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Requirements for Directly Buried Pipelines with Nonmetallic Compensators
Release time:
Jan 12,2021
The materials and structure of non-metallic expansion joints must meet requirements for high-temperature resistance, corrosion resistance, flame retardancy, and sealing. The bellows are a critical component of non-metallic expansion joints, capable of reducing vibration and absorbing thermal displacement in pipelines. Selection should be based on operating conditions, such as the working medium, external environment, and operating temperature.
The materials and structure of non-metallic expansion joints shall meet the requirements of high-temperature resistance, corrosion resistance, flame retardancy, and sealing. The bellows are a key component of non-metallic expansion joints, capable of reducing vibration and absorbing thermal displacement in pipelines. It should be selected based on working conditions, such as the working medium, external environment, and operating temperature.
Non-metallic expansion joints should be stored in a clean, dry environment free of corrosive gases, with relative humidity not exceeding. 90%, while also avoiding direct sunlight. It is not suitable for multi-layer stacking; take care to prevent mechanical damage to the bellows caused by stacking, collisions, and drops. When a non-metallic compensator equipped with a flow guide cylinder is installed vertically, the open end of the flow guide cylinder should face downward.
The shelf life of non-metallic expansion joints should not exceed. For non-metallic expansion joints that have been stored and subsequently put into service after two years, it must be confirmed that the metal and banding materials of the expansion joint show no obvious deformation, corrosion, or aging.
To prevent the pipeline from moving up, down, left, or right after being heated or cooled, non-metallic expansion joints should be equipped with fixed supports to ensure that the overall position of the pipeline remains unchanged. On the other hand, the stresses generated after pipeline heating and cooling far exceed the allowable stresses of steel pipes, joints, and other fittings. To prevent pipeline expansion and contraction, no fixed supports or structures can provide sufficient protection. Only by selecting appropriate non-metallic expansion joints to relieve pressure can the safe operation of the piping system be ensured.
Requirements for Directly Buried Pipelines with Nonmetallic Compensators :
1. When non-metallic compensator insulated pipes are buried underground, the surrounding area should be filled with sand having a particle size of less than 20 mm, and then covered with original soil. The thickness of the sand fill should not be less than 200 mm.
2. The burial depth of the top of the thermal insulation pipe typically does not exceed 1.2 meters, but should also be no less than 0.7 meters. Non-metallic compensator thermal insulation pipes can be directly buried beneath various types of pipelines.
3. The directly buried compensator device does not require cold tightening, nor does it need to be installed by first connecting the entire pipeline with steel pipes and then cutting it to the same length as the non-metallic compensator before welding. With the use of a directly buried non-metallic compensator, there is no need to install guiding supports.
4. During installation, please ensure that the direction of the flow guide sleeve is consistent with the flow direction.
5. The medium in non-metallic expansion joints shall be treated to remove free oxygen and chloride ions, and the chloride ion content must not exceed 25 ppm.
6. Non-metallic expansion joints are permitted to undergo hydrostatic testing at system pressures not exceeding 1.5 times the nominal pressure.
7. After the compensator is installed, secure both ends of the pipeline before conducting the system hydrostatic test to prevent internal pressure thrust from stretching the compensator.
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