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Inspection and Testing for Welding Procedure Qualification

*Welding Procedures are the guidelines used to perform a weld.They are designed to provide a record of thewelding variables used and the inspection results obtained during the procedure qualification test. They canalso provide the instructions for the welder to use in production in order to produce acceptable welds. Usuallywelding procedures are developed in accordance with a welding code or standard, and with few exceptions*,require that physical weld samples be produced, inspected, and tested to establish qualification.

Welding procedures are usually divided into two categories,

1) Procedure Qualification Record (PQR)2) Welding Procedure Specification (WPS).

Procedure Qualification Records are the documented values used during the actual welding test and all theinspection and test results obtained from the actual test samples.

Welding Procedure Specifications are usually documented work instructions that can be used by the welderto conduct welding operations, and are based on, but not necessarily the same as, the parameters used for theProcedure Qualification Record.

We will consider the Procedure Qualification Record and the inspection and testing performed during itsqualification.

Qualification testing of a welding procedure normally requires documentation to show all the variables used

during the welding test and the documented inspection and test results. The variables required to bedocumented are typically such items as: welding process used, size, type and classification of filler alloy, typeand thickness of base material welded, type and polarity of welding current, amps and volts recorded, travelspeed during welding, welding position, type and dimensions of joint design, preheating temperature, interpasstemperature, post weld heat treatment details, and others. In addition to the recording of all the weldingvariables used during the test, in order to qualify a welding procedure, details of the inspection and test resultsmust also be recorded. These records must show that the inspection and testing has proven that the weldsamples have met or exceeded the specified standard requirement. The typical types of inspection and testingfor each sample for Welding Procedure Qualification are:

Inspection and Testing for Fillet Welds (Tee Joints) - This involves visual inspection of the completed weldfollowed by two macro etches, and one fillet weld break test. The welded sample is first inspected for anyvisual discontinuities and then sectioned, and two small samples removed at predetermined locations. Thesesmall samples are polished across their cross-section and then etched using some type of mild acid mixture,dependent on the base material used. The remaining welded sample is used as the fillet weld break test andis broken against the weld to reveal the internal structure of the weld for inspection.

Inspection and Testing for Groove welds (Butt Joints) This involves visual inspection, followed by twotransverse tensile tests, two root bend test and two face bend tests. (These tests are typical but may differdependent on material thickness, type and standard requirements. Different and/or additional testing, such asside bends, all weld tensile tests, impact testing or other testing may be required.) The completed weldcoupon, after visual inspection, is divided into predetermined small sections. Each section is prepared, usuallyby machining, to specific dimensions as prescribed by the standard. Each small sample is then testedmechanically to determine its characteristics. These samples are then inspected to determine theiracceptability, against specified acceptance criteria, as laid down by the applicable code or standard. Typically

the standard will provide the maximum size and location of various weld discontinuities and/or, as relevant,values such as minimum tensile strengths or minimum desired impact properties.

Samples that are found not to have discontinuities that exceed these specified limits, and that meet or exceedthe minimum values as specified in the standard, will be acceptable, and the welding procedure will bequalified.

The welding procedure is an important part of the overall welding quality system, as it provides documentedevidence that inspection and testing has been performed to ensure that welding can be conducted to meet arecognized standard.

* One exception to welding procedure qualification is the D1.1 Structural Welding Code for Steel, which will,under some circumstances, allow the use of pre-qualified welding procedures, however these procedures arestill required to be documented and meet all of the relevant code requirements.