Welding procedure specification (WPS): when a buyer should ask for one and how to check it against the job

A welding procedure specification (WPS) is the written method for making a welded joint. TWI, the UK welding research and technology organisation, describes it as the document that "details the welding variables to be used to ensure a welded joint will achieve the specified levels of weld quality and mechanical properties".^[7]

In South Africa, SANS 15609-1:2007, the adoption of ISO 15609-1, sets what a welding procedure specification for arc welding must contain. It replaced SANS 9956-2 of 1995, a number older procedure documents may still carry.^[2]

A WPS is qualified before production welding. SANS 15614-1:2007, the adoption of ISO 15614-1, specifies how a preliminary welding procedure specification (pWPS) is qualified by welding procedure tests, for arc and gas welding of steels and arc welding of nickel and nickel alloys. It replaced SANS 9956-3 of 1995.^[3]

The record of the test weld, with how it was made and its NDT and mechanical test results, is what proves the WPS. ASME calls it the PQR, and ISO 15607, the ISO general rules for welding procedures, calls it the WPQR.^[7][8]

A WPS covers the method, not the welder. Each welder who welds to it needs a qualification of their own, called a code in South Africa: see coded welders.^[7]

Four documents go together on qualified welding. The first three belong to the fabricator's procedure; the fourth belongs to each welder.^[7][3]

Sources:^{[7][8][3][2][5]}

Mainly on two kinds of work: pressure equipment, and steelwork built to a welding code. On pressure equipment, a weld repair is a repair in law: the Pressure Equipment Regulations, 2009 define a repair as "restoration to original standard by the application of heat or welding to any pressure equipment" (regulation 1), and they apply to equipment with a design pressure of 50 kPa or more (regulation 2(1)).^[1][6]

The user of the equipment has duties of its own when it orders a repair: to give the repairer or modifier "comprehensive information of the operating or intended operating conditions of the pressure equipment, including the characteristics of the fluid and operating parameters of other connected pressure equipment, where reasonably practicable" (regulation 6(2)(a)).^[1]

The user must also ensure that the equipment has a certificate from the repairer or modifier, with an approved inspection authority's signature when required, certifying the work was done to the relevant health and safety standard (regulation 6(2)(c)).^[1]

For an item built to a section of the ASME Boiler and Pressure Vessel Code (BPVC), the welding procedures are qualified to BPVC Section IX, which ASME describes as containing "rules relating to the qualification of welding, brazing, and fusing procedures as required by other BPVC sections".^[5]

For structural steelwork, SANS 2001-CS1:2017 covers steelwork for buildings and other structures, excluding bridges, offshore structures, mobile equipment such as cranes, mine shaft steelwork and mining conveyances. Its text is sold, not published free: ask the project's engineer which welding standard and procedure qualification the specification calls for.^[4]

Where a specification calls up AWS D1.1, the Structural Welding Code: Steel, that code covers the welding requirements for any type of welded structure made from the commonly used carbon and low-alloy constructional steels.^[6]

Usually by a procedure test. TWI describes the ISO 15614 route like this: the manufacturer drafts a pWPS; one of its competent welders welds a test piece to it; the test piece is examined and tested and the results recorded; and if the examiner approves the record, it is used to finalise one or more WPSs for production.^[7]

The test piece goes through non-destructive and destructive tests. In South Africa, SAIW's materials laboratory offers weld procedure qualification testing. Its SANAS accreditation to ISO 17025 covers the tensile, bend, impact, hardness, macro and fracture tests; the radiographic, magnetic particle, penetrant and visual testing it also lists is not accredited.^[10]

Which tests a given procedure needs, and the ranges it then qualifies, are set by the qualification standard and by the application standard or contract. Those texts are sold, not published free, so ask the fabricator which standard and edition its test followed.^[7][3]

A procedure test is not the only route. TWI notes that, where the application standard or contract allows, a WPS can be qualified on previous welding experience (ISO 15611), tested welding consumables (ISO 15610) or a standard welding procedure (ISO 15612), and that AWS D1.1 allows prequalified procedures within the limits the code sets.^[7][8]

Compare its qualified ranges with your joints, before the first production weld. A WPS holds only within the ranges its test qualified: a change in an essential variable, which TWI lists as including material type, welding process, thickness range and sometimes welding position, invalidates the procedure and needs a new test.^[7]

Compare these points on each WPS with the job:^[7]

• the standard and edition it was qualified to, against the one your contract or construction code names;^[7][3]
• the PQR or WPQR it rests on, with that record's test reports and approval;^[7]
• the welding process, material type and thickness range, against your drawings;^[7]
• the welding positions, against where the welds sit on site;^[7]
• the filler material, heat input and any post-weld heat treatment, against the specification;^[9]
• the welders named for the job, each coded within the WPS's ranges.^[7]

SAIW's technical services price list, last updated in December 2025, gives these lines under the heading "Welding Procedure Specifications": R19,144 for an ISO 15614-1 butt weld, R18,471 for an ASME IX or AWS D1.1 butt weld and R13,865 for a fillet weld under any standard. The page does not say what each price covers or whether VAT is included.^[9]

SAIW's laboratory price list, also updated in December 2025 and exclusive of VAT, prices the tests one by one: for example R723 for a tensile test on a specimen under 25 mm thick, R416 for a bend test on a specimen under 10 mm thick, R832 for a set of three impact tests at room temperature, R832 for a weld hardness traverse and R653 for a macro examination with photograph.^[10]

Impact tests cost more at lower temperatures: on the same December 2025 list, exclusive of VAT, a set of three is R1,037 at 0°C or below but above -100°C, and R1,441 below -100°C, so state any impact test temperature the design calls for in the request.^[10]

A new test is needed where none of the fabricator's qualified WPSs covers the job, so ask which of its existing WPSs it will use.^[7]