Welding is one part of the construction process that requires a number of elements to be in place to assure proper performance. These elements are similar to the essential elements in other industrial processes: appropriate materials must to be used, people performing the work must be capable, procedures must be appropriate for the work, and such procedures must be followed. Finally, appropriate inspection must take place to ensure that all of these steps have been properly executed.
Engineers have many tasks in the course of their review work. Some of those tasks entail review and evaluation of welding documents and records.
American Welding Society (AWS) codes contain provisions describing minimum requirements for each of these elements, and documentation is required to assure each of these elements is in place. The three AWS codes most commonly applicable to building type structures are D1.1 Structural Welding Code - Steel, D1.3 Structural Welding Code - Sheet Steel, and D1.8 Structural Welding Code - Seismic Supplement. This article focuses on D1.1, but includes a few comments about D1.8. Steel Engineers should also be aware of D1.4 Structural Welding Code - Reinforcing Steel.
Documentation associated with welded construction fit into three broad categories, as follows:
- welding procedures
- qualifications of personnel
The topic of welding documentation must also include discussion of inspections and associated reporting (Table 1).
Table 1: Welding Quality Elements and Associated Documents.
Minimum requirements for documentation are specified in AWS codes, but distribution and review of this documentation is not specified. In many cases, owners rely on engineers to assist in determining what documentation to obtain. Some of the documentation contains information that only an engineer can evaluate, while other parts contain information that can be reviewed by an inspection agency. Generation of this documentation is usually part of the project’s contract work. However, review involves elements of responsibility, and distribution is time consuming and costly. Therefore discretion is required. Reviews should be performed efficiently. More sophisticated projects may deserve more documentation distribution and review.
In 2005, a series of documents regarding steel construction subject to seismic loads were published by the American Institute of Steel Construction (AISC) and AWS. These standards provide more guidance about quality assurance than codes used in other forms of construction. They require a few more documents and include provisions for document distribution and review.
Certainly one of the most influential materials in a welded joint is the base metal. Documentation of base metals is provided in accordance with ASTM A6 (Standard Specification for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling). Reviewers should look to assure that tensile and yield strengths are as specified, that elongation exceeds the minimum, and that the chemical makeup is within the specified range.
Common standards for welding consumables (filler metal, flux, and shielding gas) used in the building construction industry are the AWS A5 series of specifications. Certification of consumables is accomplished by placing the AWS specification and classification on the package or product. Typically, certificates of conformance are produced by consumable manufacturers, and are used in the general building construction industry to assure that welding consumables are produced in accordance with requirements of the applicable AWS A5 specification.
Certificates of conformance are collected and kept by fabricators using the products, but are usually distributed only upon request. Certificates of conformance contain a statement by the manufacturer that the product meets the requirements of the specification. Additionally, certificates provided by most US manufacturers also indicate test results to confirm that the material is representative of the product furnished and complies with the specified requirements. Typically, tests are conducted on a periodic basis as defined in AWS A5.01 Filler Metal Procurement Guidelines.
Filler metal and flux manufacturers make literature available to provide advice on product usage. This literature includes the AWS classification, the position in which electrode can be used, and the typical properties of the weld metal. The literature also includes welding procedure specification variables. Certificates of conformance and product literature are available on company websites.
Welding Personnel-Related Documentation
Every person placing a weld on the structure, including tack welders, must be “qualified.” As the term “qualified” is used in the D1.1 code, this refers not to the individual’s capability per se, but rather indicates that the welder has demonstrated his or her skills by making a weld under prescribed conditions. In the qualification test, the weld is then subjected to a variety of tests, including visual, non-destructive, and mechanical.
There are many different tests used to qualify welders, each providing a means of demonstrating different skills. Some tests include demonstrations of more than one skill, so one test may be used to qualify a person for a number of different welds in production. For example, a welder who has been qualified by making a vertical groove weld test plate is also qualified to make vertical, horizontal, and flat position complete joint penetration (CJP) and partial joint penetration (PJP) groove welds, as well as vertical, horizontal, and flat position fillet welds. A welder who qualifies on a horizontal fillet weld test plate is also qualified to weld horizontal and flat position fillets, but is not qualified to make any groove welds or any vertical fillet welds. AWS D1.1 Table 4.10 indicates the weld type, position, and product form (plate, round tubing, box tubing) for each test that is required, and also indicates what welding the individual may do when the prescribed test is successfully passed.
