UNIVERSAL AXLE COUNTER SYTEM 1. 0INTRODUCTION : 1. The track circuits are considered as the vital component of signaling system to achieve safety of train operations. Various Accident Enquiry Committees have recommended to bring more and more tracks under track circuiting to safeguard against reception of trains on occupied lines. The track circuiting could not achieved desired progress die to virtual scarcity of wooden sleepers, prohibitive costs and environmental consciousness in the country and the world at large.
Availability of concrete sleepers have solved the problem to some extent but track circuiting on loop lines, points and crossings still suffers for want of adequate supply and insertion of concrete sleepers. 2. Axle counters were developed as a substitute for track circuiting. Initially axle counters were imported from Germany to gain experience and to evaluate their suitability for adoption on Indian Railways. Having gained acceptability for introduction on a wide scale on Indian Railways, it was considered to take up indigenous development of axle counters which was taken up in collaboration with IIT, Delhi and DOE.
Two models of axle counters known as single entry/exit axle counter were emerged and after extensive laboratory and field trials under various conditions, the design was finalized and commercialized through private sector as well as public sector. Based on the feed back from filed, a new axle counter has been developed by RDSO, known as “UNIVERSAL AXLE COUNTER”. 1. 1ADVANTAGES The advantages of Axle counter over a conventional track circuit are that: i) It does not require wooden sleepers (where concrete sleepers are not available) except for short track circuits to suppress the counts due to movement of insulated trollies. i) An axle counter system can cover a very long section up to 15 km as compared to 750 mts of maximum length of operation of conventional track circuit. iii) It does not get affected either by flooding of track or poor maintenance of track unlike the track circuit, which is highly susceptible to these conditions. iv) It does not require insulating joints, thus, rails can be continuously welded. This reduces track maintenance cost, lower wear and tear of tracks and vehicles and to increase traveling comfort. 1. 2APPLICATION : 1. Axle counters have been finding more and more uses on modern safety signaling systems in railways.
These are being used presently for the following : i) Monitoring of berthing tracks in station areas and yards (drawing no. 1005985A4). ii) Monitoring of Point zones in station areas and yards (drawing no. 1005986A4 & 1005987A4). iii) Automatic Signaling systems using axle counters (drawing no. 1005988A4). iv) Block working through axle counters using multiplexers with cable are radio communication (18GHz) (drawing no. 1005989A4 & 1005990A4). v) Level-crossing warning system using axle counter (drawing no. 1005991A4). 2. BRIEF DESCRIPTION : (Drawing no. 1005992A2). it is an electronic device consisting of :- ) A set of track inductors fitted at the entrance of a length of a track which “COUNTS IN” the number of axles passing over them. ii) Another set of track inductors fitted at the exit of the length of track which “COUNTS OUT” the number of axles passing over them. iii) An evaluator which registers “COUNTS IN” and “COUNTS OUT” and ‘CLEAR’ the line, if two are equal and shows “ACCUPIED” if the two counts are defferent. iv) The principal of counting axles is described below (drawing no. 1005993A4). The magnetic flux generated by the 5 khz current following in the transmitting coil induces a voltage in the receiver coil.
These coils are fixed opposite to each either side of running rail. When a wheel passes between these two coils, the magnetic flux path gets disturbed and the induced voltage in the receiver coil is substantially reduced. These reductions (called dip) are processed in the evaluator. 1. 4The complete system consists of :- i) Track mounting and track side equipment. ii) Transmission media between track side equipment and central evaluator. iii) Central evaluator with EV relays and SUP relays as its output. iv) Reset box. v) Line verification box. Brief description of Each unit:- )Track mounting and track side equipment : Track mounting equipment consists of a pair of transmitter and receiver coils housed in specially designed housings which are fixed to flange of a rail section by means of suitable rail clamps using bolts and nuts. Each detection point has two sets of such track devices mounted on same rail with a fixed stagger between them. The two transmitter coils of a detection point are connected in series to 5khz oscillator housed in electronic junction box which is installed in a location box by the side of the track.
The output of two receiver coils of a detection point serve as inputs to two receiver amplifiers housed in the same electronic junction box through cables which are part of the track mounting equipment. Electronic junction box is powered by 24V DC Supply. ii)Transmission media between track side equipment and Central evaluator: The connection between track side equipment and central evaluator made using balanced twin twisted quad cables of specification IRS: TC/41/90. The output of electronics junction box and input of central evaluator are matched for an impedance of about 180 Ohms at 5 khz.
