If the above inspection is normal, the shock absorber shall be further disassembled to check whether the fit clearance between the piston and the cylinder barrel is too large, whether the cylinder barrel is strained, whether the valve seal is good, whether the valve disc and the valve seat fit tightly, and whether the stretching ball valve of the shock absorber is too soft or broken. In addition, the method of grinding or replacing parts shall be adopted as the case may be, The keel pneumatic butterfly valve will make noise in actual use, which is mainly caused by the collision between the keel pneumatic butterfly valve and the steel plate ball valve, the frame or the shaft, the damage or falling of the rubber pad, the deformation of the dust cylinder of the keel pneumatic butterfly valve, insufficient oil and other reasons. Find out the cause and repair it