In the valve industry, valve knowledge of professionalism and importance has been widely appreciated. Valve model is not the same, each valve has its own unique characteristics, in the selection of valves, not only to consider the parameters of these valves, but also take into account the scope of the valve, media and so on. In addition, the valve in the later maintenance, valve knowledge is a very important part of the following list of the more popular valve knowledge of several practical know-how:

1, why the cut-off valve should try to choose hard seal?

Cut-off valve requirements leakage lower the better, soft seal valve leakage is the lowest, cutting effect of course good, but not wear-resistant, can be poor. From the leakage volume is small, sealed and can be * double standards, soft seal cut off than hard seal cut off good. such as the full function of ultra light control valve, sealed and heap wear-resistant alloy protection, can * high, leakage rate of up to 10-7, has been able to meet the requirements of shut-off valves.

2, why double seal valve can not be used as a cut-off valve?

The advantage of the two-seater valve spool is the force balance structure, allowing the pressure difference to be large, and its outstanding disadvantage is that two sealing faces can not be at the same time good contact, resulting in large leakage. If it is artificially and forcibly used to cut off the occasion, obviously the effect is not good, even if it made a lot of improvements (such as double sealed sleeve valve), it is undesirable.

3, why the two-seater valve small opening of the work is easy to oscillate?

For single core, when the medium is flow open type, the valve stability is good, when the medium is the flow is closed, the valve stability is poor. The two-seater valve has two spool, the bottom spool is in the flow closes, on the valve core is flowing open, thus, in the small opening degree work, the flow closes the spool to be easy to cause the valve the vibration, this is the two-seater valve cannot use in the small opening degree work the reason.

4, what direct stroke control valve plugging performance is poor, the angle travel valve blocking performance good?

Straight Stroke valve spool is vertical throttling, and the medium is horizontal flow into the outflow, the valve cavity flow path must turn to turn, so that the flow of the valve becomes quite complex (shape such as inverted "S" type). In this way, there are many dead zones, which provide a space for the precipitation of the medium, and thus the blockage. Angle travel valve throttle direction is horizontal direction, medium flow into, horizontal outflow, easy to take away the unclean medium, at the same time the flow path is simple, medium precipitation space is also very few, so the angle travel valve prevent plugging performance is good.

5, why the direct stroke control valve stem thinner?

Direct stroke regulating valve it involves a simple mechanical principle: big sliding friction, small rolling rubbing. Straight stroke valve stem up and down movement, filling a little tighter, it will be the stem pack very tight, resulting in a larger return to the difference. To this end, the valve stem design is very small, filler and often small friction coefficient of PTFE filler, in order to reduce the return to the difference, but the problem is to send the stem fine, it is easy to bend, filler life is also short. Solve this problem, the best way is to use the travel valve stem, that is, the angle stroke type of control valve, its stem than the straight stroke stem coarse 2~3 times, and the use of long life of graphite filler, stem stiffness, filler life long, its friction moment is small, back to small.

6. Why is the cutting pressure difference of the angle travel type valve larger?

The angle travel type Valve's cutting pressure difference is big, is because the medium in the valve core or the valve board produces the force to the rotational axis to produce the torque is very small, therefore, it can withstand the big pressure difference.

7, why the sleeve valve instead of single, two-seater valve has not been fulfilled?

The 60 's advent of the sleeve valve, the 70 's in the domestic and foreign large number of use, the 80 imported petrochemical equipment in the ratio of the sleeve valve is larger, at that time, many people think that the sleeve valve can replace single, two-seater valve, become the second generation of products. By now, not so, single seat valves, two-seater valves, sleeve valves are equally used. This is because the sleeve valve is only improved throttling form, stability and maintenance of the single seat valve, but its weight, blocking and leakage indicators with single, two-seater valve consistent, how can it replace the single, two-seater valve? So, it can only be used together.

8, why the use of salt-lined butterfly valve, lining fluorine diaphragm valve service life is short?

The desalting medium contains low concentrations of acids or alkalis, which have a greater corrosive effect on the rubber. The corrosion performance of rubber is swelling, aging, low strength, with the use of rubber lining butterfly valve, diaphragm valve, the effect is poor, its essence is the rubber is not corrosion-resistant. The lining diaphragm valve is improved as a lining fluorine diaphragm valve with good corrosion resistance, but the diaphragm with fluorine diaphragm valve is folded and broken, causing mechanical damage, and the life of the valve is shortened.

Now the best way is to use water treatment special ball valve, it can use to 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 gas source pressure, so that the actuator size than film-type more compact, more thrust, the piston in the O-ring than the film can be *, so its use will be more and more.

10. Why is selection more important than calculation?

In comparison with the model selection, selection is much more important and more complicated. Because the calculation is only a simple formula calculation, it is not the accuracy of the formula, but the given process parameters are accurate. Selection involves more content, a little careless, it will lead to improper selection, not only the creation of the force, material, financial resources, and the use of the effect is not ideal, bringing a number of use problems, such as the * sex, life, operating quality.

Valve knowledge of valve selection, valve maintenance, and so are the focus of each business businesses place, valve knowledge more, more comprehensive, representing the Chinese valve industry step towards specialization of the road closer and nearer.