Track Circuits Overview
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Questions and Answers

What is the primary purpose of quarterly interchanging DC track relays?

To prevent permanent magnetisation.

List three visual checks that must be conducted on track relays during inspections.

Movement of armature, wiping of contacts, and arcing of contacts.

What action should be taken if a defective track relay is found during inspection?

The defective relay should be replaced immediately, and a report on the defects must be submitted.

How often should plug-in type track relays be replaced?

<p>Every 12 years, or earlier if warranted by the condition or usage.</p> Signup and view all the answers

What is the importance of having components ready before opening an insulated rail joint?

<p>It ensures a smooth and efficient replacement process without unnecessary delays.</p> Signup and view all the answers

What must be done if there is no gap at the insulated rail joint when replacing an end-post?

<p>Loosen the rail fastening, pull back the rail, and insert the end-post between the rail ends.</p> Signup and view all the answers

Why is it imperative to properly pack at least three sleepers on either side of an insulated rail joint?

<p>To maintain track stability and integrity throughout the joint area.</p> Signup and view all the answers

What maintenance procedure must be followed regarding fish bolts?

<p>Fish bolts must be kept tight.</p> Signup and view all the answers

Why is it important for the track circuit rail to be series bonded?

<p>To ensure that defective bonding cannot cause a wrong side failure of the track circuit.</p> Signup and view all the answers

What is a major consideration regarding traction return in rail bonding?

<p>The traction return rail cannot be series bonded to avoid disconnection risks that may lead to loss of train shunt.</p> Signup and view all the answers

What occurs if there is a break in the uninsulated rail of a single rail track circuit?

<p>Very heavy current will flow through the track relay and equipment at the feed point.</p> Signup and view all the answers

How should uninsulated rails be bonded to prevent excessive current flow?

<p>The uninsulated rails of adjacent tracks should be cross bonded at intervals of no more than 100 meters.</p> Signup and view all the answers

What type of wire is provided on traction masts in single line track circuited sections?

<p>A continuous earth wire capable of carrying full traction return current.</p> Signup and view all the answers

What must be done to connect uninsulated rails to traction masts?

<p>Structure bonds must be riveted at both ends to connect uninsulated rails to each traction mast.</p> Signup and view all the answers

What should not be connected to the running rails in double rail track circuits?

<p>No structure bonds, cross bonds, or connections to earth wires or return conductors should be made.</p> Signup and view all the answers

What is a potential installation method for double rail circuits when necessary?

<p>An impedance bond must be specially installed to provide a neutral point for necessary connections.</p> Signup and view all the answers

What are the two modes in which an Audio Frequency Track Circuit can operate?

<p>Local fed and remote fed modes.</p> Signup and view all the answers

List the components of an Audio Frequency Track Circuit.

<p>Tuning unit, transmitter, receiver, power supply, track connections, and impedance bond.</p> Signup and view all the answers

What precautions should be taken regarding the connection of the rail and tuning unit during installation?

<p>Ensure the tightness of the connection.</p> Signup and view all the answers

What is prohibited at the terminal junctions on insulated joints within the same frequency?

<p>Connecting track circuits with the same frequency.</p> Signup and view all the answers

Why is circuit pairing important when wiring and installing track circuits?

<p>Circuit pairing prevents significant cross talk levels in adjacent circuits.</p> Signup and view all the answers

What protective measures should be installed to safeguard electronic equipment from atmospheric voltage surges?

<p>Protection against both common mode and differential mode voltages.</p> Signup and view all the answers

How should the transmitter, receiver, and power supply be mounted for maintenance?

<p>In a standard relay rack allowing maintenance staff to view the track relay.</p> Signup and view all the answers

What should the design and installation of field equipment consider?

<p>Requirements for mechanised track maintenance and safety for personnel.</p> Signup and view all the answers

What is the primary purpose of locating the Relay End and Feed End at the boundaries of a track circuit?

