Please read 5.7.6 where my former post says 5.7.4.
My apologies.
Frans Stoop
Date: Tue, 30 Oct 2007 14:32:58 +0100
To: [email protected]
From: Frans Stoop <[EMAIL PROTECTED]>
Subject: Re: Fire Pump performance as per the name plate
Dan,
NFPA 20-2007 paragraph 11.2.4.1.1:
"Engines shall be provided with a governor capable of regulating
engine speed within a range of 10 percent between shutoff and
maximum load condition of the pump."
Does this help: paragraph 11.2.4.1.2
"The governor shall be field adjustable and set and secured to
maintain rated pump speed at maximum pump load." ?
The pump in concern should have a pressure relief valve installed
per paragraph 5.18.1.1:
"Where a diesel engine fire pump is installed and where a total of
121 percent of the net rated shutoff (churn) pressure plus the
maximum static suction pressure, adjusted for elevation, exceeds the
pressure for which the system components are rated, a pressure
relief valve shall be installed."
If the water supply has its own storage tank(s), you may be able to
solve the problem by piping the discharge side of this relief valve
back to the water storage tank.
Although, note that paragraph 5.7.4.2 5.7.6.2 does not allow to use
the relief valve for this purpose:
"Pressure relief valves shall not be used as a means to meet the
requirements of 5.7.4.1 5.7.6.1."
You may also find other useful text in section 5.7.4* 5.7.6*
Maximum Pressure for Centrifugal Pumps.
like paragraph 5.7.4.1 5.7.6.1:
"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."
It says "net pressure" , no 5% allowance mentioned.
Frans Stoop
TOS architecture & fire protection
Netherlands
At 10:20 30-10-2007 +0200, you wrote:
Dear All,
I have got a problem with a fire pump.
The pump performance does not match the name plant data.
The cause is the Diesel Engine.
The engine RPM deviation from "No Load" to 150% nominal is 90 rpm, just over
5% of the nominal (1760 rpm).
The result is too high pressure (5% excess) at churning causing operation of
the 175psi relief valves of the sprinkler systems,
At the other end, 150% flow, the pressure is 5% below the name plant data.
The question: To what extent the pump supplier is bound by the name plant
performance data.
The supplier Rep. argues that 5% deviation is within the normal.
Dan Arbel
Tel: 972-4-8243337
Fax: 972-4-8243278
M: 972-52-2810593
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