Stabilizing, Welding and Anticorrosion
of seamless steel pipes
Stabilizing the pipe is to stabilize the pipe on the foundation or foundation according to the design mark and horizontal position. The pipe should be placed in the center of the pipe trench, and its allowable deviation should not be greater than 100mm. The pipe should be placed firmly in the pipe trench, and there should be no suspension under the pipe to prevent the pipe from bearing additional stress.
If there is a position error in the welding work pit dug in advance, it should be re-excavated according to the actual needs. When excavating soil, do not damage the anti-corrosion layer of the pipeline. The soil and debris in the pipe should be removed before the pipe is connected to the mouth. When butt welding is carried out in the trench, the gap between the butt joints and the amount of misalignment should meet the requirements, and the pipeline should be kept in a straight line. Before welding, the dirt and rust on both sides of the weld should be removed.
After the pipeline is welded, a comprehensive inspection must be carried out with an electric spark leak detector before backfilling, and repairs should be made to the electric spark breakdown. Town gas pipes shall comply with the relevant standards. The repairs that do not meet the requirements will be checked again until they are qualified.
After the pipeline group is welded, it is necessary to carry out non-destructive inspection of the weld seam, and conduct strength and tightness tests on the pipeline. After passing the test, the welded joint should be covered with anti-corrosion. After the electric spark inspection is passed, all the soil can be backfilled. Usually, after the pipe is welded, a welding pit is reserved, and the pipe body is partially filled with soil to cover the pipe body, so as to prevent stones and other hard objects from falling on the pipe and damage the anti-corrosion layer, and at the same time, it can reduce the pipeline caused by temperature changes. The thermal expansion and contraction of the anti-corrosion layer cause damage to the anti-corrosion layer due to friction with the soil.
Horizontal and vertical clearances between underground gas pipelines and buildings, structures or adjacent pipelines and cables. If it is difficult to arrange due to terrain restrictions and cannot be solved, the clear distance can be appropriately reduced after effective protection measures are taken after consultation with relevant departments.
When the gas pipeline encounters obstacles, the following measures are often taken:
(1) When the actual situation is less than the specified clear distance, according to the local conditions, the gas pipeline is bypassed horizontally or vertically, and 4 elbows are added.
(2) Increase the casing, and lay the gas pipeline in the casing.
(3) Increase the trench, and lay the gas pipe in the brick pipe trench.
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