span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="19px;" src="https://lh5.googleusercontent.com/PdL8iW4v2kQxkd1qqYTk_dIMEHrEPWylziaXWvjPpWld4LHHRUOMqJKrHurG2upsVvLZco_jEPlWB0Ni38AIZr8odmjoVf8EOyQPoRpVNACLDrFLVQ2tfSebPFSrQJl6SwY-xuQk54LU_UGS" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="69px;" /></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">kg</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="41px;" src="https://lh6.googleusercontent.com/7_5iIa-hnBHg5qqK9-eh99ruGXoh4HdUtwAy1IFZnaxWMh0lG8L9uymd4Q_9ijvUejF8boJUVMLAIVzJZPSb-02K6SZvYWWqGABnGYkpcYJDvwxcdL4dtON9IUZLZ8fFC15CyAUN9Rn7kgfJ" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="71px;" /></span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">N = 13.68 </span><span style="font-family: Calibri; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">≈</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> 14 Pcs</span></div>
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<span style="font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Current Output Method for Kp 4+500</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="41px;" src="https://lh6.googleusercontent.com/Bc3E3Y9wxdka8vdMoBEFWLbIZlWbxE_S0E5bWYhWRos8LeW8kU8eOdYPn46YJ86nLdFGV27XGHKUyjYvGJ5ay88PzBQMAenfB_mpTYOYStDWPcsu562JxhpRiMOJziTIGc-4DrOg9IU3Dw-s" style="-webkit-transform: rotate(0.00rad); border: none; transform: rotate(0.00rad);" width="51px;" /></span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Ip = Current Protective</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">Ia = Current Anode</span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: sub; white-space: pre-wrap;"><img height="41px;" src="https://lh4.googleusercontent.com/yMgxWifka4UgLZae5vpLSLtR16ui5MZk1BccJh135w56exoQmQngp4KOHHXAV5PbJ2CwE9kB3WmK9Mbmu8x0D165_1XQClP4RIBtYR-bzAfiEEOmuiK6PY2Ix5zd88ISJwkkzCvG4ghUWGln" style="-webkit-transform: rotate(0rad); border: none; transform: rotate(0rad);" width="80px;" /></span></div>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">N = 2.6 </span><span style="font-family: Calibri; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">≈</span><span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;"> 3 Pcs</span></div>
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<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Lifetime of anode</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Current capacity </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= mass anode : Consumtion rate</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Current capacity </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= 14.5 kg : 8 kg/amp.year = 1.8125 A.Y</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Life of anode </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= Current Capacity (A.Y) x N x </span><span style="font-family: Arial; font-size: 13.3333333333333px; font-style: italic; vertical-align: baseline; white-space: pre-wrap;">f</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"> : I</span><span style="font-family: Arial; font-size: 8px; vertical-align: sub; white-space: pre-wrap;">R</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Life of anode</span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= 1.8125 A.Y x 14 x 0.8 : 0.992 A</span></div>
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<span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Life of anode </span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space: pre;"> </span></span><span style="font-family: Arial; font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">= 20.46 Years > 20 Years</span></div>
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<li dir="ltr" style="font-family: Arial; font-size: 13.3333333333333px; font-weight: bold; list-style-type: decimal; vertical-align: baseline;"><div dir="ltr" style="line-height: 1.2; margin-bottom: 0pt; margin-top: 0pt;">
<span style="font-size: 13.3333333333333px; vertical-align: baseline; white-space: pre-wrap;">Total Anode Required</span></div>
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</ol>
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<span style="font-family: Arial; font-size: 14.6666666666667px; vertical-align: baseline; white-space: pre-wrap;">The total Anode required is 40 Pcs, weight is 32 lbs or 14.5kg for each. Uses Current Method for better distribution.</span></div>
</span></h1>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com2tag:blogger.com,1999:blog-6964345713354057406.post-65118937960966881172015-06-12T10:56:00.002-07:002023-09-22T01:00:25.984-07:00cathodic protection system for internal tank<div class="MsoNormal">
<b><span face="Tahoma, sans-serif" lang="EN-US" style="font-size: 10pt;">Basic calculation for<a href="https://www.solusikatodik.com/"> cathodic protection </a>system for internal tank</span></b></div>
<div class="MsoNormal">
<b><u><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"><br /></span></u></b></div>
<div class="MsoNormal">
<b><u><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Data:</span></u></b></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Atmospheric
Storage Tank:<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> - length : 11 m<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> - Diameter (D) : 38 m<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> - high of water level (L) : 9 m<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Current
Density (CD) :
55 mA/m<sup>2</sup><o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Consumption
Rate of Aluminum Anode : 3.5 kg/Amp
Year<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">life time design :
0.2 tahun<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Utility
Factor :
0.8 <o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<b><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Calculation:<o:p></o:p></span></b></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal" style="margin-left: 54pt; mso-list: l0 level1 lfo2; tab-stops: 36.0pt list 54.0pt; text-indent: -36pt;">
<!--[if !supportLists]--><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt; mso-fareast-font-family: Tahoma;">1<span style="font-family: 'Times New Roman'; font-size: 7pt; font-stretch: normal;">
</span></span><!--[endif]--><b><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Surface
Area (SA) </span></b><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> <o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> - SA bottom =
</span><u><span lang="EN-US" style="font-family: Symbol; font-size: 10pt; mso-ascii-font-family: Tahoma; mso-bidi-font-family: Tahoma; mso-char-type: symbol; mso-hansi-font-family: Tahoma; mso-symbol-font-family: Symbol;">p</span></u><u><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> x D<sup>2</sup></span></u><sup><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> </span></sup><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> =
<u>3.14 x 38</u><sup>2</sup> = 1134.1 m<sup>2</sup><br />
4 4 <br />
- SA wall = </span><span lang="EN-US" style="font-family: Symbol; font-size: 10pt; mso-ascii-font-family: Tahoma; mso-bidi-font-family: Tahoma; mso-char-type: symbol; mso-hansi-font-family: Tahoma; mso-symbol-font-family: Symbol;">p</span><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> x D x L =
3.14 x 38 x 9 = 1074.4 m<sup>2</sup> <o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> <sup> </sup>Total Surface Area = 2208.5 m<sup>2</sup> <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 36pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 54pt; mso-list: l1 level1 lfo1; tab-stops: list 36.0pt; text-indent: -36pt;">
<!--[if !supportLists]--><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt; mso-fareast-font-family: Tahoma;">2<span style="font-family: 'Times New Roman'; font-size: 7pt; font-stretch: normal;">
</span></span><!--[endif]--><b><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Current Requirement
(Ip)<o:p></o:p></span></b></div>
<div class="MsoNormal" style="margin-left: 36pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Ip = SA x CD<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 36pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> =
2208.5 m<sup>2 </sup> x 55 mA/m<sup>2 </sup><br />
=
121467.5 mA = 121.5 Amp<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal" style="tab-stops: 36.0pt list 58.5pt left 252.0pt 270.0pt; text-indent: 18pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">3 <b>Weight
of Anode (W)</b><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 36pt; tab-stops: 36.0pt list 58.5pt left 72.0pt 252.0pt 270.0pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">W<sub>Al</sub><b> </b>=
<u>Ip x Y x 3.5 kg/Amp Year</u> <br />
U<br />
= <u>121.5 Amp x 0.2 years x 3.5 kg/Amp Year</u><br />
0.8<o:p></o:p></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> =
106.3 kgs<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">4 <b>Number
of <a href="https://www.solusikatodik.com/">Aluminium Anode</a> (N)<o:p></o:p></b></span></div>
<div class="MsoNormal" style="margin-left: 78pt; tab-stops: 78.0pt; text-indent: -42pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Proposed
Aluminium Anode type 120 ADFB - Net weight = 12 kg/ea <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 78pt; tab-stops: 78.0pt; text-indent: -42pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">N<sub>Al</sub>
= W<sub>Al</sub> : 12 kg<sub><o:p></o:p></sub></span></div>
<div class="MsoNormal">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> = 106.3 kgs : 12 kg<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 78pt; tab-stops: 78.0pt; text-indent: -42pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> = 8.86 pcs </span><span lang="EN-US" style="font-family: Symbol; font-size: 10pt; mso-ascii-font-family: Tahoma; mso-bidi-font-family: Tahoma; mso-char-type: symbol; mso-hansi-font-family: Tahoma; mso-symbol-font-family: Symbol;">»</span><span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;"> 9 pcs<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal" style="text-indent: 36pt;">
<span face=""Tahoma","sans-serif"" lang="EN-US" style="font-size: 10pt;">Total = 9 pcs
Aluminium Anode type 120 ADFB<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com1tag:blogger.com,1999:blog-6964345713354057406.post-19695979102598570202015-06-12T10:26:00.000-07:002015-06-12T10:26:19.961-07:00TEST FACILITIES AND TEST POST LOCATIONS<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">In order to monitor <a href="http://magnesium-anode.blogspot.com/">cathodic protection</a>, we
must be able to contact the metal of the subject pipeline or structure.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">There was a time when contact was achieved
by driving a steel rod into the ground from above the pipeline, and making
temporary contact by piercing the coating. The main reason for discontinuing
this practice was the physical damage that was possible to the pipe metal
itself, and that damage that was caused to the coating. <o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">Most pipelines now have provision for
contact through electrical conductors connected to the subject metal in a
variety of ways.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The most common is a process known as
<a href="http://magnesium-anode.blogspot.com/">cadwelding</a>, which can result in a low resistance, permanent, electrical bond
between the copper conductor and the steel of a pipeline.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The disadvantage of this type of connection
is that it needs considerable skill to achieve a good connection, in some field
conditions. The joint must be carefully
inspected and the integrity of the coating must be tested before backfilling.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">We are all aware that copper and brass are
more noble than steel which will tend to disolve if coupled together in an
electrolyte. Cadwelding introduces such a ' bi-metalic coupling' to the surface
of the pipe and care must be taken that all metal is separated from the
electrolyte by a chemically impervious, electrically resistant coating. This coating must be compatible tho the
pipeline coating and to the insulation on the copper conductor cable.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The use of copper conductor cables also
introduces the possibility of a bi metalic coupling if its insulation is not
perfect. It should be remembered that
the voltage that we are measuring is between the potential of copper in a
saturated solution of its own salts, and steel in the local environmental
electrolyte. <o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">If the conductor to the pipe is severed,
then the voltage that we measure will be that between copper in a saturated
solutionof its own salts and copper in the salts that are present in the local
environment. This voltage will be very low, as the difference between the
potentials, will be small.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">Readings can be very confusing however as
they are sometimes affected by the cathodic protection current. Charges will be passing onto the broken
copper tail which is still attached to the steel of the pipe, due to the
galvanic activity, and this will cause a variation in the potential of the
ground in the immediate vicinity. The extent of this area of influence depends
on the area of contact between the copper and the electrolyte, and the
resistance of that electrolyte. <o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">If the conductor is not completely severed,
it will definitely draw currentfrom the ground, and this will have a
significant effect on the measured voltage if the insulation damage is close to
the electrode position.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The contact between the conductor and the
subject metal must have a low electrical resistance, as it may be used for
measuring current.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The best test facility is direct contact
with the pipeline at a riser but there are many sections of pipeline which are
buried with no riser.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">There was a period when some test posts
were connected to two conductors which contacted the pipeat two locations
exactly 100m apart. The purpose was to
enable current direction readings to be taken, but although I saw several
attempts to do this, I never saw it done successfully, or was never able to
obtain meaningful readings myself. I
read and understand the theory behind this type of measurement, but the
application seems impractical in field work.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The electrical resistance of the pipeline
itself is extremely low, for example a 4" dia. steel pipeline is 0.141
ohms per mile and a 24" dia. pipeline is an incredibly low 0.0161 ohms
per mile.(Peabodies) If we are dealing
with other structures such as storage tanks we can never consider the
resistance of the metal itself, as a significant feature in cathodic protection
calculations.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It therefore follows that the POTENTIAL of
the pipe metal does not vary significantly, over a 2km section of continuous
welded steel pipeline, with the diameters quoted. This matter was debated during the application
of over-the-pipeline potential surveys, conducted in the UK, on high pressure,
welded steel, gas mains.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">I was part of a team that carried out the
field test which resolved this matter, on a 2km section of 24" dia. welded
steel, coal tar enamel coated, buried pipeline.
