Pipe Ball Valve Common Faults and Troubleshooting

1. Ball valve leakage within

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

(1) Causes of Leakage in Ball Valves

1) Causes of internal leakage in the valve during construction:

1 Improper transport and lifting cause damage to the valve and cause internal leakage of the valve.

2 At the time of delivery, the water pressure did not dry the valve and carry out anti-corrosion treatment, causing the sealing surface to rust and form internal leakage.

3 The protection of the construction site was not in place. Blinds were not installed at both ends of the valve. Impurities such as rain and sand entered the valve seat, causing leakage.

4 When installing, no grease is injected into the valve seat, causing impurities to enter the rear of the valve seat, or internal leakage caused by burns during welding;

5 The valve is not installed in the fully open position, causing damage to the ball. If the valve is not in the fully open position during welding, welding spatter will cause damage to the ball. When the ball with welding spatter is in the switch, it will further damage the valve seat. , which leads to endoleaks;

6 welding residue and other construction remnants cause scratches on the sealing surface;

7 Leakage caused by inaccurate limit at the factory or during installation. If the stem drive bushing or other accessories are misaligned with the assembly, the valve will leak.

2) Causes of valve internal leakage during operation:

1 The most common reason is that the operation manager does not maintain the valve in consideration of the relatively expensive maintenance cost, or lacks scientific valve management and maintenance methods to prevent preventive maintenance of the valve, resulting in premature failure of the equipment;

2 improper operation or maintenance in accordance with the maintenance program caused by internal leakage;

3 During normal operation, construction remnants scratch the sealing surface, causing internal leakage;

4Immediate leakage due to seal surface damage caused by improper pigging;

5 Long-term maintenance or inactivity of the valve, causing the valve seat and ball to lock up, causing leakage damage when the valve is opened and closed;

6 The internal leakage is caused by the valve not reaching the position. Any ball valve, regardless of the opening or closing position, is inclined by 2° to 3°, which may cause leakage.

7 Many large-diameter ball valves have valve stem stoppers. If they are used for a long time, rust, dust, paint, and other debris will accumulate between the stem and the stem stopper blocks due to corrosion. These debris will cause the valve. Failure to rotate into place causes leakage. If the valve is buried, lengthening the valve stem will create and drop more rust and impurities to prevent the valve ball from rotating into place, causing the valve to leak.

8 The general actuator is also limited. If it causes rust for a long time, the hardening of the grease or loosening of the limit bolt will make the limit inaccurate and cause internal leakage;

9 The valve position of the electric actuator is set at the front, and there is no internal leakage caused by closing.

10 The lack of periodic maintenance and care causes the seal grease to dry and harden. The dried sealant accumulates on the elastic valve seat, hinders the movement of the valve seat, and causes seal failure.

(2) How to determine inner leakage

Natural gas pipelines are commonly used fixed-axis ball valve, the general inspection method is: the valve is turned to fully open or fully closed position, through the discharge of the valve body discharge nozzle to check for leaks. If it can be cleaned, the seal is proven to be good. If pressure is always discharged, the valve may be considered to be leaking, and the valve must be treated accordingly. However, it should be emphasized that the GROVE B-5 and B-7A ball valves, PBV ball valves and ROBERT CORT ball valves can only be checked in the fully closed position, because these ball valves open a passage in the valve body and are fully open. When used to balance the pressure of the pipeline and valve chamber. However, when it is fully closed, this will not happen.

(3) Endoleak processing procedures

1 First check the limit of the valve to see if the inner leakage of the valve can be solved by adjusting the limit.

2 First inject a certain amount of grease to see if it can stop leaking. At this time, the injection speed must be slow. At the same time, observe the change of the index of the grease gun outlet pressure gauge to determine the inner leakage of the valve.

