The Chatter 2021

Quality Matters – the Importance of Welding Programs

By Charles Hall

Cianbro, Starcon, and A/Z routinely perform welding during most construction projects. Welding, although a common industry practice, is a complex activity requiring careful attention to many details that must be performed by skilled, qualified professionals. Welding programs focus on two key elements – Weld Procedure Specifications (WPS) and qualified welders. Both elements of a welding program must be satisfied to properly produce sound welds.

Welding must be performed by qualified team members in accordance with a written WPS, following both project specifications and the applicable Welding Code. Depending on the project, Welding Codes may be in accordance with the American Society of Mechanical Engineers (ASME), the American Welding Society (AWS), the American Petroleum Institute (API), or other internationally recognized standards.

To establish a qualified WPS, welding codes usually require performance of weld procedure qualification weld(s), documented on a procedure qualification record (PQR). Once welded, test pieces are destructively tested to ensure the welding operation did not degrade the base metal. Common destructive tests performed on completed welds include:

• Bend tests to prove ductility.

• Tensile tests to prove material ultimate strength is acceptable.

• Some codes require additional nondestructive and destructive tests of welds during the qualification process, including:

• Radiographic test (RT)

• All weld metal tensile tests

• Notch toughness testing to prove material toughness at lower temperatures

• Corrosion tests

• Ferrite content tests

• Microstructure hardness tests

• Macro etch examination to prove complete weld penetration

• Nick break tests

The PQR documents all welding parameters used during the qualification weld(s) and the required testing results. Once the required tests are completed satisfactorily and documented on the PQR, the details recorded on the PQR may be used to write an approved WPS.

Vital details established and recorded on the PQR, transferred to the WPS, are essential variables. Essential variables may not be changed on a WPS without redoing the PQR (establishing revised essential variables). Some details recorded on the PQR are non-essential variables. Changes to non-essential variables on a WPS may be made without redoing the PQR. Examples: Specified welding process, base metal, or filler metal numbers are essential variables requiring a new PQR to revise an existing WPS (if changed). Methods used to clean the weld zone or nominally increase preheat from that specified on the WPS are non-essential variables that can be changed without redoing the PQR.

Once a qualified WPS is written, skilled welders must pass welder qualification tests following the WPS. After performance test welds are made, they are usually subject to visual examination and bend testing (some welding codes require additional inspections or testing). Results of a welder’s performance testing are documented on a Welder Qualification Record (WQR). The WQR lists performance essential variables, which differ from WPS essential variables. Once qualified, welders may weld using a qualified WPS within limits (performance essential variables) established by their qualification test. Performance essential variables include process used, base metals, filler metals, thickness of deposited weld, positions allowed to weld, performance of butt welds with or without backing, and a few others.

Cianbro, Starcon, and A/Z are capable of welding any base metal routinely encountered in construction. Welding processes include:

• Shielded metal arc welding (SMAW)

• Gas tungsten arc welding (GTAW)

• Flux-cored arc welding (FCAW)

• Gas metal arc welding (GMAW)

• Submerged arc welding (SAW)

• Other options, such as machine welding, orbital welding, pulsed arc, and high-frequency arc

Any Cianbro company may use the WPS and welders qualified by the other Cianbro companies. This practice must be described in each company’s QC Manual. Welding documents from one Cianbro company used by another, must be formally accepted by the second company (certification statement included on the applicable record).