<p>To ensure effective monitoring and control of the track circuit boundaries.</p> Signup and view all the answers

Why should all contacts of the track relay be loaded as much as possible?

<p>To enhance reliability and minimize the risk of false detections in the track circuit.</p> Signup and view all the answers

How should jumper connections be arranged to ensure they are effective?

<p>They should be made in series and protected from damage while considering rail creep.</p> Signup and view all the answers

What minimum cross-section should galvanized iron wire used for short jumpers be?

<p>The cross-section should not be less than 8 SWG.</p> Signup and view all the answers

What type of conductor is recommended for the lead wires connecting feed sets to junction boxes?

<p>Copper conductor with a minimum cross-section of 2.5 sq.mm.</p> Signup and view all the answers

What is the maximum resistance of rail and bonding per 1000 meters for track circuits longer than 700 meters?

<p>The maximum resistance should not exceed 0.5 ohm.</p> Signup and view all the answers

What methods can be employed for securing bond wires near fish plates?

<p>Bond wire clips and securing them with channel pins or by brazing/welding.</p> Signup and view all the answers

Why is it recommended to use duplicated jumper connections?

<p>To provide redundancy and minimize the risk of connection failures.</p> Signup and view all the answers

What applications may benefit from the use of Axle Counters instead of conventional track circuits?

<p>Applications include Intermediate Block Stop Signaling, Automatic block signaling, poor drainage stations, Block Section Proving of Clearance, rust-prone tracks, and tunnels or bridges.</p> Signup and view all the answers

Why might Digital Axle Counters be preferred on girder bridges?

<p>Digital Axle Counters may be preferred due to their improved accuracy and reliability in detecting train presence in challenging conditions.</p> Signup and view all the answers

What is the purpose of trolley suppression in the context of Axle Counters?

<p>Trolley suppression is designed to prevent Axle Counters from incorrectly counting the wheels of motorized trolleys, ensuring accurate train detection.</p> Signup and view all the answers

What installation guidelines must be followed for Axle Counters?

<p>The installation must follow the OEM's prescribed guidelines and an approved pre-commissioning checklist.</p> Signup and view all the answers

In what scenarios can trolley suppression provision be omitted during installation?

<p>Trolley suppression can be omitted in sections using non-metallic wheels or in point zone portions with approved circuits.</p> Signup and view all the answers

What role does the installation of trolley suppression arrangements play in Axle Counter operation?

<p>Trolley suppression arrangements ensure that insulated trolleys do not trigger the Axle Counter, thereby maintaining system accuracy.</p> Signup and view all the answers

List one specific location type where the installation of Axle Counters is beneficial.

<p>Axle Counters are beneficial in flood-prone sections due to their effectiveness in such challenging environments.</p> Signup and view all the answers

What aspect of Axle Counter technology is expected to improve in future models?

<p>Future models are expected to include an inbuilt provision of trolley suppression, enhancing their functionality.</p> Signup and view all the answers

What should the Station Master do after an Axle Counter failure?

<p>The Station Master should verify the clearance of the block section with the Assistant Station Master by exchanging private numbers and recording it in the Train Signal Register.</p> Signup and view all the answers

How is the reset operation of the Axle Counter controlled between stations?

<p>The reset operation must be initiated cooperatively between the ASMs of both the dispatching and receiving stations, preventing independent resetting.</p> Signup and view all the answers

What must happen before the Axle Counter can be reset?

<p>The block section must be verified as clear of any obstructions or vehicles before initiating a reset.</p> Signup and view all the answers

What role does the reset box play in the Axle Counter system?

<p>The reset box, operated by a locked key, allows for controlled resetting of the Axle Counter while being monitored by a non-resettable counter.</p> Signup and view all the answers

What should be checked by Signal and Traffic Inspecting officials during station inspections?

