BSI publishes BS 8548:2017 Guidance for arc welding of reinforcing steel

The British Standards Institute (BSI) published this new standard in January 2017. There has recently been a significant growth in the specification of pre-assembled welded fabrications. This standard aims to clarify the requirements of BS EN ISO 17660-1 and BS EN ISO 17660-2, providing suitable guidance for the arc welding of carbon steel reinforcing bars produced in accordance with BS 4449 and BS 4482.

This standard gives general guidance for the satisfactory production and control of the welding of steel reinforcement in accordance with the requirements of BS EN 1011-2, BS EN ISO 17660-1 and BS EN ISO 17660-2. In order to aid the specifier and manufacturer using these standards, additional informative guidance has been added, especially regarding the steps to be taken to avoid hydrogen cracking.

The procedures and test requirements contained in this standard apply to the assessment of the weld, and its potential effect on the welded reinforcement, but do not take into account design criteria, e.g. fatigue, that are the responsibility of the relevant application standard.

The preferred method of control of welding is under factory conditions. Construction site welding, if conducted, should be carried out under similar controlled conditions.

Reinforcing steel bars manufactured in accordance with the requirements of BS 4449 and BS 4482 are produced by a number of differing process routes, typically quenched and self-tempered, cold reduced and to a lesser extent micro-alloyed steel. In addition, the profile of the reinforcement bar is ribbed and as such the welding of steel reinforcement requires a specific level of skill and job knowledge, both for the welder and the organisation exercising control over the whole process, from purchasing of the steel to the eventual supply of the prefabricated item to the customer.

Whilst the specific requirements for the welding of steel reinforcement are set out in BS EN ISO 17660-1 and BS EN ISO 17660-2, this standard gives general guidance for the satisfactory production and control of welding. It also details possible detrimental phenomena which might occur, with advice on how these can be avoided.

The recommendations in this standard are relevant to the metal arc welding processes, which are commonly used for the welding of reinforcing steels, although other welding processes may be used by agreement between the contracting parties.

CARES recommends that when specifying   welding according to ISO17660, purchasers should include the requirements of BS 8548 into the purchase specification. This is achieved by specifying CARES approved manufacturers of pre-assembled welded fabrications as shown below.

CARES has revised our technical requirements covering pre-assembled welded fabrications to align with the requirements of BSENISO17660, and the guidance provided in BS 8548. By specifying CARES approval, purchasers will be able to have confidence that appropriate independent tests have been conducted, and that an independent assessment has been made of the manufacturer’s quality management systemas well as the efficacy of the welding procedures and welder qualifications.

Specification of CARES approved manufacturers of pre-assembled welded fabrications

The suggested wording for inclusion in a specification is as follows:

• Semi-structural / structural welding activities:

"Only firms that have achieved certification to CARES Appendix 12 - Quality and operations assessment schedule for the manufacture of pre-assembled welded fabrications using welded semi-structural and/or structural joints, shall be permitted to bid for or undertake contracts to supply pre-assembled welded fabrications.”

• Tack welding activities:

"Only firms that have achieved certification to CARES Appendix 11 - Quality and operations assessment schedule for the tack welding of reinforcing steel, shall be permitted to bid for or undertake contracts to supply pre-assembled tack welded fabrications.”

Note: Evidence of compliance with the above should be requested for submission with contract bids.

When a CARES approved manufacturer is not specified, there is an additional onus on the purchaser to verify compliance, which may require inspection and testing involving both significant cost, and the potential for delays on site.

CARES list of approved manufacturers

CARES regularly updates the list of approved manufacturers, via the CARES website (www.ukcares.com). This also describes the manufacturer's scope of approval and provides useful contact information. Occasionally, pre-assembled welded fabrication manufacturers have falsely claimed to hold CARES approval because they only use steel from CARES approved sources, and/or have an approval for cutting and bending to BS 8666 / BS 4466. In these cases the pre-assembled welded fabrications supplied by these companies are not covered by CARES approval. If there are any doubts concerning the scope of approval of a manufacturer, then the CARES website should be consulted, www.ukcares.com or alternatively the CARES office can be contacted for verification, +44 1732 450000.