4. Search for leakage point of anticorrosive coating

The method of using DCVG to find the damaged point of anticorrosive coating of pipeline and determine the leakage point or short contact point of pipeline. This method first sends the pulse signal to the pipeline to be tested. If the pipeline coating is good, the current flowing into the pipeline is very weak, and the instrument does not display it. If the anticorrosive coating of the pipeline is damaged, the current will leak into the pipeline through the damaged place from the soil, and the current flow will produce obvious potential gradient in the surrounding soil. When the detector holds two reference electrodes to detect and walk directly above the pipeline, the voltmeter will vibrate. When the pointer of the voltmeter stops shaking, the middle of the two reference electrodes is the leakage point of the anticorrosive coating.

   5. Near distance potential measurement along the pipeline
It is usually used to check the working condition of cathodic protection system by measuring the point position on the test pile. In this way, even if there is a leakage point in the pipeline coating, if the leakage point is far away from the test pile, it is difficult to detect it through the potential measurement of the test pile. Therefore, the closer the potential measurement is, the more tender the measurement result will be, which will reflect the actual situation of cathodic protection of pipelines. In order to eliminate the IR drop, a short circuit is installed in the cathodic protection circuit, and all the power supplies connected to the detected pipeline should be turned on and off at the same time, so as to measure the on-off potential of the bag pipe.

   6. Aging test of pipeline anti-corrosion coating
Electromagnetic method can reflect the general condition of anticorrosive coating, buried depth of pipeline and defect location of coating. Its principle is to input a voltage signal to the pipeline, and the detector detects the attenuation degree of the signal along the pipeline. When there is a sudden attenuation of the coating on the pipeline, it shows that the signal attenuation is smooth.

   7. The safety of maintenance type in cathodic protection system
On the way to the construction site, you should pay attention to safety, whether by bus, by boat or by plane. When surveying in the field, pay attention to the attack of poisonous snakes and beasts. When working on the rectifier, disconnecting the switch on the panel does not mean that it is safe to operate inside the equipment. AC power should be disconnected and safety locks and labels should be installed. Before contacting the rectifier, check whether the shell is charged with electric pen.