Chapter 18: Block Instruments, Section 5-8 (PDF)

18.3.4 Earthing (a) A separate earth shall be provided for each instrument. The earth shall be of an approved type and should be buried at a depth of not less than1.5 meters and at a distance not less than 2.5 meters from any other earth. The resistance o...

18.3.4 Earthing (a) A separate earth shall be provided for each instrument. The earth shall be of an approved type and should be buried at a depth of not less than1.5 meters and at a distance not less than 2.5 meters from any other earth. The resistance of the earth should not be more than 10 ohms. Note: Separate earth is applicable for only those equipments which work on earth return. (This does not apply to block instruments which work on metallic return) Also the protective earth for SPDs of block instruments to be connected to common ring earth of Indoor Signalling system. (b) The length of the Earth wire shall be as short as possible and cross section of the wire not smaller than the size of the line wire and in any case shall not be smaller than 4 mm dia. The earth wire shall not have a sharp bend or spiral. Earth wire should be adequately protected from mechanical injury and be efficiently connected to the earth. All connections to the earth shall be well soldered. Section 4: Installation of Single Line Token Instruments 18.4.1 (a) The Token instruments shall be so installed that the token of one section cannot be placed in any other instrument at that station. It is also desirable that the installation be such that if the token is over carried, it cannot be placed in any instrument at the next station. (b) Consecutive block sections shall be provided with tokens of configurations A, B & C. Following block sections shall also be provided with similar configuration in the same order. Where a junction station falls in between or new crossing station is opened, tokens with special configuration (D&E) shall be provided. (c) Block Instruments must be mounted level (spirit level may be used) so that tokens will not get into any particular race in case of ball Token instrument and the token will not tilt in case of tablet type Token instrument. 18.4.2 Tests to be Conducted After Installation and Before Commissioning (a) Check that correct polarities are connected to the instruments at both the ends. (b) Check that all mechanical parts are free to move without undue friction and that there is no jamming of moving parts. (c) Check that the commutator does not change unless the token gets into the races in the case of Ball Token instruments and slides down the rail beyond the tablet receiver in the case of Tablet Token instrument. (d) Check that the insulation of electrical components and internal wiring of the block instrument is proper and free from leakage from the instrument body/earth. Note: RDSO Booklet STS/E/BTI/IMI may be referred to for detailed instructions regarding installation & testing. Chapter 18: Block Instruments, BPAC & IBS Working Page 364 of 530  Section 5: Installation of Single Line Tokenless Block Instrument 18.5.1 (a) The instruments shall be mounted level. The instruments shall be so placed as to have an easy access and space for their maintenance. (b) Before installation, the instrument shall be checked for the following: (i) Free from mechanical damage, corrosion. All nuts and bolts shall be secure and complete. (ii) The Front Panel shall be free from splitting, twisting or warping in case of Push Button type instruments. (iii) The seal of all the relays and counters shall be intact. (iv) Sealing. (c) All the external connections to the block instrument shall be removed and insulation resistance measured between individual insulated circuits and Earth. The minimum value between each individual insulated circuit and Earth shall not be less than 10 mega ohms. (d) Block release shall be by operation of two track circuits sequentially. 18.5.2 Testing of Single Line Tokenless Block Instruments (a) Check that the Last Stop Signal at the sending station cannot be taken 'OFF' until the receiving station instrument is set to "Train Coming From" condition and the sending station instrument is set to "Train Going To" condition. (b) Check that the Line Clear can be granted only when reception signals and the Last Stop Signal are proved at 'ON'. (c) Check that the Last Stop Signal is replaced to 'ON' by the entry of a train into the block section and the same is maintained in the 'ON' position until the train has cleared the block section and the instruments are brought back to the 'Line Closed' condition and fresh "Line Clear" is obtained. (d) Check that the opposing Last Stop Signals of the block section cannot be taken "OFF" at one and the same time. (e) Check that the circuit for proving the arrival of a train is directional. (f) Check that the shunting key can be taken out only when the instruments are in "Line Closed" condition or "Train Going To" condition. Chapter 18: Block Instruments, BPAC & IBS Working Page 365 of 530  Section 6: Installation of Double Line Block Instruments 18.6.1 (a) Quick acting relays shall not be used for stick circuits of the block instrument. Two immunized plug-in type 'Q' series relays connected in tandem or one 'Q' series slow to pick up AC immunized relay shall only be used. The total pick up time of relays used shall not be less than 300 msec. DC 3-position polarized line relay of approved type shall only be used in the line circuit for block working. (b) Block release shall be by the operation of two track circuits sequentially. 