Welding Procedure Terms (WPS, PQR, WPQR)

1. Welding Procedure Terms

The welding profession requires skill. Determining “how to weld” requires specific knowledge related to the base materials being welded, the type of welding process/method, and several other related factors. In actual welding production, many factors contribute to the welding process and directly affect productivity and quality.

Therefore, the knowledge/competency of the welding engineer and the skills of the welder must be assessed through a series of tests/inspections. All this information must be documented and presented in documents such as:

• Welding Procedure Specification – WPS, Procedure Qualification Record – PQR, Independent laboratory test report for PQR – Test Report, and Independent laboratory test report for WPQR; OR
• Pre-qualified Welding Procedure Specification – Pre-qualified WPS (only applicable according to certain standards/codes), Welder Performance Qualification Record – WPQR, and Independent laboratory test report for WPQR; OR
• Standard Welding Procedure Specification – SWPS, Welder Performance Qualification Record – WPQR, and Independent laboratory test report for WPQR.

These are considered terms in the welding field and are widely applied around the world.

2. What is a Welding Procedure Specification (WPS)?

A Welding Procedure Specification (WPS) is a document that describes the methodology for performing welding tasks in actual production. Its purpose is to assist in planning and controlling welding quality. The WPS is recommended for all welding processes and is often required by most codes and standards.

3. What is a Procedure Qualification Record (PQR)?

A PQR is required when it is necessary to demonstrate that a plant/manufacturing unit has the capability to produce welds that meet the technical requirements for mechanical properties and metallurgical characteristics.

Welding procedures must be qualified according to the technical requirements specified in the applicable welding standards or codes. For example, in the ASME Section IX code, the steps in a welding procedure qualification report are outlined as follows:

• Develop a Welding Procedure Specification (WPS) as described above.
• Weld a test coupon according to the specified technical requirements. The assembly of the joint, welding, and visual inspection of the finished weld must be witnessed by a Certified Welding Inspector (CWI) accredited by the American Welding Society (AWS) or by an independent inspection agency. Welding parameters used during the welding of the test coupon, such as welding current, preheat temperature, etc., must be fully recorded during execution.
• Upon completion of welding, the test coupon must undergo both destructive testing (DT) and non-destructive testing (NDT/NDE) such as radiographic testing (RT) and mechanical testing as specified in the applicable standard or code. This work must be performed by an accredited testing laboratory. An independent inspection agency may be required to witness the entire testing process and review all RT films.
• If the test results meet the requirements, the documentation must be signed and stamped by the individual who conducted the inspection.

4. What information should be included in the WPS and PQR?

Detailed and comprehensive information helps all personnel involved in the welding work (welders, welding supervisors, welding inspectors, or welding engineers) apply the procedure correctly and produce welds that meet quality requirements. The amount of information and the level of quality control specified in a WPS depend on the application and the acceptance criteria of the weld joint.

For the WPS, in most applications, the required information is typically similar to that in the PQR, except that some parameters are expanded to cover a range of applications, such as thickness range, diameter, welding current, material group, etc., or joint type.

If the WPS is used in conjunction with the PQR, the ranges of application in the WPS must comply with the ranges qualified by the PQR.

In actual production, care must be taken when specifying application ranges to ensure feasibility and the technological capability of the production team.

5. What is a Prequalified Welding Procedure Specification (Prequalified WPS)?

Some standards/codes, such as AWS D1.1, allow the use of Prequalified Welding Procedure Specifications (Prequalified WPS) which are developed based on pre-established criteria that ensure the technical requirements for mechanical properties and metallurgical characteristics are met.

With Prequalified WPSs, it is not necessary to perform a Procedure Qualification Record (PQR). However, the technological parameters in a Prequalified WPS have specific application ranges for each type of weld. When the welding parameters fall outside these ranges, a new WPS must be qualified with a PQR.

6. What is a Standard Welding Procedure Specification (SWPS)?

To standardize and streamline the approval process for WPSs, AWS has established Standard Welding Procedure Specifications (SWPSs). The technical parameters in these standard specifications are based on extensive industrial experience and expert knowledge. For these SWPSs, it is not necessary to perform PQR qualification since they are developed based on a large number of prequalified PQRs.

When using SWPSs that are accepted by the applicable standard/code, the manufacturing unit does not need to perform WPS qualification. Manufacturers can purchase SWPSs from the American Welding Society (AWS) for unlimited internal use.

7. Welder Performance Qualification Record (WPQR)

Once the welding procedure is approved, the next step is to qualify all welders involved in the work to ensure they have the knowledge and skills to produce quality welds. If the welder was involved in the procedure qualification, they are automatically qualified. Other welders must be qualified according to a process that conforms to the applicable standards or codes.

The following are the requirements for welder qualification according to ASME Section IX:

• Complete a test as mentioned above. The test should be chosen to match the actual production conditions, and the position/orientation of the weld test should correspond to the position/orientation of the weld in production.
• The highest level of qualification is the 6G position, which involves welding a pipe at a 45-degree angle without rotation, qualifying the welder for all positions except vertical down welding.
• Inspect the completed weld according to the relevant standards/codes to ensure it meets visual appearance requirements.
• For butt joints, after visual inspection, further testing such as radiographic testing (RT) or bend testing is typically required.
• After completing the inspection steps, a certification record must be created and signed by a welding inspector or an assessor from the certification body.
• Note that any changes requiring a new WPS may also apply to welder qualification. Refer to the applicable standards/codes for accurate information.

8. Acceptance Criteria

Generally, the quality of a weld can be evaluated based on its appearance. The weld root must be completely fused along its length, the weld surface must transition smoothly to the base metal, and no defects should be detected. The evaluation of these criteria must be based on the specified acceptance criteria/standards.

9. PQR/WPQR Testing

The following testing methods may be required to be performed by an independent laboratory for PQR and WPQR samples:

• Weld Visual Examination by an AWS Certified Welding Inspector (CWI)
• Bend Test
• Hardness Test
• Transverse Tensile Test
• All Weld Metal Tensile Test
• Charpy Impact Test
• Weld Metal Chemical Analysis
• Macroetch Test
• Torque Test
• Peel Test
• Nick Break Test
• Radiographic Test (RT)
• Ultrasonic Test (UT)

10. Measuring and Inspecting Welds

In addition to the above-listed testing methods, the manufacturing unit may also require independent inspections by individuals with recognized certification such as:

•  Visual Inspection by AWS Certified Welding Inspector (CWI)
•  Radiographic Testing by Level II personnel certified as per SNT-TC-1A
•  Ultrasonic Testing by Level II personnel certified as per SNT-TC-1A
•  Magnetic Particle Testing by Level II personnel certified as per SNT-TC-1A
•  Penetrant Testing by Level II personnel certified as per SNT-TC-1A