TESTING BUILDING FIRE PUMPS
(Photos by author.)
An important component of a building’s emergency equipment, the fire pump requires an acceptance test and annual testing per NFPA 20, Installation of Centrifugal Fire Pumps and NFPA 25, Inspection, Testing and Maintenance of Water Based Extinguishing Systems to ensure that it will respond and perform in a fire emergency. Part one of a two-part series, which is a synopsis of many of the requirements found in NFPA 20 and 25, this article discusses the objectives of and how to prepare for the actual pump test.
An original acceptance test must be performed on a new fire pump system to verify that it has been selected, designed, and installed as intended. For this test, the pump installer and manufacturer’s representative should be present. A test of an existing fire pump assembly will detect the reasons, if any, for the pump not operating as originally designed and determine if the pump will meet the flow and pressure demand of the system it supplies.
TYPES OF PUMP DRIVERS
Most fire pumps are driven by an electric motor, which is supplied from a single connection to the public utility and possibly to an emergency generator or second utility through an automatic transfer switch. Where the electric power supply is not considered reliable, an engine is installed to drive the pump. Since the 1974 edition of NFPA 20. only diesel engines are permitted on new installations. Older installations may have engines fueled by gasoline, liquefied petroleum gas (LPG), or natural gas. In rare cases, fire pumps are driven by steam turbines.
During the testing of a fire pump installation, you must observe each element of the system. This includes suction supply; net pump performance, which depends on the diameter and condition of the impeller and wear rings, speed of rotation (rpm), and horsepower of its driver; pump driver and power or fuel supply; controls, including required automatic and manual starts; operation and condition of any auxiliary or support systems such as pump house heating and lighting, security, remote alarms or trouble signals, and proper drainage and sump pumps; emergency standby or alternate power supply if provided, including switch-over while the pump is operating at peak load; and any condition that may prevent proper pump operation.
EQUIPMENT NEEDED
Certain tools, supplies, and equipment are required to verify the net pump performance and its suction supply. The primary test encompasses taking measurements of inlet and discharge pressures at flows (in specific increments) throughout the pumping range.
To test for this data, you will need the following:
- Test-quality calibrated suction and discharge gauges (a spare set is recommended).
- Pitot tube and calibrated gauge.
- Hydrant cap gauge.
- Underwriter’s playpipe with 1 ¾-inch tip and removable 1 ⅛-inch tip plus 100 feet of 2 1/2-inch fire hose for each 250 gallons of pump capacity. (If the pump installation includes a flow meter piped back to suction, sufficient hose and playpipes may be necessary to verify the suction supply by flowing one or more remote outlets, such as yard hydrants, wall hydrants, or roof manifolds.)
- Orifice pressure and flow tables or calculator.
- Tachometer.
- Voltammeter.
- Safey glasses and ear protection.
- Test forms and semilog 1.85 graph paper.
- Pump manufacturer’s data including factory-certified test curves (if a new pump) or previous test reports on an existing installation. If the certified curve or previous test results are not available, the manufacturer’s data plate affixed to the pump or its base should list pump rated speed (rpm), rated pressure (psi), rated capacity (gpm), and pressures at shutoff (no flow) and 150 percent of rated capacity.
PREPARING FOR THE TEST
Before the actual test, visually check the following to gain an understanding of the system, plan the test, and verify compliance of the installation with NFPA 20. Should the installation not be found in compliance with the requirements of NFPA 20, terminate the test until corrections are made to the installation.
- Is the driver rated at the same speed (rpm) as the pump?
- Pump rotation direction: Does the pump rotate properly with both
- power supplies (primary and emergency generator or second supply)?
- Coupling or drive shaft alignment.
- All valves in suction line are open.
- How will the system be tested? With a flow meter back to suction or suction reservoir, make sure the tubes from the meter primary element to the meter are bled free of air before the test. Since flow meter discharge
- piping typically is piped back to the suction side of the fire pump, the suction supply must be verified at a yard hydrant, wall hydrant, or roof mainfold. If testing at an outside test header, ensure that flows can be discharged safely. If testing at an inside test header, check that hoses can be run to a discharge point without risking injury to personnel or creating a flooding hazard.
- Is the piping and valve arrangement proper? Check if the suction and discharge pipe sizes are at least as
- large as specified in NFPA 20, Table 220.
- Are separate brass (pressure-sensing) lines provided for each pump (including the jockey pump), and are they connected to the pump piping between the discharge check valve and control valve? If controllers are mounted to an outside wall, check that there is sufficient clearance or insulation to prevent freezing.
- Are proper and adequate drains provided to prevent flooding of the pump room or wetting of electrical components by the pump relief valve, circulation relief, air release, engine heat exchanger waste, bracket (packing gland) drains, and engine controller solenoid? Is the circulation relief valve discharge pipe separate from the air release and bracket drains?
- Is the pump foundation grouted?
- Are all pipes properly supported?
- Is a relief valve provided for a positive displacement jockey pump? Where does it discharge? Does the jockey pump have a discharge pressure gauge adjacent to its discharge outlet?
- Check that all bolts and nuts arc in place and apparently tight.
- Check that all guards are in place (fan belt, drive shaft, coupling). An ccurate photoelectric tachometer reading may require that you remove the guard to the coupling or drive shaft during the test.
- Are engine oil and coolant, gear drive oil, and battery electrolyte levels as specified? Are the battery cables and clamps in serviceable condition?
- Are the electrical connections to the controller and motor tight?
- Are pump and driver bearings lubricated?
- Determine how the pump can beisolated from the rest of the system. Is there a bypass around the pump to provide some fire protection until the test can be terminated and the pump placed back in service? If the bypass is an “emergency” bypass consisting of one normally closed valve, the pump cannot be tested with this valve open.
- With an engine drive, is the exhaust piping properly supported and not in contact with combustibles?
CARE OF EQUIPMENT AND PERSONNEL SAFETY
To reduce the risk of injury or damage to the equipment before, during, and after the pump test, take the following precautions.
Keep hoselays as short and as straight as possible, avoiding kinks or letting the hose rub against any sharp or rough objects.
Securely tie down hose nozzles unless personnel trained in handling heavy hose streams are available. Do not mount playpipes directly on the test header valves unless they are gate-type valves and there is no possibility of the nozzle reaction unscrewing the test header.
Do not open or close any valves quickly, except in an emergency such as a nozzle coming loose or a coupling pulling off a hose. (It usually is safer to shut down the controller.)
If a pilot light on an electric controller does not light, don’t put a finger or any tool in the socket unless the breaker and isolating switch are open.
In a high-rise series pump system, don’t test the high-zone pump through the test header while the low-zone pump is operating. If there is no bypass around the low-zone pump, the high-zone pump should be tested through the roof manifold or highest hose outlets.
Never examine a coupling, drive shaft, fan belt, or impeller unless the controller is “off” and locked out.
Never stand in front of an electric controller, transfer switch, or circuit breaker when it is being operated.
Never open or close an isolating switch unless the circuit breaker is tripped (off).
If the circuit breaker trips for no apparent reason, stop the test until an electrician determines the cause.
In Part 2 we will discuss procedures for the test and evaluating data.
