Weekly or Monthly No Flow (Churn) Tests of Fire Pumps
Fire pumps are an essential part of many water-based fire protection systems. They are used to increase the pressure (measured in psi or bar) of a water source when that source pressure is not adequate for the system it’s supplying. The right design, installation, and acceptance testing of these pumps will ensure that they are ready and available to protect the building on the day of the acceptance test. After that, once “the keys” are handed over to the building owner, there is no guarantee that the pump will remain in a ready state to work as designed unless it undergoes routine inspection, testing, and maintenance (ITM). The requirements for ITM of fire pumps are found in NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems.  While there is a good deal that goes into a robust ITM program for fire pumps, this blog will focus on the no-flow test of fire pumps which is often referred to as a churn test. See this blog for weekly fire pump inspections. What is the purpose of the no-flow test? NFPA LiNK where hot spots can be chosen to find more information about certain inspection and testing requirements for different components. How often is a no-flow test required? The no-flow (churn) test of fire pumps must be conducted at either a weekly or monthly basis. The frequency varies by the type of fire pump; diesel and electric; and both have allowances to extend the time between tests based on approved risk analysis. Generally, diesel fire pumps must be no-flow (churn) tested on a weekly basis. The requirements for electric fire pumps vary. Most electric fire pumps can be no-flow (churn) tested at a monthly frequency. Electric fire pumps which (1) serve fire protection systems in buildings that are beyond the pumping capacity of the fire department, (2) have limited service controllers, (3) are vertical turbine fire pumps, or (4) those taking suction from ground level tanks or a water source that does not provide sufficient pressure to be of material value without the pump all require no-flow (churn) tests at a weekly frequency unless they are provided with a redundant fire pump. Starting The no-flow (churn) test needs to be conducted by starting the pump automatically. The pump must be started by drawing water from the sensing line to simulate a pressure drop in the system rather than using the “start” button on the front panel of the fire pump controller. An allowance is included in NFPA 25 for an automatic timer using either a solenoid valve drain on the pressure control line for a pressure-actuated controller or another means for a non-pressure-actuated controllers. Run time Electric pumps must be run for a minimum of 10 minutes while diesel pumps must be run for a minimum of 30 minutes. Personnel Qualified personnel must be in attendance whenever the pump is in operation unless automated inspection and testing is performed in accordance with the requirements of NFPA 25. Check out this blog for more on automated and remote inspection and testing. Qualified personnel is defined in NFPA 25 as competent and capable individual(s) having met the requirements and training for a given field acceptable to the AHJ. Relief valves NFPA 25 allows the circulation relief valve to open to flow water as a cooling measure. Allowing any additional water flow to prevent overheating is not a requirement of the standard. Flow from the circulation relief valve should be sufficient to prevent over-heating of the pump. It should be confirmed that the circulation relief valve is discharging a small flow of water during the no-flow (churn) test. There are additional details around circulation relief valves and main pressure relief valves in NFPA 25 which personnel should familiarize themselves with. Visual observations while pump is not running The following visual observations need to be conducted while the pump is not running. Record the system suction and discharge pressure gauge readings. For pumps that use electronic pressure sensors to control the fire pump operation, record the highest and lowest pressure shown on the fire pump controller event log where such information is available without having to open and energized motor-driven fire pump controller. If the highest or lowest pressure is outside of the expected range, record all information from the event log that helps identify the abnormality. Visual observations or adjustments while pump is running The following visual observations or adjustments need to be conducted while the pump is running. Pump system procedure as follows: Record the pump starting pressure from the pressure switch or pressure transducer Record the system suction and discharge pressure gauge readings Adjust gland nuts if necessary Inspect the pump packing glands for slight discharge Inspect for unusual noise or vibration Inspect packing boxes, bearings, or pump casing for overheating Record pressure switch or pressure transducer reading and compare to the pump discharge gauge For pumps that use electronic pressure sensors to control the fire pump operation, record the current pressure and the highest and the lowest pressure shown on the fire pump controller event log. For electric motor and radiator cooled diesel pumps, check the circulation relief valve for operation to discharge water Electrical system procedure as follows: Observe the time for motor to accelerate to full speed Record the time controller is on first step (for reduced voltage or reduced current starting) Record the time pump runs after starting (for automatic stop controllers) Diesel Engine system procedure as follows: Observe the time for engine to crank Observe the time for engine to reach running speed Observe the engine oil pressure gauge, speed indicator, water, and oil temperature indicators periodically while engine is running Record any abnormalities Inspect the heat exchanger for cooling waterflow Steam system procedure as follows: Record the steam pressure gauge reading Observe the time for turbine to reach running speed In addition to the above, the discharge temperature of the water must be monitored, and the pump shut down if necessary to prevent exposing the pump and/or driver to excessive temperatures. Where the recorded pressure readings on the discharge and suctions gauges show a difference that is greater than 95 percent of the rated pump pressure, the situation needs to be investigated and corrected. The weekly or monthly no-flow (churn) test is an important part of ensuring that a fire pump can be continually relied upon in the event of a fire. These tests will help to ensure that the pump will start and will not overheat in the event of a fire. At an annual frequency, flow testing will be performed to further verify the complete operating condition of the pump. NFPA has a number of resources related to fire pumps and the ITM required for them. Some of these include NFPA 20 Online Training Series, NFPA 25 Online Training Series, the NFPA 25 Handbook, the Certified Water-Based Systems Professional (CWBSP) credential, and the Certified Water-Based Systems Professional Learning Path among many others.