Relay Installation & Testing Procedures PDF

Section 2: Installation & Testing of Relays 21.2.1 Relays – General Requirements: (a) Approved type of Plug-in Line relays of Neutral/Polar Biased/Magnetic latch/Interlocked type rated at 24/48/60 V DC shall normally be used. Approved type of LED Lamp proving relays shall...

Section 2: Installation & Testing of Relays 21.2.1 Relays – General Requirements: (a) Approved type of Plug-in Line relays of Neutral/Polar Biased/Magnetic latch/Interlocked type rated at 24/48/60 V DC shall normally be used. Approved type of LED Lamp proving relays shall be used for LED signal lamps. (b) Approved type of Relays shall be used in RE & Non-RE areas. Various types of relays used in signaling are given in Annexure: 21-A1. (c) Time element relays of approved type shall be used. Where approved electronic time element relays are used, these shall be two in number and their contacts shall be in series in the concerned time release circuits. (d) The relays, including track relays, located in the track side location boxes, shall be plug-in type. (e) All plug-in relays and relay groups shall be provided with coding pin arrangement to prevent the wrong relays/relay group being accidentally plugged-in during replacement. All relays, relay groups shall be sealed. (f) As far as possible, all relays shall be housed in the relay room of the controlling cabin to achieve maximum centralization. (g) Sequential proving of front and back contact shall be ensured where metal to metal contact relays are provided. (h) Removal or replacement of plug-in relays/relay groups from the relay racks during operation shall not cause any unsafe conditions in the circuits. (i) Where feasible all relays except track relays, shall have 10% of working contacts as spare subject to a minimum of one front and one back to facilitate addition and alteration to the circuits at a later date. Extra space (minimum 10%) to accommodate repeater relays shall be provided in the relay rack to cater for future expansion. (j) Where magnetic latch relays are used, the circuit shall be so designed so as to prevent undue dropping of the relay due to back EMF generated by other relays. (k) Wiring of 'Q' type relays shall be done through flexible multi strand wire preferably and contacts to be paralleled as feasible. (l) Mercury wet contact type relay shall be used for flasher circuits, alternatively, a solid state flasher may be used. If solid state flasher is used, flashing indication on operating panel should be provided for indicating healthy condition of flasher. (m) Relays shall not be stored in the vicinity of damp or chemically polluted environment. (n) Sealing screws of the relays shall be intact. (o) Care shall be exercised in transporting the relays from the place of storage to the work site so that the relays do not get damaged. Chapter 21: Relay & Electronic Interlocking Page 449 of 530 21.2.2 Fixing in Relay Room As far as practicable, the relay room is not located in the vicinity of chemical factory, loco shed or engine ash pits etc. In case it becomes unavoidable, necessary precautions shall be taken so that relays are least affected by the chemical fumes, dust etc. and are provided with dust free environment. Relay room shall be provided with double locks and door opening shall be monitored through Datalogger. (a) Where Relays cannot be located in the Cabin, they shall be housed in location box of approved type which are properly secured. (b) In 'Q' style relay the code pins configurations for plug in relay shall not be changed by drilling additional holes on plug board to avoid fixing of a wrong relay which may lead to unsafe condition. In Siemen's K-50 relays, the Code pins position on base plate should not be changed and to be retained as fixed by the manufacturer. (c) All relay clips shall be checked for proper locking in the base when plugged in. Extreme care shall be exercised while removing the clips from the jacks of the plug-in type relay. (d) In all installations, a relay index board shall be provided for locating relays easily. (e) Relays involving external circuits shall have cross protection and double cutting. Signal control relays shall preferably be provided with double cutting. (f) A contact analysis chart shall be prepared duly showing the contacts used circuit-wise with reference and spare contacts available, wire count for each contact and relay position in the rack. (g) 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. (h) Where available, spare contacts shall be paralled with working contacts. 21.2.3 Sealing of Plug-in Relays (a) In case of metal to carbon contact type relays, sealing shall be done at Manufacturer's premises before dispatch and if the seals have to be broken due to any defect noticed, resealing must be done at the workshops. (b) In case of metal to metal contact type relays, sealing of the cover shall be done by not below the rank of JE (Signal) at site. Whenever seals have to be broken at site for maintenance purposes, the same shall be done by an official not below the rank of JE(Signal). (c) Line Relays shall be energized at the rated voltage specified in the specification. Chapter 21: Relay & Electronic Interlocking Page 450 of 530 21.2.4 Maintenance of Relays (a) Cleaning shall be done regularly so that dust is not deposited on the relay. There is no loose connection on the terminals, plug in relays is fitted tightly & the sealing is intact. Metal contacts are not blackened due to arcing. There is no pitting of carbon contacts. No foreign materials or water vapor which can cause fungus formation, are inside the relay. There is no rusting or sulphation on the parts. Relays are not due for P.O.H., wherever applicable. (b) During routine inspection and maintenance, if high contact resistance is observed on any contact of a relay, spare contact to be used or the relay should be replaced. 21.2.5 Periodical Inspection of Relays Sectional SSE/JE (signal) shall visually inspect the relays, with particular attention to those used in vital circuits. During visual inspection, relay shall be taken out of service if any of the defects are noticed in respect of; (a) Movement of armature and contact carriage (b) Wiping of contacts (c) Arcing of contacts (d) Pitting or charring of contacts (e) Dust accumulation on contacts (f) Electro-plating (g) Corrosion, rusting of components (h) Crack or breakage in components (i) Presence of fungus and ants inside the relay casing (j) Charring of cover near contacts in the case of plug-in-type relays (k) Corrosion of Label (l) Absence or tampering of seal (m) Effectiveness of relay retaining clip to be checked in case of Q style Plug-in type relays (n) Any other abnormal condition 21.2.6 Replacement of Relays: Metal to carbon contact miniature plug-in type relays should not be overhauled. These relays except track relays should not be used after completion of the codal life of 25 to 30 years or after their failure. Plug in type track relays have to be replaced on completion of 12 years or earlier if warranted by the actual condition of the relay and/or its usage. Chapter 21: Relay & Electronic Interlocking Page 451 of 530