SA-193 Gr.B6 in sour service NACE MR0175

[mitulmech]

Dear Group Members,

I am working on Heat Exchanger which is an electric heater.

Design details are as below.
Material of shell side is 13%Cr. SA - 336 Gr.F6
Service is high pressure CO2 Service
Design Pressure = 320 Barg
Design Temp = 85 / -20 °C

Equipment is under sour service and NACE MR0175 is applicable.

Can we use SA-193 Gr.B6 for the flange bolting?

I could not find any restriction for martensitic or any other stainless steel grade bolting in MR0175. Like it have recommendation of using B7M and L7M for exposed bolting.

Please advise is this material is permitted or not as per NACE MR0175.
If not what alternative material we can use.

 

[gr2vessels]

How much of sour service you have on outside the exchanger? If not, then use ASME SA-193 B7 for external bolting.