18.6.2 Tests to be Conducted at the Time of Installation (a) Check that the commutator handle is locked first before the "Train on Line" indication appears on the indicator when the handle is turned from "Line Clear" to "Train on Line" position. (b) Check that the Block Clearance Relay picks up only after the commutator is turned to "Train on Line" position. (c) Check that the Last Stop Signal cannot be taken 'OFF' when the commutator is in other than "Line Clear" position. (d) Check that the Last Stop Signal is automatically replaced to 'ON' when the train enters the block section and continues to remain in the 'ON' position until the train has arrived at the receiving station and a fresh “Line Clear” is obtained. (e) Check that when the commutator is turned from "Line Closed" position to "Train On Line" position, the commutator is free for return to “Line Closed” position. Section 7: Maintenance of Token Instruments - General 18.7.1 Register of Block Instruments The Senior Section Engineer (Signal) shall maintain a register containing the following information: (a) The type of instrument, its serial number, location, and name of manufacturer. (b) Date of installation. (c) Date of last overhaul. (d) Particulars of all tokens working in each block section and particulars of tokens either removed or lost irrecoverably during the course of working and of those introduced as replacement. 18.7.2 Census of Tokens: Each Sectional JE/SSE (Signal) shall take a census of the tokens working in various block sections at least once in six months and shall keep their record in the register of Block Instruments. He should also record this information in the Signal History Book at every station and keep it up to date in this respect. Chapter 18: Block Instruments, BPAC & IBS Working Page 366 of 530 18.7.3 Damaged Tokens (a) Tokens, which are cracked or deformed or have worn to a size smaller than the normal size or are damaged in any other way and are liable to jam in an instrument and cause a failure shall be removed, broken up and returned to Stores. Advice of tokens that have been removed shall be given to all concerned. (b) Token so removed shall be replaced with another token of the same number and all concerned advised. 18.7.4 Lost Tokens (a) When a token has been lost and cannot be found after a thorough search, a joint certificate to that effect shall be given to the Senior Divisional/ Divisional Signal and Telecommunication Engineer by the supervisors of the Signal and Telecommunication Department and the Operating Department. On receipt of the certificate, a joint circular shall be issued by the Senior Divisional/ Divisional Signal and Telecommunication Engineer and the Sr.Divisional Operating Manager giving full particulars and cancelling the lost token for the information of the staff. The particulars of the lost token shall be published in the Railway's Gazette. (b) Particulars of lost tokens on Card No. S&T/TL, as per Annexure: 18-A2 shall be conspicuously exhibited near the relevant instrument for the information of the Operating Staff. (c) If a lost token is not found for six months, it shall be replaced with a token of next higher number in continuation of the series in use on the section. The lost token, if found subsequently, shall be broken and returned to stores. 18.7.5 Balancing of Tokens (a) Technicians shall, whenever necessary, transfer tokens from the instrument in which they have accumulated to the instrument at the other end of the section. Each Technician in charge of single line token instruments shall be provided with a "Token Balance Book" consisting of Form No. S&T/TB, as per Annexure: 18-A3, serially numbered. Each book before issue shall be endorsed by Senior Section Engineer (Signal) as under: "Page _______ to _______ checked and found correct". (b) Technicians shall fill up portions 'A' and 'B' of Token Balance Book form and take the signatures of – The Station Master of the Station from where tokens have been extracted to verify that token numbers as mentioned were extracted from the instrument with his permission; and the receiving Station Master to verify that token numbers mentioned in the book have been correctly deposited in the relevant instrument. (c) An entry in the "Train Signal Register" shall be made to this effect. (d) Station Masters shall have instructions to advise the Technician (signal) by wire/control message as soon as the balance of tokens in their token balance register falls to "Six". Chapter 18: Block Instruments, BPAC & IBS Working Page 367 of 530  (e) Extracting of/replenishment of tokens in Token instruments shall be done when the instruments are in the "Line Closed" position. (f) Token pouches shall be kept in proper repair by the Traffic Department and damaged pouches shall not be allowed to be used. Note: Also refer to para No. 18.9.1. 18.7.6 Responsibility of the Operating Staff (a) Staff operating the instruments is responsible for the safe working of the instruments, which is dependent on the correct use of the code of bell signals and the correct operation of the instruments being carried out in proper sequence. (b) Importance of Bell Signals: The provision of telephones does not do away with the necessity for use of authorised code of bell signals. Section 8: Maintenance of Block Instruments & their Ancillary Apparatus - General Instructions 18.8.1 (a) Technician shall ensure by a fortnightly check that (b) Locks: Electrical or Mechanical Locks are in a condition that they are not liable to be forced. (c) Indicators: Indicators operate fully and return to the normal position correctly when released. (d) Contacts: All contacts are clean and free from pitting, if surfaces are pitted, they shall be cleaned with chamois leather and refurbished. (e) All springs are in good condition and kept properly adjusted. (f) Relay Armatures: Relay armatures are free and return to their normal position when no current is flowing. (g) Track Circuits: Instructions as laid down in Chapter 17 of SEM shall be adhered to. (h) External Wiring: All wiring is in good condition and free from joints. Joints, wherever necessary, are properly soldered and insulated. (i) Terminal Screws: All terminal screws, lock nuts and locking screws are kept tight and split pins opened. (j) Batteries: All batteries are kept clean, terminals tight and free from dirt or corrosion and maintained in accordance with instructions in Chapter 16 of SEM. (k) Lightning Protector: Lightning and power protective devices and earth connections are effective and in good condition. Chapter 18: Block Instruments, BPAC & IBS Working Page 368 of 530