Of course, in the field and shop work welding procedure developments, the pre-WPS, WPS of Welding Procedures, and the PQR record of the Procedure Qualification plays the most vital documented instructions that helps to ensure repeatability and quality welds for critical systems.
In fact, the WPS’s and PQR’s serves as standard layouts to produce sound welds in a consistent, efficient, and safe aspect.
Table of contents
- What is Pre-WPS?
- What is a Procedure Qualification Record (PQR)?
- What is a Welding Procedure Specification (WPS)?
- What are the major WPS Standards followed by Industries?
- What’s a WPDS?
- Whar is a SWPS (Standard Welding Procedure Specifications)?
- Practical Guide to Writing a WPS
- Basic Information on a WPS/PQR
- Know the Welding Data – Essential, non-essential and supplementary essential variables
- Joint Design and Base Material
- Thickness and Diameter for Qualifications
- Understanding the parent material grouping P-No.
- Filler Metals, the Metal groupings F-No. and Composition groupings A-No.
- Understand ASME Section II Part C
- Welding Positions (Flat, Vertical, Horizontal and Overhead)
- Know the Welding Procedure Parameters
- Understanding the Types of Tests Applicable
- Location Marking and Dimensioning of Test Specimens
- The Acceptance Criteria for Qualification Tests
- Field Documentation
What is Pre-WPS?
For instance, let us consider there is no procedure for a weld related to a new material. Therefore, a Pre-WPS or p-WPS has been to define the set of essential, non-essential and if required the supplementary essential variables for testing Procedure Qualification for new production welds.
Meanwhile, pre-WPS developed should consider all relevant documentations from construction drawings to field production requirements that stipulate the base metal, required filler metal, current, backing gas, heat treatment, and test coupon requirements for the test. Moreover, this preliminary procedure may involve multiple coupon welds and needs mechanical testing to ensure they meet all applicable requirements.
In other words, a preliminary WPS helps record all real time data parameters from base metals, current, and heat input requirements. This forms a basis of initial PQR and subsequently, the WPS for the job, after required testing and approvals to the minimum code requirements.
What is a Procedure Qualification Record (PQR)?
A PQR or a procedure qualification record is a document that shows the results of mechanical and NDE tests done by an approved laboratory. To make sure the procedure results in a satisfactory weld, tests needs to be done to code requirements and by an authorized personnel.
Consequently, the purpose of the Procedure Qualification Record is to test the proposed coupon for design and weld joint considerations. Design requirements, for instance, include the mechanical properties and chemical composition of the material at intended pressure and temperature. Moreover, the weld joint parts should meet or exceed the expectations of strength at the intended pressure and temperature.
Unlike WPS, the PQR’s have been limited to the essential variables of the process. Once the procedures have been defined, and accepted by all parties, the respective code has to be referred for for all the essential, non-essential and supplementary essential variables. For instance, for a 6″ piping material with 10mm thickness are limited to range of 1.5mm to 20mm during production. Therefore, multiple welding procedures (WPS) can be created with single procedure qualification provided, diameter range for each welding procedure and other essential variables) are supported by a PQR.
What is a Welding Procedure Specification (WPS)?
Welding Procedure Specifications (WPS), specifically, details the parameters of a qualified PQR, and documents the limitations for use in the production welds as per the applicable code requirements.
For that reason, a WPS acts as a guiding document for shop and field for ranges of acceptable production welds. Moreover, a welding procedure is qualified only if a PQR is approved with all test acceptance criteria.
What are the major WPS Standards followed by Industries?
The most widely used standards that have been practiced for preparation of WPS/PQR are listed hereunder, such as:
AWS D1.1 – Structural Steel Welding Standard
AWS D1.3 Sheet metal Welding for thickness less than 5mm
AWS D1.6 –Structural Stainless Steel welding
ASME Section IX – Boiler & Pressure Vessel Code
ISO 15614 – International Standard for WPS
BS EN15614 British Standard (similar to ISO 15614)
CSA W47.1 and W59 – Canadian Welding Standards for Welder Qualification
AS/NZS 2980 – Australian Structural welding standard
What’s a WPDS?