This pipeline was protected by impressed current cathodic protection
which was switched on continuously during these tests.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The negative pole of a high resistance
voltmeter was connected to the test post conductor terminal at the top of a
test post at location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">A standard copper/copper-sulphate electrode
was placed in a fixed position at location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">A reel of armature wire was used to connect
the electrode to the positive pole of the high resistance voltmeter and the
reading was noted.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The wire was reeled off the spool and used
to make contact with a standard copper/copper-sulphate electrode at location B,
which was 2km distance from location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">A changed voltage was noted on the meter,
which was still connected to the test post at location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The change of standard electrode positions
had significantly altered the recorded voltage.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The armature wire was then used to connect
the negative pole of the voltmeter to the distant test post at location B.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The positive pole of the voltmeter was then
reconnected to the electrode at location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The voltage on the meter was identical to
the first reading.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">Altering the position of contact to the
pipeline, by a distance of 2 km, had no detectable influence on the voltage
measured.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The meter was taken to location B and
connected between that test post terminal and electrode B.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The voltage recorded was identical to the
second voltage of the test, confirming that the location of the electrode is
the only significant feature.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The positive pole of the meter, at location
B, was then connected to the armature wire which was connected to the electrode
in the fixed position at location A.<o:p></o:p></span></div>
<div class="MsoNormal">
<span lang="EN-US">The voltage recorded was identical to the
first voltage recorded confirming, once more that the point of contact to the
pipeline has no detectable effect on the recorded voltages.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The discussions culminating in this test,
resulted in a re-appraisal of test post locating within the operating
company. It was decided that fewer test
posts were needed, and that the priority importance was access to the test post
locations.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The best form of test post, for a steel
pipeline consists of a steel bar welded directly onto the pipeline metal and
protruding through the surface of the ground directly above. This is protected
by encasement in a concrete block, which includes a vertical 4" dia.pipe
filled with the local ground material.
The standard electrode would always be placed in the top of 4" pipe
for the purposes of periodic voltage measurements.<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<br />
<div class="MsoNormal">
<br /></div>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com2tag:blogger.com,1999:blog-6964345713354057406.post-61353920206859307662015-06-12T10:19:00.003-07:002015-06-12T10:19:42.954-07:00Measuring the effects (CATHODIC PROTECTION)<br />
<div class="MsoNormal">
Measuring the effects</div>
<div class="MsoNormal">
<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<a href="http://magnesium-anode.blogspot.com/">Cathodic protection</a> has been extremely cost effective since
first used, but there have been instances throughout its history, where
corrosion failures have occurred in spite of it's use.<o:p></o:p></div>
<div class="MsoNormal">
The problem is to measure the effectiveness of cathodic
protection. Corrosion is
electro-chemical and this suggests that electrical metering can be used for
short term monitoring.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The simplicity of the circuit of a single <a href="http://magnesium-anode.blogspot.com/">corrosion cell</a>would tend to suggest that there is a simple means available to make the
required measurement. Standard
reference electrodes have a recognised and known potential which can be used as
an electrical datum point against which to measure other potentials, in a
laboratory.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
We normally measure VOLTAGES which are the differences
between two potentials.<o:p></o:p></div>
<div class="MsoNormal">
This causes confusion because the readings are commonly
called "potentials", where in fact, either of the two potentials can
be regarded as zero and the other will be either higher or lower. The meter will show positive or negative
values according to the polarity of the connecting conductors.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Cathodic protection theory dictates that the metal must be
reduced to below its corrosion potential IN RELATION TO A STANDARD REFERENCE
POTENTIAL. These potentials can be
measured in a laboratory where it is possible to control all elements of the
circuit, but it has proved impossible, so far, to measure the required
potential in field work.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The problem with field measurements, is that the earth at
one location has never exactly the same potential as the earth at another
location. In a laboratory, the
electrolyte is contained in an electrically insulated container and the
currents are all in closed circuit and related to the corrosion reaction. The potential of the electrolyte can be
measured at the reaction interface by the use of a glass capillary containing
an inert, but conductive, electrolyte such as agar-agar gel. This cannot be achieved in field work,
although a close approximation has been achieved by Dr Prinz of Rhurgas, in
Germany.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Field readings taken and analysed in the established way are
not related to each other, except through the low resistance of the pipeline
itself. This is easily demonstrated by
a simple calculation base on Ohms law as follows.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Take any sample readings from a typical pipe-to-soil
"potential" cathodic protection survey and work out the amount of
current that must be passing through the pipeline between any two cathodic
protection test facilities. It will be
found to be ridiculously high, to the extent of being unbelievable.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
For example, a span of 24"diameter steel pipeline ten
miles long will have a resistance of about 0.001 Ohms, depending on the wall
thickness, and the readings at either end of the span might be -0.950 volts and
-1.250volts. This would not cause
alarm, and would be plotted on an 'attenuation curve', without too much
comment. However, calculation shows
that, if the 'half-cell' (electrode) is truly a reference, then there is a
volts drop of 0.300 over the ten mile span.
This seems reasonable until it is realised that with such a low
resistance there must be 300 amps passing through the pipeline. Something is quite clearly wrong with the
measuring system or the theories.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
This has not been seen as a major problem until pipelines
became so widespread and numerous that reliability became a major industrial
consideration. Even now there seems to
be little concern with this subject until a failure causes financial
losses. The public at large are not
even aware that the inadequacy of present technology could result in an
unforeseen disaster.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
As far as I'm concerned, the more fucking pipelines that
blow up the better. I'll put my price
up.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Before going any further it is necessary to imagine
electricity and this has been likened to water pressure, with containers
connected by pipes to allow current to flow.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The pressure is caused by the height of the water in each
container and not the weight. The water
will fill any connecting tube and then the pressure downwards will be greater
in the vessel which has the highest level.