<p>Officials should check and ensure that the exchange of private numbers between ASMs is being followed meticulously.</p> Signup and view all the answers

What is the importance of the Line Verification box (LV box) in this context?

<p>The LV box is utilized for the physical verification of a failed track section to ensure it is free from obstruction before receiving a train.</p> Signup and view all the answers

What is documented in the Train Signal Register during the reset process?

<p>The Train Signal Register records each operation of the reset button, noting the movement of trains before and after resetting.</p> Signup and view all the answers

What established rules govern the procedure for resetting the Axle Counter?

<p>The Station Working Rules clearly lay down the procedure for resetting and the verification of clearance.</p> Signup and view all the answers

What indication should be displayed on the panel when a track line is unoccupied?

<p>Yellow/white Light</p> Signup and view all the answers

What is the maximum excitation limit for QBAT Relays according to the specified guidelines?

<p>235%</p> Signup and view all the answers

In what scenario should plug-in type track relays exclusively be used?

<p>Future installations in both Non-RE &amp; RE areas.</p> Signup and view all the answers

What should be the minimum excitable voltage for a DC Track Relay as per the regulations?

<p>125% of its rated pick up voltage.</p> Signup and view all the answers

What should be the maximum length of track circuits as per different track parameter conditions?

<p>Specified in the provided table, adhering to conditions.</p> Signup and view all the answers

What is the minimum ballast resistance required for track in the block section?

<p>4 ohms per km</p> Signup and view all the answers

How often must the track circuited portion of the track be inspected jointly by S&T and Permanent Way Inspectors?

<p>At least once every six months.</p> Signup and view all the answers

What should be done if abnormal readings are noted during track circuit tests?

<p>Suitable remedial action shall be taken.</p> Signup and view all the answers

What is the significance of maintaining the percentage of missing insulated liners for the track circuit length?

<p>It should not exceed 3%.</p> Signup and view all the answers

What specific attention must be given to track drainage during rainy conditions?

<p>Defects must be reported to the SSE/JE(P-Way).</p> Signup and view all the answers

How frequently should a Train shunt test be conducted?

<p>Every quarter and every time the track circuit is adjusted.</p> Signup and view all the answers

What is the minimum availability of insulated liners required when using PSC Sleepers?

<p>A minimum level of 97%.</p> Signup and view all the answers

What must be reported regarding defective valves of overhead water pipes in track circuited areas?

<p>They must be reported to the Inspector of works SSE/JE(Works).</p> Signup and view all the answers

What specific requirement must be met for both rails in an Audio Frequency Track Circuit?

<p>Both rails must be balanced with respect to earth and current flow.</p> Signup and view all the answers

Why are impedance bonds necessary in the design of Audio Frequency Track Circuits?

<p>They are necessary to balance the traction rail return current where no other provisions are present.</p> Signup and view all the answers

What is the maximum continuous current that AC impedance bonds should support?

<p>AC impedance bonds should support a continuous current of 400 Amperes.</p> Signup and view all the answers

What is the primary distinction between AC and DC impedance bonds?

<p>AC impedance bonds are generally designed for lower traction current ratings than DC impedance bonds.</p> Signup and view all the answers

What conditions must be considered in the design and installation of impedance bonds?

<p>Design and installation must consider mechanized track maintenance and safety for personnel.</p> Signup and view all the answers

What should be done to the leads between impedance bonds across IRJ on the same track?

<p>They must be capable of carrying the traction current.</p> Signup and view all the answers

What is the significance of examining Electric Traction Units for harmonics before service?

<p>It is crucial to identify any potentially harmful harmonics that could affect overall performance.</p> Signup and view all the answers

Why are impedance bonds designed for AC traction systems not suitable for DC traction systems?

<p>They are not suitable because AC impedance bonds are typically rated for lower currents than necessary for DC systems.</p> Signup and view all the answers

What is the maximum allowable resistance for rail bonding per 1000 meters for track circuits that are shorter than 700 meters?

