ocal partner and agent for Plasser & Theurer Track, maintenance equipment manufacturer Plasser South Africa (SA), has submitted a tender to provide State-owned rail utility Transnet with three flash butt rail-welding machines, Plasser SA spokesperson Tamsin Louw tells Engineering News.

Plasser submitted the tender at the beginning of last year and is awaiting adjudication.

However, Louw is optimistic that Plasser SA’s tender will be successful, as no other flash butt rail-welding machine in the world complies with the specifications provided in the tender, as far as she is aware.

When creating the specifications, Transnet mostly stuck to the EN14587-2 specification, says Louw.

She highlights Transnet’s requirement that the welding machine be able to perform a closure weld at the final gap between two fixed stretches of rail. This is particularly difficult because the rails must be stretched in order to close the gap while fusing the rail ends, says Louw, adding that this task requires the welding machine to have extremely powerful pulling force.

Plasser’s technology will enable Transnet to remove thousands of substandard and fatigued thermit welds and rail cracks from their network across the country at high production rates and without major disruption to their train services.

The welding machines will also enable Transnet to eliminate the practice of traditional and inferior thermit welding on site during rail replacement programmes. In addition, any length of rail can be welded on site, eliminating the need for welding depots and special rail trains to transport long, welded rails from the depot to site.

EN Specification
Louw notes that, until recently, most mobile flash butt rail-welding machines used similar welding heads. However, in 2009, the new EN14587-2 standard specified additional requirements, and most of the existing welding heads on mobile plant are not fully compliant with these requirements.

The EN requirements include greater geometric accuracy during welding, higher breaking and fatigue strength of the rail line, as well as that rail clamping jaws operate independently from one another. The welding head should also allow for excess upset to be trimmed automatically and all welds must be carried out according to programmed and automatic sequences.

Responding to the new requirements, Plasser SA partner company Plasser & Theurer developed a welding head that not only complies with the EN standard but also boasts additional features that increase the competitiveness of the product, says Louw.

The flash butt welder’s special features include being able to perform closure welds, automatic rail alignment, strong clamping jaws that grip the rails with 3 200 kN using four hydraulic cylinders, electrodes that operate independently from the clamping jaws and the high-frequency 1 000 Hz used for the current supply of the 400 V alternating current generator, Louw explains.

Meanwhile, Plasser SA is also preparing to meet increased demand expected from Transnet. In terms of their market demand strategy, tonnages have increased dramatically and will continue to do so in the next decade and beyond. With increased traffic and subsequent congestion on the lines, more maintenance will be required with shorter maintenance windows.

To tackle this problem, high-speed, continuous action tamping machines such as the Plasser & Theurer 3X are able to tamp three times faster than conventional machines. Such machines are also available as 2X universal derivatives, which are able to tamp open line as well as conduct turnout tamping, says Louw.

In addition, integrating track stabilising is a process of ballast consolidation after tamping. These machines are able to stabilise the track at the same speed of high-speed tamping machines and increase the durability of ballast maintenance by about 30%, says Louw.

She explains that high-speed ballast cleaning machines are able to clean ballast at twice the speed of conventional machines.

Plasser SA currently contracts out about 65 machines to Transnet’s freight rail division, State-owned rail utility the Passenger Rail Agency of South Africa and the mining sector.

Plasser’s equipment covers the whole spectrum of machines used to measure, monitor and analyse the condition of rail infrastructure, as well as to maintain, relay and construct new lines, says Louw. About 700 Plasser SA and subcontractor staff members operate, maintain, support and refurbish the fleet.