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Common problems in valve use
First, the regulator valve Why can not double seal valve used as a shut-off valve?
The advantage of the double seat valve spool is that the force balance structure allows a large pressure difference, and its outstanding disadvantage is that the two sealing surfaces cannot be in good contact at the same time, 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 has made many improvements (such as double sealed sleeve valve), it is also not desirable.
Second, the regulator valve Why does the double seat valve easily oscillate when working at a small opening?
For a single core, when the medium is a flow-open type, the valve has good stability; when the medium is a flow-closed type, the stability of the valve is poor. The double seat valve has two valve cores, the lower valve core is closed, and the upper valve core is open. This way, when the valve is operated at a small opening, the flow-closed valve core can easily cause the vibration of the valve. This is the double seat valve. The reason why it cannot be used for small opening work.
Third, what is the direct stroke control valve anti-blocking performance is poor, anti-blocking angle valve is good?
Straight stroke valve spool is vertical throttling, and the medium is the horizontal flow in and out, the flow path in the valve cavity will inevitably turn and turn, so that the flow path of the valve becomes quite complex (shaped inverted S-shape). In this way, there are many dead zones, which provide space for the sedimentation of the media and, over time, cause blockages. The throttle valve throttle direction is the horizontal direction, the media flow into the horizontal outflow, easy to take away the dirty media, while the flow path is simple, the medium precipitation space is also very little, so the angle valve anti-blocking performance is good.
Fourth, why angular pressure difference between the angle stroke valve?
The cut-off pressure difference of the angular stroke valve is larger because the resultant force generated by the medium on the valve plug or the valve plate generates a very small torque on the rotating shaft, so that it can withstand a large pressure difference.
V. Why is the straight stroke valve stem smaller?
It involves a simple mechanical principle: large sliding friction and low rolling friction. The valve stem of the linear valve moves up and down, and the packing is pressed slightly. It will pack the valve stem tightly and generate a large return difference. For this reason, the valve stem is designed to be very small, and the filler is often a PTFE filler with a small friction coefficient in order to reduce the return difference, but the problem is that the valve stem is thin, it is easy to bend, and the filler life is short. To solve this problem, the best way is to use the trip valve stem, which is a quarter-rotor type control valve, its stem is 2 to 3 times thicker than the straight stroke stem, and the use of long-life graphite filler, stem rigidity Well, long filler life, the friction torque is small, the difference is small.
6. Why does the service life of the lined plastic butterfly valve and fluorine-lined diaphragm valve is short due to the desalinated medium?
Demineralized water contains low concentrations of acids or bases that are highly corrosive to rubber. Corrosion of rubber is manifested as swelling, aging, and low strength. The use of plastic-lined butterfly valves and diaphragm valves are all poor in their effect. The reason is that rubber is not resistant to corrosion. The rear rubber-lined diaphragm valve was improved to be a fluorine-lined diaphragm valve with good corrosion resistance, but the diaphragm of the fluorine-lined diaphragm valve could not stand up and down and was broken, causing mechanical damage and shortening the life of the valve. The best way now is to treat the special ball valve with water. It can be used for 5 to 8 years.
Seven, why cut off the valve should try to use a hard seal?
The cut-off valve requires a lower leakage, the better, and the leakage of the soft-seal valve is the lowest. The cut-off effect is certainly good, but it is not wear-resistant and has poor reliability. From the double standards of small leaks, sealing and reliability, soft seal cutting is not as good as hard seal cutting. Such as full-featured ultra-light control valve, sealed and piled with wear-resistant alloy protection, high reliability, leakage rate of 10 to 7, has been able to meet the requirements of the shut-off valve.
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