Thread: LDH Discharges

  1. #1
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    Dec 2007

    Default LDH Discharges

    The phase one report of the post incident review from the City of Charleston has been released and one of the suggestions listed was to have LDH intake valves and discharge outlets installed on each engine.

    This made me start thinking about my own station. We have three engines, they all have a LHD intake valve but only one has an actual LDH discharge.

    The only way I can see for a LHD discharge to be added to the other two engines is to use a 5" adapter on a 2 1/2" discharge. Is anyone currently doing this? If so what type of flow can be achieved?

  2. #2
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    May 2006


    I don't remember the exact flow, but when we did some flow testing on some our trucks with only 2.5" discharges the flow was in excess 1000 gpm using a ground gun and 5" hose... Main thing to look for in using the 2.5" discharge is the one with the shortest run of pipe from the pump to outlet this way you decrease your fiction loss.... Also a 2" smooth bore tip at 80 psi will flow little over 1000 gpm and your starting off with 2.5" outlet...

  3. #3
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    Mar 2007
    Eastern Ct.


    Putting a 2.5" X LDH adapter is common practice. Even our engines spec'ed with LDH discharge only have 3" pipe going to 5" adapter. The shortest run on the side opposite the pump operator is the best place to start with discharges. We put the LDH intake (5" storz, slow close hand wheel, with pressure relief) on the curb side and draft from the road side with 6" storz. This keeps the pressurized lines away from the pump operator. If your engine is newer it should have a intake pressure relief on the intake side of the pump, but we use it in the adapter so that a line can be protected even if the intake is closed.

  4. #4
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    mcaldwell's Avatar
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    Apr 2003
    Panorama, British Columbia, Canada


    Each of our engines have 4" LDH Piston relief valves on the steamer ports, but we only have an LDH discharge on our ladder. The engine gets an adapter off of the 2 1/2 discharge.

    Nonetheless, we can easily flow the max capacity of the 1050 IGPM (1250 USGPM) pump through that discharge to supply the ladder. A short and straight run of steel 2 1/2 pipe will not be a huge restriction.
    Never argue with an Idiot. They drag you down to their level, and then beat you with experience!


  5. #5
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    Jan 2007
    Pa Wilds

    Smile LDH discharges on engines.

    We have been using Watrous pumps since 1970. Originally this pump mfgr. did not have a good system for discharging high flows, but in the mid 1970's came out with "A Pair of Pants" connection. This piping adaptation connected two full flow 3 1/2" gated outlets to a single 4 1/2 NH connection out the right side. This allowed the connection of a 4 1/2" BY 5" Stortz adapter to feed the LDH. This was a great improvement over the 2 1/2" valves that were standard on the earlier models. We have been able to supply 2154 gpm (Factory test at Pierce) at 135 psi with less than 5 psi loss internal to the pump panel. This particular engine was designed to arrive 2nd or 3rd in our high value district and to supply two 1250 gpm attack engines on the scene. This has worked very well over the past 20 years.

    When specifying large flows the valve must now (NFPA) be a slow operator. From experience, be absolutely certain that the valve or valves can be locked in position. The high flow rates through small valve openings create large forces trying to slam the valves into the closed position. For anyone adapting a 2 1/2" outlet to LDH, please be sure that the valves are not 2" valves on a 2 1/2" body. This sort of piping and valves can easily cause 60 to 100 psi losses internal to the pump panel at flows over 1200 gpm.

    I strongly suggest that Performance Specifications be written into any new pumper specs. Under no circumstances should a pumper have more than 10 psi loss between the pump and discharge at the specified flow rates.

    The comment above concerning the nozzle pressure (80 psi) needed to discharge 1067 gpm through a 2" master stream nozzle can be applied to that same flow passing through a 2" valve. That is a 2" valve will need 80 psi across the valve to pass 1067 gpm. Additionally, 2 1/2" piping is basically designed to handle between 250 and 300 gpm flows. Each elbow will have between 3 & 5 psi loss at 250 gpm. The friction loss in pipe follows the same rules as for hose, so that increasing the flow through the elbow to 500 gpm will cause 4 times the loss or 12 to 20 psi. Doubling our flow again to 1000 gpm, you can expect 48 to 80 psi loss per elbow. If your fire company elects to try to stuff this much flow through a 2 1/2" outlet, expect some pretty high pressure drops internal to the pump panel. Try to select the outlet with the least number of elbows and the shortest path to the adapter.

    Along these same lines never try to get full flows through the pony suction intakes. I suggest you get a creeper and slide under your engines and count the elbows, valves and strainers that the water must pass through on its way to the pump intake. The most direct route, with the largest waterway is the path to select.

    Kuh Shise Just an old German B.S. er

  6. #6
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    FWDbuff's Avatar
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    Jul 2003


    At the time we began using (5") LDH, we were trying to come up with ways to move water more efficiently through it with our hydrant piece, a 1978 Hahn with a 1250.

    As stated above, we simply could have adapted one 2.5" discharge to storz. But the key operating word here is EFFICIENT.

    Obviously, the preferred scenerio was using multiple dishcharges to our advantage, but how to adapt multiple discharges to a single LDH?

    We studied an old 4.5 to (2) 3" gates siamese. Keeping in mind efficiency, we "gutted" it, removing the ball valve and associated assemblies, eliminating some friction losses. We were then going to special-order two lengths of 3.5" hose with female couplings on both ends- remember, this was an old siamese with male threads we wanted to adapt to......BUT......

    In the process of adapting our HUMATS to 5"LDH, we removed the 3" female plates and sat them on the workbench next to our modified siamese. I happened to be staring at them one afternoon, and lo and behold the bolt patterns matched up perfectly.....So off came the male-coupling flange plates from the siamese, and on went the female coupling flange plates.... we special ordered the 3.5" hose with male and female couplings, and our 5" LDH discharge was born!

    I cant remember specifics, but I do believe I moved 1000+ through it at a drill one night......
    "Loyalty Above all Else. Except Honor."

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