Anti-corrosion practices for buried steel pipes

Pipe rust removal → Apply primer → Top coat → Second coat of top coat → Wrap glass silk cloth → Top coat → Top coat;

Inner wall construction process: pipe rust removal → primer application → top coat → second top coat → third top coat

1. Pipe rust removal
Before applying primer, the surface of the steel pipe should be cleaned of grease, ash, rust, and oxide scale. The quality standard of sandblasting rust removal reaches Sa2.5 level.
2. Apply primer after de-rusting the surface of the steel pipe. The time interval should not exceed 8 hours. When applying primer, the base surface should be dry. The primer should be applied evenly and fully without any clumping or bubbling. The primer should not be applied within the range of 150 to 250mm at both ends of the pipe.
3. After the primer is dry, apply the topcoat and wrap the glass fiber cloth. The time interval between primer and topcoat should not exceed 24 hours.
4. The epoxy coal tar pitch coating is a two-component, room-temperature curing coating; the glass fiber cloth is dry, dewaxed, untwisted, edge-sealed, medium alkali, and has a warp and weft density of 10*12 threads/cm~12*12 threads/ cm glass fiber cloth. Immediately after the topcoat is applied, wrap the glass silk cloth. The width of the edge of the glass cloth is 30 to 40 mm. The overlap length of the joints is not less than 100 mm. The overlap joints of each layer are staggered. The oil penetration rate of glass fiber cloth is more than 95%, and there should be no gap larger than 50mm*50mm. Leave 150~250mm ladder-shaped stubble at the end of the pipe.
5. The construction of pipeline interfaces should be carried out after the welding pressure test is passed. The old and new anti-corrosion edges should be no less than 50mm, the overlap length of the joints should be no less than 100mm, and the joints should be firmly and tightly bonded.
6. Steel pipe outer wall coating mechanism: one bottom and two sides, one cloth and two sides, the total dry film thickness is 400µm.
7. Steel pipe inner wall coating mechanism: one bottom and three sides, the total dry film thickness is 300µm.
8. After the external anti-corrosion construction of the steel pipe is completed, quality inspection shall be carried out according to the design requirements or the corresponding requirements in Table 4.3.11 in the “Construction and Acceptance Specifications for Water Supply and Drainage Pipeline Projects”.