<p>1.5 ohms</p> Signup and view all the answers

How far should track circuit termination be from the Fouling Mark?

<p>At least 3 meters</p> Signup and view all the answers

What should be ensured before the installation of an insulated joint?

<p>Compliance with permanent way requirements in Para no. 17.1.2</p> Signup and view all the answers

Where should insulated rail joints ideally not be installed?

<p>On the outer rail in curves</p> Signup and view all the answers

What is the minimum spacing required between tracks in existing yards?

<p>4.265 meters</p> Signup and view all the answers

What's the main impact of incorrect installation sizes of insulated rail joint components?

<p>It may lead to malfunction or safety hazards.</p> Signup and view all the answers

What installation should be done by the Civil Engineering Department according to the text?

<p>Installation of glued rail joints</p> Signup and view all the answers

What happens to track relays when cut section track circuits are de-energized?

<p>They open the track feed and shunt the track circuit.</p> Signup and view all the answers

What minimum distance must be maintained between adjacent axle detectors, and why?

<p>The minimum distance must be at least 2 meters to minimize mutual interference.</p> Signup and view all the answers

What is the purpose of installing deflectors near axle detectors?

<p>Deflectors are installed to protect axle detectors from damage caused by hanging parts of moving trains.</p> Signup and view all the answers

How should cables between axle detectors and track side electronics be managed?

<p>Cables should be terminated on a cable distribution board for testing, and transmitter and receiver coil cables must be laid in different pipes.</p> Signup and view all the answers

What is the recommended ripple limit for input power supply to track side electronic equipment?

<p>The maximum ripple limit for the input power supply shall be 50 mV peak to peak or 10 mV rms.</p> Signup and view all the answers

Where should the evaluator be installed, and why is the location significant?

<p>The evaluator should be installed in a relay room or inaccessible location to protect it from unauthorized access and environmental damage.</p> Signup and view all the answers

What measures should be taken to avoid vibration of track devices under train movement?

<p>A minimum of 400 mm sleeper spacing must be ensured, and proper packing of sleepers should be conducted.</p> Signup and view all the answers

What type of power supply is recommended for track side electronic equipment in remote locations?

<p>Separate power supply systems should be used for track side electronic equipment in remote locations.</p> Signup and view all the answers

What precautions need to be taken regarding electromagnetic interference when installing electronic equipment?

<p>Electronic equipment should be located away from sources of heavy electromagnetic interference like industrial machinery.</p> Signup and view all the answers

What is a significant reason for the quarterly interchanging of DC track relays?

<p>To prevent permanent magnetisation of the relays.</p> Signup and view all the answers

Why should the defective track relay be immediately replaced without attempts to repair it?

<p>Because unauthorized repairs can lead to further malfunctions or safety hazards.</p> Signup and view all the answers

What condition must be ensured regarding the rail fastening during the replacement of an end-post?

<p>The rail fastening should be loosened to allow the rail to be pulled back.</p> Signup and view all the answers

What should be visually checked to ensure the integrity of the track relay contacts?

<p>Wiping of contacts, arcing, and any pitting or charring.</p> Signup and view all the answers

Which components must be prepared before opening an insulated rail joint?

<p>The replacement components conforming to the rail section.</p> Signup and view all the answers

What is the minimum distance recommendation for packing sleepers on either side of an insulated rail joint?

<p>At least three sleepers should be packed properly.</p> Signup and view all the answers

What are the main conditions for the maintenance of insulated rail joints according to the guidelines?

<p>Components must match the rail section, and sleepers must be adequately packed.</p> Signup and view all the answers

What role does the visual inspection play in the maintenance of track relays?

<p>It helps identify defects that could affect relay performance and safety.</p> Signup and view all the answers

Flashcards

Track Circuit Relay Ends

The locations at the boundaries of a track circuit where track relays are connected.

Track Relay Contact Loading

All track relay contacts should be connected as much as possible, and if spares are available, connect them in parallel to increase the capacity.

