Often encounter some friends who use fluorine lined valves will consult such and such problems, and then some of the most easily encountered problems will be summarized, defined as the valve ten why, I hope to help you:

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

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

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

The advantage of the two-seat 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 used artificially and forcibly for cutting off occasions, it is obviously not effective, even if many improvements have been made for it (such as double sealed sleeve valve), it is not advisable.

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

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

4.What straight stroke regulating valve blocking performance is poor, Angle stroke valve blocking performance is good?

Straight travel valve spool is vertical throttling, and the medium is horizontal flow into and out, the valve chamber flow channel must turn and reverse, so that the valve flow path becomes quite complex (shape such as inverted "S" type). As a result, there are many dead zones, providing space for the medium to settle and, over time, causing blockage. The direction of the Angle travel valve throttling is the horizontal direction, the medium horizontal flow into, horizontal flow out, easy to take away the unclean medium, at the same time, the flow path is simple, the space of the media precipitation is also very little, so the Angle travel valve blocking performance is good.

5.Why straight travel control valve stem is smaller?

It involves a simple mechanical principle: large sliding friction, small rolling friction. The stem of the straight travel valve moves up and down, and the packing is a little bit tighter. It will wrap the stem tightly and produce a larger return difference. For this reason, the valve stem is designed to be very small, and the packing is commonly used with small friction coefficient of tetrafluoroidal packing, in order to reduce the return error, but the problem is that the valve stem is small, it is easy to bend, and the packing life is short. To solve this problem, the best way is to use the rotary valve stem, that is, the regulating valve of the Angle stroke class, its stem is 2 ~ 3 times thicker than the straight stroke valve stem, and the selection of long life graphite packing, valve stem stiffness, packing life is long, the friction torque is small, small back difference.

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

The cut off pressure difference of angular stroke valve is large, because the resultant force generated by the medium on the spool or valve plate produces a very small torque on the rotating shaft, so it can withstand a large pressure difference.

7.Why did sleeve valves replace single and double seat valves not work?

Sleeve valves came out in the 1960s, and were widely used at home and abroad in the 1970s. In the petrochemical devices introduced in the 1980s, sleeve valves accounted for a larger proportion. At that time, many people believed that sleeve valves could replace single and two-seat valves and become the second generation of products. Until now, this is not the case, single seat valve, two seat valve, sleeve valve are equally used. This is because the sleeve valve is just improved throttling form, stability and maintenance is better than the single seat valve, but its weight, plugging and leakage indicators are consistent with the single and two seat valve, how can it replace the single and two seat valve? Therefore, it can only be shared.

8.Why is the service life of the rubber lined butterfly valve and fluorine lined diaphragm valve short for desalting water medium?

The desalted water medium contains low concentration of acid or alkali, which is more corrosive to rubber. The corrosion of rubber is characterized by expansion, aging and low strength. The use effect of butterfly valve and diaphragm valve lined with rubber is poor. The essence is that rubber is not corrosion resistant. After the rubber lined diaphragm valve is improved into a fluorine lined diaphragm valve with good corrosion resistance, but the diaphragm of the fluorine lined diaphragm valve can not withstand up and down folding and is broken, resulting in mechanical damage, and the life of the valve is shortened. Now the best way is to treat the special ball valve with water, it can be used for 5 ~ 8 years.

9.Why is the piston actuator used more and more in the pneumatic valve?

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

10.Why is selection more important than calculation?

Compared with calculation, selection is much more important and complex. Because the calculation is just a simple formula calculation, its itself does not lie in the accuracy of the formula, but in the accuracy of the given process parameters. The selection involves more content, slightly careless, will lead to improper selection, not only cause the waste of manpower, material resources, financial resources, and the use effect is not ideal, bring a number of use problems, such as reliability, life, operation quality, etc.

Summary: The above are the top ten valves. The information is summarized according to my years of experience in fluorine lined ball valve production, for reference only.