Pre-action makes most sense to me as well. That is, when goal is to prevent
fire spread to other rooms by fire starting in such vital room.
Pre-action is not really statistically justified to avoid unintentional water
application and wet sprinkler is more reliable in performing on demand in a
The practice of connecting the relief valve discharge to the pump suction has
been accepted for many years.It was removed from NFPA #20 in the nineties
but has since been reinstated.I have done this many times for many reasons
without any problems.Because it is a closed loop,I have not increased
Any problem dumping the relief discharge back into the tank?
Thank You
Rahe Loftin, P.E.
Region 7 - GSA
Office - 817-978-7299
Fax - 817-978-8644
Cell - 817-371-3102
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If the relief valve is installed before the pump check, it's going to effect
your numbers a little when you test.
IMHO, the BEST way to pipe it is as Rahe suggests that way you have a break
and tank circulation (which is a good thing for weekly's).
I assume no bypass but will you have a flowmeter
No. Follow the same rules as you would for discharging a flow meter
back into a tank.
At 09:16 AM 3/20/2009, you wrote:
Any problem dumping the relief discharge back into the tank?
Thank You
Rahe Loftin, P.E.
Region 7 - GSA
Office - 817-978-7299
Fax - 817-978-8644
Cell - 817-371-3102
Does anyone out therte know what the trade-offs Pat is referring to
in the below memo are?
Hello All:
Given the initiatives in some states to forestall the adoption
of the IRC in order to eliminate sprinkler requirements in new 1
2-family homes, I wanted to let you know that there
Other than the turbulence, which was deemed acceptable for the condition
where the relief is piped back to suction under #20, the pipe running from
the tank to the suction side of the pump is the same chamber as the tank-
unless there's a OSY right on the suction nozzle of the tank- and if you're
Yes we have many dry systems. I have never seen one which does not have a
pressure regulator and an adjustable PRV. Most of the adjustable PRV's are
set to relieve any pressure which is 10-15 psi above the set pressure.
Rodney K. Hamm, P.E.
President/Owner
Falcon Fire Protection
Office (478)
Wow what a week..I was at another plant yesterday which has the same exact
problem. This facility has 14 wet systems fed by a fire pump so the static
pressure is maintained by a jockey pump at 170 psi. Several systems had
system pressures 175 psi. One of the gridded systems had a system pressure
Does the plant realize that once all your air is gone that these prv's will be
dribbling water every time the system warms up? Hopefully they have a good
mop-up crew.
Air is the cushion in the system, systems will over pressurize once they have
become water logged and there is no place for
I FULLY INTEND THAT THIS WILL BE MY LAST POST REGARDING THIS SUBJECT. I
promise to make a concerted effort to make this statement true. I would also
like to state that you should probably read this entire post if you have not
completely tuned out regarding this subject!
I obtained my Bachelors
No branding here. Everyone enjoys a spirited discussion now and then. Keeps
the viewer ratings up. lol
Craig L. Prahl, CET
Fire Protection Specialist
Mechanical Department
CH2MHILL
Lockwood Greene
1500 International Drive
PO Box 491, Spartanburg, SC 29304-0491
Direct - 864.599.4102
Fax -
Rodney,
Last week when I posted on the incompressibility of pure water (14.7 psi
to reduce volume 1 part in 5x10^7) illustrated through a hypothetical
temperature swing from 40F to 80F, I thought my statement of BIG
PRESSURE was self explanatory on the massive pressure increase water can
Yes. This building is in an area up north where the temperature drops to -40
to -50 deg.C in the winter. The suction pipe from gravity tanks to pumphouse
is heat traced and isulated. Running relief discharge to tank will be a big
cost. The flow meter runs back to the tank,bu it is too small to
How about a more basic question. Why do you even have a relief
valve? With a rating of only 105 psi exceeding 175 psi with a tank
feed requires a tall tank.
Roland
On Mar 19, 2009, at 11:23 PM, A.P.Silva wrote:
The building owner wants to connect the discharge piping from the pump
Tony made reference to a 4 in. diameter PRV, so I assume he is dealing with
a diesel driven fire pump. The PRV is required for all diesel driven fire
pumps. If the diesel driver rpm increases higher than the set idle position,
the system pressure could easily exceed 175 psi without a suitable PRV.
I had not been following the thread because the subject title hasn't
changed, but am I correct in assuming this problem does not occur with
pressure switches at the top of retard chambers?
James L.(Jim) Roberts, PE/SET
Fluor Corporation
100 Fluor Daniel Drive - C104F
Greenville, SC 29607
True. Good point.
I should've mentioned the pump is diesel. The tank is 40' high. To conform
to NFPA 20, 2007 section 5.18.1.1, 121% of churn gives (105 x 120% x 121%) +
(40 x .433) = 170 psi (approx), assuming churn pressure is 120% of rated
pressure. Someone would have thought it was not too
Thanks. A waste cone and sight glass are included.
Tony
-Original Message-
From: sprinklerforum-boun...@firesprinkler.org
[mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Rodney Hamm
Sent: March 20, 2009 10:26 AM
To: sprinklerforum@firesprinkler.org
Subject: Re: Fire Pump
If it is a relatively new pump, it may churn at 140% but I'd be
shocked if that were the case. I haven't gone looking but has any one
seen a horizontal pump that exceeds the old 120% criteria? The pumps
I've played with have been less than 110% and there are a boat load
that are at or
Yes Jim. Pressure in the retard chamber is relieved through the drain when
the alarm port is closed.
On Fri, Mar 20, 2009 at 10:26 AM, jim.robe...@fluor.com wrote:
I had not been following the thread because the subject title hasn't
changed, but am I correct in assuming this problem does not
Ron:
I checked with the Colorado Div. of Fire Safety, and no decisions have been
made on code adoptions Steve Gasowski of the Div. said he's part of an Ad
Hock committee reviewing this and other code adoption issues, but no final
decisions yet.
Thom McMahon, SET
Firetech, Inc.
2560 Copper Ridge
, P.E.
President/Owner
Falcon Fire Protection
Office (478) 953-1677
Cell (478) 396-6988
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Rodney,
You said you aren't hard headed and you understand the principles behind
the system pressure increases. Here's a chance to prove both.
1. Two containers of identical volume. One container 50% water, the
other container 100% water. Each has been sitting in a 50 F room with
the lid
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