Electrification will be one of the big stories covered by the rail engineer over the next few years. Millions will be spent on projects to electrify the Great Western, various lines in the North West, and also the Midland Mainline.

The most obvious result of all these activities will be rows of posts alongside the tracks, and the miles of copper traction power cable strung between them. Between the two, fastened to each post and supporting the contact wire, will be a complex arrangement of poles, brackets, clips, clamps and wires that makes up the overhead catenary. The actual design varies from system to system, but whether it is 25kV 50Hz AC as used in the UK and many parts of Europe, 15kV 16 2⁄3Hz AC in Germany and Scandinavia, or even 3kV DC in Italy and Morocco, the same types of components are needed.

Since 1908

Cariboni, or to give it its full name Osvaldo Cariboni Lecco SpA, is a company based in northern Italy not far from the shores of Lake Como. Established in 1908, Cariboni constructed Italy’s first overhead electrification on the Lecco-Colico line in that same year. Since then, the company has been involved in nearly every electrification project in the country, and quite a few outside.

More recently, Cariboni ceased installing complete lines, and concentrated on manufacturing electrification components. In recent years, the market for new equipment has dried up in Italy as most lines are already electrified and current requirements are only for refurbishment and repair. As a result, the company’s market mix has changed from being 80% domestic/20% export to almost being the other way around – only 20% in Italy. However, the core market is still primarily in Europe, with some exports to North Africa.

As Cariboni is one of the world’s major suppliers of these important components, and with the UK set to be a major consumer over the next few years, the rail engineer visited the factory in Pescate to find out more.

The Alstom connection

The first indication of the changes taking place was the sign “Welcome to Alstom” (in Italian of course) next to the reception desk. Alstom acquired 70% of the company in 2008 and purchased the remaining shares from the Cariboni family at the beginning of 2012. Cariboni’s managing director, Marco Rastelli, was enthusiastic about that development.

“Italy is a tough place to do business these days,” he commented. “Small and medium- sized companies struggle to get bank finance and a number have ceased trading for that reason. However, with Alstom behind us, we don’t have any of those problems and we can invest in new designs and new processes.”

Although not new, the Cariboni factory was neat and tidy, and almost completely self- contained. Design and development is important, with no fewer than ten of the 85 employees dedicated to that role. Luca Laini, engineering manager, explained that while many railways have their own standards, all of them different, increasingly the company was being asked to use its own expertise to come up with better, more cost effective solutions. Using computer-aided design and CAD-CAM programs, the development team is able to draw on both their own experience and Alstom technology to refine components used on everything from high- speed railways to urban trams.

Foundry and factory

Many of the components are cast, either from aluminium or bronze. These are sand castings, and the patterns are also designed and manufactured in-house. Made either from aluminium or resin, depending on the number of castings to be produced from each pattern, these are CNC machined and assembled by hand.

Mould production is a continuous process. Each “slab” of compressed sand has half a moulding in each end – the left hand end contains the recess for the right hand half of the component while the right hand side contains the left hand half of the next component. When fitted together, the two halves mate to form the complete mould.

Molten metal is then poured by hand into each mould and allowed to cool. Three crucibles are used to melt the metal, two for different compositions of bronze and one for aluminium as these are the most commonly used materials. Steel castings are purchased from other local foundries.

Once cool, the cast blanks are knocked free of the sand, which is cleaned, dried, treated and recycled. Components are then cut from the metal sprues which are also recycled, but at a rate of 20% recycled material to 80% new metal so as to maintain the purity of composition.

Casting finished dimensions is tricky. The metal part naturally shrinks on cooling, so allowance has to be made for that. Also, moulding the void into wet sand is not the most accurate of processes. However, on one component, the “gap” in a hook is maintained to a total tolerance of 0.3mm so that it doesn’t need subsequent machining.

Those parts that do need finishing are completed on a range of machinery from 4- axis CNC machining centres to simple linishing belts. Similar machines also manufacture components complete from bar and the factory turns out around 500,000 pieces a month. 60,000 different designs are held on file, from the very latest specifications to parts from the 1930s that are needed as spares.

Operations manager Bruno Colombo recalled a recent project in Northern Italy. An electrified line dating from the 1960s was to have been replaced, but to save money the decision was made to refurbish it instead. This produced an order for a variety of components to be manufactured to the original designs, which were still on record at Cariboni.

Other component types are also manufactured in the Pescate factory. Steel tubes for supports are cut to length, drilled and have various machined and cast fittings crimped into the ends. Washers, spacers and pins all form part of the range to make up a complete offering to electrification installers around the world.

Testing is important, whether it is electrical or mechanical, and a variety of test rigs even includes two posts and a gantry at the end of the car park, on which complete assemblies can be tested for strength and performance.

Cariboni views itself as primarily a mechanical engineering company which makes parts for electrification systems, rather than an electrical engineering concern. Thus material testing, mechanical design and production engineering form the core of the wide skill base of its employees.

New products, new markets

Involvement, and now ownership, by Alstom has brought other benefits. APS (Alimentation par le Sol, or ground-level power supply) is a third rail system used for powering trams that removes the need for overhead wires. Developed to power trams across historic areas of cities where the wires would be unsightly, the third rail is located between the tracks, with only the top surface exposed, and is energised only under the tram as it passes. The APS rail is fibreglass with a steel top surface to provide the contact. Ceramic spacers at each end ensure that arcing between sections is not possible, and the whole system is manufactured by Cariboni in a satellite factory at nearby Olginate.

Through Alstom, Cariboni is approaching the UK market as part of two joint ventures. ABC (Alstom-Babcock-Costain) is targeting the Network Rail electrification programmes, in particular those projects to be built around Network Rail’s new strategy of alliancing with turnkey providers. ATC (Alstom-TSO [Travaux Sud Ouest]-Costain) is tendering for Crossrail contracts, including the solid busbar overhead system to be used in the tunnels which is also manufactured by Cariboni at the Olginate facility.

So next time you travel on an electrified route, look up at all the bracketry from which the wire is suspended, and think of all the work that took place to put it there.