Globe valves should be checked regularly
For the globe valve in operation, various valve parts should be complete and intact. The bolts on the flange and the bracket are indispensable, the threads should be intact, and no loosening is allowed. If the tightening nut on the handwheel is found to be loose, it should be tightened in time to avoid abrasion of the connection or loss of the handwheel and nameplate. If the handwheel of the globe valve is lost, it is not allowed to replace it with an adjustable wrench, and it should be completed in time. Packing glands are not allowed to be skewed or have no preload clearance. For globe valves in environments that are easily contaminated by rain, snow, dust, sand and other pollutants, a protective cover should be installed on the valve stem. The scale on the globe valve should be kept intact, accurate and clear. The lead seal, cap, and pneumatic accessories of the globe valve should be complete and intact. It is not allowed to knock, stand or support heavy objects on the globe valve in operation; especially for non-metallic valves and cast iron valves, it is also necessary to prohibit the maintenance work when the valve is greased. Professional maintenance work of the valve before welding and after it is put into production , It plays a vital role in the production and operation of the valve. Correct and orderly and effective maintenance will protect the valve, make the valve function normally and prolong the service life of the valve. Valve maintenance work may seem simple, but it is not. There are often overlooked aspects of work.
First, when injecting grease into the globe valve, the amount of grease injection is often ignored. After grease injection and refueling, the operator selects the valve and the grease injection connection method, 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 quickly due to the lack of lubricant. On the other hand, excessive grease injection results in waste. The reason is that there is no precise calculation of the sealing capacity of different globe valves according to the valve type category. The sealing capacity can be calculated based on the size and type of the globe valve, and then a reasonable amount of grease can be injected.
Second, when the globe valve is greased, the pressure problem is often ignored. During the grease injection operation, the grease injection pressure changes regularly with 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 sealing inner grease is hardened, or the sealing ring is locked with the valve ball and valve plate. Usually, 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, and replace it if the grease hole is blocked. . In addition, the sealing type and sealing material also affect the grease injection pressure. Different sealing forms have different grease injection pressures. Generally, the grease injection pressure of hard seals is higher than that of soft seals. The ball valve is generally in the open position during maintenance, and in special cases, it is selected to be closed for maintenance. Other valves can not be regarded as open position. 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 fall directly into the flow channel or valve cavity, causing waste.
After installation, the globe valve should be inspected regularly. The main inspection items:
(1) The wear of the sealing surface of the globe valve.
(2) The wear of the trapezoidal thread of the stem and stem nut.
(3) Whether the packing is outdated and invalid, if damaged, it should be replaced in time.
(4) After the globe valve is repaired and assembled, the sealing performance test should be carried out.