Pump Pressure How Much Over 175 psi??

[LCREP]

I seem to be seeing fire pumps test reports with churn pressures of 175 psi and greater the last few weeks. I know the max is 175 psi unless the sprinkler/standpipe components are rated higher. The question is how much higher will you go before you will not accept the system? My feeling is anything over 185 psi is a stopper for me on existing systems and 170-175 psi on any new jobs . What is your number???

Oh yea I get to pay for the water damage via a coverage known as sprinkler leakage when it goes bad!


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Fire Sprinklers Save Firefighters’ Lives Too

Not ALL Sprinkler Systems Are Created Equal! An Inadequate Sprinkler Design Is JUST As Bad As A Nonsprinklered Building!! When Occupancies Change So Should The Sprinkler System. See NFPA 25, 2002, Edition, Section 4.1.5, 4.1.6 & 4.1.6.1.

 

[TravisMack]

Figure out what the lowest sprinkler elevation is...the sprinkler is likely the only component in the system that is limited to 175 psi. So, if the sprinklers are at 30' above the pump discharge gauge, then you could be safe with the pump discharge at ~188 psi.



Travis Mack
MFP Design, LLC

 

[LCREP]

Mack,

I see OS& Y and butterfly valves stamped 175 psi on the discharge side of the pump, why is this not a concern?



****************************************
Fire Sprinklers Save Firefighters’ Lives Too

Not ALL Sprinkler Systems Are Created Equal! An Inadequate Sprinkler Design Is JUST As Bad As A Nonsprinklered Building!! When Occupancies Change So Should The Sprinkler System. See NFPA 25, 2002, Edition, Section 4.1.5, 4.1.6 & 4.1.6.1.

 

[TravisMack]

Sorry...then, it may be an issue. All of the valves my sprinkler contractors use are 300# valves. I guess I just got in the habit that the valves are 300#. If you have 175# valves, then you have a valid concern.

Travis Mack
MFP Design, LLC

 

[stookeyfpe]

I don't know if this helps but here goes:

If your valves have flanged fittings they should meet ASME B16.5. I seem to recall that a 150 pound flange is rated to 285 PSIG at 70F.

Is the data you want or am I getting less intelligent as I am getting older?

If you need yield data on pipe wall thickness based on fabrication I also have that data at atmospheric normal temperature and pressure.

 

[FFP1]

Sections 5.7.4.1 and 5.18.1.1 in NFPA 20 both indicate that "the net pump shutoff (churn) pressure plus the maximum static suction pressure, adjusted for elevation, shall not exceed the pressure for which the system components are rated". YES, both sections use the word "SHALL". The key question you should ask is whether or not the rated pressures for any of the system components are exceeded after "adjusting for elevation".

It is very common for a significant portion of the components (sprinklers, valves, pressure switches, flow switches, pressure relief valves, etc.) to be rated at 175 psi OR have verbage which indicates the warranty is null and void if the component experiences pressures exceeding 175 psi.

I tell my customers the max system pressure should be 175 psi.......if your system demand requires a static pressure abive 175 psi, I suggest a thorough evaluation of the design, storage heights, k-factors, etc.

As a sprinkler contractor and FPE, I am also concerned about water damage if I do not properly advise my customers. However, giving the manufacturer an out clause by voiding the warranties of the system components is just as concerning.