Valve maintenance

- Apr 11, 2018-

Valve maintenance

The purpose of maintenance during the operation of the valve is to ensure that the valve is in a state of constant cleanliness, good lubrication, complete valve parts and normal operation.

(1) Cleaning of the valve

The surface of the valve, the trapezoidal thread on the valve stem and stem nut, the sliding portion of the stem nut and the bracket, and the contaminants such as gears, turbines, and media residues can cause wear and corrosion on the valve. Therefore, it is obviously very important to keep the outside of the valve and the active part clean and protect the integrity of the valve paint. The dust on the valve is suitable for brush sweeping and compressed air purging; the trapezoidal thread and the dirt between the teeth are suitable for rag scrubbing; the oil stains on the valve and residual media stains are suitable for steam purging, even brushing with a copper wire brush, Up to the processing surface, the mating surface shows a metallic luster, and the paint surface shows the true nature of the paint. The trap should be in charge of personnel, at least once in each shift, open the flushing valve and the plug at the bottom of the trap regularly for flushing, or remove the flush periodically to prevent dirt from clogging the valve.

(2) Lubrication of valves

Valve trapezoidal threads, sliding parts of stem nut and bracket, bearing parts, gears, worm gears, meshing parts of worm gear and other coordinated moving parts all require good lubrication conditions to reduce mutual friction and avoid mutual wear. Some parts are specially equipped with oil cups or grease nipples. If they are damaged or lost during operation, they should be repaired and cleaned.

Lubrication parts should be regularly refueled according to specific conditions. Frequently opened, high-temperature valves are suitable for intervals of one week to one month; infrequently opened, low-temperature valves can have longer refueling cycles. Lubricant organic oil, butter, molybdenum disulfide and graphite. High-temperature valves are not suitable for oil and butter. They are lost due to high temperature melting and are suitable for injection of molybdenum disulfide and graphite powder lubrication. For exposed parts that require lubrication, such as trapezoidal threads, gears, etc., if grease such as butter is used, it is easily contaminated with dust. When molybdenum disulfide and graphite powder are used for lubrication, dust is not easily contaminated and the lubrication effect is better than that of butter. Graphite powder is not easy to smear, and it can be used with a little oil or water-synthetic paste. The oil-filled plug valve should be filled with oil for a specified time, otherwise it will be easily worn and leaked.

(3) Valve injection

1 When the valve is filled with grease, the amount of grease is often neglected. After the grease gun is refilled, the operator selects the connection method of the valve and grease injection and then performs the grease injection operation. There are two situations: on the one hand, the amount of grease injected is insufficient, the grease injection is insufficient, and the sealing surface accelerates wear due to lack of lubricant. On the other hand, excessive fat injection causes waste. The reason is that there is no accurate calculation of the different valve sealing capacities depending on the type of valve. The seal capacity can be calculated in terms of valve size and type, and a proper amount of grease can be properly injected.

2 The pressure problem is often neglected when the valve is filled with grease. During the grease injection operation, the pressure of the injection grease changes regularly between the peak and the valley, the pressure is too low, the seal leaks or fails, the pressure is too high, the grease injection port is blocked, the seal grease hardens, or the seal ring and the ball body and the gate plate are locked. When the injection pressure is too low, the injected grease flows into the bottom of the cavity, which usually occurs in the small gate valve. The injection pressure is too high, on the one hand to check the grease injection mouth, if the grease hole is blocked and clear the situation to be replaced; on the other hand is the lipid hardening, use the cleaning fluid, repeatedly soften the failure of the sealing grease, and inject new grease Replacement. In addition, the sealing type and the sealing material also affect the injection pressure. Different sealing types have different injection pressures. In general, the hard sealing pressure is higher than the soft sealing.

3 When filling the valve, pay attention to the valve's position in the switch. Ball valve maintenance is generally open, under special circumstances choose to close the maintenance. No other valve can be said to be open. When the gate valve is being maintained, it must be closed to ensure that the grease fills the sealing groove along the seal ring. If it is in the open state, the sealing grease will directly fall into the flow path or valve cavity, causing waste.

4 When the valve is filled with grease, the grease injection effect is often neglected. During the grease injection operation, the pressure, grease injection volume, and switch position are all normal. However, in order to ensure the valve's grease injection effect, it is sometimes necessary to open or close the valve to check the lubrication effect and confirm that the surface of the valve ball or the gate plate is evenly lubricated.

5 When filling grease, pay attention to valve body drainage and plug pressure relief. After the valve pressure test, the gas and moisture in the valve chamber of the sealing chamber are boosted due to the increase of the ambient temperature. During the injection of the grease, the sewage discharge pressure is firstly used to facilitate the smooth progress of the grease injection work. The air and moisture in the sealed cavity after the grease injection are fully replaced. Timely release of the pressure in the valve chamber also ensures the safe use of the valve. After the grease is finished, be sure to tighten the drain and drain plugs to prevent accidents.

6 When filling grease, pay attention to the problem of even grease. For normal fat injection, the grease outlet closest to the grease injection port will be greased first, then to the low point, and finally the high point, and the grease will be produced successively. If you do not follow the law or grease, to prove that there is a blockage, you should clear it in time.

7 When filling the grease, observe the problem of the valve diameter being flush with the seal seat. For example, if there is an open position in the ball valve, the open position limiter can be adjusted inward to confirm the straightness and lock. Adjusting the limit can only be used to open or close a position. Consider the overall situation. If the open position is flush and the position is not closed, the valve will not be closed tightly. In the same way, adjustments must be made in order to take corresponding adjustments into account. Make sure the valve's right angle travel.

8 After filling the fat, seal the grease injection hole. Prevent impurities from entering, or lipid oxidation at the grease injection port. Apply anti-rust grease to the cover to avoid rust and apply it for the next operation.

9 When injecting grease, consider the specific treatment of the oil in the future. Given the different qualities of diesel and gasoline, the scour and decomposition capabilities of gasoline should be considered. After the valve is operated and the gasoline section is encountered, grease is added in time to prevent the occurrence of wear.

10 When filling grease, do not ignore the grease in the stem area. There is a sliding sleeve or packing on the valve shaft, which also needs to maintain the lubrication state to reduce the frictional resistance during operation. If the lubrication cannot be ensured, the torque will be increased when the motor is operated, and the switch will be laborious when operated manually.

11 Some ball valves are marked with an arrow, if no English "FLOW" is attached. The handwriting is the direction of action of the seal seat, not as a reference for the flow direction of the medium, and the valve is self-relieving in the opposite direction. Normally, a two-seat sealed ball valve has bidirectional flow.