1. Valve stem failure
Knife gate valve valve stem failure is usually caused by the damage of the valve stem thread and the twisting of the valve stem due to excessive operation, or the fit tolerance of the valve stem and the nut is prohibited, the nut is skewed, the thread is corroded by the medium, rust and other reasons. In addition, the selection of materials can also cause the valve stem to fail. For example, the valve stem and the valve stem nut are the same material, and they are simply bitten and cause failure.
Solution: Workers should carefully operate the knife gate valve when opening and closing. Strictly control the scale when opening and closing. Do not open and close the valve violently to prevent the valve stem from twisting. When opening, do not open to the top dead center. After opening the valve properly, turn the handwheel backward to make The upper side of the thread is tightly closed to prevent the medium from pushing the valve stem upwards; adjust the orientation of the nut; if it cannot be prevented from being corroded and rusted, replace the valve stem and the nut in time; choose nuts and stems of different materials.
2. The valve stem is not sensitive or stuck
The main reason for the insensitive rolling or jamming of the knife gate valve stem is that the packing is too tight; the packing does not meet the specifications when it is loaded into the stuffing box; the gap between the valve stem and the bushing is not good; the valve stem is tortuous; the thread surface roughness does not meet the requirements ; The information of the valve stem and the valve stem sleeve is not properly selected and other reasons.
Solution: properly loosen the packing gland screws; increase the charging according to the specification; control the gap between the valve stem and the bushing within the specification; control the surface roughness of the thread processing within the specification.
