Difference between ASTM SA182 cl 3 and cl2

[kevlar49]

Hi,

We are ordering a new heat exchanger with ASTM SA182 F11 cl 3 pressure-retaining components. A question came back if there is any problem with designing as if it were ASTM SA182 F11 cl 2 since code allowables are only availble for that. cl 3 is a stronger, but has same chemistry as cl2. I could not find any difference in quality control for the two classes. Is there one? It just sounds like that if design were based on cl2 then we just wouldn't be optimizing on cost, but from a metallurgical standpoint they are equivalent. Any comments?

 

[metengr]

kevlar49;
To achieve the Class 3 designation, the heat treatment requirements would probably be altered to more of a liquid quench versus Class 2 requirements for air cooling. By the way, Section II, Part D does have allowable stress values for SA-336 F11, Class 3 material (same chemical composition and mechanical property requirements as F11, K11572, under SA-182), which could probably be certified to SA-182 as a forging. I agree with you to go with Class 2 if you specified SA 182.