Three-valve assembly and five-valve assembly
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The three-valve assembly is designed to maintain the transmitter; when in use, the valves on the positive and negative pressure sides are opened first, followed by the middle balance valve； When shutting down, close the balance valve first; it is best to close the valves on both the positive and negative pressure sides ； What is the basis for choosing between a three-valve unit and a five-valve unit when selecting a valve assembly? What are the advantages of choosing a five-valve unit?
The five-valve assembly adds sewage outlets for high-pressure and low-pressure measurements on top of the three-valve assembly; its usage is no different from that of the three-valve assembly.
The original poster wasn’t very clear; to open the three-valve assembly, one should first open the balance valve and then the valves on the high-pressure and low-pressure sides. Pay attention to the function of the balance valve.
Function of the three-valve assembly: To connect or disconnect the positive and negative pressure chambers of the differential pressure transmitter from the pressure lead pipes, or to disconnect or connect the positive and negative pressure chambers themselves. Features of the five-valve assembly: It allows for the inspection, calibration, or cleaning of the instruments online at any time. Rinsing reduces the hassle associated with installation. It functions in the same way as the three-valve assembly.
The five-valve assembly integrates high and low pressure drain valves on the basis of the three-valve assembly
The original poster got it backwards – when starting up the system, the balance valve is opened first; when performing maintenance on the instruments, the high and low pressure sides are shut off first, followed by the balance valve
The five-valve unit is too small; it’s inconvenient to reach in order to turn it on or off, so it’s not practical to use. A three-valve unit will suffice; you can arrange the drainage system by yourself, or handle everything on your own. This post was last edited by zhaohh3211 on 2008-12-13 13:53.]
I don’t think the 5-valve assembly has any particular advantages; the 3-valve assemblies also come with plug valves for sewage and venting. If the 3-valve assembly can handle the tasks at hand, why use a 5-valve assembly? I’ve never used a 5-valve assembly myself, though some of my colleagues have purchased them, and I haven’t dared to use them. The intuition isn’t very good; it seems that the sealed areas are likely to have problems. I wonder if anyone has used it in person; let me give a brief introduction.
The five-valve assemblies are fine, while three-valve assemblies are basically no longer needed nowadays；
The five-valve assembly adds high and low pressure drain valves to the three-valve assembly, but they are generally not used for draining purposes; once the pressure tapping valve is closed, it serves to release air from within the diaphragm box, and it can be used to empty this air in order to zero the instrument. If you need to drain fluid, it is recommended to use the drain screw located after the transmitter. Since the five-valve assembly is situated before the transmitter, it can only be used to drain fluid from within the pipes. If there is dirt in the diaphragm box, it cannot be removed using the five-valve assembly
We usually use three sets of valves, not five; one extra integrated valve means one extra point of leakage