Operating Manual-Traffic 80-88 PDF

INTERLOCKING (Back to Index) Definition: - Interlocking means an arrangement of signals, points and other appliances, operated from a panel or lever frame, so inter-connected by Mechanical locking or Electrical locking or both that their operation must take place in proper sequence to ensure...

INTERLOCKING (Back to Index) Definition: - Interlocking means an arrangement of signals, points and other appliances, operated from a panel or lever frame, so inter-connected by Mechanical locking or Electrical locking or both that their operation must take place in proper sequence to ensure safety. 1. Basic Principles: - The basic principles of interlocking are as follows: - v) It shall not be possible to take “off” conflicting signals at one and the same time. vi) It shall be possible to take “off” signal for a running line only when:- (a) All points on the running line are correctly set and facing points locked (b) All points, giving access to the running line from the sidings and goods lines, are set against the running line. (c) Level crossing gates if included or controlled by interlocking are closed and locked against the road traffic. (d) A signal lever when operated must lock or back lock as necessary the levers operating the points and gate locks referred to above. Once signal is taken off it shall not be possible to alter the points, to unlock the gate lever etc until all signals are taken off have been put back. vii) When all signals are in the “On” position, all points which would be locked by taking ‘off’ such signals must be free for shunting purposes/testing etc. iv) It must be impossible to take “off” a Warner Signal, until all the relevant stop signals in advance have first been taken “off” and when “off” it must back lock all such signals. a) Interlocking – Points, Signals and other units are usually, operated by means of levers and panels. Interlocking between these levers is accomplished either by mechanical or by electrical or electro-mechanical or electronic means. In the former method, some mechanical contrivance variously designed, controls the relation between one lever and the other. At less important stations the point, signal and other levers are interlocked by means of keys which are used to lock or release the levers, either in the normal or in the reverse position, as required. At other stations the levers are interlocked by means of tappets inside a box of the lever frame, which is normally kept covered and sealed. 3. Types of Interlocking: i) Mechanical Interlocking. ii) Panel Interlocking (Relay) iii) Route Relay Interlocking. iv) Solid State Interlocking. i) Mechanical Interlocking: The era of interlocking started with mechanical frames. In mechanical signaling, since the functions are operated by levers, the relationship that should exist between the functions can be transferred to exist between the levers. To ensure that the signal can be taken ‘OFF’ only after the point is correctly set, we can arrange the interlocking between the signal lever and point lever to be such that the signal lever can be reversed only after the point lever is in the correct position, viz. ‘Normal’ or ‘Reverse’, as the case may be. As the size of yards & train movements increased, size of lever frames also increased. These lever frames not only increased in size occupying more space but also required intensive maintenance. ii) Panel Interlocking: With the advent of Electro-mechanical relays, lever frames gave way to relay interlocking based installations. This development resulted in relatively faster operation, fail- safe operation and reduced size of buildings required for housing of interlocking installations. With further increase in traffic and expansion of railway network, panel Interlocking installations were commissioned. iii) Route Relay Interlocking: Route Relay interlocking is same as Panel Interlocking with Electro Mechanical Relays doing the Interlocking except that it can be employed for big yards. the interlocking is done between one route and another route. Another Important feature in terms of operating point of view is that the SM has to only press two buttons, Signal button & Route Button (entry-exit system). He doesn’t have to individually operate the points to the required position. iv) Solid State Interlocking (SSI): Computer based interlocking uses thousands of Electro-mechanical relays requiring complex wiring and Inter-connections. The wiring diagrams for such installations run into hundreds of sheets. Individual relays, wiring and interconnections along with thousands of shouldered joints are required to be physically examined and certified. This exercise requires traffic blocks of long durations and large manpower to manage the traffic during blocks. Even for small yard re-modelling like addition of a loop line, all the above activities are required to be redone. Therefore, the advantages of relay based interlocking installations are being nullified. The SSI system occupies considerably less space, consumes less power, is more reliable and is easy to install and maintain. Also, initial commissioning & changes due to yard re-modeling can be carried out in negligible time requiring skeleton manpower for traffic management during the blocks. Unlike PI or RRI, Microprocessors (IC’S) are doing the Interlocking based on pre determined logic circuits. Advantages of SSI:- Increase in section capacity. Faster operation. User friendly operation. Fail safe technique Multiple mode operation. Significance of SSI for operating staff: Reduces man power Centralised operation Multiple mode of operation Control cum indication panel Video display unit (P.C) CTC (Centralised Traffic Control)—permits remote control Significant reduction in traffic block time Easier & simple operation Indirect and Direct Interlocking: -  (a) Indirect interlocking means that the points are set and locked from one place and the signals are operated from another place and another lever frame; the interlocking is effected by means of keys carried from one place to the other. (b) Direct interlocking means that all levers, viz. the point, the point locks and the signal levers are concentrated in one lever frame and worked therefrom; the interlocking is effected by means of rigid connections between levers without the use of keys. Standards of Signaling and Interlocking: - Interlocking at stations is standardized into four different classes viz. I(R), II(R) ,III(III) and IV(R). The regulations prescribing the four standards have been drawn up primarily to meet the needs of crossing stations on the single line but, with such modifications as may be necessary in regard to the equipment of signals; these are also applicable to other stations both on single and double lines. The standards are as follows: - Note: - For details see para 170 to 174 of “Indian Railway Signal Engineering Manual”. Two aspect signalling. (a) Standard I.(R) (i) Speed - 50 kms. Per hour. (ii) Isolation - Isolation of the main line is recommended, but is not essential. (iii) Points - the facing points should be provided with key locks, locking both switches independently and the switches detected independently by relative signals. (iv) Interlocking - Interlocking between points and signals may be carried out indirectly by means of key locks. (v) Signals - Outers and Bracketted Home signals shall be provided. The provision of Starter signals is optional. Working Warners may be provided for metre gauge stations where trains run through, if considered necessary, but are not required for other stations signalled to standard I. (b) Standard II.(R) (i) Speed - 110 kms. per hour. (ii) Isolation of the main line is essential. (iii) Points - the facing points should be provided with plunger type locks, locking both switches independently and the switches and the bolt being detected independently by relative signals. (iv) Interlocking - The interlocking between points and signals may be direct or indirect. Where indirect interlocking is used, signals shall be worked from a position under the control of the Station Master and key must be provided to enable the Station M