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  1. #1
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    Default Intake Relief Valve Setting

    I searched the archives and really didn't find an answer to the following question:

    What should the set point be for an intake relief valve such as the TFT Intake relief ?

    I always thought that the relief set point should be some percentage over the maximum hydrant pressure. Say 10% over the maximum hydrant static pressure. Others have chimed in that they should be set at 150-200 psi to allow for relay pumping...I'm missing that point since the residual pressure at your engine during a relay should be on the order of 50 psig.

    Thanks,
    LDR20TRK


  2. #2
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    I like setting the intake relief valve at or something above the maximum hydrant pressure, but not much. In our area we have some monster hydrants, carrying normally 180 - 185 psi. Both of our engines are equipped with piston intake/relief valves, also. I have the pumps' intake reliefs set at 185, and the piston valves set at 190. Works well for us. When we first flow water into the pump case, the main intake valve may open briefly. If the pressure is particularly strong, the relief on the piston intake valve may open also. In almost every case, as soon as pressures stablilize, the reliefs close.

    The only logic I can see for keeping the relief set high for relay pumping is that if lines flowing water to the fire are shut down, your intake pressure is going to go up considerably, well above that desirable 50 psi. Whether or not you want to allow for that is an operational matter that your department should review and set SOPs around. Just be certain that your SOP takes into consideration preventing a pump damaging water hammer.

    Sure would like to see some more opinions on this subject, there's a lot to be learned from it.

    Stay safe out there, everyone goes home.

  3. #3
    Forum Member Chauffeur6's Avatar
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    We also set ours just above the average maximum pressure of our strongest hydrants, which falls somewhere around 150 PSI, so the valves are generally set at around 160 to 170 PSI. Anything lower and you'll be ****ing water all the time, anything higher and there's hardly any point of even having an intake relief valve. Also, I can't see pumping anything over 100 PSI through LDH. For relay pumping, you're much more concerned with volume than you are pressure (or at least, you should be). I once had a guy send me enough pressure to blow my relief valve through a fairly short lay of 5" (300' between him and the hydrant, 500' between me and him) and I wanted to go over and hit him in the head with a Halligan for being such a moron.

    Incidentally, if you're using an external piston relief intake valve...such at the TFT, Snap-Tite, Harrington, etc...just remember that the pump itself almost always has an intake relief valve built in to it. You have to adjust this also, as adjusting just one or the other will be pointless. I believe most pump relief valves are factory set at 150 PSI unless you request otherwise. It's very important not to set it too high, as it will negatively impact the discharge relief valve/governor system, which can not only damage the pump itself, but can get guys on handlines hurt.
    Last edited by Chauffer6; 09-09-2006 at 10:10 PM.

  4. #4
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    LDR20TRK

    We set ours at 180, because our LDH is rated at 200 PSI.
    10% safety factor,reason being we have to pump our Truck
    Co.'s and you have to pump more than 100 psi to get a 1000 gpm at the tip.You need to Know what your LDH is rated at, then go from there.
    As for hydrant pressures we are lucky to see 90 psi hydrants.

    The pump intake relief doesn't need to be set at the same as the intake relief. Ours are set at 260 psi because we have high rises that need to be pumped from 250 to 600 psi, of coarse this requires us to tandem pump.As for the discharge relief valve/governor if there set your guy's will not feel a thing with pressure spikes, nor will it affect your intake pressure. Hope this helps.

  5. #5
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    Quote Originally Posted by Chauffer6
    Also, I can't see pumping anything over 100 PSI through LDH. For relay pumping, you're much more concerned with volume than you are pressure (or at least, you should be). I once had a guy send me enough pressure to blow my relief valve through a fairly short lay of 5" (300' between him and the hydrant, 500' between me and him) and I wanted to go over and hit him in the head with a Halligan for being such a moron.
    If you want to move alot of water, you'll have to go over 100 PSI.

    To move 1500 GPM about 900 ft you'll need to pump at 185 PSI in 5" hose (this leaves 20 PSI residual).

    In most cases, supply lines are laid to establish a continuous flow, rather than a maximim or high volume flow. Generally for 2-3 handlines (typical all hands type fire). Since this is the case, we tend to get away with long hose lays or low pump pressures, because the water supply demand doesn't require higher pressure (flow) or shorter lays (more relay engines with shorter distances between them). What this tends to cause is a sense of complacency and laziness. When the big one hits, I'll bet you dinner at a nice restaurant that many co's will be trying to supply 2 master streams and 3 handlines with a single 4 or 5" line from a hydrant with 800' of hose on the street and they'll be screaming that the hydrant sucks.....

    I say always start pumping the supply line at 100 PSI and adjust up/down once youve calculated the flow and/or the receiving engine tells you to adjust. Its funny how many operators scream how they need the pressure dropped from the relay engine when all they need to do is drop the throttle on their pump and take advantage of the incoming pressure.

    We set our intake valves for 150-160ish.

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