Welding Failures I Have Known, Interesting cautionary tales from Metals & Welding  expert, Dr Jesse A Grantham, PE

Expert Insights - Robot Welds

Robot Welding Steel PlateThe Problem:

WJMG conducted zero guided bends or tensile tests for robot welds in the past 20 years.  WJMG conducted thousands of guided bends and tensile tests for manual, semi-automatic and automatic code-related welds. The welding procedures and welder tests specified in ASME and AWS codes are not being applied to robot welds.  In forensic assessments of robot welds, manufacturing deficiencies were found in welding procedures, operator qualifications and inspections.  Manufacturers ignore code requirements for time-proven procedures, qualifications and inspections for weld soundness and compliant robot welds.

My Assessment: 

The ASME & AWS codes require mechanical tests for qualification of pipe welding and structural welding.  When these codes are stipulated in contract documents, conformance with all provisions of these codes is required, except for those provisions that the Engineer or Contract Documents modify or exempt.  Code welding rules apply to WPSs, PQRs, welder performance (WPQs), and inspection for all welding processes permitted in the codes.  Industry does not enforce these rules for robot code welding.

The Consequences: 

The purpose of a WPS is to determine that the weldment is capable of providing the required properties for the intended application.  The PQR documents what occurred when welding a standardized test coupon and the results of mechanical testing.  The PQR records the essential variables for the test weld.  The WPQ confirms the welder’s performance and the person’s ability to operate the equipment and deposit sound weld metal.  These code-proven, time-tested techniques allow production processes to have a good chance of consistently achieving the minimum design criteria on every part.

The Lessons Learned: 

Robot welds may visually appear sound, when actually there are inherent flaws and non-fusion that preclude the weldment from achieving the designer’s intent.  During forensic assessments of weld failures, data in the WPS, PQR, WPQ and Inspection are guides for the investigator to confirm the likelihood of weld soundness.  Robot welds that do not attempt to comply with the engineering specified welding codes are considered as gross negligence in a failure incident.

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Welding Failures I Have Known, Interesting cautionary tales from Metals & Welding  expert, Dr Jesse A Grantham, PE