Ways to improve the service life of control valves

Ways to improve the service life of control valves

The control valve is not like a manual valve. After it is installed, it is rarely managed and maintained. It must be maintained frequently to ensure normal operation and long service life. Below we introduce eight ways to extend the service life of the control valve.

　　1) Wide opening work

　　 Let the regulating valve work at the maximum opening as far as possible from the beginning, such as 80%. In this way, damage such as cavitation and erosion occurs on the head of the valve core. As the spool is destroyed and the flow increases, the corresponding valve is closed again. This will continue to break and gradually close, so that the entire spool is fully utilized until the root and sealing surface of the spool are damaged and cannot be used. At the same time, the large-opening operation has a large throttle clearance and weakened erosion, which can increase the service life by more than 1 to 5 times than letting the valve work at the middle and small openings from the beginning. If a chemical plant adopts this method, the service life of the valve is increased by 2 times.

　　2) Decrease S to increase working opening

Reducing S means increasing the loss of the system except for the regulating valve and reducing the pressure drop distributed to the valve. In order to ensure that the flow passes through the regulating valve, the opening of the regulating valve must be increased. At the same time, the pressure drop on the valve is reduced to make Cavitation and erosion are also weakened. The specific methods are as follows: set an orifice throttling behind the valve to consume pressure drop; close the manual valve connected in series on the pipeline until the regulating valve obtains a more ideal working opening. It is very simple, convenient and effective to use this method when the valve is selected at a small opening at the beginning.

　　3) Reduce the diameter and increase the working opening

By reducing the valve diameter to increase the working opening, the specific methods are: ①Change a valve with a smaller diameter, such as DN32 to DN25; ②The valve body does not change, and replace the valve core valve with a small seat diameter seat. For example, when a chemical plant was overhauled, the throttling piece dgl0 was replaced with dg8, and the service life was doubled.

　　4) Transfer the damage location

　　 Move the severely damaged place to a secondary position to protect the sealing surface and throttle surface of the valve core and seat.

　　5) Increase throttling channel

　　The easiest way to increase the throttling passage is to thicken the valve seat to increase the seat hole and form a longer throttling passage. On the one hand, the sudden expansion after the flow closed throttling can be delayed, and the damage position can be shifted away from the sealing surface; on the other hand, the throttling resistance is increased, the pressure recovery degree is reduced, and the steam Eclipse weakened. Some of the valve seat holes are designed to be stepped or waved in order to increase resistance and weaken cavitation. This method is often used when introducing high-pressure valves in the device and when improving old valves, and it is also very effective.

　　6) Change the flow

The flow-open type flows in the opening direction, and cavitation and erosion mainly act on the sealing surface, which quickly damages the valve core root and the valve seat sealing surface; the flow-close type flows in the closed direction, causing cavitation and erosion. After throttling, below the sealing surface of the valve seat, the sealing surface and the root of the valve core are protected and the service life is extended. The valve pretending to be a flow-open type, when the problem of extending the life is more prominent, only need to change the flow direction to extend the life by 1 to 2 times.

　　7) Change to special materials

　　 is anti-cavitation (damaged shape like small honeycomb dots) and scouring (streamlined small grooves), it can be replaced with special materials resistant to cavitation and scouring to make the throttle. This special material includes 6YC-1, A4 steel, Stellite, cemented carbide and so on. In order to resist corrosion, it can be changed to use more corrosion resistant materials with certain mechanical and physical properties. This material is divided into two types: non-metallic materials (such as rubber, PTFE, ceramics, etc.) and metal materials (such as Monel, Hastelloy, etc.).

　　8) Change the valve structure

　　 To achieve the purpose of improving the life by changing the valve structure or selecting a valve with a longer life, such as the use of multi-stage pressure reducing valves, anti-cavitation valves, corrosion-resistant valves, etc.