Hose testing

[RFDACM02]

I know this has been posted here before but the search function seem to be dead, so here goes:

Can anyone explain why NFPA 1962 states that you should not exceed 300 feet in any lay of hose when performing a service test?

I know I've seen this before, but don't know that I've see a reasonable answer.

[BC79er_OLDDELETE]

Maybe because if it blows the resulting pucker factor of those standing around would be too high?

Can't remember enough physics right now but maybe the pressure disappates too much after a certain point so the test would be unreliable. Can't say I ever thought about it, we usually only run 100' at a time because of limited testing space in the parking lot.

[sdff1520]

Don't know why for sure either. From a practical standpoint I can tell you that when we test hose we test 4 seperate 300ft lenghts at a time (1,200ft total) and after you fill the hose with water then bleed air it takes a fair length of time to bring the whole works up to test pressure. I can't imagine how long it would take if you added another 400 ft or so to the equation.

[Dave1983]

Maybe because if it blows the resulting pucker factor of those standing around would be too high?

That and I cant imagin its good for your pump.

[hwoods]

Well............

We run with split beds of Three inch supply line (800ft. each). We lay out all of one side, test it, pick it up, then start over again with the other side. We have had no problems with doing that.

Side Note: DAVE!..... You don't have to work the pump any harder just because the line's longer. There is no Friction loss when there is no flow. I charge the line at hydrant pressure, with a person on the nozzle to bleed all the air out. When that's done, lay the nozzle down and bring the pressure up on the pump. Works for me.

[FlyingKiwi]

Blimmin Signtists always have an answer.

Why not put a plug in the middle and test both at the same time Harve?

[LtLTSmash]

i dont know if this is much of an answer, but it seems practical. the reason we don't exceed 300' cause that's the maximum distance we can go without having to block the street, when you lay the hose on the sidewalk. but i doubt the NFPA would use that as their standard.

[jtstoney]

Hose testing

RFDACM02,

One of the main reasons NFPA and manufacturers limit it to 300" max is the stored energy in the hoses. The longer they lay, the more volume of energy that is stored.

In a failure, the shorter length is a lot less dramtic and hazardous

Put it this way,

Would you rather be holding a 50' or 600' hose when the nozzle coupling fails.

JT

[RFDACM02]

RFDACM02,

One of the main reasons NFPA and manufacturers limit it to 300" max is the stored energy in the hoses. The longer they lay, the more volume of energy that is stored.

In a failure, the shorter length is a lot less dramtic and hazardous

Put it this way,

Would you rather be holding a 50' or 600' hose when the nozzle coupling fails.

JT

You lost me here. Do you me the longer the hose lays on the ground with pressure in it or the longer the total lengths of the particular lay? Though the stored energy seems to make sense. I'm not sure the LDH burst would be very dramatic as its so heavy it doesn't move.

OBTW: While it doesn't make a difference in the standard (except psi) my real issue is with testing LDH. Let me elaborate on how we test:

We lay out (4) 300 ft. lays of LDH, connect them to the truck fill them, bleed the air through nozzles or gated wyes and then bring it up to pressure. The issue is that this only gets 1200 ft. at once so we have to run a second test to finish the beds. While its only another 5 minutes in a perfect world, we usually have to stop to replace a gasket here and there and re-tighten nozzles, etc. So each engine ends up taking an hour and a half, and about three by the time its fully loaded and back in service.

Also a recap of what we know:

1. Pressure in a closed system is equal from one end to the other.
2. Contrary to popular belief you cannot test hoses at different pressures at
the same time, gating does not change pressure ina closed system.
3. We have the room to lay all of our bed in a single line if we desired. Though
this would be a pain if you lost a length. But it would be easier to reload.

Anyway thanks for the replies. I'm tempted to just test it as Harve described and be done.

[BC79er_OLDDELETE]

2. Contrary to popular belief you cannot test hoses at different pressures at
the same time, gating does not change pressure ina closed system.

Not without shutting gates before you bring it up to the higher pressure you can't. But if you fill one hose, close the gate (system), then raise the pressure for the next line, close the gate, and continue on to the highest pressure then you can test as many simultaneous pressures as you have gates for.