Canadian Welding Bureau (CWB) division 1, 2 and 3 companies follow a certain requirement to outline the essential requirement like weld parameters, material, thickness and ranges in a standard format before a Welding procedure test. For this reason, the documents have been noted as WPDS (Welding Procedure Data Sheet), which is a guideline as datasheet to avoid errors.
Whar is a SWPS (Standard Welding Procedure Specifications)?
The American Welding Society, provides set of Standard Welding Procedure Specifications (SWPSs), in other words, pre-qualified welding procedures, that are intents to meet requirements for major codes like AWS Structural Codes (D1.1, D1.2, D1.3, etc.), ASME Boiler and Pressure Vessel Code, Section IX, as guidance welding procedures based on successful weld constructions.
Moreover, these SWPSs are supports relevant Procedure Qualification Records (PQRs) which meet the rules of AWS B2.1 reviewed and approved by WRC Welding Procedures Committee.
Though the SWPS’s saves time, money and expertise they are mostly intent for common materials and process. Hence, they are in use by companies performing welding without a qualification test. Consequently, the manufacturer implementing SWPS’s should record and document their welding experience. This procedure is not applicable in case of impact test requirement.
However, the articles on web suggests use of a standard qualification test rather than a SWPS’s. Because, as there are certain negative impact regarding proper use and understanding the correct requirements before application. Refer Mandatory Appendix E of ASME Section IX for Permitted SWPSs. Meanwhile, the SWPSs have to be purchased from AWS.
Practical Guide to Writing a WPS
A Welding Procedure and the supporting Procedure Qualifications, obviously, represent the basis of satisfactory production welds. Besides, we will see the various sections of WPS/PQR and how they relate as per the ASME BPVC Section IX Standard WPS / PQR format QW-482 / QW-483.
Breaking down the important aspects of the WPS/PQR
Basic Information on a WPS/PQR
Specifically, every section of the PQR requires to be duly filled and recorded as it forms the basis for WPS and subsequent production welds. Therefore, includes the name of testing organization (company), unique PQR and WPS No., the WPS revision, the supporting PQR’s (for WPS), date of tests, the WPS reference, the welding process and type of welding (manual, automatic or semiautomatic).
Know the Welding Data – Essential, non-essential and supplementary essential variables
Essential variables are that variables when changes to certain parameters are in need, a new qualification is mandatory. Non-essential variables, though changes are accepted, must comply with the code limits for acceptance, where there is no need for a new qualification.. When there is a notch toughness test requirement, the supplementary essential variables become an essential variable.
Joint Design and Base Material
The PQR section, QW-402 Joints, defines the exact groove joint design parameters (sketched) like angle, backing, root spacing and thickness used for the procedure qualification test. Details like the number of passes (weld layers) help define a structure approach in welds. The joint variables differ based on the process applied.
In contrast, the WPS section, defines the parameter ranges qualified based on the PQR test.
Since the document is for production welds, the WPS format clearly defines the base materials (QW-403), their groups to which they are to be weld with. Material grouping can be verified from table of the ASME Sec IX, QW-422.
Thickness and Diameter for Qualifications
Likewise, record the exact details of the base coupon. This includes the material, Grade, P-No., thickness, diameter, and the maximum pass thickness to the PQR. Moreover, the specimen thickness qualification limitations is under Table QW-451.1 of ASME Section IX.
Most importantly, the WPS thickness range qualified should relate to the actual thickness welded on the PQR as per Code.
Understanding the parent material grouping P-No.
The WPS/PQR documents should specifically define the base materials (QW-403), their groups to which they are to be welded with.
Besides, the material grouping can be verified from the table of the ASME Sec IX, QW-422. Moreover, the thickness range qualified should be about the actual thickness welded on the PQR.
Filler Metals, the Metal groupings F-No. and Composition groupings A-No.
