1. Exactly why is the 2-seat valve vulnerable to oscillation when working under small opening conditions?
For single-core valves, once the medium is flow-open type, they are stable. Once the medium is flow-closed type, they are unstable. There’re two valve cores within the two-seat valve. The low core is within flow-closed condition as the upper core is within flow-open condition. Within this situation, under small opening conditions, the flow-closed kind of valve core will easily cause oscillation from the valve. For this reason two-seat valves can be used as small opening conditions.
2. Why can’t double-sealing valves be utilized for sanitary shut-off valves?
Two-seat valve core has the benefit of balanced pressure double-sealing valve structure, allowing a sizable pressure difference. And it is disadvantage would be that the two sealing surfaces can’t be in good contact simultaneously, creating a large leakage. Whether it’s purposefully and mandatorily utilized in shut-off occasions, the result will not be great, even when lots of enhancements happen to be made onto it. (for example double-sealing sleeve valve)
3. How come the straight stroke sanitary controlling valve possess a poor anti-blocking performance and rotary stroke controlling valve have a very good anti-blocking performance?
The main of straight stroke valve is vertical throttle, however the flow direction from the medium is horizontal. So there has to be plenty of twists and turns in valve cavity flow funnel, making the flow pathways from the valve very complex. Therefore, there’re lots of blind zones that offer space for deposition from the medium, which over time causes clogging. The throttle direction of rotary stroke valve is horizontal, the medium horizontally flows out and in, which could easily remove unclean medium. Meanwhile, the flow path is straightforward, and there is little room for medium deposition, so rotary stroke valve includes a good anti-blocking performance.
4. Exactly why is the stem of straight stroke controlling valve thin?
It calls for an easy mechanical principle: the larger the sliding friction, the smaller sized the moving friction. The stem of straight stroke valve rises and lower. When the stuffing slightly pressed just a little tighter, it might summary the stem tightly, producing a large hysteresis. For this finish, the valve stem is made to be thin and small , the stuffing use PTFE which has a small friction coefficient to be able to lessen the hysteresis. The main problem that stems from this really is that the thin valve stem is simple to bend and also the stuffing includes a short service existence. To resolve the issue, the easiest way is by using rotary valve stem, a controlling valve like the rotary stroke ones. Its valve stem is two to three occasions thicker compared to the straight stroke valve. Also it uses graphite stuffing which has a lengthy service existence. The valve stem stiffness is nice, the service existence of stuffing is lengthy, the friction torque and hysteresis are rather small.
5. How come the rotary stroke valve possess a relatively large shut-off pressure difference?
It is because the torque around the rotating shaft created through the pressure of medium on valve core or valve plate is extremely small.
6. Exactly why is the service existence of desalination water medium short when utilizing rubber lined butterfly valve and fluorine lined diaphragm valve?
The medium of desalination water contains low concentrations of acidity or alkali, that are pretty corrosive to rubber. The corrosion of rubber is exemplified by expansion, aging and occasional strength. Poor people aftereffect of using rubber lined butterfly valve and diaphragm valve is really brought on by the intolerance of corrosion of rubber. Rear rubber-lined diaphragm valve is improved upon is the fluorine lined diaphragm valve which has a good tolerance of corrosion. However the lining of diaphragm of fluorine lined diaphragm valve can’t withstand the up-and-lower folding and it is damaged, leading to mechanical damage and shorter service existence from the valve. Now the easiest way is by using water treatment special ball valves, that you can use for five to eight years.
7. Why must shut-off valves use hard sealing?
Sanitary shut-off valves require leakage to become to a minimum. The leakage of soppy sealing valve may be the cheapest, therefore the shut-off effect is unquestionably good. But it is not put on-resistant, not reliable. Knowing in the double standard of small leakage and reliable sealing, soft sealing shut-off isn’t as good as hard sealing shut-off. Take full-featured ultra-light controlling valve for instance, it’s sealed and stacked with put on-resistant alloy for defense, highly reliable, includes a leakage rate of 10 to 7, which curently have met the needs of shut-off valves.
8. Why can’t sleeve valves replace single-seat and double-seat valves?
Sleeve valves, which first made an appearance within the ’60s, were broadly utilized in the ’70s worldwide. Sleeve valves take into account a sizable percentage in petrochemical equipment imported throughout the ’80s. In those days, lots of people thought sleeve valves could replace single-seat and double-seat valves to get the 2nd-generation products. So far, that isn’t the situation. Single-seat valves, double-seat valves and sleeve valves are equally used. That is because sleeve valves only improve the clear way of throttle, have better stability and maintenance than single-seat valves. Nevertheless its weight, anti-blocking and leakage indicator overlap with individuals of single-seat and double-seat valves.
9. Exactly why is selection more essential than computation?
Compare computation with selection, selection is much more important and much more complicated. Computation is just a simple formula. It isn’t the formula itself, but instead the precision of given parameters that means something. Selection involves several things, as being a bit careless can result in improper selection, which not just leads to the waste of manpower, material, and cash, however the results of use aren’t good, causing numerous problems being used, for example reliability, service existence and quality, etc.
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