Performance Testing of Fire Pump
Fire pumps are complex systems that present one of the greatest testing challenges to contractors and field technicians. Unfortunately, many individuals tasked with performing these tests simply lack the necessary expertise. A botched-up fire pump test may fail to discover a major problem, or can result in unnecessary corrective work.
Fire pumps must satisfy the following performance goals:
- Start and run
- Supply the volume and pressure intended in the fire protection system design
- Initiate the necessary signals to alert responding personnel
- Keep running for the duration of a fire event.
Like any mechanical/electrical system that spends its life in standby mode, the system must receive periodic evaluation and testing to ensure that it has not been compromised by wear, age and the elements. If a fire pump fails to achieve any one of the above performance goals during a fire emergency, it will not adequately supply fire protection systems, the fire department will not have enough water, or both.
As an owner, your organization spent a lot of money installing and maintaining their fire pump system. You expect it to be available when needed, perform flawlessly and protect your assets.
As a contractor, you do not want to see a fire at your customers’ facility on the evening news after you just tested their systems. With that in mind, treat each performance test as if it was the last test before that fire.
NFPA 25, Inspection, Testing and Maintenance of Water-Based Fire Suppression Systems, as well as many state and local fire codes require that fire pumps receive an annual performance test. This is the most rigorous test the system receives between its commissioning and an actual fire. The goal of the annual performance test is a thorough test and evaluation of not only the fire pump, but of the entire fire pump system. As NFPA 25 states, this is to be performed by “qualified personnel”, but NFPA does not enumerate qualitative criteria for being “qualified”. Many jurisdictions require a fire protection contractor license to perform the annual performance test. Some jurisdictions require National Institute for Certification in Engineering Technologies (NICET) certification for field technicians to meet NFPA’s “qualified personnel” requirement.
In addition to properly performing the testing, the interpretation of the test results requires an understanding of hydraulic principles, centrifugal pumps, motors and controllers and is paramount to reach a conclusion as to the overall condition of the fire pump system.
The goals of the annual performance test are as follows:
- Comparing the field measurements against the certified pump curve.
- Ensuring that the fire pump system does not exhibit problems when operating under full load.
- Testing all ancillary systems to the extent possible in the field.
The proper testing of a fire pump system takes time and preparation. This includes ensuring that all measuring instruments are properly calibrated. NFPA does not set calibration standards, but industry practice for test instruments is at least annually. In addition, necessary measuring devices, such as smooth-bore nozzles, hoses, brackets, and common hand tools should be available. One or more assistants may be needed. Also, a qualified person able to perform simple testing on energized electrical systems should be on hand. The test comprises the following essential parts:
1. Start with a visual evaluation of the entire fire pump system to identify potential problems that could complicate the test or result in adverse conditions.
2. The automatic starting function should be tested. Determine whether the actual starting pressure is within the guidelines of NFPA 20.
3. The pump should be tested from churn conditions all the way to 150% of its rated capacity while taking the appropriate readings for each point. At least three points (churn, rated capacity and 150% of rated capacity) should be taken. Since these are nominal points on the pump curve, it is not necessary to measure flow exactly at 100% and 150%.
4. If a recirculating flow meter is provided, NFPA 25 requires measuring the flow against pitot tube readings every three years. Many perfectly good fire pumps were needlessly overhauled because of erroneous flow meter readings. One method of performing a field calibration of the flow meter can be done relatively easily by measuring a flow rate between 100% and 150% of the pump rating (the higher the flow the better) with a pitot and then recording the corresponding discharge pressure at the pump. Then, adjust the flow rate through the flow meter until the same discharge pressure is obtained as earlier. The flow meter reading is then compared against the flow obtained with the pitot flow measurements. If both readings are within 5%, then the accuracy of the flow meter is acceptable and all other flow measurements can be taken through the flow meter. This method can also be used to verify the flow meter’s accuracy when unsatisfactory results are obtained.
5. Let the pump run for a while at the 150% point as this places the greatest load on the system. Watch for overheated diesel engines, fuel system failures, and electric breakers tripping during peak conditions. NFPA 25 requires that electric pumps be operated for no less than 10 minutes and diesel pumps no less than 30 minutes during the annual test.
6. On electric pumps, voltage and current readings need to be obtained at the controller for each test point where a digital external gauge is provided. Voltage readings should be within 5% below and 10% above the rated voltage. If current readings exceed the rated amperage of the motor, the product of voltage and current must be within the product of the rated current and amperage times the service factor stamped on the motor nameplate.
