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1. Why is the small opening of the two-seat valve easy to oscillate?

For single core, when the medium is open flow, valve stability is good; When the medium is closed type, the stability of the valve is poor. The two-seat valve has two spool, the lower spool is in the flow closed, the upper spool is in the flow open, so, in the small opening work, the flow closed spool is easy to cause the vibration of the valve, this is the reason why the two-seat valve can not be used for small opening work.

2. Why the double seal valve can not be used as a cut-off valve?

The advantage of the two-seat valve spool is the force balance structure, allowing large pressure difference, and its outstanding disadvantage is that the two sealing surfaces can not be in good contact at the same time, resulting in large leakage. If it is artificial, mandatory for cutting occasions, obviously the effect is not good, even if it has made many improvements (such as double sealing sleeve valve), is not desirable.

3. What straight stroke control valve blocking performance is poor, Angle stroke valve blocking performance is good?

Straight stroke valve spore is vertical throttling, and the medium is horizontal flow into and out of the valve chamber flow channel must turn to turn, so that the valve flow path has become quite complex (shape such as inverted "S" type). In this way, there are many dead zones, providing space for the precipitation of the medium, which, in the long run, causes blockage. Angle stroke valve throttling direction is the horizontal direction, horizontal flow into the medium, horizontal outflow, easy to take away the dirty medium, at the same time the flow path is simple, medium precipitation space is very little, so the Angle stroke valve blocking performance is good.

4. Why straight stroke regulating valve stem is thinner?

It involves a simple mechanical principle: sliding friction is high, rolling friction is low. Straight stroke valve stem up and down movement, packing a little bit tight, it will put the stem package is very tight, resulting in a large return difference. To this end, the stem design is very small, and the packing is often used with small friction coefficient of ptfe packing, in order to reduce the return difference, but the problem is that the stem is thin, easy to bend, and the life of the packing is short. To solve this problem, the best way is to use rotary valve stem, that is, Angle stroke type of regulating valve, its stem than straight stroke stem thick 2 ~ 3 times, and choose long life graphite packing, stem stiffness is good, packing life is long, the friction torque is small, small back.

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

Angle stroke valve cut off the pressure difference is larger, because the media in the spool or valve plate on the resultant torque of the rotating shaft is very small, therefore, it can withstand a larger pressure difference.

6. Why the use of desalination water medium rubber lined butterfly valve, fluorine lined diaphragm valve short life?

The medium of desalinated water contains low concentration of acid or alkali, which has greater corrosion to rubber. The corrosion of rubber is manifested as expansion, aging, low strength, and the use effect of butterfly valve and diaphragm valve lined with rubber is poor, and its essence is caused by rubber corrosion resistance. After the rubber lined diaphragm valve is improved to the fluorine lined diaphragm valve with good corrosion resistance, but the diaphragm of the fluorine lined diaphragm valve is broken by folding up and down, resulting in mechanical damage, and the life of the valve is shortened. Now the best way is water treatment special ball valve, it can be used to 5 ~ 8 years.

7. Why should the cut-off valve be hard sealed as far as possible?

The lower the leakage requirements of the cut-off valve, the better, the leakage of the soft seal valve is the lowest, the cutting effect is of course good, but not wear-resistant, poor reliability. From the double standard of small leakage and reliable sealing, soft sealing is not as good as hard sealing. Such as the full function of the ultra light valve, sealed and piled with wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the requirements of the cut-off valve.

8. Why did the sleeve valve replace the single and double seat valve?

The advent of the sleeve valve in the 1960s, the 1970s in large numbers of domestic and foreign use, the introduction of the petrochemical equipment in the 1980s sleeve valve accounted for a larger proportion, at that time, many people believe that the sleeve valve can replace the single, double seat valve, become the second generation of products. To date, this is not the case, single-seat valves, two-seat valves, sleeve valves are equally used. This is because the sleeve valve is only improved throttling form, stability and maintenance better than the single seat valve, but its weight, blocking and leakage indicators and single, double seat valve, how can it replace the single, double seat valve? Therefore, it can only be used together.

9. Why is selection more important than calculation?

Computation is much more important and complex than selection. Because the calculation is just a simple formula calculation, its itself does not depend on the accuracy of the formula, but on the accuracy of the given process parameters. Selection involves more content, a little careless, it will lead to improper selection, not only cause the waste of human, material and financial resources, but also the use of the effect is not ideal, bringing a number of use problems, such as reliability, life, operation quality and so on.

10. Why are more and more piston actuators used in pneumatic valves?

For pneumatic valves, the piston actuator can make full use of the air source pressure, the size of the actuator is more compact than the film type, the thrust is larger, the o-ring in the piston is more reliable than the film, so its use will be more and more.