The welding code has many provisions and every welded joint uses many selected essential variables. The written WPS is our record of controllable and measurable variables used on each joint. Control of those variables and qualification of the welders is the industry method of providing reliability of welded assemblies. WPSs for bridges are approved by the Owner, often a State; WPSs for seismically loaded structures are submitted to the Engineer of Record for review (Seismic Provisions Section J3.1). WPSs for other structures are provided to authorized agents on their request. Welds deposited out of compliance with the WPS may not provide the needed properties. Some WPSs are qualified by test and others are prequalified. All WPSs have essential variables that must be documented. Prequalified WPSs have properties that must comply with the requirements of AWS D1.1/D1.1M Chapter 5 that result from documented variables and technique such as pass thickness and width limits.

WPSs are either prequalified or qualified by test. SMAW, GMAW (except GMAW Short Circuit), SAW, and FCAW procedures can be prequalified. GTAW, GMAW-s, EGW, and ESW procedures cannot be prequalified. Prequalified procedures must comply with all the provisions of AWS D1.1:D1.1M Clause 5. Qualification of WPSs that are not prequalified includes welding a sample of the joint to be qualified and subjecting it to visual, NDE, and mechanical property tests. The number of tests required, and a description of the tests is given in AWS D1.1:D1.1M Clause 6. Many WPSs can be written based on one set of tests. WPS qualifications are dependent on weld type (groove, fillet, or plug), position, and whether the weld it tubular or not. Each test has many essential variables. Changes in variables that can be covered by one test and changes that require a new test are defined in AWS D1.1:D1.1M Clause 6. Qualification tests in 2021 were reported to cost as much as $10,000. Some variable changes that require new tests are process, position, base metal outside the group, some changes in filler metal, etc. (See AWS D1.1:D1.1M Table 6.5 for a complete list). Documentation of a WPS qualification test is called a procedure qualification record (PQR). It should include a trial WPS showing the variables used in making the sample signed by a QC representative and sometimes by an independent witness and a test report signed by the responsible person at the test laboratory.

Welder qualifications are also described in Clause 6 of AWS D1.1:D1.1M. Welders, welding operators, and tack welders all need to be qualified. Welders continue to be qualified as long as they continue to weld using the process they are qualified in every 6 months. As with WPSs the welder qualification consists of welding a test plate assembly and having that assembly visually inspected and bend tested or RTd. Evidence of a welder qualification is called a Welder Performance Qualification Record (WPQR). Welder qualifications are dependent on weld type (groove, fillet, or plug) and position and whether they are for tubular or non-tubular joints. Base metal thickness can be a welder qualification limit but many welders in the structural steel industry test on a 1-in. plate which qualifies them to weld any material over 1/8 in. SMAW welders can be limited to electrode classifications.

As stated in AWS D1.1:D1.1M Section  6.2, properly documented evidence of previous qualification of joint welding procedures should be accepted without re-qualification. Additionally, properly documented evidence of previous qualification of welders, welding operators, and tackers should be accepted without re-qualification, provided that the period of effectiveness has been maintained as described in AWS D1.1:D1.1M, Section  6.2.3.1.