1. Is it easy to oscillate when the double-seat regulating valve is in a small opening working state?

       The reason why the double-seat regulating valve cannot be used with a small opening is determined by its seat structure. The double regulating valve has two spools, the upper spool is in the flow-open state, and the lower spool is in the flow-closed state. When the spool of the regulating valve is in the flow-open state, the stability is relatively good. When working in the small opening range of the closed state, the spool will vibrate. Therefore, in the selection of the control valve, it is necessary to avoid the use of the double-seat control valve in the small opening range.

2. Can the double-seat regulating valve be used as a cut-off valve?

      The spool of the double-seat control valve has the advantage of a force balance structure, which allows a wide range of pressure difference between the front of the valve and the back of the valve. Since the two sealing surfaces cannot be in good contact at the same time, the leakage is large and cannot be used to cut off the pipeline. , even if the sleeve improvement is added to the double-seat valve now, it cannot change its limitations caused by structural design.

3. What is the anti-blocking performance comparison between the straight-stroke control valve and the quarter-stroke valve?

      The spool of the straight-stroke control valve moves vertically, and the fluid moves horizontally. The flow channel structure in the valve cavity is not straight-through, generally in an S-shape, which deforms into many blind areas. Over time, the medium is easy to form in these blind areas. Precipitation can easily cause clogging. The spool of the quarter-turn valve is in the horizontal rotation movement, and the medium is also in the horizontal flow direction, so there is no dead angle, and the sediment is easily taken away by the fluid. Therefore, the anti-blocking performance of the straight stroke regulating valve is much better than that of the quarter stroke valve.

4. The reason why the stem of the straight stroke control valve is 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 produces a large friction force. Therefore, the valve stem is designed to be small and the PTFE packing with a small friction coefficient is used to reduce the friction as much as possible. However, there are problems such as thin valve stem, easy to bend, and short packing life.

5. Is the cut-off pressure difference of quarter-turn valves large?

      Because the resultant force generated by the medium acting on the valve core produces a very small torque on the valve shaft, it can withstand a large pressure difference, so the quarter-turn valve has a large cut-off pressure difference.

6. Why should the cut-off valve be hard-sealed as much as possible?

      Only in terms of cutting effect, the performance of soft sealing valve is better than that of hard sealing valve. However, the wear resistance and reliability of soft-sealed valves are much worse than those of hard-sealed valves. Therefore, in terms of leakage and reliability, hard-sealed shut-off valves are better than soft-sealed shut-off valves. Now many cut-off valves use surfacing wear-resistant alloys, which greatly improves the sealing performance and is sufficient to meet the requirements of cut-off valves.