Aboveground Surveys

Summary

All CP systems require routing monitoring to make sure that the systems are running efficiently and effectively to prevent corrosion and subsequent metal loss from occurring, which could be very costly or cause environmental damage or be harmful to human life.

With thousands of miles of pipeline inspected and decades of experience in different countries, Vecor counts on a variety of equipment of latest technology to offers a wide range of aboveground surveys to evaluate any kind of CP system or pipeline network.

Why Vecor?

With thousands of miles of pipeline inspected and decades of experience in different countries, Vecor counts on a wide variety of equipment of latest technology to offers a wide range of aboveground surveys to evaluate any kind of CP system or pipeline network with our qualified team of engineers and technician always ready to attend any requirement at anytime and anywhere.

Vecor has set its Operator Qualification program in Veriforce, Avetta and ISNetworld to satisfy any formal pre-requisite set by DOT or internal standards. Contact us to find out more about our services!

Among the techniques employed by the industry to determine the functionality of CP systems, Vecor can offer support in:

• Annual Compliance Surveys
• Monitoring Test Stations
• Close Interval Surveys (CIS)
• Direct Current Voltage Gradient (DCVG)
• Alternating Current Voltage Gradient (ACVG)
• Pipeline Current Mapping
• Soil Resistivity Surveys
• Corrosion Coupons

Annual Compliance Surveys 

These are routine measurements and checks carried out at regular intervals defined by legal requirements or internal standards to determine if protection criteria is being fulfilled and to determine any deficiencies with the CP system.

Monitoring Test Stations (Test Points)

 Pipelines generally have monitoring facilities installed along the pipeline route to check that CP is being supplied to all parts of the pipeline.

Typically, pipe-to-soil potentials, current and possible interference are monitored at test stations which are usually installed above the pipelines at a distance no between 1 to 3 miles apart.

Vecor’s certified technicians follow guidelines outlined in NACE TM0487 to carry out the required measurements.

Close Interval Potential Surveys

Close Interval Surveys (CIS) belongs to the group of methods accepted and approved by Department of Transport (DOT) for assessing the effectiveness of cathodic protection (CP) systems used on buried pipelines. Basically, the potential (voltage) difference between buried pipes and their surrounding soil is measured. The measures allow detecting defect on the coating. Normally the method is combined with other techniques due to its limitations for detecting small holidays or because it results ineffective under some conditions such as: frozen ground, disbonded coating casing pipes and when pipes are located in rocky terrain, or under a paved road.

Vecor offers the following CIS service:

• “On/off” CIS used to evaluate the performance of the CP system against system performance criteria.
• “Depolarized” CIS used to evaluate CP system effectiveness by measuring polarization decay after the cathodic protection current has been switched off long enough for the pipe-to-soil potential to stabilize.
• “On” CIS used when CP current sources cannot be interrupted.

 Direct Current Voltage Gradient Surveys

DCVG Surveys are used to determine the location of a coating defect or holiday and to classified its relative severity once it is found. During the survey a direct current signal is applied to the pipeline to measure the voltage gradient between the soil and the pipe. The voltage gradient becomes larger and more concentrated toward the defect. From the data analysis, it is possible calculated the %IR and classified the defect magnitude. 

Alternating Current Voltage Gradient ACVG Surveys

ACVG Survey is used to evaluate the coatings on buried pipelines. The technique is similar to DCVG but in this case, the voltage gradient at the location of a coating defect is achieved by applying an alternate current signal.

Pipeline Current Mapping Surveys

Current Attenuation Survey, frequently refers as PCM Survey, is a useful technique to locating the line position and determining the overall coating condition of the pipeline. The technique is based on the use of electromagnetic detection devices. It relates current change along the length of the pipeline to the coating defect. The survey involves the use of a transmitter to simulate the frequency DC signal and a receiver. The receiver is responsible of the measurements and calculations. The advantage of this technique is that allows determining whether CP current is being lost along the pipeline. When an area is a high consumer of CP current, it can cause a lack of current in the system that leaves other pipeline zones unprotected.