Abstract

GIS Helps Evaluate Cathodic Protection System for Gas Distribution Pipelines
Track: Pipeline and Gas Utilities
Authors: Dr. Syed Ali Naqi, Nadia Akhter, Irfan Zafar

Damage to steel pipelines can arise not only from physical activities, but also from underground corrosion. To prevent corrosion, steel pipelines are protected with coating and cathodic protection (CP) system. SSGC has 2,367,893 consumers, connected through 39,253 Km of distribution pipeline network which comprise of 84.5% of steel material laid in year 1955 to 2011. Impressed current cathodic protection system is used for high/medium pressure supply-mains while sacrificial anode system for low pressure distribution-mains.

To evaluate the current CP status of gas distribution network in Karachi, spatial analysis techniques were performed on 1784 CP test points' values and existing GIS. Based on CP potential values (in volts), Karachi was classified into three categories/zones; protected area (-0.85volts-or-higher), partially protected area (-0.7 to -0.84volts) and unprotected area (-0.69volts-or-lower). Year-wise length of steel pipeline in each category was also estimated for replacement of affected steel pipelines with PE, CP system Expansion/upgrade and budgeting.