×
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

System not maintaining pressure

System not maintaining pressure

System not maintaining pressure

(OP)
Hi all,

New to the Forum(any forum really) and fairly new to hydraulics but I have an issue I cannot seem to fix. Hopefully someone on here that know a lot more than me can chime in with something I haven't thought of.

I have a pretty simple hydraulic system on a large roll calender (or roll mill) here at work. The machine is used to compress battery electrodes to a desired thickness/density and recently has been unable to compress the electrodes to an acceptable level. A local repair company came out multiple times and after replacing a few valves, and costing a lot of money, the system was still not fixed. We decided after that to just do the work ourselves and replaced all the other valves and the pump itself. The system worked quite well after that for a month or so until someone decided to increase the system pressure and things have all gone wrong again (it has since been reduced to normal and did not exceed the 5000 psi rating of the valves and fittings). I am pretty new to working on hydraulics more complicated than a simple braking system on a car or motorcycle but I understand well the theory of fluid power. I will describe the system the best I can with my limited knowledge of the proper terminology.

The pump goes into a check valve, and then into a stack of 3 manifold blocks. The first and closest to the pump is an RDDA valve, a relief valve. Next is the PRDR, direct acting, pressure reducing. After that it goes into a directional valve and onto the cylinders. The cylinders are what raise the lower roller to a defined gap between it and the upper roller. They are dual acting and there are 2 of them. There is also a nitrogen accumulator.

Now that you have some backstory and the system description, here are the problems. As mentioned above, it no longer can achieve the density desired and also cannot maintain pressure after running for a short time. The system cycles up to 3200 psi and shuts down until the pressure drops below 3000 psi and cycles again. After running for a short time (<15min) the system can no longer maintain pressure and the pump runs continuously with the pressure stalling out around 3000 psi. I have been trying to bleed air out of the system and have got a fair amount out but it does not seem to be making a significant difference and does make sense to me that air in the system could keep it from maintaining pressure after a short time when it was working fine previously. Any ideas or even corrections of some improper terminology are appreciated as I am trying to learn all I can quickly.

https://files.engineering.com/getfile.aspx?folder=... - Cylinder 1
https://files.engineering.com/getfile.aspx?folder=... - Roll calender
https://files.engineering.com/getfile.aspx?folder=... - Power unit


RE: System not maintaining pressure

Have you got a schematic diagram for the circuit. If you have, it would be worth posting a copy (recommend using the image button rather than posting links to files in the cloud - people are understandably cautious about downloading files off the net).

If you haven't got a schematic, it would be a very useful first step to try to draw one (based on datasheets for the components and your best understanding of how they go together). As well as giving people here something to work with, the act of putting the schematic together will help you understand your system and may well lead you to work out the solution for yourself.

A.

RE: System not maintaining pressure

Make sure your relief valve is set higher than your pressure reducing valve, oil running through the relief will generate heat quickly. Also check the accumulator pre-charge.

Rich

PRA

RE: System not maintaining pressure

#1, your reservoir is very small and may contribute to a high operating temperature which will result in short seal life.

#2, your system appears to have an accumulator. Without a proper gas charge this will cause short cycling.

RE: System not maintaining pressure

If the pump is running continuously at 3000 psi and still moving any quantity of fluid, it will be generating heat somewhere, wherever the fluid goes from 3000 psi to atmospheric pressure before returning to the tank. Finding where that heat is generated will tell you something (if you have an IR camera they're great for this, but a bit overkill for this system). I'll second zeusfaber's suggestion to get the schematic (and posting it here). Trying to troubleshoot a hydraulic system without a schematic is pretty useless, at least I find it to be.

It would also be a good idea to take a look at the controls side of this system to make sure you don't have an problems there and to understand what is supposed to be happening.

RE: System not maintaining pressure

You have 4 links to images.
If you use the "Camera/Image"-button those images will show on the screen and you will have a much better chance to engage someone with a good answer for you.
The attachment feature is meant for text documents

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