Ten small problems common in the use of valves

1, why is a small two seater valve opening is easy oscillation work?
For a single core, the stability of the valve is good when the medium is open, and when the medium is closed, the stability of the valve is poor. Two spool valve seat, flow under the valve is closed, the valve is open flow, so that a small opening in the work, the flow of closed type spool valve is easy to cause the valve vibration, which is two seat valve can not work for small opening reason.

2. Why can not the double seal valve be used as a shut-off valve?
The advantage of the double seat valve spool is the force balance structure, which allows large differential pressure, and its prominent drawback is that the two sealing surfaces cannot be well contacted at the same time, resulting in large leakage. If it is artificially and compulsively applied to the occasion of cutting off, the effect is not obvious. Even though many improvements have been made for it, such as double seal sleeve valve, it is not advisable.

3. What is the poor anti blocking performance of the direct stroke regulating valve and the good anti blocking performance of the angle stroke valve?
The straight throttle valve core is vertical throttling, while the medium is horizontal flow into the outflow. The flow path of the valve chamber is bound to turn and reverse, which makes the flow path of the valve quite complex (shape, such as inverted "S"). In this way, there are many dead zones, which provide space for the precipitation of the medium. In the long run, it causes blockage. Hongfeng found the direction of the rotary throttle valve is the horizontal direction, flowing into the medium level, the level of outflow, easy to medium is not clean away, and flow path is simple, medium precipitation little space, so the rotary valve attempts to prevent the performance is good.

4, why is the straight stroke valve stem smaller?
It involves a simple mechanical principle: large sliding friction and small rolling friction. The stem of the direct stroke valve moves up and down, and the packing is pressed a little bit. It will wrap the stem very tightly and produce a larger return. For this reason, the stem design is very small, and fillers are commonly used for tetrafluoroethylene packing with small friction coefficient, so as to reduce the return difference, but the problem is that the valve stem is thin and easy to bend, and the service life of the packing is also short. To solve this problem, the best way is to use the valve of the travel valve, that is, the angular stroke control valve. The stem is 2~3 times longer than the straight stroke valve stem, and the graphite filler with long life is used, the stem stiffness is good, the filler life is long, the friction torque is smaller and the return time is smaller.

5, why the angle stroke type valve cut off the pressure difference is big?
The cutting pressure difference of the angular stroke valve is large, because the torque produced by the resultant force of the medium on the spool or valve plate is very small for the rotating shaft, so it can withstand large differential pressure.

6, why does the desalting medium use the lining glue butterfly valve and the fluorine diaphragm valve short life?
The desalting 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. Rubber and butterfly valves and diaphragm valves are not used properly. The essence of rubber is rubber intolerance to corrosion. Hongfeng valve that after the rubber lined diaphragm valve fluorine diaphragm for improved corrosion resistance, but the fluorine diaphragm diaphragm and stand folds up and down were broken off, resulting in mechanical damage, the valve life is short.
The best way to do it now is to use a special ball valve with water, which can be used for 5~8 years.

7, why should a hard seal be chosen as far as the valve is cut off?
The shut-off valve requires the lower the better the leakage, the leakage of the soft seal valve is the lowest, and the cutting effect is certainly good, but it is not wearable and poor in reliability. From the double standard of small leakage and sealing and reliability, the soft seal cut off is better than the hard seal. Such as full function ultra light control valve, sealed and pile with wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the requirements of the shut-off valve.

8, why does the sleeve valve replace the single and the double seat valve without the wish?
The sleeve valves, which came out in 60s, are widely used at home and abroad in 70s. The proportion of sleeve valves in petrochemical plants introduced in 80s is larger. At that time, many people thought that sleeve valves could replace single or double seat valves and become the second generation products. To the present, it is not the same, single seat valve, double seat valve, sleeve valve have been used equally. Hongfeng think this is because the valve sleeve valve is throttling the form of improved stability and maintenance of the single seat valve, but it is weight, anti clogging and leakage targets with single, double seat valve line, how can it replace the single seat valve? So, it can only be used together.

9. Why is lectotype more important than calculation?
In comparison with the selection of calculation and selection, the selection is much more important and more complicated. Because the calculation is only a simple formula, it does not in itself lies in the accuracy of the formula, but in the accuracy of the given process parameters. Selection involves more contents, and a little carelessness will lead to improper selection. It will not only cause waste of manpower, material resources and financial resources, but also the effect is not ideal. It will bring some problems of use, such as reliability, life and operation quality.