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Old 12-31-2017, 10:55 AM   #1
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Hydraulic pressure gauge failure

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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Old 12-31-2017, 11:03 AM   #2
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I would leave the valve closed except to check pressure occasionally.
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Old 12-31-2017, 11:54 AM   #3
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Hydraulic pumps have a good bit of pressure pulsation in the output that can fatigue the bourdon tube in a gauge. Worse when located right at pump output.

Leave valve closed unless checking pressure.
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Old 12-31-2017, 11:58 AM   #4
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Hydraulic pumps have a good bit of pressure pulsation in the output that can fatigue the bourdon tube in a gauge. Worse when located right at pump output.

Leave valve closed unless checking pressure.


Thanks for the info and validation. That's what I had planned. Closed unless checking psi but wanted confirmation.
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Old 12-31-2017, 12:00 PM   #5
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I would leave the valve closed except to check pressure occasionally.


Thanks! That's what I'll plan on doing from now on
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Old 12-31-2017, 12:05 PM   #6
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I had pressure gauges on my TD gears. Same MO as Tozz. By luck I caught the leak on my engine room hourly check before the gear completely bled out and was ruined. I shut down the engine and replaced the gauge with a pipe plug. Dodged a bullet on that one.
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Old 12-31-2017, 12:54 PM   #7
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Thanks for the info and validation. That's what I had planned. Closed unless checking psi but wanted confirmation.
Careful!

Closing off hydraulic fluid in a dead end can blow out the gauge. Since hydraulic fluid/oil is essentially non-compressable, any raise in temperature of the fixed volume fluid will result in a pressure increase, possibly far in excess of the gauge FS reading. So, if you shut the valve when cold, at warm/hot, you will see a pressure rise.
My company sees numerous cases yearly of improper valve shutting and piping/gauge damage, at least in outdoor settings.
In your case, there is merit in unattended valve OFF, however, either provide a blow off or an air space in that dead head.
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Old 12-31-2017, 01:03 PM   #8
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Careful!



Closing off hydraulic fluid in a dead end can blow out the gauge. Since hydraulic fluid/oil is essentially non-compressable, any raise in temperature of the fixed volume fluid will result in a pressure increase, possibly far in excess of the gauge FS reading. So, if you shut the valve when cold, at warm/hot, you will see a pressure rise.

My company sees numerous cases yearly of improper valve shutting and piping/gauge damage, at least in outdoor settings.

In your case, there is merit in unattended valve OFF, however, either provide a blow off or an air space in that dead head.


So is there an order of operation that is recommended for a setup like this with the gauge and dam valve?
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Old 12-31-2017, 01:14 PM   #9
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Am I looking at a V drive transmission in that photo?
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Old 12-31-2017, 01:23 PM   #10
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Am I looking at a V drive transmission in that photo?

I have twin disc gear boxes on DD 6v92TA engines. Main hydraulic pump off the port engine.
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Old 12-31-2017, 01:23 PM   #11
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Quote:
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Careful!

Closing off hydraulic fluid in a dead end can blow out the gauge. Since hydraulic fluid/oil is essentially non-compressable, any raise in temperature of the fixed volume fluid will result in a pressure increase, possibly far in excess of the gauge FS reading. So, if you shut the valve when cold, at warm/hot, you will see a pressure rise.
My company sees numerous cases yearly of improper valve shutting and piping/gauge damage, at least in outdoor settings.
In your case, there is merit in unattended valve OFF, however, either provide a blow off or an air space in that dead head.
Thermal expansion of the fluid MIGHT cause gauge to over range, but I doubt it. Easy enough to find out, just look at the gauge and see if it is pegged high.

But the big deal here is that with valve closed, a gauge failure means a... failed gauge, that's it. It will not hurt the gearbox.

If gauge fails with valve open, you can easily lunch the clutches in the gearbox. Not so with valve closed.
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Old 12-31-2017, 01:38 PM   #12
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OK, not a drive system, but a power unit for stabilizers, etc, I suppose?

I would want a 3-way ball valve there, configured for a "L" port.
https://www.vnestainless.com/valves/...ed-ball-valves

This way, when the gauge is "OFF", it is ported to atmosphere, the pump side is closed off.
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Old 12-31-2017, 01:40 PM   #13
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OK, not a drive system, but a power unit for stabilizers, etc, I suppose?

I would want a 3-way ball valve there, configured for a "L" port.
https://www.vnestainless.com/valves/...ed-ball-valves

This way, when the gauge is "OFF", it is ported to atmosphere, the pump side is closed off.

Correct. Stabilizers, windlass, and thrusters all hydraulic.
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Old 12-31-2017, 01:40 PM   #14
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Originally Posted by diver dave View Post
OK, not a drive system, but a power unit for stabilizers, etc, I suppose?

I would want a 3-way ball valve there, configured for a "L" port.
https://www.vnestainless.com/valves/...ed-ball-valves

This way, when the gauge is "OFF", it is ported to atmosphere, the pump side is closed off.


I'll review with my mechanic. He also mentioned the possibility of a pulsation damper.
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Old 12-31-2017, 01:43 PM   #15
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If this was a drive hydraulic pump, then I would launch into my "have the gauge on the dash" mentality, but implemented by few.
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Old 12-31-2017, 01:43 PM   #16
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If this was a drive hydraulic pump, then I would launch into my "have the gauge on the dash" mentality, but implemented by few.

That too.
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Old 12-31-2017, 01:45 PM   #17
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I'll review with my mechanic. He also mentioned the possibility of a pulsation damper.
Yes, they can act as a smoothing device to be nicer to the Bourdon tube inside the gauge.
If you plumb that in the correct spot, then the fluid would have a place to expand into with gauge off.
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Old 12-31-2017, 01:51 PM   #18
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Thermal expansion of the fluid MIGHT cause gauge to over range, but I doubt it. Easy enough to find out, just look at the gauge and see if it is pegged high.

But the big deal here is that with valve closed, a gauge failure means a... failed gauge, that's it. It will not hurt the gearbox.

If gauge fails with valve open, you can easily lunch the clutches in the gearbox. Not so with valve closed.
Agree with the problem risk. Note also, if you do happen to turn ON a gauge that had sustained a overpressure/leak, especially with 1000psi or greater fluids, you stand the risk of blowing out the lens into your eye(s).
Wika is a good quality gauge, and should have a rear facing blowout plug on the case.
Just sayin'. And it does happen.
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