Base metal and weld thickness are also essential variables in welder qualification. AWS D1.1 Table 4.11 gives limits on what thickness of production joints are qualified (and for hollow structural steel (HSS), what diameter) depending on the dimension of the weld sample that is tested. While there are many options for qualifying welders, one test that is common is to weld a 1-inch groove weld, which then qualifies the welder for 1/8-inch to an unlimited plate thickness. A welder qualified on plate steel is also permitted to weld many joints on rectangular HSS and round HSS (with a diameter greater than 24 inches). The Welding Performance Qualification Record (WPQR) lists essential variables included in AWC D1.1 Table 4.12. These include:
- If Shielded Metal Arc Welding (SMAW), the Electrode Classification Group (F number)
- Diameter and or thickness
- If vertical, the progression (up or down)
- The use of multiple electrodes (for operators).
Figure 1 shows the example WPQR form from AWS D1.1. The completed form will indicate the welder’s identity, essential variables of the test weld, and a record of examinations and tests performed on the weld. All test plate welds are visually examined and then subjected to bend or radiographic tests. WPQRs are normally maintained by the company employing the welder and are made available for inspection upon request.
Figure 1: WPQR Form published with permission of the American Welding Society.
Engineers and inspectors that review welder qualification records should examine them to see that the welder has passed a test in the particular procedure, and that the procedure defines the product form (pipe or plate) in the size range and in the position that qualifies that welder for the work being performed.
Welding Procedure-Related Documentation
The term ‘welding procedure specification’ or WPS refers to a written document that defines the quantifiable conditions under which a weld is to be made (Figure 2). The WPS includes variables shown in Table 2. (Note, figures and tables listed in this table refer to AWS D1.1). To ensure that the combination of variables will result in a weld of the appropriate quality, two approaches are used by AWS D1.1: the WPS may be prequalified, or the WPS may be qualified by test. Both prequalified WPSs and WPSs qualified by test list essential variables that are to be used when making a weld.
Figure 2: Sample WPS Qualified by Test. Published with permission of the American Welding Society.
Table 2: Variables Included on a WPS.
A feature of the AWS D1.1 welding code is its recognition of many procedures that have been used commonly and successfully for many years in structural production and therefore do not have to be retested by each company using them. These procedures are considered ‘prequalified.’ Chapter 3 of the D1.1 code prescribes conditions that must all be met in order for a WPS to be prequalified. These conditions include the following broad topics:
- Filler metal/base metal combination.
- Preheat conditions.
- Weld joint details, including groove details for CJP and PJP groove welds.
- Welding parameters (amperage, weld layer thicknesses, etc.).
WPSs Qualified by Test
Weld procedure specifications that do not meet all of the requirements in Chapter 3 may be qualified by test. Welds using materials that are not listed in Table 3.1, joint geometries other than those shown in Figures 3.3 through 3.11, and electrical variables outside the manufacturer’s recommendations may be demonstrated to be adequate for use by test. Qualification tests are conducted by welding a test plate using the parameters to be tested and by subjecting the weld to bend tests, tensile tests and, if required, Charpy V-notch tests. Test results and variables qualified are shown in a Procedure Qualification Record (PQR) (Figure 3).
Figure 3: Sample Procedure Qualification Records. Published with permission of the American Welding Society.
Whether the WPS is prequalified or qualified by test, it must be written and must be made available to those authorized to review them, including the engineer. WPS’s can be reviewed to ensure that they are applicable for the work being performed. Prequalified WPSs can be compared to the requirements of D1.1 Chapter 3 to ensure full compliance. WPSs that have been qualified by test can be compared to the PQR and the limitation of variables contained in AWS D1.1 Chapter 4 to ensure that any differences between WPS parameters and those listed on the PQR are within appropriate limits.
To ensure that inspectors are qualified, D1.1 provides three bases of qualification: 1) current or previous certification to AWS Certified Welding Inspector requirements, 2) current or previous qualification by the Canadian Welding Bureau requirements, or 3) an individual who by training or experience is competent to perform the inspection. The engineer is specifically authorized to review qualifications of inspectors. Documentation associated with inspectors typically consists of copies of certificates that demonstrate compliance with the first two options provided.
