Page 50 - วิศวกรรมสาร ปีที่ 74 ฉบับที่ 4 ตุลาคม - ธันวาคม 2564
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Axle Counters (AC) are based on a completely different technology and don’t have to rely on the
                 electrical properties of a track section. And there are many more differences between TC and AC
                 in installation and operation. The decisive advantages of Axle Counters include, for example: Cost
                 efficiency in installation and operation, lower maintenance requirements, possibility to provide
                 additional information and flexibility.

                 The  following table  compares  the features and characteristics of both technologies directly:

                                               Axle Counters                Track Circuits

                  Functional Scope             Track vacancy detection,     Track vacancy detection, rail
                                               direction, speed, number of   breaks, cab signalling
                                               axles
                  Compatible with electric     Yes                          Special measures required
                  tracion                                                   depending on traction and rail
                                                                            type
                  Track section length         Theoretically unlimited,     Two miles maximum. Long
                                               depending on network         block sections can be
                                               structure. One single AC     equipped with multi- section
                                               system can replace many      track circuits, which is a
                                               track circuits, giving improved  costly solution
                                               reliability and cost
                                               effectiveness
                  Rail breakdown detection     No                           Some breaks, if clean
                  Reset required after error   Yes – remote and local reset   Not required
                                               options available
                  Can monitor complex          Yes, without restriction     Yes, with complex designs
                  switches and crossovers                                   required
                  Maximum speed                280 mph (450 km/h)           155 mp (250 km/h)
                  Sensitive to environmental   Virtually immune to these    Can be significantly impacted
                  conditions (heat, snow,      conditions, (potentially     by any of these conditions
                  water, road salt, rust debris,   affected by metallic debris)
                  etc.)
                  Ballast resistance           independent of ballast       TCs cannot operate on track
                                               conditions and therefore ideal  with steel sleepers, metal
                                               for use in long wet tunnels   bridges, wet tunnels, etc.,
                                               and in locations where ballast  where the running rails are
                                               may become saturated by      not isolated from each other
                                               (salty) water                or where the minimum
                                                                            allowed ballast resistance
                                                                            cannot be guaranteed

                  Wheel shunt resistance       Not affected by the value of   Loss of track circuit shunting
                                               the train shunt. ACs provide   capacity is a serious hazard
                                               highly reliable train detection   and may lead to wrong-side
                                               on infrequently used lines   failures. Electrical wheel-to-
                                               and in the presence of       rail contact may be
                                               intensive leaf fall          permanently compromised by
                                                                            excessive sanding, dust,
                                                                            fallen leaves or


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                  วิศวกรรมสาร ปีที่ 74 ฉบับที่ 4 ตุลาคม-ธันวาคม 2564
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