Establishing quality systems for welding
Welding codes and standards exist for a reason. They provide a framework for welders and shop managers to keep quality a top priority in their work.
Using a quality system for welding that is developed according to welding code or standard requirements, may be an opportunity for the welding fabricator to improve weld quality and reliability.
With more manufacturers implementing quality management systems, such as ISO 9000, and requiring such systems for process control, we must consider welding as a special process and, consequently, its formal control.
Welding codes and standards often are used by a welding fabricator to assist with the development of a process control system. If we consider the major elements of process control, as specified by such standards for quality systems, we will see those same elements addressed within the welding code or standard. The first requirement for process control is documented procedures defining the manner of production.
For welding, this is the welding procedure specification (WPS). A second requirement is criteria for workmanship, which should be stipulated in the clearest practical manner. For welding, this may be the code or standard acceptance criteria. A third requirement is qualification of personnel. This may be addressed by the welder performance qualification. Regardless of the manufacturer's overall quality system, selecting and using appropriate welding codes or standards offer opportunities for welding quality and reliability improvements.
Codes and Standards: An Overview
Many aspects of the design and fabrication of welded components are governed by codes and standards. These documents also are called guides, recommended practices, regulations, rules, and specifications. End users and purchasers often cast the documents as contractual agreements to control the characteristics of a welded fabrication that may affect the product's service requirements. Manufacturers also use them to develop and implement their welding quality systems.
Many end users of welded components have developed and issued specifications to address their specific requirements. Such specifications may be limited in application and related only to that customer's situation and requirements.
National interest in areas such as public safety and reliability has prompted the development of welding codes and standards that command broader recognition, both on a national and industry-specific basis. Numerous committees have been formed over the years within national engineering and technical societies to evaluate the needs of their respective industries and create new welding codes and standards. Such committees comprise members who are technical experts and represent all interested parties, such as manufacturers, end users, inspection authorities, and government agencies.
The membership of these committees usually is balanced to prevent any one interest group from controlling the committee. When a new or revised document is completed by a specific committee, the new text usually is reviewed and approved by a review committee; if accepted, the standards then are published. Documents that have significant influence on public health and safety sometimes are adopted by legislative bodies or by federal regulating agencies. In those jurisdictions, such documents become law and are often referred to as codes or regulations.
Welding inspectors should be aware of which codes and standards are applicable within their jurisdictions, understand the requirements of the relevant documents, and perform their inspections accordingly.
Code and Standard Sources
The following are some of the more popular sources of U.S. welding codes and standards:
- American Welding Society (AWS). AWS probably is the largest producer of welding codes and standards in the U.S. The AWS publishes many documents addressing the use and quality control of welding. These documents include such general subjects as "Welding Definitions and Symbols," "Classification of Filler Metals," "Qualification and Testing," "Welding Processes," "Welding Applications," and "Safety."
- American Society of Mechanical Engineers (ASME). ASME is responsible for the development of the "Boiler and Pressure Vessel" code, which contains 11 sections and covers the design, construction, and inspection of boilers and pressure vessels.
- American Petroleum Institute (API). The API publishes many documents relating to petroleum production, a number of which include welding requirements. The best-known might be API Std 1104—"Standard for Welding Pipelines and Related Facilities."
The group also produces the "Code for Pressure Piping," which comprises seven sections. Each section prescribes the minimum requirements for the design, materials, fabrication, erection, testing, and inspection of a particular type of piping system. Both of these documents are American National Standards.
What Codes Provide
The content and requirements of welding codes or standards vary, but these documents have a number of elements in common.
Scope and General Requirements. General requirements are found at the beginning of the document. They are important because they usually provide a description of the type and extent of welding fabrication for which the document was developed and intended. It also may provide information relating to the limitations for use of the document. Care should be taken to use codes and standards that are applicable for a particular application.
Design. If the document covers design, it may refer the user to a secondary source of information, or it may contain minimum requirements for the design of specific welded connections.
Qualification. This section of the document typically outlines the requirements for qualification testing of the WPS and also those requirements for qualification of welding personnel. It may provide the essential variables, such as the change limitations that govern the extent of qualification. Such variables typically include the welding process, base metal type and thickness, filler metal type, electrical parameters, joint design, and welding position.
This section of the document also may give the qualification testing requirements. Usually this section is divided into welding procedure and welder performance testing requirements. It should specify the types and sizes of test samples to be welded and prepared for testing, the testing methods to be used, and the minimum acceptance criteria to be used to evaluate test samples.
Fabrication. This section, when included in the document, typically provides information associated with the fabrication methods and workmanship standards. It may contain information and requirements on such items as base materials, welding consumable classification requirements, shielding gas quality, heat-treatment requirements, and preparation and care of base material.
Inspection. This section of the document typically addresses welding inspectors' qualification requirements and responsibilities, acceptance criteria for discontinuities, and requirements relating to procedures for nondestructive testing.