The reason for this is obviously due to the imbalance between the
pressures in the two containers and electrical potentials have the same
tendency when connected by conductors.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRnQkE8mw6WMHB1S-K-C4AbpGVfANDdjdZUAdT9muzx5K0NmFcqBS32gFezQfNMIwW-d-0tbRVp8HZqOGMvTWCeojUk9SJ4fXKhe83caSFGTt-N5ZgIKDPanECuZtAzisnDmzbEYgQDvM/s1600/CATHODIC+PROTECTION+FLOW+WATER+2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRnQkE8mw6WMHB1S-K-C4AbpGVfANDdjdZUAdT9muzx5K0NmFcqBS32gFezQfNMIwW-d-0tbRVp8HZqOGMvTWCeojUk9SJ4fXKhe83caSFGTt-N5ZgIKDPanECuZtAzisnDmzbEYgQDvM/s400/CATHODIC+PROTECTION+FLOW+WATER+2.png" width="400" /></a></div>
<br />
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="MsoNormal">
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<div class="MsoNormal">
This is fine when visualising a simple circuit such as a
single corrosion cell or a dry cell battery connected through a light bulb, but
in a cathodic protection circuit, or when corrosion takes place on a pipeline
we have no means of measuring each separate cell in this way.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If we examine the technique that is used in the laboratory
then it becomes clear that provision has been made to eliminate outside
influences in this 'open circuit measurement'.<o:p></o:p></div>
<div class="MsoNormal">
This is not possible in cathodic protection field work, and
yet laboratory derived theories are applied to readings obtained in the field.<o:p></o:p><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdi3YJOHfIqmKVL2Ww68a0DEw492t1kLLjnxESjjN_V8qTZZFPLpXrIfkBxiRvW9oEtUtoxNWNcRwKTjgIrnGWY-XY-QfxMUcf0WJbQnnoAO1sb_VaHJ7ulzn-Z7lt1X7pQvltq10SqHg/s1600/CATHODIC+PROTECTION+FLOW+WATER.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="195" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdi3YJOHfIqmKVL2Ww68a0DEw492t1kLLjnxESjjN_V8qTZZFPLpXrIfkBxiRvW9oEtUtoxNWNcRwKTjgIrnGWY-XY-QfxMUcf0WJbQnnoAO1sb_VaHJ7ulzn-Z7lt1X7pQvltq10SqHg/s400/CATHODIC+PROTECTION+FLOW+WATER.png" width="400" /></a></div>
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<div class="MsoNormal">
It can be seen that it is impossible to measure the pressure
differences in each cell by making a single connection to the common reservoir
at the bottom. However it would be
possible to stop the flow of water from the highest level in the small vessels
by adding a supply of water from a higher level.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
However, it can be seen that the pressure measurement in
such a system would need to be between the lowest water level and the highest
water level in the whole system. This
would be a much greater voltage (Vp in the drawing) than that required to stop
the flow in the single cell with the biggest differential.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Comparing electrical pressure with that of water is a good
starting point, but it is better to imagine electricity as simply a pressure
which can pass through conductors, and is restricted by resistances.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Imagine trying to measure the gas pressure within a
cylinder. We must allow that pressure
to act on a meter which will guage the pressure. This action will consume some of the gas
within the cylinder and it is the passage of the gas which makes it possible to
measure the pressure itself.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The same rule applies to electrical pressure and this used
to cause considerable inaccuracy in voltage measurements until the digital
meters made it possible to measure voltages while drawing very little current.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Back to the gas cylinder and imagine measuring the pressure
with a guage which draws very little gas.
We still have the problem that this pressure has to be compared to
something. In the case of gases, we can
related this pressure to atmospheric pressure, displayed in such a way that we
can imagine its effect on our senses.
We are aware that we are all subject to atmospheric pressure and the
effect of increasing the pressure on the human body can be felt, when swimming
under water, for example. We use our
muscles to compress stale air which is then exhaled and can feel the current of
air through our nose and mouth. Gas
pressure is therefore part of our lives with which we are familiar. We can use this experience to imagine
electrical pressure, which has similar qualities.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Everything has an electrical potential (pressure) which has
the tendency to equalise on contact with another item of a different
potential. It is this tendency which
causes current to flow and allows us to make.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
In the same way that chemical reactions can give off gas,
and increase the pressure within a cylinder, for example, chemical reactions
can cause an electro-motive-force (EMF) which increases the electrical
pressure, or potential, on one side of the reaction.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
In order to measure the electrical pressure of this reaction
we must complete a measuring circuit with a low resistant electrically
conductive path. The whole measuring
circuit reaches equilibrium with a small amount of current flowing depending on
the requirement of the meter.(in the case of digital meters, the current
required to make the measurement is very small).<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
In the case of measuring the voltage of a dry cell battery,
we connect a voltmeter between the poles of the battery and the voltage is the
difference in electrical pressure caused by the chemical reaction at the
interface between the electrolytic paste and the inner surface of the metal
container and the electrode which serves as the positive pole of the battery.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The technique is simple because it is possible to confine
the path of the current to that of the measuring circuit and each element of
this circuit can be evaluated. Voltage
drops can be measured around the circuit, using independent meters and
measuring current can be detected by magnetic field and other techniques.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Natural corrosion cells are much different, as they can be
physically minute or large. Large
corrosion cells can contain micro-cells within the same area where anodic areas
completely surround cathodes or vice-versa.
When studying such cells, we are not able to separate the component
parts, and the measurements have come to be known as 'open circuit
measurements'.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
This type of measurement involves connections to the
electrolyte as well as the metal and this requires the use of an
electrode. There is a danger that this
will introduce another EMF into the circuit, by the reaction between the
electrode and the electrolyte. We
therefore use an electrode in a solution of its own salts, which has a known
reaction EMF. We can then make a
connection between the electrolyte in the cell and the earth electrolyte, in
the hopes that there will be no electrical disturbance to the measuring
circuit.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
In the laboratory, this disturbance is prevented by the use
of a glass capillary filled with inert gel, which is used as a conductor from
the reaction interface to the reference electrode. The reference electrode is a metal in a
saturated solution of its own salts, as this has a known reaction
potential. Reference electrodes are
related to each other by known voltages and are used as international
standards. Without this consistency it
would be impossible to evaluate the reaction, develop theories or design
cathodic protection systems etc.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Unfortunately, it became the practice to apply the same
principles in cathodic protection field work.
It seems that many thought that the electrode could be regarded as a
reference against which other potentials can be established. They thought that pipe to soil voltages were
pipeline metal potentials which could be plotted against a fixed potential
supplied by the use of the 'reference electrode'. There are still remnants of this concept in
cathodic protection practice today, which are manifest in 'attenuation curves'
etc., which are used by some in the design of CP systems.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
This subject can now be studied in greater detail by
computer modeling which makes it much clearer that the fixed potential is
normally that of the pipeline metal, and the variation in the measured voltage
is due to the different potentials elsewhere in the measuring circuit.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Imagine that we require to know the voltage of two dry cell
batteries which are arranged in parallel.
That is to say that each is in connection with a common conductor to the
positive pole and another common conductor to their negative poles. Both conductors would carry equilibrium
current according to the reaction within each battery and the voltage between
the two conductors could be measured by connecting a meter between the
two. Unless the two cells are
separated, it is impossible to evaluate the voltage of each battery. Even this is not as complex as the
expectancies of cathodic protection monitors.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If we take two batteries and half bury them in an
electrolyte with their positive poles exposed and connected, we have two
corrosion cells in closer condition to those found on a pipeline. A circuit drawing of this arrangement will
show that current will pass through the ground to equalise the pressures caused
by the interface reactions within each battery.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
We must now try to evaluate the reaction within each battery
using a high resistance voltmeter and an electrode. We cannot break the circuit or separate the
batteries but connections can be made to the metal or the electrolyte or
both. It will be seen that we are only
capable of measuring voltages across various spans of the circuit, and cannot
establish a reference within that circuit.
The laboratory techniques cannot be applied to these conditions as there
are too many variables which are impossible to evaluate.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If we increase the number of half buried batteries connected
together, we improve the similarity to a pipeline, but in order to be more
realistic, we must include some which have their positive poles buried. The complexity of the situation is now
apparent and what seemed to be a simple measurement, now seems almost
impossible.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
A circuit diagram of the complex arrangement will show that
a different voltage will be measured with every new position of the electrode,
and this is born out in cathodic protection field practice. It is especially obvious on pipelines which
are not connected to <a href="http://magnesium-anode.blogspot.com/">cathodic protection</a> systems and which have poor coating.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The different voltages are due to the variety of potentials
at each pole of the voltmeter. These
can be caused in many ways, as described later, but it is important to realise
that they are all components of the voltage shown on the meter. It is possible to eliminate them in the
laboratory but not in the field, therefore they must be evaluated and
considered in the analysis of survey results.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The problem is even more complex when <a href="http://magnesium-anode.blogspot.com/">cathodic protection</a> is
introduced as this is an additional voltage which is superimposed over all the
others. Being designed to drain charges
from the whole of the pipeline, it has an effect on the equilibrium of all the
other electrical influences. However,
the dynamic effects of an impressed current system can be removed by taking
voltage measurements immediately after the system has been switched off. This cannot be achieved where sacrificial
anodes are used, unless they have a special facility designed for this purpose
at construction stage.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The voltages obtained between the pipeline metal and a
randomly placed electrode have a certain amount of value when compared to
others obtained from connections to the same pipeline. This is because of the very low electrical
resistance in this part of the corrosion and cathodic protection circuits. <o:p></o:p></div>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com1tag:blogger.com,1999:blog-6964345713354057406.post-77660760776491332012015-06-12T10:12:00.001-07:002015-06-12T10:12:44.748-07:00EXPERIMENT HOW TO UNDERSTAND VOLTAGE OF CATHODIC PROTECTION SYSTEM<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It is possible to make a model of electrical components to
demonstrate further complications involved in DC electrical fields of this
nature.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<a name='more'></a><br />
<div class="MsoNormal">
Two chains of randomly selected resistors are soldered
together, linking two different potentials such as the poles of a dry cell
battery. The probes of the voltmeter
can be placed in any position along either of the chains and a different
voltage will be displayed.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<o:p> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQffHYVr_x68jNERQoI6RWS6sFe-hkdP1TYLfiiyZhy-doLTMNkRaYNmETpFo_SJwA1abNE88Yqb42FnkhHM32jnbs32Ecuw3wlxnoWDHW5OLjqflsTT0AswZJPiod-on8j1QgU2QKElU/s1600/cathodic+protection+system+battery.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="333" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQffHYVr_x68jNERQoI6RWS6sFe-hkdP1TYLfiiyZhy-doLTMNkRaYNmETpFo_SJwA1abNE88Yqb42FnkhHM32jnbs32Ecuw3wlxnoWDHW5OLjqflsTT0AswZJPiod-on8j1QgU2QKElU/s400/cathodic+protection+system+battery.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
</o:p></div>
<div class="MsoNormal">
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<div class="MsoNormal">
The number of variations in voltage between the two nodes is
equal to the square of the number of resistors.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If a grid of resistors is constructed with random values,
and the probes of the voltmeter are placed at various locations in the grid, it
would require a computer to predict the results.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Put a third dimension onto the grid, and a very powerful
computer would have to be fed with every resistance value in order to predict
the voltage resulting from the probes placed at surface nodes.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Two or more resistances of unspecified value included in the
system would make the result impossible to predict by any computer. (However it is true that given the same
source voltage, the voltage between any two nodes would be constant.)<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
FIELD EXPERIMENTAL WORK<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It is possible to apply this principle of an 'electrical
picture' to field work by a simple experiment.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Choose a buried, insulated, cathodically protected pipeline
running through areas of soil of different resistances. Place a metal coupon in high resistance soil
and another in low resistance soil, both connected to the pipeline. Using two copper/copper-sulphate electrodes
as probes, connected to the poles of a high resistance voltmeter<o:p></o:p></div>
<div class="MsoNormal">
plot the potentials surrounding the coupons. In the case of the high resistance soil, the
'potential gradient' will spread much further than that from the coupon in the
low resistance soil.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The area of influence of the coupon can vary from a few
millimeters in low resistance soils, to many meters in extremely high resistant
circumstances such as fresh water, sand and gravel. As a result, it is sometimes not possible to
detect a corrosion cell or even a coating fault at ground level, if the
resistance of the soil is too low, and the amount of current is small.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The effect of this can be seen in a drawing showing a single
corrosion cell, where the back-fill is homogenous. <o:p></o:p></div>
<br /><div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It is clear that the exact distance between each probe and
the actual interface between the metal and the electrolyte is crucial to any
calculation of the interface potential.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The most basic measurement in cathodic protection work is
described in Procedure 1, and is known as the 'pipe to soil potential'.<o:p></o:p></div>
<div class="MsoNormal">
The vast majority of existing cathodic protection records
are composed of these readings which are in fact voltages.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
A direct metalic connection is made to the steel of the
pipeline and the other pole of the
voltmeter is connected to a copper rod suspended in a solution of copper
sulphate in a container with a porous base.
