-40f procedures

[Skeeterbob]

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?

[sn0border88]

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?

[Fegenbush]

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.

[Donald Branscom]

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 32ºF

Anyway like Fegenbush said, check those ASME codes.

[Fegenbush]

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.

[dave powelson]

In addition to all of the above suggestions, you should request in writing
from 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!

[davinwheel]

Originally Posted by Fegenbush

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.

Section VIII applies to pressure vessels not the piping. So PWHT may not apply. To find that spec refer to ASME B31 codes for piping.
ER70 and 7018LH along with other filler metals and processes, can be used with a supporting WPS and WPQR's that have passed low temp. impact tests.