SPLIT-TEE LONGITUDINAL WELDING

By wjsantamaria Date 11-27-2001 16:22

WE HAVE A PROJECT, WHERE WE HAVE TO DO A LONGITUDINAL SEAM WELDS IN A SPLIT-TEE, SO THE SITUATION IS IF THE PARAGRAPHA B.4.1.2 (API 1104-99) APPLIES IN ORDER TO DO LONGITUDINAL SEAM WELD IN THE SPLIT-TEE, BESIDES WE WANT TO KNOW IF WE CAN WELD THIS LONGITUDINAL JOINT WITH OR WITHOUT BACK-UP STRIP AND IF IS NECESSARY TO REMOVE THIS BACK-UP STRIP.

WE APPRECIATE YOUR HELP, THANKS

By NDTIII

Date 11-28-2001 10:45

Paragraph B4.1.2 applies to inservice welding. It states these joints "should" be fitted with a mild steel back-up strip or suitable tape to prevent penetration of the weld into the carrier pipe.
The intent of this, I believe is stated in the Note following the paragraph. Penetration of the weld into the carrier pipe is undesirable since any crack that might develop will be exposed to hoop stress in the carrier pipe. That could cause it to propogate.
As for the back up strip, I don't know how you would remove the it after welding, but I think it should be used.