Maintenance of natural gas pipeline ball valve and common troubleshooting methods

Documents | Detials

1. Daily maintenance and maintenance suggestions during operation

2. Maintenance and management during construction

Common faults and troubleshooting methods

1. Ball valve internal leakage

Ball valve internal leakage is the most common problem of natural gas pipeline ball valves.

Reasons for internal leakage of ball valve

  1. Reasons for the internal leakage of the valve during the construction period:
  1. Reasons for internal valve leakage during operation:

Judgment method of internal leakage

The fixed shaft ball valve is commonly used on natural gas pipelines. The general inspection method is: turn the valve to the fully open or fully closed position, and check whether there is any leakage through the discharge of the valve body drain nozzle. If it can be drained, the seal is good. If the pressure is always discharged, it can be considered that the valve is leaking, and the valve must be treated accordingly. But it should be particularly emphasized that for GRoVE B-5 and B-7A ball valves, PBV ball valves, and ROBERT CORT ball valves, inspections can only be performed in the fully closed position because this type of ball valve opens a passage on the valve body. When it is used to balance the pressure of the pipeline and valve cavity. But when the position is fully closed, this will not happen.

Procedure for internal leakage

  1. First check the valve limit to see if the internal leakage of the valve can be solved by adjusting the limit.
  2. Inject a certain amount of grease first to see if the leakage can be stopped. At this time, the injection speed must be slow. At the same time, observe the change of the pressure gauge pointer at the outlet of the grease gun to determine the internal leakage of the valve.
  3. If the leakage cannot be stopped, it is possible that the sealing grease injected early becomes hard or the sealing surface is damaged, causing internal leakage. It is recommended to inject the valve cleaning fluid at this time to clean the valve sealing surface and valve seat. Generally, soak for at least half an hour, if necessary, you can soak for several hours or even days. After the solidified material is completely dissolved, do the next step. It is best to open and close the active valve several times during this process.
  4. Re-inject grease, open and close the valve intermittently, and drain impurities out of the back cavity and sealing surface of the valve seat.
  5. Check in the fully closed position. If there is still leakage, inject reinforced sealant grease, and open the valve cavity to vent at the same time. This can generate a large pressure difference and help seal. Generally, by injecting reinforced sealant grease, the internal leakage can be eliminated.
  6. If there is still internal leakage, repair or replace the valve.

2. Stem leakage

The valve stem of most ball valves is equipped with upper and lower seals. Under normal circumstances, no maintenance is required. However, due to long-term wear or aging, leakage may occur at the valve stem. For valve stems with injection ports, sealing grease can be injected to temporarily stop leakage. Filling the sealing grease should be slow, preferably with a manual grease gun. When the leakage stops, the filling should be stopped. Too much filling will cause difficulty in the rotation of the valve stem. Of course, some valve stems can be sealed by injecting packing or pressing the packing gland according to the structure.

3. Abnormal operation of the ball valve

  1. If the ball valve is not maintained and moved for a long time, the valve seat may lock up with the ball. In this case, it is more laborious to operate the valve or even unable to operate. At this time, it is best to inject a certain amount of cleaning fluid and soak for a period of time and then operate.
  2. Garbage, sand, dust, or aging, hardened sealing grease in the pipeline accumulates around the seat ring and affects the seat action, causing the seat ring to jam, causing leakage between the seat and the ball. Usually, inject cleaning fluid into the valve to remove impurities.
  3. When the water content in natural gas is high, condensate water will appear as the environment changes during transportation. The water in the valve will have the lowest point of the valve, which is usually the lower pivot or the lower part of the valve body of the ball valve, which freezes in the lower temperature and cold conditions, causing the valve to open and close.
  4. When dealing with valve stem leakage, the compression screw is too tight to cause difficulty in switching, and the compression screw should not be too loose or too tight.
  5. For ball valves operated by worm gear and worm gear meshing transmission, there may also be the following reasons:
  1. There may be the following reasons for the gas-liquid linkage ball valve:

To sum up

In order to improve the reliability of the valve and prolong the service life of the valve, it is very important to do early maintenance and supervision work, especially during the construction period and the production period. To this end, it is recommended:

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