Case
Case
Regulating valves play a very important role in the automatic control of modern factories whose production depends on the correct distribution and control of the flowing medium. Whether these controls are energy exchange, pressure reduction, or simple container filling, some final control elements are required to complete.
(1) The method of extending life by working with a large opening
Let 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 spool is damaged and the flow rate increases, the corresponding valve will be closed a little more. This will continue to destroy and gradually close so that the entire spool can be fully utilized until the root of the spool and the sealing surface are damaged and cannot be used.
At the same time, the throttling gap is large when the large opening works and the erosion is weakened, which improves the service life by more than 1 to 5 times than letting the valve work at the middle opening and small opening at the beginning. If a chemical plant adopts this method, the valve's service life has been increased by 2 times.
(2) Decrease S and increase working opening to improve service life method
Decrease S means 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, so that Cavitation and erosion are also weakened. The specific methods are: set orifice plate behind the valve to throttle the consumption of pressure drop; close the manual valve connected in series on the pipeline until the regulating valve obtains an ideal working opening. Using this method is very simple, convenient, and effective when the valve is selected to work with a large opening at the beginning.
(3) Reduce the caliber and increase the working opening to improve the service life method
Increase the working opening by reducing the diameter of the valve
Change a valve with a smaller diameter, such as DN32 to DN25; For example, when a chemical plant is overhauled, the throttling part dgl0 is replaced with dg8, doubling the service life.
(4) The method of transferring the damaged position to improve the lifespan
Shift the severely damaged place to a secondary position to protect the sealing surface and throttle surface of the valve core and seat.
(5) The method of increasing the throttling channel to improve the life
The easiest way to increase the throttle channel is to thicken the valve seat to increase the seat hole and form a longer throttle channel.
On the one hand, it can delay the sudden expansion after the flow-closed throttling, shift the damage position, and keep it away from the sealing surface; Eclipse weakens. Some design the valve seat hole into a stepped or wavy shape just to increase resistance and weaken cavitation. This method is often used on the high-pressure valve in the introduction device, and when the old valve is improved, it is also very effective.
(6) Change the flow direction and improve the lifespan method
The flow-open type flows toward the opening direction, and cavitation and erosion mainly act on the sealing surface, causing the root of the valve core and the sealing surface of the valve seat to be quickly damaged; the flow-closed type flows toward the closing direction, and the cavitation and erosion effects After throttling, the sealing surface of the valve seat is below the sealing surface, which protects the sealing surface and the root of the valve core and prolongs the service life.
For the valve used as a flow-open type, when the problem of extending the life is more serious, the life can be extended by 1 to 2 times only by changing the flow direction.
(7) Use special materials to improve life expectancy
In order to resist cavitation (destructive shapes such as honeycomb dots) and erosion (streamlined small grooves), special materials that are resistant to cavitation and erosion can be used to make throttling parts. Such special materials include 6YC-1, A4 steel, stellite, hard alloy, etc.
In order 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 metal materials (such as Monel, Hastelloy, etc.).
(8) Change the valve structure to improve the service life method
Adopt the method of changing the valve structure or choosing a valve with longer life to improve the life, such as choosing a multi-stage valve, anti-cavitation valve, corrosion-resistant valve, etc.
