A great explanation. The only thing to add is that the fire pump alarm signals and controller functions must be tested as well per NFPA 25. Almost no one does that.
The only time I would apply affinity would be with a variable speed controller (VFD-PLD) because speed is what i is but also how well the mfgr matched the driver to the pump.
I test a fire pump that consistently has a high churn pressure (140 PSI plus as compared to the factory churn of 116 PSI) The 100 % is always around 90% of the factory 104 PSI at 94 PSI and then the bottom falls out at the 150% point (Factory at 87PSI to the annual test pressure of 58PSI which is well below the 90% requirement). This is a vertical turbine pump with a raw water source. Normally I get a -3PSI for the supply pressure as the water level is usually around 6.5 ' from the surface of the water to the C/L of the discharge on the pump. The curve on the graph is always convex instead of concave. Would you be able to direct me to a corrective coarse of action that would help resolve this. The pump rating is 1,000 GPM @ 104 PSI with 1770 RPM. My RPM readings are around 1785 at churn, 1777 at 100% and 1774 at 150%. Yes, I do have my gauges calibrated annually.
Dennis, thanks for the great questions. Can you get a borescope inspection of the bowls? The experience I have with VT fire pumps is that either a blockage of weeds and branches formed or one or more of the lifting bowls was damaged or missing. In those days we pulled the vertical impeller. Possibly a borescope would give you confidence to look elsewhere or actually find an issue.
What if corrected test result shows that test curve is above the pump OEM curve...what is the interpretation for such result? will 5% apply to going above the OEM curve as well?
The NFPA 25 committee was not concerned with pumps performing above the curve. They weren’t even interested in meeting the largest system demand. The manufacturers reps on the committee were just looking for a way to monitor wear on the impellers. (Check that the driver is at an appropriate RPM.) The 5% was never about reducing risk. Risk was never discussed. Where did it come from? It was made up.
Very easy to understand! Good information! I will watch again to reinforce learning. Thanks
Chuck Worrell FireSafetyConcepts
I glad you liked it. Thanks. 😊
A great explanation. The only thing to add is that the fire pump alarm signals and controller functions must be tested as well per NFPA 25. Almost no one does that.
Great points! Thanks.
very useful explaination
Thanks Kindly.
Very informative 👍
Great video and explanation! Reach out to Hose Monster if anyone has questions on how to perform a test.
Thanks for contributing!
This was really amazing,
A great Explanation thank you.
The only time I would apply affinity would be with a variable speed controller (VFD-PLD) because speed is what i is but also how well the mfgr matched the driver to the pump.
I test a fire pump that consistently has a high churn pressure (140 PSI plus as compared to the factory churn of 116 PSI) The 100 % is always around 90% of the factory 104 PSI at 94 PSI and then the bottom falls out at the 150% point (Factory at 87PSI to the annual test pressure of 58PSI which is well below the 90% requirement). This is a vertical turbine pump with a raw water source. Normally I get a -3PSI for the supply pressure as the water level is usually around 6.5 ' from the surface of the water to the C/L of the discharge on the pump. The curve on the graph is always convex instead of concave. Would you be able to direct me to a corrective coarse of action that would help resolve this. The pump rating is 1,000 GPM @ 104 PSI with 1770 RPM. My RPM readings are around 1785 at churn, 1777 at 100% and 1774 at 150%. Yes, I do have my gauges calibrated annually.
Dennis, thanks for the great questions. Can you get a borescope inspection of the bowls? The experience I have with VT fire pumps is that either a blockage of weeds and branches formed or one or more of the lifting bowls was damaged or missing. In those days we pulled the vertical impeller. Possibly a borescope would give you confidence to look elsewhere or actually find an issue.
Thanks for the insight, once I get consent to proceed, I'll get back to you on the results.
What if corrected test result shows that test curve is above the pump OEM curve...what is the interpretation for such result? will 5% apply to going above the OEM curve as well?
The NFPA 25 committee was not concerned with pumps performing above the curve. They weren’t even interested in meeting the largest system demand. The manufacturers reps on the committee were just looking for a way to monitor wear on the impellers. (Check that the driver is at an appropriate RPM.) The 5% was never about reducing risk. Risk was never discussed. Where did it come from? It was made up.
Thank you sir.
You are very welcome! Next video will be about lube oil system risks.
Thank you. Every plant should watch 😅