Railway Signalling Concepts https://www.railwaysignallingconcepts.in Railway Signalling Concepts Tue, 07 Jul 2020 16:54:04 +0000 en hourly 1 https://wordpress.org/?v=5.4.2 Railway Signalling Train Stop Equipment Presentation https://www.railwaysignallingconcepts.in/railway-signalling-train-stop-equipment-presentation/ https://www.railwaysignallingconcepts.in/railway-signalling-train-stop-equipment-presentation/#respond Tue, 07 Jul 2020 19:59:20 +0000 http://www.railwaysignallingconcepts.in/?p=433 Railway Signalling Train Stop Equipment Presentation What is Train stop :    Train stop is a train protection device that automatically stops a train if it attempts to pass a signal at danger or (in some applications) if it attempts to pass at an excessive speed on the approach to all terminal and bay platforms . Raised (or effective) State (of trainstop) […]

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Railway Signalling Train Stop Equipment Presentation

What is Train stop :   

Train stop is a train protection device that automatically stops a train if it attempts to pass a signal at danger or (in some applications) if it attempts to pass at an excessive speed on the approach to all terminal and bay platforms .

Raised (or effective) State (of trainstop)

The Sttus of a trainstop such that it will not initiate a brake application on a train passing the trainstop. 

Lowered (or effective) State (of trainstop) 

The Status of a trainstop such that it will not initiate a brake application on a train passing the trainstop. 

 

Principle:

The trainstop system operates on the principle of a mechanical interface between track-mounted trainstop arm and vehicle-mounted tripcocks. When the tripcock on the train is deflected by a raised trainstop arm, it automatically initiates an emergency brake application.

 

Basic operation:

The train stop system comprises two basic components:

One is the trip arm mechanism, mounted on the ground adjacent to the rail, which essentially consists of a spring-loaded arm connected to an electric motor.

 

Train Stop

 

The other is the train-mounted trip cock, which is connected either directly or electrically to the train’s braking system.

 

 

When the signalling system determines it is safe for the train to proceed, the motor drives the trip arm down to the lowered position. The spring ensures that the trip arm is raised in all other situations. If a train attempts to pass the signal with the trip arm in the raised position, the trip arm makes mechanical contact with the trip cock on the train, causing the train’s brakes to be automatically applied, thereby bringing the train to a halt.

Wayside trip arms are adjusted so that they rise to a point approximately 2½ inches (about 6 centimetres) above the top of the running rail when in the stop position, and lower to approximately 1 inch (2.5 centimetres) below the top of the running rail when clear.

The time taken for the arm to rise or be lowered is approximately two seconds.

 

 

 

Types of  Trainstops:

There are three types of train stops:

Trip stop stops train trying to pass red signal

Timed train stop stops train moving too fast

Fixed train stop prevents any trains from passing a point

Trip stops:

The trip arm is raised whenever the signal is not displaying a proceed aspect. If a train tries to pass the signal, the trip cock on the train strikes the raised trip arm and the train is brought to a halt. When the signal indicates it is safe to proceed (clear or caution), the trip arm is lowered, and a train is able to proceed without further hindrance. In some cases, the trip arm will not be lowered when the signal to which it applies is exhibiting a proceed indication, e.g. when subsidiary signals are cleared, forcing a train to trip before proceeding, thus ensuring that movements are conducted at safe speeds.

Timed train stops:

With a timed train stop, the trip arm stays raised when the train approaches at a speed higher than the one that is set and trips the train to a stop. If the train approaches at a speed equal to or lower than the set speed, the trip arm lowers before the train arrives, and the train is able to proceed without further hindrance.

 

Fixed train stops:

With fixed train stops, the trip arm cannot be lowered. Fixed stops are positioned close to the end of a dead-end track, to stop a train before it runs out of track. They may also be used at the end of track sections beyond which certain trains should not pass e.g. storage sidings.

 

Mechanichal Working Of Trainstop:

When a signal displays the proceed aspect the trainstop head is lowered from the raised position by air being admitted to a cylinder. This action is common for all trainstops, which causes the head to lower to a position below the train tripcock line. This lowering of trainstop head also applies compression to a spring or springs which are part of the trainstop mechanism. The head is maintained all the time in lowered position when signal displays proceed aspect.

When signal returns to danger the air supply is removed from the cylinder, the compressed spring or springs then mechanically force the head back to the raised position.

 

Mechanichal Types Of Trainstop:

LER    ( London Electric Railway)

DR      ( District Railway)

CLR    ( Central London Railway)

“H”O  ( “H” outside)

“H”T   ( “H” Tube tunnel)

“J”      ( Outdoor type self lubricating)

“K”     ( Tube tunnel type self lubricating)

 

Railway Group Standard

GERT8018 Iss 2_mechanical trainstop

 

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What is Railway Level Crossings?  https://www.railwaysignallingconcepts.in/railway-level-crossings/ https://www.railwaysignallingconcepts.in/railway-level-crossings/#respond Tue, 07 Jul 2020 19:21:09 +0000 http://www.railwaysignallingconcepts.in/?p=2602 Railway Level Crossings  Railway Level Crossings :- Level Crossing:- An intersection at the same elevation of a road footpath or bridleway and one or more rail tracks. Strike-in point:- The position on the approach to an automatic level crossing or other  installation at which a train initiates the warning or closure sequence. Warning Sequence:- The order in […]

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Railway Level Crossings 

Railway Level Crossings :- Level Crossing:- An intersection at the same elevation of a road footpath or bridleway and one or more rail tracks.

Strike-in point:- The position on the approach to an automatic level crossing or other  installation at which a train initiates the warning or closure sequence.

Warning Sequence:- The order in which the visual and audible active warning devices operate as a train approaches a crossing.

 

Warning Time:- a) The shortest time for a train to travel from the point where it is the first visible or the time when the audible warning given by a train is heard at the crossing to its arrival at the crossing – applied to a user worked crossing or a footpath crossing where whistle board is provided.

b) The shortest time for a train to travel from the strike-in point to the crossing – applied to an automatic crossing.

 

Decision Point:- This applies to user-worked crossings, footpath crossings and bridleway crossings.

It is a point where guidance on crossing safely is visible and at which a decision to cross or wait can be made in safety.

For footpath crossing this should not be less than 2m from the nearest running rails or 3m the speeds are higher than 160 Km/h.

For bridleway crossings and user worked crossings this should not be less than 3m from the nearest running rail.

Footpath Crossing:-  A public or private pedestrian level crossing.

Open Crossing:- A level crossing that has no barriers, gates or road traffic light signals and which is protected only by road traffic signs.

User-worked Crossing:- A level crossing where the user operates the crossing gates or barriers themselves.

AOCL:- Automatic open crossings, locally monitored, are equipped with road traffic light signals, but barriers are not provided. An audible warning is provided for pedestrians.  New AOCL are not permitted by GI/RT7011.

 

     Principles:-   Where a right of way crosses the railway at track level, appropriate arrangements should be provided to warn and protect level crossing users, and safeguard the railway. This document also supports HM Railway Inspectorate safety principle.

     Control Measures:- The required control measures are :-

  1. a) Barriers (lifting barriers, gates and stiles)
  2. b) Fixed signs
  3. c) telephones to the signaller or crossing keeper
  4. d) active visible warnings
  5. e) active audible warnings.