[Iceman136]

I believe what you have a memory of is the maxium length of re-testing repaired hose, repaired or replaced couplings should be limited to a max of 300' test lengths before they are returned to service.

When you think about it the static pressure of water in hose (no matter what the length) is constant. So if you pressurize (after you bleed the lines) to 300 psi the entire length is at 300 psi. The way I was taught to do hose testing is you lay out the hose to be tested, connect into the pumper (Pumper has a water source), charge all the lines, bleed all lines, increase to testing pressure for that recommended time. Hint: we also have a booster reel just opened into a storm drain to have moving water so the pump doesn't overheat....and we gate down our discharges..so if a line does blow it doesn't whip around and kill anyone, you only have to makeup the leaks in the couplings so you dont need the discharges at full open for full flow. Hope that helps you.

[neiowa]

Or perhaps, in the name of safety and responsible practice, use the correct piece of equipment for the job - a hose tester?

[jtstoney]

testing

You lost me here. Do you me the longer the hose lays on the ground with pressure in it or the longer the total lengths of the particular lay? Though the stored energy seems to make sense. I'm not sure the LDH burst would be very dramatic as its so heavy it doesn't move.


Also a recap of what we know:

1. Pressure in a closed system is equal from one end to the other.

RFDACM02,

Sorry to confuse you. I was refering to the total length of the hose sections, and not the time on the ground.

To clarify, LDH bursts are very much dramatic, there have been several fatalities from failures, and numerous broken bones.

The biggest problem with hose period is coupling retention. I witnessed one test on 5" where the storz coupling flew off, and to this day we have never found it. Sounds odd, I know, but it happened in front of a crew that was witnessing it.

As designed, LDH usually has a longitudinal burst, meaning it splits lengthwise, like a bananna, with little to no violent reaction side to side.

As for your recap #1, pressure in a closed system is equal only if it is on a level surface. Any change in elevation adds .5 lbs psi head per foot, regardless of diameter.

One other thing to consider, water is not compressable, but the hose is elastic, sometimes as much as 10%. This elasticity stores energy that is released in a failure.

Think of this. 5" LDH has an elongation of 6% at 200 psi. That means that your 100' section, which normally holds one gallon per foot, now holds 106 gallons in its 106' charged length.

If a coupling fails, you have 6% more water that vents immediately. At the same time, the hose instantly shrinks rearward 6' to its normal length. That movement can transfere to a side to side momentum and strike someone or something.

Lots to think of, but there are reasons for 300' maximum lays, or shorter.

JT

[RFDACM02]

Not without shutting gates before you bring it up to the higher pressure you can't. But if you fill one hose, close the gate (system), then raise the pressure for the next line, close the gate, and continue on to the highest pressure then you can test as many simultaneous pressures as you have gates for.

Good point, but I know that on most given days the valves in our engines are not as tight as we'd like.

JT: Thanks you shed a lot of light on the subject. Now its starting to make a lot more sense. Oh well, as usual the easy way is not the right way. I guess we'll keeping doing it as we've done in the past, though I think closing the gates once the lines are up to presure is a new one for us. As long as we keep the pump turning and can keep it cool this may limit the potential for the more dramatic bursts in any size line.

[RFDACM02]

I believe what you have a memory of is the maxium length of re-testing repaired hose, repaired or replaced couplings should be limited to a max of 300' test lengths before they are returned to service.

I finally installed the latest NFPA disc and pulled up 1962. Here are a few sections that clarify things better.

So from NFPA 1962, 2006 Annual Revision Cycle:

With regard to repaired hose:

"When couplings are attached or reattached to hose, the hose shall be tested at its service test pressure one length at a time in accordance with Chapter 7" and "If the hose is repaired, or the couplings are repaired or replaced, the hose shall be service tested one length at a time in accordance with Chapter 7 before being placed back in service"

Regarding why they say 300ft. :

"Hose is tested in lengths not exceeding 300 ft (91 m) to allow the hose to untwist and be straightened out. As the pressure rises, the shorter length will allow the hose to assume a natural elongation, creating less warp in the hose."

I guess I could have looked here earlier, but this was a good review and some of the ideas are quite well thought out.