In recent years, the excellent performance of three-layer PE anti-corrosion coating makes it the first choice for new oil and gas pipeline projects in China. However, there are many factors during the production, construction and operation of the three-layer PE anti-corrosion coating, which is easy to be damaged. The damaged points of anticorrosive coating found by external inspection technology need to be repaired in time to avoid further corrosion of oil and gas pipelines. Due to the different types of anticorrosive coating, the repair construction technology is also different.

The repair technology of viscoelastic anti-corrosion tape and winding polypropylene tape is mainly divided into three steps: surface treatment, coating defect repair and repair acceptance.

1. Remove the soil on the exposed pipe section to make the anticorrosive coating defects fully exposed. Measure and record the size and position of the defects, and take photos of the defects.

2. Repair the anticorrosive coating at the defect, remove the damaged coating, and expose the corroded pipe body completely.

3. The surface of exposed pipe body shall be treated and the corrosion products shall be cleaned up. The surface treatment grade shall reach st2.5.

4. All rust spots, scales, dirt and other impurities as well as loose coating on the surface of anticorrosive coating to be repaired within 10 mm around the defect must be removed; after that, the defect part shall be ground into rough surface, and the dust shall be removed with dry cloth and brush. Attention must be paid to the following when working on the surface of the pipe body where the anticorrosive coating is defective:

1. Before the construction of viscoelastic anti-corrosion tape, the mending area should be dry;

2. The viscoelastic anti-corrosion adhesive tape shall be applied in sequence, and the air shall be removed by rolling at the same time. The overlapping width of viscoelastic anti-corrosion tape shall be greater than or equal to LCM. During the construction, the connection line can be lapped along the inner side of the tape; the overlapping length of the beginning and end of the viscoelastic anti-corrosion tape shall be more than or equal to 100 mm;

3. After the construction of viscoelastic anti-corrosion tape, the appearance and leakage point shall be detected immediately;

4. After the viscoelastic anti-corrosion tape layer is qualified, polypropylene reinforced fiber tape is used to wrap around the outer layer of viscoelastic anti-corrosion tape.

5. The specific construction method of polypropylene reinforced fiber tape is as follows: from one end, the viscoelastic tape with a width of about 3 mm shall not be wound around the outer belt, and then spiral winding shall be carried out. When winding the outer belt, a certain tension shall be maintained, and the lap width of the tape shall be 50% - 55% until the other end, and finally the end part shall be wound in situ for one week. Appearance inspection shall be carried out on the repaired part of anticorrosive coating to ensure its surface is smooth. 100% electric spark leakage detection shall be adopted for the repair part. The leakage detection voltage is 15kV, and it is qualified if there is no leakage point, wrinkle, bubble and other phenomena. If it is unqualified, it shall be repaired again.

Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services. Tel: 0539 3712117, 15588026668.