×
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

HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

(OP)
I have a vendor design for driving cooling fans with hydraulic motors in series.  The motors have internal case drains.  Is this a problem?  Could the first motor in series see a detrimental back pressure from the second motor?

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

Both motors must be rated for full supply pressure.
First motor _should_ see a backpressure of roughly half the supply pressure unless the second motor has somehow failed open.
Both case drains should go to the tank.

...  Ah.  Now I understand your question.

If the case and shaft seal of the first motor are not rated for full system pressure, there might be a problem.  See the motor cut sheets.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

Yes.  The first motor shaft seal will see the operating pressure of the second motor.  Motors with internal case/seal drains expect the motor outlet port to be connected to low, return line pressure.

Ted

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

(OP)
I would have to agree ... the ramification here being?  Elevated case pressure? Reduced motor life?

Any estimates?  We are working with 2500 PSI system with each motor/fan at ~ 17HP.

We also have the fans controlled by proportional relief valve.  Worse when max power to fans, yes?

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

Reduced shaft seal life.  No quantitative guess as to how much.  If shaft seals are desiged for 100psi, max, and are operated at 1250psi, maybe seal life will be reduced by ~90%.  What is the original design life?

Control flow, not pressure, to control fan speed.
Do you know that the motors will, in fact, demand full system pressure capacity?

I'd recommend a parallel motor arrangement with individual flow controls to control motor speed.  Maybe some thermal feedback to control motor speed.

Ted

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

(OP)
Thanks for the expert direction.  We are making arrangement for dedicated drains.

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

As a general rule, shaft seals should not be exposed to any more than 0.5 - 3.0 BAR, depending on the type, manufacturer and application. To avoid possibility of seal failure, it is always recommended that casing drains are returned to the reservoir with the minimum of restriction.

Although I have personally seen an application where the shaft seal contained the casing pressure up to 300 BAR. The cast iron case of the motor was the weak link, it cracked.

There are always exceptions, but to be sure, they really need to be separate.

Adrian

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

Not to mention you could also just blow the seals out! ISZ

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

Yes series motors should have drain ports connected direct to Tank

RE: HYDRAULIC MOTORS CASE DRAIN REQUIRMENT WHEN IN SERIES

fit check valves on each casing drain to prevent inter communication ,or alternatively pipe the drains separately to the reservoir.

Offshore Engineering&Design

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

eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
White Paper - Comparing Multi-Patterning at 5nm: SADP, SAQP, and SALELE
Self-aligned multi-patterning techniques such as SADP, SAQP, and SALELE are increasingly popular at advanced nodes, but each process has its pros and cons. IMEC and Mentor, a Siemens business collaborated to identify potentially less-obvious process and design limitations and trade-offs between the three SAMP techniques. Learn more in this paper. 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