(Temporary) Stiffener Sizing for Boiler / Tower cut out.

[ER_Azza]

Hi All

I just can't remember the standard for this. Done once before but now can't remember the info in ASME Sec VIII, I think.

I need to do a temporary cut out at the (acid) tower for access during shutdown.
Possibly size of about 1500 x 1000mm.
I just need to size the temporary stiffener for this (horizontal and vertical).
I have done twice in the past, many years back and I remember ASME had drawings. For the life of me, I just could not find it now.

Any help appreciated.

 

[JStephen]

I'm not familiar with the item you're referring to.
However, Section VIII is a construction code, for new construction, and wouldn't address repair procedures.
There is a National Board Inspection Code and API 579. I don't know that either addresses the topic, but more likely than Section VIII.

In this thread, scroll down to LittleInch's post, there is a link to a pdf with some presentation notes on the topic as applied to large storage tanks:

https://www.eng-tips.com/viewthread.cfm?qid=513344

Note that with these tanks, the plate may be elastically bent into a curved shape during erection, so when a section is cut out, it may be flat, and allow the adjacent edges to flatten out. I would assume not so much an issue on vessel work.

 

[r6155]

See ASME PCC-2.

Regards

 

[Christine74]

I don't think ASME provides any guidance for this type of repair, but I think you should be okay so long as the Section Modulus of the tower with the window cutout and the stiffeners is no less than the original Section Modulus, so that's one way. Of course you would also need to evaluate the stiffener attachment welds.


-Christine

 

[dig1]

ER Azza,

You may want to look at Tubular Steel Structures Theory and Design by Troitsky; there are sections on on the analysis of breech openings including the stiffener design; it may not be 100% applicable to your situation but you should be able to adapt the methodology. Typically when we do these designs we include the construction wind provisions (if it is outside and has any level of height) from ASCE 37 (this standard may not be applicable in your area) which has a reduced wind pressure based on duration of the work being performed.

 

[r6155]

More data: diameter, height, shell thickness, material .....?

Regards

 

[RJW000]

Make sure you put the stiffeners on before you cut the window