-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Reza
Esmaeili
Sent: Tuesday, September 04, 2007 3:28 AM
To: [email protected]
Subject: RE: Fire Pump Selection - REVISED
Richard,
Many thanks for your great explanation. I think my previous question about
selecting of fire pumps was a bit confusing, so I revised it as below.
- Actually this is for a big deluge system, not sprinkler system, I
mistyped sprinkler system in my previous email.
Let me ask my question in another way. I want to asume 3 scenarios for
selecting fire pumps for a water demand of 3900 GPM at 90 Psi.
1- Want to be economical and and I don't afford to buy reserve pumps: (is
it allowed as per NFPA not to have reserve pumps)?
If you are referring to basic NFPA 13, 15, 20, etc. requirements, a reserve
pump isn't required although if you have an electric drive without a
reliable power source, maybe in that case you could say you need a reserve
(i.e. diesel drive) although I wouldn't look at that way. One supply (water
supply + pump in this case) is required and satisfy with diesel or electric.
I'm not sure if there is an occupancy type NFPA standard that requires a
reserve pump (I would doubt it, but I'm not familiar with every NFPA
occupancy type standard)
1-1: I have a very reliable power source: I will buy only an electric
driven main fire pump 3500GPM at 102 psi working at about 112% of rated
capasity ( I won't buy diesel, because I have a reliable power source and
also I want to be economical)
1-2:I doN't have a reliable power source: I will buy only a diesel fire
pump 3500GPM at 102 psi to work as my main fire pump.
1-1/1-2 sound OK
2- have too much money, I will buy reserve pumps:
2-1: I will buy a main electric pump 3500GPM at 102 psi and a diesel pump
3500GPM at 102 psi and my eletric fire pump would be main pump and diesel
pump would be reserve pump which will work at power failure conditions.
2-2: is above arrangement as per NFPA? or I should arrange diesel pump as
main? Either is OK per NFPA from my perspective. If you're only concerned
about power failure, the diesel drive addresses that and the electric would
be unnecessary (diesel is your main AND reserve). If you are looking at
reliability more broadly, an electric paired with a diesel probably provides
some increase in reliability (diesel addesses power availability and
electric addresses the some of the inherent complexity in the diesel drive)
3- Want to be very very economical: I don't want to buy expensive pumps
like Pattreson, Peerless, ... who are producing big pumps, I want to be very
economical and buy the cheap pumps from my supplier who can't make a 3500
GPM pump, so I have to split the pumps and buy two sets of 1500 GPM at 129
psi working at about 130% or rated capacity.
3-1: I have a very reliable power source: I will buy 2 electric pumps each
1500 GPM at 129 psi working as main pumps. Sounds OK, nothing stops you from
using 2 50% pumps in my opinion.
3-2: I doN't have a reliable power source: I will buy 2 diesel pumps each
1500 GPM at 129 psi working as main pumps. Sound OK,
3-3: I am not 100% sure about reliability of power source: I will buy one
electric pumps and one diesel pump at the same capacity of 1500 GPM at 129
psi, electric pump will start first and when water demand exceeds than 1500
GPM, then diesel pump will start, this arrangement is because in case of
power failure, I can supply at least 50% of water demand to control half of
fire. I know this is not logical, but imagine that power failure possibility
is less than 1%. Wouldn't agree with your logic here. 50% supply for a
deluge system isn't of much use. Particularly with the deluge systems, have
to meet or exceed the demand or the protection isn't there.
Regarding the 2 pumps, if you're demand is down to 3900 gpm, you could
likely make that work with a single 3000 gpm. That's nothing that
extraordinary. I would be looking at my estimates for installed cost and
life cycle costs as well for a single vs. 2 pumps. I thnk typically the
owner would be better off with a single 100% pump vs. 2-50%. Good luck.
Would you kindly please analyze these three scenarios and let me know if
any of them is aganist NFPA? If you have to choose one economical choice
(among item 1) and one non economical choice (among item 2), and one very
economical choice (among item 3), which ones you will choose?
Many thanks for your kind help in advance.
Thank,
Reza
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