If the pressure is low behind the outlet valve of the boiler feed water pump, should the outlet valve be opened or closed?
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The pressure of the boiler feed water pump is low; there is an interlock associated with the outlet pressure, and the pump’s return line has been fully closed. Should I adjust the outlet valve?
Why is pressure controlled by opening and closing valves? Such pumps generally come with variable frequency control, right?
It depends on where the pressure sensing point for your pressure interlock is located – is it at the pump outlet? Still on the main pipe. At the pump outlet, the valve should be closed to build pressure; on the main pipe, the outlet should be opened to increase pressure – dual pumps are necessary if required. (No overcurrent, eliminates pump failure)
The pressure of the boiler feed water pump is low, which can easily result in water not being able to reach the boiler drum. The pump return line of the poster has been fully closed; at this point, it is necessary to check whether the pump outlet valve is stuck. If it is stuck, the outlet valve should be opened fully. If the pump outlet valve is fully open, it indicates that the flow rate of the boiler feed pump is insufficient; in such a case, another pump should be started to operate the system with two pumps. Of course, if there is some issue or malfunction with the pump or its inlet and outlet pipes that prevents the pump from achieving its rated flow rate, it should be repaired before operation.
First, determine the cause of the insufficient pressure – whether it has always been this way or if the pressure changed suddenly. The pressure measurement point must be located after the pump outlet; it is impossible to obtain a normal water pressure if it is placed in front of the outlet valve.
The pump head might be set too low, or the inlet pressure is low. The outlet shut-off is a sequential action; without closing the outlet pump, it cannot operate according to the performance curve, which can easily damage the pump.
Low pressure after the boiler feed water pump outlet valve means the outlet valve should be opened
At first, when the outlet is opened slightly, the pipeline needs to be filled with water; opening it further can cause water hammer. Once the pipeline is filled with water, the outlet should be opened fully and then the pressure increased. There is a control valve on the main outlet pipe of our installation, and later an inverter was installed as well; all the low-pressure automatic start interlocks were removed
The cause should be sought in the pump itself – could cavitation be responsible for the lack of flow? You also mentioned water hammer. Has the water reached its boiling point? ? ? ? This should not happen with water pumps; also, check whether the frequency conversion function of the pump is not in use.