Jumper Connections

Connections within a track circuit that carry signal or control signals. Crucially, they electrically connect sections of track in series, excluding the traction return rail.

Jumper Connection Protection

Jumper connections should be protected from damage, preferably with duplicates, ensuring circuit reliability.

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Track Jumper Material

Short jumpers use galvanized iron wire (minimum 8 SWG), while long jumpers use cables (minimum 7/0.750 mm).

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Track Lead JB Location

The Junction Box (JB) for track leads should be clear of ballast.

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Lead Wire Material

Lead wires for connecting to the feed and relay ends of the track circuit should ideally be copper with a cross-section of at least 2.5 sq.mm.

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Track Lead Wire Protection

Lead wires crossing the track should be protected using suitable methods to prevent damage and ensure reliability of the connections.

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Bond Wires

Bond wires/rope wires are critical for electrical conductivity between rails and should be of an approved type. Installation requires duplicates for safety and reliability.

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Bond Wire Installation

Bond wires/rope wires should be installed next to fish plates using bond wire clips and secured immediately.

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Rail and Bonding Resistance

The combined resistance of the rails and bonding (per 1000 meters) must not exceed 0.5 ohms for track circuits longer than 700 meters.

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DC Track Relay Interchange

DC track relays are periodically swapped to prevent permanent magnetization.

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DC Track Relay Inspection

Quarterly visual inspection of DC track relays is performed, looking for issues like contact movement, arcing, and component flaws.

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Track Relay Defects

Defective track relays must be immediately replaced, and a report filed with senior management.

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Plug-in Relay Replacement

Plug-in type track relays should be replaced after 12 years, or sooner if needed.

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Insulated Rail Joint Maintenance

Maintenance of Insulated Rail Joints (IRJs) follows specific instructions, including pre-replacement component readiness and sleeper packing.

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Insulated Rail Joint Opening

Prepare replacement components before opening an Insulated Rail Joint.

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End-Post Replacement (No Gap)

Loosen rail fasteners, pull back the rail, and insert new end-post when replacing end-posts on an IRJ with no gap.

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IRJ Sleeper Packing

Insulated Rail Joints require proper packing of at least three sleepers on each side.

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Fish Bolt Tightening

Fish bolts in Insulated Rail Joints must be kept securely tightened.

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Single Rail Track Circuit Bonding

Series bonding of track circuit rails is crucial to prevent wrong side failures. It ensures the conductive path is interrupted if a connection is broken.

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Traction Return Rail Bonding

Traction return rails cannot be series bonded due to traction considerations. Bond disconnections must be avoided to prevent train shunt loss.

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Uninsulated Rail Cross Bonding

Uninsulated rails of adjacent tracks must be cross-bonded at intervals not exceeding 100 meters to handle high currents if an uninsulated rail breaks.

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Single Line Track Circuit Earth Wire

Single-line track sections need a continuous traction mast earth wire to handle traction return currents.

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Double Rail Track Circuit Connections

No structure bonds, cross bonds, or connections to earth wires are allowed on running rails where double rail track circuits operate (unless an impedance bond handles connections).

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Axle Counters

Devices that count the passage of axles, using different technologies (e.g., track circuits).

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Digital Axle Counter (DAC)

An axle counter using digital technology, often preferred over DC track circuits, especially on girder bridges.

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Intermediate Block Stop Signaling

A signaling system (intermediate signaling) that stops trains at an intermediate point

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Automatic Block Signaling

A type of signaling that automatically controls train movements within blocks and prevents collisions.

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Trolley Suppression

A system to prevent axle counters from registering trolleys, using either physical or electrical means.

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Installation Guidelines

The specific procedures and standards that the OEM (Original Equipment Manufacturer) follows to effectively install Axle Counters and related equipment.

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Pre-commissioning Checklist

A step-by-step list of necessary and/or recommended procedures prior to activating newly installed Axle Counters and/or components.

