COLAS Rail is using Doosan Portable Power’s new generation of compressors to apply shotcrete to the interiors of French train tunnels.
Colas is the first French company to purchase the compressors. The first two new generation Doosan 12/250 portable compressors have been delivered to the technical team at the Les Marches offices of Colas Rail RTS, based near Chambéry. The 12/250 Stage IIIB compliant compressor provides a free air delivery of 25 m3/min at a working pressure of 12 bar.
The Colas Rail RTS team uses the Doosan compressors mainly for spraying quick setting, dry-mix shotcrete in tunnel interiors as part of renovation or refurbishment projects.
The compressors are installed on railway wagons and have to function inside tunnels for hours on end – until the job is finished and, at the end of a job, the compressors are very often covered in splashes of shotcrete.
Both men and equipment have to endure extremely tough conditions, including high temperatures caused by the confined space in which the work is done.
On top of this, dry air is absolutely essential for the effective spraying of quick-setting shotcrete.
Thanks to the Doosan compressors, around 98% of the humidity is removed from the compressed air prior to its use by the Colas Rail RTS team for shotcreting.
Thierry Delaporte, Technical Director of Colas Rail RTS, said, “Our teams have to work in challenging conditions during operations inside tunnels, and very often have to work at night to avoid disrupting rail traffic. Our equipment has a tough time too, so we need rugged machines.
“We’ve been using Doosan compressors for a number of years now and really appreciate their performance, reliability and easy maintenance.”
In September and October 2013, teams from the Colas Rail RTS division near Chambéry carried out what was, for them, a fairly typical job and one in which they have a great deal of experience.
Work was needed on the Madeleine tunnel in the Maurienne region.
As with many railway tunnels originally constructed in brick towards the end of the 19th century, dimensions no longer satisfied the latest railway traffic standards. Renovation and track repositioning work therefore involved ‘widening the walls’.
The extent of the widening work was not a major issue, since only a short section of the 359-metre-long tunnel was involved, where the track was at an incline on a bend.
What made the project difficult were the operating conditions.
Work had to be completed without halting traffic; the atmosphere was hot, dusty and humid; severe restrictions were imposed on working positions, and strict safety precautions were in place.
Luckily, the site management was extremely experienced as were the teams provided by Colas Rail.
Each team specialised in a particular job: marking out, cutting, demolition, propping, concrete mixing and spraying, finishing and cleaning up.
As much as possible, the work was mechanised using special equipment mounted on wagons to form a ‘work train’.
The shotcrete spraying was the most delicate phase in the operation as the lifetime of the work depended largely on its effectiveness.
Colas Rail employs specialist workers to ensure success: a spraying team made up of one machine operator and one or two sprayers.
This is where the company’s expertise really comes into play, because dry-mix shotcrete spraying in tunnels requires experienced operators and equipment capable of withstanding the harsh conditions. Humidity, dust and heat are the order of the day.
To tackle this job, Colas Rail decided to use one of its new, high power Doosan 12/250 compressors.
The unit was set up to deliver a constant air pressure of between 8 and 12 bar with the lowest possible humidity content – under 5% – in order to guarantee a top quality shotcrete coating.
The compressor proved able to function perfectly for long sessions in challenging ambient temperatures, not to mention the dust!
On top of its excellent performance, the Doosan 12/250 compressor proved a real winner for its compact size, which allowed it to operate on the tight load bed of a French railway wagon on only a single track.
Colas Rail also places great importance on equipment being easy to clean and maintain.
The new compressor has fully satisfied the company’s requirements.
Colas Rail is a French construction company specialising in services to the railway sector.
It is a subsidiary of the Colas Group (itself part of the Bouygues Group), and employs a workforce of around 3900. The company’s turnover in 2012 came to 656 million euros.
The RTS division of Colas Rail, based near Chambéry, employs a staff of 80 and specialises in the maintenance and renovation of railway tunnels.
The division owns a fleet of 12 Doosan Portable Power compressors (ex Ingersoll Rand) plus a few older models that have been in use for over 10 years.