Oil storage tanks cathodic protection

A storage tank is a large container composed of a tank wall, a tank top, a tank bottom and accessories to store crude oil or other liquids. The cathodic protection of the storage tank includes internal cathodic protection and external cathodic protection. Generally, sacrificial anodes can be used inside the storage tank. For cathodic protection, impressed current cathodic protection can also be used for the inside of storage tanks that require a long protection life. For the bottom of the storage tank, because it is inconvenient to replace the sacrificial anode and requires a long service life, impressed current cathodic protection is generally used. ,

Cathodic protection of storage tanks, it is very necessary to carry out cathodic protection construction on the bottom of the storage tank: the bottom of the storage tank is generally on tar sand. As time goes by, the tar sand will gradually age, and the foundation cushion will also crack In this way, the underground water will reach the bottom of the oil tank through the cracks; on the other hand, the quality of the oil tank is also affected with the height of the internal liquid, and it will deform after a long time. If the two factors are produced at the same time, the service life of the oil storage tank will be greatly shortened, and even dangerous. Therefore, more and more businesses attach great importance to the cathodic protection of oil storage tanks.

Some basic rules for cathodic protection must be observed: if there is an anti-corrosion layer on the outer surface of the bottom of the storage tank, the set cathodic protection current density must be controlled between 5 mA per square meter and 10 mA per square meter; if When the quality of the anti-corrosion layer on the bottom of the oil storage tank is poor or not, the current density of the cathodic protection should be controlled between 10 mA and 20 mA per square meter.

The cathodic protection system and the test device must be carried out at the same time. Therefore, the test requirements of the oil storage tank should also be carried out at the same time: the long-acting reference electrode should be buried under the bottom of the oil tank, and the reference electrode required at the center of the bottom plate should be long-acting Reference electrode made of copper sulfate or high-purity zinc; the test cable should be of good quality, high strength, and sufficient length; when measuring the protection point of the storage tank bottom plate, a plastic pipe with holes can be installed under the bottom plate.

Partial cathodic protection

1. Concrete slab foundation and covered with sand or asphalt;

2. Concrete ring foundation, the ring is filled with gravel, sand, with or without asphalt cover;

3. The base of the assessment is paved with gravel, gravel and sand, with or without asphalt cover.

Only by conducting a power feeding test on a container filled with liquid can the cathodic protection protection current requirement be accurately estimated. Here, the amount of current flowing to other grounding devices through the connection piece should be included in the calculation. Especially for large-diameter storage tanks, when the tank is empty, the bottom of the tank will bulge upwards and no longer fully contact the ground. In this case, the data obtained from the power feeding test will be low.