This base is placed in contact with the ground and the resulting voltage
is recorded.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It has been seen from the sand tray experiment and from the
experiment with the steel coupon in contact with the pipeline, that the actual
potential of the ground can vary. When
carrying out Procedure 1, it is often possible to obtain significantly
differing readings by altering the position of the electrode within the radius of
the connecting lead. Errors as high
as 30% or more are common for this
reason and it can be imagined the voltages obtained by a left handed engineer
would differ from those of a right handed engineer, under certain
circumstances.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
One example of where this was known to have happenned was at
a pipeline cathodic protection post where the copper connecting lead to the
pipeline, had faulty insulation just below ground level. This would cause current to flow into the
copper for two reasons. Cathodic
protection current would follow this path being the least line of resistance,
and the less noble steel of the pipeline would tend to discharge current to the
copper as the cathode of a bi-metalic corrosion cell. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Current flowing into the copper caused a considerable
voltage gradient in the soil for about 1/2 meter, and this caused the meausred
voltage to drop from -.950 volts, which was considered to be protected, to
-.750 volts which was considered not to be protected. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Another example occured during an 'over the line close
interval potential survey' where a depression in the ground voltage was caused
by a galvanised fitting to a steel 'well-point tube' which had been abandonned
during the construction of the pipeline through waterlogged soil. In this case there was no connection between
the pipeline and the scrap, and certainly no influence on the corrosion control
of the pipeline, and yet the survey results showed the the pipeline was
unprotected at this exact spot and adequately protected one meter distant.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It is crucial that cathodic protection engineers and
technicians understand the nature of DC electricity and the significance of
these voltage measurements.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
It is no good understanding thermo-dynamic
theory and complex formulae if their components are grossly inaccurate. Many measurements made in laboratory
conditions cannot be made in field practice and it follows that an immeasurable
criteria is about as useful as an elastic tape measure.<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<br />
<div class="MsoNormal">
<br /></div>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com1tag:blogger.com,1999:blog-6964345713354057406.post-35359147662559790732015-06-07T23:44:00.002-07:002015-06-07T23:44:38.992-07:00Dangerous Coating Breakdown Factor<br />
Explosion of gas pipeline because wrong protection the pipeline. this because a little bit coating breakdown. Just a very little bit but give more lose<br />
Cathodic Protection System will protect pipeline from this thing.<br />
i will show you why coating breakdown will destroy the gas pipeline<br />
dangerous of coating breakdown factor<br />
How to stop this , please visit http://adf.ly/1IRzbh.<br />
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<br />Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com1tag:blogger.com,1999:blog-6964345713354057406.post-79426615993006506322015-06-07T23:01:00.000-07:002015-06-12T04:09:11.116-07:00basic cathodic protection system for presentation, dasar proteksi katodikbasic <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection system for presentation, dasar proteksi katodik<br />
Presentation of cathodic protection system, basic about <a href="http://magnesium-anode.blogspot.com/">cathodic protection</a> system if any question, please contact me (08565305351 - bajakz@gmail.com)<br />
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<br />Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com0tag:blogger.com,1999:blog-6964345713354057406.post-6102535619693533022015-05-18T16:44:00.003-07:002015-06-12T04:12:41.359-07:00CONCEPT CATHODIC PROTECTION SYSTEM<br />
<br />
The basic concept of <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection is that the electrical potential of the subject
metal is reduced below its corrosion potential, and that it will then be incapable of going
into solution, or corroding.
<br />
<br />
This mechanism has been defined by many scientists and has become established beyond
dispute. Indeed the principles of corrosion reactions are used in the design and
construction of expendable and re-chargeable batteries and accumulators which play such
a major part in modern life.
<br />
<br />
A battery that is 'dead' has no energy left and does not corrode any further. Likewise a
car battery on charge does not corrode, in fact in this case the reaction is reversible, and
energy is 'pumped back in'.
<br />
<br />
However, a battery has a very carefully composed electrolyte which has qualities to
ensure a predictable reaction with the other components of the battery. We know that the
corrosion within a battery can be controlled very accurately, by external electrical input,
as this technique is in common use with rechargeable batteries which are nowadays
controlled by computers which balance the reaction equilibrium to suit their own power
demands.
<br />
<br />
Unfortunately a <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection system is not composed of simple elements in the
way that batteries are, because the electrolyte is the ground itself. This electrolyte is
uncontrollable and has an almost infinite variety of qualities. The chemical composition
and electrical conductivity can span a vast range, as can the temperatures and pressures to
which the reaction is subjected.
<br />
<br />
<a href="http://magnesium-anode.blogspot.com/">Cathodic</a> protection of such subjects as ships hulls and storage tank bases is relatively
simple as the electrolyte is likely to be almost homogeneous, but as the size of the
structure increases, it extends through different electrolytes and the reaction at each
interface varies.
<br />
<br />
Offshore oil rigs, for example have different temperatures and pressures at the sea bed to
those at the surface, and a study of this situation has shown that it has a substantial
influence on corrosion.
<br />
<br />
Pipelines can be regarded as many interface reactions connected together in parallel.
The metal element can be well defined, as this is specified to a high degree by the
designers, as is the coating material.
<br />
<br />
However it is accepted that no coating can be perfect, and the faults, or 'Holidays'
introduce the first indefinable variable to the system.
<br />
<br />
During the construction of a pipeline all possible measures are taken to detect and repair
coating faults, so it follows that those remaining are undefined. It is possible to calculate
the theoretical resistance of a perfectly coated pipeline, given the specification of the
coating and dimensions of the pipeline, but it is impossible to calculate the actual
resistance of the total pipeline.
<br />
<br />
The electrical current measurements, taken during routine <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection
monitoring, show that there is little resistance in the total coating (with faults) of a
pipeline and this can be explained by the difficulty in quality control, during the
construction period.
<br />
<br />
Undetected coating faults are the path of <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection current and a perfect coating
would prevent any output from the CP system. We therefore, know that there are many
unspecified 'metal to electrolyte' interfaces present on an average pipeline.
<br />
<br />
The electrical resistance of the pipeline metal itself can be calculated, and is found to be
very low. In fact the effect that the pipeline resistance has on the complex current paths
and variation in potentials, is so small that it can almost be ignored.
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4SpVB1ACYAdohUOkfbn8fWxNniFtkSVZJSlYsh6yGvaMMxfsn0-rVVDvUpDfQn0YQfiqdGQtSNK8f0GnqAw2mMn3vR7s79SsWVKHXcrMdar75-BqoR36ZXVF_zUwudC8U8P90-GqClv0/s1600/concept2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4SpVB1ACYAdohUOkfbn8fWxNniFtkSVZJSlYsh6yGvaMMxfsn0-rVVDvUpDfQn0YQfiqdGQtSNK8f0GnqAw2mMn3vR7s79SsWVKHXcrMdar75-BqoR36ZXVF_zUwudC8U8P90-GqClv0/s320/concept2.jpg" width="286" /></a></div>
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<br />
<center>
<img align="Middle" src="concept2.jpg" /></center>
The complication is due to each interface being capable of a different reaction, electro-
motive-force (EMF) which cannot be measured as it is in parallel with all other EMF’s on
the same section of pipeline. The magnitude of the current from each of these reactions
is dependent on the earth resistance immediately adjacent to the interface, and the
direction of all the resulting currents is the result of the combined effects of all the
resistances and electrical pressures caused by all the EMF's.
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHNUtq8UNQrH-68pCIKtYHH4ja4YA-Fyay998p71ivuB_xEGUnwzDxrmrLcSHKKyIkkvdRvL54KQ7K8vp6-0hjxhJKT1xTjCWw1g5-aShKyNrCD72iWnsDdzPmXWERfPJ63lrnCcT0SZ4/s1600/concept1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHNUtq8UNQrH-68pCIKtYHH4ja4YA-Fyay998p71ivuB_xEGUnwzDxrmrLcSHKKyIkkvdRvL54KQ7K8vp6-0hjxhJKT1xTjCWw1g5-aShKyNrCD72iWnsDdzPmXWERfPJ63lrnCcT0SZ4/s320/concept1.jpg" width="320" /></a></div>
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<br />
<center>
<img align="Middle" src="concept1.jpg" /></center>
Although it is simple to understand each corrosion cell and the mechanism of corrosion
itself, the reality of applying the science, to the field, becomes immensely complex.
This becomes more obvious when the circuit has been subject to computer modelling as
discussed later.
