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I know this should be in the "training" section, but I figured most of the engineers and operators were down here. I am a driver trainer in a rural department looking to hold a mutual aid relay pumping drill. We generally run tanker shuttles in our area so we don't have much experience with them. I would appreciate any advice you guys may have for me. Also, any links to drill outlines that you'd be willing to share would be greatly appreciated. Thanks in advance!!
I will see if I can scratch up a copy of the SOP's for the Montgomery County (Pa.) LDH Task Force- who's basic job and standard is to deliver minimum of 1000GPM up to and including one mile from the source.Quote:
Originally Posted by 3260e
The most basic rule is: Get the water moving, keep it moving! Meaning, if for some reason an engine in the relay has to shut down, you don't shut down the whole relay. Getting a relay up and running it time consuming enough.
The engine behind the one that had to shut down diverts its water out onto the ground if need be.
To expand on Buff's message, some of the basics in the MontCo. LDH Task Force include, each engine must be at least 1,500 GPM. Not more than 1,000' between engines. A relay valve is used at each engine so that in the event of a failure of the engine, the water can be diverted around it until a replacement engine is brought in. That way, the integrity of the relay is maintained. Remember, get it moving, keep it moving! Another point, engines that are equipped with pressure governors, the governor is operated in the throttle control mode rather than the pressure control mode.
Those are just a few of the basics but it gives you an idea of things to think about. It's not rocket science, it's just the application of some high school physics.
I'm working on one using Turbo Drafts, I'll send a copy when I get it done.
3260: Pump Operators never get enough time moving water. In the course of any fire there are usually several things that jump up to bite you, and you are forced to recognize the cause from the effect. The rapid recognition of the cause and a subsequent action to correct the condition are usually the result of years of operating and exposure to actual fireground conditions.
Operating in a long relay for most rural pump operators is an unusual occurance. One area that is seldom practiced is laying out LDH while other operators observe the hose leaving the bed at different speeds. I know it is a pain for the probies and grunts, but trying different loading techniques and different speeds is a good learning exercise for everyone. We typically use first gear on the Mack and run at 1500 to 1800 rpm during the lay. By limiting the speed, we dont get the adrenalin doing strange things like causing a high speed lay problem. This exercise is OK for the probies and drivers, but becomes a pain for the grunts. Once you all know what methods to use in loading and the speeds are determined for laying out, then an SOP on loading hose and laying LDH should serve you well for many years.
Actually establishing and operating a relay is another matter. I like to divide this into two different aspects. Pumping long lays forces the operator into using the radio, as hand signals are rarely usable considering distances, turns and apparatus placement. The biggest effects of an actual long lay-out are fill rates and reaction times for pressure changes. When a change is made on the fireground like shutting down a line, it takes some time for the change to work its way back to the supply engine.
One way to practice operating multiple engine relays is to replace the LDH with 3 hose. Since the K factor for 3 with 2 ½ couplings is 1, and the K for 5 is 1/15th then a 100 ft section of 3 has the same losses as 1500 ft. of 5 LDH. We use 25 ft. sections (2) in hooking to Mae West hydrants, so we can set up 1500, 1100, 750 & 400 ft equivalent relay distances. (Extend short pieces with 5 LDH if necessary) Start this exercise by placing an engine at the source with the pump operators panel facing away from the water source. Park each succeeding engine with the operators panel facing inward and run all the 3 around the outside. (Circle the Wagons) This allows each pump operator to observe the effect his actions have caused for every other operator in the relay. It is important to remember that, with modern pressure governors, only the attack engine should be operated in the pressure control mode with the governor. This should be a minimal problem when using the short sections of 3, but long lays of 5 have a significant volume change as pressures change in the system. Sometimes (not always) it is possible to set up a delayed reaction between engines caused by running multiple engines in the pressure control mode.
Let us say that after the relay has been established, a large line shuts down on the fireground. The resulting increase in discharge pressure causes the attack engine to throttle back. At the same time the reduced flow in the relay causes the intake on the attack engine to rise, further causing the pressure governor to again throttle down to keep discharge pressures at the original set point. Because of the delay, the relay engine does not see the spike in pressure immediately. About the same time as the attack engine is cutting back, the relay engine also starts to throttle back, but the expansion in the LDH keeps the change from being transmitted rapidly as the hose is now shrinking slowly causing another delay in the reaction. Eventually what happens is a surging action is established causing pulses in the system. To avoid this, place all engines except the attack engine in the rpm mode, and chain the pump operators to the panels.
Careful selection of the discharge on the draft and relay engines is necessary to avoid large internal pump losses. Since LDH supply hose is rated and tested at 200 psi, we need to set a max operating pressure on the relay of 185 psi. Assuming 20 psi intake pressure minimum, then the friction loss needs to be limited to 165 psi including internal pump discharge losses. Using the friction loss equation, we can find that 100 of 3 (1500 ft. of 5) will supply 1280 gpm, 75 of 3 (1100 ft. of 5) will supply 1480 gpm, 50 of 3 (750 of 5) will supply 1816 gpm, and 25 of 3 (400 of 5) will handle about 2500 gpm at 185 psi discharge on each relay engine. By running parallel and series hose lines, almost any layout can be simulated using short lays of 3 between engines. This makes it easy to set-up relay practices without the time constraints of repacking large quantities of LDH. It also keeps the equipment readily available should an alarm require the response af any engine assigned to the drill.
Have fun playing!
Great stuff! Thanks to all for the help, I will report back after we try a drill and let you all know how it went! If anyone has any more tips, keep'em coming.
We run LDH, either 4" or 5" depending on the company. Here's how our relays get setup:
1) Supply engine set's up at water source. Either hydrant or draft.
2) Second engine will dump it's hosebed, laying out from the first. Most like to leave 100' in the bed incase there is a burst length or whatever, it can easily be replaced.
3) When the second engine dumps it's bed, the operator connects to his intake and calls for water from the first.
4) The third engine will repeat the process, again calling for water once he's dumped his bed.
5) When the lay eventually reaches the fire, the only 2 trucks talking to each other are the source truck and the attack truck. If the attack engine calls for more pressure, it's always in 25psi increments. Each truck in the middle simply adjusts his intake gauge to 20psi residual. That's it. simple and to the point.
By doing it this way and filling the line as you go, you're ready for water at the fire scene as soon as the lay is complete. There's no waiting for X amount of LDH to get filled.