Difference between SA 387 F11 CL1 And SA 387 F11 Cl2 Material

[Ronak_Patel]

I`m Working on HE design where there is steam service at Design Temp of 475C and Operating Temp of 250C at 48KG/CM2 Design Pressure.

Material specified by Process team is 1.25 CR + 0.5 MO . I have Two options for plate material
1) SA 387 F11 CL1 :- Creep Temp = 480C , as material will be within creep range i can perform elastic platic calculation in UHX and get smaller thickness
2) SA 387 F11 CL2 :- Creep Temp = 455C ,as material will be in creep range , i cant perform elastic plastic calculation in UHX and getting higher thickness.

So my first choice was to go with SA 387 F11 CL1 but my seniors here are apprehensive of CL1 and instructing me to use CL2 strictly saying there is some problems of PWHT with CL1 Material.However i could not find much of difference between two class from ASME codes and API 934.
Kindly help me with knowing if there is any fabrication or NDE complexities with Cl1 material and where i could read more about different classes.

Thank you

 

[Guest102023]

ASTM can be very vague about the meanings of ‘class’ for low alloy steels. Usually it refers to heat treatment methods that are recognized across the industry. Given the higher specified mechanicals I’m guessing this is Q&T.

I’m not sure about PWHT problems with class 1; I’ve done it and it’s perfectly allowable in ASME construction codes. I suspect they are basing it on a well reported past failure that they want to apply to this steel for all time. I see non-metallurgists do this a lot.

After all that, a reputable supplier like Arcelor Mittal would be your best bet.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[Guest102023]

Ah, this should explain it. It’s about the minimum tempering temperature, which you can’t exceed for some classes. Your bosses may actually be on to something!

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[Ronak_Patel]

@brimstoner
Thank you for your response.

can you please elaborate on min tempering temp ?
do you mean class 1 can not be tempered at 1150 F ?