×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Hydraulic Life Calculation??

Hydraulic Life Calculation??

Hydraulic Life Calculation??

(OP)
How do you calculate cummulative damage on a pump?  It is fairly straight-forward with structural components through the use of Rainflow analysis, level-crossings, etc..  However with pumps, if you have real-time pressure, flow and temperature measurements, how do you combine them into a damage assessment?  Thanks in advance!

RE: Hydraulic Life Calculation??

Many manufacturers will give you an estimated design life
in hours based on various RPM's @ a certain pressure/flow
rates based on years of field testing, but I've found those
to be about as reliable as the operating environment of any
pump.  Maintenance and abuse are HUGE unknown key factors.  

Hydraulic pumps are prone to environmental conditions and
contamination damage which can take place in several hours
at any point in an expected 5,000 hour life span.  Using
non spec or aging hydraulic fluids can have a minimal effect
over time until wear particles contaminate the fluid to a
point that wear rates increase exponentially over a few
hours.  Cavitation damage due to air entrainment in the
working fluid can also be a major wear issue.

For my non critical applications, hydraulic pumps get the
black or white test of, "After an internal visual and
measurement inspection,  Do they meet the specified flow
and pressure requirements without making excessive noise,
vibration or leaking fluid?  If yes, you're good to go!

From a budget standpoint, its a good idea to ask yourself,
what will this cost if a questionable pump goes out in a
worst case scenario at the least opportune time and is it
worth spending the money to avoid that?

In critical applications like aircraft, spacecraft,
submarines, nuclear reactors, etc., if those concerned
are doing their job correctly, once any pump hits its
rated life span, even if it looks, works, and sounds
perfect, it goes into the trash can and gets replaced
with a new pump.  You'll find that in many critical
applications, in addition to hourly and/or cycle time
design life limits, double, even triple system redundancy
is often the best policy.  Aircraft engines, which are
really just hydraulic pumps, are a good example.

The short answer is, there's no sure way to accurately
estimate the design life of hydraulic pumps.


Chumley

RE: Hydraulic Life Calculation??

A rough rule of thumb that I use is the life is a function of horsepower*hours.  Take the rated life and horsepower, and then keep this number constant.  As you draw more horsepower from/through the pump, the number of hours to failure decreases.  I use this as a linear relationship, and it works well as long as the system is kept within NORMAL operating limits (i.e. no cavitation/turbulent flow).

RE: Hydraulic Life Calculation??

(OP)
Thanks.  I like the horsepower idea.  We have been theorizing about using some form of Energy Analysis or even calculating Herzian stresses and trying to figure out a damage analysis from that. Any other ideas?

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

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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