There is attenuation of signal from electronic junction box to central evaluator which limits the length of the cable. Other media such as optic fiber and wireless system may also be used in place of cable by incorporating appropriate interfacing equipment at transmitting and receiving ends. iii)Central evaluator with EV relay and SUP relay as its output: The signals received from electronic junction boxes are processed in the central evaluator first by analog circuits and them by digital circuits to produce suitable output in terms of picking up or dropping of EV and SUP relays.
The DIP’s generated by wheels as they pass over the track devices installed at detection points, after they get processed, generate count pulses in a fail safe manner. These pulses are identified as ‘IN COUNTS’ or ‘OUT COUNTS’ depending on the direction of movement of vehicles over the monitored section. The counts are also displayed through the 7-segment display on front panel of evaluator. The display unit is useful in fault localization, initial and periodical adjustments. The evaluator is provided with its own power supply unit known as DC-DC converter mounted in the same rack and requires 24V DC supply for its operation.
The output of EV and SUP relays are used to indicate “track clear” or “track occupied” conditions. iv)Reset Box: This equipment is installed in station master’s room to enable resetting of central evaluator in case of failure of system after observing prescribed procedure. The reset unit consists of RESET key (which gets actuated after inserting, turning and pressing) the counter and 3 LED indications (red, yellow and green). This unit requires 24V DC supply for its operation. This unit functions in conjunction with line verification box. )Line Verification box: The box is required to be kept near monitored track portion outside SM’s office for achieving co-operative feature. This is a box consisting of a lock with a key fixed inside. The lock gets actuated only when key is inserted, turned and pressed. Whenever there s a failure of axle counter, SM will depute his ASM / Switchman after verification of the track, if found clear, will report to SM who in turn will handover the key of line verification box for operation. 1. 5TYPES OF SYSTEM : There are four types of system used in Indian Railways. ) 1-D System ii) 2-D System iii) 3-D System iv) 4-D System i)1-D System (Drawing No. 1005994A4) : In this system, there is a common detection point at entry and exit point of monitored section. This system is useful for monitoring the berthing track of terminal yard. A train after passing the detection point generates pulses equal to axles in it and these pulses are counted and stored by the evaluator as ‘INCOUNTS’ At the time of exit of train, the same detection point will be encountered and it generates equal number of pulses as during entry.
These pulses are counted and recorded as ‘OUTCOUNT’ by the evaluator. When INCOUNTS & OUTCOUNTS are same, the system gives a “track clear” indication. Otherwise “track occupied” indication is shown. ii)2-D System: (Drawing No. 1005995A4). The principle of working of this system is similar to 1-D System except that in this system there are two detention points, one at each end of the monitored section. This system is useful for providing track circuiting on berthing track. iii)3-D System: (Drawing No. 1005996A4). In this system, there are three detection points.
The principle of working of this system is similar to 2-D System. This system is useful for providing track circuitry on points, crossing and siding. iv)4-D System: (Drawing No. 1005997A4). In this system, there are four detection points. The principle of working of this system is similar to 2-D system. This system is useful for providing track circuiting on branch lines, sidings and points and crossings. The design of 4-D system is such that it can be converted into 2-D system and 3-D system and vice-versa. 1-D SYSTEM : (DRAWING NO. 1005994 A4)
In this system, the 2-D system of CEL type Rack ACS 55 consisting of EV 542 -2D evaluator is used as 1-D type system as given below. One common detection point TX/RX Coils and its EJB installed at the Entry/ Exit of the track for monitoring the berthing track of terminal yard. The signal of EJB of the common detection point is fed to A&C Channels in parallel and B&D Channels in parallel at the terminal plate inside the Axle Counter Rack in Relay room. One detection point feeds all the 4 Channels of 2 D type system to make it as 1 D system.
When train enters the terminal yard each wheel of the train is processed by A & B and C & D Channels and registered as two “In counts”. The series of wheels of train are stored as “In counts”. Similarly when the train leaves the terminal yard each wheel gives two “out counts” into the system and all the “Out counts” are stored. Both “In counts” and “Out counts” becomes equal when complete train exits from the terminal yard and section is shown as clear. DOUBLE EVALUATOR RACK: (A 006903 A3). Two evaluators of EV 542 (2D) / EV543 (3D) / EV544 (4D) can be used independently in 30U rack supplied by CEL.
Each of the Evaluator can be of 2D or 3D or 4D or even 1D type. CEL wires and supply the double evaluator for maximum of two evaluators x 4 detections. The input connections to be wired and extended independently at site for the respective track circuits under monitoring. The clear / occupied indications and the EVR & SUPR set of Relays for each evaluator is provided separately. It is recommended to check the input / output external wiring of Double Evaluator Rack and ensure its independent operation. The Saving of space is achieved in Relay Room by deploying the double evaluator rack in Railways.