Valve use FAQ2016-11-15
1, why double seat valve small opening work easy to oscillate?
For single-core, when the medium is open-type, the valve stability is good; when the medium is closed, the valve stability is poor. Double seat valve has two spool, the lower spool in the flow closed, the spool in the flow open, so that in the small opening work, the flow closure of the valve core is easy to cause the valve vibration, which is double seat valve Can not be used for small opening work of the reasons.
2, why double seal valve can not be used as a shut-off valve?
The advantage of the two-seat valve spool is the force balance structure, which allows the pressure difference to be large, and its outstanding drawback is that the two sealing surfaces can not be in good contact at the same time, causing a large leak. It is not advisable to make a lot of improvements (such as double-seal sleeves) if it is artificially and forcefully used for cutting applications.
3, what straight trip valve anti-blocking performance is poor, angular travel valve anti-blocking performance is good?
Straight stroke valve spool is a vertical throttling, and the media is horizontal into and out of the flow, the valve cavity flow channel must turn down the turn, so that the valve flow becomes quite complex (shape such as inverted "S" type). In this way, there are many dead zones that provide space for the precipitation of the medium, which in the past causes clogging. Angle travel valve throttling direction is the horizontal direction, the media level into the horizontal outflow, easy to clean the media away, while the flow of simple, medium precipitation space is also very small, so the angle of the valve anti-blocking performance.
4, why straight stroke valve stem finer?
It involves a simple mechanical principle: sliding friction is large, rolling friction is small. Straight stroke valve stem up and down movement, packing slightly pressed a little, it will be very tight valve stem, resulting in a larger hysteresis. To this end, the stem is designed to be very small, the filler is often a small friction coefficient of PTFE filler, in order to reduce the hysteresis, but the problem is sent stem fine, easy to bend, filler life is short. To solve this problem, the best way is to use the travel valve stem, that is, the angle of the class of control valve, and its stem stem straight stroke than 2 to 3 times, and the choice of long life graphite packing, stem stiffness Well, the filler life is long, the friction torque is small, the hysteresis is small.
5, why the angle of the valve class cut off the larger pressure?
The angular pressure of the angle travel valve is large because the resultant force on the spool or valve plate is very small for the rotating shaft, so it can withstand a large pressure difference.
6, why desalination water medium using lined butterfly valve, lined diaphragm valve short service life?
Desalted water medium contains low concentrations of acid or alkali, they are more corrosive to rubber. Rubber corrosion is manifested as expansion, aging, low strength, with rubber lined butterfly valve, diaphragm effect is poor, the essence is the rubber is not resistant to corrosion caused. Back rubber diaphragm valve improved corrosion resistance for the good performance of the fluorine diaphragm valve, but the lining of the diaphragm diaphragm can not withstand the folding up and down and was broken, resulting in mechanical damage, the valve life shorter. Now the best way is to use water treatment dedicated ball valve, it can be used to 5 to 8 years.
For single-core, when the medium is open-type, the valve stability is good; when the medium is closed, the valve stability is poor. Double seat valve has two spool, the lower spool in the flow closed, the spool in the flow open, so that in the small opening work, the flow closure of the valve core is easy to cause the valve vibration, which is double seat valve Can not be used for small opening work of the reasons.
2, why double seal valve can not be used as a shut-off valve?
The advantage of the two-seat valve spool is the force balance structure, which allows the pressure difference to be large, and its outstanding drawback is that the two sealing surfaces can not be in good contact at the same time, causing a large leak. It is not advisable to make a lot of improvements (such as double-seal sleeves) if it is artificially and forcefully used for cutting applications.
3, what straight trip valve anti-blocking performance is poor, angular travel valve anti-blocking performance is good?
Straight stroke valve spool is a vertical throttling, and the media is horizontal into and out of the flow, the valve cavity flow channel must turn down the turn, so that the valve flow becomes quite complex (shape such as inverted "S" type). In this way, there are many dead zones that provide space for the precipitation of the medium, which in the past causes clogging. Angle travel valve throttling direction is the horizontal direction, the media level into the horizontal outflow, easy to clean the media away, while the flow of simple, medium precipitation space is also very small, so the angle of the valve anti-blocking performance.
4, why straight stroke valve stem finer?
It involves a simple mechanical principle: sliding friction is large, rolling friction is small. Straight stroke valve stem up and down movement, packing slightly pressed a little, it will be very tight valve stem, resulting in a larger hysteresis. To this end, the stem is designed to be very small, the filler is often a small friction coefficient of PTFE filler, in order to reduce the hysteresis, but the problem is sent stem fine, easy to bend, filler life is short. To solve this problem, the best way is to use the travel valve stem, that is, the angle of the class of control valve, and its stem stem straight stroke than 2 to 3 times, and the choice of long life graphite packing, stem stiffness Well, the filler life is long, the friction torque is small, the hysteresis is small.
5, why the angle of the valve class cut off the larger pressure?
The angular pressure of the angle travel valve is large because the resultant force on the spool or valve plate is very small for the rotating shaft, so it can withstand a large pressure difference.
6, why desalination water medium using lined butterfly valve, lined diaphragm valve short service life?
Desalted water medium contains low concentrations of acid or alkali, they are more corrosive to rubber. Rubber corrosion is manifested as expansion, aging, low strength, with rubber lined butterfly valve, diaphragm effect is poor, the essence is the rubber is not resistant to corrosion caused. Back rubber diaphragm valve improved corrosion resistance for the good performance of the fluorine diaphragm valve, but the lining of the diaphragm diaphragm can not withstand the folding up and down and was broken, resulting in mechanical damage, the valve life shorter. Now the best way is to use water treatment dedicated ball valve, it can be used to 5 to 8 years.
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