<br />
To be effective, <a href="http://magnesium-anode.blogspot.com/">cathodic</a> protection must reduce the metal at each single interface, to
below it's corrosion potential. This is not too difficult to achieve, as each interface is part
of the same metal structure, which has a very low electrical resistance. The difficulty is
knowing when all the interfaces have been reduced to below their corrosion potential in
relation to the electrolyte in their reaction vicinity. ( Don't forget, if we knew where each
interface was we would repair them all!!!!)
<br />
<br />
<br />
<center>
<h2>
OVER PROTECTION</h2>
</center>
There are several other problems, however, as too much current passing onto a steel
surface can cause embrittlement, which under certain circumstances can be as detrimental
as corrosion itself. This is manifest in such applications as the protection of the external
surfaces of drill pipe casings, where a considerable amount of<a href="http://magnesium-anode.blogspot.com/"> cathodic</a> protection current
is used.
<br />
<br />
<br />
<center>
<h2>
CATHODIC DISBONDMENT</h2>
</center>
Another fear of 'over-protection' is that of <a href="http://magnesium-anode.blogspot.com/">cathodic </a>disbondment of the coating. This
happens when the coating manufacturers specifications are exceeded. <a href="http://magnesium-anode.blogspot.com/">Cathodic </a>
protection current passing onto the metal causes the release of hydrogen which disbonds
the coating. In reality this is rarely a problem, and a careful study reveals why.
<br />
<br />
The current will only pass onto the metal at a coating fault, and the density of the current
will depend on the size of the coating fault and the current locally available. As the
current blows the coating from the metal, the volts drop at the interface will decrease, and
equilibrium will be reached with a very small increase in additional disbondment.
<br />
<br />
If there is no coating fault, then no cathodic disbondment will occur as recognised in the
British Standard Code of Practice for testing the coating manufacturers specification.
This requires a specific size of coating fault on a steel coupon, to be subjected to an
increasing voltage over a specified period. The test cannot be carried out on a coupon
with perfect coating as the disbondment is observed under the coating at the edge of the
fault.
<br />
<br />
It is logical to deduce that if <a href="http://magnesium-anode.blogspot.com/">cathodic </a>disbondment is caused by current and that if all
current is prevented by a perfect coating, then no disbondment will take place. This is not
common sense, however, as many excavations have been dug in areas where high 'pipe-
to-soil potentials' have caused concern about cathodic disbondment. In the event, it has
proved the logic (above) and no disbondment has been found.
<br />
<br />
In one particular example voltages of over 5 volts had been recorded when the electrode
was place on the surface above the buried pipeline which was subsequently excavated, at
several spots, for examination. A coating fault was found at one location but no
disbondment. The current passing onto the metal at this coating fault, caused a drop in
the voltage of the electrode as it got nearer to the pipe. Whereas at the surface the
reading had been over 5 volts, this reduced to 0.950 volts when the electrode could be
placed close to the actual interface between the metal and the earth.
<br />
<br />
This simple drawing shows that the earth at the surface has a higher potential than the
earth close to the pipeline at the coating fault, due to the current passing from 'mass earth'
into the pipe metal.
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoOP1OsI0PhoxTBg_STdNlU222OVy1HaD04z2v4nfLtcYBGV_KjsGH7vI4YifNt39GxgxA2KiHz0eUaKdKtg6vqUMh8us-42akJkpCHgNFyZaQKG2nh6uarCbu2ogXC2tO5S8-amfmBR0/s1600/concept3.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="119" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoOP1OsI0PhoxTBg_STdNlU222OVy1HaD04z2v4nfLtcYBGV_KjsGH7vI4YifNt39GxgxA2KiHz0eUaKdKtg6vqUMh8us-42akJkpCHgNFyZaQKG2nh6uarCbu2ogXC2tO5S8-amfmBR0/s320/concept3.jpg" width="320" /></a></div>
<br />
<br />
At such site it is easy to plot the 'potential gradient' using a static electrode as a reference
and a moving electrode to trace the potential isobars. As soon as the coating fault is fully
exposed to the air, the gradient disappears completely, as the current stops. The meter
then reads 5 volts, even with the electrode placed in the ground a few mm from the metal.
<br />
<br />
by : Roger AlexanderPetrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com0tag:blogger.com,1999:blog-6964345713354057406.post-33594684060032918652015-05-18T16:36:00.000-07:002015-06-12T04:16:41.220-07:00Cathodic protection is important<center>
<h1>
An idiots guide to cathodic protection</h1>
</center>
<br />
<br />
<dir>
<br />
<br />
<center>
<h2>
What the heck IS cathodic protection in the first place???</h2>
<br />
<b><a href="http://magnesium-anode.blogspot.com/">Cathodic </a>protection is an electrical way of stopping rust.</b><br />
<b><br /></b>
</center>
Rust is chemical and electrical. Metal dissolves in some solutions and gives off electricity. Metal can be 'plated' onto other metal electrically.
<br />
All 'batteries' work on this principle and everyone knows that batteries drive loads of the things we use daily.
<br />
Not many people know that our gas and oil comes to us through pipes that are inclined to rust, but are protected by 'cathodic protection'.
<br />
Some people know that metal boats are protected by cathodic protection, and have seen lumps of metal attached to hulls for this purpose. These lumps of metal dissolve in the water and give off electricity which prevents the hull from rusting.
<br />
When you put two different metals in contact and submerge them in liquid (or wetness) one of the metals dissolves and discharges an electrical current into the liquid. The liquid (or damp material) is the 'electrolyte'
and gets 'charged up' with electricity. It's 'electrical potential' is increased.
<br />
Electricity works by 'pressure' and anything with a higher 'pressure' gives off electricity to anything with a lower 'pressure'.
<br />
The electrolyte is then at a higher electrical 'pressure' than the metal that is not dissolving and so the electricity passes into it.
<br />
The metal that is dissolving is the 'anode' from which the electrical current passes into the electrolyte and the other metal is the cathode into which the current passes because the electrical pressure must be balanced out. (everything tries to equalise).
<br />
The dissolving metal is sacrificed to prevent the subject metal from corrosion, and this method is known as '<a href="http://magnesium-anode.blogspot.com/">sacrificial </a><a href="http://magnesium-anode.blogspot.com/">cathodic </a>protection'.
<br />
There are limits to which <a href="http://magnesium-anode.blogspot.com/">sacrificial </a><a href="http://magnesium-anode.blogspot.com/">cathodic </a>protection can be used but the same principle can be used by causing a manufactured electrical pressure which is 'impressed' into the electrolyte. The electricity is then 'drained' out of the subject metal....... boat hull or pipeline.... and this interferes with the natural tendency of the metal to dissolve....or rust!
<br />
<center>
<br />
<h3>
Impressed current cathodic protection</h3>
</center>
<br />
Electricity is generated by a sort of pumping action which causes it to flow backwards and forwards in 'waves', but this is no use for our purposes so we have to get it going in one direction through a circuit known as a 'rectifier'. At the same time we can control the amount of current by transforming it, so the apparatus is know as a transformer-rectifier.
<br />
A transformer-rectifier can be regarded as an electrical pump which is sucking the electricity out of the pipeline (etc) and pumping it into the ground (or sea ... or swamp... or wherever else you want to pump it).
<br />
The effect of this is amazing. It stops rust! And it's cheap!
<br />
But there are some snags.
<br />
Because it's so good, it gets installed .... then ignored...... well most people don't even know it exists... and because it's cheap some people don't think it's important.
<br />
<br />
<br />
<center>
<b><span style="font-size: large;">But it 's life and death to some.</span></b></center>
<br />
<center>
<img border="0" src="waterc~1.jpg" /></center>
<br />
The villagers in the picture are gathering water from outside a flowstation in Nigeria.
A pipeline in Nigeria leaked petrol and local people collected the petrol in cans and washing up bowls and the site drew hundreds of women and children until the petrol was accidentally ignited.... cooking up to 1000 people.
<br />
<br />
<center>
<b>Cathodic protection IS important.</b>
</center>
A couple of years before this incident a pipeline in the USSR exploded and blew a train off it's tracks, killing many and causing ecological devastation. This was thought to be caused by corrosion.
