CIPS Survey (Close Interval Potential Survey)

The CIPS (Close Interval Potential Survey) is one of the most widely used techniques for evaluating the effectiveness of cathodic protection systems on buried pipelines.

The method provides detailed measurements of the pipe-to-soil potential at closely spaced intervals along the pipeline route, allowing variations in cathodic protection performance to be identified with much greater resolution than measurements taken only at conventional test stations.

Italcorr performs CIPS surveys on gas pipelines, oil pipelines, water pipelines and industrial pipeline systems to assess cathodic protection effectiveness, identify under-protected areas and support pipeline integrity management programs.

Objectives of a CIPS Survey

The main purpose of a CIPS survey is to obtain a continuous profile of cathodic protection potentials along a buried pipeline.

The survey can be used to:

evaluate cathodic protection effectiveness;
identify under-protected pipeline sections;
identify areas of excessive polarization;
detect significant potential variations;
evaluate protective current distribution;
identify possible electrical interference;
investigate abnormal cathodic protection conditions;
support maintenance and system optimization;
provide data for pipeline integrity assessment;
compare cathodic protection performance over time.

Unlike measurements performed only at fixed test stations, CIPS provides detailed information between test points and can reveal localized areas that might otherwise remain undetected.

Principle of the CIPS Method

During a CIPS survey, the pipe-to-soil potential is measured at closely spaced intervals while an operator moves along the pipeline route.

A reference electrode is placed in contact with the soil above or near the pipeline, while the measurement system is electrically connected to the pipeline through a test station or other suitable connection point.

Measurements are normally recorded together with their position along the route.

This produces a detailed potential profile that can be analyzed to determine how cathodic protection performance varies along the pipeline.

ON Potential Measurements

The ON potential is measured while the cathodic protection system is operating normally.

ON measurements provide useful information about the overall electrical conditions of the pipeline, but they may include voltage drop components caused by protective current flowing through the soil.

These voltage drops are commonly referred to as IR drop.

For this reason, ON potentials alone may not always provide sufficient information to determine the actual polarization condition of the pipeline.

Instant OFF Potential Measurements

Where technically possible, CIPS surveys can include synchronized interruption of the cathodic protection current.

The instant OFF potential is measured immediately after the protective current is interrupted.

This technique significantly reduces the influence of IR drop and allows a more representative assessment of pipeline polarization.

For pipelines protected by several cathodic protection stations, synchronized interrupters may be installed on the relevant current sources to ensure simultaneous switching.

The resulting ON/OFF potential profile provides detailed information about cathodic protection performance along the pipeline.

Synchronized Current Interruption

Accurate OFF potential measurements require proper synchronization of the cathodic protection current sources affecting the pipeline.

Depending on the network configuration, interrupters may be installed on:

transformer-rectifier units;
drainage systems;
other cathodic protection current sources.

Synchronization allows the measuring equipment to record potentials during defined ON and OFF cycles.

Before the survey, the influence of neighbouring cathodic protection systems and other current sources should also be considered.

CIPS Field Equipment

A typical CIPS survey may use:

high-input-impedance data logger;
portable reference electrodes;
synchronized current interrupters;
pipeline connection cable;
trailing wire;
GPS/GNSS positioning equipment;
pipeline locator;
field data acquisition software.

The exact equipment configuration depends on pipeline characteristics, accessibility, survey objectives and project requirements.

Reference Electrodes

The reference electrode is a critical component of a CIPS survey because all potential measurements are made relative to a stable electrochemical reference.

Depending on the environment and applicable requirements, suitable reference electrodes are selected for field measurements.

During the survey, attention is given to:

electrode condition;
electrical contact with the soil;
soil moisture;
electrode stability;
contamination;
positioning relative to the pipeline.

Poor electrode contact or an unstable reference electrode can significantly affect measurement quality.

Pipeline Route Localization

Accurate localization of the pipeline is important before and during the CIPS survey.

The pipeline route can be identified using electromagnetic locating equipment and existing pipeline documentation.

