What design conditions are required to calculate Tmin for steel stack in service for 40 years?

[sxz]

Hi, Steel Chimney Experts,
I like to know what conditions should be considered to calculate the minimum required wall thickness (Tmin).
1) Original wind code
2) Original nominal wall thickness, instead of actual wall thickness measured.
3) Original allowable tensile stress
4) Original allowable compressive stress

Thanks in advance for any advice.

SXZ

 

[saplanti]

There is no short cut in this kind of applications. There are a lot of factors that you cannot imagine. The best, you should call an expert to look after your job. Trust me you cannot replace the site investigation through an expert eye with simple forum search. Additionally, you need to prepare all the documentation and drawings for the expert. If you can, ask the original designer to provide the calculation for you.

 

[MJCronin]

sxz...

Do you have any experience at all with industrial stacks and chimneys ?..... oh, you are a recent University graduate,... I now understand

STEP ONE----- Get a cost estimate for a new replacement stack - you have gotten 40 years out of this one, it is at the end of it's life. There are many contractors available who will provide accurate cost estimates

STEP TWO ----- Get an estimate of the cost to determine a wall thickness survey on the old stack. Throw in the cost of a new external coating system because your MBA boss will want new paint while there is scaffolding in place. New paint will make him look good while you, of course absorb all responsibility for structural integrity.

STEP THREE ----- Get an estimate on the business cost if the old stack were to collapse. Will business production shut down ? .... Will people die ?.... Make an estimate

Now with the costs associated with STEPS One Two and Three, make an evaluation of whether a new stack is the best choice to replace your 40 year old grandfather.

Please post pictures of your old stack and the anchorage at the bottom. Tell us of the materials of construction

MJCronin
Sr. Process Engineer

 

You are basically asking

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design the entire equipment.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[sxz]

Thanks for your time for response.
I applied Compress to check it with original nominal thickness, Tmin is less than the measured wall thickness, it passed.
If input of measured wall thickness, a thicker Tmin is more than the measured wall thickness, it failed.
This is different from the evaluation on the old pressure vessel, which has NBIC and rules from local authority. For steel stack, is there any rules to evaluate the stack's Tmin in service.

 

[saplanti]

In case a simple calculation gives you failure you have problem. If you want to make sure you need to run a proper finite element analysis by providing all the measured thicknesses.

You do not give us drawings to see some details, perhaps we could contribute better by seeing it. Sometimes they do not have strikes on them and cross-wind response may be more critical. I still suggest you employ an expert to go through entirely. The corrosion is another issue. I believe from top to the bottom cone outside corroded if it continuously run all these years. If the stack have internal protective layer or if it has secondary stainless skin you may not have internal corrosion. Otherwise you may need to think about the future corrosion as well.

 

[MJCronin]

I Believe that this s what you are looking for .....

https://www.asme.org/codes-standards/find-codes-standards/sts-1-steel-stacks

MJCronin
Sr. Process Engineer