25.11.08
Light rail overhead lines - the Malico solution
The Malico solution: self insulating synthetic cable and self insulating composite material mastarms with corrosion withstanding metallic components
The Malico factory is well known principally for its extensive research and development programme related to the use of self insulating synthetic cable in the building of tramway and trolleybus overhead lines.
Various types of synthetic cable can be sourced from the industry. Some are made of polyester fibres and others are of Kevlar fibres. A quarter of a century of experience has now shown that polyester fibres are far better suited to overhead line applications than Kevlar ones. Kevlar lines are too susceptible to degradation in the corrosive atmosphere of polluted cities or near the seaside. On the other hand, polyester fibres appear to be far more stable in that kind of environment.
Malico technology is based exclusively on three type A parafil ropes manufactured by Linear Composites Ltd in a mill nearby Keighley, west Yorkshire. All the spanwires, pull-over, mastarm ties, contact wire anchoring guys and headspans necessary for the hanging of the contact wires can be built using 7mm, 11mm and 13.5mm diameter type A parafil ropes. If necessary, 17mm type A parafil can be considered in the case of compensation at a high mechanical tension.
Over the last ten years, Malico have helped completely realize insulator-free overhead lines by replacing the traditional metallic tubes used in the mastarms, through composite material solid rods manufactured by companies in Germany, the Czech Republic and Norway. These rods have normally a diameter of 55mm and are made of fibreglass and of polyester resin.
The Malico factory is highly specialized in manufacturing fittings which allow the building of an overhead line with synthetic cable and with composite material mastarms. Almost all of these mechanical components are made from corrosion resistant materials: copper alloys, aluminium alloys, stainless steel or UV-protected polyamide 6 reinforced with fibreglass meshs.
The development of the Malico solution in the Rhonalps in 1980
Early research into the application of self insulating synthetic cables to the suspension of contact wires occurred in 1974 in Milan, Italy. One year later the Grenoble trolleybus network tested parafil ropes in its overhead lines. The Malico Company began designing components through collaboration with the Grenoble mass transit network in 1980. In 1981, the la Mure railway, an independent mountain railway 12 miles south of Grenoble, began investigating the use of parafil in the renovation of its tramway-like overhead line.
As this railway uses a 2,700 volt DC electrification scheme, the la Mure railway proved to be a perfect test bed for the development of a brand new type of overhead line which could be used not only on tramway lines, but also on secondary railway lines when the speed did not exceed 50 miles/hour. The first application of all these exciting developments materialized in 1987 with the opening of the Grenoble light rail transit.
Twenty one years ago many people expressed doubts about the durability of the Malico designed overhead line. But despite this, the electric line does not need any maintenance, except in the case of a shock by a lorry. So the Rhonalps really were the cradle of overhead lines built with self insulating synthetic ropes.
Applications of the Malico solution in the UK in the 1990s
The design of the Grenoble light rail overhead line inspired two English schemes between 1991 and 1995 - the city centre section of the Manchester Metrolink and the Sheffield Supertram. Both rely heavily on the use of spanwires, mastarm ties, delta suspensions and pull-over made of type A parafil with Malico manufactured terminals, hangers and anchoring clamps.
Some curves on the Don Valley tramway line nearby Sheffield are among the most beautiful overhead line sections ever built in the world thanks to the late Alan Seddon, catenary engineer at that time with Balfour Beatty.
In the late nineties, Malico was associated with the Midland Metro and the Croydon schemes. Unfortunately, thanks to the choice of Kevlar fibres instead of polyester fibres in the synthetic ropes, the resulting overhead lines were more expensive to build and trickier to maintain.
The success of the Malico solution in 21st century coastal Europe
If you analyse the cities where a tramway overhead line has been built with Malico technology over the last twenty years, a pattern emerges. Most of these areas are located on or nearby the seaside. This is because the synthetic polyester ropes and the Malico bronze and aluminium alloy components withstand a marine environment better than steel cable and fittings.
10 examples in four different seaside areas are: Tallinn, Riga and Liepaja on the Baltic, Oslo on the North Sea, Bilbao, Porto and Lisbon on the Atlantic and Marseille, Valencia and Messina on the Mediterranean, along with applications on island locations such as the Canary Isles (Tenerife tramway) or Mallorca (Palma-Soller railway). A strange fate for a technology designed for use in the snowy mountains of the western Alps!
The Malico solution for light railway DC catenaries
For the last ten years Brecknell Willis and Malico have been demonstrating on the Midland Metro that it is possible to operate a light rail overhead simple line – that means without catenary cable – up to speeds around 50 miles/hour. Nevertheless, some customers prefer to switch to catenaries at lower speeds for various reasons from current capacity to pole spacing.
Malico is also able to offer solutions in this case with its headspans made of synthetic rope or its cantilevers combining polyester rope and composite material rods. Tests are now under way on various Spanish Railways (Guadarrama railway, Bilbao Metro and Eusko Trenbideak) and on the Latvian railways nearby Riga.
During the next few years, new light rail lines will be built in Ireland, Scotland and England in Manchester, Edinburgh, Dublin and also in Galway. Malico hopes to again be part of these exciting developments.
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