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Close Interval Survey (CIS)

We survey the potential step by step along the entire pipeline route to obtain the complete cathodic protection profile. With that profile we locate sections with under- or over-protection, interference, contacts with other structures and isolation faults, among other findings.

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Technician in full PPE walks the pipeline route with the electrodes and the data logger on his chest.

What it is

The Close Interval Survey (CIS), also called CIPS, is an ON/OFF potential survey at short intervals, carried out by walking along the pipeline route. Between one test station and the next there are hundreds of meters without data. The CIS fills them in and shows the continuous protection profile.

When it is needed

  • To assess cathodic protection along the entire pipeline, not only at the test stations.
  • As indirect inspection within an External Corrosion Direct Assessment (ECDA).
  • After finding points that do not meet the criterion in a potential survey.
  • To locate direct current interference from other structures.

How we do it

Pipeline Rectifier GPS-synchronized interrupter Test station Trailing wire Cu/CuSO4 electrodes Fails criterion − −850 mV OFF ON Author: Pampa Eco (pampaeco.com.ar). License: CC BY 4.0 – https://creativecommons.org/licenses/by/4.0/deed.en pampaeco.com.ar Pipeline Rectifier GPS-synchronized interrupter Test station Trailing wire Cu/CuSO4 electrodes Fails criterion − −850 mV OFF ON Author: Pampa Eco (pampaeco.com.ar). License: CC BY 4.0 – https://creativecommons.org/licenses/by/4.0/deed.en pampaeco.com.ar
Criterion: −850 mV OFF with respect to Cu/CuSO4.
Diagram by Pampa Eco. You may use it with attribution (CC BY 4.0).

  1. We install GPS-synchronized interrupters on the rectifiers, anodes or current injection points that influence the section.

  2. We locate the pipeline route with a pipe locator.

  3. We connect to the pipe at a test station with the trailing wire and walk the route with Cu/CuSO4 electrodes. We record ON and OFF step by step.

  4. We georeference each reading with sub-meter GPS.

  5. We process the data, build the profile and mark the sections that do not meet the criterion.

When the scope requires it, we run it together with the Direct Current Voltage Gradient (DCVG) in a single pass.

Equipment

  • CIS data logger
  • Cu/CuSO4 reference electrodes
  • Trailing wire reel
  • GPS-synchronized current interrupters
  • Pipe locator
  • Sub-meter GPS

Deliverables

  • ON and OFF potential profile by chainage, with the criterion line.
  • List of sections that do not meet the criterion, with chainage and coordinates.
  • Georeferenced KMZ file.
  • Final report in PDF.
  • Instrument calibration certificates and personnel certifications.

Standards

NACE SP0207 – NACE SP0169 – NACE TM0497 – ISO 15589-1

Where we apply it

Pipelines – Industrial plants – Service stations and fuel depots

Related services

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