During welding, inspectors should make certain that all weld operations are performed in accordance with the WPSs. Inspectors are to confirm that welds are made by qualified welders. Welds are to be visually inspected. The welding code includes provisions and acceptance criteria for nondestructive testing methods including visual, but, except for some cyclically loaded joints, the code does not require methods other than visual to be used. Inspectors are to document inspection of welds by marking the material inspected. They are to keep records of WPS qualifications, welder’s qualifications and ‘other such information as may be required.’
While there are no more specific requirements or recommendations for these inspection tasks, most inspectors record the work they have inspected by general description and describe non-conforming work that has not been repaired. The description of non-conforming work should include the location, a description of the non-conformance, and a reference to the requirement that has not been met. Welds are permitted to have discontinuities and the inspector must compare those discontinuities to the acceptance criteria in the code to determine if the weld is to be rejected.
Figures 4, 5 and 6 are examples of forms for reporting Magnetic-Particle Tests (MT), Radiographic Tests (RT) and Ultrasonic Tests (UT) examinations. Submissions of copies of these completed forms are the typical documentation required to ensure such inspections have been performed.
Figure 4: Example RT form.
Figure 5: Example MT Form.
Figure 6: Example UT Form.
Supplemental Requirements for Welds in a Seismic Load Resisting System
AISC’s Seismic Provisions (341-05) contain supplemental requirements for welding in Appendix W and information on quality control and quality assurance in Appendix Q. The requirements in Appendix W were included in the Seismic Provisions primarily because the AWS document was finalized and published subsequent to the date the Seismic Provisions were adopted. The requirements of Appendix W are expected to be substantially superseded by AWS D1.8 Structural Welding Code - Seismic Supplement in the next publication cycle of AWS D1.8. The QA/QC plan in the Seismic Provisions is provided for use by the engineer in response to the International Building Code requirements to establish a QA Plan. While the Seismic Provisions stipulate what QA/QC tasks to perform, AWS D1.8 Section 7 includes requirements that supplement the non-destructive testing (NDT) methods and acceptance criteria of D1.1. Section Q5.1 of AISC 341-05 includes a table indicating what visual inspections to perform and what to document. Section Q5.2 lists NDT requirements other than visual inspection.
Selected items to note in these documents are:
▪ AISC 341 lists specific visual inspection points and assigns one of two different inspection frequencies and documentation requirements to these inspection points.
▪ AISC 341 Section Q3 is a specific list of documents to be submitted by the contractor for review by the engineer and a list of documents to be available for review upon request.
Documents to be submitted are:
1) Shop Drawings.
2) Erection Drawings.
3) Weld Procedure Specifications listing variables required in D1.1.
In addition to the variables required in D1.1, procedures for seismically loaded structures indicate:
a) Power source. Constant current (usual for SMAW) or constant voltage (usually for FCAW or GMAW).
b) For demand critical welds, electrode manufacturer and trade name.
4) Certificates of conformance for electrodes, flux, and gasses. (Certificates of conformance for SMAW, FCAW and Submerged Arc Welding (SAW) should indicate 16mL/100g of diffusible hydrogen or less for selected filler metals).
5) For demand critical welds, a certificate stating that the filler metal meets the supplemental notch toughness requirements (Hi-Lo CVN Tests) defined in D1.8 Annex A.
6) Manufacturers product data sheets for Shielded Metal, Flux Cored, and Gas Metal Arc Welding composite electrodes.
Documents to be available for review include:
1) Material test reports for steel, bolts, shear connectors, and welding materials.
2) Inspection procedures.
3) Nonconformance procedures.
4) Material control procedures.
5) Bolt installation procedures.
6) WPQRs (including those indicating performance of the supplemental welder qualification test for welding the bottom flange of beams to column flanges).
7) QC Inspector qualifications (including supplemental UT qualifications as specified in D1.8 Annex E).
Quality Assurance agencies also have a list of documents to submit:
1) QA Agency written practices including personnel selection and qualifications and inspection procedures.
2) Management qualifications.
3) Qualification records for inspectors and NDT technicians.
4) NDT procedures and calibration records.
5) Periodic inspection reports.
6) Nonconformance reports.
It has been said that if you fail to plan, you plan to fail. Documentation of various welding-related requirements ensures that a degree of planning has already taken place: that the materials, personnel, and procedures are in place for a successful project. Far from being an unnecessary paperwork task, these documents are important to ensure a quality structure.▪