How to adjust flow with a stop valve. . Who can explain it to me in detail?
Thread Content
I’m quite confused right now. I always thought that stop valves could only be used for shutting off flow. Later, I found out that globe valves can be used for regulation. Who can explain to me in detail how he does it? What theories are there to support this? . I need to figure this thing out :Q
The theoretical foundation is quite complex; it can’t be explained in just a few words, and I can’t explain it either, haha! Simply put, it involves changing the flow area, which in turn increases the pressure drop and thus alters the flow rate. In fact, gate valves can also regulate flow rate. If you have in-depth knowledge, please share more about it.
It is difficult to achieve linear adjustment using a stop valve; in other words, the adjustment characteristic curve is not linear – it is only linear within a certain range. In such cases, unless it is for special purposes, no one uses it for precise adjustments.
Can it only be guaranteed to be linear within a certain region? Was it during the period just before it shut down? .
Globe valve: It is a valve in which the closing element (valve disc) moves along the center line of the valve seat. Based on this type of movement of the valve disc, the change in the valve seat opening is directly proportional to the stroke of the valve disc. Due to the relatively short opening and closing stroke of the valve stem in this type of valve, as well as its highly reliable shut-off function, and because the change in the valve seat orifice is proportional to the stroke of the valve disc, it is highly suitable for regulating flow rate. Therefore, this type of valve is very suitable for use in cutting off or regulating flow, as well as for throttling. Advantages: ① During opening and closing, the frictional force between the valve disc and the sealing surface of the valve body is lower than that of gate valves, thus it is wear-resistant. ②The opening height is generally only 1/4 of the valve seat passage, so it is much smaller than gate valves ； ③Usually, there is only one sealing surface on the valve body and the valve disc, which makes the manufacturing process simpler and facilitates maintenance. ④Since its filler is generally a mixture of asbestos and graphite, it has a high temperature resistance rating. Gauge valves are generally used for steam valves. Disadvantages: ① Since the flow direction of the medium through the valve changes, the minimum flow resistance of a globe valve is also higher than that of most other types of valves ； ②Due to the long travel distance, its opening speed is slower than that of a ball valve.