Fire Pump Flow Head Introduction
The power of the driver equipped with the fire pump should meet the requirements of the power required for operation at any point on the performance curve of the selected water pump flow head. The flow head curve of the fire pump shows a monotonically decreasing distribution, the greater the flow rate, the smaller the head. For example: When spraying water from a water pipe, when you pinch the mouth of the water pipe (small flow rate), the water sprays far away (large head); if you don’t pinch the water pipe mouth (large flow rate), the water sprays close (small head).
There is a small rule in the selection of fire pumps: choose a large flow head instead of a small one, which is known to many people in the industry, but the larger the flow head of the fire pump, the better? There are three common misunderstandings here. In fact, this statement is not wrong, but it does not say what the maximum limit is. Let us tell you about it below:
1. When the actual head of the self-priming pump, centrifugal pump and submersible pump is far lower than the rated head, the flow rate of the pump will increase, so that the current of the pump motor will increase accordingly, which will cause the pump to burn out due to overcurrent. If the head of the pump is indeed too high and cannot be replaced temporarily, you can choose to install a regulating valve at the outlet of the pump to reduce the flow of the pump and control the current of the pump to use within the normal range. This is actually a protection for the pump as well.
2. In terms of the head in the selection of the pump, I feel that the larger the head, the better, but I don’t know that this is the reason for a large part of the centrifugal pump motor to be burned by overcurrent.
3. The lift of self-priming pumps, centrifugal pumps and submersible pumps should be 0.7-1 times the actual lift. The working principle of these pumps is different from that of screw pumps and gear pumps. The actual lift of screw pumps and gear pumps is the pump’s It can be within the rated head range. The greater the resistance of screw pumps and gear pumps, the larger the head. The actual use head of self-priming pumps, centrifugal pumps, and submersible pumps needs to be calculated according to the on-site working conditions.
The empirical algorithm of the fire pump flow head is: the horizontal distance of 100 meters consumes about 10 meters of head, the vertical part is directly converted into the head value, and about 2 elbows in the elbow part consume 1 meter of head. After calculating the actual head, add the margin About 5% can choose the pump model according to this value.
Fire pump flow head selection method:
The flow and head of a fire pump should be selected based on the requirements of the fire protection system. The flow rate should be enough to provide the water pressure and flow rate needed to meet the demands of the system, while the head should be sufficient to meet the pressure requirements of the system. The pump should also be sized to meet the requirements of the local fire code.