The FDNY, NFPA 25 and your fire insurance company all require monthly non-flow testing of fire pumps, known as the "churn" test In this test the qualified tester looks at the supply water gauge going to the pump (50 psi) and looks at the water gauge on the system side of the pump (discharge) (150 psi) In this example it means that the pump has added 100 psi to the water. This information shows that the pump is doing it’s job. A rule a tumb is that you need 5 psi to lift water per floor therefore one can assume that this pump can lift the water 20 floors.
The person testing normally has developed an expert eye and ear and looks at the casing relief valve as well as the main pressure relief performance. He looks for leaks, noises and vibrations which are possible tell-tale signs of trouble. This information is entered on the pump record sheet and commonly identified as: 50/150 for the example given above. Keep in mind that the existing gauges that are permanently installed on the customer pump apparatus might not be very accurate. Independent studies by Fire Protection Research Foundation showed that these "churn" tests are usually 95% confidence.
Non-flow tests are required primarily to verify if the pump will start and run without any problems.
NFPA 25 also requires a yearly performance test in which performance readings are recorded at no flow, 100% of rated flow, and 150% of rated flow. Annual flow testing is typically performed by qualified personnel who have a better understanding of the fire pump operation.
The testing team is usually a team of three people. One person is an electrician who measures the rpm of the electric motor (speed at which it turn) looks at rotation of the motor to make sure it’s not turning the wrong way. He measures the electrical amps that the pump draws at each speed at the electrical controller. He collects all this data for entry on a spreadsheet and later use.
The pump specialist and the helper transport the appropriate amount of hoses (each hose only allow for a testing of 250 gpm) to the test header (commonly found on the roof, sidewalk or pump room) and connect same to special nozzles. The pump is turned on and each reading (using a pitot gauge) from each hose nozzle(water discharging ) is taken and recorded on a spreadsheet for later use. If the pump could not supply 95% of the rated net pressure at any point during the test the pump "failed". This pump needs to be rebuilt or replaced.
This yearly water flowing test the output of the pump at 150% of rated flow. The report generated, gives a detailed and historical records of performance year to year and a visual guide to predict with confidence that the pump will be ready to perform. Insurance companies in particular ask for this test report.Estimating Water Flow Rates
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