Test your Hydraulic Knowledge Here

[milldrone]

Problem #6 from Bud's brain teasers

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Edit: I should have added that the existence of the flow control implies that the relief valve is lifted off it's seat.

 

[gbradley]

Are you saying that in condition 2, that the piston will just stay there?
Doesn't it show a blown piston seal?
Can't the oil go by that blown seal?
It seems to me that the piston will travel to the bottom, and then stop.
What MasterBlaster said.
OH Wait,,, scratch that.
Now I finally get it, you can cut that piston all of the way down to the rod size, and it will still hold the 10,000#

 

[fluidpower1]

Vaughn wrote:
"And Heat Generator"
All circuits that use Flow Restriction by causing a Fixed Volume Pump to send oil across a Relief Valve or a Pressure Compensated pump to operate at Compensator seting, Generate Heat. Some more some less but all do.
Once you learn it is Wasted Energy (Energy In That Does No Work) it is often easy to design a hydraulic circuit that does not require a Heat Exchanger and never heats up more than 40-60 Deg. F. above ******t temperature.

Then there are Proportional and Servo circuits that always require a Heat Exchanger since they function very inefficiently to get the required precise control they are capable of.

 

[Peter Nachtwey]

Picky, picky, picky but you know I am right.

The answer is 1001.47 psi not 1000 psi.

Actually the 1000 psi answer is only valid if the initial internal pressure is 0 psia. If it is 0 psig there would be a vacuum on the B side of 14.7 psi so there wouldn't need to be 1000 psi on the A side. Just 1000-14.7 psi. The right answer using psig would be 1000-14.7+1.47. The B side would now be -14.7 psig.

Now what does the oil weigh?

Can you see why I got into a lot of arguments with instructors about test questions?

 

[fluidpower1]

Peter asked/stated:
"Can you see why I got into a lot of arguments with instructors about test questions?"
I would have never guessed that would ever be possible Peter!

 

[fluidpower1]

Peter also wrote:
"Just 1000-14.7 psi. The right answer using psig would be 1000-14.7+1.47. The B side would now be -14.7 psig."

Do you really think oil compressibility and cylinder stretch would allow enough Piston Travel to reduce the "A" side to minus 1 Atmosphere?

Seems very unlikely to me.

 

[TConnolly]

...and heat generator

A trick I got from Bud was to use a solenoid unloaded relief valve in the off line filtration loop in series between the pump and the filter to warm up a cold oil tank, so although I try to minimize heat generators, they are not always a bad thing.

 

[milldrone]

Peter asked/stated:
"Can you see why I got into a lot of arguments with instructors about test questions?"
I would have never guessed that would ever be possible Peter!

Bud,

I think you nailed it!

 

[gas]

Alaric's problem given here as a quiz can be a real life problem. I have seen instances of rod seals blown off, valve internals blown apart or other failures from super high pressure in an old system 750-1000 psi.

The cause....you guessed it. I can remember someone replacing rod seals over and over until he "figgered it out".

Experience is that marvelous thing that enables you recognize a mistake when you make it again.

 

[fluidpower1]

Alaric's problem given here as a quiz can be a real life problem. I have seen instances of rod seals blown off, valve internals blown apart or other failures from super high pressure in an old system 750-1000 psi.

The cause....you guessed it. I can remember someone replacing rod seals over and over until he "figgered it out".

Experience is that marvelous thing that enables you recognize a mistake when you make it again.

I still marvel at the fact that after all the years that Fluid Power has been in use in so many places, that there are no or at least VERY FEW TRAINED/DEDICATED Persons like the Electrical and Mechanical field has.

After 20 years of asking why and making argumenst for TRAINED/DEDICATED Fluid Power Persons it appears the main way to learn Fluid Power is the old College of Hard Knocks.

If I was just starting my career knowing what I do, I would learn evey facet of Fluid Power and hold Training Sessions and do Circuit Design and Redesign and Trouble Shooting for anyone willing to pay my way. BTW, the Training Sessions are primarily to get known so the Trouble Shooting work picks up.

However at 75 and taking care of my wife who had Colon Cancer my Trouble Shooting and Training days are curtailed to say the least. Presently she is doing well but has a problem with my getting very far away. I only bring that up to let everyone know that, except for the forums, my contacts with the industrial world are nil.

Quite a few years back I heard a saying from and elderly person that went, "Old Age is Not For Sissies" which seemed odd since I was so busy that setting around sounded like a great way to live. But as another saying goes "Now I Are One" and I understand the first saying a lot better.

 

[Peter Nachtwey]

Bud,

I think you nailed it!

I saw that. I have been informed indirectly via a telephone call that I am nuts. +1.47 psi. Oh well.

However, GLK once told me that a pile driver system he was working on was unintentionally compressing a large volume of air and it affected the motion.

It is all a mind game until the little things make a difference. Then things then the difference can be costly.

 

[TConnolly]

Alaric's problem given here as a quiz can be a real life problem.

It's actually from fluidpower1's brain teaser page, he gets the credit, not me. I never encountered the problem where it would generate really dangerous pressures but we did have a tooling handler on a press once that wouldn't retract. Because of the blown seal the piston would only extend. Bubba literally jacked it right off its rails and nearly tipped it over because he didn't realize why the piston would not retract. When Bubba and Cletus finally called me they were just sure something was wrong with the controller.

I saw that. I have been informed indirectly via a telephone call that I am nuts. +1.47 psi. Oh well.