ASME - Butt joint full penatration permissible gap?

[VinceFabspec]

Hi,
what is the maximum permissible gap in a buttweld for plates 1/4" thick without backing? Where can I find it in the ASME code?
Thanks,
Vincent

 

[metengr]

VinceFabspec;
What does your WPS state for an open root, butt weld root spacing tolerance? There are no maximum root spacing requirements for butt welds in the ASME B&PV Code, this is a process detail.

 

[littlechickend]

gap should be 2mm. but i can not find where it is mentioned in ASME code.

Maybe you refer to part UW or Sec. IX ASME Code, or AWS welding hand book.

 

[vesselfab]

that gap is set by welding process and your wps

 

[weldtek]

Vincent,
Metengr and vesselfab are correct. If you reference Sec IX you'll note for most of the common processes, root spacing is a non essential variable. This means that while it must be specified on the WPS, a change can be made without requalifying the procedure. Some common sense must be applied here. There are some processes such as laser beam welding where root spacing is an essential variable meaning that a change would require requalification of the procedure.