Railway Signal Engineering

Siding Points on Passenger running lines outside station limits:- Facing Points:-SEM-7.4.12 1)  The siding points on passenger lines outside the station limit shall be detected for permitting speeds of up to 50 kmph in facing direction.In case the detection is not provided, speed restriction of 15 kmph shall be imposed. 2) Where Siding Points are provided only with the minimum equipment specified in Para no. 7.4.12 (a), an appropriate speed limit over the facing points imposed for all trains passing over such Points in the facing direction only and an 'S' marker at the Points and a speed indicator at not less than 30 meters from the Points shall be provided, neither of which, need be lighted.  3) In addition a caution and termination indicator shall also be provided . If the sanctioned speed of the section does not exceed 50 kmph, the S 'Marker' at the points and the indicators need not be provided. 

  Catch Siding is provided to protect the station section, if the gradient is steeper than 1 in 80 falling towards the station section. Slip Siding is provided to protect block section if the gradient is steeper than 1 in 100 towards Block Section. Normal permissible gradient for Block Section is 1:1200 and for Station Section is 1:400. Reception of Trains in Catch Siding Stations- (a) Either a minimum of two Stop Signals shall be provided in rear of the Catch Siding points or the First Stop Signal shall be at an adequate distance equal to Block overlap from the catch siding points. (b) A train shall first be brought to a stop at the First Stop Signal, before the Catch Siding points are set for the main line and the reception signals shall not be taken 'OFF' unless the following conditions are satisfied. (1) The line on which the train is to be received is clear and the train is to be received on the main line.  (ii) The points leading to the Catch Siding as well as all the Poi

  Number of contacts in a circuit shall not exceed 45 Nos,due to voltage drop consideration.The voltage across R1 & R2 of a relay shall not be less than 22 V.

  Important facts   -  1. There should be no change in gradient within 30 m in case of BG and 15 m in case of MG of the point. 2. For IRS point Stroke is 143 mm and  opening is 115+_ 3mm.For IRS clamp type point machine maximum stroke is 220 mm. 3. For TWS Point stroke is 220 mm and opening is 160 mm.Tolerance is not mentioned anywhere. 4. Clearance of check rail ( Wing Rail) on crossing is 44 mm to 48 mm. 5. Chipped/ Cracked Switch -  Chipped length is the portion where tongue rail has worn out for a depth of more than 10 mm over a continuous length of 10 mm.If the total  chipped length is 200 mm within 1000 mm from toe of switch rail, this switch rail will be called Chippped Switch. 6.  Knife Edged tip- If thickness of tip is less than 2 mm over a length of  more than 100 mm anywhere upto a distance of 1000 mm from its toe, then it is knife edged tip. 7. Vertical wear - It is measured at a point where tongue and stock rail are at same level.Vertical wear  allowed is 8 mm for 60 kg IR

  In TWS Point,Distance between tongue rail and stock rail at JOH is 60 m.This distance is 25 mm in IRS Point.When train moves on Point,it does some lateral movement.Due to this larger gap at JOH in TWS Point,wear and tear in wheel and tongue rail is very less compare to IRS Point. TWS fitting are made for high speed (160 kmph).Stroke of TWS Point machine is 220m. In IRS Point only closed switch is locked and Open switch is kept free but in TWS both switches are locked.Open switch is locked with Fish tail or clamp. TWS is not suitable if curve is more than 2 degrees.  In TWS Point, throw is 220 mm 220 mm = 160 (opening) + 60 (gap at JOH)  Operating Data as per IRS :S 24/2002 - Amandement No 1 Motor DC series split field. Throw of point machine -220 mm +4/-1 Time of operation (Max) -5.0 sec Current Consumption- <_ 5.5 Amp Rated Voltage- 110 V DC Max Throw -550 Kg Slipping load - <_ 700 kg Stalling load (min) - 1000 kg Threaded portion of Lock Rod is made of steel . SSD( Spring Set

  SLB ( shunting limit board) It is used in single line B class Station working in Absolute block system, where Advanced Starter is not provided and Shunting is permitted in front of Approaching train.Its distance is 180 m ahead of Home Signal and it is facing towards station.A white light on the board will lit both in day and night Shunting in face of approaching train can be done only upto SLB.                  Dimension of rectangular board is 600 mm×1000 mm.Height of the bottom of rectangular board is 2 m from rail level .On the post there are alternate band of Black and White, each 300 mm wide. BSLB ( Block Station Shunting Limit Board)   It is used in double line B class station worked on absolute block system and placed 180m  ahead of home Signal when first point is trailing or there is no point. BSLB should be placed near Fouling Mark of the first point .Legend is facing towards station. A white light on the board will lit both in day and night. Other Indication Boards An ind

  Station Limit - Area Between outermost points of Station.In Single line, it is from UP Distant Signal of  to DN Distant Signal. In Double line , it is from DN Distant to DN Advanced Signal and UP Distant to UP Advanced Signal. Block Section -  In single line area between Advanced Starter of other Station and Home Signal including overlap is Block section. In Double line area between Advanced Starter Signal of other station and Home Signal including Block Overlap  Station Section - Other than block Section is  Station Section

  Automatic Block System  A) Automatic Block is a system in which movement of trains is controlled by the stop signals which are operated automatically by passage of trains past the signals. B) The automatic stop signal which governs entry of train into an Automatic Signalling section is a multiple aspect colour light signal which is not dependent upon manual operation but it is controlled automatically by the passage of a train into, through and out of the automatic Signalling  section which the Signal governs. C) The line between two adjacent crossing stations shall be divided into a series of signalling sections and entry into each signalling section shall be controlled by a manual stop signal or Automatic Stop Signal which must assume ON position on entry of a train into the section and be maintained in that position until the train has passed clear of the next Automatic Stop Signal in Advance and also for an adequate distance beyond it.  D) No automatic signal shall assume OFF p

  A warning board is to warn loco- pilot approaching a stop signal of a station.It is provided at a distance of 1.4 km in rear of the FSS. Where inter distance between two signals is less than the distance required for warning board, the signals in rear shall either be controlled by the signal in advance or both the signals shall be combined. Generally placed on left side unless there are special reasons to the contrary. Goods Warning Board  - Height of centre of circle of  goods warning board is 3.65 m from Rail level.The dimension of rectangular board is 1800× 530 mm.In Double distant terroritary, there is no need of this board. It gives a pre warning that either FSS  of a Station or IBS or Gate Stop Signal will come after 1400 m.This distance may be increased suitably to cater for gradients.Its post is alternate yellow and black. Detonator- When engine explodes detonator, Loco pilot shall whistle intermittently and take every possible caution including reduction of speed as necessar