How to use valves correctly and how to maintain and repair them - Knowledge

How to use the valve correctly is the knowledge that users must master. Only correct use can make it last longer. Therefore, the hydraulic control valve center recommends that you must carefully read the instruction manual before installing and using the valve, and strictly operate and maintain it according to the instruction manual of the valve. Negligence and recklessness are the main causes of valve damage. We know that the maintenance workload required for most valves is very small, which means that most valves do not need to be repaired frequently. Sometimes even a small problem such as a simple valve stem leakage often becomes a big problem due to negligence. What's more, some reckless operators do not close the valve according to the requirements of technical specifications, resulting in valve stem bending or serious damage to the closing parts. Such situations happen from time to time. The threaded mating parts of the valve stem nut and the valve stem should be lubricated regularly with lubricating oil, which can not only reduce the friction between them, but also extend their service life. This is also a very important protective measure. If the worn valve stem nut is still in use, it may break, so that the entire axial force of the valve stem cannot be supported and the valve will lose its function. The gasket starts with a simple leak, and finally reaches the hazard of steam leakage. To avoid this danger, the valve cover bolts should be tightened properly when the leakage begins; if the valve seat sealing surface is improperly selected due to material selection, it will start with a small amount of leakage, which may later expand to groove leakage. If there are reasons such as insufficient opening height, the erosion of the fluid will be accelerated, resulting in complete damage to the valve seat.
The reason for the bending of the valve stem may be that the operator turns the handwheel excessively after closing the valve.
There are many reasons for valve damage. In fact, if the operator is slightly trained, similar situations may be avoided.
Now the use, maintenance and repair of several common valves are explained one by one.
The stop valve is a commonly used shut-off valve, which is mainly used to connect or cut off the medium in the pipeline. In the pipeline system, the time when the stop valve is not operated is very short, so regular maintenance is required.
A small amount of packing leakage can be solved by simply tightening the packing gland nut. However, when the packing is damaged, the packing must be replaced. When replacing the packing, the valve must be fully opened to allow the upper seal to work (generally possible under pressure). When replacing, install appropriate packing in the stuffing box and tighten the packing gland nut. Check it regularly in the future to prevent the gland nut from loosening. When replacing the valve disc parts, lift the valve stem, disassemble the valve cover, and then install the new valve disc on the new clamping frame. Turn the valve stem until the valve disc is disengaged from the clamping frame, replace it with a new valve disc and clamping frame, and install it into the valve. The operation of replacing the valve disc is convenient. In order to grind the valve disc (the valve that can be ground and updated), use a small amount of abrasive on the valve disc, and then grind it. The grinding method is to place an axle pin on the valve disc nut groove and the hole of the valve stem support head, place the assembly on the valve body, unscrew the connecting sleeve, and then grind it alternately in forward and reverse directions. Use the valve stem as a grinding tool, put in the abrasive and grind it. The grinding should not be excessive. When the grinding is completed, clean the abrasive and then lubricate the thread. Check valve The function of the check valve is to allow fluid to pass only in one direction to prevent the medium from flowing back. The most common type of check valve in urea equipment is the lift check valve, whose valve disc moves up and down along the center line of the channel. The action is reliable, but the fluid resistance is large, and it is suitable for small and medium-sized occasions. Lift check valves can be divided into straight-through type and vertical or angle type. Straight-through lift check valves
Generally can only be installed in horizontal pipelines, while vertical lift check valves should generally be installed in vertical pipelines, and the medium flows from bottom to top, while angle lift check valves can only be installed in vertical pipelines.
Pay special attention when adjusting larger spring-loaded safety valves, because neither users, manufacturers nor maintenance workshops have sufficient ability to accurately calibrate the discharge pressure. Unless accurately adjusted at the manufacturer or on the actual device, no adjustment shall be made to the spring-loaded safety valve.