Repair & Surfacing

Maintenance welding, including repairs and rebuilding of plain line, switches and crossings is carried out using manual metal arc welding or using self shielded flux cored semi automatic welding. Crossings are repaired to make good the batter and cracking caused by traffic, plain lines are repaired to make good damage caused by wheel slip and manufacturing faults.

We can provide a team of welders certificated to Network Rail requirements for undertaking the repair welding of plain line and crossings, using the approved Manaual Metal Arc and Semi Automatic Self shielded Arc methods.

In addition, the Submerged Arc Welding repair or resurfacing of embedded rails has been standard practice on many Metro and Tram rail systems throughout Europe for many years. The method, developed by the Goldschmidt Thermit Group, uses the submerged arc welding process with solid wires specifically formulated to produce a deposit with enhanced wear or noise reducing properties. The process is used with automatic welding equipment attached to a rail mounted tractor, with tracking devices to enable a continuous weld deposit to be made.

Repair or resurfacing by welding raises specific issues when applied to embedded rails. For some of the older tram systems the type and grade of rail that has been installed is often uncertain, and some of the sealing / grouting materials can be damaged or produce toxic fume when subject to the high temperatures generated during the welding operation. In addition there can be operational restrictions - proximity of the general public, access and track possession time.

As a result, the submerged arc welding process offers several benefits when applied to surfacing rails:

• The process is a high heat input welding method - avoiding the need for preheating or post weld heat treatment
• The process has a high deposition rate enabling large repairs in a short timescale
• The process produces an intrinsically high quality weld deposit - free from porosity and inclusions
• As the welding arc is protected by the flux powder there are no environmental restrictions. Work piece preparation is minimized.

The rate at which a rail profile may be restored will depend upon the extent of the repair and specific site conditions:

3 mm full width 3mm deep head repair	27 deg side wear
8 - 12 deposits - 5-8 m / 5 hr shift	2 - 5 layers - 18-16 m / 5 hr shift

Typical applications for the process include:

• Repair of damaged track
• Repair/ rebuilding worn running surfaces and flanges
• Control of corrugations & noise
• Increased wear resistance
• Repair/reprofiling of switches & Crossings

Thermit Welding have also been involved in producing a technique for welding embedded rails that have a harder grade, typically 900.

The metallurgical problems encountered have resulted in the development of a technique that allows for a low temperature pre-heat, that will not cause damage to the jointing compound that typically adjoins embedded rail.

Coupled with state of the art cored filler wires that can be used in an open-arc system, the resulting weld will allow for precise weld build-up on switch-blades, gauge corners and head repairs.

The equipment will allow for quick deployment, maximizing the time of engineering possessions.