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  • #16
    At a single-family dwelling house fire, why would we ever need to relay pump?
    Ever have 2 trucks hit 2 hydrants at once? If they are on the same line/grid, the pressure in those hydrants will vanish once the second hydrant is opened. You still have a 1000gpm hydrant, but it now has 10psi and that won't get you the water. We run into this often. If you never have a second hydrant hit, then you may not have to worry about it.
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

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    • #17
      The higher the pressure the water is when it comes into the attack pumper, the less the attack pumper has to work.

      Which isn't necessarily here nor there.

      If you have 150psi coming in, you're gonna be almost throttled down and/or having to gate back discharges to keep their pressures reasonable to the flow.

      Our fire pumps would be happy campers to have 150psi intake and add another 150psi and have 300psi discharges. Guys on the knob are probably not going to be happy campers!

      Throw in someone monkeying at a relay pumper, the fireground guy is constantly pulling and pushing levers to try and keep his discharge pressures even and reasonable.

      A relay pumper cannot add volume to the water flow, only pressure
      With the clarification that by adding pressure to overcome friction loss (which is higher at higher flows), a relay pumper allows that volume to be delivered further.
      IACOJ Canine Officer
      20/50

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      • #18
        Well.........

        Here in downtown Maryland, I don't have any 5" hose, nor do I want any. We have reasonably close hydrant spacing (300 Ft in some areas, 600 in most) good mains with good pressure, AND, you will always find an engine on the hydrant. Period. We demand the control and flexibility that a source pump gives us, and our operations are better for it. On a single family dwelling, we never (that's right, I said NEVER) get fewer than 3 engines on the initial dispatch, quite often, more will show up. First engine lays 1 or 2 3" lines from the hydrant, 2nd engine hooks into hydrant, 3rd engine stands by at the next available hydrant, to bring in a backup supply if needed. If additional engines are running, the 4th will pick up the backup hydrant, and the others will stage out of the way. Multifamily residential and commercial alarms get at least 4 engines, and the operation is the same, if there is a building system, the first engine hooks into it. Why no LDH? Once a LDH line is charged, there is no getting over it, this effectively blocks out later arriving apparatus (among other things). We do have several units with 5" LDH, they are special called as needed, thankfully not often. Stay Safe....
        Never use Force! Get a Bigger Hammer.
        In memory of
        Chief Earle W. Woods, 1912 - 1997
        Asst. Chief John R. Woods Sr. 1937 - 2006

        IACOJ Budget Analyst

        I Refuse to be a Spectator. If I come to the Game, I'm Playing.

        www.gdvfd18.com

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        • #19
          HWOODS, So what you are saying is that most of your fires are controlled by either 1 or 2 3 inch lines. Must be nice to have those types of fires. I understand the moveability of the LDH, But here we do not have that luxury of having 3 engines because of smaller Volley company and we do not have the luxury of close proximity to hydrants everywhere, nor do we have the luxury of all the toys you all have down there. So Relay pumping does come into play for us on calls outside the village and in mutual aid areas.

          Like others, we either have the pump at the water source or in line where needed for boosting the pressure, not the volume just the pressure. All engines lay in forward on 99% of the calls, but we still train on the reverse lays for the occasional call when we need to utilize that also.

          Chief, you all got your act down there in that neck of the woods though I will admitt that. Stopped by one of the stations a couple years ago, and you all have a real nice set up and some down right intelligent people that knew everything about your operations.


          STILL STANDING!!!!!!!!!!!!!!!!!

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          • #20
            In Baltimore County, Maryland we have a term called "Heavy Water Hookup" for our hydranted areas that is very rarely used now that most companies run 4 and 5 inch LDH. The real oldtimers tell me it was used a lot back in the days of single and dual 3" supply lines. Us old guys still train "the kids" on it.

            We use Humat hydrant valves and typically if the first engine drops a line this line is connected to the hydrant at the steamer outlet and a water supply is established. For those of you not familiar with a Humat, it has one steamer connection with a clapper and then has two outlets that are controlled by a pressure sensitive clapper valve and one that is controlled by a manual vavle. One of the side connections is attached to the supply line and the other is open. The second engine hits the plug and can hook up to the hydrant to boost the pressure if necessary. The second engine connects to the Humat with a suction hose and then connects a discharge line to the open side connection. The manual valve is opened to allow water to enter the relay engine's pump where it is discharged back into the hydrant valve. The pressure actuated flapper opens and the pressure boosted water is sent on it's way to the attack engine.

            The beauty of the Humat is that the supply to the initial attack engine is uninterrupted while the heavy water hookup is taking place.

            In non hydrant areas, we typically have an engine at the fire scene which lays a line from the end of the driveway or access into the scene. A second engine and a drop tank are set up at that point to supply the attack engine and a shuttle is run to keep the porta-tank full.