<br />
<br />
by : Roger Alexander (my great Teacher)<br />
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<blink><b><span style="color: red;">Newsflash 5th December 2000</span></b></blink></center>
<br />
<br />
<center>
*** Natural gas spewing in Texas
MONT BELVIEU, Texas (AP) - A pipeline ruptured and released a<br />
potentially explosive cloud of natural gas, forcing evacuations of<br />
about 40 homes and the rerouting of airplane flights around the<br />
area. Several minor injuries were reported Monday night when the<br />
pipeline, owned by Channel Industries Gas Co., blew open near<br />
Houston Raceway Park. The blowout was felt and heard as far away as<br />
Baytown, more than 10 miles to the south. There was no fire, said<br />
Baytown police Sgt. Keith Dougherty. However, residents of the<br />
immediate area were told to evacuate and flights east of Houston<br />
were kept at least miles from the site as a precaution, said Texas<br />
Department of Public Safety spokesman Richard Vasser.<br />
<br />
Full article at: http://www.infobeat.com/fullArticle?article=405225991
</center>
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Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com0tag:blogger.com,1999:blog-6964345713354057406.post-89136055863777668862010-04-26T20:57:00.001-07:002015-06-12T10:45:06.973-07:00Basic Calculation For Sacrificial SystemA. Current requirement ( I ) = SA x CD<br />
<br />
Where :<br />
SA = Surface area (taken from Norton Corrosion calculation)<br />
CD = Current density (taken from NACE standard RP 0176-83)<br />
(Standard Recommended Practice Corrosion Control of Steel, fixed Offshore Platform<br />
Associated with Petroleum Production)<br />
Sea water = 55 mA.sq.m<br />
Seabed = 11 mA/sq.m<br />
<br />
B. Anode Weight = N<br />
<br />
N = (I x Con x L) : U<br />
<br />
Where,<br />
I = Current requirement (Amp)<br />
Con = Consumption rate of <a href="http://magnesium-anode.blogspot.com/">aluminium </a><a href="http://magnesium-anode.blogspot.com/">anode </a>= 3.35 Kg/AY<br />
Consumption rate of <a href="http://magnesium-anode.blogspot.com/">magnesium </a><a href="http://magnesium-anode.blogspot.com/"> anode </a>= 7.7 Kg/AY<br />
L = Life time = 10 years<br />
U = Utilization factor = 0.9<br />
<br />
C. Example<br />
<br />
Data:<br />
Atmospheric Storage Tank:<br />
- Length (L) : 5.54 m<br />
- Diameter (D) : 9.058 m<br />
- Water level Assume : 1 m<br />
Current Density (CD) : 55 mA/m2<br />
Consumption Rate of <a href="http://magnesium-anode.blogspot.com/">Aluminum </a>Anode : 3.5 kg/Amp Year<br />
Years design : 10 tahun<br />
Utility Factor : 0.9<br />
<br />
Calculation:<br />
<br />
1 Surface Area (SA)<br />
<br />
- Surface Area of Ground = pi x D2 = 3.14 x 82.047 = 257.62 m2<br />
- Surface Area of wall = pi x D x L = 3.14 x 9.058 x 5.54 = 157.56 m2<br />
Total Surface Area = <span style="font-weight: bold;">415.18 m2</span><br />
<br />
2 Current Requirement (Ip)<br />
<br />
Ip = SA x CD<br />
= 415.18 m2 x 55 mA/m2<br />
= 22,834.9 mA = <span style="font-weight: bold;">22.835 Amp</span><br />
<br />
3 Weight of Anode (W)<br />
<br />
W.Al = Ip x Y x 3.5 kg/Amp Year<br />
U = 22.835 Amp x 10 years x 3.5 kg/Amp Year : 0.9<br />
= <span style="font-weight: bold;">799.225</span> kgs<br />
<br />
4 Number of <a href="http://magnesium-anode.blogspot.com/">Aluminium </a><a href="http://magnesium-anode.blogspot.com/">Anode </a>(N)<br />
<br />
Proposed <a href="http://magnesium-anode.blogspot.com/">Aluminium </a><a href="http://magnesium-anode.blogspot.com/">Anode </a>type 50 kg - Net weight = 50 kg/ea<br />
N.Al = W.Al : 50 kg<br />
= 799.225 kgs : 50 kg<br />
= 15.985 pcs = 16 pcs<br />
<br />
Total = 16 pcs <a href="http://magnesium-anode.blogspot.com/">Aluminum </a><a href="http://magnesium-anode.blogspot.com/"> Anode </a>type 50 kg<br />
<br />
<br />
regards<br />
bajakz<br />
email : bajakz@gmail.com<br />
<br />
note : if you need more of calculation for cathodic protection, please contact mePetrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com1tag:blogger.com,1999:blog-6964345713354057406.post-28352059838674769602009-10-22T07:11:00.000-07:002009-10-22T08:34:09.955-07:00INTERNATIONAL STANDARD ISO 15589-2Foreword<br /><br />ISO 15589-2:2004(E)<br /><br /><br />ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies<br />(ISO member bodies). The work of preparing International Standards is normally carried out through ISO<br />technical committees. Each member body interested in a subject for which a technical committee has been<br />established has the right to be represented on that committee. International organizations, governmental and<br />non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the<br />International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.<br /><br />International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.<br /><br />The main task of technical committees is to prepare International Standards. Draft International Standards<br />adopted by the technical committees are circulated to the member bodies for voting. Publication as an<br />International Standard requires approval by at least 75 % of the member bodies casting a vote.<br /><br />Attention is drawn to the possibility that some of the elements of this document may be the subject of patent<br />rights. ISO shall not be held responsible for identifying any or all such patent rights.<br /><br />ISO 15589-2 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures<br />for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline transportation systems.<br /><br />ISO 15589 consists of the following parts, under the general title Petroleum and natural gas industries —<br />Cathodic protection of pipeline transportation systems:<br /><br />— Part 1: On-land pipelines<br /><br />— Part 2: Offshore pipelines<br /><br /><br />Introduction<br /><br />Pipeline cathodic protection is achieved by the supply of sufficient direct current to the external pipe surface,<br />so that the steel-to-electrolyte potential is lowered to values at which external corrosion is reduced to an<br />insignificant rate.<br /><br />Cathodic protection is normally used in combination with a suitable protective coating system to protect the<br />external surfaces of steel pipelines from corrosion.<br /><br />External corrosion control in general is covered by ISO 13623.<br /><br />Users of this part of ISO 15589 should be aware that further or differing requirements may be needed for<br />individual applications. This part of ISO 15589 is not intended to inhibit alternative equipment or engineering<br />solutions to be used for the individual application. This may be particularly applicable where there is innovative<br />or developing technology. Where an alternative is offered, any variations from this part of ISO 15589 should<br />be identified.<br /><br />Deviations from this part of ISO 15589 may be warranted in specific situations, provided it is demonstrated<br />that the objectives expressed in this part of ISO 15589 have been achieved.<br /><br />More... you can download the file<br /><br /><a href="http://www.4shared.com/file/142724789/8ca67b26/ISO15589-2-2004forOR.html" target="_blank">http://www.4shared.com/file/142724789/8ca67b26/ISO15589-2-2004forOR.html</a><br /><br />thks for all<br /><br />bajakzPetrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com0tag:blogger.com,1999:blog-6964345713354057406.post-47909745948496316902009-10-20T07:17:00.000-07:002015-06-12T04:22:15.756-07:00Examples of Design for Cathodic Protection SystemsFrom Estimated Exposed Surface Area<br />
<br />
Estimating current requirements from expected exposed surface is always subject to<br />
error. There are many factors, which affect the results.<br />
Consider:<br />
• Total surface area in contact with soil or other electrolyte.<br />
• Dielectric properties of any protective coating.<br />
• Factors which may damage a protective coating during installation.<br />
• Expected protective coating life under service conditions.<br />
• Expected percentage coverage by protective coating.<br />
• Past experience with coating applicators and construction contractors.<br />
• Current density required for cathodic protection of the metal(s) in the<br />
environment.<br />
<br />
In the end, the expected current requirement depends on calculating the area of<br />
exposed metal in contact with the electrolyte and multiplying it by the “best estimate”<br />
of current density for the conditions present.<br />
There is an alternate approach for coated electrically isolated structures (pipes, under-<br />
ground storage tanks, etc.) where there is data available on existing cathodic protection<br />
systems.<br />
<br />
The approach requires reliable local data on:<br />
• Expected leakage conductance (Siemens/unit area) in 1000 ohm cm. soil for a<br />
class of coating (epoxy, polyethylene tape, etc.) and type of service<br />
(transmission pipeline, gas distribution, fuel tank).<br />
• Soil resistivity in the service area.<br />
• Structure to soil potential shift required to produce polarization needed to meet<br />
cathodic protection criteria. This is the immediate change in potential of an<br />
isolated structure measured to a point at “remote earth” when cathodic<br />
protection is applied.<br />
<br />
The value is not a criteria for protection. However, under a given set of operating and exposure conditions, a potential shift will provide a good estimate of current needed to meet accepted criteria.<br />
<br />
The approach is best understood by using an example.<br />
<br />
Example 5.1<br />
<br />
A gas utility is planning to install 3049 meters (10,000 feet) of 5.1 cm (2 inch) coated<br />
steel distribution mains in a new development. The average soil resistivity in the area<br />
is 5,000 ohm cm. The corrosion engineer wishes to estimate the approximate current<br />
required to cathodically protect the pipes.<br />
Experience in the utility has developed the following data on cathodic protection<br />
current requirements:<br />
Average leakage conductance G for distribution type service is 2.14 × 10−3S/m2in<br />
1000 ohm cm soil.<br />
Average potential shift measured to “remote earth” to achieve protection is −0.250<br />
volt.<br />
Calculations:<br />
<br />
Total surface area of the proposed pipe.<br />
As=πd L = (5.1 × 3.1416/100) × 3049 = 488 sq. meters<br />
<br />
Estimated leakage conductance of new pipe in 1000 ohm cm soil.<br />
g = G × A = 2.14 × 10−3×488 = 1.04 Siemens<br />
Since resistance = 1/conductance<br />
Resistance to remote earth = 1/1.04 = 0.96 ohm<br />
<br />
Estimated resistance to remote earth in 5000 ohm cm soil. (Resistance is directly pro-<br />
portional to resistivity).<br />
0.96 × 5 = 4.8 ohms<br />
Estimated current to shift pipe potential to remote earth −0.250 volt. From Ohm’s<br />
Law (I = E/R)<br />
0.250/4.8 = 0.052 A.<br />
<br />
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bajakzPetrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com2tag:blogger.com,1999:blog-6964345713354057406.post-5427878478145253592009-07-15T19:30:00.000-07:002015-05-21T13:49:59.956-07:00CATHODIC PROTECTION BASIC PRINCIPLES<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">The presence of anodes and cathodes in a structure can be caused by micro or macro influences.<br /> On the micro scale, they may be due to:</span><br />
<table border="1" cellpadding="0" cellspacing="0" style="color: #cccccc;"> <tbody>
<tr> <td><div align="left">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Heterogenieties in alloy structure.</span></div>
</td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Oxide layer.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Difference in stress level.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Micro segregation, etc</span></td> </tr>
