1. Is it easy for oscillation to occur when the dual seat regulating valve is in a small opening working state?

Why can't a double seat regulating valve be used with a small opening? This is determined by its valve seat structure. A double seat regulating valve has two valve cores, with the upper core in the flow open position and the lower core in the flow closed position. When the valve core of the regulating valve is in the flow open position, the stability is relatively good. Therefore, when the valve core of the double seat regulating valve works in a small opening range close to the flow closed state, the valve core will oscillate. Therefore, in the selection of regulating valves, it is necessary to avoid the use of double seat regulating valves in small opening ranges.

2. Can dual seat regulating valves be used as shut-off valves?

The valve core of the 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. However, due to the inability of the two sealing surfaces to make good contact at the same time, the leakage is large and cannot act as a cutoff in the pipeline. Even if sleeve improvements are added to the double seat valve now, it cannot change the limitations caused by its structural design.

3. Comparison of anti blocking performance between straight stroke regulating valve and angle stroke valve?

The valve core of a straight stroke control valve moves vertically, while the fluid moves horizontally. The flow channel structure inside the valve chamber is not straight through, usually in an S-shape, which forms many blind spots. Over time, the medium is prone to settle in these blind spots, which can cause blockages. The valve core of the angle stroke valve is in horizontal rotational motion, and the medium is also in horizontal flow direction, so there is no dead angle, and the sediment is easily carried away by the fluid. Therefore, the anti blocking performance of straight stroke regulating valves is much better than that of angular stroke valves.

4. Why is the stem of the straight stroke regulating 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, which generates significant frictional force. So designing the valve stem to be small and using PTFE packing with a low coefficient of friction are all aimed at minimizing friction as much as possible. But this has resulted in problems such as thin valve stem, easy bending, and short packing life.

5. Is the cut-off pressure difference of angle stroke valves large?

Due to the small torque generated by the combined force of the medium acting on the valve core on the valve shaft, it can withstand a large pressure difference, so the cut-off pressure difference of angular 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, soft sealed valves have much worse wear resistance and reliability than hard sealed valves, so from the dual standards of leakage and reliability, hard sealed shut-off valves are better than soft sealed shut-off valves. Nowadays, many cut-off valves use wear-resistant alloy welding, which greatly improves the sealing performance and is sufficient to meet the requirements of cut-off valves.