Subscribe to our newsletter to receive the latest news and events from TWI:

Subscribe >
Skip to content

Welding procedure

   

Job Knowledge 39

AC TIG welding of aluminium cryogenic pressure vessel Courtesy of Air Products PLC
AC TIG welding of aluminium cryogenic pressure vessel Courtesy of Air Products PLC

For a given application, the main way of ensuring adequate weld quality is to specify the procedure and the skill level of the welding operator. Here, the alternative routes for welding procedure approval are described together with the requirements for welder or welding operator approval.

Routes to welding procedure approval

The key document is the Welding Procedure Specification (WPS) which details the welding variables to be used to ensure a welded joint will achieve the specified levels of weld quality and mechanical properties.

The WPS is supported by a number of documents (eg, a record of how the weld was made, NDE, mechanical test results) which together comprise a welding approval record termed the WPAR (BS EN ISO 15614) or PQR (ASME).

In both the European and ASME standards, there are a number of 'essential variables' specified which, if changed, may affect either weld quality or mechanical properties. Therefore, a change in any of the essentials will invalidate the welding procedure and will require a new approval test to be carried out. The essential variables are detailed in the relevant specification but include material type, welding process, thickness range and sometimes welding position.

Fig 1. Stages in welding procedure and welder approval

The route followed to produce a WPS in BS EN ISO 15614 and the responsibilities of the manufacturer and the Examiner/Examining Body are shown in Fig.1.

The most common method of gaining approval is to carry out an approval test as described in BS EN ISO 15614-1 (steels) and 15614-2 (aluminium and its alloys). The manufacturer initially drafts a preliminary welding procedure (pWPS) which is used by one of the manufacturer's competent welders to prove that it is capable of producing a welded joint to the specified levels of weld quality and mechanical properties. The welding procedure approval record (WPAR) is a record of this weld. If the WPAR is approved by the Examiner, it is used to finalise one or more WPSs which is the basis for the Work Instructions given to the welder.

It is noteworthy that the welder carrying out a satisfactory welding procedure approval test is approved for the appropriate range of approval given in the relevant standard (BS EN ISO 9606, ASME IX or AWS D1.1).

The following options for procedure approval are also possible:

  • Welding procedure test (BS EN ISO 15614)
  • Approved welding consumable (BS EN ISO 15610)
  • Previous welding experience (BS EN ISO 15611)
  • Standard welding procedure (BS EN ISO 15612)
  • Pre-production welding test (BS EN ISO 15613)

The conventional procedure test (as specified in BS EN ISO 15614) does not always need to be carried out to gain approval. But alternative methods have certain limits of application regarding, for example, welding processes, materials and consumables as specified in the appropriate application standard or contract agreement.

The welding procedure test method of approval is often a mandatory requirement of the Application Standard. If not, the contracting parties can agree to use one of the alternative methods. For example, a welding procedure specification can be approved in accordance with the requirements of BS EN ISO 15611 (previous experience) on condition that the manufacturer can prove, with appropriate documentation, that the type of joint has previously been welded satisfactorily.

The American standard, ASME IX requires a welding procedure test (PQR) but AWS D1.1 will allow the use of pre-qualified procedures within the limits detailed in the specification.

Welder approval

The welder approval test is carried out to demonstrate that the welder has the necessary skill to produce a satisfactory weld under the conditions used in production as detailed in the approved WPS or Work Instruction. As a general rule, the test piece approves the welder not only for the conditions used in the test but also for all joints which are considered easier to weld.

As the welder's approval test is carried out on a test piece which is representative of the joint to be welded, it is independent of the type of construction. The precise conditions, called 'essential variables', must be specified in the approval test, eg material type, welding process, joint type, dimensions and welding position. The extent of approval is not necessarily restricted to the conditions used for the test but covers a group of similar materials or a range of situations which are considered easier to weld.

It is important to note that a number of Amendments and Corrigenda have now been issued which affect the range of approval (see list of Relevant Standards).

In BS EN ISO 9606, the certificate of approval testing is issued under the sole responsibility of the Examiner/Examining Body. The welder approval certificate remains valid subject to the requirements of the application standard. In BS EN ISO 9606, it can be confirmed at six monthly intervals by the employer/welding coordinator/examiner or examining body for up to three years, depending on the route selected (see next paragraph), provided the welder has been successfully welding within the range of qualification of his/her certificate.