</tbody></table>
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">On the macro scale, anodes and cathodes may be caused by:</span><br />
<table border="1" cellpadding="0" cellspacing="0" style="color: #cccccc;"> <tbody>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Variation in oxygen availability.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Water composition.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Soil resistivity.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Bi-metallic couples.</span></td> </tr>
<tr> <td><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;">Presence or otherwise of protective coatings, etc.</span></td> </tr>
</tbody></table>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Corrosion results from an electrochemical reaction. It requires an anode, a cathode, a common electrolyte, and an electrical connection between the two zones. The corrosion process results in the flow of a small electric current from the anode to the cathode through the electrolyte. The magnitude of the current which is due to a number of factors is directly proportional to the metal lost due to corrosion. One ampere flowing for one year would result in the loss of 9 kg of steel from a corroding surface. </span></div>
<div align="center">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;"><br /> <img src="http://fransasia-s.com/images/corr.jpg" height="216" width="354" /> </span> </div>
<div align="center">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;"><em>Freely flowing corrosion current from Anode to Cathode.</em></span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">In recent years cathodic protection has found a general acceptance amongst engineers and structure owners as being a truly effective method of preventing corrosion under the ground or under the sea. It is now more common than not to find cathodic protection used on marine structures and on buried pipelines.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">The concept of cathodic protection is straight forward. Corrosion occurs as the result of electrochemical reactions between zones of differing potential on a metal surface. Oxidation (corrosion) occurs at the anodic zone and reduction (no corrosion) occurs on the cathodic zone. Cathodic protection is achieved when an entire metal surface is converted to a cathodic zone.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">The corrosion reactions at each surface may be described as:</span></div>
<div align="center">
<img src="http://fransasia-s.com/images/duagb.jpg" height="189" width="500" /></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Cathodic protection is achieved by supplying a current from an external source so that it reverses the natural corrosion currents and ensures that current is flowing through the electrolyte onto all of the metal surface requiring protection. This current flow causes a change in potential.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Freely corroding mild steel in seawater has a resultant potential between anode and cathode of approximately -0.50 to -0.60 volts compared to a silver/silver chloride reference electrode. When cathodic protection is applied, it will be noted that the surface potential of steel will change to more negative than -0.80 volts when measured relative to a silver/silver chloride reference cell. Thus by using this simple practical measurement, it is possible to determine whether corrosion has been completely eliminated or not.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">The external current applied in cathodic protection may be generated from either of two methods, sacrificial anodes or impressed current systems.</span></div>
<div align="justify">
</div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;"><strong><span style="font-size: 85%;">GALVANIC ANODES</span></strong><br /> Sacrificial or galvanic anodes rely on the galvanic corrosion of a more reactive metal to produce current, e.g. aluminium anodes, zinc anodes or magnesium anodes.</span></div>
<div align="center">
<img src="http://fransasia-s.com/images/sacrif.jpg" height="250" width="358" /></div>
<div align="center">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;"><em>Flow of corrosion current suppressed by protective current discharged from sacrificial anode.</em></span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Sacrificial anodes are most commonly used to protect metallic structures in electrolytes because of their simplicity of installation and maintenance free operation. Of the alloys available for sacrificial anodes, alloys of aluminium have proven to be the most economical in seawater or very low resistivity muds.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Knowing the total submerged and buried steel areas, the water resistivity and the required system life, a corrosion engineer can determine precisely what energy will be required to protect a structure and can design a galvanic system to suit the environmental requirements.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 85%;"><strong><br /> IMPRESSED CURRENT ANODES</strong></span><span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;"><br /> Impressed current systems provide the same electric current as galvanic anodes by the discharge of D.C. current from a relative inert anode energised from an external D.C. power source such as a transformer rectifier or thermo electric generator. Impressed current system anodes include materials such as graphite, silicon iron, platinised precious metals and lead alloys.</span></div>
<div align="center">
<img src="http://fransasia-s.com/images/dcpower.jpg" height="250" width="355" /></div>
<div align="center">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;"><em>Flow of corrosion current suppressed by protective current discharged from Impressed Current </em></span><span style="font-size: 78%;"><em><span style="font-family: Verdana,Arial,Helvetica,sans-serif;">System</span></em></span>.</div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Effective cathodic protection guarantees corrosion free existence. Providing the structure is maintained at a potential of -0.8 volts (or more negative) no loss of metal will occur at all during the life of the structure. As cathodic protection can be renewed or added to during the life of the structure, the maintenance of the desired potential is readily achievable. The efficacy of the system can be monitored by simple electrical measurements.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Cathodic protection apart from overcoming the more "normal" causes of corrosion, may be used to counter accelerated corrosion resulting from contact between different metals, from impingement by high velocity water, from the effects of sulphate reducing bacteria and from the effects of stray D.C. currents.</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">In fact, any metal such as scrap iron may be used as an impressed current anode. In cathodic protection practice, we choose to use either semi-permanent or permanent anode and very seldom non-permanent anode (such as scrap iron).</span></div>
<div align="justify">
<span style="font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 78%;">Examples of semi-permanent anodes are silicon/chromium/iron anode, lead/silver/antimony anode, graphite anode etc.<br /> Examples of permanent anodes are mixed metal oxide anode, platinised titanium anode etc.</span></div>
Petrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com2tag:blogger.com,1999:blog-6964345713354057406.post-87135845673705142912009-07-13T19:23:00.000-07:002015-06-12T10:45:50.429-07:00Consideration for Design of Galvanic Anode Cathodic Protection System<span style="font-size: 180%;"><span style="font-size: 100%;"><span style="font-style: italic;"><span style="font-weight: bold;">by</span> Ernest Klechka, P.E, NACE International CP Instructor</span></span></span><span style="font-size: 180%; font-weight: bold;"><span style="font-size: 100%;"><br /></span>N</span>ormally cathodic protection (CP) can be applied by a sacrificial anode or impressed current system. CP can be applied by galvanic or sacrificial system when limited amounts of current are needed, soil resistivity is low (normally less than 5,000 ohm-cm), and electric power is limited or not available. Sacrificial anode system have the added advantage of requiring minimum maintenance.<br />
To design a sacrificial anode system, the following information is needed:<br />
1. Current requirement (I <span style="font-size: 78%;"><span style="font-style: italic;">current required</span></span>)<br />
2. Anode resistance ( R<span style="font-size: 78%;"><span style="font-style: italic;"> anode</span></span>), calculated or based on the manufacturer's data<br />
3. Design life<br />
<br />
<span style="font-weight: bold;">Design Current Requirements</span><br />
CP current requirements can be determined by calculation based on bare or exposed surface area, assumptions about existing coatings, the coating damage factor, and the current density (CD) required for CO in environment are needed.<br />
<br />
To calculate the current required, the total surface area (A<span style="font-size: 78%;"><span style="font-style: italic;">total</span></span>) in sq m of the structure is defined. Base on experience, the coating damage factor (f<span style="font-size: 78%;"><span style="font-style: italic;">damage</span></span>) or percent bare area is determined. The total surface area to be protected by CP (A<span style="font-size: 78%;"><span style="font-style: italic;">cp</span></span>) in sqm is then :<br />
A<span style="font-size: 78%;"><span style="font-style: italic;">CP</span></span> = A<span style="font-size: 78%;"><span style="font-style: italic;">total</span></span> f<span style="font-size: 78%;"><span style="font-style: italic;">damage</span></span><br />
<br />
Based on the environment to which the structure is exposed, the applicable CD for CP (I<span style="font-size: 78%;"><span style="font-style: italic;">cd</span></span>) is estimated in mA/sqm. Using the ACP and Icd, the calculated current required (Icurrent required) is then :<br />
I<span style="font-size: 78%;"><span style="font-style: italic;">current required</span></span> = A<span style="font-size: 78%;"><span style="font-style: italic;">CP</span></span> I<span style="font-size: 78%;"><span style="font-style: italic;">cd</span></span><br />
<br />
<span style="font-weight: bold;">Current Requirements Based on Field Tests</span><br />
<br />
Current requirement test are the most reliable way to estimate the current requirements for existing structure and take info account the condition of the coatings and variations in soil resistivity. If the structure is coated and isolated, it is possible to directly determine the current requirements.<br />
<br />
A temporary anode (groundbed) is established and a portable power supply (usually a battery, generator, or portable rectifier) is installed. A current is applied (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a>I) and the change in polarized potential (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a> V) is determined. The ratio of the current applied dicided by the change in polarized potential (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a>I/<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a>V) is used to calculated the current requirement.<br />
<br />
For example, if 5A are applied to the structure and a polarized potential shift of 50 mA occur, and a 100 mV shift is needed for CP, then :<br />
<br />