Fixed signs and road markings:-At crossing equipped with white light indicators, instruction signs bearing the words ‘caution- cross only when light shows’ shall be provided/ Also signs shall be provided to indicate the name of Level crossings, both to crossing users and to railway staff.

Active visible warnings:- Where direct observation of approaching trains at a crossing for use by railway staff is inadequate for the safety of users, warning indicators, in the form of a white light shall be provided.

Active audible warnings:- At level crossings with full barriers controlled by staff, the audible warning shall commence when the road traffic light signals are illuminated at the commencement of the barrier lowering sequence and shall cease when all barriers are fully lowered.

At all other type of crossing provided with active audible warnings, the audible warning shall commence at the initiation of the warning sequence and shall be continue until all approaching trains have passed clear of the crossing. ex-AHBC. At such crossings where a second train approaches the crossing during the warning period for the first train, the audible warning shall change distinctively as soon as the first train arrives at the crossing. Number of audible devices shall not be less than two.

At footpath crossings:- it is permissible for an audible warning to be given by an approaching train, subject to a risk assessment. In such cases, whistle signs shall be provided.

Provision of AWS equipment:- AWS equipment shall be provided on the approach to all distant signals, distant board or level crossing warning signs associated with automatic crossing and crew operated crossings.

   

   Different categories of Level Crossings    

Gated Crossings

1. Gated crossings are suitable where traffic moment and actual daily road vehicle user are low.

2. At Gated crossings operated by railway staff, the gates shall usually be arranged such that when opened to the road they close across the railway. The gates shall complete the fencing of the railway when closed across either the road or the railway.

3. There shall be a means of securely retaining the gates in both open and closed positions. They shall be lockable in either position.

4. Generally, level crossing gate stops should be interlocked with the signals or routes reading over the crossing, including crossings up to 50m in advance of the signal ahead.

5. Railway signals interlocked with gates are required so that it is not possible to clear the signals unless the road is fully closed by the gates, nor is it possible to open the road unless the signals are ARAAFOAL.

 

6. Road traffic light signals may be provided but need not to interlock with the gates.

7.  Track locking should be applied by the track section(s) in which the crossing is situated, and route locking should be provided where necessary.

8. Gate stops in reverse position should release the gates across the road and secure them across the railway when their movement is complete.

9. Gate operating Mechanism should only be released from its normal position ( across the road) when gate stops are reverse.

10. Alternatively, the gate operating mechanism may be released by reversing a gate lock function which locks the signals and releases the gate stop function.

 

11. Gate operating mechanism may be mechanical (e.g. by wheel) or motorized.

12. Where gates are protected by road lights, the first action of signaller in preparing to open the gates to rail traffic should initiate the road light sequence. The lights should then operate for the required time and red lights should be proved alight before the gate can be released.

13. Detection of level crossings gates that are locked by gate stops or gate lock is not required.

 

OPEN CROSSINGS (OC)

1.  A level crossing that has no barriers, gates or road traffic light signals and which is protected only by road traffic signs.

2. The speed of the trains over the crossing should not exceed 15Kph.

3. There should not be more than one line over the crossing.

 

4. The maximum daily traffic moment not normally to exceed 2000 or the peak hour traffic moment 30 or the maximum actual daily road vehicle user 200.

5. The 85%ile road speed at the crossing to be less than 35 mile/h.

6. This type of crossing is only suitable for very lightly used applications.

 

USER-WORKED CROSSING (UWC)

1. The speed of trains over the crossing should not exceed 160 Kph unless special protection e.g. Miniature stop lights, Whistle boards and/or telephones are provided.

2. There are no limitations upon the frequency of rail traffic.

3. These crossings should only be used on private roads.

4. There should not normally be more than two lines over the crossing.

5. Where no additional protection is provided, the time required by users to traverse the crossing length to be at least 5 seconds less that the warning time available.

6. Where Miniature Stop Lights are provided, the warning period should be greater than time required by users to traverse the crossing length by not less than 5 seconds.

 

FOOTHPATH CROSSING & BRIDLEWAY CROSSINGS (FC & BC)

1. The speed of trains over the crossing should not be more than 160 Km/h otherwise additional protection like MSL, whistle board, telephones are required.

2. There are no limitations upon the frequency of rail traffic.

3. There should not generally be more than two lines over the crossing.

4. A level crossing for public or pedestrian, cyclists & horses.

5. Gates at bridleway crossings shall not be less than 1.5m wide.

6. Bridleway level crossings shall be protected by self closing gates on each side of the railway. The gates shall be arranged to open away from the railway.

7. Lifting barriers are not permitted.

8. LC gates shall be sufficiently high & robust to prevent the insertion of animals.

 

9. Footpath crossings shall be protected by either gates or stiles on each side of railway.

10. Gates on both side of railway shall have same type of access i.e. either gates or stiles on both ends.

11. The gates shall be arrange to open away from the railway.

12. Gates shall be easily opened by one person & shall be self closing.

13. Gates at footpath crossing shall not be less than 1.0 m wide.

14. The warning time should be greater than the time required by users to traverse the crossings.

15. Where MSL are provided, the warning time should be greater but not less than 5 sec than the time required by the users to traverse the crossing.

16. A gates shall be painted white and shall carry circular red retro-reflective facing towards users.

17. Gates shall also carry red lights, illuminated during night facing towards approaching road traffic.

 

MINIATURE STOP LIGHT (MSL)

MSL where provided on footpath and bridleway level crossing should be mounted on the far side of the railway facing towards oncoming users.

Approaching trains automatically initiate the warning sequence and change the light from green to red & sound the audible warning.

Where provided, audible warning should change in character when a second train approaches the level crossing.

The warning period should be at least 5 seconds longer than the time taken to traverse the crossing, subject to the following minimum requirements.

Footpath crossing  20 seconds

User worked & Bridleway crossings  40 seconds.

Failure of MSL units should not prevent normal operations of the audible warnings but should be indicated to the monitoring point.

Indication at monitoring point

White : Crossing functioning correctly.

Red    : The level crossing has failed.

 

Barrier Crossings operated by Railway Staff (MCB)

This type of crossing is generally suitable for any situation with permissible line speeds not greater than 200 KPH. Three categories :

MCB – Manually Controlled Barriers

MCB – CCTV – Manually Controlled Barriers supervised with the aid of Closed circuit Television.

TOB – Train crew operated Barriers.

At MCB and MCB-CCTV, railway signals interlocked with the barriers are required so that it is not possible to clear the signals unless the road is fully closed by the barriers, nor is it possible to open the roa unless the signals are at ARAAFOAL.

 

Manually Controlled Barriers

1. The barriers when lowered shall fully close the carriageway and footway on both sides of railway.

2. Two arrangements are permissible:

  1. a) a single barrier on each side of the railway, each barrier extending across the full width of the carriageway and footways,
  2. b) two barriers on each side of the railway, each barrier extending to the centre line of the carriageway.

3. If automatic lowering is employed, two barriers on each side of the railway shall be provided.

4. Where two barriers are provided on each approach, the barrier covering the left hand side of the road shall be lowered first. All barriers shall rise together.

 

5. Where single barriers are provided, they shall be pivoted on the left hand side of the road unless site constraints prevent this.

6. For each road approach, two barriers are normally provided. When closed to roadway boom is marked with alternate red & white stripes and carries two boom lamps showing red light in both directions.

