×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

Pipe Length Affecting Design Thickness3

Pipe Length Affecting Design Thickness

(OP)
Hi all,

I am looking into designing a stabilizer tower for a process application using ASME VIII Div 1 (first time doing so) and have a curiosity question regarding the correlation between design thickness for a shell and the length of said shell.

Some info:
Design pressure is 200PSI@400F, 24" OD, Sa-333-gr6, .118" CA, 50' tall, Full radiography, tower is split into a top and bottom section at 120" from bottom.

My concern is when I run the bottom shell (~120") versus the top shell (~480") the design thickness for the shells differ (.2755" versus .3322") and the only thing I can accredit this to is the length of the top shell.

So i'm assuming that Compress is taking into account the length of the top shell, but if I were to do this calculation by hand I would end up with a min. thickness much less than what Compress is requiring.

I guess my ultimate question is at what point does Compress start to increase the required thickness of the shell?
Is there somewhere in code that requires the length of the shell at some point to be taken into consideration?
Am I potentially just missing something in general?

Any feedback is welcome.
Thank you!

RE: Pipe Length Affecting Design Thickness

Couple of things it can be:
- Length of the shell is a factor in external pressure calculations. SO if you have full vacuum, it would affect the thickness.
- Also, if you set the liquid level of the vessel to be the top of the tower, the corresponding weight would translate to a pressure that is highest at the bottom. This extra pressure would require a thicker shell.

RE: Pipe Length Affecting Design Thickness

I just opened compress and ran this case with the information you provided. It is most definitely the external pressure because I also came up with exactly 0.3322" as well. If you want reduce the thickness so that you can use Std-Wt pipe, try using a vacuum ring (stiffener ring) or two to get the thickness down.

RE: Pipe Length Affecting Design Thickness

(OP)
Afox88, you are correct it is most definitely the external pressure. Thanks for the quick reply i knew i was overlooking something very simple. Again much appreciated!

RE: Pipe Length Affecting Design Thickness

2
With the "Cylinder Dimensions" dialog open, you may consider enabling the "Details >>" tab at the bottom. This will reveal thickness requirements due to internal "t(int)" or external "t(ext)" pressure.

RE: Pipe Length Affecting Design Thickness

(OP)
DandB, as always the Details tab is very useful, and 90% of the time I do run everything with it open. The issue for me is I overlooked this as I usually don't end up designing towers, mostly just scrubbers and suction discharge bottles. But you are correct, the "t(ext)" is very clearly shown as the contributing factor to my issue here.
Thanks for the input!

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.

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
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!