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Axle Counter Reset (Cooperative)

The procedure for resetting a failed axle counter, requiring cooperation between dispatching and receiving station masters to ensure the block section is clear.

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Reset Verification

Confirming the block section is clear of any obstructions before resetting the axle counter.

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Station Master (SM) Responsibility

Station Masters are responsible for physical verification using the Line Verification Box (LV box) for station sections with axle counters.

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Line Verification Box (LV Box)

A device used for physical verification of track sections near where a train is scheduled to pass.

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Train Signal Register (TSR)

A logbook used to record all operations related to resetting axle counters.

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Independent Reset Prevention

The system design prevents a station from independently resetting an axle counter to ensure proper coordination.

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Locked Reset Key

The key for operating the reset button is kept locked, ensuring authorized personnel perform the reset.

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Audio Frequency Track Circuit Operation Modes

Audio Frequency Track Circuits (AFTC) can be set up as either locally fed or remotely fed.

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AFTC Components

AFTC consists of tuning units, transmitters, receivers, power supplies, track connections, and impedance bonds (when needed).

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AFTC Installation Procedure

Adhere to specific guidelines for installing AFTC types.

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Tuning Area Requirements

The tuning area should be free of check rails, level crossings, insulated bonds, and each fish-plated joint must be bonded with adequate jumpers.

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Rail-Tuning Unit Connection

Ensure tight connections between the rail and tuning unit.

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Frequency Assignment

A pre-determined frequency assignment scheme for the track circuit must be followed rigidly.

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Terminal Junction Restrictions

Terminal junctions on insulated joints for track circuits with the same frequency are forbidden, but frequencies not part of the same pair can be used.

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Cable Core Restrictions

Do not use cable cores from the same cable to connect the transmitter and receiver of a track circuit.

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Wiring and Circuit Pairing

When wiring and installing, ensure conductors from the same pair are used for each transmission or reception in the line cables, ensuring minimal cross-talk.

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Field Equipment Design Considerations

Field equipment designs must accommodate planned mechanized maintenance and must not pose hazards for personnel working near the track.

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Atmospheric Surge Protection

Install protection against atmospheric voltage surges on each pair of conductors that connect to the outside to decrease the effects of lightning.

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Equipment Mounting

Mount transmitters, receivers, and power supplies in standard relay racks, allowing maintenance and testing staff to access and view the track circuit relays while they perform adjustments.

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Rail and Bond Resistance

The combined resistance of rail and bonding connections, should not exceed 1.5 ohms per 1000 meters for track circuits shorter than 700 meters.

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Track Circuit Termination

The point where a track circuit ends, typically located before the "Fouling Mark" to prevent train interference with circuit operation.

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Insulated Rail Joint

Sections of railway track where rails are electrically isolated from each other using special materials.

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Fouling Mark

A marked point on the track where the distance between tracks begins to shrink below the defined minimum distance.

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Multiple Track Circuit Indications

For berthing tracks with multiple sections, individual track circuit indications on the control panel are recommended.

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Station Line Status Indicator

Station indicators display yellow/white for unoccupied lines and red for occupied lines.

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Adjustable Limiting Resistance

DC track circuit limiting resistance must be adjustable and of an approved design.

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DC Track Relay Design

Approved design DC track relays should be utilized. Future installations should use plug-in type (9 ohm).

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Q Series Relay Pairing

Q series track relays should be used with Q series slow-to-pick-up relays as repeaters.

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DC Track Relay Excitation

DC track relays must operate at a minimum of 125% rated pick-up voltage with minimum ballast resistance and normal supply voltage.

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Maximum Relay Excitation

Maximum excitation for QBAT relays is 235%, and other plug-in types is 300%, based on specified conditions.

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Maximum Track Circuit Length

Maximum circuit length depends on track parameters (like ballast resistance and sleeper type).

