1. #1
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    Default Intake pressure for relief valves & governors

    Looking for input on proper procedures for controlling/adjusting intake pressure when pumping from a pressure source (normally hydrant supply) on apparatus equipped with 1. relief valve and 2. governor

    Question:

    1. Is gating down the intake pressure the most appropriate method to control high intake pressure from hydrant source?

    2. Is it necessary to control intake pressure when using a governor pressure control system?

    thanks

  2. #2
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    No it is not necessary to gate the intake pressure down. More pressure (to a point) on the intake side is less that your engine will have to work to get the outlet pressure required. Less engine work equals less fuel burned and less wear and tear on the pump. NFPA recommends intake valve relief no more than 10 psi above normal static water pressure. Or 10 psi over what your department relay pumping procedure calls for as a starting pressure.

  3. #3
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    Depending on the age of your units, the intake should per NFPA 1901 have a preset intake relief valve. This valve should be set around 110 psi. If you have more than 110 into the pump it will dump the excess to the ground. NFPA states that a relief valve will open within 30 psi of its setting. The governer will automatically raise or lower the engine rpms or adjust the water as needed. Remember however that nothing is instant. Some times I have seen where the gov and relief valve being set properly will react slower than other times. You can check on the various mfg websites for proper operation of both. Good luck be safe jeff

  4. #4
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    as a side note if you have a relief valve that is operating slow, on hale pumps there is a strainer in the discharge side of the pump that allows water to the pilot valve( control on panel). It appears to be nothing more than a brass fitting but if you remove the line going to it and then the fitting there is a screen on the end that filters out trash. If this has never been serviced, you need to replace it as it will make the system slow or not reactive. Waterous also uses a similar type of strainer. Jeff

  5. #5
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    Default intake pressure

    On our newer apparatus that are equipped with poly-tanks, there is a note on the pump panel that advises against filling the tank above 100psi.

  6. #6
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    Restricting a pump intake is never a very good idea because that cuts down the available water and the pump discharge pressures will vary a lot every time someone opens or closes a line.

    Some of our hydrants have over 110 psi in them and gigantic mains so their pressure never really drops when flowing water. If the main has enough pressure you might even drop the truck transmission into neutral if the hydrant has enough pressure to supply the lines directly. Keep the switch/air valve in "pump" though so you can shift the transmission back into drive if you need more water in a hurry.

    Otherwise just do like you would for any discharge that needs less pressure than what your pump is supplying, gate down the individual dicharges.

    Birken

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