FAQ For Use the valve 03 Sep, 2020

1, Why easy oscillation valve seat small opening?


For single-core, when the medium is a stream-open, the valve stability; flow when the medium is closed, the stability of the valve poor. There are two spool valve seat under the spool in the flow closed, the valve is open flow, so that when the small opening, the flow of closed type valve spool is easy to cause vibration, which is the seat valve the reason can not be used where small opening.


  2, why the double sealing valve as a shut-off valve can not use?


Advantages seat valve spool force equilibrium structure, allowing the pressure big, but it highlights the shortcomings of the two sealing surfaces can not be a good contact, causing a large leak. If it artificially, mandatory for cutting off occasion, obviously not good, even if it made a lot of improvements (such as double sealing sleeve valve), is also undesirable.


  3, what is the difference between a straight stroke adjustment valve attempts to prevent performance, attempts to prevent the rotary valve performance?


Straight trip throttle valve spool is vertical, while the medium is the horizontal flow into the outflow valve cavity flow must turn down the street, so that the valve flow path becomes quite complex (shaped like inverted "S" type). Thus, there are many dead, for precipitating medium provides a space for the long run, causing blockage. Rotary valve throttling direction is the horizontal direction, the medium level of flow into the level of outflow, easy to clean and does not take away the media, while the flow path is simple, medium precipitation space so few attempts to prevent the rotary valve performance.


  4, Why straight trip valve stem smaller?


It involves a simple mechanical principle: sliding friction, small rolling friction. Linear actuator valve stem up and down movement, the packing slightly compressed that it will stem a very tight package, resulting in a greater backlash. To this end, the stem designed to be very small, another commonly used filler friction coefficient of PTFE packing, in order to reduce hysteresis, but the resulting problem is to send small stem, is easy to bend, packing too short life. To solve this problem, the best way is to turn the valve stem with a tour that rotary type valve, which stem two to three times thicker than the straight stroke stem, and use long life graphite packing, stem stiffness well, filling long life, but little friction torque, hysteresis is small.


  5, why cut rotary type valve pressure greater?


Large rotary type valve off the pressure, because the force media in the spool or valve on a board on the shaft torque produced is very small, so it can withstand greater pressure.


  6 Why use desalinated water medium rubber lined butterfly valves, lined diaphragm short life?


Desalting the aqueous medium containing a low concentration of acid or base, they have a greater resistance to rubber. Rubber corrosion performance of expansion, aging, low intensity, with rubber lined butterfly valve, diaphragm use effects are poor, its essence is rubber impatience caused corrosion. After the rubber lined diaphragm for improved corrosion resistance good lined diaphragm, but lined diaphragm membrane folds down and stand up to be broken off, resulting in mechanical damage, shorter valve life. Now the best way to deal with specific water valve, which can be used to 5 to 8 years.


  7 Why use a hard shut-off valve should be sealed?


Shut-off valve leakage requirements as low as possible, the soft sealing valve leakage is the lowest cut off the effect is good, but do not wear, poor reliability. From leakage and small, sealed and reliable double standards, as hard soft sealing off sealing off well. Such as full-featured ultra-light valve, sealing the reactor with wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the requirements of shut-off valve.


  8 Why sleeve valve instead of a single, two-seat valve has not happened?


1960s, the advent of the sleeve valve, 70s heavy use at home and abroad, the larger the 1980s introduced petrochemical plants in the sleeve valve accounting ratios, then, a lot of people think that the sleeve valve can be replaced by a single, double seat valve , to become the second-generation products. Now, is not the case, single-seat valves, seat valves, sleeve valves have been the same use. This is because only improved throttle valve sleeve form, stability and safeguard the single seat valve, but its weight, and attempts to prevent leakage indicators consistent with single, double seat valves, how can it replace single, double seat valves it? Therefore, it can only common use.


  9, why selection is more important than computing?


Calculation and selection of comparison, the selection is much more important, much more complex. Because the calculation is a simple formula, which in itself is not the accuracy of the formula, but rather the given parameters is accurate. Selection related to the content, a little careless, would lead to improper selection, not only wasteful of human, material and financial resources, and the use of the effect is not ideal, bringing some use issues, such as reliability, life, running quality.


  10, why in the pneumatic valve piston actuator using more and more?


For pneumatic valve, piston actuator can take advantage of gas supply pressure, so that the size of the actuator is more compact than the film type, the greater the thrust piston O-rings are also reliable than film, so its use will become increasingly much.

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