Interpreting results for fire pump tests
A fire pump is the heart of the fire protection system. Fire pumps require flow testing at least annually in accordance with Chapter 8 of NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2011 edition, at which time a full performance evaluation must be conducted. Observed testing should be compared to the original manufacturer and acceptance test information as well as the fire pump data plate. Per NFPA 25, “qualified individuals shall interpret the test results” for the following criteria:
Net pressure is the pressure the pump creates and is the most critical indicator of pump system health. At each observed flow rate, net pressure must be at least 95% of either: 1) the pressure at rated flow and speed recorded on the unadjusted field acceptance curve, or 2) the rated pressure listed on the pump data plate. This interpretation may require adjustment for observed speed (rpm) if it differs from rated speed.
Discharge pressure is the pressure provided for the fire protection system and varies based on suction pressure and flow rate. This unadjusted pressure must be compared to the fire protection system demand to ensure the pump can supply the required system demand per the hydraulic placard(s).
Consistent power is required to drive the pump at all required flow rates. For electric pumps, the voltage should be within a range of 5% below to 10% above the listed motor data plate, while the current should not exceed the rated amperage multiplied by the motor safety factor at any flow rate. For diesel-driven pumps, the fuel must be tested annually in accordance with ASME standards. Variable speed pumps require evaluation at additional test points.
Although not a comprehensive list, these are the crucial aspects of a flow test. And remember, an observation is only as accurate as the equipment used to record it, so make sure all test equipment is calibrated within one year with suitable accuracy and scale. Taking appropriate care in evaluating flow test results is necessary to maintain a healthy fire protection system.
Chris Ribando, CET, is vice president at Approved Fire Prevention Corp.
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