Close Interval Survey: Assessing the effectiveness of cathodic protection systems
A close interval survey (CIS) is a measurement tool used to ensure pipeline cathodic protection systems are operating to NACE SP0169 specified standards. Close interval surveys may also be referred to as close interval potential surveys (CIPS). They are often part of a structured External Corrosion Direct Assessment (ECDA) process.
Close interval surveys are conducted on buried or submerged pipelines. At regular intervals, measurements are taken of the potential (voltage) difference between the pipeline and a reference electrode in contact with the material or soil (electrolyte). The data collected during a close interval survey provides insight into the cathodic protection on your pipeline.
MATCOR can assist with all of your CIS requirements.
Why Perform Close Interval Surveys?
There are two primary reasons to conduct close interval surveys:
- Regulations – State or federal regulations require operators to assess the effectiveness of cathodic protection systems on certain protected assets such as gas pipelines.
- Risk assessment – CIS is also a tool utilized to determine risks where CP assessment may not be required by law. In this case the cost of the cathodic protection system is seen as a benefit when compared to the cost of a potential catastrophic failure.
Data from Close Interval Surveys can be used to:
- Establish a baseline for assessing the performance and operation of underground pipeline CP systems
- Pinpoint areas of low pipeline potentials requiring adjustment to the CP system or remediation
- Test for interference at bonds and casing vents, or where foreign lines or overhead power lines exist
Close Interval Survey Methods
There are various types of close interval surveys that measure the difference between the pipeline and the ground surface at regular intervals:
- Native potential and depolarized surveys establish a baseline for determining the level of cathodic protection for a structure
- On potential and interrupted potential surveys can be used to determine if corrosion is taking place and the level of corrosion
Qualified MATCOR technical personnel can conduct close interval surveys in the field for oil, gas and water pipelines. Data is then analyzed by NACE certified experts.
