Relief Unloading Valve and Pulsation Damper in Hydraulic System

[Cool SH]

Refer to the photo.

Unloading valve set pressure = 130 bar
Pulsation damper pre-charge N2 pressure = 50 bar
Pulsation damper nominal liquid volume = 1 liter

Consider the following scenario. Pulsation damper gas valve is leaking gas. As liquid is incompressible, in order to reach 130 bar hydraulic set pressure, more than 1 liter of liquid need to fill in the pulsation damper.

The volume of the whole system now is more than the calculated volume. Does the temperature of the hydraulic oil increase as the above scenario happen?

Thanks in advanced.

 

[btrueblood]

No photo?

"As liquid is incompressible, in order to reach 130 bar hydraulic set pressure, more than 1 liter of liquid need to fill in the pulsation damper. "

So the total volume of the dampener is greater than 1 liter? Or are you leaking fluid as well?

Shouldn't have any effect on the oil temperature in itself, but if system run time is longer to reach operating pressure, then maybe that accounts for a change. Did oil get added to the reservoir to accommodate the stuff now held in the dampener? Does running without a dampener air pad cause more bypass flow due to pressure pulsations, and/or has the excess chatter on the bypass caused it to leak excessively - both things can cause an apparent temperature rise, esp. if the pump is a variable-volume type.

 

[gerhardl]

Or sketch?

 

[Cool SH]

Sorry for the late reply. I live in SEA. Please refer to the sketch.

Yes. The volume of dampener is greater than 1 liter. Only gas is leaking at dampener. By right the time taken to reach operating pressure is more, but that is in the range of a few seconds.

No oil is added to the reservoir. The pump is a gear pump, fixed volume displacement pump.

 

[gerhardl]

No. I cannot see anything changing temperature here, except that a leaking N2 valve leaking considerably might be cooled down, and a motordriven pump overworking cold be hot. I dont believe this to be differences enough to influence oil temperature.

Solenoid valves might naturally (depending on construction and if electrically held in a 'normal' position) reach as much as 80 deg C.


PS. What is your 'real problem'? Just wondering!

 

[Cool SH]

I have a hydraulic system with manifold and cartridge valves. Oil is leaking for the manifold. When inspect, found that some o ring is damage. The temperature of hydraulic oil is high enough, that cause the damage of the o ring.

High pressure in system will increase the temperature. I don't know whether is the relief unloading valve , or the pulsation damper, which is connect after the relief valve, has faulty.

If relief unloading valve is not functioning properly, that's the pressure in the system will rise more than the set pressure. Then the temperature of oil will increase.

Or the pulsation dampener is unhealthy, gas leak from the gas valve, cause the volume of oil to increase, that will cause the temperature to increase.

 

[hydtools]

Additional oil will not raise temperature. Wasted energy like internal valve leakage increases temperature. Without damping, pressure pulses will open the relief valve causing increase in temperature.

Ted

 

[btrueblood]

"No oil is added to the reservoir."

So volume of system increased, no oil was added, that means reservoir level dropped. Question is, did it drop enough to cause cavitation or incipient cavitation in the pump - that could show up as increased heat. In addition to the bypass leakage. Do you not have an oil cooler for this system?

 

[Cool SH]

I don't have any oil cooler for this system.

I never thought of the cavitation problem until you brought this up. Thanks for the comment. I will check the system once i go to site again, which is next month.

As of now I will try to study the system through theory and PID

 

[LittleInch]

What is this system servicing? I can't really see the volume in the damper being big enough compared to total oil volume to make any difference.

However operating with the damper being ineffective and operating at a higher pressure is likely to increase flow through the relief valve and thus increase temperature over time if you have no cooler.

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