What they are considering is requiring ALL designs be done to the lower
supply, without the Fire Pump running. The situation would for high demand
systems require additional fire pumps, which just seems to be an expensive
fix to a city wide problem. I propose using the lower flow to design up to
the point at which they are sure the fire pump will activate, and then
provide a second calc for all flows required above that point.
If you start asking about current domestic demands ect. there are no real
answers nor anyone to ask. The city doesn't have a city engineer. The guy
that runs the water treatment plant and sewage plant is the only "Water guy"
they have. For years this has been called the "High Pressure" main, which
supplies the airport, and hangers at the airport. The questions started
flying when the inspectors test on the new Terminal addition couldn't call
for the fire pump to activate, and just dribbled water. They solved the
immediate problem by connecting the flow switch to a signal transmitter to
call for fire pump start, but that still has about a 2 min. delay. Now they
are looking at all the Airport systems, because any small fire won't
energize the fire pump. The airport is located over a mile away from the
fire pump.
Our project is half way between the airport and the fire pump, at a new
industrial park (Live work units) connected to the "High Pressure" main
A 4 sprinkler design for the residential portion won't start the pump, but
what about the OH II 3000 SF design area? For the first 350 Gpm the fire
pump won't be on, but for the total design demand it will. That's why I
proposed two calc's, since they tell me the "Normal pumps wouldn't be able
to supply the full 600 Gpm at 20 Psi or more, not to mention the hose
allowance.
Another screwy water system.Water tanks without the elevation to get the
water to the airport, hence they supply the pumps, fire pumps to meet the
"Emergency" demand, supplied from the same tanks. Still trying to find the
pressure settings for all the pumps on this system, and their elevations,
and the various tank elevations.
Thom McMahon
Firetech, Inc.
2560 Copper Ridge Dr
Steamboat Springs, CO 80488-2136
Tel: 970-879-7952
Fax: 970-879-7926
----- Original Message -----
From: "Roland Huggins" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, April 02, 2007 10:19 AM
Subject: Re: Flow test & fire pump
Are they considering IGNORING the pump demand portion of the initial
sprinkler calc since once the fire dept hooks up, the flow is going to
exceed 350 gpm?
Roland
On Apr 1, 2007, at 12:48 PM, Thom McMahon wrote:
We have a municipal water system which operates at 48 psi most of the
time, however when the flow exceeds 350 Gpm the fire pump kicks in and
boosts the system to 145 Psi, @ 2000 gpm. Whenever a flow test is
performed the results are always based upon the fire pump flow.
As we all know most fires are contained or extinguished by one to three
heads. Obviously this isn't enough to make the fire pump kick in.
The local Fire Chief has started to question the operation of systems
installed using the full flow of the fire pump, since even in flow
conditions over 350 Gpm it can take as long as 2 (Two) minutes for the
pump to kick in. The bigger concern as I see it is that the design for
any system up to 350 Gpm should be based upon "NO" fire pump, with two
sets of calculations one for flow up to 350, and another for flow over
350. This way we can be sure that the sprinkler heads will have the min.
pressure and flow even if only a few go off. The other calc should be
easy to prove, as over 350 there will be a large increase in pressure
available. The caveat is that the higher flow calculation cannot be used
to reduce the pipe size below those used for the lower calc. It is just
a "Proof" calc.
Does this sound like the right approach?
No the city has no intention of changing the pump set up any time soon.
Thom McMahon
Firetech, Inc.
2560 Copper Ridge Dr
Steamboat Springs, CO 80488-2136
Tel: 970-879-7952
Fax: 970-879-7926
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