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  1. #1
    Junior Member
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    Mar 2004
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    Caseyville,IL
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    16

    Question suction intake relief valves?

    I am looking to increse the flow into my trucks by using the second large suction intake. Do I need a second relief valve setup, like a piston intake or will a simple gate valve work since a centrifical pump will flow through and the primary intake has a relief valve? Any help would be appreciated. Thank You.


  2. #2
    Forum Member
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    Apr 1999
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    Maine
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    Default

    The purpose of a relief valve is to prevent damage to the pump by any unexpected water surge. What will you be doing with this suction intake? If you will be using it for drafting operations, no relief valve is necessary. If you will be receiving water from a hydrant or another pupmper, a relief valve is cheap insurance against pump damage.
    Remember, it IS as bad as you think and they ARE out to get you!

  3. #3
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    Essex Junction, Vt.
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    Default

    Technically, you won't NEED it, since the pump inlet is a common area to both sides, as long as you don't shut off the valve with the pressure relief. If you shut it for any reason, you will be unprotected. If it were me, I'd put relief valves on both sides, as Jim917 said, it's cheap insurance. By the time you've paid for a gate valve (and they aren't all that cheap), you'll be most of the way to the cost of a relief valve. If your serious about making the change, go all the way.
    Last edited by TWEJFD; 03-05-2004 at 01:52 PM.
    TW
    Essex Junction Fire Dept.
    Vermont

  4. #4
    Forum Member
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    Nov 2003
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    51

    Default Intake valve

    Hi I have a couple questions. If you have suctions on both sides of the truck that are common with each other the amount of water coming into the truck will be equal. an intake relief valve simply does this. If you set the valve at 100 psi and hook up to both suctions and could flow 200 psi of water into the pump it will still open at 100. I guess my question would be this. Why would you want to flow more water than the pump can deliver? Remember the releif valve simply opens when the pressure not the gallons reach the preset setting. The purpose for the Intake relief valve is one for not over pressuring the fire pump and causing structural damage to it and also to aid in keeping FF safe when changing over.

    How many gpm at what psi do you want to flow into the pump? What kind of pumps do you use? Also this will go against NFPA 1901 and 1911. A fire pump is rated at a draft and 150 psi. If you flow higher pressure than 150 you loose output from the pump. Let me know what you come up with. Jeff

  5. #5
    MembersZone Subscriber
    Join Date
    Jan 2001
    Location
    MA
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    157

    Default

    I am looking to increse the flow into my trucks by using the second large suction intake.
    Good idea. Every engine should have at least two gated intakes

    Do I need a second relief valve setup
    Yes. Every gated intake should have a pre-set PDV on the upstream side of the valve.



    If you have suctions on both sides of the truck that are common with each other the amount of water coming into the truck will be equal. an intake relief valve simply does this.
    So what do you do when your supply line is charged too quickly and you have 200psi of water hammer flying through the line?

    Why would you want to flow more water than the pump can deliver?
    Because centrifugal pumps are designed to greatly exceed their rated capacity when supplied from a positive pressure source. Not to mention the fact that most of the time you will never be able to supply your pumps to capacity with a single supply line. I think the question should be why not.

    Also this will go against NFPA 1901 and 1911
    Care to explain this one? Adding a second intake relief valve violates NFPA? I don't think so. In fact, if they REQUIRED that every intake be equipped with a PDV on the upstream side of the gate, they wouldn't have to put those silly warning stickers on stating that death or serious injury may occur if the intake is supplied from a pressurized source.


    A fire pump is rated at a draft and 150 psi. If you flow higher pressure than 150 you loose output from the pump. Let me know what you come up with.
    What does this have to do with anything?

  6. #6
    Forum Member
    Join Date
    Nov 2003
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    51

    Default explaination

    I guess terminology is the question. When you say suction relief valve are you talking about a valve that is installed onto the steamer? I am when you say suction relief valve thinking of a true relief valve that is tied into the suction side of the pump plumbing. Either way they both have setting to keep you from overpressuring the pump. If the mfg of the pump wanted 200 psi in the pump they would not put a relief valve on the pump to keep it from exceeding 100 -130 psi. When i say it goes against nfpa i mean it takes away from the fact that they have in the standard that a pump will have a suction relief valve to keep you from building too much pressure. As far as the last statement having anything to do with the question. again it goes to the misuderstanding of what the statement was in the beginning. Sorry for the information i posted earlier.

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