Revalidation of the welder’s qualification can be carried out according to one of these three routes:

a) The welder shall be retested every 3 years.

b) Every 2 years, two welds made during the last 6 months of the validity period shall be tested by radiographic or ultrasonic testing or destructive testing and shall be recorded.

c) A welder's qualifications for any certificate shall be valid as long as it is confirmed as described above and provided all the following conditions are fulfilled:

  • The welder is working for the same manufacturer for whom he or she qualified, and who is responsible for the manufacture of the product;
  • The manufacturer's quality programme has been verified in accordance with ISO 3834-2 or ISO 3834-3;
  • The manufacturer has documented that the welder has produced welds of acceptable quality based on application standards; the welds examined shall confirm the following conditions: welding position(s), weld type (FW, BW), material backing (mb) or no material backing (nb).

American standards have similar requirements although the extent of approval of the welding variables are different to those of BS EN ISO 9606. From the 2015 edition of ASME IX, a new nonmandatory appendix titled: “NONMANDATORY APPENDIX L WELDERS AND WELDING OPERATORS QUALIFIED UNDER ISO 9606-1:2012 AND ISO 14732-2013”, describes conditions under which an organization that is testing welders or welding operators under the above ISO standards to also certify that those welders and welding operators are qualified to Section IX.

Welding operator approval

When required by the contract or application standard, the welding operators responsible for setting up and/or adjustment of fully mechanised and automatic equipment must be approved but the personnel operating the equipment do not need approval. In clarifying the term 'welding operator', personnel who are using the equipment (loading and unloading robotic equipment or operating a resistance welding machine) do not require approval.

As specified in BS EN ISO 14732, "Welding personnel — Qualification testing of welding operators and weld setters for mechanized and automatic welding of metallic materials" can be based on:

a) qualification based on a welding procedure test in accordance with the relevant part of ISO 15614;

b) qualification based on a pre-production welding test in accordance with ISO 15613;

c) qualification based on a test piece in accordance with the relevant part of ISO 9606;

d) qualification based on a production test or production sample test.

It should be noted that the methods must be supplemented by a functional test appropriate to the welding unit. However, a test of knowledge relating to welding technology which is the equivalent of 'Job knowledge for welders' in BS EN ISO 9606 is recommended but not mandatory.

Revalidation of the welding operator approval is generally in accordance with the requirements of BS EN ISO 9606, except that route (a) requires retesting every six years and  route (b) requires revalidation based on evidence every three years.

When working to ASME IX, operators for both mechanised and automatic welding equipment require approval. The essential variables are different to those in welder approval. From the 2015 edition of ASME IX, a new nonmandatory appendix titled: “NONMANDATORY APPENDIX L WELDERS AND WELDING OPERATORS QUALIFIED UNDER ISO 9606-1:2012 AND ISO 14732-2013”, describes conditions under which an  organization that is testing welders or welding operators under the above ISO standards to also certify that those welders and welding operators are qualified to Section IX.

Relevant Standards

BS EN ISO 15614
Specification and qualification of welding procedures for metallic materials - Welding Procedure test. Part 1 Arc and gas welding of steels and arc welding of nickel and nickel alloys.

  • Part 2: Arc welding of aluminium and its alloys
  • Part 3: Fusion and pressure welding of non-alloyed and low-alloyed cast irons
  • Part 4: Finishing welding of aluminium castings
  • Part 5: Arc welding of titanium, zirconium and their alloys
  • Part 6: Arc and gas welding of copper and its alloys
  • Part 7: Overlay welding
  • Part 8: Welding of tubes to tube-plate joints
  • Part 9: Underwater hyperbaric wet welding
  • Part 10: Hyperbaric dry welding
  • Part 11: Electron and laser beam welding
  • Part 12: Spot, seam and projection welding
  • Part 13: Resistance butt and flash welding 

BS EN ISO 9606-1: 2013
Qualification test of welders - fusion welding. Part 1: Steels

BS EN ISO 9606-2: 2004
Qualification test of welders - fusion welding. Part 2: Aluminium and aluminium alloys

BS EN ISO 15612: 2004
Specification and qualification of welding procedures for metallic materials - Qualification by adoption of a standard welding procedure.

BS EN ISO 15610: 2003
Specification and qualification of welding procedures for metallic materials - Qualification based on tested welding consumables.

BS EN ISO 15611: 2003
Specification and qualification of welding procedures for metallic materials - Qualification based on previous welding experience.

BS EN ISO 14732:2013
Welding personnel — Qualification testing of welding operators and weld setters for mechanized and automatic welding of metallic materials

Bill Lucas prepared the information in this article in collaboration with Oliver Smith, John Weston and Gene Mathers.

For further information on WPSs see Welding Procedures

For more information and/or technical enquiries please contact us.

For more information please email:


contactus@twi.co.uk