1、 Precautions before construction
1. The burial depth shall be in accordance with the gas construction regulations. If the burial depth exceeds the construction regulations, protective pipes must be used.
2. After excavation, first remove the stones, crushed stones and other sundries, and then pave and press them with sand about 10cm thick.
3. The piping of pneumatic ball valve and connection joint shall be kept horizontal and vertical before construction.
4. The distance between burial and other buried objects shall be kept: ① For buried objects above 60 ℃ such as regional heating, the distance between THP and other protective measures shall be kept above 30cm. ② Water supply pipe, electrical facilities, communication cable: more than 30cm. ③ Sewer pipe: more than 20cm.

Fixed support thrust calculation:
The degree thrust of the main fixed support is composed of the combined force of three forces:
(1) Internal pressure thrust caused by working pressure F ＝ P * A:
Where P is the working pressure and A is the effective sectional area of the bellows. The internal pressure thrust is determined by the effective sectional area and working pressure of the bellows. The internal pressure thrust is proportional to the working pressure and effective sectional area. Generally speaking, the internal pressure thrust of the bellows compensator is large.
(2) Elastic force generated by bellows rigidity PA ＝ K * f * L
Wherein, K refers to the rigidity of bellows, L refers to the practical elongation of pipeline, f refers to the coefficient, which is 0.5 when pretensioning, otherwise, it is 1.
(3) Sliding friction reaction force q between fixed supports μ l
Where q is the weight of the pipe, μ Is the friction coefficient, and l is the spacing between the free end and the fixed end of the pipe.
Degree thrust of main fixed support=internal pressure thrust+friction reaction+elastic force
If it is not concentric, the bending moment and lateral thrust of the fixed support due to eccentricity will also be included. The main fixed support has a great thrust, and the large pipe diameter can reach hundreds of tons. The civil engineering layout is difficult, and comprehensive structural accounting needs to be stopped. It is a heavy load support.
The secondary fixed support bears the same force as the main fixed support, but the internal pressure thrust is balanced and offset, and the total thrust is small. It is not of the same order of magnitude as the main fixed support, but belongs to the intermediate load shedding support.
When calculating the fixed point thrust, the force on each side of the fixed point shall be calculated separately and then combined. When both sides of the fixed point have the same direction, the vector sum of the two forces is used as the fixed point thrust. When the two forces are in opposite directions, use the force with large absolute value minus 0.7 times of the force with small absolute value as the thrust of the fixed point.
The guide support is used to control the movement along the pipeline or the movement direction of the compensator, so as to ensure that the contraction of the pipe section acts on the compensator and that the pipeline will not be unstable
The manufacturer's samples of ordinary compensators not only elaborate on the product specifications, structures and parameters, but also have application examples for thrust calculation and general device requirements, which are more generous and can be used as design basis