Thread: LDH Hydrant Valve
10-29-2000, 11:21 PM #1DashFirehouse.com Guest
LDH Hydrant Valve
Currently, I am upgrading our department with appliances for industrial and municipal application. In rookie school the LDH Hydrant valve was not taught. I am looking at this appliance in our application, I need some help in better understanding this appliance. What department use this valve and case history of this would be helpful.
10-30-2000, 11:45 PM #2wannabe-EMTFirehouse.com Guest
From my very rudimentary understanding of my department's four-way hydrant valve (from a simple EMS standpoint), we use it to increase pressure in LDH. The attack engine leads off from the hydrant, connecting, and flows water through the five inch. The supply engine hooks up, running two sections of five inch, from the valve to the pump intake, then from the discharge to the valve, to increase the pressure inside it. As a result, water can go farther and have a higher discharge pressure.
Our department covers an everything territory, with: Residential streets, narrow side streets, a major four lane roadway, I-95, industrial complexes, woods and offroad areas, train tracks and shopping centers in our box area, with a mall and a beltway in the neighboring box area.
We always hook up with the 4-way, but I don't know the reasoning behind it. Sorry if this doesn't help. Maybe a pump operator could provide some more insight? Anyone wanna pitch in?
Peace, and stay safe.
10-31-2000, 02:37 AM #337 Fire/RescueFirehouse.com Guest
wannabe described the use of the hydrant valve (We call it the Hydra-assist) pretty well. One main advantage is you can hook up while the hydrant is is use and you don't have to break down to boost hydrant pressure. Very helpful if you use primarily a forward lay, which we do. First engine in lays from the hydrant to the fire. Second engine in picks up the hydrant, hooks into the hydra-assist valve and engages it if necessary. If the residual pressure is adequate, then you do not have to boost pressure with the truck. Hope this helps.
11-05-2000, 09:28 PM #4Lieut706Firehouse.com Guest
The 4 way or hydra-assist is a great tool that allows you to flow at hydrant pressures, then when an engine is available, boost pressures without interupting flows. What this does for you is to get immediate water, then boost flows (GPM) by getting greater pressures. The hydrant will (hopefully)supply more water than you can push through the 5 inch at hydrant pressure. By pushing up the pressure with the assist of the supply engine you increase flows to the fire. Its all about being able to use the available gpm from the hydrant. I ran in Baltimore county Co 310, Owings Mills, for a few years in the early 80's, and I LOVE the water supply we had. 36" mains up reistertown road. Hardly had to use the pump. I miss it now, as we have no hydrants in Lebanon.
[This message has been edited by Lieut706 (edited November 05, 2000).]
11-05-2000, 10:22 PM #5LHS*Firehouse.com Guest
One disadvantage is they reduce the flow to the pumper before the boost occurs by as much as 50%
The cost for the valve when factored into the cost of the hose would allow the next size hose, which in a majority of cases will flow more than using a pumper in relay through the valve.
The cost of the valve would also allow laying two lines if it was hose, which again would boost flows and pressure more than a pumper in realy.
11-06-2000, 10:55 PM #6ffengFirehouse.com Guest
Where you might want to start is with some hydraulic analysis of your water supplies (hydrant flow and pressure)and then look at how you are supplying your pumpers. Simply put, water moving through hose uses energy and pumps add energy. In water flow, the energy is pressure. The larger the diameter of the hose, the less friction loss (energy loss), therefore more energy (pressure) when the water reaches the pumper. It is likely most efficient to ensure that your supply hose arrangement uses up the least amount of energy (pressure) from the hydrant. The goal should be to minimize energy (pressure) loss to the pump, this way, you essentially move the hydrant right next to the attack pumper every time so that the attack pumper can use every bit of flow and pressure that the hydrant can supply. This method also only uses one pumper to max out the flow of a hydrant.
If you see that your current arrangement of hose size, distance, and flow requirements use up a lot of energy(pressure) just getting the water to the attack pumper, you have two basic options - one lower the energy losses by going to larger hose or multiple lines (this can be significant - on longer lays/higher flows - you would likely get more pressure to your attack pumper by going from 4" to 5" hose than relay pumping with the 4") or adding a second pumper to add energy (pressure) so that you can overcome the friction loss (energy loss) in your supply lines. This is where the four way hydrant valve is useful.
Can you give us some specifics:
What size supply line - single or double lay
What is your max lay you want to figure
Do you have some hydrant flow data on a hydrant or two? This would be a static pressure and at least one residual pressure and a flow (example 90 psi static; 800 gpm @ 65 psi).
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