Half-Pipe Jacket

[torsani]

Hi
The ASME VIII-Div.1 code present, in appendix EE, tables for half-pipe's design limited in: 30<=D<=170 in., 3/16<=t<=2 in. and pipes with NPS = 2, 3 and 4.
Can I use appendix EE for design half-pipe jackets with others dimensions, out of limits above?
I no, how can I design others dimensions half-pipe jackets?

 

[prex]

If your work specification requires you to fulfill ASME VIII design criteria, then of course you can't go out of specified criteria (though EE is a non mandatory appendix...).
Otherwise it's up to you.
However I can't see how you could extend the tables in app.EE, as the rationale for their derivation is not given.
You should go on by analysis.
prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[MJCronin]

torsani,

The rules for half-pipe jackets were developed by Maan Jawad ( an author of books on process equipment design and a consultant to the Nooter corporation.

His ASME paper on this subject was incorporated into the ASME B&PV code as EE. (See the text: Guidebook for the design of ASME Section VIII Pressure Vessels; available thru ASME press)....

I suggest that you contact him (e-mail)or get a hold of his paper for the answer to your question

Good Luck

MJC

 

[welding1]

Make sure the shell under the coil is strong enough; I have seen half pipe coils become full pipe coils because this was overlooked!

Treat the area under the coil as a short vessel under external pressure or consider it to be a rectangular flat plate of infinite length.

The other problem is the coil to shell weld. If the coil is hot and the vessel cold the thermal stress in this weld will be high, particularly if its stainless steel. Ideally the weld should have two layers, as single run can leak. Avoid using fillet welds.

http://www.gowelding.com

 

[Seldom]

Welding1 has give some of the best, yet most overlooked advice I've seen pertaining to fabricating and welding half-pipe jacket as he states &quot;Ideally the weld should have two layers, as a single run(one) can leak. Avoid using fillets.&quot;

It's been my experience, that little bit of advice if followed, would save some companies from alot of unscheduled process shutdowns and subsequential costly field repairs.

 

[MJCronin]

To all above,

The question of weld quality in the fillet (?) weld connecting a half pipe to a reactor is one that the industry struggles with.

The configuration of the weld is such that the &quot;heel&quot; of the fillet is placed in bending as the half pipe jacket increases in pressure or in temperature. Performing a full-penetration weld on the half pipe is both very difficult and expensive.

More than one vessel fabricator will offer different weld qualities (via different weld techniques) for vessels fabricated with these types of jackets. Two that come to mind are Nooter Corp (St. Louis) and Central Fabricators (N.J ? i think) These two firms have and will construct vessels with different types of weld qualities. Nooter, I believe, calls the two proceedures...&quot;fillet welded&quot; and &quot;nearly full penetration welded&quot; ( my memory may be a little weak here...)

The idea here is that, if the service demands many deep temperature and/or pressure cycles, the premium weld may be required. If there are modest temperature/pressure cycles or if the vessel is to have a limited number of cycles, then the fillet welds may be adequate...

Some fabricators will internally inspect the welds within the half-pipe chamber via a flexible borescope and certify the inspection. I have seen some of the recorded videos...

Some process and pharmacuetical companies have chosen to develop &quot;in house&quot; perfomance standards for these welds. The fabricator must develop a &quot;test plate&quot; using the proposed weld proceedure and hydrostatically test to destruction

I would like others to comment on this issue and share any knowledge ( or websites) that may be useful....

MJC