A Different Approach to High Resolution CP Evaluation

Assessing the effectiveness of Cathodic Protection (CP) in multiple pipeline corridors can be challenging. Close interval potential (CIS or CIPS) above ground CP surveys rely on interruption of all current sources that affect a particular pipeline and can be especially problematic in multi-pipe corridors involving several operators. Multi-pipe corridors can be very congested and complicated with numerous pipeline crossings and bonds. These circumstances can lead to difficulties in locating and ensuring the above ground survey is being conducted over the pipeline of interest. Inappropriate decisions surrounding the actual integrity of a particular pipeline have been made based on conventional pipe to soil surveys. The use of inline cathodic protection current measurement tools can eliminate a number of errors associated with above ground potential assessment techniques in multiple pipeline corridors and provide more accurate integrity data. CP ILI inspections can conclusively identify undocumented electrical connections to other structures on pipelines in such congested corridors. Active, unbeknownst bonds/connections will cause significant errors in CIS/CIPS data if not properly addressed during data acquisition. Additionally, information collected through the CIS technique is generalized since it is the average gradient being measured from all influencing adjacent lines. Information from an inline cathodic protection current measurement tool is specific to only the pipeline being inspected and therefore eliminates this uncertainty. This paper outlines an alternative approach to above ground close interval survey for assessing CP performance using inline inspection technology.