Usage of Existing Fire pumps

[Sengathirselvan]

Hi,

In one of our projects, there is an opportunity to shift a slightly older pump (say one year) to adjoining new facility.

The rated flow rate of the pump is 1000 gpm @ 160 psi. The demand flow rate at the new facility is 1250 gpm @ 101.5 psi. While testing, it is found that the existing pump delivers 1250 gpm, 110 psi.

Though the performance meets the requirement, we are at disadvantage that the name plate details of the pump do not meet NFPA requirement. Is it still acceptable?

Thanks!!

 

[LCREP]

Depends....

Some insurance carriers i.e. Factory Mutual will require the fire pump to meet the system requirements at 100% of the pump output.

As per the 2013 NFPA 20 handbook

Maximum system demand flow should be between 90% and 140% of pump’s rated capacity, but, in no case, greater than 150% of the pump’s rated capacity.


Another thing to consider....If the new system doesn't have a backflow device and you need to add one, depending on the type required it can reduce the pump pressure by 5-15 psi.

You will need a full acceptance test on the pump when installed.

 

[MatthewJWillis]

Concur. I do not think the pump test satisfies pump rating...

 

[stookeyfpe]

The fire pump is compliant so long as it meets the required demand within the rated pressure limits based on NFPA 20 Section 4.6.2.3.1 (2013 edition). The nameplate is the permanent record of the pump's rated rated flow rate and pressure - it isn't a maximum limit. The maximum limits in NFPA 20 are based on if the pump is a centrifugal or a positive displacement design.

Your pump is compliant under the 2012 International Fire Code.

 

[SprinklerDesigner2]

The way I have always understood it all the rated capacity, the 150% of rated capacity at 65% of rated pressure is simply presented as the minimum performance in order to achieve UL listing or FM approval.

A pump rated at 100 psi must deliver at least 65 psi discharging at 150% of its rated capacity. This is not directed at the designer to use these pressures but simply at the pump manufacturer.

I feel safe in saying all UL/FM pumps will do better then 65% of rated pressure @ 150% of rated capacity. While I am guaranteed a 100 psi pump will deliver 65 psi @ 150% of rated capacity my gut feeling is it would be rather on the safe side to "assume" we'd most likely get 75% and one of my favorite 100 psi (1,250 gpm) pumps gives me 92 psi at 150% and you can see this in the factory certified curve.

As I understand it I can certainly use that 92 psi @ 150% of rated capacity as long as I follow the factory certified curve.

Let me back up a bit.... I used the term "assume" above but while we can all assume a listed fire pump will do better, and sometimes a lot better, than 65% of its rated pressure there is no way I would use another number unless 1)I had the results of a properly run pump test with certified gauges (pet peeve of mine) or a certified factory curve.

Oftentimes on a large project with a pump I won't so much shop for a pump based on price but on the curve. Sometimes you can have 20 psi more than your competitor just by shopping the curve and not the pump.

Am I right?

 

[LittleInch]

The problem will be that yes it can do the demand flow, but can it do the required over flow (140-150%) within the requirements.

Maybe yes maybe no - would need a good look at the pump curve and motor power required / motor rating

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bmlxd40]

I agree with your comments SD2. I Shop curves the same way.

 

[mk3223]

A high possibility is that the existing pump won't meet the NFPA requirements, in terms of the head/flow. Besides, it may need to add on all the instrument and control for the pump to meet all requirements. It seems that the basic fire water system is existed, and this is a add-on to comply the additional flow as needed. Instead of buy a new NFPA pump, you may seek the comment from your Fire Chief for accepting the equipment. The bottom line is that it is to improve the system safety and reliability with the minimum investment.