Greg,
Why would you need to flow of an 'open-end' piece of pipe? Is this for
sprinkler system design, or a theoretical problem your trying to solve?
If it's for sprinkler system design, can't you simply solve the problem for
a given flow of say 1000 gpm (in other words set the flow and work backwards
to see what the residual pressure at that flow).?
In other words, if the flow is 1000 gpm, we can subtract the friction loss
in the piping \ fittings from the pressure head to estimate available
pressure at a point downstream from the tank....
Then you would have an estimate of the residual pressure at 1000 gpm flow
(for example)
...there are fitting losses that need to be estimated and, as always, don't
forget to allow for some safety factor...also, I would use the base of the
tank elevation to be conservative.
(I get approximately 3 psi loss in 140 ft of 8", with some allowance for
fittings, low c-factor, etc....This gives the following rough capabilities
of the system...roughly 60 psi static, 57 psi residual, 1000 gpm flowing (at
base of the tank)...to be conservative I would probably go with 60 psi
static, 55 residual, 1000 gpm.)
Elevated tank systems are known for being fairly "flat" curves if you're
tieing into the piping near the base of the tank to feed your system.
Possibly others on this list could confirm or contradict my
calculations\reasoning.
If you are trying to determine the MAXIMUM available flow from this tank
system....and need to solve for the flow in an open end piece of
pipe....then Bernoulli's equation can be used to solve this problem with
reasonable accuracy. (wikipedia has a information on this equation).
(the maximum flow would be at a residual pressure of 0 at the outlet of the
pipe...in other words, all pressure energy converted to flow)
Nathan
Global Fire Engineering, Inc.
Tel: (813) 659-2700 | Fax: (813) 659-2727
[email protected]
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Greg McGahan
Sent: Thursday, August 06, 2009 9:07 AM
To: [email protected]
Subject: RE: water storage tank
I know the static pressure. I need the RESIDUAL pressure and flow through an
open 8" pipe at ground level.
Greg McGahan
Operations Manager
Living Water Fire Protection
1160 McKenzie Road
P.O. Box 877
Cantonment, Florida 32533
(850) 937.1850 | Fax (850) 937.1852 | Cell (850) 554.3231
[email protected]
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Thursday, August 06, 2009 7:28 AM
To: [email protected]
Subject: RE: water storage tank
The formula is: ft of water x .433 = psi
So for 140 ft of head the approximate psi would be around 60 psi, at 70 ft
it would be approximately 30, etc.
Note that this does not account for the loss through the tank outlet, vortex
plate valves or piping loss.
Find out what that 8" is. Especially if it's a plastic. Beware of HDPE.
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 - 864.599.8439
[email protected]
http://www.ch2m.com
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Greg McGahan
Sent: Thursday, August 06, 2009 8:18 AM
To: [email protected]
Subject: water storage tank
We have a situation where a new water storage tank is being installed on a
public utility system and I need some help if anyone can tell me the
following:
New Tank - 140' high
8" pipe (unknown type) going straight to ground level
What is a reasonable expected flow and residual pressure?
Any help would be appreciated.
Greg McGahan
Operations Manager
Living Water Fire Protection
1160 McKenzie Road
P.O. Box 877
Cantonment, Florida 32533
(850) 937.1850 | Fax (850) 937.1852 | Cell (850) 554.3231
[email protected]
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