Specialist Surveys

Each survey technique has its particular attributes, in general Pearson and signal attenuation coating surveys directly examine the external coating, whereas close interval potential surveys investigate cathodic protection levels and thereby provide an indirect report of coating condition. The dc voltage gradient survey is a hybrid approach, as the technique can locate coating defects and is then able to evaluate whether cathodic protection is achieved at that coating defect.

Close Interval Potential Survey (CIPS)

Close Interval Potential Surveys (CIPS) are carried out to provide a profile of the potential level throughout the length of a metallic structure. The profile can include both ‘On’ and instantaneous ‘Off’ potentials to assess the Cathodic Protection performance. This survey procedure can also be used to identify areas affected by interaction.

DC Voltage Gradient (DCVG) Survey

Using a pulsed dc current on the pipeline, the survey investigates voltage gradients associated with external coating defects, using two earth contact probes and a sensitive centre-zero voltmeter. Severity of defects can be assessed and effectiveness of cathodic protection at the defect determined.

Pearson Coating Survey

A survey technique to detect external coating defects, which employs an ac signal injected onto the pipeline and compares the potential gradient between two mobile earth contacts. At coating defects, increases in voltage gradient occur which are noted and recorded as the survey progresses.

Signal Attenuation Coating (SAC) Survey

An ac signal is applied to the pipeline and this signal will gradually decrease as it leaks to earth through the capacitive and resistive effects of the coating. At coating defects the signal loss will be greater and the survey equipment is used to measure this intensity at selected pipeline locations to determine coating condition.