Thread: Pump operations

  1. #1
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    Default Pump operations

    I'll keep it simple. Mini Pumper pumping water to engine,One 3 inch line 100psi. Pump operator of engine shuts down intake line causing extreme back pressure to Mini Pumper to the point of the truck shaking. My question is should under this sceneraio the relief valve kicked open to keep this surge from happening or is the relief valve just for multi line operations? The Mini operator said he always needs to shut down first to avoid this or a hose could snap etc. I think the relief valve should open up or something. Let me know what you think.

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    Question

    First, let's get our assumptions in order.

    1. Let's assume the minipumper has a relief valve, that it is exercised periodically and that the pump operator has it set correctly.

    2. The pump operator is pumping the line at 100 psi with the intake valve on the receivng engine in the open position.

    Yes, if the intake valve is closed, the pressure should begin to spike and the relief valve should open.
    Remember, it IS as bad as you think and they ARE out to get you!

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    Default

    Yes, relief valve should have opened, if it was set correctly. The extreme pressure causing the truck to shake should never have happened. If the minipumper operator was doing his job, he should have noticed the pressure increase almost immediately, radioed what was going on, and throttled back to decrease the pressure.
    "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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    I'm a firm believer in always taking a look at the relief valve setting to make sure it didn't get put away with the valve setting way too high. I also agree with the earlier post that referred to exercising the relief frequently to be sure it is working properly. These two items are no less important than making sure your SCBA is functional and full before use.
    Lt. D. Gordon
    Greendale Fire Department
    Greendale, IN

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    Exclamation GO SLOWLY

    I agree with all above. Another point to make is that all valves should be opened and closed slowly. For a hammer to occur, the engine intake must have been closed quickly. If the mini was connected to hydrant, the pump would still get hammered on the intake side. Most relief valves dump discharge back to intake. There's no where for the flow from the hydrant to go. Slow the flow down before you stop it.

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    Red face

    This is a point in which the relief valve was working according to the design, but didnt work. Now that I've confused you, let me explain. In order for a relief valve to work, there has to be a minimum of 60 psi difference between the intake and the discharge pressures. The way the relief valve is designed, it won't work with a difference less than that. I have no idea what the water system is like in your area, but here, our pressure is 80 to 90 psi prior to flowing water. With flowing through a 3" line, I don't think there would be enough flow to reduce the residual pressure to 40 psi. Also, a relief valve starts to work at 90 psi. Thats to NFPA standard.

    Also, as far as valves opening and closing, if the intake valve on the big engine was an air valve, I'd be hard pressed to think that it closed slowly, and there is nothing the operator can do. We have an engine with air operated intake valves (6", both sides) and they are air operated. When you open them with the supply line charged, the whole truck shakes back and forth. This is one reason why wont be putting air valves on the valves of any trucks. Its either open or closed, no feathering of the valve is possible.

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    Originally posted by gordoffemt
    I'm a firm believer in always taking a look at the relief valve setting to make sure it didn't get put away with the valve setting way too high.
    Maybe I'm confused, we've always been taught that after pump operations, the relief valve should be turned up (set at higher pressure). So in theory when the next person uses the pump, if the valve were to malfunction, atleast you'd be able to pump the truck. We've never had one of our fail, mainley because our drivers (15 of us) have to do quarterly driver training so the relief valves are worked almost weekly.

    Pardon my spelling and punctuation, I just woke up!

    -Nick

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    Default Pump operator

    If you are relay pumping with a Hale TPM when the pumping engine shuts down, the supply engine would dump to the ground automaticly through the TPM. As the pumping engine opens his discharge and the demand for water returns the TPM compinsates and closes stopping the dump to the ground.
    Regular relief valve may not be able to compinsate because the water has no where to go but from one side of the pump to the other. You need to be on top of your operation with a regular relief valve. Hope this is of help. Hopefully it will cause more replies.
    Last edited by rodeohoser; 06-03-2004 at 01:43 PM.

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