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

Minimum recycle line for reciprocating compresor

Minimum recycle line for reciprocating compresor

Minimum recycle line for reciprocating compresor

I have been requested to consider a minimum recycle line for a variable speed electrical reciprocating compressor train which it should be used to protect the system for the train blocked discharge case.

For a centrifugal compressor, it is normal to consider a minimum recycle line but for a reciprocating compressor I believe if it is necessary to consider a recycle line, it should be designed for full compressor capacity.

The compressor train has three stages each stage has:
1) A recycle line to maintain the suction pressure of compressor
2) High high pressure trip.
3) Pressure relief valve as ultimate protection of the system.

The overall train recycle line can protect the compressor for the following cases:

1) Manual valve at the train discharge shut close- this can be avoided by considering LO valve.
2) Check valve at the train discharge shut close- this can be happened during compressor start up. As the check valve cannot be fixed quickly, in this case the compressor should be tripped and standby train should be used.
3) Tran discharge shutdown valve (SDV) fail close- if the discharge SDV is shut closed again the compressor should be tripped as the SDV should be repaired.

So in my case, I am thinking that the recycle line is not necessary and it just make the system more complicated.

I appreciate if I can have your valuable experience in this matter.

RE: Minimum recycle line for reciprocating compresor

Since you already have a recycle valve on each stage, you can use any one of them to double up in this service. Suggest you use the one stage 1. Setup a PIC on stage 3D and send its output to a high or low signal autoselect which also gets the signal from stage 1S low suction PC. The selector will pick the appropriate signal to feed the stage 1 recycle CV. If you are not sure how to do this, ask your plant process controls engineer to help set this up.
Capacity of this control valve would be full flow seen at max normal stage 1S pressure and max normal stage 1D pressure ( coincident with high pressure on stage 3D). But check to see if:
1)The recycle flow stream temp is not higher than the normal stage 1S temp.
2)Specify a low noise valve for this recycle service if noise is estimated to be high.
The basic idea here is to recycle gas around stage 1, and thereby reduce net forward flow of the compressor in an attempt to reduce the final discharge pressure on stage 3.

RE: Minimum recycle line for reciprocating compresor

Hi georgeverghese;

Thank you so much for your kind reply. So you also believe that an additional recycle line is not necessary.

RE: Minimum recycle line for reciprocating compresor

Yes, not required. The new PIC on stage 3D should be a high setpoint controller ie. it only acts to open the stage 1 recyle valve when stage 3D pressure is high and approaching high high trip pressure.

RE: Minimum recycle line for reciprocating compresor

thanks georgeverghese

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


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