The system shuts down when the outlet flow is too high when the fire pump starts
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With the fire pump, even though the valve at the outlet was set to a very low position when the pump was started, it still stopped operating due to current overload. What is the reason for this? The outlet has already been turned down to a very low level. What’s even more troublesome is that this is a fire pump; it takes at least 15 minutes for the pressure at the pipe outlet to increase – isn’t that too slow? Please ask
The effective power under rated conditions is 33 kilowatts; a 45-kilowatt motor is also quite substantial. Overloading of the pump’s motor is usually a problem with the motor itself, such as an issue with the insulation between the coils; this can generally be resolved by removing the motor and heating it up. With submersible pumps, there have also been several instances where the motor tripped frequently due to blockages at the pump inlet. We also had a motor that had high current levels under normal operation, and it would trip at the slightest mistake. After a long time of investigation, neither the electricians nor the fitters would admit that it was a problem related to their own area of expertise. With no other solution, we ended up replacing the motor, and then the current levels returned to normal.
Under normal conditions, the flow rate is calculated based on the pressure difference between the front and rear, that is, with pressure in the rear system. If there is no pressure in the fire water system, the outlet valve must not be opened too wide right after it is started; it can only be fully opened once pressure is established, otherwise overcurrent will cause the system to shut down.
It is possible to test the motor’s insulation index to check whether it meets the requirements
Yes, that’s exactly the case, but this is a fire pump; in a crisis situation, it’s already too late by the time the pressure builds up. So I wonder what the reason is?
The pump inlet is blocked; it seems cavitation is occurring. But what does a high current level mean? Thank you very much
The system backpressure is not established; the pipeline curve is gentle, the intersection point with the performance curve shifts to the right, resulting in a higher flow rate and greater power at the operating point
Under normal circumstances, a fire protection system is equipped with a pressure stabilizing pump. The design takes into account the possibility of the pressure in the piping network dropping below a certain level, in which case the main pump is activated automatically. Therefore, it is necessary to check whether the design of your fire protection system includes such a function; ask again after reviewing the drawings carefully. It seems this is the first time the system is being put into use; the entire fire water piping network is an empty system. When starting the pump, close the outlet, then slightly open the outlet valve, and gradually increase the opening of the outlet valve based on the pressure in the pipeline network.