Rail joints have always been a major cause of maintenance on rail track. Discontinuity of the track running surface produces dynamic impact loads causing greater stress on the ballast and subgrade which accelerates track wear and failure. The introduction of continuous welded rail has improved the geometric stability of the track. Using the butt welding process has further reduced rail surface discontinuities due to its limited change to the metallurgical character of the rail, producing a very high quality weld.
The Plasser & Theurer APT 1500 RA has many improved features including higher clamping forces, shorter welding durations, automatic alignment of the rails, the ability to perform closure welds and it is the only machine that fully complies with the European welding standard, EN14587-2 published in 2009.
Less costly machines are still available for lighter applications such as short rails and non-closure welding. Two of these machines (the K 355 APT) have been successfully operating in South Africa for almost two decades on construction and maintenance projects, welding all types of rails in-situ and in depots.