Thread: Maximum distance for 5"
11-01-2008, 05:44 PM #1
- Join Date
- Nov 2004
- Staten Island
Maximum distance for 5"
what is the recommeded distance for 5" hose in a supply stretch or relay between engines? hydrants are rated 1000 gpm+ and engines have 1500 gpm pumps.
11-01-2008, 05:52 PM #2
- Join Date
- Oct 2002
- New Jersey, USA
I was always told 800 to 1000 feet max. I believe it is due to the fact that if relaying from one engine (positioned on the hydrant) to a second engine you would have to pump over the rated pressure for the hose to deliver full GPM to the second engine if it was over 1000 feet. I'll look into it and get back to ya... 5" is volume not pressure, it delivers a very high volume of water at lower pressures with low friction loss...
11-01-2008, 07:05 PM #3
- Join Date
- May 2006
- Bryn Athyn, Pa.
Should any engine in the relay suffer a failure, the the distance between between functioning engines becomes 2000' and friction loss increases to 140. Add 50, and you have 190 psi which is still doable for even a 1000 gpm engine (remember, we're dealing with NET pump pressure). Admittedly, this is 5 psi over the 185 psi that most 5" supply hose is supposed to be pumped at. The fix for that is to back off to 185 psi. The next engine will be receiving 40 - 45 psi, still well within a comfortable margin, and the 1000 gpm objective is still being met. There will also be some loss involved in blowing the water through the pump of the failed engine, but it should not be enough to cause the objective (1000 gpm) to be missed.
The task force's normal practice is to put a relay valve (Humat, Z-valve), Hydrasist, 4-way) at each engine in the relay. That way, in the event of a an engine in the relay does fail, another engine can be brought in and hooked up without shutting down the relay. Again, there will be some loss through the relay valve, but also again, not enough to take the flow below the objective.
Stay safe out there, everyone goes home!
Last edited by chiefengineer11; 11-01-2008 at 07:08 PM.
11-01-2008, 08:14 PM #4
There is no such thing as a hard and fast maximum distance. As long as you don't exceed 200psi, you can pump as far as you want. On flat ground flowing 1000gpm, you are limiting yourself to about 1,800ft to maintain 20psi on the intake. You can work with less GPM and PSI and therefore more length to your heart's content.Even the burger-flippers at McDonald's probably have some McWackers.
11-01-2008, 09:49 PM #5
- Join Date
- Jan 2007
- Pa Wilds
Deciding on LDH hose loads
As referenced by others on this thread, and many threads in these forums.... There is a great difference among types, weaves & suppliers of LDH. Conservative friction loss tables for double jacket hose with very little stretch in diameter you could expect to have 15 to 18 psi per 100 ft at 1500 gpm flow rates. Snaptite / Ponn supplies a hose with sizeable changes in diameter when the hose is pressurized. Since the friction loss in hose is inversely proportional to the diameter of the hose raised to the 4.87 power, this stretching can result in a major reduction in friction loss. The Ponn extruded might be as low as 10 psi per 100 ft. at 1500 gpm.
5 in. LDH frequently has an annual test pressure of 200 psi, and consequently it is suggested that pump operators do not exceed 180 psi on the fireground as a safety factor. Using this (180 psi) as a maximum and allowing an incoming pressure of 30 psi at the attack or relay engine, a friction loss of 150 psi can be accomodated. Somewhere between 1,000 and 1,500 feet can safely be pumped at 1500 gpm. It would be best to test your particular brand of hose on the drill ground.
While you might think of this as maximizing the flow, most dwelling fires won't require flows much in excess of 500 to 800 gpm. The Iowa formula suggests a flow of 1 gpm for every 100 cubic feet of fire volume. A 50' by 40' three story frame constructed home would need only 480 gpm. Assuming one exposure, this will get you about an 800 gpm requirement. This low flow, supplied at 180 psi, can be pushed 3,700 feet through the 5" and still have an incoming pressure at the attack engine of 30 psi. The proper place to begin your assesment of engine, hose, and tactics is to examine the fire problems that your community presents. While SFD's are a problem, you might want to take some serious looks at any work places that provide significant employment. Some portion of the justification for equipment purchases can be made by determining the monitary loss to the community if a place of employment were lost due to inadequate application rates.
If you are faced with large flow requirements and are blessed with hydrants every 500 ft, then you might be able to justify engines of 2,000 gpm. That is, if your water company has been progressive enough to install mains that can support 2,000 gpm flows. 5" LDH can flow 2,000 gpm through 600 ft with losses of around 150 psi. For a period of time in the past (1992 to 2003) our SOP was to supply two attack engines (1250 gpm) with a single large engine (2,000 gpm) on a short lay of 400 to 500 feet. This arrangement consistently supplied total flows of about 2200 gpm from hydrants with 40 psi residual at that flow.
Good Luck with your project.
11-01-2008, 11:50 PM #6
- Join Date
- Dec 2002
- Central NJ
11-02-2008, 12:57 PM #7
- Join Date
- Sep 2006
- Northeast Coast
11-17-2008, 11:30 AM #8
A lot of variables exist in using LDH or other hose line for supply.
The spacing for the hydrants should be considered the department should take in before they buy any supply line. If you are in a city, most hydrants are spaced usually no more than 300 to 400 feet apart, with some even less that that.
What else are you going to use this hose line for?
Generally speaking a lay out of 800 ft for 4 inch is considered the ideal lay. The 5 inches can be laid another 400 feet on a good water source without have to worry about water problems.
Of course, if you can lay out two different supply lines from different sources, you would be able to operate on the fire ground in a more efficient manner.
Plus if one supply line or pumper should malfunction, you will not be standing there with I screwed the pooch look on your face!!
Stay Safe and Well Out There....
Always remembering 9-11-2001 and 343+ Brothers
11-20-2008, 07:24 AM #9
- Join Date
- Aug 2006
Our standard is.....
When the total pump pressure to achieve the required volume reaches the pressure required to achieve maximum pump rating, then you have reached your maximum length.
This can be calculated using the friction loss formula for your supply hose, and knowing your pumps rating. For example, if your pump achieves it's maximum rated capacity at 150 psi, then that will be your limiting pressure in the relay.
If you are using a 5 inch supply line with a friction loss coefficient of .08 then the total length is calculated thus...
FL is friction loss, C is the coefficient of your hose, Q is flow and L is length, TPP is total pump pressure. (Q^ is Q squared)
Q and L is in 100's
Assuming a required flow = 1400 gpm
Assuming a required residual pressure = 20 psi.
FL = .08 x 14 x 14 x 8 = 125
TPP = 145
Therefore your length limit will be between 800 and 900.
If the required flow was 2000 gpm then the limit would be 400 ft:
FL = 0.8 x 20 x 20 x 4 = 128
TPP - 148
Of course, everyone will do this different, and have different methods. We have these MAXIMUM limits pre calculated and posted for ready access. And, on the fireground many will just pump by the seat of their pants. And, the longer the relay, the more residual we require.
Your mileage will vary... this is more theory than put to use I believe. We actually seldom need relay beyond a pumper at the hydrant pumping to the attack pumper.
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