The single use cruciblerail welding

THERMITREXImproves

Until now, the Thermit welding system has used a conventional multi component crucible, which could be reused a number of times. In this process, a two-part mould would be clamped around the gap between the two rail ends. The rail ends would then be heated to 800°C using either propane or a petrol/air mix. A steel crucible would then be swung into position over the mould, and the Thermit welding material or ‘portion’ placed inside it. The portion would then be ignited. The exothermic reaction would melt a plug in the bottom of the crucible, and the molten contents would then flow into the mould filling the gap between the two rails and effectively welding them together.

Thermitrex, the leading South African supplier of Thermit welding kits, related equipment and consumables, is now able to offer a greater refinement to its already-proven system for welding railway track joints together.

The conventional Thermit welding system has been in use for more than 100 years. Early in the 20th century, Professor Heinz Goldschmidt demonstrated the reduction of metal oxides by using aluminium powder. This was the basis of the Thermit welding system. By 1928, the Thermit rail welding process was adopted as the standard for the German State Railways.

Since then, the Goldschmidt-Thermit Group, which is today Thermitrex’s holding company, has invested substantially in research and design, to ensure that its customers receive the most effective rail welding solutions.

While this process worked well, there were certain disadvantages. The robust steel crucible was heavy and in inaccessible sections of track, at least two people would be needed to carry the weighty crucible to the site.

The conventional crucible is made to be used as many as forty times. Because of this, this unit is constructed of four components, any of which could be damaged during the high temperatures generated by the exothermic reaction. If any of the components were damaged, or simply went missing during moves from one site to another, it would not be possible to continue with rail repairs.

After each use, the crucible needed to be cleaned out carefully to ensure the effectiveness of the next weld. Where crews are unsupervised, or where the need for pre-cleaning the crucible is not fully understood, the resulting welds could be sub-standard.

Although all rail welds are inspected using X-rays, this process might only happen some days or even weeks later. During this period, as a precaution, the newly welded joint is protected by a clamping device known as a ‘joggle plate’. In South Africa, these have been stolen for their scrap metal value, leaving the joint unprotected. Should a weld fail while a train is passing over it, a calamity could ensue.

The downtime while the track is out of service could run into many hundreds of thousands of rands.

The amount of rework needed when using a single-use crucible would be considerably reduced.

The single-use crucible is much lighter than the conventional crucible and requires only one person to carry it to site. The reduction in labour needed will lead to substantial cost reductions. In addition, weighty crucible stand, crucible extension and adaptor assembly are no longer needed.

The single-use crucible reduces the time taken to carry out a weld by a considerable margin.

The largest factor in favour of the single-use crucible is that it reduces the risk of human error. The single-use crucible is made from a bonded refractory material, which is contained in a five litre steel canister. The automatic self-tapping thimble is incorporated during manufacture. The single-use crucible requires no preheating or drying before it can be used.

When preheating of the rail ends has been completed, the single-use crucible is placed on the mould, which has four lugs into which the canister fits. A standard Thermit portion is placed in the crucible and ignited for the weld to proceed.

Now Thermitrex is able to offer its South African customers the latest innovation from Goldschmidt-Thermit – the single-use Thermitrex crucible.

THERMITREX Brings Improved Rail Welding

With the conventional crucible, once the weld had been completed, the waste products from the procedure were usually buried next to the track.

This waste consists of the welding slag and the excess steel sheared from the weld during the re-profiling of the track. On occasions this unsightly waste was left lying next to the track, as the crews had not a convenient way of returning

this material to a central depot.

With the single-use crucible, the used canister makes

a handy container in which to return all waste material. The five kilograms of waste steel and four kilograms slag from a single weld have value and can be recycled, indirectly contributing to job creation.

The Goldschmidt-Thermit group and Thermitrex have a commitment to maintaining the highest environmental standards, as it witnessed by their ISO 9001:2000 accreditation. The recycling of waste is very much in line with this philosophy.

In terms of cost, the single-use crucible is slightly more expensive than the conventional unit. However, the numerous benefits of the new system will give its users an increased return, which will outweigh the minor cash outlay many times over.

As the single-use crucible reduces the steps involved in the welding process. Thus training of exothermic rail welders is considerably simplified. Thermitrex offers fully accredited training and support in the Thermit welding processes, after which a formal certificate of competence is issued.

Safety is also a key concern of Thermitrex and its parent company. The single-use crucible reduces the amount of sparks that are released during welding, diminishing the possibility of a member of the crew being injured. The smoke from the reaction is also reduced which is a major benefit when joining rails in tunnels or other confined areas.

Contact:Thermitrex (PTY) Ltd Tel: +27 (0)11 914 2540Fax: +27 (0)11 914 4627

Email: clloyd@thermitrex.co.zaWebsite: www.thermitrex.co.za

PO Box 6070,Dunswart,Johannesburg,GautengSouth Africa1508