Description

At the request of IRPC Public Company Limited, CGL Engineering Co. Ltd carried out a survey of the cathodic protection system and checked five (3”, 4”, 12”, 18” and 20”) insulation flanges (IF) along the 40” water main (WM) pipeline between water tank and IP in July 2018. The WM pipeline and the branchs lines in Cooling Tower area (Zone A) are currently supplied with cathodic protection (CP) current by 30V/ 80A impressed current cathodic protection (ICCP) system. As this single ICCP system is not sufficient to protect the entire WM pipeline and branch lines, a temporary 30V/ 22A ICCP system was set up to provide CP current for the WM pipeline and the branch lines outside the cooling tower area (Zone B). Despite supplying the CP current with two ICCP systems, the pipelines stayed more electropositive than the internationally accepted protection criteria (-850 mVCSE) but, these pipelines do satisfy the minimum 100 mV decay of polarisation criteria to confirm CP protection. Out of the five flanges checked, the 4” and 12” are not CP insulated as the steel insulation gasket allows the CP current to flow through. This report details the findings and recommendations of the work performed by CGL Engineering to ascertain the present condition and suggest the improvements to be made in the ICCP system for the Water pipelines.