1. When the double seat regulating valve is in a small opening working state, it is prone to oscillation?

The reason why a double seat regulating valve cannot be used with a small opening is determined by its valve seat structure. The double regulating valve has two valve cores. The upper valve core is in the flow open state, and the lower valve core is in the flow closed state. When the valve core of the regulating valve is in the flow open state, the stability is relatively good. Therefore, when the valve core of the double seat regulating valve is working in a small opening range close to the flow closed state, the valve core will produce vibration. Therefore, in the selection of regulating valves, it is necessary to avoid the use of double seat regulating valves within a small opening range.

2. Can a double seat regulating valve not be used as a shut-off valve?

The valve core of a double seat regulating valve has the advantage of a force balance structure, allowing for a wide range of pressure differences before and after the valve. Due to the inability of the two sealing surfaces to make good contact at the same time, there is a large amount of leakage, which cannot play a cut-off role in the pipeline. Even if a sleeve improvement is added to the double seat valve now, it cannot change the limitations caused by its structural design.

3. Comparison of anti clogging performance between straight stroke control valves and angle stroke valves?

The valve core of a straight stroke regulating valve moves vertically, while the fluid moves horizontally. The flow channel structure in the valve chamber is not a straight through type, usually in an S-shaped shape, which forms many blind spots. Over time, the medium is prone to precipitation in these blind spots, which can easily cause blockage. The valve core of the angle stroke valve is in horizontal rotary motion, and the medium is also in horizontal flow direction, so it is not easy to have dead corners and sediment is easily carried away by the fluid. Therefore, the anti blocking performance of straight stroke regulating valves is much better than that of angle stroke valves.

4. Why is the stem of a straight stroke control valve thinner?

Due to the principle of high sliding friction and low rolling friction. The stem of a straight stroke valve slides up and down, creating significant friction. So designing the valve stem to be small and using PTFE packing with low friction coefficient is to minimize friction as much as possible. However, this has resulted in problems such as thin valve stems being prone to bending and short packing life.

5. Is the cut-off pressure difference of angle stroke valves relatively large?
Due to the combined force generated by the medium acting on the valve core, the torque generated by the valve shaft is very small, so it can withstand a large pressure difference, so the cut-off pressure difference of angle stroke valves is relatively large.

6. Why should hard seals be used as much as possible for shut-off valves?
In terms of cutting effect alone, soft sealed valves perform better than hard sealed valves. However, the wear resistance and reliability of soft sealed valves are much worse than those of hard sealed valves. Therefore, in terms of double standards of leakage and reliability, hard sealed shut-off valves are better than soft sealed shut-off valves. Nowadays, many shut-off valves use wear-resistant alloy for welding, greatly improving sealing performance and meeting the requirements of shut-off valves.