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DC Track Relay Interchange

Periodically swapping DC track relays to prevent permanent magnetization.

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Jumper Connections

Connections in track circuits that electrically connect sections of track, excluding the traction return rail.

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DC Track Relay Inspection

Quarterly visual inspection of DC track relays to check for issues like contact movement, arcing, and component flaws.

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Ballast Resistance

Minimum electrical resistance of track ballast, measured in ohms per kilometer. Different values apply for station yards and block sections.

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Track Relay Defects

Defective track relays must be immediately replaced, and a report filed with senior management.

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Track Drainage

Proper drainage of water from railway tracks, crucial during rainfall to prevent track circuit issues or signal errors.

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Joint Inspection

Regular inspections of electrically isolated sections of track to assess rail and insulation quality, ballast condition, and drainage system efficacy.

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Plug-in Relay Replacement

Replace plug-in track relays after 12 years, or sooner if needed.

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Train Shunt Test

A test performed on the track circuit to verify proper operation and connections, done each quarter and during modifications/adjustments.

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Insulated Rail Joint Maintenance

Maintaining Insulated Rail Joints (IRJs) following specific instructions, including pre-replacement component readiness and sleeper packing.

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Insulated Rail Joint Opening

Prepare replacement components before opening an Insulated Rail Joint.

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Track Circuit Test Record

Documentation of track circuit performance readings to identify and address potential issues.

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End-Post Replacement (No Gap)

Loosen rail fasteners, pull back the rail, and insert a new end-post when replacing end-posts on an IRJ with no gap.

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IRJ Sleeper Packing

Insulated Rail Joints require proper packing of at least three sleepers on each side.

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Fish Bolt Tightening

Fish bolts in Insulated Rail Joints must be kept securely tightened.

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Impedance Bond

A device used to balance traction return current in audio frequency track circuits where a design does not provide built-in balancing.

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AC Impedance Bond Current Rating

AC impedance bonds can continuously handle 400 amps (200 amps per rail) with a peak of 1000 amps for up to 5 minutes.

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DC Impedance Bond Current Rating

DC impedance bonds usually handle significantly higher current than AC bonds.

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Impedance Bond Use on AC/DC Lines

DC bonds are often usable on AC systems due to their high current capacity, but AC bonds aren't suitable for DC systems.

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Impedance Bond Installation Considerations

Installation needs to account for track maintenance and safety for personnel walking along the track.

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AFTC Double Rail Configuration

Audio Frequency Track Circuits (AFTC) are configured as double-rail circuits requiring balanced rails with respect to earth and current flow.

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AFTC Impedance Bonding

Impedance bonds should be used to balance traction return current in audio frequency track circuits lacking design provisions for balancing.

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Distance between axle detectors

The minimum distance between adjacent axle detector pairs to minimize interference; typically at least 2 meters, or as specified in manufacturer manuals.

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Axle detector protection

Deflectors are needed to protect axle detectors from damage caused by moving trains' hanging parts. Single-line tracks need deflectors on both sides; double-line tracks, one side.

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Track side electronics location

Track side electronic equipment should be placed near axle detectors to minimize cable length and keep it below manufacturer recommendations. It should be above the flooding level.

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Cable distribution board

Incoming cables from axle detectors and evaluators should be terminated in a cable distribution board for testing, when applicable.

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Separate cables for coils

Transmitter and receiver coil cables between axle detectors and associated track side electronics should use separate conduits when possible, as per OEM standards.

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Sleeper spacing

Maintain a minimum of 400mm sleeper spacing to ensure correct placement & prevent vibration.

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Central power supply

Track side electronic equipment should run from a central DC-DC converter, preferable of approved type feeding the evaluator and having battery backup to maintain power.

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Evaluator Location

The evaluator should be in a secure, non-public location (e.g., relay room), elevated above flooding levels to prevent water damage. Should be kept away from electromagnetic interference.

