Report of 13th technical seminar:

Rail welding - challenges for the future

An unprecedented level of praise was received by the speakers following the recent IoRW Technical Seminar held at the Derby Conference Centre.

Explosive depth hardening (EDH) of crossings was the first subject of the day with Mike Westoby of Balfour Beatty Rail explaining the advantages in terms of reduced maintenance and increased service life. EDH is used in a number of railways outside the UK, notably in the USA and India. The technique involves detonating an explosive sheet (see photo) in order to create a shock wave that work hardens the surfaces of the crossing. Environmental issues have prevented its use in the UK, although it is possible to get the EDH work done in the USA and then ship the crossings back to the UK. However, the UK rail community has so far been unwilling to meet the cost of this. There is a possibility that EDH could be done in future in the UK by enclosing the process in a special chamber.

Bob Hervey of GrantWeld highlighted the special problems with installing and maintaining grooved rails such as those used for tramways and metro systems. Aluminothermic welding is used extensively and has the flexibility to deal with a variety of sections. Enclosed arc welding is also used for both installation and maintenance. Particular mention was made of the restoration of the gauge corners using submerged arc welding, using fully austenitic filler metal, followed by profile grinding.

Alignment of rails prior to welding has received considerable attention over the years and Ian Moore of Vital Rail presented a new technique, recently approved by Network Rail, called the Rail Setter System. This is the only system that can be applied to both sleeper supported rails and to rails for which support is not available. Alignment is achieved in the vertical, lateral and horizontal directions through a novel mechanical arrangement of clamps and screws. This avoids the use of wedges and hammers which has, and still does, result in injuries to rail workers. The speaker also advocated the use of the Rail Setter as part of a 'production line' system in order to increase rail welding productivity.

Grinding and re-profiling rails during their service life has a beneficial effect on endurance but the process can be slow and difficult to apply at a time when track possession times are reducing. Marcel Taubert of Stahlberg Roensch explained the use of high speed grinding (HSG) as a completely new preventative grinding strategy. The grinding is accomplished at a speed of 80 km/h and 50 microns of material is removed uniformly across the crown profile of the rail head in a single pass. It does not re-profile the rail: it copies the existing profile while removing the fatigued surface layer. The high speed means that it can be carried out in normal traffic schedules. Data on the effect of frequent (HSG) treatment on rail life shows a dramatic increase in endurance compared to conventional, less frequent, maintenance grinding. The system is approved in Germany and examples of its application were presented.

Bill Mosley of Network Rail outlined the properties and weldability of new types of rail which are currently appearing in track in the UK. 400MHH (micro-alloyed head hardened) rail is currently being trialled in the UK. This material has an ultra-fine pearlitic structure which leads to significantly higher harness and strength than conventional rail. Welding techniques covering flash butt, aluminothermic and arc welding have been developed for manufacture, installation and repair. A further premium rail steel, Corus HP2, is also being considered. This is designed to provide resistance to wear and rolling contact fatigue without the large addition to the alloying elements and without the need to generate high hardness.

Mr Mosley went on to describe three types of coated rail. Soginox Rail has a thin layer (0.5 - 0.8 mm) of austenitic stainless steel rolled onto the surface. Flash butt and aluminothermic welding can be used and the rail is currently under trial in the UK. Alphatek coated rail has an aluminium coating on the web and foot (not the head) and is used in the track sections where corrosion is a problem. Both flash butt and aluminothermic welding can be used but the coating must be removed from the vicinity of the weld in the latter process. CorProTech rail is similar to Alphatek except that the coating is glass flake epoxy. Again, special care is needed when welding, especially with the aluminothermic process.

In order to reach Network Rail's goal of a '7 day railway' improved efficiency is required in the replacement of switches and crossings. These efficiencies include both the utilisation of manpower and the use of modular units, and were outlined in a presentation by Dylan Edwards of Network Rail.

Better planning has already reduced installation time from 54 hours to 37 hours (the 'early deployment' phase) and three further step changes are in prospect which gradually introduce the modular switches and crossing units. The goal is to reduce installation time to 8 hours during mid week possession which is compatible with the '7 day railway'. The presentation included details of the new equipment and procedures that were in prospect, and the speaker urged the audience to embrace enthusiastically the new approach.

The final presentation was by Bob Sawdon of Balfour Beatty Rail Technologies on their high productivity welding (HPW) initiative. This initiative had also arisen from the '7 day railway' goal and was similar to that described earlier by Ian Moore. The main features of it are: to maximise the effective use of all available time on the worksite by minimising wasted effort; to increase productivity through detailed planning; to facilitate parallel tasks; and to ensure the site is prepared for welding activity. Trials of the new procedures have been conducted and have resulted in significant increases in the number of welds completed in a given period of time.

With acknowlegements to Jon Hawthorn, BOC, for chairing the event and to Bob Sawdon, BBRT, for developing the programme.

Tim Jessop
Executive Officer