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Thread: LDH intake relief

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    Default LDH intake relief

    We are going to 5 inch hose and looking at appliances. Do we need intake relief valves mounted external to the pump.

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    Do you get supplied by other engines? or do you only work off hydrants? do you only work off port-a-ponds?
    "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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    Bones' answer is right on. If you ONLY draft, then there's no real need for one. But if you get water from any pressurized source, then you should have at least one. If you don't already have one already built in, (I'd be surprised if there isn't one on there somewhere), then look at one of the many piston or ball control valves that go right onto your steamer inlet. Most (not all) of them have adjustable relief valves built into them. Look at Akron, AWG, Harrington and TFT, just to name a few.

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    We normaly draft, but have a large factory with hydrants, we relay pump and mutual aid to hydrants. Our 95 engine has a relief valve on the pump but there is no adjustment at the panel. We also do tanker fills but will have manifold with relief before tanker.

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    What we do on my #1 POC FD is have a butterfly valve on the driver's side, and an intake relief valve on the officer's side and an inline pressure relief on the rear with no valve since that line is valved on the engine.

    We primarily draft from the officer's side of the rear. With the butterfly on the driver's side it is a direct connect to the pump intake. With just the inline pressure relief on the rear it is easy to remove it since it is smaller and lighter than an intake relief valve, so we also draft off the rear.

    If there is any circumstance that you will receive water under pressure through the 5 inch hose it is imperative to have that intake protected by an intake pressure relief valve.
    Last edited by FyredUp; 01-29-2012 at 01:03 AM.
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    If you receive water through LDH, you also need an air bleed on your intake.
    Bullseye Fire likes this.

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    If you have any industrial sites (warehouses, power plants, mfg) with a fire pump connected to the fire hydrant system you can sometimes see 175psi and sometimes 200 psi from the fire hydrant. If you do not know what pressures you will get, ask for copy of the annual fire pump test. Look for the "Churn" discharge pressure, it will be the highest pressure listed on the test form. OR the fire pump should be tested weekly, ask for the weekly test document, look for the "discharge" gauge reading. This will give you an idea of what you will get from the fire hydrant.
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    Quote Originally Posted by sklump View Post
    We normaly draft, but have a large factory with hydrants, we relay pump and mutual aid to hydrants. Our 95 engine has a relief valve on the pump but there is no adjustment at the panel. We also do tanker fills but will have manifold with relief before tanker.
    Both our pumps have relief valve built in....it won't allow pressure coming in to be higher than pump pressure going out. Also has a minimum pressure of 100psi so it won't "activate" at lower than 100psi incoming.
    "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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    sklump.

    There are several factors to look at.

    What comes off of your pump manifold? Do you have dual intakes or just one? I believe anything over 1,000 gpm has 2. Is there a valve (butterfly or piston) for each one?

    Assuming you have dual master intakes (one each side) and they simply have a blind cap on each one. You will need to purchase an external master intake valve (MIV) for at least one side. Pick your brand. We use Akron Black Max but there are several good ones on the market. Remove the blind cap and thread the MIV on. This will do two things for you. One it will have a bleeder valve that will allow the operator to bleed the air from the LDH so the pump only gets water. Once the air is bled you open the MIV and feed the pump. Two, most MIV's have a field adjustable relief valve. Once it is set anything over X amount of pressure opens the relief valve and dumps on the ground. I believe ours are set at 100 psi.

    Hope this helps. If you have any questions ask.

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    sklump: The short answer is: YES, anytime that LDH is used in a relay situation, there is a risk of water hammer due to rapid closing of a high flow valve. The result will be a pressure spike, and since most supply hose has a maximum test pressure of 200 psi, there is a strong possibility of water hammer pressures exceeding the test pressure of the supply hose. Much of this risk has been controlled by the NFPA's requirements of "Slow Close" valves, but there is always the risk of shutting down several 2 1/2" valves in rapid succession, or on some older Watrous pumps, of the valve "sucking shut" under high flow conditions.
    Where you set the relief pressure is dependent upon the supply pressures you are being fed by, that are not controlled by the relaying engine. (hydrant pressures) InsCLRep referenced static head on pumped industrial systems. We have some areas of our Muni system that run from 175 to 195 psi, and we needed to compromise on our relief valve setting. We opted to allow the relief valves to open initially and dump water, because later when flowing the system the residual drops into the 100 psi range at 1500 gpm. The other end of the problem is to keep the setting low enough to protect the hose under water hammer or surge conditions. Water hammer can easily exceed 5 times the static pressure when rapid reductions in flow occur. The relief valve on the attack engine needs to protect the LDH near the supply engine. As a result there will always be somepressure rise from the relief valve working back toward the supply engine. Suppose the relief opened and dumped 1,000 gpm on the ground at a pressure of 150 psi. 800 ft away at the supply engine the discharge pressure would rise to 198 psi. 150 relief + 48 friction loss at 1,000 gpm through 8 joints. This will occur until the pressure governor or internal relief on the supply engine is able to react.
    bones: Be sure to keep a blind cap handy in a compartment for your built in relief valve. We are finding that many times the internal relief valves are not adequately exercised and as a result some debris ends up undre the seat. This will effectively prevent getting a good draft from a static source. Remember to remove the cap after the operation, or the next time that engine is used for attack you will have no relay relief valve protection.

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