Code Insight: Qualifying Tube-to-Tubesheet Weld Procedures Per ASME Section IX

In recent code editions of ASME Section VIII, Division 1, clarifications regarding Tube-to-tubesheet welding have been included. In the UW-28(b) paragraph, which is new to the 2021 code edition, the code user is directed to qualify Tube-to-tubesheet welds by either following paragraph QW-193 or QW-200 in ASME Section IX.

What Does Section IX Provide Guidance On?

Section IX has options for both procedure and performance qualification based on mockups or based on groove weld or fillet weld qualifications.

If the applicable code of construction (in this case Section VIII, Division 1) requires the mockup rules, then QW-193 applies. If the applicable code does not, then the mockup per QW-193 is still an option but groove weld requirements or fillet weld requirements may be used instead.

Procedure Qualification

The Tube-to-tubesheet welding procedures under UW-28(b) must be qualified according to Section IX QW-193 or QW-200, with the option to use mockups (or not).

Guidance in Section IX QW 202.6 clarifies that if mockup qualification is required by the code of construction, QW-193.1 must be followed. However, in Section VIII, QW-193 is listed as an option, allowing for flexibility. QW 202.6 permits the use of mockups per QW-193, meeting groove weld requirements of QW-202.2 and 202.4, or meeting fillet weld requirements of QW-202.2(c), but only for non-pressure retaining welds.

Essential variables for Tube-to-tubesheet welding per QW-288 are additional to those specified in Tables QW-252 through QW-267, depending on the process used. For instance, if GTAW is used, variables from both Table QW-256 and QW-288.1 apply. It's noted that Table QW-288.1 applies to processes other than explosion welding, while Table QW-288.2 applies only to explosion welding.

The language in QW-288 makes it sound like the paragraph only applies if QW-193 is used, which may be clarified in a future version of the code. But consider this: using the additional variables in QW-288, anything would be conservative by adding further limits on the qualification. Also, the language surrounding the performance qualification per QW-387 suggests the additional essential variables are unaffected by the application of QW-193 or not.

Performance Qualification

UW-28 speaks to procedure qualification, while UW-29 in Section VIII, Division 1 addresses performance qualification. Currently, UW-29 lacks explicit requirements for Tube-to-tubesheet performance qualification, deferring to Section IX QW-387. Performance qualifications mirror procedure qualifications closely:

• If the applicable code of construction (in this case Section VIII, Division 1) mandates mockup rules, QW-193 applies. Even without such a requirement, QW-193 remains an option. Alternatively, groove weld or fillet weld requirements may suffice (the fillet option was introduced in the 2021 edition of Section IX).
• Table QW-388's essential variables complement those for Welder Performance Qualification (Tables WQ-352 through QW-357) and Welding Operator Performance Qualification (QW-360).

Streamlined Qualifications with Weld Procedure Technology

In the same manner that Section VIII, Division 1 UW-28(b) makes QW-193 mockup rules optional, so does weld procedure software like CEI’s ProWrite.

Here’s how it works:

• The welding engineer, Certified Welding Inspector (CWI), or fabricator using ProWrite may qualify the procedures based on QW-193 or not as described above. The same applies to qualifying welders and operators.
• The procedures based on the Tube-to-tubesheet PQRs take into consideration the additional variables per QW-288 to help guide the user on the allowable ranges that do not require requalification.
• Likewise, welders and operators can be easily matched with the procedures based on their performance history, considering the additional variables in QW-387.

To see a quick demo of this in action, visit https://info.thinkcei.com/qualify-tube-to-tubesheet-weld-procedures.