Notes on common problems with imported electric control valves
Notes on common problems with imported electric control valves
The imported electric control valve is a control system consisting of intelligent electric actuators and valves. By receiving signals from the industrial automation control system (eg 4~20mA ), the valve is driven to change the cross-sectional area between the valve core and the valve seat. Process parameters such as flow, temperature, and pressure of the medium. Implement automatic adjustment functions. The world's famous imported electric control valve brands mainly include American Shield VTON and American Fisher FISHER.
With the automation industry more and more, the United States Granville Shield VTON of imported electric control valve is being more and more applications. And pneumatic control in various areas of industrial production around the world has significant advantages compared to valves : Electric control valve energy saving (only consumes electricity when working), environmental protection (no carbon emission), quick and easy installation (no complicated pneumatic piping and air pump workstation) .
The technical engineer of VTU VTON in the United States will come to explain some common problems of imported electric control valves .
1. The double seal valve of the electric control valve cannot be used as the shut-off valve
The advantage of the double seat valve spool is the force balance structure, which allows a large pressure difference, and its outstanding disadvantage is that the two sealing surfaces cannot be in good contact at the same time, resulting in a large leak . If it is artificially used forcibly, it is used for cutting off, Obviously the effect is not good, even if it has made many improvements (such as double sealed sleeve valve), it is not advisable .
2 , the shut-off valve of the electric control valve should be as hard as possible
The shut-off valve requires the lower the leakage, the better, the leakage of the soft-sealed valve is the lowest, the cutting effect is of course good, but it is not wear-resistant . The reliability is poor . From the double standard of leakage and sealing, the soft seal is cut off. It is better to cut off the hard seal . For example, the full-function ultra-light regulating valve is sealed and protected by wear-resistant alloy. The reliability is high and the leakage rate is 10-7 , which can meet the requirements of the shut-off valve .
4. Straight-stroke imported electric control valve has poor anti-blocking performance, anti-blocking performance of angular stroke electric control valve
Linear vertical stroke of the throttling valve spool, while the medium is the level of flow into the outflow valve cavity flow must turn back street, so that the valve flow path becomes quite complex (shaped like an inverted "S" type). Thus, the presence of Many dead zones provide space for the precipitation of the medium. In the long run, the blockage is caused . The direction of the throttle of the electric control valve of the angular stroke is the horizontal direction. The medium flows horizontally and horizontally, which makes it easy to take away the dirty medium and the flow path. Simple, the space for media precipitation is also very small, so the angular stroke valve has good anti-blocking performance .
5. The angular stroke electric control valve has a large cutting pressure difference
The cut-off pressure difference of the angular stroke type valve is large because the resultant force of the medium on the valve core or the valve plate produces a very small torque to the rotating shaft, so that it can withstand a large pressure difference .
6 , double seat valve inlet electric control valve is easy to oscillate when working at small opening
For a single core, the valve stability is good when the medium is flow-opening; the stability of the valve is poor when the medium is flow-closed . The double seat valve has two spools, the lower spool is closed, the upper valve The core is flowing, so that when the valve is operated at a small opening degree, the flow-closed spool is likely to cause vibration of the valve, which is why the double seat valve cannot be used for small opening work .
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