Reason:
1. Poor operation, the closure member stuck on dead center or more, damage to fracture junction.
2. Pieces of connection is not firmly closed, slack off.
3. Choose the material of the connection piece is wrong, can not afford the media of corrosion and mechanical wear.
Maintenance method:
1. Correct operation, close the valve can not be too hard, open the valve can not exceed the top dead center of the valve fully open, the hand wheel should be reversed a little.
2. The closure of the valve stem connection should be firm, the threaded connection should check back.
3. The closure of the valve stem connection with the fastener should withstand the corrosive media, and have a certain mechanical strength and wear resistance.
