August 30, 2017
Fire Pump Maintenance
By Wills LaCrosse
Fire Pumps are a critical safety item in facilities across the world. Their purpose is to make sure a building has enough water pressure in case of a fire emergency. Of course, the hope is that they are never needed but if they are they need to perform reliably.
Fire Pumps are typically tested on an annual basis. In addition to flows and pressures the mechanical integrity needs to be verified. I typically see the same pumps year after year, however, I am also often called out on pumps I haven’t inspected previously.
There are two standards currently in use for Fire Pumps.
- NFPA 20 for new construction
- NFPA 25 for ongoing maintenance
Section 6.5.2 NFPA 20 states that pumps and drivers that are coupled should be aligned in accordance with manufacturers specifications and the Hydraulic Institute Standards for Centrifugal, Rotary and Reciprocating pumps. Section 220.127.116.11 NFPA 25 indicates that angular and parallel (offset) alignment of the pump and driver shall be checked during the annual test and that any misalignment shall be corrected.
Here is an example of an alignment check done before the annual flow test. The coupling manufacturer’s maximum allowance was 2.6 mils/in angular and 16 mils offset. The initial check revealed that the misalignment was over 3X the manufacturer’s limit. A precision shaft alignment using the Fixturlaser GO Basic laser system was performed and took less than 30 minutes. The final alignment was left within widely accepted precision tolerances for an 1800 RPM machine (0.7mils/1” angular, 4.0 mils offset) and well below what the coupling manufacturer called for. Both results are shown below.
I also utilize the Hawk Supervisor to check the mechanical condition of Fire Pump Systems. The Hawk allows me to check the initial condition and the final condition of the system. I receive a diagnosis at the machine in about 10 minutes. Data is compared to ISO specifications and the over health is reported. If problems exist I am given a diagnosis, what it thinks is wrong and recommended corrective actions.
In this example, the initial diagnosis was a bad outboard bearing which required replacement.
The thrust bearing was replaced and the system aligned and a final scan showed everything was acceptable.
In summary, the alignment condition of fire pumps needs to be checked and corrected, if needed, anytime a Fire Pump is serviced. New tools also allow us to not only determine the health of the fire pump but give recommendations on corrective actions.
Save Time. Save Money. Save the Machine.