7. Each road, the barriers meet at the centre of the road to close the highway fully.

8. Each approach is provided with two road signals. Each signal consists of two red lamps and a single yellow lamp.

 

9. When level crossing sequence is started , initially yellow lamps show for 3 sec, followed by red lamps flashing at 80 flashes/min. After 4-8 secs booms commence to lower. Once boom are lowered they are hydraulically locked.

10. The audible warning device will commence to sound as the sequence is started and will continue till all barriers are fully lowered.

11. Once it is safe to re open all barriers rise simultaneously.

 

Manually Controlled Barriers (MCB)

 

12. Manually operated barrier crossings are always provided with protecting signals to prevent the passage of train until the barriers are fully lowered and the crossing has been observed to be clear of road traffic.

13.  Track circuits are provided between the protecting signals and the crossing to prevent the barriers from being raised until the train has passed clear.

14. In certain cases, If a train overruns protecting signal at danger track circuits initiate the road signals, but barriers are not lowered.

15. Barriers can be lowered by the actions of the operator by pressing lower buttons on the control console.

16. Once the barriers are fully down, the operator has to ensure that enclosed road surface is unobstructed. Operator then presses crossing clear button.

17. It is then possible to clear the protecting signal.

 

18. At busy signal boxes, the barriers may be lowered automatically by the approach of the train.

19. In these cases the strike in point is set at such a distance from the crossing that it is possible to clear protecting signal in time to avoid the outermost distant signal from displaying a restrictive aspect.

20. When the barriers are fully lowered an alarm is sounded in signal box to remind the operator to verify and press crossing clear button.

21. Once the protecting signal has been cleared the barriers may only be raised once the signal is at danger and free of approach locking and all intervening track circuits are clear.

22. Raising can be manual or automatic raise can be selected.

23. In an emergency it is possible to stop either the lowering or raising of booms at any time by the operation of the stop button.

 

POSITIONING OF PROTECTING SIGNALS

1. Protecting signal shall be at least 50 m from level crossing.

2. Where level crossing lies immediately beyond a station platform it can be at 25m.

3. Protecting signal shall not usually be more than 600m from the crossing.

4. Protecting signal can be Non interlocked crossing only signal or Automatic signal with additional LC controls or fully interlocked signal.

5. Shunting signals are always fully interlocked . Shunting over the level crossing requires the automatic raise facility to be inhibited.

6. Shunting signals shall be positioned so that movements pass clear over the crossing before setting back.

 

MCB -CCTV

1. These are remotely operated barriers where operator has to view the whole of the enclosed road surface of the crossing by means of a closed circuit television system.

2. The CCTV usually consists of a single mast with duplicated cameras, the crossing being viewed on a single monitor with a second monitor available as back up. Either camera can serve either monitor.

3. The display of picture of the crossing by CCTV is obtained by pressing the picture button

4. On manually lowered installations the lower button for the barriers will not be effective unless a picture has been selected.

5. When automatic raising is selected the picture ceases to be displayed after the crossing clear button is operated.

6. If manual raise is selected , then the picture is displayed at all the times  whilst the barrier are down.

7. If the crossing is automatically lowered, the picture is displayed at the time lowering sequence is initiated and is extinguished by the operation of crossing clear button.

 

STANDARDS APPLICABLE FOR LEVEL CROSSING

  • GI/RT 7012 – GROUP STANDARD
  • GI/RT 7012 Issue One, August 2004 deals with requirements of Level Crossings.
  • RT/E/C/11600 Part X – LINE STANDARD
  • RT/E/C/11600 Part X deals with choosing the correct form of level crossing and design aspects of various kind of Level Crossings

 

 Watch Youtube Video :- https://www.youtube.com/watch?v=qV53vUiicT4

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Railway Signalling Track Circuit https://www.railwaysignallingconcepts.in/railway-signalling-track-circuit/ https://www.railwaysignallingconcepts.in/railway-signalling-track-circuit/#respond Mon, 06 Jul 2020 22:00:42 +0000 http://www.railwaysignallingconcepts.in/?p=809 Railway Signalling Track Circuit Introduction • A Track circuit is an Electrical circuit of which the running Rail of a Railway track forms a part. It is employed for indicating the presence of Trains and thereby for controlling Signalling and Block equipment’s. For the device Track circuit, following truly holds good. • ‘No single Invention […]

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Railway Signalling Track Circuit

Introduction
• A Track circuit is an Electrical circuit of which the running Rail of a Railway track forms a part. It is employed for indicating the presence of Trains and thereby for controlling Signalling and Block equipment’s. For the device Track circuit, following truly holds good.

• ‘No single Invention in the history of Development of Railway Transportation has contributed more towards Safety and Dispatch
Control in that field than the Track circuit. Track circuit forms the foundation for the development of practically every one of the
intricate Systems of Railway Signalling in use today wherein the Train itself is continuously active in maintaining its own protection’

• Track circuits are categorised as DC Track circuits, AC Track circuits and Electronic Track circuits (AFTC).

 

DC TRACK CIRCUIT

• Open Loop DC TC : The circuit gets completed when the track is occupied through the net resistance of the vehicle axles occupying the track circuit. The series resistance is so adjusted as to give sufficient voltage to the relay when track rails are shunted by axles. In this type of track circuit, if any connection breaks, its occupation goes undetected. Hence, it is used only for limited purposes where its failure does not lead to unsafe conditions.

Open Track Circuit

 

Closed Loop DC TC: In this track circuit, the series resistance is called a Regulating Resistance. It regulates the relay voltage so that it falls below the drop away value when the track is shunted. The fall is caused by increased voltage drop across the regulating resistance due to rise in circuit current when shunted by the vehicles.

DC Track Circuit

AC TRACK CIRCUIT

A.C. Track Circuits are provided exclusively in DC traction areas confined to Bombay Divisions of Western and Central Railways. It is possible to work A.C. Track circuits with A.C. traction also, provided the track circuit supply frequency does not have even a harmonic relation with the traction power frequency of 50Hz. 83 1/3 Hz frequency is chosen for this purpose and these track circuits are used in A.C. Traction areas including the places where DC electric traction ends and AC traction starts.

AC TC IS TWO TYPES:
1. Single Rail AC TC
2. Double Rail AC TC

The length of Single Rail Track circuit is permitted up to 500 metres. Maximum permissible length of Double Rail Track circuit is 2,300 metres. The cable lead Resistance at Relay end shall not exceed 12 Ohms irrespective of length of Track circuits. The feed end cable Resistance shall not exceed 12 Ohms for Track circuits of 2,100 and 2,300 metres and it can be progressively more with reduction of Track circuit length.

AC Track Circuit

 

AFTC

• The Audio Frequency Track Circuit (AFTC) is the Jointless type of track circuit
• specifically designed to meet the onerous immunity required in AC or DC electrified areas
• against the high levels of interference present mainly due to traction harmonics.
• The equipment is classified as universal since it can be used-in AC, DC or Non-electrified sections and meets all the requirements of the known track circuits.

