Fire pumps are an essential component of many water-based fire protection systems. They are used in instances where a building’s demand pressure exceeds the pressure that can be provided by the water supply. They are common in high rise buildings, as well as buildings with large sprinkler demand (high hazard storage, for example). Fire pumps can only be used to increase the available pressure, not the available flow. If there is inadequate flow, a fire pump alone will not be an effective solution – a water storage tank will also be required, often requiring a fire pump as well.
Just as a car needs to get its oil changed or tires rotated, a fire pump also requires preventative maintenance and care. The requirements for inspection, testing, and maintenance (ITM) of fire pumps can be found within Chapter 8 of NFPA 25: Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. A summary of the ITM requirements can be found in Table 188.8.131.52 of NFPA 25, 2014 Edition. One of the tests that is required is the annual flow condition test, which is to be performed by a qualified sprinkler service contractor. NFPA 25 describes the different testing methods that can be utilized for this test.
Three separate scenarios occur during the annual flow test:
- No-flow (Churn): This represents the pump at minimum flow which should not exceed 140% of the rated pressure
- 100% rated flow: This represents the pump’s rated flow at its rated pressure
- 150% rated flow: This represents a pump’s flow at 65% of the rated pressure
These flows are achieved by discharging specific amounts of water through the fire pump test header using approved testing devices that measure the flow and pressure coming from each test port. Once the desired flows are reached, the results are recorded, and they are then graphically represented on what is known as a pump performance curve, which is typically found on a Test Report. Below is a basic example of pump test results.
The Fire Pump Rating can be found on the fire pump’s name/data plate, the Test Results are the results recorded by the service contractor, and the Theoretical Results are what is expected based on the original manufacturer’s specifications. When added to a graph, they typically look as shown below in Figure 1, with the blue line being the Test Results and the green line being the Theoretical Results.
Figure 1: Fire Pump Performance Curve – Performing as Expected
A new fire pump is required to perform in accordance with NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection. The curve provided by the manufacturer is the preferred basis of comparison when determining of a pump is performing as it should. NFPA 25 § 184.108.40.206 and § 220.127.116.11 outline what is considered acceptable when it comes to the fire pump performance test. It states that if a pump yields results less than 95% of the pump’s rated pressure and flow, than an investigation must be conducted as to why the pump is yielding a degraded performance. The example above shows that the pump is within the 95% rated performance meaning the pump test results are acceptable and no further investigation is needed.
The curves in Figure 1 closely resemble one another which is also a good indication that the pump is performing as it should, but the values should still be fully analyzed. If there is an issue with the pump’s performance, the curves will typically look different from one another as shown in Figure 2 below.
Figure 2: Fire Pump Performance Curve – Under Performing
As seen above the test data results deviate more than 5% from the rated performance, and further investigation is needed. During this investigation is when issues with the pump components are typically discovered. The longer an issue is left unaddressed, the more costly the effect could be. An underperforming pump does not necessarily mean a complete replacement is needed, as there are numerous causes for poor performance test results.
The results of the test should be interpreted by qualified personnel who can properly analyze each aspect of the report. In many cases, a thorough analysis of a pump and its performance data can find a relatively inexpensive solution help resolve performance issues. Remember, fire pumps are an important part of the life safety system in a building, so proper performance is key.
If you have questions on fire pump testing, or need assistance with reviewing fire pump test results, please contact us at firstname.lastname@example.org or 617-500-7633.