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Ways to improve life - control valve common troubleshooting

In industrial automation instruments, the regulating valve is cumbersome, and the structure is simple, and it is often not taken seriously. However, it has complicated working conditions on the process pipeline, and once there is a problem, everyone is busy. Because of its cumbersomeness, the problem is difficult to find, often it is difficult to please, but also involves system commissioning, system complete, quality adjustment, environmental pollution. So how to extend the service life of the regulating valve, Prevo Technology Department summed up the following points:

First, the method of improving life
1) Extended working method
Let the regulator work as far as possible at the maximum opening, such as 90%. Thus, cavitation, erosion, and the like occur on the head of the spool. As the spool is broken, the flow rate increases, and the corresponding valve is closed again. This is continuously destroyed and gradually closed, so that the entire spool is fully utilized until the root of the spool and the sealing surface are broken and cannot be used. At the same time, the large opening degree of the throttle opening is large, and the erosion is weakened. This allows the valve to work at the intermediate opening degree and the small opening degree to increase the life of the valve by more than one to five times. If a chemical plant adopts this method, the service life of the valve is increased by 2 times.

2) Reduce S to increase the working opening and improve the life method
Decrease S, that is, increase the loss of the system except the regulating valve, so that the pressure drop distributed to the valve is reduced. In order to ensure the flow through the regulating valve, the opening of the regulating valve is inevitably increased, and at the same time, the pressure drop on the valve is reduced, so that Cavitation and erosion are also weakened. The specific methods include: the pressure drop of the orifice plate after the valve is throttled; the manual valve connected in series on the pipeline is closed, and the valve is obtained to obtain a better working opening. This method is very simple, convenient and effective when the valve selection is at a small opening.

3) Reduce the caliber to increase the working opening and improve the life method
Increase the working opening by reducing the diameter of the valve.
The specific methods are:
1 Change a small one-caliber valve, such as DN32 to DN25;
2 The valve body is not changed, and the valve seat of the small seat diameter is replaced. If a chemical plant is overhauled, the throttle dgl0 is replaced with dg8, and the service life is doubled.

4) Transfer damage location to improve life method
Transfer the severely damaged area to a secondary location to protect the sealing and throttling surfaces of the valve seat.

5) Growth throttling channel to improve life method
The simplest way to increase the throttling channel is to thicken the seat to increase the seat bore and create a longer throttling channel. On the one hand, the sudden expansion after the flow-closing type of throttling can be postponed, and the position of the transfer is destroyed to make it away from the sealing surface; on the other hand, the throttling resistance is increased, the degree of recovery of the pressure is reduced, and the steam is reduced. The eclipse weakens. Some design the valve seat hole as a stepped, wave type, in order to increase the resistance and reduce the cavitation. This method is often used when introducing high pressure valves in the installation and retrofitting old valves, and is also very effective.

6) Change the flow direction to improve the life method
The flow-opening type flows toward the opening direction, and the cavitation and erosion mainly act on the sealing surface, so that the sealing surface of the valve core and the valve seat is quickly damaged; the flow-closing type flows toward the closed direction, cavitation and erosion. After throttling, below the seat sealing surface, the sealing surface and the root of the valve plug are protected, extending life. Therefore, when the valve for the flow-open type is used, when the problem of prolonging the life is more prominent, the life can be extended by one to two times by simply changing the flow direction.

7) Use special materials to improve life method
In order to resist cavitation (destruction of shapes such as honeycomb dots) and scouring (streamlined small grooves), special materials resistant to cavitation and erosion can be used to manufacture the throttle. This special material is 6YC-1, A4 steel, stellite, hard alloy and so on. For corrosion resistance, materials that are more resistant to corrosion and have certain mechanical and physical properties can be used. This material is divided into non-metallic materials (such as rubber, PTFE, ceramics, etc.) and metal materials (such as Monel, Hastelloy, etc.).

8) Change the valve structure to improve the life method
The purpose of improving the life is to change the valve structure or to select a valve with a longer life, such as a multi-stage valve, an anti-cavitation valve, a corrosion-resistant valve, and the like.

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