Operation and maintenance of cathodic protection system(1)

1.Preparation and acceptance of cathodic protection before putting into operation

Before cathodic protection is put into operation, the pipeline to be protected shall be inspected. If there is no insulation, there is no protection. Before applying cathodic protection current, it is necessary to ensure that all insulation measures of the pipeline are correct. There should be no leakage points on the surface of the pipeline, and the protected pipeline should have continuous conductivity.

2. Daily maintenance and management of Cathodic Protection Station

Check the electrical equipment circuit connection firmness, the correctness of installation, electrical components whether there are mechanical obstacles. Check whether the fuse of the fuse on the distribution board is properly connected according to the regulations. Observe the electrical instrument, record the output current and electrified potential value on the special form, and check whether there is any change compared with the previous record. Regularly check the working grounding and arrester grounding, and ensure that the grounding resistance is not greater than 10 ohm. Do a good job in cleaning and sanitation of the equipment in the station, pay attention to keep the indoor dry, well electrified, do a good job of ventilation, and prevent the instrument from overheating.

3. Maintenance of sacrificial anode

   1. The daily maintenance work of pipeline sacrificial anode protection is not much. In addition to the protection potential measurement, test pile maintenance, insulation joint detection, grounding fault removal and other work according to the requirements of impressed current cathodic protection, it is recommended to measure the parameters every year. According to this, the pipeline protection situation is analyzed. If the performance of the prototype deteriorates, corresponding measures should be taken.

   2. During the annual inspection, the output current of sacrificial anode can be measured to repair the broken cable.

   3. If the output current of anode decreases obviously and the anode does not reach its life, the short circuit of anode cable is the common reason. The ammeter can be connected in series in the anode cable to measure the anode output current, or a resistance of 0.1 Ω can be connected in series in the anode cable. The anode current output can be calculated by measuring the voltage drop on the resistance.

   4. The grounding resistance of anode is anode open circuit potential minus anode closed circuit potential divided by anode output current.

4. Analysis of common faults in cathodic protection system

   1. The harm of poor pipeline insulation and leakage fault
After the cathodic protection station is put into operation or the sacrificial anode protection is put into operation for a period of time, the phenomenon that the output current of the sacrificial anode group increases while the pipeline protection distance is shortened under the specified power on point; or in the sacrificial anode system, the output current of the sacrificial anode group increases, and its value has exceeded the protection current demand of the pipeline, but the protection point still fails to reach the specified index . It is called imprint to protect pipeline leakage.

   2. Causes of electric leakage
Improper construction, insulation joint failure or leakage, metal sleeve crossing, pipeline and grounding grid short circuit.

   3. How to judge the short circuit between pipeline and grounding grid

To judge whether there is a short circuit between the grounding electrode and the pipeline, the method of potential measurement can be used. The reference electrode is used to measure the potential of pipeline and grounding electrode respectively. The potential of short circuit grounding electrode and pipeline is the same. Or measure the potential difference between the grounding electrode and the pipeline. If the potential between the two is zero, it can be judged that there is a short circuit between the grounding grid and the pipeline.

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