(1) Inner wall of valve body. Check the pressure and corrosion resistance.

(2) valve seat. Due to the penetration of medium, the inner surface of the thread used to fix the valve seat is easy to be corroded, which makes the valve seat loose. Attention shall be paid during the inspection. For high-pressure occasions, check whether the sealing surface of valve seat is damaged.

(3) spool. It is necessary to carefully check whether all parts of the valve core are corroded and worn, especially when the valve core is worn more seriously under the condition of high pressure difference. In addition, check whether the valve stem has similar phenomenon, or the connection with the valve core is loose.

(4) Diaphragm, O-ring and other gasket. Check whether it is aged and cracked.

(5) Sealing packing. Check whether Teflon packing and sealing grease are aged and dry, and whether the mating surface is damaged.