The control valve itself may have the following faults:
1, the valve stem deformation; due to improper transportation or use conditions are not (pressure difference beyond the allowable range) caused by excessive leakage. Because the force is not enough. Or the sealing surface has impurities deposition, so that the valve core and valve seat damage.
2, the valve body and valve cover, or valve cover and the junction of the stem is not tight. The reason is the tightness of the components, or the chosen packing is not suitable for the working conditions.
3, the valve (or butterfly valve plate) wear guide system. It is caused by high pressure difference and strong force.
Main fault element of regulating valve:
1, valve: always check valve wall from corrosion and wear, especially for the harsh conditions of corrosive media and high differential pressure and cavitation under the valve, must ensure that the compressive strength and corrosion resistance, wear resistance.
2, the valve spool: because to adjust and cut off the effect of fluid, closure element is the collision, so the erosion and corrosion of particles by the media, the most serious, more easily damaged in high differential pressure and cavitation condition, so check the parts whether damage, wear and corrosion, whether to repair or replace.
3, valve seat: the valve seat joint surface is the key to ensure the valve closed, it is affected by the rot is also relatively serious wear. And because of the penetration of the medium, the internal surface of the fixed valve seat is often corroded and loose, especially to check this part.
4, stem: check the stem and spool, push rod connection loose, whether it produces excessive deformation, cracks and corrosion.
5, packing: check PTFE or other filler whether aging, lack of oil, deterioration, packing whether compression.
6, gaskets and O ring: these vulnerable parts can not crack, aging.
The pneumatic actuator may have the following faults:
1, rubber gasket sealing area leakage, the reason is accessories wear, diaphragm rupture, mainly due to the inferior quality of rubber, metal contact surface quality is not good (sharp edge).
2, spring break, because the force is too large or improper processing (improper heat treatment) caused.
3. The membrane head and the connecting air duct are not tight. Because of the uneven force or improper connection when tightening the membrane head.
The electric actuator may have the following faults:
1, the travel limit is irregular. Due to improper transportation or installation.
2, the coupling weakness caused by the same reason, the motor overheating, due to improper location of motor installation caused.