Common problems and precautions in valve maintenance
Published: February 15, 2017 Author: 【191566.com】
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Daily valve maintenance
1. The valve should be stored in a dry and ventilated room, and both ends of the passage must be blocked.
2. Valves that have been stored for a long time should be checked regularly to remove dirt and coated with rust-proof oil on the processing surface.
3. After installation, regular inspections should be performed. The main inspection items are:
(1) Wear of sealing surface.
(2) The trapezoidal thread wear of the stem and stem nut.
(3) Whether the packing is out of date, if it is damaged, it should be replaced in time.
(4) After the valve is overhauled and assembled, the sealing performance test shall be performed.
Maintenance work during valve filling
The professional maintenance work of the valve before and before production and after production, plays a vital role in serving the valve in production and operation. Correct, orderly and effective maintenance will protect the valve, enable the valve to function properly and prolong valve use. life. Valve maintenance may seem simple, but it is not. There are often neglected aspects of work.
In the first place, when the valve is filled with grease, the problem of the amount of grease is often ignored. After the grease gun is refueled, the operator selects the valve and grease connection mode, and then performs the grease injection operation. There are two situations: On the one hand, the amount of grease injected is small, and the amount of grease injected is insufficient, and the sealing surface is accelerated due to lack of lubricant. On the other hand, excessive fat injection causes waste. The reason is that there is no accurate calculation of different valve sealing capacities according to the type of valve. The sealing capacity can be calculated based on the valve size and type, and then a reasonable amount of grease can be injected.
Second, the pressure problem is often ignored when the valve is filled with grease. During the fat injection operation, the fat injection pressure changed regularly in peaks and valleys. The pressure is too low, the seal leaks or fails, the pressure is too high, the grease injection port is blocked, the grease in the seal is hardened, or the seal ring is locked with the valve ball and valve plate. Usually when the grease injection pressure is too low, the injected grease flows into the bottom of the valve cavity, which usually occurs in small gate valves. The grease injection pressure is too high. On the one hand, check the grease injection nozzle, and replace it if the fat hole is blocked; on the other hand, if the grease is hardened, use a cleaning liquid, repeatedly soften the failed sealing grease, and inject new grease to replace . In addition, the seal type and seal material also affect the grease injection pressure. Different seal types have different grease injection pressures. Generally, the hard seal grease injection pressure is higher than the soft seal.
Third, pay attention to the problem of the valve in the switch position when filling the valve with grease. The ball valve is generally in the open position during maintenance. In special cases, the valve is closed for maintenance. Other valves cannot be treated in the same way. The gate valve must be closed during maintenance to ensure that the grease fills the sealing groove along the seal ring. If it is open, the seal grease will fall directly into the flow channel or valve cavity, causing waste.
Fourth, when the valve is filled with grease, the problem of the effect of fat filling is often ignored. During the fat injection operation, the pressure, the amount of fat injection, and the switch position are normal. However, in order to ensure the grease injection effect of the valve, it is sometimes necessary to open or close the valve and check the lubrication effect to confirm that the surface of the valve ball or the gate is evenly lubricated.
Fifth, pay attention to the problems of valve body drainage and wire plug pressure relief when injecting grease. After the valve pressure test, the gas and moisture in the sealed chamber valve cavity are increased due to the increase in ambient temperature. When the grease is injected, the drainage and pressure should be performed first to facilitate the smooth operation of the grease injection. The air and moisture in the sealed cavity are fully replaced after the grease injection. Releasing the valve cavity pressure in time also ensures the safety of the valve. After the end of the greasing, be sure to tighten the drain and pressure relief plugs to prevent accidents.
Sixth, pay attention to the problem of uniform fat production when injecting fat. During normal fat injection, the fat exit hole closer to the fat injection mouth will first make fat, then go to the low point, and then the high point, and then fat out one by one. If it is not in accordance with the rules or does not produce fat, it proves that there is a blockage, and it is cleared in time.
Seventh, it is also necessary to observe that the valve diameter is flush with the seat of the sealing ring when injecting grease. For example, for ball valves, if there is interference in the open position, you can adjust the open position limiter inward to confirm that the diameter is straight and lock it. Adjusting the limit cannot be pursued only by opening or closing one position, it must be considered as a whole. If the open position is flush and the close is not achieved, the valve will not close tightly. In the same way, when the adjustment is in place, we must also consider the corresponding adjustment of the opening. Ensure right-angle travel of the valve.
Eighth, the fat injection port must be closed after the fat injection. Avoid the entry of impurities, or oxidation of lipids at the grease injection port, and apply anti-rust grease to the cover to avoid rust. For the next operation.
Ninth, when injecting fat, we must also consider specific issues in the future delivery of oil products. In view of the different qualities of diesel and gasoline, the scouring and decomposition capabilities of gasoline should be considered. When the valve is operated in the future, when it encounters the operation in the gasoline section, it should be replenished in time to prevent wear and tear.
Tenth, don't neglect the grease injection at the valve stem part during the grease injection. The valve shaft has sliding sleeves or packings, and it is also necessary to maintain lubrication to reduce frictional resistance during operation. If lubrication cannot be ensured, the torque will increase when the electric parts are worn and the switches will be laborious during manual operation.
Eleventh, some ball valves are marked with arrows on the valve body. If there is no FIOW in English, it is the direction of the seal seat. It is not used as a reference for the flow direction of the valve. Normally, double seated ball valves have a bidirectional flow direction.
Twelfth, when maintaining the valve, pay attention to the problem of water in the electric head and its transmission mechanism. Especially infiltration of rainwater during the rainy season. One is to rust the transmission mechanism or transmission sleeve, and the other is to freeze in winter. As a result, the torque of the electric valve is too large, and the damage to the transmission components will cause the motor to no-load or the over-torque protection will trip and fail to achieve electric operation. Transmission parts are damaged and manual operation is not possible. After the over-torque protection action, the manual operation cannot be opened or closed. If it is forcibly operated, the internal alloy parts will be damaged.