1. Is the double-seat control valve prone to oscillation when it is working at a small opening?
Why the double-seat control valve cannot be used with a small opening is determined by its seat structure. The double control valve has two valve cores. The upper valve core is in flow open and the lower valve core is in flow closed. When the valve core of the control valve is in flow open, the stability is better, so when the valve core of the double-seat control valve is close to flow When operating in a small opening range in the closed state, the valve core will vibrate. Therefore, when selecting a regulating valve, we must avoid using the double-seat regulating valve in a small opening range.
2. The double-seat regulating valve cannot be used as a shut-off valve?
The valve core of the double-seat control valve has the advantage of a force-balanced structure, which allows a wide range of pressure differences between the front and rear of the valve. Since the two sealing surfaces cannot make good contact at the same time, the leakage is large and cannot play a role in cutting off the pipeline. , even if the sleeve improvement is now added to the double-seat valve, it cannot change its limitations caused by structural design.
3. Comparison of anti-blocking properties between straight stroke control valves and angle stroke valves?
The valve core of the linear stroke control valve moves vertically, and the fluid moves horizontally. The flow channel structure in the valve cavity is not straight-through, and is generally S-shaped. This deformation creates many blind spots. Over time, the medium is easy to form in these blind spots. Precipitation can easily lead to clogging. The valve core of the quarter-turn valve is in horizontal rotation, and the medium is also in the horizontal flow direction, so there is no dead space easily, and the precipitated matter is easily taken away by the fluid. Therefore, the anti-blocking performance of straight-stroke regulating valves is much better than that of quarter-stroke valves.
4. Why is the valve stem of the straight stroke regulating valve thin?
Due to the principle of large sliding friction and small rolling friction. The valve stem of the straight stroke valve slides up and down, which generates greater friction. Therefore, the valve stem is designed to be small and PTFE packing with a small friction coefficient is used to reduce friction as much as possible. However, this results in problems such as thin valve stem, easy bending, and short packing life.
5. The cut-off pressure difference of the quarter-turn valve is large?
Since the resultant force generated by the medium acting on the valve core exerts very little torque on the valve shaft, it can withstand a large pressure difference, so the cut-off pressure difference of the quarter-turn valve is large.
6. Why should shut-off valves use hard seals as much as possible?
In terms of cutting effect alone, soft seal valves perform better than hard seal 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 volume and reliability, hard-sealed shut-off valves are better than soft-sealed shut-off valves. Nowadays, many shut-off valves use surfacing wear-resistant alloy, which greatly improves the sealing performance and is enough to meet the requirements of shut-off valves.