-40f procedures

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I will be making several pipe welds on a co2 refridgeration unit. process co2 will be at -40f conditions when unit is running. all pipe is A106. weld connections to be made are flange connections to exsisting pipe stubs, so will likely all be multiple fillet passes. My question is, becuase of the extreme low temperature is there a required alloy of rod that should be used other than standard er7056 tig rod?
Reply:Sounds like you need to consult a weld engineer.  Do you really want to be held liable when the weld fails because you referenced your weld procedure from an unknown source on the internet?Have we all gone mad?
Reply:Per ASME Section VIII Division 1 UCS-65, you will need to post weld heat treat the welds.  Standard ER70 rod can be used, but your procedure will need to be approved for PWHT usage.  This normally involves a charpy impact test to determine the brittleness of the material at the desired temperature.
Reply:I do not know anything about pipe but can you get the temperature up to at least 32ºF to weld?Structural welding requires metal to be above 32ºFAnyway like Fegenbush said, check those ASME codes.AWS certified welding inspectorAWS certified welder
Reply:Donald,It was my understanding that the service of the pipe will be at -40°F, not the conditions at which it will be welded.However, you are correct, it is necessary to be above 32°F to make D1.1 welds.
Reply:In addition to all of the above suggestions, you should request in writingfrom the customer 'What?' WPS, etc.--they require--even if they have none and no clue. Whatever WPS, etc. you arrive at--they need to sign off on this.....if it ain't in writing-it ain't--so!Blackbird
Reply:Originally Posted by FegenbushPer ASME Section VIII Division 1 UCS-65, you will need to post weld heat treat the welds.  Standard ER70 rod can be used, but your procedure will need to be approved for PWHT usage.  This normally involves a charpy impact test to determine the brittleness of the material at the desired temperature.