SDTC

• The Smartway DTC is a solid-state, fail- safe system which performs, in a safe way, the train detection, rail continuity detection and track to train data transmission functions within a track circuit (TC) using audio frequency signals

Technical Specifications

• TC length: from 20 to 400 m;
• Transversal conductance: from 0 to 0.5 S/km (2 ohm∙km), LTC=400 m;
• from 0 to 1 S/km (1 ohm∙km), LTC=320 m;
• Maximum shunt resistance 0.5 Ohm;
• Overlap length 7 m (joint length);
• Maximum distance between SER and track connections
• 4.5 km if LTC=350 m, Ballast 0.5 S/km (2 ohm∙km);
• 2.0 km if LTC=400 m, Ballast 0.5 S/km (2 ohm∙km);
• 4.5 km if LTC=280 m, Ballast 1 S/km (1 ohm∙km);
• 2.0 km if LTC=320 m, Ballast 1 S/km (1 ohm∙km)
• Cable type 2×1.5 mm2, 40 nF/km, shielded;
• Data transmission speed: 400 bit/s for train detection;500 bit/s for Sacem;
• Rail continuity control throughout track circuit; Yes
• Maximum number of points in TC 2;
• Power supply 220 Vac ±10% at 50 Hz to 60 Hz;
• Temperature range -25°/+70° in the SER; -40°/+80° in the field;
• Frequency carriers (8nos.) 9.5-11.1-12.7-14.3-15.9-17.5-19.1-20.7 kHz;
• Modulation: MSK ±100 Hz at 400 bit/s (Digicode TC)
• : CPFSK ±100 Hz at 500 bit/s ( data);
• Vital Output 12 Vdc on 400 W or 24 Vdc on 1600 W, insulation 1000 Vac;
• DOT 24 Vdc on 1500 W, insulation 1000 Vac;
• Diagnostic RS232 front or RS422/485 rear connector, at 9600 bit/s, packet
• data protocol.

Block Diagram

 

Frequency and codes arrangement

 

Frequency and codes arrangement

 

Electrical Joints

 

Electrical Joints

Electrical Joints, S-Bond

Electrical Joints, S-Bond

ELECTRICAL JOINT, TYPE: S BOND

ELECTRICAL JOINT, TYPE: S BOND

Electrical Joints:terminal Bond

1.Single rail insulation :- Terminal bond allows to delimit the track circuit at a boundary with an Insulated Rail Joint as shown on
Figure The traction current can continue on the next track circuit by flowing through the terminal bond.

 

2. Double rail insulation :- Terminal bond allows to delimit the track circuit at a boundary with an Insulated Rail Joint on both rails as
shown on Figure.

Double rail insulation

 

ELECTRICAL JOINT, TYPE: DOUBLE ALPHA (TERMINAL ) BOND

ELECTRICAL JOINT, TYPE: DOUBLE ALPHA (TERMINAL ) BOND

INSULATED RAIL JOINT

Electrical Joints:Short circuit Bond

Short circuit bond At a boundary with an area without track circuit, a short circuit bond can used as shown on Figure
This configuration does not require any Insulated Rail Joints but the draw back is a dead zone whose length is in relation with the limit shunt value.

 

SDTC principle

SDTC : specific installation : S Bond in crossing

 

 

Railway Signalling Track Circuit, DC TRACK CIRCUIT,Open Loop DC TC, Closed Loop DC TC, AC TRACK CIRCUIT,Single Rail AC TC , Double Rail AC TC, AFTC , SDTC, Technical Specifications, Frequency and codes arrangement , Electrical Joints, S-Bond,Electrical Joints,ELECTRICAL JOINT, TYPE: S BOND , Double rail insulation,ELECTRICAL JOINT, TYPE: DOUBLE ALPHA (TERMINAL ) BOND, INSULATED RAIL JOINT , Electrical Joints:Short circuit Bond,SDTC : specific installation : S Bond in crossing 

 

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Railway Direction Indicator  https://www.railwaysignallingconcepts.in/railway-direction-indicator/ https://www.railwaysignallingconcepts.in/railway-direction-indicator/#respond Mon, 22 Jun 2020 22:30:40 +0000 http://www.railwaysignallingconcepts.in/?p=968 Railway Direction Indicator  Railway Direction Indicator :- •Direction Indicator is a display along the track side at critical locations that informs the train operator of direction of the path ahead.   • This indicators display a text sign based on a command the system management center. The text will indicate the next route as being a mainline […]

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Railway Direction Indicator 

Railway Direction Indicator :- Direction Indicator is a display along the track side at critical locations that informs the train operator of direction of the path ahead.

 

• This indicators display a text sign based on a command the system management center. The text will indicate the next route as being a mainline move or a depot/shunt move. However they do not indicate that the approaching train has been authorized to proceed along the indicated route.

• Direction Indicators will be provided at locations in which a non- passenger move and a passenger move may be made and at branches.

 

• Direction Indicator is a display provided at facing points where there is a move for which it is necessary, for operational purpose, to indicate the route to be taken to the train operator.

• The SMC will provide the route information via the PLC non-vital outputs to the DI in order for it to illuminate.

 

• The SMC will remove the output indication to the direction indicator when the train has been reported as having passed the direction indicator.

• It is visible to the train operator when the train is stationary.

 

• The aspect displayed shall be Lunar white.

• Mixed Mode Area: At locations where a Direction Indicator is required, and there is a shunt signal(or) main signal required for Metropolitan line trains, both will be provided. This is to give consistent operational instructions to TBTC train driver regardless of location.

 

• The applicable DI will be blanked if the next destination on a SMC route assignment passes through a SCS region where the SCS is operating in DMC or LCP mode.

 

• All the DIs associated with a VCC will be blanked if the communication between the VCC and SMC is severed.

• When RS sign is illuminated, then DIs will not be lit, If the RS and DI are located in the same post.

 

DIRECTION INDICATOR

 

DIRECTION INDICATOR

 

TYPES:

Two series of DI units are required, they are
1. Open section and

2. Tunnel section.
DI Symbol shown in SSP:

DIRECTION INDICATOR

 

 

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Railway Point Circuit https://www.railwaysignallingconcepts.in/railway-point-circuit/ https://www.railwaysignallingconcepts.in/railway-point-circuit/#comments Mon, 27 Apr 2020 22:03:22 +0000 http://www.railwaysignallingconcepts.in/?p=1366 Railway Point Circuit Introduction To re-cap The Controlling Lever The Point Control circuit The Detection circuit The WL Control circuit The Lever Lock circuit The Indication circuit Point Detection The P&LD Box The Three Position WKR Railway Point Circuit Railway Point Circuit Introduction  The majority of points used on London Underground are pneumatically operated, the most […]

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Railway Point Circuit Introduction To re-cap The Controlling Lever The Point Control circuit The Detection circuit The WL Control circuit The Lever Lock circuit The Indication circuit Point Detection The P&LD Box The Three Position WKR

Railway Point Circuit

Railway Point Circuit Introduction 

The majority of points used on London Underground are pneumatically operated, the most common types being Four Foots, Chair locks and Clamp locks.  On the Central Line, electrically driven points such as M63’s and HW1000’s are used as there is no compressed air main supply available. In some areas, Four Foot and Chair lock points have had their pneumatic motors replaced by electro-hydraulic units. The control circuits vary slightly from air worked points; however, the principles remain pretty much the same.

This Unit will deal with all the circuits associated with air worked Four Foot, Chairlock and Clamplock points controlled from a ‘V’ style lever frame. The circuit principles also apply to the older ‘N’ style frames even though these circuits differ very slightly, explanations areoffered in the relevant sections. The circuitry associated with all air worked points over which passenger trains can run are derived from the Basic Principles looked at in Unit 1.

