Methods to improve the service life of regulating valves

Thread Content

1) The life extension method of working at a large opening is to make the regulating valve work at the maximum opening as much as possible from the beginning, such as 90%. In this way, damage such as cavitation and erosion occurs on the head of the valve core. As the valve core is damaged and the flow rate increases, the corresponding valve will be closed a little further. This will continue to destroy and gradually close, so that the entire valve core can be fully utilized until the root and sealing surface of the valve core are damaged and cannot be used. At the same time, the throttling gap is large when working at a large opening, and erosion is weakened. This improves the service life by more than 1 to 5 times compared with having the valve work at an intermediate opening or a small opening from the beginning. For example, if a chemical plant adopts this method, the service life of the valve is increased by 2 times. 2) Reduce S, increase the working opening and increase the service life. The method of reducing S is to increase the loss of the system except the regulating valve and reduce the pressure drop distributed to the valve. In order to ensure the flow 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, which weakens cavitation and erosion. Specific methods include: An orifice plate is installed behind the valve to consume pressure drop. ； Close the manual valves 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 initially working with a small opening. 3) Reduce the diameter and increase the working opening. The method of increasing the service life is to increase the working opening by reducing the diameter of the valve. The specific methods are:: ①Change to a valve with a smaller caliber, such as DN32 to DN25. ； ②The valve body does not change, but the valve core and seat with a smaller seat diameter are replaced. For example, during the overhaul of a chemical plant, the throttling part dgl0 was replaced with dg8, and the service life was doubled. 4) Transfer the damaged position to improve the service life. Move the severely damaged place to a secondary position to protect the sealing surface and throttling surface of the valve core and seat. 5) Increase the throttling channel and improve the service life. The simplest way to increase the throttling channel is to thicken the valve seat to make the valve seat hole grow and form a longer throttling channel. On the one hand, it can delay the sudden expansion after closed-flow throttling and move the damage position away from the sealing surface. ； On the other hand, it increases the throttling resistance, reduces the degree of pressure recovery, and weakens cavitation. Some design the valve seat hole into a stepped or wavy shape, in order to increase resistance and weaken cavitation. This method is often used on high-pressure valves introduced into installations and when old valves are improved, and is also very effective. 6) Change the flow direction to improve the service life. If the open flow pattern flows in the open direction, cavitation and erosion mainly act on the sealing surface, causing the valve core root and the valve core and valve seat sealing surface to be quickly damaged. ； The closed flow type flows in the closed direction, and cavitation and erosion act after throttling, below the sealing surface of the valve seat, protecting the sealing surface and the root of the valve core, and extending the service life. When the problem of extending the life of a valve designed to be a flow-open type is more prominent, the life can be extended by 1 to 2 times simply by changing the flow direction. 7) The method of using special materials to improve the service life is to resist cavitation (destructive shapes such as honeycomb-shaped dots) and erosion (streamlined small grooves). Special materials that are resistant to cavitation and erosion can be used to manufacture throttling parts. This special material includes 6YC-1, A4 steel, Stellite, carbide, etc. To resist corrosion, materials that are more resistant to corrosion and have certain mechanical and physical properties can be used. This material is divided into two categories: non-metallic materials (such as rubber, PTFE, ceramics, etc.) and metallic materials (such as Monel, Hastelloy, etc.). 8) Change the valve structure to improve the service life. Change the valve structure or select a valve with a longer service life to achieve the purpose of improving the service life, such as selecting multi-stage valves, anti-cavitation valves, corrosion-resistant valves, etc.