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

Tray support rings as external pressure stiffening rings

Tray support rings as external pressure stiffening rings

Tray support rings as external pressure stiffening rings

Does anyone have any useful tips on how to rerate a trayed tower originally designed at 0 psi external to full vacuum by taking advantage of the tray support rings?
My initial analysis shows the moment of inertia does not quite meet UG-29(a), but I think I'm ok for full vacuum based on the rules of UG-29(c)(1) thru (4).  
Another option I haven't yet pursued is Code Case 2286; anyone with experience using this for rerating without adding additional hardware to a tower to obtain full vacuum?

RE: Tray support rings as external pressure stiffening rings

Even though the Code allows it, be very careful taking credit for internal tray rings as vacuum stiffening rings.  There are several potential problems with this idea.  

You have to meet both UG-29(a) AND UG-29(c) to comply with the code rules for external pressure.  

With internal rings, you will have corrosion acting on 3 surfaces of the ring.  You must subtract the corrosion allowance off of both the upper and lower surfaces, making the ring thinner, and add the corrosion allowance to the inside diameter, making the ring shorter.  Once you do this, you will always have to be inspecting and measuring the rings on subsequent internal inspections to make sure you haven't corroded below the required ring dimensions.  Significant repairs may be required if corrosion exists.  

Code cases are generally used for new vessel fabrication.  As for applying a Code case to a vessel rerate, your local jurisdiction may need to be involved, depending on your local boiler and pressure vessel laws.  In California, Code cases are only allowed on new fabrication and the vessel fabricator must apply to the State for approval to use the desired Code case.  

If your vessel rerate for full vacuum has to be approved by your local jurisdiction, you will probably be better off by attaching external vaccuum rings of the proper dimensions.  

Good luck.  

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


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