Shut-Off Valve Maintenance

For the stop valve in operation, various valve parts should be complete and intact. The bolts on the flange and the bracket are indispensable, and the threads should be intact and no looseness is allowed. The tightening nut on the handwheel should be tightened in time if it is found to be loose to avoid wearing the connection or losing the handwheel and nameplate. If the hand wheel of the shut-off valve is lost, it is not allowed to replace it with an adjustable wrench, and it should be provided in time. The packing gland is not allowed to be skewed or have no pre-tightening gap. For shut-off valves in environments that are easily contaminated by rain, snow, dust, sand and other dirt, the valve stem should be equipped with a protective cover. The ruler on the shut-off valve should be complete, accurate and clear. The lead seals, caps, and pneumatic accessories of the globe valve should be complete and intact. It is not allowed to knock, stand on or support heavy objects on the shut-off valve in operation; especially non-metal valves and cast iron valves. It is also forbidden to maintain the valve during grease injection. Professional maintenance of the valve before and after production before welding , Serving the valve plays a vital role in the production and operation. Correct, orderly and effective maintenance will protect the valve, make the valve function normally and prolong the service life of the valve. Valve maintenance may seem simple, but it is not. There are often overlooked aspects of work.

First, when the globe valve is injecting grease, the problem of the amount of grease is often ignored. After grease injection and refueling, the operator selects the valve and grease injection connection mode, and then performs the grease injection operation. There are two situations: on the one hand, the amount of grease injection is small, and the grease injection is insufficient, and the sealing surface wears faster 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 sealing capacity of different shut-off valves according to the valve type category. The sealing capacity can be calculated based on the size and category of the globe valve, and then a reasonable amount of grease can be injected.

Second, when the globe valve is injecting grease, the pressure problem is often ignored. During the fat injection operation, the fat injection pressure changes regularly between peaks and valleys. If the pressure is too low, the seal leaks or fails, the pressure is too high, the grease injection port is blocked, the sealant is hardened, or the sealing ring is locked with the valve ball and valve plate. Generally, when the grease injection pressure is too low, the injected grease mostly flows into the bottom of the valve cavity, which usually occurs in small gate valves. If the grease injection pressure is too high, on the one hand, check the grease injection nozzle, if the grease hole is blocked, replace it; on the other hand, if the grease is hardened, use a cleaning fluid to repeatedly soften the failed sealing grease and inject new grease to replace it. . In addition, the seal type and sealing material also affect the grease injection pressure. Different sealing forms have different grease injection pressures. Generally, the grease injection pressure for hard seals is higher than that for soft seals. The ball valve is generally in the open position during maintenance. In special circumstances, it is selected to close for maintenance. Other valves cannot be treated as open positions. The gate valve must be closed during maintenance to ensure that the grease fills the sealing groove along the sealing ring. If it is opened, the sealing grease will directly fall into the flow channel or valve cavity, causing waste.

After installation, the stop valve should be inspected regularly, the main inspection items:

(1) Wear of the sealing surface of the globe valve.

(2) Wear of trapezoidal threads of valve stem and valve stem nut.

(3) Whether the packing is out of date and invalid, if it is damaged, it should be replaced in time.

(4) After the shut-off valve is overhauled and assembled, a sealing performance test should be carried out.