What should be the set pressure of the safety valve on the outlet pipeline of a positive displacement pump?
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According to pump standards, there are certain requirements regarding the setting pressure of the safety valve on the outlet pipeline of positive displacement pumps; it is usually determined as the pump’s outlet pressure plus a margin, or the outlet pressure multiplied by a coefficient. But some people say that this pressure value should be the design pressure of the pipeline. Because it is used to protect pipelines. I lack experience, so I hope fellow sailors can share their opinions. How is the set pressure of this outlet safety valve determined, according to your experience?
The set pressure of the safety valve on the pipeline at the outlet of the positive displacement pump should be less than or equal to the design pressure of the pipeline, in order to ensure its safety.
In that case, can any value be chosen for the coefficient at the pump outlet pressure, as long as it lies between the pipeline design pressure?
The key is to determine who is responsible for this safety valve; if it is provided by the pump manufacturer, it is meant to protect the pump, and the manufacturer decides on that. When designing pipelines, the design pressure should be higher than this pressure. If it is configured by oneself, the calculation is done by multiplying the maximum operating pressure by a coefficient, mainly to protect the pipes.
What you say makes sense too. However, I think it’s just a matter of dividing the scope of supply regarding who will provide this safety valve; there shouldn’t be any difference in the technical requirements for it. Because the installation location is the same, right? !
If the manufacturer supplies the pump, it will select one based on the flow rate and head you specify. If you don’t provide any requirements, they will mainly consider the pump’s pressure resistance, including the pump casing and seals. If you had a request, he naturally prepared it according to your wishes. So there is a sequence: if you design the pipeline first, you need to provide them with the design pressure, so that the pressure of the safety valve does not exceed this design pressure. If you are not sure about your maximum operating pressure, you can only set the design pressure according to the safety valve he has chosen. In the best case, it’s of course safest to prepare it oneself. But you also need to know what the maximum pressure rating of his pump is.
It can also be chosen arbitrarily; if the value is set too low, the safety valve is prone to activating
The Industrial Pump Selection Manual (2nd edition) states that the set pressure of the safety valve on positive displacement pumps is the maximum pressure at the pump’s outlet, and it is primarily used to protect the pump.
I believe the maximum pressure allowed for both the piping and the pump should be the lower of the two values
Well, I learned it*. It should be said that safety valves are used to protect the safety of the system, rather than referring to just a single device. It is more appropriate to take the lower value between the two.
The pump safety valve indeed serves to protect the pump, but when it comes to pressure regulation, it is necessary to take into account the part of the system that is under the lowest pressure. For example, if there is a copper valve installed on a steel pipe, then the pressure should be set according to the safe pressure limit of that copper valve. Currently, there is severe material reduction in engineering projects; it should be determined based on the lowest pressure-bearing part of the actual pipeline system in use.