First, why does the linear stroke control valve have poor anti-blocking performance, while the angle stroke valve has good anti-blocking performance?
Anyone who has a need for electric double-seat control valves will know that there are actually many types of electric double-seat control valves, and their applicable ranges are different according to different performances. The spool of the straight-stroke valve is a vertical throttling, while the medium is horizontal When flowing in and out, the flow path in the valve cavity must turn and reverse, making the flow path of the valve quite complicated (the shape is like an inverted "S" shape). In this way, there are many dead zones, which provide space for the precipitation of the medium, which in the long run will cause blockage. The throttling direction of the quarter-turn valve is the horizontal direction. The medium flows in horizontally and flows out horizontally, which can easily take away the dirty medium. At the same time, the flow path is simple and there is little space for the medium to settle, so the quarter-turn valve has good anti-blocking performance.
Second, why is the double-seat valve prone to oscillation when operating at a small opening?
For a single core, when the medium is flow-open, the valve has good stability; when the medium is flow-closed, the valve has poor stability. The double-seat valve has two valve cores. The lower valve core is in flow-closed state and the upper valve core is in flow-open state. In this way, when working at a small opening, the flow-closed valve core can easily cause valve vibration. This is the electric double-seat valve. The reason why the regulating valve cannot be used for small opening work.
Third, why is the valve stem of the linear stroke regulating valve thinner?
It involves a simple mechanical principle: large sliding friction and small rolling friction. The valve stem of a straight stroke valve moves up and down. If the packing is pressed a little tighter, it will wrap the valve stem very tightly, resulting in a large hysteresis. To this end, the valve stem is designed to be very small, and the packing often uses PTFE packing with a small friction coefficient in order to reduce the hysteresis. However, the problem derived from this is that a thin valve stem is easy to bend, and the packing life is also short. To solve this problem, the best way is to use a rotary valve stem, that is, a rotary stroke regulating valve. Its valve stem is 2 to 3 times thicker than a straight stroke valve stem, and it uses graphite filler with long life and high valve stem stiffness. Good, the filler has a long life, its friction torque is small, and the hysteresis is small. In other words, we are still very knowledgeable when choosing electric two-seat control valves!
Fourth, why is the cut-off pressure difference of the quarter-turn valve so large?
The cut-off pressure difference of the quarter-turn valve is large because the resultant force generated by the medium on the valve core or valve plate exerts a very small torque on the rotating shaft. Therefore, it can withstand a large pressure difference. .
Fifth, why can’t the double seal valve be used as a shut-off valve?
In fact, the advantage of the electric double-seat control valve core is that it has a force-balanced structure that allows a large pressure difference. However, its outstanding disadvantage is that the two sealing surfaces cannot make good contact at the same time, causing large leakage. If it is used artificially and compulsorily in cutting-off situations, the effect will obviously not be good. Even if many improvements are made to it (such as double sealing sleeve valve), it is not advisable.