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Common problems and solutions of gate valves

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The gate valve is used as a cut-off medium, and the whole flow is straight when it is fully opened. At this time, the pressure loss of the medium is minimal. Gate valves are usually suitable for working conditions that do not need to be opened and closed frequently and keep the gate fully open or fully closed. Not suitable for fine-tuning or throttling use.

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For high-speed flowing media, the gate can cause a vibration of the gate when it is partially opened, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the gate to be eroded by the medium. From the structural form, the main difference is the form of the sealing element used. According to the form of sealing elements, gate valves are often divided into several different types, such as wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate valve, etc.

Gate valve is one of the valves often used in pipelines, but many users lack relevant maintenance and maintenance knowledge during the use of gate valves, and lack the corresponding technical guidance during installation, resulting in various minor problems. In response to such problems, our factory has made a comprehensive summary of various situations based on years of production and installation experience. As long as users can master these points, they will easily solve some common small problems during the use and maintenance of the gate valve.

1. If the gate valve is not in use temporarily, both ends of the valve cavity should be blocked and placed in a dry and ventilated room. During long-term storage, the processing surface should be coated with anti-rust oil.
2. The gate valve is recommended to be installed on a horizontal pipeline, that is, the centerline of the valve stem is perpendicular to the horizontal pipeline, and the driving part is on the top. The installation of the gate valve should ensure convenient work, maintenance, and operation.
3. The gate valve is required to be fully open or fully closed during use. It is not allowed to be used as a throttle valve to prevent the sealing surface from being damaged when the pipeline flow rate is high.
4. For gate valves with bypass valves, the bypass valve should be opened before the main valve is opened. When the valve is closed, the bypass valve should also be closed at the same time.
5. When opening or closing the valve, use a handwheel or electrical switch, and do not use auxiliary levers or other tools.
6. When starting the valve, the sling is not allowed to be tied to the handwheel, motor, or gearbox.
7. The transmission part should be kept clean, and lubricant should be added regularly.
8. The following work should be done during installation:
(1) Clean the inner cavity and the sealing surface, and no dirt is allowed.
(2) Check whether the connecting bolts are evenly tightened, and check whether the filling and shaking are tight. After the packing is compressed, the sealing of the packing should be ensured and the rotation of the valve stem should not be hindered.
(3) It must be checked whether the mark on the valve meets the requirements for use.

For gate valves with electric drive devices, the following should also be done:
After the valve is assembled, the stroke control device should be adjusted step by step, and it can be energized for use after adjustment. When opening and closing the valve, the rotation direction of the motor should be consistent with the opening and closing direction indicated by the stroke control device. When the stroke control device is not adjusted, it should be prevented that the valve is not adjusted to the required position, and the valve is damaged by crossing the allowable opening and closing range of the valve.

9. After installation, it should be checked regularly.
(1) Wear of the sealing surface.
(2) The thread damage of the valve stem and the valve stem nut.
(3) Whether the packing is invalid.
(4) Wear between worm gears, worms, and gears.
(5) Whether the joints in the electrical control circuit are firm and reliable, and whether the electrical components work normally.
(6) Whether each part of the stroke control device works normally.
10. After the valve is overhauled and assembled, the stroke control device must be readjusted and the sealing performance test must be carried out.




There are the following items about possible failures and their elimination methods:

1.Leakage on the sealing surface.
(1) If dirt adheres between the sealing surfaces, it should be rinsed.
(2) If the sealing surface is damaged, the sealing ring should be processed and repaired, or replaced.
2. Leakage at the filler:
(1) If the packing gland is not compressed, the packing should be evenly compressed.
(2) If the packing is not enough, increase the packing.
(3) If the packing has been used for a long time, or if it becomes invalid due to improper storage, the packing should be replaced.
3. Leakage at the connection between the valve body and bonnet:
(1) If the connecting bolts are not evenly tightened, they should be tightened evenly.
(2) If the connecting surface of the valve body and the bonnet is damaged, it should be repaired.
(3) If the gasket is damaged, replace the gasket.
4. The gate cannot be opened and closed or the valve stem cannot be rotated flexibly:
(1) If the packing is too tight, the nut of the packing gland should be properly loosened.
(2) If the thread on the valve stem is damaged or has dirt accumulated, the thread should be disassembled, trimmed and dirt removed. ’
(3) If the thread of the stem nut is severely worn or broken, the stem nut should be replaced.
(4) If the valve stem is bent, calibration should be added.
(5) Contaminants accumulate between the gate and the valve body, which should be eliminated.
(6) The connecting device between the gate and the valve stem is corroded and damaged, and the connecting device should be replaced

The following situations may also occur in gate valves with electric devices:
5. The rotation direction of the motor is opposite to the indicated direction. If the input of the mainline is reversed, any two of the three live wires of the mainline should be switched on.
6. The motor is idling, accompanied by a harsh clicking sound. This may be that the worm clutch and the motor clutch are not connected, then the pull rod should be turned or the electric device should be disassembled to check and eliminate the fault.
7. When the valve opens or closes to the end, the motor continues to run:
(1) The contact of the travel switch is in poor contact. Check and repair the contact piece to make the contact good.
(2) When the stroke controller fails or the adjustment position is incorrect, recheck or adjust the stroke control device

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