Bulk Modulus and Hydraulic Oil Pressure

[MolaKule]

The Bulk Modulus is defined as the ratio of volume change to pressure change in a liquid.

In a hydraulic fluid, what is the percentage of volume change for each 1,000 psi of increased pressure?

Let's let the general membership answer this question so chemists, ME's, tribologists, formulators, etc., please refrain from answering.

Guidelines for the Question of the Day:

1. No Piston Cup Lapel Pin will be awarded to the same person within 14 days of a previous award.

2. Please respond with a complete sentence or explanation.

3. Please do not post links. If a question arises as to the need for clarification, then sources and links may be requested.

4. Please, no off topic posts.

 

[CT8]

It depends on certain factors.

 

[A_Harman]

There are probably different fluids out there with different bulk moduli, but how about 300,000 psi for MIL-H-83232? That means that the fluid volume will change 1% at 3000 psi, or .33% at 1000 psi.

Other Bulk Moduli:
Gasoline is 150,000 psi
JP4 is 200,000 psi
Water is 310,000 psi.

 

[MolaKule]

A fluid's Bulk Modulus depends on pressure, temperature, chemistry, and structural (molecular) rigidity.

Let me state the question this way:

As a rule of thumb for a hydraulic fluid:

For each 1,000 psi step in increased pressure - what is the percentage of volume change?


Let's let the general membership answer this question so chemists, ME's, tribologists, formulators, etc., please refrain from answering.

Guidelines for the Question of the Day:

1. No Piston Cup Lapel Pin will be awarded to the same person within 14 days of a previous award.

2. Please respond with a complete sentence or explanation.

3. Please do not post links. If a question arises as to the need for clarification, then sources and links may be requested.

4. Please, no off topic posts.


A Harmon is on the right track.

 

[53' Stude]

61%

 

[Shannow]

I know the answer, but it's still better than using pneumatics.

 

[CR94]

Originally Posted By: MolaKule
... A Harmon is on the right track. ...
That answer looks good in principle to me, although the volume change is negative. Are you looking for a "-" sign?

 

[SuperSalad]

Originally Posted By: CR94
Originally Posted By: MolaKule
... A Harmon is on the right track. ...
That answer looks good in principle to me, although the volume change is negative. Are you looking for a "-" sign?

Correct me if I'm wrong Molakule, but what I think he is saying is that he is looking for a rate of change in the volume, whereas A Harmon provided the percentage change at specific pressures instead.

 

[MolaKule]

Originally Posted By: CR94
Originally Posted By: MolaKule
... A Harmon is on the right track. ...
That answer looks good in principle to me, although the volume change is negative. Are you looking for a "-" sign?


For each 1,000 psi step in increased pressure - what is the percentage of volume change?

Or stated another way: If I increase the hydraulic pressure from 1000 psi to 2000 psi, how much does the volume change in terms of percentage?

The hints here are change and percentage, with percentage expressed as a positive number.

I said A Harmon was on the right track; I did not not say he gave the correct answer.

 

[BeerCan]

Ok I am way way out of my element here but I decided to see if I could find the answer.
First I do not know the answer yet, a lot of the stuff I read is still marinating.

Second, does the answer have something to do with this formula? BT = V0 (dP/dV)


Edited to add that near as I can figure we are looking at a ~0.33% reduction in volume for a 1k psi pressure increase.

 

[MolaKule]

Originally Posted By: BeerCan
Ok I am way way out of my element here but I decided to see if I could find the answer.
First I do not know the answer yet, a lot of the stuff I read is still marinating.

Second, does the answer have something to do with this formula? BT = V0 (dP/dV)


Edited to add that near as I can figure we are looking at a ~0.33% reduction in volume for a 1k psi pressure increase.


As a rule of thumb, the volume of a hydraulic fluid decreases by about 0.5% for each 1000 psi increase in pressure.

So BeerCan receives the Piston Cup Lapel Pin for the closest answer.

In a recent test, a Group V phenyl ester exhibited the lowest torque losses in a hydraulic system because of its high Bulk Modulus.

 

[BeerCan]

W00T W00T

It was a fun problem. I exercised my brain and learned more about hydraulic pressure than I will ever need to know

 

[Shannow]

I built one of these in the late 1990s.



but quite a bit bigger... google maps -33.404989, 150.089308.

The boom was 100' long...the movement in the ram was hugely amplified at to pointy end.

(also introduced me to dieseling in hydraulics when the lip seals started to ingress air on the bounce)

 

[MolaKule]

Originally Posted By: Shannow
I built one of these in the late 1990s.



but quite a bit bigger... google maps -33.404989, 150.089308.

The boom was 100' long...the movement in the ram was hugely amplified at to pointy end.

(also introduced me to dieseling in hydraulics when the lip seals started to ingress air on the bounce)


Smooth!

Is that an aggregate they're pouring?

 

[Shannow]

It's coal, it's a Schade circular stacker reclaimer.

Has two modes of operation, stacking, where the boom stays at full height, piles the coal, then when it reaches full height indexes around a bit.

The mode in the video is "Chevcon", where it stroked backwards and forwards, up and down "painting" a layer of coal over the top of the last...diagonal layer cake for blending different sources.

Look at 0:13, and you can see the harrow, with tines that scrub across the retreating face, causing the coal to trickle down the face, and into the bucket chainwheel at the bottom and into a chute that leads to an underground conveyor.

We had to build the dome, while still building the tunnel to meet programme, it was really interesting at the time...ours held 35,000 tonnes of coal, which was enough for 3-4 days running in the best of times.

Alas, that station has been killed...

 

[userfriendly]

Go to www.westshore.com

On the cover page you will see a long conveyor from the coal pile to a ship.

One day, a coal ship captain thought he would take a short-cut and drove a million ton, give or take, ship through the conveyor.

 

[Shannow]

ouch..

 

[DriveHard]

DANG! I wish I would have seen this problem sooner. I deal with this stuff every day!