Thread: Water Supplies/pump Operations
07-29-2004, 06:57 PM #1
- Join Date
- Jul 2004
Water Supplies/pump Operations
ACORDING TO IFSTA THEY SAY TO MAINTAIN AT LEAST 20PSI OF INCOMING PRESSURE ON THE COMPOUND GAUGE TO AVOID COLLAPSING THE LINE.ASSUMING ALL THE GAUGES ARE IN WORKING ORDER WHY WOULD A HYDRANT SHOW 40PSI (GAUGE ATTACHED TO A 2 1/2 OUTLET) RESIDUAL PRESSURE AND THE PUMP COMPOUND GAUGE SHOW ZERO? THE 5 INCH HOSE CONNECTED TO THE PUMPER IS HARD AS A ROCK.
07-29-2004, 07:53 PM #2
Sounds like the intake valve is closed or a bad guageBuckle Up, Slow Down, Arrive Alive
"Everybody Goes Home"
07-29-2004, 08:08 PM #3
I'll go with mtnfireguy on that one you might want to also check your tank fill valve to make sure it is shut. Also youre relief valve may be stuck open.
07-30-2004, 02:30 AM #4
- Join Date
- Feb 2003
- Fairfield, CA
First, it is necessary to know:
(1) the flow rate when this occurred,
(2) the length of the 5" hose (20 ft or 1,000 ft),
(3) where is the compound gauge taped into the internal piping (i.e., very close to the pump suction or some distance away).
(4) the diameter, length, and number of elbows in the internal piping from the suction inlet to the pump suction.
(5) the type and diameter of the intake valve (butterfly valve or gate valve)
(6) the elevation difference between the hydrant gauge and the compound gauge.
A proper answer cannot be provided with these 6 additional pieces of information.
As mtnfireguy suggested, one or both of the gauges may be out of calibration. If you are reading the hydrant pressure with a 2" diameter gauge with a 0-300 psi range, throw it away - it’s useless. Get some good gauges (i.e., 1% Full scale accuracy, 3.5" diameter, a range of twice the expected pressure, and liquid filled - typically glycerine). I suspect that most of the compound gauges used are out of calibration. Get a good gauge and connect it to the test port and ignore the compound gauge. If the new gauge is not a compound gauge watch it carefully as it nears 0 psi.
It may be (assuming the gauges are accurate) that everything is normal. The 40 psi at the hydrant can be considered a “starting” pressure. From this you must subtract the hydrant exit loss, the pressure loss in the hose, the pressure loss, at the suction intake (including the intake valve), and the pressure loss in the internal piping and fittings.
07-30-2004, 10:58 AM #5
07-30-2004, 12:17 PM #6
1) Please don't type in all caps. It's hard to read and a breach of "nettiquete"
2) The 20psi is a good starting point -- both for hydrant operations and hose relays. It gives you time to react if someone opens up another large discharge (say a 2.5" that whose nozzle was shut-off), or if someone hits another hydrant. It also gives nearby users some residual pressure to use, and hopefully keeps the number of sprinkler flow alarms going off (from drop in pressure) to a minimum. It's not a "hard" number -- if you understand your hydrant system and know it's limitations and what happens when you do bring it below 20psi it can be done. For hose relay operations, it's a good number to start with, and once the fireflows are stabilized you can drop below 20psi intake to maximize the throughput of the relay.
You won't actually collapse the line even at 1psi intake -- but if your start flowing more on the outbound side (opening a nozzle) or if you lose just a bit on the supply side (someone hits another hydrant) then you see some flat hose real fast.
3)ASSUMING ALL THE GAUGES ARE IN WORKING ORDER
Ok. Still check the damper valve!
WHY WOULD A HYDRANT SHOW 40PSI (GAUGE ATTACHED TO A 2 1/2 OUTLET) RESIDUAL PRESSURE AND THE PUMP COMPOUND GAUGE SHOW ZERO? THE 5 INCH HOSE CONNECTED TO THE PUMPER IS HARD AS A ROCK.
a) Your intake is closed and you're not flowing water through the 5"
b) You're flowing through an incredibly poorly plumbed or plugged intake:
b1) Poorly designed front-mount suction, say single 2.5" or 3" piping with multiple bends. You have plenty of extra water on the inlet side (the hard hose shows that), but you're sucking it through a tiny straw (which is why you have 0 psi by the time it gets to the pump & compound guage area) -- that tiny "straw" of piping is your limiting factor.
b2) You have crap plugging the intake screen at the pump's steamer connection itself -- again, plenty of water but it can't get to the pump.
b3) The valve on the LDH intake on the steamer connection isn't opening fully, again restricting the flow.
In any of the "b" scenarios, you should be flowing a lot less than either the pump capacity and/or hydrant is.IACOJ Canine Officer
08-12-2004, 07:11 AM #7
Is it possible that the inner liner on your LDH came loose?
Did you find out the cause yet?Train like you want to fight.
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