The filler metals selected should match or exceed the minimum specified Tensile strength properties of the base material. In certain cases, the codes or contract requirements will need additional mechanical properties and should be required to be taken into consideration. Specific tests and evaluations need to be considered in the procedure.
The F-number (QW-404.4) and A-numbers (QW-404.5) are essential variables in a WPS. However, diameter ranges is non-essential (QW 404.6), and can be varied based on heat input.
For F-Numbers Refer QW-432 for Grouping of Electrodes and Welding Rods for Qualification in ASME BPVC Section IX.
The actual filler metals used based on the specification and classification as per standards tabled in QW-432, and should be recorded in the PQR.
The selected filler metals should meet the required pre-heat and inter-pass temperatures.
Commercial names of electrodes and their designations though not essential parameters may serve as information on the type of flux being used or the required heat input data constraints.
Understand ASME Section II Part C
Especially, the ASME Section MATERIALS Part C Specifications for Welding Rods, Electrodes, and Filler Metals. ASME BPVC II.C-2019 specifically mentions the various aspects of the base materials and the compatible filler metal that has to be used for the process.
Moreover, the Specification for Filler Analysis (SFA No.), the AWS classification of Welding Consumables, and the limits for chemical composition and mechanical properties (including capability after PWHT) of consumables have been defined in ASME Part C.
Welding Positions (Flat, Vertical, Horizontal and Overhead)
The position of weld does have its impact as well. The shop floor and field access requirements are some of the aspects that need to be considered before drafting a WPS.. For that reason, most WPS or Welder performance testing (WPQ) define a 6G position. Various limitations considered for the different qualification positions with reference to QW-465 for plates and pipes.
Know the Welding Procedure Parameters
The Current, Voltage, Polarity, Wire Feed, Travel Speed, Heat Input, Torch Angle, Weave Technique, Cleaning Technique, and the Thermal Parameters (Pre-heat, interpass, and post heat treatment) values play a significant part in the PQR and subsequently, the WPS.
Also, refer Article IV welding data, only if mentioned by other articles in the section.
Understanding the Types of Tests Applicable
Various tests with reference to Section QW 141 mechanical tests, like, the Tension Tests (QW-150), Guided Bend Test (QW-160), Fillet-Weld Tests (QW-180), Toughness Tests (QW-171 & QW-172), and Stud-Weld Test (Figures QW-466.4, QW-466.5, and QW-466.6) and macro examination (QW-202.5).
Location Marking and Dimensioning of Test Specimens
Further, the dimensioning requirements to QW-462 Test Specimens shall be followed (unless tolerance limitations are specified) for respective Qualification Tests.
The Acceptance Criteria for Qualification Tests
Meanwhile, a clear understanding of the qualification acceptance criteria applicable for different types of testing needs evaluation with relevant ASME Sections.
- QW-153 Tension Tests
- QW-163 Bend Tests
- QW-171.2 & QW-172.2 Toughness Tests
- QW-184 Macro Examination
- QW-191.1.2 Volumetric NDE
- QW-191.2.2 & QW-191.2.3 Ultrasonic Test
- QW-192.1.2, QW-192.1.3, QW-192.1.4 & QW-192.2.2 Stud Weld Test
- QW-193.1.1, QW-193.1.2 & QW-193.1.3 Tube to Tube sheet Test
- QW-194 Visual Examination.
- QW-195.2 Liquid Penetrant
- QW-196 Resistant Welding
- QW-197.1.2, QW-197.1.3 & QW-197.2.2 Laser Beam Welding (LBW) QW-199 Flash Welding
Equally important, the procedure specifications (PQR) shall be available for reference, and review at the fabrication site, as per Code.
However, as normal practice, the construction/fabrication sites should document the client’s requirements and as a minimum, the weld map, construction documents, the WPS’s used, and the Material Safety Data Sheet (SDS) is for welding consumables and related products.
For a brief understanding of ASME Section IX for welding (QW), the various sections are shared in the article on codes here. Recommended that you purchase the newest edition of ASME Section IX for understanding the criteria and their limitations.