LDH to supply FDC

Replies to This Discussion

Permalink Reply by Mike Walker on June 7, 2008 at 7:28am

Russ

Our Code guys started allowing building owners to place Storz couplings on their FDC's a few years back. At first I was concerned by this because of the type LDH hose we carry. I contacted a couple of different hose vendors and inquired about double jacketed LDH. Both of them informed me that the type of hose didnt' matter as long as Storz couplings were used. They are the weak link. 200 psi test pressure and 185 operating pressure.

If you think about it; it makes sense. Extruded aluminum couplings that get dropped 100's of times over their service life. I know in the Tech. Rescue world, if I drop an aluminum caribeener they recommend taking it out of service yet supply hose gets dumped several feet nearly every time it is used.

A couple of times students have informed me that they contacted a hose vendor and the salesman told them grand stories of the testing LDH goes through. They'll speak of enormous burst pressure strength tests and how their hose can do everything but cook your morning breakfast. Everytime that has occured I have asked the student to call the vendor back and ask them to put it on the hose manufacturer's letter head that we can exceed the recommended flow pressures. I'm still waiting to see any responses back. Why? Because the hose manufactures know that their hose may be able to withstand extreme pressures when they are new but over time they can't. Once the hose his dropped 100 times and frozen, baked, ran over, etc. it weakens the hose/couplings.

Another point I consider. When do we remove hose from service? When it fails!

During any operation at an FDC, hose failure could be fatal. And to add to that, LDH is as likely or more likely to fail at the coupling making a very nice club.

Permalink Reply by Russ Chapman on June 7, 2008 at 6:04pm

Boy.....I just did a whole huge reply and the system ate it!!!!!
Anyway, Mike I think you and I are singing the same song.
I don't want to put all my eggs in one basket...
You can't pump more than 170 PSI to supply LDH due to the NFPA standard of 30 PSI increase in pressure before a relief valve or governor needs to engage.
I have been on FDC operations where 150 PSI was not enough.
I seen what happens to LDH when it lets go, and the couplings had nothing to do with it, ( I have the section with an 18" enlongated gash in my locker)
We forget how much water a 3" line can push!
Be safe

Permalink Reply by Mike Walker on June 7, 2008 at 6:35pm

There haven't been that many recorded failures of 4" LDH but according to coupling manufacters they see it more in 5" line with the Storz coupling.

We are allowing LDH on FDC's when pressures above 150 are not going to be needed. I've been seeing another issue which I think I'll use for a new discussion. The phenomonon of system failure when pressures of 150 psi are achieved. Even though Standpipe systems are supposed to allow for increased pressures, sprinkler systems are not. How does that effect combination systems? I have seen one fail recently at 150 psi. We were still able to get a good stream but at the opposite side of the structure water filled the place. It would have been a matter of saving a building only to lose it to water damage.

Permalink Reply by Russ Chapman on June 8, 2008 at 5:11pm

There's got to be a way to isolate the standpipe from the sprinkler, or you would not be able to pump the riser directly off a lower standpipe outlet after you close the contol valves? I dunno. All I know is that the standpipe has priorety, and if something else lets go, we did not take the short and cheapest route and built it that way! Oh well!

Permalink Reply by Mike Walker on June 8, 2008 at 5:35pm

Good point.

I also forgot to mention another instance that occured several years back. When we pumped into the system and flooded the entire basement. So it's happened twice just to me.

Permalink Reply by Russ Chapman on June 9, 2008 at 7:32pm

Same here. Blew right behind the FDC. Stamford CT had a riser let go about 10 months ago. Scary Stuff!