Is there an inevitable relationship between the magnitude of pump outlet pressure control and the pump head?
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Hello everyone, I have an operational issue in actual production and would like to seek advice from those with more experience: every time the centrifugal pump is started, the outlet pressure is adjusted by modifying the pump’s outlet valve. What criteria should be used to determine what the appropriate outlet pressure for the pump should be? In practice, we always determine the outlet pressure based on the head indicated on the nameplate. For example, if the head specified on the nameplate is 90 m, many of us assume that a downstream pressure of 0.9 MPaG is considered normal. Do you think that’s correct? I don’t think that’s right. I believe the head indicated on the nameplate merely shows the capacity of the pump; as for what the outlet pressure should be at this time, it should be determined based on actual needs. The outlet valve can be opened wider to reduce the outlet pressure below 0.9 MPaG, and even lower pressures can be achieved when a high flow rate is desired, as long as the motor’s rated current isn’t exceeded. What do you think?
We usually keep the manual valve fully open and then control the flow rate using a control valve; the pump head merely indicates the pump’s ability to lift liquids to a certain height. The size of the export control is no longer related to the pump head.
Reply to 1# 262885705: I agree with your view.
I think the flow rate and head can be interchanged on the nameplate; it’s just that the pump’s capacity does not determine the outlet pressure. Head and flow rate are related to each other – the larger the outlet diameter, the relatively lower the outlet pressure will be. This can be tested by installing a pressure gauge in front of the outlet valve
The outlet pressure control should be based on the actual production requirements; the pump’s head should not be taken into account, as it is merely one of the parameters of the pump. The original poster’s view is correct!
There are curves showing the pressure (head) of each water pump in relation to its flow rate and motor power. Adjustments should be made according to the actual operating conditions (the size of the outlet valve can be adjusted). The parameters on the nameplate refer only to those at the optimal operating condition. As long as it stays within the traffic range (maximum, minimum).
In actual production, the focus is on meeting the flow requirements for production and ensuring smooth operation of the pumps (that is, to avoid exceeding current limits). Rest assured, there is no problem with this. Theoretically, however, it is generally required that the outlet pressure of the pumps not exceed the head value plus 10 meters, with the minimum pressure not exceeding the head value plus 20 meters; of course, these are just the regulations in our workshop.
I completely agree with the original poster’s view; head is not the only factor to consider, as the rated current of the pump is what really matters. As long as the current doesn’t exceed the limit and the pump isn’t overloaded, there’s no problem.
As long as the production requirements can be met and the motor is not overloaded, that’s fine; of course, this is related to the selection of the pump.
Agree with the opinion from the 3rd floor; in fact, there is also the static pressure inside the equipment
It is true that the head indicated on a centrifugal pump’s nameplate can be converted into outlet pressure. But centrifugal pumps have a pump efficiency. The parameters indicated on the nameplate are generally those at the pump’s highest efficiency. Therefore, unless adjustments to the flow rate are necessary for production reasons, it is advisable to keep all parameters of the centrifugal pump at their rated values. If an increase in flow rate is desired, it is recommended that it not exceed 50% of the rated value, and such operation should not be sustained for long periods, unless variable frequency control is used