Route localization allows the operator to maintain the correct survey path and position the reference electrode appropriately relative to the pipeline.

GPS/GNSS coordinates can be recorded together with potential measurements to provide accurate geographical referencing of the survey results.

Measurement Interval

One of the principal advantages of CIPS is the short distance between consecutive measurements.

Measurements are taken at close intervals along the pipeline rather than only at permanent test stations.

The appropriate interval depends on:

project specifications;
pipeline accessibility;
terrain conditions;
required survey resolution;
applicable procedures and standards.

Closer measurement spacing provides a more detailed representation of potential variations along the pipeline.

Field Survey Activities

A typical CIPS field survey may include:

review of pipeline documentation;
identification of cathodic protection stations;
pipeline route localization;
verification of electrical connections;
installation of synchronized interrupters where required;
verification of reference electrodes;
acquisition of ON and/or instant OFF potentials;
continuous recording along the pipeline route;
GPS/GNSS positioning;
identification of test stations and relevant pipeline features;
recording of abnormal conditions;
verification of collected data.

Field observations are important because terrain, electrical installations and local environmental conditions can help explain anomalies identified during data analysis.

Data Processing and Analysis

After field acquisition, CIPS data are processed to generate a continuous potential profile along the surveyed pipeline.

Analysis may include:

ON potential profile;
instant OFF potential profile;
comparison between ON and OFF values;
identification of potential shifts;
identification of under-protected areas;
identification of unusually negative potentials;
comparison with cathodic protection criteria;
correlation with test stations;
comparison with previous surveys;
correlation with coating survey results.

Potential data can also be correlated with GPS coordinates to produce geographically referenced results.

Identification of Under-Protected Areas

One of the primary applications of CIPS is the identification of pipeline sections where cathodic protection may be insufficient.

Possible causes include:

inadequate protective current;
deterioration of the coating;
excessive distance from a cathodic protection station;
poor current distribution;
defective electrical connections;
insulating joint problems;
shielding conditions;
interference from neighbouring structures;
stray currents.

CIPS identifies the affected sections, while additional diagnostic methods can be used to investigate the cause.

Identification of Excessive Polarization

CIPS can also identify areas where pipeline potentials are significantly more negative than required.

Excessive cathodic protection may be undesirable for certain coating systems or materials and can indicate inefficient current distribution.

Identifying these areas allows the cathodic protection system to be optimized rather than simply increasing the total current output.

Detection of Electrical Interference

Potential variations recorded during CIPS may indicate the influence of external electrical sources.

Possible sources include:

neighbouring cathodic protection systems;
DC traction systems;
electrified railways;
industrial electrical installations;
grounding systems;
high-voltage power transmission infrastructure.

Where interference is suspected, additional measurements can be performed to determine its origin and significance.

CIPS and Coating Condition

CIPS primarily evaluates cathodic protection potentials and does not directly locate every coating defect.

However, coating deterioration can significantly influence current demand and potential distribution.

For this reason, CIPS is particularly effective when combined with coating assessment techniques such as DCVG, Pearson Survey and PCM.

Correlation of the different datasets helps distinguish between cathodic protection problems and coating-related anomalies.

CIPS + DCVG Survey

The combination of CIPS and DCVG (Direct Current Voltage Gradient) is widely used for detailed assessment of buried pipelines.

CIPS provides information about the level of cathodic protection, while DCVG helps locate and assess coating defects.

Together, the methods can help identify areas where:

coating defects are present;
protection potentials are insufficient;
current demand is elevated;
further investigation or excavation may be justified.

This approach allows maintenance activities to be prioritized according to actual field conditions.

CIPS + PCM Survey

PCM (Pipeline Current Mapping) provides additional information about the distribution and attenuation of current along a pipeline.

Combining PCM with CIPS can help identify relationships between:

potential changes;
current losses;
coating deterioration;
electrical connections;
interference;
areas of increased current demand.

