welding procedure for -40f process pipe

[Rsams]

I need to make several connections to existing(new)pipe stubs on a Co2 refrigeration skid. welds will be multiple pass fillet socket weld. pipe to flange. All pipe is carbon A106 and flanges are the same. Class #300. Process C02 is at -35f during operation. My question is are there any welding procedures that need to be adhered to because of the low Temperature? Is there a certain alloy tig rod needed? any pre or post heating needed? etc.

Thanks in advance.

 

[ColonelSanders83]

What piping code is applicable to this system? The details you need will depend on the code.

Your welds will need to be qualified with impact testing performed on your joints due to the low temperature. Additionally all your installed A106 will need to undergoe impact testing. For this reason you are genarlly better off to use A333. Of course these requirments assume you are not making use of one of the code exemptions allowing colder service temperatures based on lower sustained stresses within the system. It all comes back to what code?

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/

 

[Rsams]

Co2 skid and our Ammonia skid that we are piping together(exchangers)were both fabricated to ASME B31.5.

 

[ColonelSanders83]

I reccomend reading B31.5 Para 523.2.2 and determining which if any of the exemptions governs your case. The exemption applied will be specific to your systems and thier design conditions. If noe of the exemptions apply you will need to impact test.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/

 

[DVWE]

Rsams,

Is the entire weld joint going to be done with TIG? Any other processes used, such as SMAW?

 

[Guest102023]

Once you sort out the requirements in B31.5 and choose the material (SA-333 is recommended), then you will need a qualified welding procedure that has impact testing to your minimum design temperature or lower. I don't know if hardness testing is required for your spec'n or in B31.5, but it is useful and inexpensive to add it (Vickers method recommended). If you don't need the hardness now you will in future.

If you don't have a WPS for -35°F, I recommend ER80S-D2 filler for TIG and E7018-1 for SMAW. These are both good down to ~-50°F. Preheat and follow good low moisture (i.e., low hydrogen) practice.

Using TIG for the entire joint may cause excessive distortion, especially on higher thicknesses (you have not told us T). PWHT is probably not required by Code for thinner materials (I am sticking my neck out here on B31.5, which I am not intimately familiar with). PWHT is probably not necessary to make your properties. Again, check your spec or company fabrication standards.