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How does a hydraulic check valve work?

Discussion in 'Technical Discussion' started by Pascal, May 15, 2024.

  1. Pascal

    Pascal Senior Member

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    So we re replacing hydraulic hoses on the pistons that lift the garage pods. They are original braided SS hoses and have corrosion spots.

    we are holding the pod in the open position using the rod I set up after that bolt failure a couple of months ago

    in the process I noticed the cylinder seems to be holding pressure after the hoses were disconnect and found this check valve just outside the cylinder.

    I understand that the check valve will prevent fluid from leaving the cylinder causing the pod to go down in case of hose failure but how does the fluid leave the cylinder when the pump is retracting the cylinder? Is the check valve set to give in under the high pressure sent by the pump?
    Confused. :)

    Attached Files:

  2. vacser

    vacser New Member

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    Pascal, I had the same valves on my forklifts at the high and dry I owned. If a failure of a hose occurs, the cylinder will fall so fast that the check valve will close. If we tried to lower a boat to fast, the check valve would close and stop the cylinder from lowering. It's has nothing to do with pressure be how much flow passes through. Hope I explained it OK
  3. Capt Ralph

    Capt Ralph Senior Member

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    We are replacing some Marquipt davit cylinders on a customers Hatt.
    On the bottom of these rams is a fail check valve.
    It has to have pressure from the pump to open. I suspect you may have the same thingie in-line as I think is in the picture or on the bottom of the cylinder.

    When the job is complete, I may open a new thread on this project.
    !cid_01b301d651b0$5a3dc5a0$1401a8c0@RC77.gif
  4. Pascal

    Pascal Senior Member

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    If it is flow and not pressure which release the inline check valve, then I wonder why when we disconnected the hose the door didn’t go down out all. Odd.
  5. Pascal

    Pascal Senior Member

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    The fail check valve are different than inline. They have another port to release the valve

    I wonder why TNT didn’t use check valves on their platform lifts to prevent the platform from falling down when a hose fails. Happened to us a couple of years ago. Now we set up a heavy duty ratchet strap in the cockpit as a safety when crossing open water. Pita.
  6. vacser

    vacser New Member

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    This guy does a good job explaining how the cylinder is locked with no pressure. You could add this to your door.

  7. K1W1

    K1W1 Senior Member

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    That's not a bad video, I was relieved when he mentioned why he was doing it all with adjustable wrenches. I hate those things for regular work.