CALCULATION CATHODIC PROTECTION SYSTEM FOR PIPELINE

CALCULATION CATHODIC PROTECTION SYSTEM FOR PIPELINE

Under Ground Surface Pipe Area

The surface pipeline to be protected, as follows:
  • Length pipeline (L): 4.875 km
  • Pipeline Diameter (d) :   12 inch = 323.85 mm = 0.32385 m
Total surface to be protected (A) = π * d * L
A =  4957.33 m2

Demand of Current

Total demand current to given formula:

Where :
= Demand Current (Amp)
= Surface area to be protected (m2)
= Current density per m2 (mA)
= Coating breakdown factor
Therefore:
mA = 0.992 Amp

  1. Resistance of Magnesium Anode for Kp 4+500





Rmg : Magnesium anode resistance (Ohm)
Lmg : Length of prepacked magnesium anode 32lbs (m) 0,9 m
Dmg : Diameter of prepacked magnesium anode 32lbs (m) 0,195 m
ρ : Layer Soil resistivity data at depth from survey  (Ohm cm) 5500 ohm.cm
Rmg = 25.3739 ohm

  1. Driving Voltage Anode
Net Driving Voltage The net driving voltage between Magnesium anode of -1.6  V
(Cu/CuSO4 reference) is 0.75 V (1.6 - 0.85).
 Close circuit potential (Volt) of magnesium is -1.6 volt

  1. Current of anode For Kp 4+500


Ia : Magnesium anode current output (Amp) = (Ec - Ea) : Rmg
Ipf : Required current
Ec : Protective potential (Volt) -0,85 Volt
Ea : Close circuit potential (Volt) -1,6 Volt
I = -0.85 – (-1.6) : 25.3739
I = 0.0296 A


  1. Sacrificial anode requirement

  1. Mass Metode
Total Sacrificial Anode weight to be given formula:
Where:
Y = Design Live Period (year)
S = Consumption rate (kg/amp-year)
= demand current (Amp)
f  = Utility factor
So, total weight;
kg
N = 13.68 14 Pcs
  1. Current Output Method for Kp 4+500
Ip = Current Protective
Ia = Current Anode
N = 2.6 3 Pcs

  1. Lifetime of anode

Current capacity = mass anode : Consumtion rate
Current capacity = 14.5 kg : 8 kg/amp.year = 1.8125 A.Y
Life of anode = Current Capacity (A.Y) x N  x f    :     IR
Life of anode = 1.8125 A.Y x 14  x 0.8 : 0.992 A
Life of anode = 20.46 Years > 20 Years

  1. Total Anode Required
The total Anode required is 40 Pcs, weight is 32 lbs or 14.5kg for each. Uses Current Method for better distribution.