To re-cap, these are as follows:

1. A means of moving the points to one of two positions (either Normal or Reverse)

2. A lock to hold the switches in the required position (Facing Point Lock, this requirement is achieved mechanically).

3. Detection of both the open and closed switches and the FPL

4. A means of preventing the points being moved when a train is upon them (Track Locking)

In addition to these principles, extra circuitry is needed to operate and detect the WL if it is fitted to the points.

An electric lock should be fitted to the controlling lever to prevent the points being thrown when a train is occupying the associated track circuit(s). An extra circuit that needs to be added is some form of visual indication of the position of the points.

If the controlling frame is a manual type then the indication is mounted on the frame to inform the signal operator of the point’s position. If it is a remotely controlled frame then the indications will be found on the equipment room line diagram.

Point Circuit

 

The Controlling Lever

The ultimate control of the points is effected from the point lever which is situated in the relevant IMR or signal cabin. The point number corresponds with the lever number as discussed in Unit 1 section 1.2. All levers, regardless of their function, proscribe an arc of 60º from the fully Normal to the fully Reverse position and back again. Fig 1.1 shows how this 60º arc is broken up into distinct angular positions which correspond with the letters N-A-B-C-D-E-R to represent these angles.

The lever shaft has contacts attached to it, known as lever bands, which are designed to electrically bridge the contact fingers as shown in Fig 1.2, and make up circuits when the lever is in a certain position. For example an NC lever band will make contact with its respective fingers when the lever shaft is within the NC arc as shown in Fig 1.1.  It can therefore be seen that the lever bands will make at different times and electrically energise circuits in a certain sequence.

With point circuits, the main bands used are the N, NC, RC and R. The N and R bands are normally used to energise the point auxiliary valves. The NC and RC bands are used to energise the WL electro-pneumatic valve.

The Controlling Lever

We will now look at all the electrical circuits used with points. There are five different circuits and these are as follows:

1. The Point Control circuit.
2. The Detection circuit.
3. The WL Control circuit.
4. The Lever Lock circuit.
5 The Indication circuit.

 

The Point Control Circuit

The point control circuit controls the throw of the points. This applies to both the Normal and Reverse positions and fulfils the first basic principle. On Four Foot and Chairlock points, the valves are energised at all times allowing the air motor to hold the escapement slide fully home and locked. This in turn ensures that the point switches remain locked until the points are thrown the opposite way.

 The Point Control Circuit

 

Fig 1.3 shows a typical point control circuit. The outgoing control lines 33NW and 33RW are fed from the main 33W fuse via the Normal and Reverse contacts on the point lever shaft. The lever contacts are arranged so that only one can make at any one time, thereby only one of the point auxiliary valves can energise at any given time. For this to occur, the lever shaft must be either fully Normal or fully Reverse.

A fault in this circuit could lead to a situation where neither valve is energised. To prevent the points moving if this were to happen, the ‘D’ valve in the point auxiliary valve is designed to maintain air pressure to the points even when there is no electrical supply to either the NW or RW valves.

Point Detection

Before a passenger train can pass over a set of points under a signalled move they must be electrically proved to be in their correct position and locked. In the case of Four Foot points there is a single point and lock detector box (P&LD) connected to the escapement slide and both point switches.

This box usually contains six contacts (6 way), three for the Normal detection and three for the Reverse detection. The relevant contacts are made when the facing point lock (FPL) is proved in position, the open point switch is detected open sufficiently and the closed switch detected up to the stock rail within tolerance. This fulfils the third Basic Principle

If any of these three criteria are not met then all contacts in the box must remain broken. We are going to look at the main electrical components involved in the detection circuit, namely the P&LD box and the three position WKR, before looking at the detection circuits.

 

The P&LD Box

The Four Foot point equipment can be located on either the left or right-hand side of the negative traction rail. The position of the positive traction rail governs the type of layout to be used as the majority of the equipment should be at continuous rail potential; where possible the continuous rail is always next to the positive rail.

 The P&LD Box

Both diagrams are viewed from the tips of the switches looking in to the points.

There are two types of six way P&LD box available and are labelled according to the layout they are to be used with. A left-hand box is for a left-hand layout and a right-hand box for a right-hand layout. Although the boxes are functionally the same they are mechanically different and cannot be swapped.

In a Left-hand box the contacts are made (Normal or Reverse) when the radial arms and parabola ball are paraLLeL to one another.

 

In a Right-hand box the contacts are made (Normal or Reverse) when the radial arms and parabola ball are at Right angles to one another.

 

The contact numbering in the P&LD box changes according to the turnout of the points. Standing at the tips of the point switches, starting with the contact furthest away the labelling is as follows

 

The AN and BR contacts are used in the control of the WL valve. Contacts 1N, 2N, 3R and 4R are associated with the point detection circuit.

A little ditty to remember this is: I (R)(AN) to (L)ondon (BR)idge

(R)ight hand turnout (AN) is furthest. (L)eft hand turnout (BR) is furthest.

A summary of the contact labelling is shown below

contact labelling

All points are shown in the Normal position and viewed from the tips of the switches, facing the points.

 

The Three Position WKR

The detection circuit uses a three position Double Element Vane (D.E.V.) type relay which has two coils (‘Q’ & ‘R’) and twelve contacts (six Normal and six Reverse). Both coils operate at 100V A.C, the ‘Q’ coil being fed directly from a local bus bar and the ‘R’ coil via the P&LD box contacts. By altering the direction of the current passing through the ‘R’ coil the relay will drive either Normal or Reverse. When there is no supply to either of the coils, the relay returns to the mid-position, where all contacts are broken.

 The Three Position WKR

 

 

 

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RRI-Free wired Route Setting https://www.railwaysignallingconcepts.in/rri-free-wired-route-setting/ https://www.railwaysignallingconcepts.in/rri-free-wired-route-setting/#comments Tue, 17 Mar 2020 15:23:47 +0000 http://www.railwaysignallingconcepts.in/?p=2161 RRI Free wired Route Setting Combined Indication & control panel   Station Layout Point setting and locking sequence Availability of selected route Control table specifies the controls required for route setting Generally when route is initiated the following checks are made to confirm that the selected route is free to be called. Checks- 1. Points including […]

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RRI Free wired Route Setting

Combined Indication & control panel

Combined Indication & control panel

 

Station Layout

Station Layout

Point setting and locking sequence

Point setting and locking sequence

Availability of selected route

Control table specifies the controls required for route setting Generally when route is initiated the following checks are made to confirm that the selected route is free to be called.

Checks-
1. Points including overlap and flank points are either already set to the required position or free.
2. Directly opposing route not set.
3. Conflicting routes are not initiated.
4. Other routes of the same signal are not initiated.
5. Any other special conditions required.

Route Lock relays

1. Each route is provided with a pair of route lock relays NLR/RLR
2. NLR is a magnetically latched relay(BR935) –
3. It is having two windings.

4. When route is released PU winding gets feed and relay picks up.
5. It gets latched in even after the feed is disconnected.
6. This is the normal condition and indicates the route is free

7. When route is initiated the other winding gets feed and the relay gets de-latched.
8. This prevents any other conflicting or directly opposing routes are being set. RLR is a neutral relay
9. RLR is a neutral relay, normally de-energised

10. Energises when the route is set.
11. De-energises when the route is released either by normalisation of route e or by TORR.

RLR/NLR circuit

1. Each circuit comprises two parts.
2. Left side of the coil called positive path.
3. Right side of the coil called negative path.

4. Push button commands (S)R & (D)R etc. are proved on positive path.
5. All route controls and special conditions are proved on the negative path.