7. The minimum necessary raw test data include suction and discharge pressures, flow rates and pump speed. Adjust the raw data points to the rated pump speed before plotting on the graph. Per NFPA 25, if the pump’s actual performance is more than 10% deficient, investigation and corrective action is required.
8. An area usually overlooked is the testing of fire pump controller alarm signals. For electric pumps, this usually includes pump running, power failure, phase reversal and loss of phase. For diesel pumps, this includes pump running, switch in OFF position, AC power failure, charger failure, high coolant temperature, low oil pressure, overspeed and failure to start. The procedure for testing these signals can usually be found in the pump controller manual.
9. Next, the emergency manual starting means should be tested. Electric and diesel pumps are provided with the ability to start the pump manually in the event of a total failure of the controller. Electric pump controllers usually have a manual switch and diesel engines have provisions for opening the fuel, establish coolant flow and crank the engine.
10. The fuel should be inspected on diesel drives. At minimum, several gallons of fuel should be drained from the tank to remove water and contaminants that have settled to the bottom.
11. On newer computer-controlled diesel engines, the engine needs to be test-run on the alternate electronic control module (ECM) to ensure its functionality.
12. During the testing, attention should be paid to unusual noises, vibration and engine vitals. At the conclusion of the test, all valves and switches should be returned to their normal positions, one last automatic start sequence should be initiated to verify its proper operation and the facility fire alarm panel(s) should be checked to ensure that all signals are properly reset.
The test report is an important document to owners, inspectors, consultants and other stakeholders. It is much more than a checklist or “certificate”. If the report and the data are thorough and accurate, it reflects positively on the tester and their employer. The report provides reassurance that the system is in good working order, or it can highlight problem areas that need to be addressed. If, however, the report is incomplete and/or contains bad data, the time and resources expended for testing were wasted. The test will have to be repeated, reputations are at stake and someone else may end up with the testing contract next year.
The annual fire pump performance test report should contain all raw and corrected data points, a list of all tested components and provide a final conclusion as to the condition of the fire pump system along with a section that describes any findings or deficiencies. The completed report must be accurate and complete enough to allow a technically competent reviewer to validate the conclusion based on your provided data.
A statement should be included as to the overall performance of the fire pump system, along with any findings and recommended corrections. If the pump does not meet the minimum requirements, it may need to be overhauled and a diagnosis should be included on the report to provide an indication to the repair concern.
If Something Goes Wrong
One of the reasons for testing any system is to identify weak links before it is too late. When something breaks or fails during a test, the test should not be viewed as the culprit, but rather as the successful discovery of a significant problem.
Fire pumps produce enough energy to inflict serious injury. This can be avoided by following good safety practices and awareness of the following:
- If using hoses and nozzles for measuring flow, make sure that the nozzles are securely strapped. You don’t want them to come loose under pressure.
- Particular care should be given to arc flash hazards when opening electric pump controllers. On older controllers without a digital readout, Volt and Amp readings needed to be measured with portable equipment, but NFPA 25 is moving away from this for safety reasons. Work inside controllers is best left to a qualified electrician wearing the appropriate safety gear.
- Stay clear of lead-acid batteries. In rare cases, these can explode under a starting load.
- Avoid standing alongside operating diesel engines. The sides are the weakest part of the engine block and internal moving parts can punch through them in case of a mechanical failure. Similarly, standing in the radial space around the flywheel should be avoided.
- A diesel engine cooling system contains water at about 200 degrees F and 35 psi. This is enough to cause significant burns. There are many potential failure points (hoses, heat exchangers, caps, etc.). Avoid standing near them.
Common Shortcomings and Causes of Botched Tests
- Failure to use calibrated measuring instruments
- Incorrect recording of instrument readings
- Inconsistent use of measurement units (i.e. psi versus feet of head)
- Failure to correct pressure and flow for rated pump speed
- Blind reliance on flow meter without vetting results
- Omission of overall conclusion as to performance
- Pump performance is inadequate, but pump is still certified
- Insufficient run time of pumps and drivers at 150% of rated flow
- Failure to test emergency starting system
- Failure to test alarms, supervisory and trouble systems
The views expressed in this article are those of its author and in no way represent the positions and views of past, present and future employers, clients or affiliates. This article is for informational and educational purposes only. Recommendations or conclusions in this article should not be interpreted as any guarantee that the reader will achieve the same results.