×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Need some help with a math question

Need some help with a math question

Need some help with a math question

(OP)
I swear I've lost my marbles... they are somewhere around here.

A cylinder has a PO operated check on both rod and blind ends.  The ratio of these checks is unknown.  The cylinder is extending and lifting a load of 10,000lbs.  The dimensions of the cylinder are 5 x 1 x 30.  The cylinder is stopped mid stroke and both checks close.  The cylinder develops a leak across the piston seal.  What would the pressure gauges at the blind port and rod port read once the cylinder stops moving.

I know the gauges will equal out, and cylinder drift will stop before bottoming (if there is enough fluid to lock it).  I know it takes about 510 psi to raise the load.  Why is 510psi not the correct answer, and how do you find the correct answer?

Thanks;
Chris

RE: Need some help with a math question

Hello,
The forces must equalize for the cylinder to halt retraction.
444482.2N force
3.517MPa to hold
Leak in piston seal - Pressure must equalize on both sides now
Presuming 35.17bar in FA when po checks seat.
Pressure in AA unknown presuming 0
Cylinder Area ratio = 1.04:1
Presuming no leaks and fluid incompressible
AA new pressure due to leak = 3.517MPa
AA new force due to leak = 87252.3792N
FA new pressure due to leak = 6.88MPa
FA new force is surprisingly enough = 87252.3792N
At this point the cylinder is hydraulically locked. But can be displaced back and forward within the volume limits.
I think that's right. But do shoot me down in flames if it's wrong.

RE: Need some help with a math question

(OP)
Ok, let me describe the process and please correct me if I am wrong.  First, you found what pressure would support the load on the blind end of the piston (described as FA).  The pressure from FA would equalize to the AA, applying 510psi (3.517Mpa) additional force with the 10Klb load, causing the blind area (FA) pressure to rise to meet the new demand for pressure (AA+Load).

Correct?

RE: Need some help with a math question

Good morning,
Yes that's correct.

RE: Need some help with a math question

When the piston seal leaks, the effective force area is that of the piston rod.  So pressure will increase to support the load.

Ted

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper - PLM and ERP: Their Respective Roles in Modern Manufacturing
Leading manufacturers are aligning their people, processes, and tools from initial product ideation through to field service. They do so by providing access to product and enterprise data in the context of each person’s domain expertise. However, it can be complicated and costly to unite engineering with the factory and supply chain. Download Now
White Paper - Medical Device Design Control
Medical device product development is a highly integrated and regulated process. Implementation of a requirements tracking solution requires attention to a variety of nuanced topics. When presented with the task of tracking the many concept relationships in a project of this type, the initial software solution of choice tends to be a two-dimensional text systems. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close