I<span style="font-size: 78%;"><span style="font-style: italic;">current required</span></span> = shift needed x (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a>I/<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s1600-h/delta.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358141314953805138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigX4uQDjeD0WULl_1AvzEovAJMMJkPT8ZlS0mZQYA0TRNZoGWfjSf1vHu3KfAllXUV6VaG_dmr9esFAUZagZ-XMxz3-Auip-t6CTpAS0TdBGElYsMAHTzcC5v6ZaaDU4NA3d6S0QkIATs/s320/delta.png" style="cursor: pointer; height: 12px; width: 12px;" /></a>V)<br />
= 100 mV x (5A / 50mV)<br />
= 10 A<br />
<br />
Determining the Output of a Sacrificial Anode<br />
<br />
Often the manufacture of an anode will provide the estimated current output in the form of table or graphs based on the shape and size of their anode and soil resistivity. The average soil (electrolyte) resistivity is needed to use these table or graphs or for calculation.<br />
<br />
if this data is not available, the output of an anode can be estimated based on Ohm's Law :<br />
I <span style="font-size: 78%;"><span style="font-style: italic;">anode</span></span> = E <span style="font-size: 78%;"><span style="font-style: italic;">driving potential</span></span> / R <span style="font-size: 78%;"><span style="font-style: italic;">anode</span> </span><br />
<span style="font-weight: bold;">Anode Resistance-to-Earth</span><br />
<br />
Typically, since sacrificial anodes are buried vertically. For a single certical anode, such as a package magnesium anode, the resistance-to-earth can be calculated using Dwight's equation for a single vertical rod or pipe :<br />
R = (0.00159 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s1600-h/rho.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143467376242018" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s320/rho.png" style="cursor: pointer; height: 11px; width: 8px;" /></a>/<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNqWX63DZT6ZSQdNtrvzSDlKPsE_RN2SpYdmRkbXjYrNCB5tZKtj1uf_qaTZwzm4K3snpFsCpCJeydGQgVJ8q9wZD6bIzeobErsUdCFRCavjmL7bNba4vzMQv2CTA3LOL1WsddT43k-iQ/s1600-h/phi.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143262778240578" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNqWX63DZT6ZSQdNtrvzSDlKPsE_RN2SpYdmRkbXjYrNCB5tZKtj1uf_qaTZwzm4K3snpFsCpCJeydGQgVJ8q9wZD6bIzeobErsUdCFRCavjmL7bNba4vzMQv2CTA3LOL1WsddT43k-iQ/s320/phi.png" style="cursor: pointer; height: 8px; width: 9px;" /></a> L) [ln (8L/d)-1]<br />
where :<br />
R = groundbed resistance (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a>)<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s1600-h/rho.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143467376242018" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s320/rho.png" style="cursor: pointer; height: 11px; width: 8px;" /></a> = resistivity (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a> -m)<br />
d = diameter of anode (m)<br />
<br />
The resistivity value used must be representative of the volume resistivity affecting the anode.<br />
<br />
<span style="font-weight: bold;">Parallel Anode</span><br />
<br />
Sunde's equation can be used to estimate the resistance of distributted parallel anodes:<br />
<br />
R<span style="font-size: 78%;">N</span> = (0.00159 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s1600-h/rho.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143467376242018" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s320/rho.png" style="cursor: pointer; height: 11px; width: 8px;" /></a>/<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNqWX63DZT6ZSQdNtrvzSDlKPsE_RN2SpYdmRkbXjYrNCB5tZKtj1uf_qaTZwzm4K3snpFsCpCJeydGQgVJ8q9wZD6bIzeobErsUdCFRCavjmL7bNba4vzMQv2CTA3LOL1WsddT43k-iQ/s1600-h/phi.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143262778240578" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNqWX63DZT6ZSQdNtrvzSDlKPsE_RN2SpYdmRkbXjYrNCB5tZKtj1uf_qaTZwzm4K3snpFsCpCJeydGQgVJ8q9wZD6bIzeobErsUdCFRCavjmL7bNba4vzMQv2CTA3LOL1WsddT43k-iQ/s320/phi.png" style="cursor: pointer; height: 8px; width: 9px;" /></a> L) [ln (8L/d)-1] - 1 + (2L/S) ln(0.656 N)<br />
where :<br />
R<span style="font-size: 78%;">N</span> = groundbed resistance (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a>)<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s1600-h/rho.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143467376242018" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiasDcvA9p6yYOvkVLMtMyjDrdw_gGa4h-e_ArXYPyRSgeNaCMzbI9JNK-zFl-sZrYepgiAlFe6OQslpms-uPGEjEqhScA04wLD7mDiLAJ3rsLJDJ3RvqpCatIz0IPgFdRp_C1NVFHSjSQ/s320/rho.png" style="cursor: pointer; height: 11px; width: 8px;" /></a> = resistivity (<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a> -m)<br />
d = diameter of anode (m)<br />
L = length of anode (m)<br />
S = spacing of anode in the groundbed (m)<br />
<br />
If the anode are separate by 6 m or more, the parallel effect of anode is negligible.<br />
<br />
<span style="font-weight: bold;">Anode Current Output</span><br />
<br />
For a single highh-[ptential (-1.75 Vcse) 7.7 kg (17 lb) magnesium anode, the current output can be calculated or determined based on the manufacturer's data.<br />
<br />
A typical 7.7 kg anode is 1,295 mm long by roughly 51 mm square. Because Dwight's equation deals with rods, an equivalent rod with the same circumference as a 51mm square is needed; the rod will be 65 mm in diameter. The equivalent diameter d for square with sides S is given as :<br />
<br />
3.14 d = 4 S<br />
d = 4 S /3.14<br />
<br />
If the structure is to be polarized to -0.850 V<span style="font-size: 78%;">cse</span>, driving potential is then:<br />
<br />
E<span style="font-size: 78%;">net</span> = -1.75 -(-0.85) = -0.90 V<br />
<br />
Anode resistance can be calculated using Dwight's equation for 5,000 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a>-cm soil :<br />
<br />
R<span style="font-size: 78%;">anode</span> = (0.00159 * 5,000 / 3.14*1,295) [ln (8*1,295/65-1]<br />
= 25 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a><br />
<br />
Assuming the structure and cable resistance are negligible, the expected current is then :<br />
<br />
I<span style="font-size: 78%;">anode</span> = Enet / Ranode<br />
= 0.90 V / 25<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"> <img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a><br />
= 0.036 A (36mA)<br />
<br />
The anticipated current output is then 36mA from single 7.7 kg anode.<br />
Anode supplier literature indicated that in 5,000 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a>-cm soil, a high-potential magnesium anode will have an anticipated output of 0.040 A (40 mA) to a structure polarized to -0.85Vcse. The data infers that the structure has negligible resistance to earth and, therefore, no <span style="font-weight: bold;">IR</span> drop. The resistance to remote earth of single high-potential (-1.75 V<span style="font-size: 78%;">cse</span>) magnesium anode can be calculated:<br />
<br />
R<span style="font-size: 78%;">anode</span> = E<span style="font-size: 78%;">net</span> / I<span style="font-size: 78%;">anode</span><br />
=(1.75 - 0.85) / 0.04<br />
= 22.5 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s1600-h/ohm.png" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358143630153326690" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvDLwZUieUvfIoqUeyT8o1CkiVJ2y3uCxfW-VveTOJOnMg0BR43HfTMHg9htgYFK8rDe97B3JVIjYbHnX1YN2Y9kjjR8Q2HYcNc0-8uhPa5riImVcdyfZm2ITg5sZVKJ0sZ_5aACiW3GI/s320/ohm.png" style="cursor: pointer; height: 12px; width: 11px;" /></a><br />
<br />
The two value of current output and resistance are very similar.<br />
<br />
Number of Anode Needed Bases on Current Requirements<br />
<br />
Once the total current required and the current output from a single anode are determined, the number of anode needed to protect the structure can be calculated. Based on current requirement :<br />
<br />
N<span style="font-size: 78%;">anode </span>= I<span style="font-size: 78%;">current required</span> / I<span style="font-size: 78%;">anode</span><br />
<br />
After the number of anode is calculated, the number of anode must be rounded up ti the next integer (no partial anode allowed).<br />
<br />
Number of Anode Needed Based on Design Life<br />
<br />
The number of anode needed can also be calculated based on the current requires an the design life. Total weight need for design life can be based on Faraday's Law :<br />
<br />
Wtotal =K I T<br />
<br />
where:<br />
K = Consumption (kg/A-h x 24 h/day x 365 days) ( see the table I )<br />
I = current in A (I<span style="font-size: 78%;">current required</span>)<br />
T = time in years (design life)<br />
Then the number of anode needed is equal to the total weight needed divided by weight of single anode:<br />
<br />
N<span style="font-size: 78%;">anode </span>= W <span style="font-size: 78%;">total</span> / W <span style="font-size: 78%;">anode</span><br />
<br />
Table I<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjshjUxBXG4wTfDgVFV-H2J21qUK9r4SPhzD-ZPU-zThOWm7l1nYvooj_PhMcqWaHnt8L3Q1JEUQWjTNtl-bVPcK_kJF9tcBdq0SBS0yBatc9mv3fYL7k_CinZkcTxIuk895013DTfjFts/s1600-h/tabel+1.JPG" onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5358309929395024450" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjshjUxBXG4wTfDgVFV-H2J21qUK9r4SPhzD-ZPU-zThOWm7l1nYvooj_PhMcqWaHnt8L3Q1JEUQWjTNtl-bVPcK_kJF9tcBdq0SBS0yBatc9mv3fYL7k_CinZkcTxIuk895013DTfjFts/s320/tabel+1.JPG" style="cursor: pointer; display: block; height: 110px; margin: 0px auto 10px; text-align: center; width: 320px;" /></a><br />
<br />
<span style="font-weight: bold;">How Many Anode Are Really Needed?</span><br />
<br />
The number of anode needed, therefore, is the larger of the number needed based on current requirements and the number needed based on design life.<br />
<br />
Because the current provided can be greater than the current required, control resistor may be needed to reduce the initial output of anodes. After a period of time, the current required may change due to changes in the condition of coating or the environment. Control resistor may needed to be changed with time.<br />
<br />
Galvanic Anode Life<br />
<br />
Once the number of anode needed is determined, the life expectancy for the system should be checked. The following equations can be used to determine the anticipated life of the sacrificial anode system.<br />
<br />
Magnesium years of life = 0.256 x anode weght in kg x efficiency x utilization factor Current in A<br />
Zinc years of life = 0.0935 x anode weght in kg x efficiency x utilization factor Current in A<br />
<br />
<span style="font-weight: bold;">Post-Installation Measurements</span><br />
<br />
After the systems installed, the structur-to-soil potentials sould be measured as we;; as the current output from the anode system. IF the current output needed adjustment, more anodes can be added to increase current or control resisters can be added to reduce the current output.<br />
<br />
Anode life can be calculated based on the actual measured current of the sacrificial anode system.<br />
<br />
<span style="font-weight: bold;">Conclusions</span><br />
<br />
The design of a sacrificial anode CP system can be accomplished as long as the current demand and the anode current output can be determined. Anode separated by more tham 6 m can be assumed to have minimum parallel interference.<br />
<br />
Sacrificial of galvanic anode CP can be very effective as long as current demands are low and soil resistivities are moderate to low. Added benefits of these system are the reduce maintenance cost, no electrical power is required, and ease of installation. Low-power sacrificialsytem also cause a minimum of interference and can be used to discharge CP interferencePetrushttp://www.blogger.com/profile/04241961009160625127noreply@blogger.com0