The integration of both datasets improves understanding of cathodic protection system behaviour.

CIPS + Pearson Survey

The Pearson Survey can be used to identify coating discontinuities along buried pipelines.

When Pearson results are correlated with CIPS measurements, coating anomalies can be compared with changes in cathodic protection potential.

This helps determine whether detected coating defects are associated with areas of reduced protection.

Integration with Non-Contact Magnetometric Inspection

For pipeline integrity programs, CIPS results can also be integrated with non-contact magnetometric inspection and other diagnostic techniques.

While CIPS evaluates cathodic protection performance, magnetometric methods can provide additional information about areas potentially affected by stress, corrosion or structural anomalies.

Combining different inspection methods can improve the prioritization of areas requiring detailed investigation.

CIPS for Existing Cathodic Protection Systems

CIPS can be used not only for periodic pipeline inspection but also for optimization of existing cathodic protection systems.

Survey results can support decisions regarding:

adjustment of rectifier output;
installation of additional anodes;
modification of anode groundbeds;
repair of electrical connections;
coating rehabilitation;
installation of additional test stations;
mitigation of electrical interference.

This makes CIPS an important tool for both corrosion monitoring and cathodic protection maintenance.

Repeat CIPS Surveys and Trend Analysis

Repeating CIPS surveys over time allows changes in pipeline protection conditions to be evaluated.

Comparison with previous surveys may reveal:

gradual coating deterioration;
changes in current demand;
deterioration of cathodic protection equipment;
new interference conditions;
changes in potential distribution.

Trend analysis can therefore support preventive maintenance and long-term pipeline integrity management.

CIPS Survey Reporting

Following completion of the survey, the technical report may include:

description of the pipeline and cathodic protection system;
survey methodology;
equipment used;
measurement conditions;
ON potential data;
instant OFF potential data;
GPS/GNSS coordinates;
potential profiles;
identification of anomalous sections;
interpretation of results;
comparison with applicable criteria;
correlation with other inspection data;
recommendations for additional investigation or corrective actions.

The results can also be presented in tables, graphs and geographically referenced formats.

Applications

Italcorr performs CIPS surveys on:

gas pipelines;
oil pipelines;
water pipelines;
firewater pipelines;
industrial pipelines;
long-distance transmission pipelines;
buried metallic pipeline networks.

The method can be applied to both existing cathodic protection systems and systems undergoing commissioning or performance optimization.

Benefits of CIPS Survey

CIPS provides several important advantages:

detailed assessment along the entire surveyed route;
closely spaced potential measurements;
identification of localized under-protection;
evaluation of cathodic protection current distribution;
detection of abnormal potential variations;
support for cathodic protection optimization;
integration with coating defect surveys;
reduction of unnecessary excavation;
support for preventive maintenance;
historical comparison of pipeline condition;
improved Asset Integrity Management.

Integrated Pipeline Integrity Assessment

For a more comprehensive evaluation of buried pipelines, Italcorr can integrate CIPS with:

DCVG Survey
For locating and assessing coating defects.

PCM Survey
For evaluating current attenuation and identifying areas of increased current loss.

Pearson Survey
For detecting coating discontinuities.

Stray Current Investigation
For identifying external DC interference and its effect on pipeline potentials.

AC Interference Assessment
For pipelines affected by nearby high-voltage power systems.

Non-Contact Magnetometric Inspection
For additional assessment of pipeline integrity and identification of potentially critical areas.

The correlation of multiple diagnostic techniques provides a more complete understanding of the condition of the pipeline and its cathodic protection system.

Italcorr CIPS Survey Services

Italcorr provides CIPS surveys as part of comprehensive cathodic protection, corrosion monitoring and pipeline integrity services.

Our approach combines field measurements, accurate positioning, technical analysis and correlation with other diagnostic methods to identify areas requiring further investigation, maintenance or optimization.

CIPS data can be used to support cathodic protection system evaluation, maintenance planning, coating rehabilitation programs and long-term pipeline integrity management.