2、 When the ball valve is closed, part of the medium remains in the valve body and also bears a certain pressure. Before overhauling the ball valve, close the shut-off valve in front of the ball valve, open the ball valve to be overhauled, and completely release the pressure inside the valve body. If it is an electric or pneumatic ball valve, the power and air supply should be disconnected first.

Difference between square compensator and commonly used rotary compensator
Square compensator, also known as natural compensator, is the earliest compensation method in China. Generally, steel pipes are welded or pressed into "Π type", and the displacement of pipes is compensated by the bending of steel pipes.
Bellows compensator is welded and assembled from stainless steel bellows, receiver and flange. It only needs expansion and contraction of bellows to absorb the deformation of compensation pipeline. In recent years, corrugated compensator has completely replaced square compensator.
The maintenance free thrust free rotary compensator is used for the displacement compensation installation of heat supply network pipes, which is mainly composed of inner and outer pipes, sealing packing and spring compression installation. The utility model is characterized in that the fit clearance between the spring compression flange and the inner pipe is small with a high-precision processing wrist. The utility model is applicable to the combination of two to three absorption compensators for the axial displacement and axial thrust of the heat supply network pipes. The product has good sealing performance, no need to stop production and maintenance. Moreover, the product adopts fine processing, which makes the coordination between product parts more reasonable, the assembly more accurate, and ensures the product concentricity. Only when the product accepts angular and lateral displacement can it be greatly improved, and the stability is good, and the safety and sealing of the product are improved.
The rotary compensator is a new type of compensator for thermal pipe thermal contraction compensation. The structure of rotary compensator is mainly composed of integral seal seat, seal gland, reducer, antifriction centering bearing, seal data, rotating cylinder and other components. The device needs more than two pairs on the thermal pipeline to form a relative rotating absorption pipeline thermal displacement, so as to reduce the stress of the pipeline.