Route controls are mainly three types –

Opposing Locking – opposing routes with same setting points. Front contacts of opposing routes and front contacts of opposing USR of route section past the signal are proved.

Point Selection  – all points in the route including flank points and points in overlap are either already set to the required position or free to move. other routes starting from the same signal are not locked out.

 

Route initiation circuit

Route initiation circuit

Route initiation circuit

 

Relays in point control

Relay Description
Point NLR Normal Point Lock Relay.  Magnetically latched relay BR935.  point RLR to be de-latched first for latching NLR. When latched calls the point for Normal operation.
Point RLR Reverse Point Lock Relay.  Magnetically latched relay BR935.  point NLR to be de-latched first for latching RLR. When latched calls the point for Reverse operation.
WZR ↓ Points free relay. Slow to release relay BR934. Must be energised to unlatch point NLR and point RLR. De-energised whenever the points are called by route or individual point relay.
NKLPR Points set, Locked and detected Normal
RKLPR Points set, Locked and detected Reverse
NZLPR Points set Normal or free to be set.
RZLPR Points set Reverse or free to be set.
NWKR Points set and detected Normal.
RWKR Points set and detected Reverse.

 

Point status

Points normal or free

Points reverse or free

Points normal and locked

Points reverse and locked

Point status

Points called to the required position

Points called to the required position

Point control and detection circuits

Point control and detection circuits


 

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RRI Button Circuit https://www.railwaysignallingconcepts.in/rri-button-circuit/ https://www.railwaysignallingconcepts.in/rri-button-circuit/#respond Tue, 17 Mar 2020 08:52:03 +0000 http://www.railwaysignallingconcepts.in/?p=2139 RRI Button Circuit  RRI Button Circuit :- points to be operated individually to the required position After points are set correctly, signal to be cleared.   Route setting system With a single action.  points initiated. points operated. route checked & locked and. finally signal cleared. Various route setting systems are in use. NX system is […]

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RRI Button Circuit 

RRI Button Circuit :- points to be operated individually to the required position

After points are set correctly, signal to be cleared.

 

Route setting system

With a single action. 

points initiated.

points operated.

route checked & locked and.

finally signal cleared.

Various route setting systems are in use. NX system is widely used.

 

Combined Indication & control panel (RRI Button Circuit) 

Combined Indication & control panel

 

Each signal is associated with a button.

Main signal is provided with a button colored red.

Subsidiary signal is provided with button colored yellow.

All buttons are spring loaded and they return to normal position.

when released after pressing/pulling.

A lamp is incorporated in the base of the button.

BUTTON SYMBOLS ON PANEL (RRI Button Circuit)

BUTTON SYMBOLS ON PANEL

 

BUTTON SYMBOLS

Button contacts

Button contacts  – M, F, FM,T, TM

Button contacts used for route setting and releasing

Normal – ‘C’ contact made

pressed – ‘F’ & ‘FM’ contact made

pressed and released – ‘F’ contact breaks & ‘FM’ contact made

pulled – ‘FM’ breaks

 

Button contacts

Button indications

First button pressed (at entrance signal) is recognized as entrance button.

Next button pressed (at destination signal) is recognized as exit button.

Entrance button pressed – white light starts flashing.

Exit button is pressed within the specified time – light becomes steady provided route is free.

If the exit button is not pressed within the specified time or the selected route is not free – flashing light ceases.

 

There is no physical interlocking between the buttons like in a Lever Frame.  So a button circuit is provided. Apart from route setting and route releasing functions, button circuit fulfills the following functions –

1. To avoid any conflicting route initiation, only one operation should be possible in a group.

2. To prove that pressing of entrance button is intentional that the exit button to be pressed within 7.5 seconds after the entrance button is released.

3. After entrance button is pressed, transfers the operation to exit button

4. Proves that wrong button is not pressed.

5. Proves that operation is completed and ready for the next operation.

 

Relays in route setting process

Relay Description
(F)R ↓ Energized when button pushed and drops when released. Provided for every button. BR960 Pin Code 212-2x 6F.2B
(FM)R↑ Drops out when button pulled and again energized when button released. Provided for every button. Double wound BR960 Pin Code 060-2x 4F.3B
PBCR↑ Energized when no button pushed in a group. Drops out when any one of the buttons pushed. One for each button ring. BR960 Pin Code 212-2x 6F.2B
PBPR↓

Energized when any button pushed and drops out when released. One for each push button ring. BR960 Pin Code 212-2x 6F.2B

TFR ↓ Transfer relay. Transfers the button operation from entrance to exit. Energized after entrance button pushed and released. Drops out with either exit button pushed within specified time or after a time delay. One for each button ring. BR931 Pin Code 023-12F.4B

 

Relay Description
(F)R ↓ Energized when button pushed and drops when released. Provided for every button. BR960 Pin Code 212-2x 6F.2B
(FM)R↑ Drops out when button pulled and again energized when button released. Provided for every button.

Double wound BR960 Pin Code 060-2x 4F.3B

PBCR↑ Energized when no button pushed in a group. Drops out when any one of the buttons pushed. One for each button ring.             BR960 Pin Code 212-2x 6F.2B
PBPR↓ Energized when any button pushed and drops out when released. One for each push button ring.  BR960 Pin Code 212-2x 6F.2B
TFR ↓ Transfer relay. Transfers the button operation from entrance to exit. Energized after entrance button pushed and released. Drops out with either exit button pushed within specified time or after a time delay. One for each button ring. BR931 Pin Code 023-12F.4B

 

Relay Description
DJR ↑ Clear time delay relay. Slow release with two capacitor slugs. Drops away one second after DCR drops, or 7.5 seconds after TFR picks. Drops away one second after DCR drops. One for each push button ring. BR934A Pin Code 063-8F.4B with H/O(D) 470 µF 330W & H/O(S) 3300µF 330 W .
Route NLR ↑

(Latched)

Normal (route) lock relay. Magnetically latched relay is up when the route is normal. To call a route this relay unlatches. Once unlatched, the NLR cannot re-operate until the signal is On and FOAL. One for each route. BR935 Pin Code 011-11F.4B
Route RLR↓ Reverse (route) lock relay. Ordinary acting neutral relay. Contains all the route controls. One for each route. BR931 Pin Code 023-12F.4B
NR↓ Normalizing relay. Energizes when route entrance button pulled or with TORR. One for each entrance button.
DZR↓ Destination invalid relay. Energizes when a wrong button is pressed. One for each push button ring. Energizes when route entrance button pulled or with TORR. One for each entrance button.

 

Route initiation –entrance selected

Route initiation

 

Route initiation circuits

Route initiation circuits

Route initiation circuits

Route initiation circuits 2

Time delayTFR, DCR, DZR CIRCUITS

TFR energizes after entrance button pushed and released.

DCR re-picks up after exit button released to indicate that operation is completed.

DZR picks up when wrong button pressed.

 

Time delayTFR, DCR, DZR CIRCUITS

 

Route initiation circuits

1. DJR drops away 7.5 seconds after TFR picks or one second after DCR drops.

2. DJR↓  releases (S)R & (D)R. Then (S)PR & (D)PR releases.

3. DJR hold switch in relay room is to hold  (S)R & (D)R for longer time for Testing.

Route initiation circuits 5

Route initiation destination selected

 

 

Route initiation destination selected

Route initiation – wrong button pressed

Route initiation - wrong button pressed

(D)R CIRCUITS

(D)R CIRCUITS

EGNR CIRCUIT

Auto Signals with  replacement facility, controlled from two locations.  F2R is same as (F)R

Double wound BR960 Pin Code 060-2x 4F.3B

 

EGNR CIRCUIT

 

Point switches or keys

Points are operated either by route initiation or by Individual point switches/keys.