3 If the leakage cannot be stopped, it may be that the early-injection sealant becomes hard or the sealing surface is damaged and the inner leakage occurs. It is recommended to inject valve cleaning fluid at this time to clean the valve sealing surface and valve seat. It usually takes at least half an hour to soak, if necessary, it can be soaked for a few hours or even several days. After the cured product is completely dissolved, the next step is performed. It is best to switch the valve several times during this process.

4 re-inject grease, intermittently open and close the valve, the impurities out of the valve seat cavity and sealing surface.

5 Inspect the fully closed position. If there is still leakage, intensified sealing grease should be injected. At the same time, the valve chamber is opened for venting. This can generate a large pressure difference, which helps to seal. Under normal circumstances, it injects the reinforced sealing grease. Endoleak can be eliminated.

6 If there is still an internal leakage, repair or replace the valve.

2 . Valve stem leakage

Most ball valves have upper and lower seals on the valve stem. Under normal circumstances, no maintenance is required. However, due to prolonged wear or aging, leakage may occur at the valve stem. For a populated valve stem, temporary leakage can be achieved by injecting sealing grease. Add sealant grease should be slow, it is best to use manual grease gun. When the leak stops, filling should be stopped. Excessive filling will cause the valve stem to turn hard. Of course, some valve stems may be sealed according to the structure by injecting a seal packing or compressing a packing gland.

3 . Ball operation abnormal

1) The ball valve will not be maintained and operated for a long time, and the valve seat may lock up with the ball. In this case, the operation of the valve is laborious or even impossible. At this time, it is better to inject a certain amount of cleaning liquid for a certain period of time and then operate.

2) Garbage, sand, dust, or aged, hardened sealing grease in the pipeline accumulates around the seat ring and affects the seat movement, causing the seat ring to jam and causing leakage between the seat and the ball. The valve is usually filled with cleaning fluid to remove impurities.

3) When the water content in natural gas is high, condensate water will appear during the transportation process as the environment changes. Water in the valve will be at the lowest point of the valve. This will usually be the lower pivot or the lower part of the ball valve body. It will freeze in cold temperatures and cause the valve to open and close.

4) When handling the leakage of the valve stem, too tight on the compression screw causes difficulty in the switch and the compression screw should not be too loose or too tight.

5) For the ball valve operated by the turbine, worm meshing drive may also have the following reasons:

1 The gear teeth are seriously worn or broken, resulting in failure to engage properly;

2 The safety pin on the worm is broken;

3 Bearing damage on worm or worm gear;

4 The lubrication of turbines and worms is not good. Greases used in these places are usually petroleum-based and can be contaminated by water. In cold weather, these waters can freeze, making the valves inoperable. If this happens, dismantle the gear box to remove all ice, water, and contaminated grease, and re-apply new grease. If it is particularly cold, it is best to use a low-temperature grease, such as ethanol-based grease;

5 The bolts connected to the gear box and the valve body are loose or sheared;

6 electric head failure, no power, wiring or settings error.

6) For the gas-liquid linkage ball valve, there may also be the following reasons:

1 gas line, oil line may be blocked or the pipeline speed limit valve is closed;

2 The pressure of the air source is insufficient;

3 hydraulic cylinder or rotary component sealing failure;

4 pressure difference and other reasons cause excessive torque.

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, especially during the construction and commissioning period. Suggestions for this:

1      Strengthen supervision of pre-shipment maintenance of equipment and supervision during transportation;

2      Strengthen the maintenance, maintenance and supervision of the installation process before installation on site;

3      Prior to installation, water pressure tests must be conducted to detect problems early and handle them as soon as possible;

4      Change the concept, conduct preventive maintenance management, formulate a periodic maintenance plan and strictly implement it;

5      Strengthen professional training, improve the quality of professional maintenance personnel, and ensure the maintenance of science, standards and safety;

6      Establish and improve equipment maintenance, maintenance, and accounting records for factory shipment, transportation, installation, testing, and use, and record and accumulate raw data for future management work;

7      Conduct continuous exploration and establish relevant and scientific maintenance procedures and inspection standards.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.