The extent of certification is described by a number of variables, which include the specific welding process, type of deposited metal, thickness, joint design, position, backing, and others.
In the USA, welder qualification is performed according to AWS D1.1,[1] ASME Section IX[2] and API 1104[3] standards, which are also used in some other countries.
Under these CSA standards, welder qualification testing is carried out every 2 years by the Canadian Welding Bureau to ensure ongoing competence.
However some Qualifications are only valid for a single project, while others are unlimited as long as welders do not go beyond a specified length of time without performing that specific type of welding (this period is typically 6 months).
In 2008, the American Petroleum Institute introduced the API 577 Advanced Welding Inspection and Metallurgy programme of certification.
Certification is issued following the successful completion of a multiple choice exam which is based on the recommended practice document API 577.