When water is needed in an emergency, the floating fire pump can be counted on. This type of pump allows for the use of alternative water sources such as streams, lakes and other ponds where fire hydrants are unavailable. Unlike the traditional split-case fire pump, these units have the motor and engine assembled in one case that detaches from the float for easy handling. This makes the float fire pump an ideal solution for quick deployment when time is critical.
During an annual flow test, the fire pump must be tested under no-flow (churn), rated and peak conditions to ensure it can deliver its maximum water pressure. When testing under the churn condition, the water flow rate must be at least 150 percent of the fire pump’s rated capacity. The churn flow and pressure must also be within the allowable range for the water supply source.
The churn test is the most difficult for pumps to pass. When a fire pump is accelerating under the churn condition, it draws full locked rotor current. Then, as the speed reaches around 90% of the rated speed, the current begins to decrease to normal running value.
To properly measure these churn and rated flow requirements, the pump must have accurate and calibrated gauges and transducers. It is important that these instruments are used because their readings must be within 1% of each other to identify trends in data. Moreover, the tachometer must be calibrated as well to verify that the fire pump is being driven at the correct speed during the churn and rated flow tests.