            Harve, you are right. LDH can be a real pain in the butt if it's not layed right. We've invested in some hose ramps for cross streets and we train our PO's to try to keep the line along the road shoulder or curb as they lay out. If we have sufficient bodies, we will move the line to the side before we charge it. Not always possible though. If you have a worker, tank water doesn't last long
            Chris Minick, P.E., Firefighter II
            Structures Specialist, MD-TF 1

            These statements are mine and mine alone
            I.A.C.O.J. Building crust and proud of it

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            • #21
              We are are all totally hydranted and we run soon to be all 5" LDH.He have a couple of places that are 1500'from the nearest hydrant and these are in industrial areas that have only yard hydrants with 2.5" connections. So our rule of thumb is forward lay first engine and next due attaches to the first one and completes the lay to the scene.
              Also, as previous posters noted it is the same gpm only under more pressure.
              IACOJ both divisions and PROUD OF IT !
              Pardon me sir.. .....but I believe we are all over here !
              ATTENTION ALL SHOPPERS: Will the dead horse please report to the forums.(thanks Motown)
              RAY WAS HERE 08/28/05
              LETHA' FOREVA' ! 010607
              I'm sorry, I haven't been paying much attention for the last 3 hours.....what were we discussing?
              "but I guarentee you I will FF your arse off" from>
              http://www.firehouse.com/forums/show...60#post1137060post 115

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              • #22
                4"

                SOP here is every 800' have a pumper,rarely used though cause of hydrent spaceing being 500'.
                I dont suffer from insanity, I enjoy every minute of it.

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                • #23
                  no ldh discharge

                  Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.

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                  • #24
                    Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.
                    Hmmm. I dont think it would be very efficent with 2.5". Your maximum effiecnt flow would be 500 gpm with 2 lines, thats half the capcity of a single 4"line and 1/4 the capcity of a 5" line. I see alot of problems with pressure and volume--course I could be wrong.
                    I dont suffer from insanity, I enjoy every minute of it.

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                    • #25
                      Re: no ldh discharge

                      Originally posted by gregblewett
                      Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.
                      The reason one uses LDH is to eliminate the friction loss created by attempting to shove a large volume of water over a long distance thru a straw. Can't do it with tiny hose dia, use LDH to reduce the friction loss. Outlet dia on your truck is not the critical issue, use an adapter on the pumper outlet if required.

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                      • #26
                        Re: no ldh discharge

                        Originally posted by gregblewett
                        Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.
                        The other thing you can do is get a Siamese or Trimese and run short sections of 3" off your discharges into the LDH that way...... Stay Safe....
                        Never use Force! Get a Bigger Hammer.
                        In memory of
                        Chief Earle W. Woods, 1912 - 1997
                        Asst. Chief John R. Woods Sr. 1937 - 2006

                        IACOJ Budget Analyst

                        I Refuse to be a Spectator. If I come to the Game, I'm Playing.

                        www.gdvfd18.com

                        Comment


                        • #27
                          What is the flow through a 2 1/2" nozzle at 100 psi? 1856 gpm. So should you be able to flow 1000, 1250, maybe even more through a single 2 1/2" discharge? Of course the internal piping from the pump to the discharge play a part in this capability. I will tell you this with our 1974 Mack CF we relayed through 1400' of 5" hose through one side discharge and flowed roughly 1000 gpm easily to the attack pumper. The only way to be sure it can be done is to try it some night in training.

                          FyredUp
                          Crazy, but that's how it goes
                          Millions of people living as foes
                          Maybe it's not too late
                          To learn how to love, and forget how to hate

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                          • #28
                            Re: no ldh discharge

                            Originally posted by gregblewett
                            Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH?
                            Let me echo FyredUp... No problem, you're talking about 2.5" pipe, not hose, much lower friction loss, and the pipe is fairly short. All of our "older" trucks have a single discharge that is equiped with a 2.5" to 5" adaptor and we can flow to the capacity of the pump (1250-1500) through that discharge.

                            There is even a discharge adaptor I've seen advertised in Firehouse and other places that screws onto a 2.5" port and gives you both 5" stortz and a 2.5" thread on the same disharge allowing you to use either type of hose w/o having to remove the stortz adaptor.

                            Bones makes a great point. Think about it, if you're tapping the second plug you need a lot of volume, that would be a bad time for the 1st pumper to see his LDH go flat because the residual suddenly dropped from 50psi to 20psi. 500' of 5" running at 1000gpm you need to overcome 31psi, so 50psi from the hyrdant. Have Engine 2 start pulling from the plug down the street and drop the residual to 30 you drop to about 500gpm. Which attack line are you going to shut down? Gulp!
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                            • #29
                              Woods,I love having you around man,it gets my post count up.You ever hear of hose bridges?Well they make really nice ones for LDH.Can't get small cars over 'em handy but apparatus is NO PROBLEM!Now in your situation you're probably ok with your 3"but there's just as much difference in going from 3 to 5" as there is going from a booster line (1")attack to a 1.75.Now on the pump end we spec our trucks with 3"pipe to the LDH outlet very little friction loss here.My hydrants are a tad bit farther apart than yours so I favor the bigger hose.But I'm just as glad I don't have to deal with some of your headaches either.Another reason to pump the hydrant is if your attack pumper experiences a problem (Heaven forbid)the source pumper can pump right thru.T.C.

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                              • #30
                                Alternative hydrant pump

                                Anyone using as SOP an engine driven pump at the hydrant rather than a very expensive fire pumper truck?

                                A nice 2000gpm diesel pump on trailer could be put together for under $25000 new vs a $150000 for an engine. Get creative could put together for much less. All that is functionally needed at the hydrant is input, pump/engine, output. Everything else on a pumper engine costs big $ and is not utilized.
                                Last edited by neiowa; 10-28-2003, 02:34 PM.

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