What is the principle of pipeline inspection technology？

Pipelines are the main way to transport a large amount of energy such as oil and gas, they are widely used in the chemical industry. Like all engineering equipment, pipelines can also malfunction. Defects may occur in various stages of pipeline manufacturing, laying, and operation, timely pipeline inspection defects can reduce pipeline maintenance costs.

1. CIPS：

The CIPS is used to detect the effective level of cathodic protection in buried steel lines.

This technology uses the CIPS close-interval potential detection system to measure the pipe-ground potential at small intervals along the pipeline, so that the protection potential at any point on the pipeline can be measured, and then the protection potential distribution map on the entire pipeline can be obtained, and the cathodic protection effect of the pipeline can be analyzed .

The CIPS method collects data along the pipeline with an interval of 1-1.5m, and draws a continuous on/off pipe ground potential curve to reflect the cathodic protection potential of the entire pipeline. When there is a defect in the anti-corrosion layer, the current density there increases, so that The protection potential shifts in the positive direction. When this shift reaches a certain amount, it can be detected on the surface. When VOFF is lower than -850mV (copper/copper sulfate reference electrode), the pipeline will corrode.

2. Potential gradient method:

The potential gradient method is divided into direct current potential gradient (DCVG) and alternating current potential gradient (ACVG) according to different signals.

a. DCVG:

This technology uses the DCVG DC voltage gradient detection system to measure the cathodic protection DC voltage gradient along the pipeline, and then obtain the voltage gradient distribution map on the entire pipeline to find the damage point of the anti-corrosion layer.

A direct current signal is applied to the pipeline, and then a pair of reference electrodes 10 m apart is used to test the potential gradient along the pipeline. The data must be measured along the entire pipeline.

When the corrosion layer of the pipe has a breakpoint point , the signal current flows out of that point , forming an electric field centered on the breakpoint in the soil around the pipe , and there is a significant difference in the potential difference between the poles ( a steep slope of the DC potential gradient curve ) , inferring the location of the breakage point , and the size of the coating defect is calculated according to the percentage of the potential drop .

b. ACVG:

The AC ground potential gradient method (ACVG) can use PCM and AC geopotential difference meter (A cross), by measuring the changes in the AC ground potential gradient in the soil, to find and locate the pipeline corrosion resistance layer breakage point.

If you want to learn more about pipeline inspection, you can contact us: info@granfoo-cn.com.