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Installation and maintenance of gate valve

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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 small. 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.

Table of Contents

Rising stem gate valve

For high-speed flowing media, the gate can cause the gate to vibrate when 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 suffer from the erosion of 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 grasp these points, they will easily solve some common small problems during the use and maintenance of the gate valve.

Common precautions and solutions to some minor problems during the use and maintenance of gate valves include:

  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. For 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 center line 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 the convenience of work, maintenance and operation.
  3. The gate valve is required to be fully opened 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 a bypass valve, the bypass valve should be opened before the main valve is opened. When the valve is closed, the bypass valve should 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 gear box
  7. The transmission part should be kept clean and regularly filled with lubricant
  8. The work that should be paid attention to during the installation of the gate valve:
    (1) Clean the inner cavity and sealing surface, no dirt is allowed
    (2) Check whether the connecting bolts are evenly tightened, and check whether the packing is tight. After compacting the packing, ensure the sealing of the packing and not hinder the rotation of the valve stem
    (3) Must check 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 exceeding the allowable opening and closing range,which damage the valve because valve is not adjusted to the required position.
  9. What are the items to be checked regularly for the gate valve after installation:
    (1) Wear of the sealing surface.
    (2) The thread of the stem and stem nut damaged condition .
    (3) Whether the packing fails.
    (4) Wear between worm gears, worms, and gears.
    (5) Whether the connectors 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.

Gate valve use site

What are the possible faults of the gate valve and their elimination methods:

  1. Leakage of seat surface:
    (1)If there is dirt attached between the seat surfaces, it should be rinsed
    (2)If the seat surface is damaged, the sealing ring should be repaired or replaced.
  2. Leakage in packing:
    (1)If the packing gland is not compressed, the packing should be evenly compressed.
    (2)If the packing is not enough, add packing
    (3)If the packing has been used for a long time, or it becomes invalid due to improper storage, the packing should be replaced
  3. Leakage at the connection between the valve body and the 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, repair it

(3)If the gasket is damaged, replace the gasket

4. The gate cannot be opened or closed or the valve stem is not flexible

(1)If the packing is too tight, loosen the nut of the packing gland properly
(2)If the thread on the valve stem is damaged or there is dirt, it should be disassembled, trimmed and cleaned.
(3)The thread of the stem nut is severely worn or broken, the stem nut should be replaced
(4)The valve stem is bent and should be calibrated
(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, the connecting device should be replaced

What are the possible situations in gate valves with electronic equipment:

  1. The motor rotation direction is opposite to the indicated direction. If the input of the main line is reversed, any two of the three live wires of the main line should be switched on.
  2. The motor is idling, accompanied by a harsh click. It 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.
  3. When the valve opens or closes to the end, the motor continues to run
    (1)The contact of the limit switch is in poor contact. Check and repair the contact piece to ensure good contact
    (2)When the limit switch fails or the adjustment position is incorrect, recheck or adjust the limit switch.
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