A-36 Cold Weather 2

[nich0142]

Don't know if this should be in the Structural Engineer or Materials section.

The project is a self supporting stack that would be behind a natural gas fired boiler.

We always use A-36 material but are aware of brittleness at low temperatures.

Is there a general "rule" when to switch to a cold weather steel? 516 Grade 70N / A572 / CSA 350WT

Our application is at -46C but the question always comes up at what temp should we consider using a different material rather than A-36.

Our customer specifies A-36 as the material but as the supplier of the stack we feel that we have an obligation to inform them of the issues of A-36.

If there is a brittle failure who is at fault us as the designer / supplier or the customer for failing to protect the stack from brittle impacts?


Appreciate your thoughts!

 

[dik]

"Lastly, your customer friend is liable,"

I wouldn't hang my hat on that... if an issue, then best he seek legal counsel.

Dik

 

[r13]

dik,

I wouldn't hang my hat on that...

Why would't you?

 

[dhengr]

Nich0142:
I’d report your findings back to your customer, and on to others in the chain, in the form of a simple report for the file, explaining the pros and cons of the original spec. vs. your findings. After all, you didn’t write the original spec., but have a legitimate question about it given the operating temps. And, make a recommendation of a better and preferred material, and ask for an extra for any extra material costs, fab. costs, etc. Alternatively, they should send you a letter telling you what material to use, and absolving you of any responsibility for the material selection. That way, you have made a good faith effort to inform them that the A36 may not be the best choice.

But still, quality design, details and welding will be just as important in this type of application as the material selection, despite the new material being a bit tougher. Poor detail or workmanship will outweigh the tougher material in a heartbeat. Almost all of the problems I’ve seen of this nature have had as much to do with poor design, details and workmanship as to the exact material selected. There will be plenty of blame to go around, if anything happens, and you’ll end up defending yourself, even if not found at fault in the end. So, don’t let your workmanship in any area be the first thing you have to defend.

 

[r13]

Wish I got the relationship straight at the first reading.

Customer 1 (end product user) - a Canadian petrochemical company, purchaser to customer 2.
Customer 2 (end product builder/designer) - a boiler manufacture, supplier to customer 1, and purchaser to the steel supplier.
Supplier - nich0142, supplies A36 steel to customer 2.

 

[nich0142]

Correct - with a small adjustment. Supplier (me) is "Stack Engineering / Manufacturing / Fabricating". i.e we are not just a steel supplier. Customer 2 will purchase an Engineered Stack from me and we will deliver it to Customer 1 / 2 at the job site.

 

[r13]

nich0142,

Ooooh, I don't know how others have figured. It turns out you are the prime "liable person" as many have suspected.
Anyway, hope you have gathered enough information here, and good luck.

 

[dik]

" Supplier (me) is "Stack Engineering / Manufacturing / Fabricating". i.e we are not just a steel supplier."

and experts to boot... dhengr's summary is great.

Dik

 

[Geoff13]

A slightly off topic "heads up" comment. My whole career is designing/building tanks and vessel for all the petrochemical companies in Canada, and particulary Alberta. Most customer specs I've seen ask for an Alberta P.Eng. stamp on anything "engineered". Not sure if this will apply to your engineering, but I see you're from Texas so it could be an issue.

 

[r13]

nich0142,

Just my (last) 2 cents:

Usually, an industry company's RFQ shall include a document called "specs", which was prepared by its in-house technical staffs, or hired gun - professional constants. If this is the case, and you have doubt on the suitability of the specified material, then you can raise the question with a RFC (request for clarification), which states your understanding (with source document cited), and offer alternatives for consideration. This RFC shall be sent to your friend/customer, then forward to the end purchaser - the petrochemical company. Then, you have done your job, until a response is received.

Otherwise, dheng's suggestion is the way to go.

 

[oldrunner]

An informative article in Modern Steel Construction: "Are You Sure That's Fracture Critical."

https://www.aisc.org/modernsteel/archives/2015/january-2015/.

Also there is a chapter in the New York State Steel Construction Manual (3rd Edition) - Section 9 - Fracture Control Plan.


Also look at US Federal Highway Administration Bridge Technology - High Performance Steel Designer's Guide. Table 2.3.1 - Temperature Zones for CVN Requirements specifies Temperature Zone 3 for below -30 degrees F to -60 degrees F. A number of northern states require the steel temperatures down to -40 degrees criteria.

Some years ago I did specify some requirements for -40 degrees F project, but used a welding consultant for recommending the welding and steel requirements.