Low temperature material 1

[SWMechanical]

We need to install a choke valve in line. It is estimated that the temperature after the choke valve is -80C. The piping material is 2" XXS, SA333 Gr6. Considering the pressure of 5000KPa after choke valve and applying Firgure USC66.1 from ASME SEC VIII. The temperature reduction is 80C. So it seems we can use this pipe at -80C. But I think carbon steel will be brittle at low temperature.

Can anybody tell me if SA333 can be used in this case?

Thanks,

 

[metengr]

Please review ASME SA 336, specifically, Table 5. This table contains minimum impact temperature testing requirements, and Grade 6 is not sufficient at -80 deg C. You need a low alloy steel containing nickel, like Grade 3 or low carbon, fine grained like Grade 4 with microalloy additions.

 

[metengr]

The specification is SA 333, not SA 336.

 

[SWMechanical]

I have checked ASME SA333. The impact testing temperature is -45C for Gr6. But can I use Figure USC66.1 from ASME SEC VIII to this material for temperature reduction?

 

[metengr]

SWMechanical;
All Figure UCS66.1 provides are requirements for impact testing and exemptions for testing based on material thickness and service temeprature, it does not provide guidance on material selection. This material should not be used at -80 deg C, you will not have adequate notch toughness.

 

[SWMechanical]

Thanks metengr.

 

[SJones]

You should be looking at ASME B31.3 Chapter IX which doesn't give you the luxury of using ASME VIII UCS-66.1 anyway.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04