Each switch/key is having three positions N, R and C.

During route setting process switch/key is kept in C (CR contact made)  position

 

Switch/Key operated to ‘N’ (NR contact made)- operates the point to Normal.

Point completes operation to ‘N’ even if it is brought  back to ‘C’ position subsequently.

Switch/key operated to ‘R (RR contact made) – operates the point to Reverse.

 

Point completes operation to ‘R’ even if it is brought  back to ‘C’ position subsequently.

Corresponding point indications are provided at point switch/key.

Individual signal operation is still possible if the points are available  in the required position, even if the switch/key is not in it’s ‘C’ position.

 

Point switches or keys

 

Route identification

When a signal is having more than one route – route on the extreme left as seen facing the signal 43 is identified  as ‘43A’. Next extreme left route will be ‘43B’

Where the route is having more than one class of route the class of route is identified by bracketed suffix.  e.g. 43A route is having main class, warning class, call-on, and shunt.

  43A(M) – main class-full O/L available.

   43A(W) – warning class – full O/L available.

   43A(C)  – Call-on class – berthing track occupied.

   43A(S) –  Shunt class used for shunting with PLGS.

 

Route setting

Route setting

Route setting

Signal RLR (RRI Button Circuit)

Energised when-

Points are initiated to set to the required position if not already set.

Points will move to the called position

After points are set to correct position and locked the detection relays NWKR/RWKR will pick up.

 

(S)PR & (D)PR CIRCUITS

(S)PR & (D)PR CIRCUITS

 

 

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Railway Route Release Circuits       https://www.railwaysignallingconcepts.in/railway-route-release-circuits/ https://www.railwaysignallingconcepts.in/railway-route-release-circuits/#respond Tue, 17 Mar 2020 08:14:25 +0000 http://www.railwaysignallingconcepts.in/?p=2106 Railway Route Release Circuits             Railway Route Release Circuits :- Approach locking Release of Approach locking as per GK/RT0063, para 4.2. Approach locking shall be released, after replacement of the signal to danger, either  by. the train passing the signal is detected such that the route or track locking is effective for the route ahead of […]

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Railway Route Release Circuits            

Railway Route Release Circuits :- Approach locking

Release of Approach locking as per GK/RT0063, para 4.2.

Approach locking shall be released, after replacement of the signal to danger, either  by.

  1. the train passing the signal is detected such that the route or track locking is effective for the route ahead of the train OR
  2. a reasonable assurance is obtained that any approaching train has come to a stand at or before the replaced signal OR
  3. 3. the proof of no train is approaching the signal

Approach/Route Locking – application

  1. Locking should be applied before the signal is allowed to show a proceed aspect.
  2. This can be either at the final stage or at the earlier interlocking stage.

 

Final Signal Control circuit

TPWS Train Protection and Warning System

 

Locking of route (General)

  1. Locking of Route is bifurcated into two parts –
  2. Approach Locking and
  3. Route Locking popularly known as Back locking.

 

Definition

The locking of any route from a signal including overlap beyond the exit signal, when the driver has seen or may have seen a proceed aspect at a signal that would indicate to the driver that the former signal is displaying a proceed aspect.

1. Approach locking can be two ways.  

2. Comprehensive approach locking.

3. Dead approach locking

Comprehensive approach locking is provided where necessary for operational reasons when the time delayed release of approach locking (Dead approach locking) would be detrimental to the working of trains.

 

Comprehensive Approach Locking

TAR (Train Approaching Relay) & ATSR (Approach Train Stick Relay) relays are used generated comprehensive approach locking, also known as look back circuitry.

TAR

  1. Basically the circuit proves all the track sections in the approach of the signal in rear are clear.
  2. Energizes during previous route release operation
  3. Remains energized till the signal is cleared again and the train is in the approach of signal.

 

ATSR –

  1. This relay amalgamates all the TARs associated with the signals in rear. Each signal’s ALSR in parallel with TAR should be selected by point lock relay contacts for any converging points.
  2. Normally de-energized.
  3. Energizes when signal cleared.
  4. Remains energized until train is with in the approach of sighting point of the last signal changing its aspect to a cautionary aspect.
  5. De-energizes with train is within the approach of sighting point of the last signal changing its aspect to a cautionary aspect.
  6. Again energizes on release of approach locking of signal in rear
  7. Remains energized till the system normalized.

 

ATSR

 

Both TAR & ATSR energised indicate, there is no train between this signal and the point in rear from which comprehensive approach locking is applied.

Route Locking – ALSR

  1. This is achieved by ALSR relay.
  2. This relay is normally in energized position indicating route is free.
  3. When route is set this relay de-energizes indicating the route is locked.
  4. This in turn de-energizes the sectional route locking relays (USRs)
  5. This relay remains in the de-energized condition until conditions for the route release are satisfied.

 

Route Locking

 

 Sequential operation of track circuits by passage of train

  1. the train passing the signal is detected such that the route or track  locking is effective for the route ahead of the train –
  2. this is achieved by sequential operation of track circuits ahead of the signal by the train. generally first & second track sections beyond the signal are chosen.
  3. ‘First & second track sections occupied, followed by first track section clear with second track section occupied.’
  4. Rest of the route is held locked by the occupation of track sections by the train.
  5. Each track section is released as the train clears that track section and moving ahead.

Route locking Release (Railway Rout Release Circuits)

Train-In-Section Proving

TASR (Train Approach Stick Relay) energises with the first two track sections occupied when route is locked.

Route locking Release

Route locking released with time

  1. A reasonable assurance being obtained that any approaching train has come to a stand at or before the replaced signal. This is ensured by proving the approach track occupied for time.
  2. This condition provides  a parallel path for ALSR to energise.

 

Section Route Release

  1. Where sectional route release facility is provided, USRs (Route Stick Relays) are provided for each track section.
  2. For each track section separate USRs are provided for Down and Up directions depending upon the requirement.
  3. When route is initiated NLR de-energises.
  4. With this all the USRs (Route Stick Relays) in the route get de-energised disabling the operation of any infrastructure in the route.

 

Approach locking (Railway Rout Release Circuits)

  1. Release of approach locking can be initiated in two ways –
  2. Manual request from the signaler in the form of pulling of the concerned signal button.
  3. Train passing the signal at OFF and continuing its journey.TORR

 

Train Operated Route Release (TORR) –

  1. TORR provided at the request of Network Rail.
  2. TORR is essential in case of Automatic Route Setting Systems.
  3. This eliminates the need for signalman to cancel the route after each train.
  4. TORR releases the only after the train entered the route.

