Valve manufacturer: Tell you a few common sense questions about the valve!

1. Why is the two-seat valve easy to oscillate when working with small opening?

For single core, when the medium is open flow type, the valve stability is good; When the medium is closed, the stability of the valve is poor. The two-seat valve has two spool, the lower spool is closed, and the upper spool is open. In this way, when the small opening is working, the flow valve core is likely to cause vibration of the valve, which is the reason why the two-seat valve cannot be used for small opening work.

2. Why can't double seal valves be used as shut-off valves?

The advantage of the two-seat spool is the force balance structure, which allows a large pressure difference, but its significant disadvantage is that the two sealing surfaces can not be in good contact at the same time, resulting in a large leak. If it is used artificially and forcibly for cutting occasions, the effect is obviously not good, even if many improvements are made to it (such as double seal sleeve valves), it is not recommended.

3. Which direct stroke control valve has poor anti-blocking performance, while the angular stroke valve has good anti-blocking performance?

The straight stroke spool is throttled vertically, the medium flows in and out horizontally, and the flow path in the valve chamber inevitably turns, which makes the flow path of the valve quite complicated (shaped like an inverted "S" type). In this way, there are many dead zones, which provide space for the precipitation of the medium, and if this goes on for a long time, it will cause blockage. The direction of the angular stroke valve throttling is the horizontal direction, the medium flows horizontally into and out horizontally, it is easy to take away the unclean medium, and the flow path is simple, and the space for the medium to precipitate is also very little, so the angular stroke valve has good anti-blocking performance.

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

It involves simple mechanical principles: high sliding friction and low rolling friction. The stem of the straight stroke valve moves up and down, and the packing is slightly compressed, which will make the stem seal very tightly, resulting in a large return difference. Therefore, the valve stem is designed to be very small, and the packing is commonly used with a small friction coefficient of tetrafluoroidal packing in order to reduce the return error, but the problem is that the valve stem is very thin, easy to bend and the packing life is short. The best way to solve this problem is to use the rotary valve stem, that is, the regulating valve of the Angle stroke class, its valve stem is 2 to 3 times thicker than the straight stroke valve stem, and the use of long life graphite filler, the valve stem stiffness is good, the packing life is long, and the friction torque is small and the return difference is small.

5. Why is the cut off pressure difference of Angle stroke valve large?

Because the resultant force generated by the medium on the spool or valve plate produces a small torque on the rotating shaft, the cutoff pressure difference of the angular stroke valve is large. It can withstand a large pressure difference.

6. Why use a hard seal on the stop valve whenever possible?

The leakage of the stop valve is as small as possible. The leakage of the soft seal valve is very low. Of course, the cutting effect is good, but it is not wear-resistant and poor reliability. From the double standard of small leaks and reliable seals, soft seals are not as good as hard seals. For example, the full-function ultra-light regulating valve, sealed, stacked, using wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the requirements of the cut-off valve.