Innovative rail switch heating system
One of the biggest sources of disruption for a rail system in winter is weather related disturbances in switch operation. Snow or ice in the switch points often causes loss of switch function, which in turn results in disrupted train services and very large costs for the society. There are several different methods to keep track switches clear of snow and ice, ranging from manual sweeping and ice hacking to different systems for melting snow and ice. Few of these are though reliable and efficient.
Inductive technology is the most efficient and functionally safest system on the market. It is significantly more energy efficient than conventional systems that are based on resistive heating elements.
The internal coil generates a magnetic flux in the main core. The flux flows through the heating plate which is made of a material that has poor magnetic properties, causing losses in the magnetic flux, thus generating heat. The magnetic ratio time / flow (T) is controlled by a thermostat located in the heating element directly connected to the underside of the rail. The heat from the heating plate is distributed to the space between the sleepers via an aluminum plate above the heating plate. The thermostat is placed where the heating plate meets the track foot, which provides enhanced heat dissipation and therefore upwards heating in the rail. The entire heating system for a track switch comprises a number of heating elements spaced between the sleepers along the switch. The temperature is controlled individually in each element using the built-in thermostat.
The heating element will reach its operating temperature, within five minutes and this temperature is very high, about 120 – 135°C, melting away snow and ice very effectively. Because of this rapid warming it is enough to turn on the heater only when snow fall has begun, or to use camera control where the camera system detects that there is snow or ice in the switch. The efficiency and the high temperatures which are soon achieved also ensure that the switch can be kept free of snow and ice even in the worst winter conditions. The claw design, which clamps the heater plate against the rail foot, minimizes installation time and therefore the time in which personnel need to work in the track environment. Plug-in connectors also allow for safe and rapid electrical connection of each heating element.
The robust design makes it impervious to mechanical snow removal and other external influences. The assembly is completely impregnated with double coating layers. The black heat resistant paint withstands the temperatures up to +400˚C. The coil is protected by a 10mm thick steel plate mounted on the rail foot. Electrical connections are made using IP 68 class plug connectors.
In addition to the savings gained from reduced traffic disruption and reduced manual snow removal there is also direct energy cost savings of about 60 % compared to systems based on heating wires.
The switch heater is controlled from a track side control cubicle. The control cubicle is equipped with a main switch, fuses, contactors and control electronics. A position sensor in the switch is used to indicate the current switch position, i.e. determining which tongue is currently abutting the rail, as this side of the switch only requires low heating effect. This feature allows for additional energy savings. The system can be remotely controlled or automatically using a camera system.