Problems with check valves and relief valves
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Is the opening pressure of a check valve the pressure difference between the inlet and outlet? ? If the opening pressure is 1 bar, does the check valve open when the pressure difference across it exceeds 1 BAR? ? If the inlet pressure is equal to the sum of the spring pressure and the outlet pressure, is the check valve in an open state? ? Is the opening pressure of the relief valve exactly the pressure of the spring? ? So the spring force of the relief valve is much greater than that of the check valve, right? ? ?
The last edit to this post was made by ylb913 on 2018-6-9 at 20:59. When selecting the resistance of a check valve, one must first consider the back pressure, which is determined by the control pressure of the subsequent equipment as well as the pressure drop of the medium being transported earlier. For logistics operations under high pressure, no one pays attention to that slight pressure drop caused by check valves. It’s precisely because of the low medium pressure that choosing a check valve proves to be quite challenging. There should always be some margin for voltage drop, but sometimes it’s really difficult to choose a suitable sample after going through various options. I’m afraid of that choppy state, with those fluctuations, causing fluctuations in traffic volume. I have never heard of the type of relief valve described by the poster. But when it comes to the operating pressure and the spring, it is actually the pressure exerted by the spring; this is determined first by the back pressure, and then the design pressure of the equipment in question is chosen by adding the pressure from the spring, with some margin also being left for flexibility. ——Of course, it is also necessary to consider ways to reduce the back pressure due to the constraints imposed by the design requirements of the preceding devices.
Doesn’t a check valve generate backpressure? The pressure at the inlet rises to the sum of the spring pressure and the pressure at the outlet. . . . Doesn’t a check valve increase pressure? How can there be a pressure drop then? . . I’m confused
This post was last edited by ylb913 on 2018-6-9 21:16. Back pressure is the pressure that exists at the back, not one that is generated at the front. For a check valve, its back pressure is independent of the pressure drop across the check valve, with the check valve being in front.
So what I understand is that the pressure drop you mentioned refers to the opening pressure of the check valve, right? I would like to ask: if a check valve is installed in the return oil circuit, what if the pressure before the valve is unknown? . . The opening pressure of the check valve is 0.1 MPa, and the pressure behind the valve is at atmospheric level. Does this mean that a backpressure of 0.1 MPa is generated in the return circuit? The pressure on the other side of the valve must be greater than 0.2 MPa for the check valve to open
The back pressure here is the atmospheric pressure; if necessary, the pressure drop of the fluid behind the check valve may also need to be taken into account.
Why does a check valve create a pressure drop?...... I’ve read online that back pressure refers to the pressure in front of the valve... But you are referring to the pressure behind the valve. . . . I’m confused; please help, experts!