Maintenance Schedules — IA/IB/IC/AOH/IOH/POH

Indian Railways has built up its electric loco maintenance experience since 1960. The scope of work prescribed in each maintenance schedule is arrived at from four inputs: (1) the manufacturer's maintenance instructions for new rolling stock, kept available to maintenance staff for each type of equipment in use; (2) maintenance instructions already developed by a zonal railway for standard equipment; (3) specific safety/fire-prevention instructions for the rolling stock; and (4) accumulated field experience of adverse environmental conditions (high temperature, high humidity, dust) that Indian locomotives operate under. Because schedules for locomotive classes already in service have more or less reached an optimum level, changes tend to be marginal — driven by service experience rather than a clean-sheet redesign.

How Maintenance Schedules Get Altered

Individual railways may make minor local alterations to schedules based on their own operating/duty-cycle experience, but the wider trend is toward standardisation, since electric locos of one system increasingly run into other systems. Two distinct approval routes apply when a change to prescribed maintenance work or periodicity is proposed:

• Safety-related changes: a comprehensive proposal — actual railway experience, likely benefits, and the specific reasons for the change — must go to RDSO with the Chief Electrical Engineer's approval. Such modifications may only be implemented after RDSO has studied and approved the proposal.
• Other (non-safety) proposals: a similar procedure applies, except that the CEE may provisionally authorise the change pending RDSO's view. If RDSO's opinion is contrary, the original schedule must be restored — though the railway may continue to pursue the matter and adopt the change to whatever extent RDSO eventually agrees.

Fleet Maintenance Periodicity — Conventional Locos (Real Board/RDSO References)

The table below gives the periodicity and duration data (current as of 11.07.2016), each row carrying its governing Railway Board or RDSO letter number.

Additional Reliability Activities Beyond Standard Schedules

• RAP — Reliability Action Plan, tracked loco-wise and equipment-wise.
• SMIs — Special Maintenance Instructions issued by RDSO/RB/CEE/HQ.
• Modifications — issued by RDSO/LKO.
• Mandatory change items during AOH/IOH/MOH/POH, each governed by its own real technical circular: AOH-schedule items (RDSO/LKO Lr. No. EL/3.6.1 dt.15.7.2002, Technical Circular ELRS/TC/0031 Rev-01-2002, 2 sheets); IOH-schedule items (RDSO/LKO No. EL/3.6.1 dt.15.7.2002, Technical Circular ELRS/TC/0029 Rev-01-2002); POH-schedule items to be changed by shops (RDSO/LKO No. EL/3.6.1 dt.16.5.2013, Technical Circular RDSO/2013/EL/TC/2013 Rev.0, 17 pages).

Technical Instructions — Four Document Types

Every maintenance section needs the technical instructions relevant to its own work, classified under four heads:

• Inspection books — give the scope of work at each scheduled inspection (TI, IA, IB, IC etc.), itemised and sequenced, arranged section-wise, with each section supervisor's responsibility defined.
• Inspection charts — prepared per component, covering the full list of points to check, observations to make, clearances to ensure, verification conditions, and the measuring equipment required.
• Trouble-shooting charts — clear instructions for each defect type, detailing checks and their sequence; a competent supervisor must satisfy himself on the correctness of investigation/rectification before the loco returns to service. Investigating teams often discover failure patterns that trigger design modifications.
• Technical charts — full details of repairs, major adjustments and refitting; where repair isn't possible, the item is replaced. These specify material description, tools to use, procedure to follow, and defects to check after completion.

The CEE's office is responsible for forwarding RDSO instructions to loco sheds and for ensuring superseded instructions are cancelled, withdrawn, and destroyed (preserving only one copy for future reference). Modifications required in RDSO's instructions may be carried out only after RDSO's approval; Sr.DEE(RS) may introduce changes provisionally with CEE's approval, but such changes must still be advised to RDSO for scrutiny and final incorporation.

Trip Inspection (TI) — Real Checklist

Trip inspection mainly covers topping of oils and distilled water in batteries, and attention to minor defects logged by Drivers, plus checks driven by hot/humid/dusty Indian operating conditions.

High-Tension and Low-Tension Pre/Post-Inspection Tests

For IA/IB/IC/2nd IC, every shed follows a standard schedule format, with staff and supervisor signatures documented and filed. The E2-section supervisor runs a defined battery of tests before and after inspection, successively from Cab 2 and Cab 1.

• Preliminary tests with 25kV supply ON: record BA (battery) voltage and battery-charger voltage; time to build compressed air from 1 to 8–9 kg/cm²; safety-valve blow-off check; brake-cylinder pressure-gauge reading on application; VEF (braking electro-valve) working via PVEF; blower operation under 'direct' and 'automatic' starting; one-minute air-leakage check in main reservoirs and brake cylinders; headlight test; cab heater/fan working test.
• Preliminary tests with 25kV supply OFF (LT test): pantograph raise/lower time for both pantographs; time-delay relay timings; QOA (auxiliary circuit earth-fault relay) functioning via an induced earth fault; QOP (power circuit earth-fault) functioning via an induced earth fault; all-lights check; Negative Bonding check — no loco is permitted from Main Shed or Trip Shed with negative bonding, verified with a 110V/30W bulb (bright when HB HOBA ON, dim when HOBA OFF).
• High-tension tests before/after inspection (successively from Cab 2 then Cab 1): pantograph raising; auxiliary compressor motor (MCPA) and Arno converter (EG)/SI unit working, watching for abnormal starting noise; main compressor working; both compressors under various isolating-switch positions; compressor governor (RGCP) cut-in/cut-out; safety-valve blow-off; blower noise check; contactor sparking/sound observation; main ammeter deviation on two traction notches, forward and reverse; wheel-slip relay (QD) and progression/regression relays (Q51/Q52); VEF electro-valve test.
• Low-tension tests before/after inspection: master controller notch-by-notch progression/regression and total regression time; sander working test; compressor isolating switch (ZCP) working test.