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Study Notes

Track Circuits General

  • Track circuits use closed-type systems to detect train clearance.
  • Double rail track circuits are used in non-RE areas, while single rail DC for RE and double rail for AFTC are used in RE areas.
  • Track circuits must cover at least two rail lengths (26 meters).
  • Minimum circuit length is determined by the maximum wheelbase of any vehicle.

Permanent Way Requirements of Track Circuits

  • Glued/insulated joints define track circuit boundaries.
  • Glued joints should be inspected before installation.
  • Staggered joint spacing should not exceed minimum vehicle wheelbase.
  • Rail ends of joints should be square and true.
  • Fish bolts at joints must be tight, and sleepers well-packed.
  • Proper drainage to avoid flooding during rain is essential in yards.
  • Ballast should be kept clean around rails and fastenings.
  • Clearance from rail foot to formation level should be at least 50mm.

Location of Track Relays

  • Locate relays at the entry end of track circuits, whenever possible.
  • If relays cannot be located in the cabin, use an approved location.
  • Mount relays on vibration-reducing surfaces (e.g., rubber pads, foam).
  • Wire connections follow approved diagrams, incorporating cross-protection and double cutting.
  • Use separate cables for feed and relay ends.

Track Circuit Terminations

  • For track circuited points or lines, terminations should be sufficiently before the Fouling Mark.
  • The distance from the termination to the Fouling Mark should not be less than 3 meters.
  • In cut section track circuits, track relays are de-energized to open track feed and shunt the circuit.
  • Insulated rail joints should be used in accordance with standard guidelines.

Track Indicators

  • Track indicators show no light when lines are unoccupied.
  • If action is initiated, indicators show yellow/white (for unoccupied routes) or red (for occupied lines).
  • Panel interlocking/route relay indicates track clearance until sub-route/route is released.
  • For berthing tracks, individual track circuit status indicators are desired.
  • Track indicators show yellow/white for unoccupied lines, and red for occupied lines.

Track Relays

  • Use DC track relays of approved design.
  • Plug-in type relays (9Ω) are preferred for new installations in Non-RE and RE areas.
  • Use Q series track relays together with Q series slow relay for repeaters.
  • Excitation of DC track relays shall not exceed 235% for QBAT and 300% for other plug-in type relays.
  • Maximum track circuit lengths depend on different parameters (table provided in the text).

Track Feed

  • Use approved secondary cells for track circuits, with battery chargers/solar panels.
  • Provide a separate feed for each track circuit.

DC Track Relays

  • Maintain pick-up and drop-away values within manufacturer's specifications.
  • Inspect track relays quarterly for armature/contact carriage movement, contact arcing, dust, corrosion, cracks, and fungus.
  • Defective relays should be replaced immediately, with a report submitted to authorities.
  • Replace plug-in type relays after 12 years, or as condition warrants.

Insulated Rail Joints

  • Follow RDSO instructions for insulated rail joint installation.
  • Use "J" type clips.
  • Avoid hammering fish bolts, maintain correct alignment.

Bond Wires/Rope Wires

  • Use approved bond wires/rope wires.
  • Duplicate wires should be close to fish plates.
  • Secure wires by clips, drilling holes or brazing.
  • Resistance per 1000 meters should not exceed 0.5 ohms (for tracks more than 700 meters), up to 1.5 ohms for tracks less than 700 meters.

Stretcher Bars and Point Rodding Connections

  • Conduct periodic checks of insulation for stretcher bars/point rodding.
  • Replace defective insulation.

Ballast

  • Ballast resistance per km should not be less than 2 ohms in station yards, 4 ohms in block sections.

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Related Documents

CH 17. Train Detection Track Circuits & Axle Counters PDF

Description

This quiz covers essential concepts related to track circuits used in railway systems. Learn about the components of track circuits, including their requirements, types, and proper installation practices. Test your knowledge on the key aspects that affect train clearance and safety.

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