What they are, when they're used, and how they're developed
January 24, 2002
Many aspects of welded component design and fabrication are governed by documents known as codes and standards.
Many aspects of welded component design and fabrication are governed by documents known as codes and standards. End users or purchasers often specify these documents in a contractual agreement to control the characteristics of the welded component that may affect its service requirements. Manufacturers also use them to assist in the development and implementation of their welding quality systems.
Many end users of welded components have developed and issued specifications that address their own requirements. However, national interest in areas such as public safety and reliability has promoted the development of welding codes and standards that command industrywide or national recognition.
For example, national engineering and technical societies have developed numerous committees that continue to evaluate the needs of industry and develop new welding codes and standards. The members of these committees are technical experts and represent all interested parties, such as manufacturers, end users, inspection authorities, and government agencies. After a committee completes a new or revised document, it usually is reviewed and approved by a review committee and published in the name of the applicable engineering society if it is accepted.
Legislative bodies or federal regulating agencies sometimes adopt documents that have significant influence on public health and safety. In those jurisdictions, such documents become law and often are referred to as codes or regulations.
Welding inspectors should know which codes and standards are applicable within their jurisdiction, understand the requirements of the relevant documents, and perform their inspections accordingly.
Following are some of the more popular sources of welding codes and standards in the U.S.
American Welding Society (AWS). AWS publishes many documents addressing welding use and quality control. 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 MechanicalEngineers (ASME). This society 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. ASME also produces the Code for Pressure Piping, which consists of seven sections, each prescribing the minimum requirements for the design, materials, fabrication, erection, testing, and inspection of a particular type of piping system.
American Petroleum Institute (API). This institute publishes many documents relating to petroleum production, a number of which include welding requirements. The most well-known is possibly API Std 1104—Standard for Welding Pipelines and Related Facilities.
The specific content and requirements of a welding code or standard can vary in detail, but they have some basic elements in common.
Scope and General Requirements. This usually is found at the beginning of the document and typically describes the type and extent of welding fabrication for which the document should be used. It also may explain limitations for the document's use.
Design. If the document provides a section for design, it may contain minimum requirements for the design of specific welded connections, or it may refer the user to a secondary source of information.
Qualification. This section typically outlines the requirements for qualification testing of welding procedure specifications, as well as the requirements for qualifying welders. It may provide the essential variables, which typically have change limitations of each variable that govern the extent of qualification. Essential variables typically include:
This section of the document also may provide the qualification testing requirements, which usually are divided into welding procedure and welder performance. Typically, it provides 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 for evaluating the test samples.
Fabrication. This section, when included in the document, typically discusses fabrication methods or workmanship standards. It may contain information and requirements for base materials, welding consumables, shielding gas quality, and heat treatment.
Inspection. This section of the document usually addresses the welding inspector's qualification requirements and responsibilities, acceptance criteria for weld discontinuities, and the requirements for nondestructive testing procedures.
Welding fabricators often use welding codes and standards to achieve process control to meet the requirements of ISO 9000 and other quality management systems. Often the major elements of process control specified by quality management systems are the same elements addressed in welding codes and standards:
Regardless of a fabricator's overall quality system, selection of the appropriate welding codes and standards can help improve welding quality and reliability even more.