1. The valve stem is deformed; due to improper transportation or improper use conditions (pressure difference is beyond the allowable range), the leakage amount is too large. Due to insufficient force. Or the deposition of impurities on the sealing surface breaks the fit between the valve plug and the valve seat.
2. The joint between valve body and valve cover or valve cover and alarm rod is not strict. The reason is that the parts are not tight enough, or the selected packing is not suitable for working conditions.
3, the spool (or disc valve plate) guide system wear. Due to the large pressure difference and strong force.
The main fault elements of the regulating valve:
1. Body: Always check the corrosion and wear of the inner wall of the valve, especially the valves used for corrosive medium and high pressure difference, cavitation and other harsh process conditions, must ensure its compressive strength and corrosion resistance. Grinding performance.
2ã€Spool: Because the spool plays a role in regulating and cutting off the fluid, it is a shut-off element of the activity. Therefore, it is affected by the erosion, corrosion, and particle collision of the medium. It is more easily damaged in the case of high pressure difference and cavitation, so Check that all parts of it are damaged, worn, corroded, and repaired or replaced.
3, valve seat: valve seat joint surface is the key to ensure that the valve is closed, it is subject to corruption grinding situation is also more serious. Moreover, due to the penetration of the medium, the inner surface of the thread of the fixed valve seat is often eroded and loosened, and this area must be particularly inspected.
4. Stem: Check whether there is any looseness in the connection between the valve stem and the valve plug and the push rod, and whether there is excessive deformation, crack and corrosion.
5. Filler: Check whether PTFE or other fillers are aging, lack of oil, deterioration, and whether the packing is compacted.
6, gaskets and O-rings: these vulnerable parts can not be cracked, aging.
Pneumatic actuators may have the following failures:
1. Leakage in the seal area of ​​the rubber gasket, due to wear of the fittings and rupture of the diaphragm, mainly due to poor quality of the rubber and poor quality of the metal contact surface (sharp edges).
2. The spring is broken due to excessive force or improper processing (incorrect heat treatment).
3, the membrane head and connecting duct are not tight. It is due to uneven force or improper connection when the membrane head is tightened.
Electric actuators may have the following failures:
1, irregular travel limit. Caused by improper transport or installation.
2. The coupling is weak due to the same reasons as above. The motor is overheated due to improper installation of the motor.
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