Arc Welding - Welder approval and procedure qualification in accordance with European Standards

Network Rail have specified that track welders and welding procedures will have to be approved/qualified in accordance with European Standards by April 2005. This article sets out the reasons for the requirement.

Network Rail Company Standard RT/CE/S/132, specifies that in future welders are to be approved in accordance with BS EN 287 and welding procedures are to be qualified in accordance with BS EN 288 (pr EN ISO 15614). It has been claimed by some that the new requirement is 'over the top' and that we are unnecessarily raising the standards for what is after all welding of rails, which is only a semi-skilled job.

So, just why is Network Rail imposing this requirement?

I totally disagree with the assertion that rail welding is a semi-skilled job. Welding is welding and if we get it wrong, we have the potential for a major disaster. What is considered best practice for the UK fabrication industry has to be implemented here. If a derailment were to occur, the first question asked by the welding expert at any subsequent enquiry would be, 'were the procedures qualified?'. If Network Rail were to adopt different practices to the UK fabrication industry, people would want to know why.

Contractors have been exercising 'grandfather rights' since privatisation based on former BR procedures. However, most of these were never formally approved. When I say formally approved, I am referring to mechanical testing in accordance with British/European Standards. Work was often carried out at BR Research in Derby, when consumables and materials were often evaluated for weldability and although limited mechanical testing was usually carried out, this was compensated for by extensive site trials which took place to understand the behaviour of new materials under traffic. 'Ha!', I hear you say, 'but we have never had any problems to date'. This is correct, but repair welds fail from time to time, occasionally resulting in complete failure of the rail, and my comment in the paragraph above still applies.

There are currently a number of working groups producing European (CEN) Standards for welding. These include flashbutt, aluminothermic and arc welding. Work on the arc welding Standard is well advanced and when this document is eventually implemented, Network Rail will have no choice but to apply it, as it will supersede any National and/or Company Standards that may be in use.

What needs to be done?

Network Rail need to implement Standards that are commensurate with current working practices, ie qualify procedures that conform to recognised Standards. Qualifying welding procedures, welder approvals and adopting working practices in accordance with welding procedure specifications would bring rail into line with the UK fabrication industry.

Welding Procedure Qualification

The requirement for welding procedure qualification of steels, can be found in BS EN 288-3 (pr EN ISO 15614-1). This part of the series of standards could rightly be claimed to be 'over the top' as it involves numerous mechanical tests which are related to the welding of plate and pipe butt and fillet welds and, as a result, is not considered applicable for the welding of rails.

BS EN 288-8 (pr EN ISO 15613) however, is probably the most suitable part and deals with pre-production testing. This part of the series of standards, is used when there is no suitable joint configuration for testing purposes and instead a joint can be substituted that is representative with the work that is carried out in production.

The mechanical testing required to qualify the procedure is also more simplified because of the shape and form of the test-piece (ie excavated railhead). Although testing is still carried out in accordance with the relevant part of BS EN 288-3 (in terms of how it is carried out), it is possible to approve a procedure by carrying out visual inspection, volumetric inspection (radiography, ultrasonics), surface crack detection, hardness testing and examination of macro-sections.

Welder Approvals

As discussed earlier, there have been claims that Network Rail are trying to raise the standards for rail welding. Once the procedure has been approved, the welder will not be asked to do anything differently from what they are currently doing, ie welding a rail sample with a portion of the railhead either ground or machined to simulate a railhead defect. The only difference is that the weld is left in the as-welded condition in order for the weld quality to be visually assessed prior to surface crack detection followed by sectioning for macro-examination.

For this reason, I do not believe we are specifying an onerous testing regime and the welders will have no difficulty in achieving approval.

Validity and prolongation of approvals

Welders who are involved in qualifying the weld procedures, are automatically approved assuming the procedure passes the tests.

Welders who pass the welder approval test(s) are approved initially for two years. Their approvals remain valid provided that they are welding within the extent of their approvals on a regular basis and that their certificates are signed at six-monthly intervals by a responsible person to confirm this. Approvals can be prolonged for a further period of two years, provided that documentary evidence is available (usually in the form of radiographs or ultrasonic test reports) that volumetric testing has been carried out. As plain rail repairs are subject to ultrasonic testing, it would be possible for welders to have their approvals prolonged.

Are there any additional requirements?

Welding is only a part of the process of repairs to plain rails and switch andcrossings. There is also the requirement for powered plant proficiency and final profile grinding which, although an important part of the overall requirement for arc welding, is outside the scope of the above tests. These additional requirements would have to be dealt with separately.

Implementation?

April 2005 is the date currently specified for compliance. As Network Rail are now bringing maintenance back in-house, we will have to manage the process ourselves. Once complete however, track welding will finally have been dragged kicking and screaming into the 21^st Century!

Bill Mosley
Senior Welding Engineer
Network Rail HQ Track Engineering