First, why the double sealing valve can not be used as a check valve?

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

Two, regulating valve why two – seat valve small opening work when easy to oscillate?

For a single core, when the medium is flow open type, valve stability is good; When the medium is flow 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 that when the small opening is working, the flow closed spool is easy to cause the vibration of the valve, which is the reason why the two-seat valve can not be used for the small opening work.

Three, what straight stroke control valve blocking performance is poor, Angle stroke valve blocking performance is good?

Straight stroke valve spool is vertical throttling, and the medium is horizontal flow into and out, the flow channel in the valve chamber must turn down, so that the valve flow path becomes quite complex (shape such as inverted S type). In this way, there are many dead zones, providing space for the medium to precipitate, and in the long run, causing blockage. Angle stroke valve throttling direction is the horizontal direction, horizontal flow into the medium, horizontal outflow, easy to take away the unclean medium, at the same time the flow path is simple, medium precipitation space is very few, so the Angle stroke valve blocking performance is good.

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

Angle stroke valve cut off the pressure difference is larger, because the medium in the valve core or valve plate produced by the resultant force on the rotation of the shaft torque is very small, therefore, it can withstand a large pressure difference.

Five, why the straight stroke regulating valve stem is thin?

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

Six, why the desalted water medium use rubber lined butterfly valve, fluorine lined diaphragm valve service life is short?

The desalted water medium contains low concentration of acid or alkali, which is highly corrosive to rubber. Rubber is corroded for expansion, aging, low strength, with rubber lining butterfly valve, diaphragm valve use effect is poor its essence is the rubber corrosion resistance. After the rubber lining diaphragm valve is improved as a good corrosion resistance fluorine lining diaphragm valve, but the diaphragm of fluorine lining diaphragm valve can not withstand the upper and lower folding and is broken, resulting in mechanical damage, the life of the valve is shorter. Now the best way is water treatment special ball valve, it can be used to 5 ~ 8 years.

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

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