Flow meter by-pass on fire pumps 3

[Norm01]

We have been designing quite a few fire pump systems lately and in the past have usually specified the typical test header arrangement (flowing water through 2.5" hose valves) for testing purposes. I am wondering though if going forward we should also be specifying a closed-loop metered by-pass (using a flow meter) in order to cut down on the amount water that is used. Instead dumping a large amount of water to watse every year, this amount could be cut back to every three years (per NFPA 25). Any thoughts or comments?

 

[LCREP]

My 2 cents from an insurance point of view.

Next time you do a pump test via a meter, shut the valve to the suction side of the pump while doing the test, see if you can tell the valve is closed based on pump performance, you will note no difference.

How many contractors send the flow meter back to the factory to be calibrated???

Remember NFPA 25 is a minimum code.

So why did I spend $100K to put this fire pump in again??? One closed valve it is all for nothing. What is a few 1000 gallons of water, compared to what will be needed if the pump does not work in a fire?

Leave the meter out!

I have seen way to many installs in office buildings basements where they put the meter in and no test header at all. How did they do a pump acceptance test with this configuration???


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Fire Sprinklers Save Firefighters’ Lives Too!

 

[TravisMack]

I have seen a few cases with a flow meter and no test header, but the job had standpipes and the standpipe system was used to test the fire pump.

Personally, I don't like flow meters and want to the the water from the hoses. Maybe I am old school. However, flow meters are being used in many installations, so I had better get used to them.



Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[SprinklerDesigner2]

In my opinion flow meters are worthless. Matter of fact they are worse than worthless they can lead someone to believe everything is fine for three years while it isn't.

As LCREP suggested next time you do a pump test close tapping valve on the city watermain then back it off three turns and everything will appear just fine. In the meantime the owner paid $2,000 or more for a piece of worthless junk.

I can not think of an instance where a flow meter would be beneficial. A pump in the middle of Death Valley taking suction from a ground storage tank? Instead of spending $3,000 on a worthless flow meter why not rig (weld) something up at the roof hatch where playpipes be positioned to shoot water back into the tank if water is critical?

If you haven't been specifying flow meters then you've been doing a great job! (My two cents)

 

[ContractorDave]

I assume you are speaking of flow meters installed in a by-pass loop where you have a positive municipal supply as opposed to one installed open ended or back to a fire water tank. But even then, I have to agree with LCREPs remark regarding calibrated meters. We're required to calibrate our test gauges annually after all.

I did a flow test today though on (2) 2000gpm pumps. In this day and age there are other mitigating factors that have to be taken into account also: in this case, what to do with 8-12,000 gallons of water (from an environmental impact as well as just the mess it can make), and, if it's domestic water or clean fresh water, this is now being frowned upon more and more as an unwarranted waste.

I'm thinking flow meters are here to stay and we need to figure out how to work with them, or rather, how to make them work for us.

Regards
Dave

 

[DavidCR]

In NFPA 20 (I don´t have the last edition), it requires that flow testing should be done with actual water discharge every 3 years, so closed loop metering should be complemented with test header, or meter discharging back to the tank.

I think that if water is going to be precious in the future, the NFPA should give more attention to flow meters.

In some cases the AHJ here in Costa Rica consider that depending on the case a pump above 2500gpm is a candidate for meter, due to the difficulty on handling water mess. We have a power plant with a 3000gpm pump design and they asked for both, flow meter with discharge to tank and test heather.