The safety valve or pressure relief valve is partially open
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This post was last edited by k110 on 2019-1-31 at 14:58. These past couple of days I’ve seen some people using the safety valve (the one on the nameplate) with it partially open, meaning water keeps flowing through the valve. In my understanding, a safety valve is supposed to be closed under normal conditions and to open when pressure rises in order to release excess pressure; their intention seems to be to maintain a constant pressure, allowing the system to operate at that level, using the valve as a pressure regulator. But is it reasonable to keep the valve at a certain degree of openness so that water can flow through it continuously? As for the UPVC safety valve used on metering pumps, as shown in the figure
It’s unreasonable. The safety valve shown is also used by our company. If the pressure in the outlet main pipe of the acid metering pump exceeds the set value, it will return to the acid metering tank. After the safety valve operates, the tightness of the rear seal can no longer be guaranteed, requiring grinding or replacement of the sealing surface. The pressure must be rechecked and a pressure test for leaks must be conducted before it can be used again. A special operation permit is required for safety valve calibration. What you mean is probably a pressure relief valve or a decompression valve.
This post was last edited by k110 on 2019-1-31 at 17:23. I expressed it incorrectly; what happens during this installation is that a bypass is added, with the pump outlet connected to a branch pipe that then leads to a valve, and after passing through the valve, the fluid returns to the tank. It is designed to maintain the pressure before the valve, not after it; therefore, it is not a pressure reducing valve. After learning more about it, it seems that what they mean now is that once the safety valve opens, its opening degree changes somewhat in response to pressure variations. Changes in flow rate or pressure in the pipeline downstream of the pump cause this adjustment in the opening degree, thereby ensuring that the pressure downstream of the pump remains constant. It’s somewhat like a pressure regulator combined with a buffer tank. In this case, the valve doesn’t close, so there are no issues related to sealing surfaces or leaks; therefore, it’s likely that no calibration is necessary. In principle, there seems to be no problem, but is this approach really okay? It feels really unconventional
It’s very common. Our company’s acid-base systems, scale inhibitors, and biocide systems are all like this. For system selection, there are some systems with low pressure, and the overpressure valve can also be used as a safety valve. The sealing surfaces are mostly made of PTFE gaskets, so the likelihood of severe leakage after operation is low. Slight leakage does not affect the pump’s output. Under normal operation, this valve should not operate. If there is a movement or internal leakage. When the pressure after the pump is lower than the system pressure, it only pumps back to the medicine tank, thus creating a circulation. It can’t be added to the system anymore.
This is not a traditional safety pressure relief valve; it belongs to the category of overflow valves
This valve is a safety valve, but it is not used in the manner appropriate for a safety valve; rather, it is used as a pressure stabilizing valve. As long as it is not treated as a safety valve and no safety risks arise, using it in this way is fine