TRACK TECHNOLOGY
Managing director Graeme Ford outlines the history of Graybar’s self- regulating track heating systems.
A
t is now over 20 years since Graybar introduced our very successful self-
regulating electric strip heating system onto the UK rail infrastructure, and since that time we have refined the control pack- age and redesigned the details of the com- ponent parts to take into account the latest rail sections and point types, now becom- ing more familiar both in the UK and over- seas, taking particular care to retain our well-proven basic control functions.
Until the launch of our self-regulating points heating system, all railway point heating had been accomplished by gas, oil and fixed constant wattage heating sys- tems, all with varying degrees of success and dubious reliability in the harsh envi- ronment of the railway infrastructure.
Very soon after we received the initial or- ders from British Rail and Network South East (as it was then known), we successfully won a contract to supply the SL Stockholm Metro in Sweden where Graybar heaters were installed on a large number of points for points heating, as well as their 750 volt DC 3rd rail conductor rail system for rail head de-icing.
This valuable experience subsequently
proved that our unique flexible self-reg- ulating heater could efficiently maintain points and 3rd rail protection from the ef- fects of snow and ice together with very low ambient temperatures.
When Graybar initially launched the self- regulating heater element onto the UK market it immediately found favour with track engineers responsible for ensuring reliable switchpoint operation and pro- vided many benefits over alternative tradi- tional means of heating.
The Docklands Light Railway and all the tram systems adopted the Graybar self- regulating track heating system in the early 1990s on their new infrastructure and, to this day, continue to install our system on new track.
With its insulated outer jacket, the heater element also proved to be ideal for instal-
162 | rail technology magazine Apr/May 11
lation on DC electrified track on Network Rail and London Underground Ltd infra- structure, where it is much safer to install and maintain than a rigid metal-sheathed product.
The heater, with its unique flexible paral- lel circuit construction, ensures that it can inject just the right amount of heat into the rail where and when it is needed along its length and with the added benefit of a field proven heater element life of more than 20 years that far exceeds the typical fixed wattage alternative service life of 5-7 years.
The extended life of a self-regulating heater element is primarily due to its construc- tion. It does not contain a wire filament but a semi-conducting, carbon-loaded polymer that cannot burn out, break or fail to pro- vide a reliable power output from its posi- tive temperature coefficient (PTC) charac- teristic.
In addition the element is very flexible; a vital and essential improvement over the rigid constant wattage elements that, by their very construction, are impossible to fit securely against the rail surface with in- evitable overheating and resultant filament failure in service.
The 110 volt self-regulating heater element is also available in various circuit lengths up to 25 metres and is customised to suit the particular type of point being heated, for example, the new UIC60 shallow depth points now being installed in the UK.
The long circuit lengths also enable the heater to be used for rail head heating. This is where the head of the running rail is heated to ensure it remains dry for im- proved rail adhesion; a vital requirement, particularly on light rail infrastructure, where the vehicles are much lighter and steeper gradients are to be found.
Because of its flexible construction and Graybar’s ability to custom manufacture heaters for points heating with various fac- tory fitted cable connections, we are able to feed heaters for the new in-bearer clam- plocks and the well known MK2 clamplocks without the need for additional cables.
The clamplock, or supplementary heaters, are simply branched off the toe end switch rail heater elements and there are many examples of this arrangement resulting in a very reliable heating system that is easier to maintain.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228