The Thermit Head Repair

Rail head defects in plain line include small isolated flaws which have been detected either by visual inspection or by the Ultrasonic Test Vehicles (UTU). Currently, these defects, when repaired, are done so by arc welding, which is both time consuming and may introduce other defects such as slag inclusions and stop/start porosity. With the support of Network Rail, Thermit Welding (GB) Ltd has developed an alumino-thermic weld repair process for the repair of these defects.

Particular attention has been paid to minimizing costs and delivery issues by wherever possible aligning the method with equipment, consumables, and welding practice used for the conventional SkV-E welding process. Therefore the Thermit HR weld has been developed to incorporate:

• Defect removal by flame cutting and grinding
• Conventional low pressure preheating - same parameters as standard SkV-E
• Single Use Crucible
• Standard Network Rail Approved Thermit Portions
• Normal Thermit Welding, Trimming and Profile grinding practice

The area to be repaired is excavated using a purpose designed flame cutting template and torch, then surface ground to prepare the surface for N.D.E. The Thermit Moulds are fitted and sealed to the rail head using conventional welding practice and equipment, and the excavated area is preheated using a special oxy propane preheating appliance. The method incorporates the new single use crucible and the Thermit Steel is cast directly into the excavation. After cooling the excess material is removed using a modified hydraulic shear and the residual material subsequently ground to restore the rail to the original profile.

The process has undergone substantial testing and now has Network Rail approval for a trial period.

View Product Development