A-36 Cold Weather 1

[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!

 

[weldstan]

Many stacks have been manufactured from A-36 where the low ambient temperature renders the material brittle because applied stress is low relative to yield strength. It would appear that wind loading would be your primary concern when temperatures are low and the stack is not operating with exhaust flow. I leave you to your calculations to determine need for impact tested ;ow temperature steel and A-36 can be so purchased.

If a crane, other equipment or other object strikes the stack and causes brittle failure, the initiator of the strike would normally be liable. If wind loadings results in failure, the designer, manufacturer and erector would have potential liability.

 

[IFRs]

Brittle fracture can be a serious concern. It is related to thickness. For example, API 650 would not use A36 at any thickness below -12C or -28C if the material has certain chemical limits. And these teperature limits rise with thickness.
But, then again, API 650 tanks hold volatile liquids and a failure is a serious public issue. What stnadards or codes apply to your structure?

 

[nich0142]

Thanks for the replies.

ASME STS 1 Steel Stacks is what governs stack designs and they don’t address cold weather material selection or what temperature charpy testing is recommended.

 

IMO due to its poor properties (strength as well as impact properties) A36 should not even be produced in plate form. Its use should be restricted to non-critical items such as internals. In any case A516-70 is not more expensive but is superior in every way.

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