×
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

Jobs

dished end thickness

dished end thickness

dished end thickness

(OP)
dear all,
can you tell me what is thickness tolerance for dished end (claded or plain)of pressure vessel.

thanks

PAUL A.

RE: dished end thickness

Ap734, best to ask the manufacturer. It can vary. Some will publish minimums.

IIRC for 2:1 heads a good rule of thumb is 1/16" for 1" and under, 1/8" up to about 2", and 1/4" over that. Use at your own risk :)

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: dished end thickness

Don't confuse tolerances with thinning allowances. But you might check Appendix 32.

RE: dished end thickness

Yes, I was speaking of forming allowance, separate from plate tolerance and other head dimensional tolerances.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: dished end thickness

(OP)
JStephen,
Appendix 32 of what code / specification / documents?

regards,
PAUL A.

PAUL A.

RE: dished end thickness

Just to clarify-
I'm not sure there IS a tolerance on thickness, actually.
By which, I mean that if you have a calculation showing minimum formed thickness of 0.8920" or whatever, are you allowed anything under that? And just glancing through, I didn't see a specific tolerance for underrun below that- maybe I'm overlooking it somewhere.
However, that Appendix 32 of Section VIII Div 1 of the ASME Boiler and Pressure Vessel Code relates to localized thin spots- so if you just have one little section of a head that underruns the thickness, you can evaluate it by this appendix.

On the forming allowance, heads are commonly referred to by the nominal thickness, which is the thickness of the flat plate they start with. But it's understood there will be some thinning in the process, so it's customary to specify a forming allowance or a minimum thickness after forming. So you might specify a 0.625" nominal head, and the formed thickness is actually 0.5625" minimum or something like that.

RE: dished end thickness

Take it from an old head maker. Make your life simple. Tell the head maker you minimum required thickness & let him figure out the nominal. If you are using clad materials let him know both the minimums, the clad requirement & the backer. If it is a welded head let him know if the clad is part of your design strength calculations or only for corrosion protection. With deepest apologies to the lady head makers.

RE: dished end thickness

Yes

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: dished end thickness

Actually, that makes your life simpler but complicates mine a little. Normally, there is some difference between the required thickness and the minimum thickness available, and that can be used in the reinforcement calculations to help eliminate repads. The thickness furnished also figures into some of the detailing, required weld sizes, impact test exemption, weights, etc.

RE: dished end thickness

Yet using a standard metal thickness (already available from stock or from a certified supplier) may save tens of thousands by NOT specifying an arbitrarily calculated but "precise" thickness.

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!


Resources