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Hydraulic gauge failure questions

Discussion in 'Technical Discussion' started by ctozz, Dec 31, 2017.

  1. ctozz

    ctozz New Member

    Joined:
    Oct 11, 2017
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    Seattle
    This week we had the pressure gauge on the main hydraulic pump off port engine fail. Hydraulic oil was gushing out the face of the gauge which had cracked. There is a shut valve on the fitting as well that can be used to isolate the gauge.

    I have two questions as we result of this experience: First, is this a normal failure mode? I would have not expected the front and back side of the gauge to be connected in any way other than the springs for the needle which is floating in liquid (glycol?). Second, under normal conditions underway should the valve be shut or opened? I assume opened but I guess that begs the question... what is the true purpose of the shut valve?

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  2. rcrapps

    rcrapps Senior Member

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    Over a few psi, mission critical part of your machinery, you have a valve, you just experienced one reason why the valve is in place.
    These are $20, shopped for & built by the lowest bidder. For many reasons they can leak or explode.

    Close that valve. You have to get close to read it so get closer and open/read/and close when you need to know if you have any pressure.
  3. ctozz

    ctozz New Member

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    Thanks for the reply and information. That's what I will plan on doing from now on. It was open when I purchased the vessel but have gotten good feedback from this and other forums as to the correct procedure. I didn't know the pulsating pressure could weaken the tube in the gauge leading to failure but it makes sense.
  4. rcrapps

    rcrapps Senior Member

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    It could of been stepped on. A tool may have dropped on it. Thermal flexing. Pressure flexing. Old age. Bad luck.
    I have had new gauges out of the box leak or leak in a few days connected to fuel filters.
  5. v10builder1

    v10builder1 New Member

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    Virginia Beach, VA
    All those possibilities are legit - my thought is vibration damaged the bellows in the gauge. The gauge is on a long "arm", and angled as well, away from the threaded port on the pump. It looks like, due to clearance issues at installation, the components chosen may not be the best. If you get a hydraulic valve (with the handle on the side) with male pipe thread at the pump side you can install the valve directly into the port on the pump (may have to take the valve apart to install due to lack of clearance). The valve would have female threads on the other end - the new gauge goes in there, eliminating the tee and the other components. Shortening the arm for more resistance to vibration. I see from the photo the gauge is a Wika brand, quality IMHO. Made quite a mess, I bet.
    Best of luck in the new year.
  6. K1W1

    K1W1 Senior Member

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    The valve will be to isolate the gauge from pulses that may exist in the system. its these type of pulses that can cause the bourdon tube inside the gauge to shatter

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