TRACK TECHNOLOGY
Conductor rail de-icing
In a similar manner, the heater element can be used for conductor rail de-icing and protection. The product used for this is known as CRH750. In this application the heater element derives its power supply from the conductor rail itself and is rated at a nominal voltage of 750 volts, although the heater construction is identical to is lower voltage sister. Because of the higher voltage rating (and therefore lower current draw) the maximum single circuit length possible is extended to 200 metres; ideal for heat- ing conductor rail in stations, depots and gradients where good shoe-to-rail contact is required for high traction current draw.
Graybar has had an overseas market for this product since the early 1990s but more recently Network Rail has also identified a need for some form of protection for their 3rd rail infrastructure.
Many 3rd rail DC conductor rails suffer from the effects of snow and ice, particu- larly when the collector shoe of the rolling stock picks up current from the top or head of the rail. Where this is not the case, such as with the Docklands Light Railway, where the collector shoe is under the rail head, poor rail contact is not an issue. However, for all top-contact systems, cold weather is bad news for the normal operation of the railway.
As mentioned above our first contract for CRH was not here in the UK but in Sweden.
164 | rail technology magazine Apr/May 11
The Stockholm Metro had suffered disrup- tion to its services for a number of years and Graybar were able to offer a solution in the form of our 750 volt rated product with a wide operating window ensuring that the heater could operate satisfactorily within various voltage levels between 600 and 1200 volts DC.
Both Network Rail and London Under- ground use a top contact 3rd rail system and failures can and do occur when weath- er conditions are particularly cold and icy conditions prevail.
Our CRH (conductor rail heater) heater, due to its higher voltage rating, is available in various circuit lengths designed to suit long and short 3rd and 4th rail sections thus ensuring that cable connections are kept to the minimum.
The heater is installed against the web of the rail, under the rail head, and is con- tained within a non-metallic heatshield identical to our points heating system. A thermal grease provides added advantages in heat transfer efficiency into the rail and allowing lateral movement and the whole assembly is securely attached with robust spring clips.
Photo HS1 Points Heating Cubicle (file: Camera 08-06-06 030jpg)
What of the future? With HS2 on the agenda, which will con-
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siderably benefit our UK rail network, and with the ultimate need to reliably heat high speed points, the demand for supplemen- tary heating of point mechanisms together with rail head adhesion heating and 3rd rail conductor rail heating has brought an ever greater need for an efficient, cost ef- fective track heating system.
There are also changes in the construction of trackside cubicles and supplementary enclosures with GRP finding favour for use on railway infrastructure due to its lower cost and weight against stainless steel.
Graybar has developed a modular points heating control cubicle making good use of the benefits of GRP where side panels can easily be replaced on site and an RCM module can be retro-fitted should the need arise.
Attach photo GRP control cubicle (file 029. jpg.)
Our self-regulating strip heating technolo- gy and associated control package has cer- tainly delivered and can continue to deliver a complete one-stop system approach for all track protection requirements for many years to come.
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