LDH and the FDC

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Permalink Reply by Robert Owens on April 13, 2008 at 11:06am

One of the problems we have seen in my locality is that the weight of the charged 5 inch being elevated of the ground for a long period of time will cause the coupling to be seperated from the hose. If you have a way to either support the weight or design the connection lower to the ground so that the weight is not a factor then I think it could work.

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Permalink Reply by Brian Arnold on April 13, 2008 at 3:00pm

Mark,
Check out some of the comments on the Start Water group. Mike Walker posted some good comments on this very thing several weeks back and talks specifically about the problems associated with 5" to the FDC.

Brian

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Permalink Reply by Mark Lee on April 13, 2008 at 9:42pm

Thanks Brian. I will see what I can find.

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Permalink Reply by Mark Lee on April 13, 2008 at 9:43pm

Wow, I forgot all about the weight issue. I think I need to pull out the old books, dust em off, and brush up on the whole Hydraulics class again...

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Permalink Reply by Mark Lee on April 13, 2008 at 9:50pm

So Brian,
I read what Mike, and the others, had written and now suddenly I don't feel like I am smoking crack afterall. This just did not make sense to pump the higher pressures on hose that we sandbag and stand way back when we test it annually to 200 psi.
Has anyone else experienced failures with this type of FDC?

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Permalink Reply by Chris Fleming on May 9, 2008 at 10:32am

We have been seeing the same thing here in Portland, Maine only with four inch Stortz connections. I had the same question for our fire Prevention guy and he kinda just gave me that look... Good comment on the weight issue, I too forgot all about that. The other issue about the single 4" connection is that you lose all water if the line bursts, whereas the double 2 1/2" or 3" connection gave you a back up if one line went down. This is definitely an issue if we are pumping the LDH at the limits of it's ability. It seems to me that this idea of the single LDH FDC is another "quick fix" to reduced staffing on engines, lack of practical knowledge by building designers and code enforcement folks and complacent fire prevention efforts.

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Permalink Reply by Thomas Horne on May 9, 2008 at 2:19pm

That is a concern I have shared with our Safety office as yet without any response. The test pressure for the LDH hose that we carry is 185 PSI. We are supposed to maintain a fifty PSI safety margin during operations. Our LDH discharge manifolds have pressure relief valves set at 135 PSI. In order to supply some of our old law unsprinklered high rises we need 150 PSI for the standpipe pack consisting of 150 feet of 1&3/4 inch hose with an automatic nozzle to obtain a flow of 150 Gallons per minute. To offset that disparity my company changed to a 50 PSI low pressure nozzle set in the standpipe pack which is designed to flow 150 GPM. That brings us to 100 PSI for the standpipe pack itself, 25 PSI for the standpipe internal losses, and five pounds per floor. All of these figures were confirmed by one of our Assistant Chief's who is a fire protection engineer. He supervised testing that was done at a high rise that was to be demolished. That means that at anything over the third floor we are invading the safety margin of the Large Diameter Hose. We have buildings of this type that are fifteen and sixteen stories high. Up to the thirteenth floor we are within the test pressure but with no safety margin on the annual service test of the hose. Add that to the fact that the county did not change all of the standpipe pack nozzles to low pressure and you have a disaster waiting to happen. What I asked for was an SOP that required attack rated hose be the only hose used between the last pumper and the standpipe inlet. Nothing heard back from the safety office in three years after three memos so I gave up. Meanwhile since the manifold's relief valve was opening at "too low a pressure to supply standpipes" plain wyes were purchased to permit the hose to be pumped at pressures that are over the safety margin and even over the annual test pressure.

One special note that came out of that testing is that it is unwise to connect LDH hose to a 2&1/2 inch standpipe inlet directly using an adapter. The friction loss in the standpipe doubled when we tried that as compared to supplying the inlet through two short lengths of three inch hose with 2&1/2 inch couplings via a manifold from the end of the LDH. That was only one particular standpipe that we tried that on but it raises the possibility that others may behave in a similar fashion if supplied in that way.
--
Tom Horne

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Permalink Reply by Mark Lee on May 9, 2008 at 2:40pm

I agree. I feel that we are always looking for ways to make things easier / quicker. Sometimes we forget to take a closer look at what we are doing.
I have not made any change as of yet to our practice of requiring the 5" storz coupling; yet, I think that we are getting close to that point.
Thanks for all of you guys input so far and keep it coming.
Anyone have any information that would make the 5" storz make sense?

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Permalink Reply by Mark Lee on May 9, 2008 at 2:41pm

Thanks Tom. This is some valuable information. Never give up, get a response from your Safety people. One way or the other, we need to always press for a definitive answer when it comes to potential safety issues. Although I haven't made a decision yet, myself...

What are those words again? Practice what we...

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Permalink Reply by G. Douglas Webb on May 9, 2008 at 3:39pm

Weight is only a small problem that can be handled by adding an elbow to the connection so your hose angles up from the ground. The real concern is the one mentioned below by Chris Fleming. If you lose the LDH supply you lose all water. That doesn't happen with dual lays. An alternative is to lay in to the system from a hydrant ( to a safe distance from the structure ) and then supply with dual lines of say 100 ft. There is also a Large Diameter to two 2 1/2 in. gated wye on the market that you can connect to the LDH FDC and then supply with duals. I know its designed to work in reverse but you can use it in this application. Of course that means reverse couplings may also have to be used but we're firefighters so we do know how to improvise.

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Permalink Reply by Mark Lee on May 9, 2008 at 3:59pm

Absolutely. This is the direction that I am leaning with the 5" manifold and laying twin 3's. Most of our FDC's with the 5" already have the elbow so I guess this should help with the weight as you mentioned.
I am truly concerned with the higher pressure on the 5" for a long term event (much longer than the annual hose test) and like mentioned by all, if you lose that line, you have lost it all!

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Permalink Reply by Chris Fleming on May 9, 2008 at 4:11pm

Mark,
One last thought for you. FDNY used to run (don't know if they still do) high rise units. They may be a resource for you to get your questions and concerns addressed about FDC supply, pressures, fittings etc.

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