Conditions for TORR to operate 

  1. The signal controls were OFF at the time the train passed the signal.
  2. Signal is disengaged and prevented from re-clearing after the train movement has taken place.
  3. The signal is not set to work automatically.
  4. The signalman has not initiated the release of route.
  5. Approach locking for the route has been released.
  6. Occupancy of two adjoining track circuits in the direction of travel followed by clearance of the first. OR
  7. Occupancy of three adjoining track circuits in the direction of travel followed by sequential clearance of two track circuits. OR
  8. Sequential train detection employing a treadle due to some limitation of track circuits. OR
  9. Proof of no train approaching the signal, at the time TORR operation, is satisfied where Comprehensive Approach locking is provided.
  10. Where Comprehensive Approach locking is not provided, one of the following conditions shall be satisfied –
  11. Occupancy of two adjoining track circuits in the direction of travel followed by clearance of the first. OR
  12. Occupancy of three adjoining track circuits in the direction of travel followed by sequential clearance of two track circuits. OR
  13. Sequential train detection employing a treadle due to some limitation of track circuits.

 

Control Table for TORR

  1. Control Tables specify the above three conditions as under –
  2. ‘Approach locking released by track circuits’ –  ordinary release condition when a train has   entered the route.  (Standard & Alternative   track sequences).
  3. Time release – shown in seconds.
  4. ‘Approach locking applied when signal clears’ and ‘Signals ON and free of approach locking’.

 

Approach locking shown in Control table

Approach locking shown in Control table

 

2 Red rule locking

Release of approach locking in case of 2 Reds rule –

In case of 2 Reds rule, the Approach locking is applied on setting of route. Therefore, back contacts in series of all the route RLRs for that signal are required to be proved in the un-conditional path of ALSR to ensure application of Approach locking on setting of any of the routes.

After passage of the train, when the signal gets replaces to ON, it should be possible to release the Approach locking. For this reason we need to provide an additional parallel path, bypassing all the RLR back contacts by GSR back contact. Further, in case of auto working facility, the GSR will not de-energise after passage of the train. So another bypass using TASR front contact needs to be provided.

There are instances when the approach locking needs to be made effective earlier than the signal controls off stage of the interlocking. In case of 2 Reds rule, the Full line speed Protecting Signal (FPS) aspect controls require either a ‘route set from the junction protecting signal(JPS)’ or ‘approach release from Red’ – in addition to other controls. Since one of the condition for clearance of the FPS is route set from the JPS, the Approach Locking of JPS will have to be made effective on route setting itself.

                                      

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Railway Use of Axle Counters Fouling Point Clearance point https://www.railwaysignallingconcepts.in/railway-use-of-axle-countersfouling-pointclearance-point/ https://www.railwaysignallingconcepts.in/railway-use-of-axle-countersfouling-pointclearance-point/#respond Tue, 17 Mar 2020 07:28:06 +0000 http://www.railwaysignallingconcepts.in/?p=2398 Railway Use of Axle Counters Fouling Point Clearance point Railway Use of Axle Counters Fouling Point Clearance point :- The Design requirements for train detection systems includes the following: Interface with authorized rail vehicles (positioning of IRJs, minimum track circuit lengths, which may be dependent on permissible speed, and interlocking measures to mitigate against any […]

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Railway Use of Axle Counters Fouling Point Clearance point

Railway Use of Axle Counters Fouling Point Clearance point :- The Design requirements for train detection systems includes the following:

  1. Interface with authorized rail vehicles (positioning of IRJs, minimum track circuit lengths, which may be dependent on permissible speed, and interlocking measures to mitigate against any deficiencies)
  2. Interface with permanent way (IRJs, standard rail bonding with pre drilling requirements and S&C bonding configuration)
  3. Interface with electric traction infrastructure (single or double rail configuration and impedance bond position)
  4. Interface with interlocking system (operating times and measures to mitigate against false release of interlocking when there is a significant risk)
  5. The requirement for secure power supplies and / or battery back up

 

Design Consideration for choice of train detection

  1. The need to detect vehicles on poor rail surface.
  2. The need or otherwise to avoid insulated rail joints.
  3. The need for immunity to AC and / or DC traction interference.
  4. The need to achieve maximum reliability at economic cost.
  5. The need to track circuit through complex S&C.
  6. The type of sleepers, where ballast resistance is critical.
  7. The length of a train may need to be measured.

Different types of train detection systems

1. Track circuits
2. Axle counters
3. Other type of wheel detector, e.g, treadle, electromagnetic proximity device(used for HABD)
4. Supplementary systems, e.g, track circuit assistor interference detector(TCAID), track circuit interrupter.

 

Key Attributes & Limitation of Track circuits

Key Attributes & Limitation of Track circuits

 

Use of Axle Counters 

Use of Axle Counters 

Fouling Point

1. This is a position a short distance away from the point of running line divergence (crossing nose). Should any part of a vehicle on one track be between the crossing nose and the fouling point, it will make physical contact with any vehicles passing on the other route.

2. The fouling point occurs where the distance between the running edges of the two rails is 1970mm, measured at right angles from the diverging line.

3. In the case where tracks become parallel with a running edge separation of less than 1970mm, the fouling point occurs where the tracks first become parallel.

 

Clearance point

Determination of clearance point :- Figure shows the relationship between the clearance point and the fouling point. In particular it depicts that the clearance point is determined by adding the maximum vehicle end overhang* allowed for a line and the allowance of 1600 mm. The allowance includes the roll back allowance of 1300 mm, which is provided to accommodate potential roll back after the train has come to a stand.

maximum vehicle end overhang :

  1. a) 5000 mm for new high-speed lines.
  2. b) 4200 mm for other lines.

 

Determination of clearance point

Determination of clearance point

 

 

 

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Railway Insulated Rail Joints https://www.railwaysignallingconcepts.in/railway-insulated-rail-joints/ https://www.railwaysignallingconcepts.in/railway-insulated-rail-joints/#comments Tue, 17 Mar 2020 07:10:17 +0000 http://www.railwaysignallingconcepts.in/?p=2391 Railway Insulated Rail Joints Railway Insulated Rail Joints :- Insulated Rail Joints (IRJs) are required to join together mechanically but no electrically. they are required for the follwing purposes: to define the limits of jointed track circuits, to provide insulation between rails at S&C, necessitating track circuit transpositions, where transpositions are required for other purposes, […]

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Railway Insulated Rail Joints

Railway Insulated Rail Joints :- Insulated Rail Joints (IRJs) are required to join together mechanically but no electrically. they are required for the follwing purposes:

  1. to define the limits of jointed track circuits,
  2. to provide insulation between rails at S&C, necessitating track circuit transpositions,
  3. where transpositions are required for other purposes,
  4. to provide traction return isolation.

The following shell be considered relative to IRJ Provision in S&C as constrained by permanent way engineering considerations:

  1. IRJs adjacent to cast crossings shall be avoided wherever practicable.
  2. IRJs, run over in the high speed route shall be avoided as far as practicable.
  3. There shall be a minimum distance of 200m between chair of rail fastenings of opposite polarity/phase to reduce the probability of failures due to metallic litter, etc.

 

 

Insulated Rail Joints

 

Insulated Rail Joints – Buffer Stops

Buffer Stop 

Rail mounted buffer stops in track circuits areas must be fully isolated, by one of the following means:

  1. Provision of an insulated design of buffer stop.
  2. Provision of ITJs in both rails, for a double rail track circuit, or
  3. Provision of an IRJ in the insulated rail, for a single rail track circuit.

in order to ensure detection of the shortest vehicle, the IRJs shall be located at 4m + 0.5m from the face of the buffer stop. the position of the IRJs for friction buffer stops shall be determined from figure F8. The type of IRJ must be of a design which offers similar tensile strength to conventional steel fish plates.

Insulated Rail Joints – Buffer Stops

 

 

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