Section-wise Inspection Content — IA, IB, IC (Consolidated)

Inspection items are assigned by section (M1/M3/M5 = mechanical sub-sections, E1–E5 = electrical sub-sections), with each level (IB, IC) adding to the previous level's items. Consolidated below by function rather than repeating each section label separately.

AOH/TOH — Section-wise (Adds to IA+IB+IC)

• M1: ultrasonic axle testing; axle-box liner condition check, suspension roller-bearing greasing; brake-cylinder overhaul; gear-case felt-seal damage check.
• M2: overhaul all valves/replace gaskets/match seating; gauge overhaul/calibrate; wiper servo-motor overhaul; main/auxiliary compressor complete dismantle-overhaul, worn components/gaskets replaced; all cotton filters replaced.
• M3: pantograph roof-bar connection check; VEPT/VESA/VEF throttle-valve overhaul.
• E1: door hinge/shutter fixation; lookout-glass/sun-visor condition; roof bolt tightness; silicon-rectifier string fuses; RC network check (with instruments).
• E2: master-controller overhaul, dust/clean, interlocking-mechanism articulation pin lubrication, interlocking cam grease; headlight-stabiliser capacitor check; transformer/tap-changer oil dielectric-strength/acidity check, recondition/replace if needed; SMGR switch-angle check/overhaul; electro-pneumatic contactor lubrication; contactor Q-factor check; dynamic braking-resistor damage inspection, overhaul, resistance record.
• E3: Arno bearing lubrication, insulation-resistance measure/record; brush-holder insulator overhaul; auxiliary machine overhaul.
• E4: overhaul/calibrate QLM, QRSI, QF, QE, QOP, QOA, Q30; overhaul/test Q118, Q44, QTD, Q48; overhaul/test SMGR relays (Q51, Q52), QD, Q20; speedometer overhaul.

Intermediate Overhaul (IOH) and Periodical Overhaul (POH)

IOH may be done at the homing shed itself or at a nominated workshop. Beyond the thorough IA/IB/IC/AOH inspection, IOH requires squaring of bogies; traction motors, rectifiers, auxiliary machines, blowers, tap changer, and pantograph must be removed from the loco and overhauled; transformer oil is filtered and replaced if acidity exceeds permissible limits; all wheels are re-profiled; insulation resistance of all HT and LT circuits is measured and recorded; and approved modifications executable in the shed are carried out. Each shed follows its own standard schedule format for IA/IB/IC/AOH/IOH/MOH/RAP checking.

The nominated POH workshop issues a programme at least six months in advance, month-wise, listing individual loco numbers; the homing shed sends important points to be attended and the modification list, so the workshop can plan work and procurement. The loco travels to the workshop under its own power, under escort, with its History Book, and a complete deficiency list is jointly checked by the workshop and shed representatives. All approved modifications must invariably be carried out during POH — deferment needs the personal approval of the CEE controlling the POH shops, in concurrence with the CEE controlling the homing shed, with advice to the homing shed.

• On completion, the loco is taken over by a homing-shed representative after joint inspection; work/modification details are entered in the History Book, which returns with the loco. The loco returns working on its own power, and if possible hauling a train, to the owning railway.
• Rebuilding & recabling: during every alternate POH, locos need recabling and pneumatic pipe renewal. During every 4th POH, mechanical components and traction gear may need rebuilding, with major-component replacement and opportunity to upgrade parts using state-of-art equipment.

Mechanical Wheel & Clearance Standards

Limits for each item are specified per loco type by the CEE, based on manufacturer/RDSO recommendations, and must be recorded in registers or on printed cards preserved for reference at the PPO (Periodical Point of Overhaul/inspection) at all times.

Squaring of Bogies

Heavy mechanical stresses and impacts in service can distort bogies out of shape. During IOH and POH it is essential to restore correct bogie shape/alignment. Every major shed and POH shop provides a test rig with substantial foundation on which the bogie is placed to measure the distortion, which is then corrected — hydraulically or otherwise — by applying adequate pressure at the appropriate points, ensuring proper mechanical alignment of all parts assembled over the bogie.

Engine Fitness Certificate

Whenever a passenger-service loco is released from a loco shed or outstation depot after a scheduled inspection or unscheduled repair, an Engine Fitness Certificate must be issued, in two parts: Part A (items checked by maintenance staff only) and Part B (items checked jointly by maintenance staff and Driver). Before despatch from Main Shed or Trip Shed, these spares must be ensured aboard: all spare fuses in working condition; BP pipe – 1 No.; FP pipe – 1 No.; screw coupling – 1 No.; wooden wheel skids – 4 Nos.; fire extinguisher as per instruction.

• One certificate copy is kept by the issuing shed/depot, one is attached to the loco log-book.
• The certificate-issue inspection is conducted jointly by a maintenance-side supervisor and a Shunter or Driver from the running side; observations are recorded and jointly signed.
• If a dispute arises between running and maintenance staff over engine fitness, the matter is referred to the TLC, whose instructions bind both Driver and maintenance staff.
• Once a shed/outstation depot issues a fresh certificate, the previous one is automatically cancelled, removed from the logbook, and sent to the homing shed for record.