RAILWAYS around the world are responding to growing demand for their services by increasing capacity. This often means reducing headways to provide a more frequent service, which in turn reduces the time available for infrastructure inspections and maintenance.
Providing reliable infrastructure with low demand for maintenance is therefore crucial for system availability and reliability.
Point machines and locking devices in particular must be able to meet these demands as they represent a complex link between the signalling and the track. Indeed their availability demands are extremely high, since failures cause immediate delays to train services.
A new generation of turnout is therefore required which will reduce the demand for maintenance and increase inspection cycles. A reliable diagnostic system is also needed to monitor heavily-used systems between inspection cycles and to detect irregularities at an early stage which will prevent failures.
Moreover, turnout systems have to be reliable even in extreme environmental conditions. Wide variations in temperature cause switch points to expand or contract, which means that a periodic summer and winter adjustment is normally inevitable for the continuing reliability of the system. Furthermore, environmental factors such as rain, snow or dust increase wear and thereby the maintenance effort.
To meet these challenges, Voestalpine Signaling developed a series of point setting systems called Unistar HR, CSV 24 and CSV 34. Each point machine is characterised by its modular and compact design, which offers increased flexibility when mounting the units in the track and in the centre of the gauge.
A particular feature is the ability to mount the equipment on top of concrete slab track or concrete sleepers. There is no need to provide cut outs in the concrete slab, which reduces the complexity of civil works thereby cutting costs. Instead the concrete can be poured continuously and the switch machine is subsequently installed on top of the concrete surface. With ballasted track, the ability to install the equipment on top of a concrete sleeper avoids the need for a hollow steel sleeper.
This system makes the track more homogeneous and stable due to the even weight distribution. Machine tamping of the system is also possible, resulting in a better quality track bed. To increase operating speeds and passenger comfort, larger turnouts and turnouts with swing nose crossings can be used.
Maintenance of traditional turnout rodding systems demands a large amount of time for readjusting, greasing and cleaning. There is also a strong risk of hydraulic linkage from these systems.
As a result, Voestalpine Signaling avoids using a large rodding system in its products. Instead the drive, locking and detecting (DLD) units are hydraulically connected in parallel, which still offers strong performance but without the use of maintenance-intensive rodding systems.
Even in large turnouts where multiple setting levels are required, the motor unit of the Unistar HR point setting system is capable of operating multiple setting systems in a turnout including the swing nose crossing.
The system’s centre gauge installation means the drive and detector connecting rods are very short and can compensate for thermal length changes with the switch points without affecting the signalling-related settings. Periodic summer/winter adjustment of the rods is unnecessary, again reducing maintenance costs and improving the availability and reliability of the system.
Until now, centre gauge installations for point setting systems for narrow-gauge turnouts were limited to light rail standards with a point opening of typically up to 100mm. This is a far cry from the 160mm required to operate turnouts with appropriate wheel dimensions and rail types such as 60E1 for mass transit and main line railway applications. Of course the safety expectations and locking force requirements are much higher on main line railways and mass transit systems than for light rail lines.
To meet these needs, we developed the Unistar HR NG, which is based on the Unistar HR EM with electro-mechanic drive. This offers the same high quality, strength and availability, but is designed for installation in an even more compact enclosure.
Narrow-gauge railways can therefore benefit from the ability to install the point setting systems within their limited track gauge. For larger turnouts, either an individual drive or a low-maintenance torsion-driven back drive system is suitable.
In addition, all the point machine modules are available for installation in a watertight enclosure which will help to increase availability and reduce wear even under extreme environmental conditions.
For example, the Unistar HR consists of two main groups: the DLD unit and the motor unit in the case of an electro-hydraulic drive. Each has water and dustproof enclosures, and is certified according to IP 67.
The DLD unit consists of an integrated prism lock with adjustable point opening, a hydraulic actuating cylinder - or an electro-mechanic drive - and detector rods. The locking device is visible through windows in the lid, enabling visual checks when operating under manual control.
With watertight enclosures, a robust design and the use of high-quality materials for all components, it is possible to extend inspection intervals by up to 24 months. The use of visual inspections also helps to avoid disruptions to train operations.
In addition, it is possible to record and evaluate performance of the Unistar HR system by deploying the Roadmaster Series monitoring and diagnostic system. This detects deviations before the system malfunctions, which means maintenance becomes condition-based rather than following a fixed time-frame.
This innovative approach to designing a modern point setting system is producing a new generation of point machines that take advantage of built-in diagnostics and are characterised by low maintenance costs and extended inspection cycles. These developments should help railways to increase performance while driving down costs.