Question: When nozzle or branch connections are attached to the wall or head of a pressure vessel, what are the basic criteria establishing procedure and performance qualification requirements, assuming impact testing is not a requirement?
Reply: Where the nozzle is attached to the vessel by welding completely through the thickness of the vessel wall, the procedure shall be qualified for the thickness of the vessel wall penetrated by the nozzle or attachment. Where additional metal is placed on either the interior or exterior of the vessel wall in the form of fillet welds, they shall be considered as having been qualified by the procedure qualification covering the thickness of the vessel wall. Performance qualification for this weldment may be made in plate to cover the appropriate thickness of the vessel wall and the position in which the weld is being made. Diameter is not a factor. Where the nozzle or attachment is welded to the vessel wall by welding through the thickness of the nozzle or attachment, the procedure qualification shall be made for the thickness of the nozzle or attachment wall at the time of welding. Performance qualification for this condition shall be made with the appropriate diameter pipe weld as required by QW-452.3 with the range of thickness of weld metal qualified determined by the thickness of the nozzle or attachment wall at the time of welding. Any fillet welds, both procedure and performance, will have been qualified when qualifying for the full penetration welds involved.
ATTENTION
The foregoing Interpretation has been further considered, and the following corrected Interpretation sent to the inquirer.
Correction Issued: March 12, 1981
Question: When nozzle or branch connections are attached to the wall or head of a pressure vessel, what are the basic criteria establishing procedure and performance qualification?
Reply: For groove weld procedure qualification, the base metal thickness range for all base metals being joined in addition to the deposited weld metal thickness range for each process used must be qualified in accordance with QW-451 (see QW-202.4). Also, see exemptions in QW-202 for fillet weld procedure qualifications. For groove weld performance qualification, the deposited weld metal thickness range must be qualified per QW-452, and where the nozzle or attachment is welded to the vessel wall by welding through the thickness of the nozzle or attachment, a "set-on connection" performance qualification shall be made with the appropriate diameter pipe as required by QW-452.3. Where the nozzle or attachment is welded to the vessel wall with the weld preparation made on the vessel wall, a "set-in" connection, diameter is not a factor. See QW-303 for exemptions for fillet welds.