Push Pull Train Operation — Real WAP7 System & Procedures

Real Key Advantages of Push Pull Trains

• A) Improved safety: real safer mode of operation vis-à-vis hazardous NON-SYNCHRONISED banking operation in Ghat sections across Indian Railways; Pull-Push mode offers the same safety level as a Train-Set.
• B) Most economic option for higher-speed train operation: existing rolling stock & locomotives can be used; cost of coach/loco modification is negligible — real cost is Rs. 3.5 lakh per coach for two train lines, expected to reduce further as volume increases.
• C) Real operational advantages: faster operation of dense traffic at longer distance; no need for engine reversal where train direction reverses (e.g. real stations NGP, DD); Hub & Spoke train operation — slip coaches can be moved promptly with rear loco (real example: Chalisgaon-Dhule coaches of train 11057); significantly reduced stoppage time; suitable for quicker platform-return trains (especially at dead-end terminus stations); higher acceleration & faster braking increases sectional capacity; higher/flexible transport capability for higher traffic volume; flexibility to vary train-length for seasonal traffic variation; no chance of section blocking; higher reliability from proven/mature technologies.

The 'push & pull' technique places 2 locomotives — one at the front, one at the back — providing more stability. Generally a train-set has 2 power cars for hotel-load; with push-pull the 2 attached locomotives handle hotel load instead, so power cars can be replaced with coaches, increasing capacity and revenue. Real milestone: the first Pull-Push passenger train over Indian Railways — the CSMT-NZM Rajdhani Express — ran successfully on 13.2.2019 between CSMT and NZM. Real result: this eliminated the need for attaching/detaching a banker locomotive on the Ghat section, and reduced journey time by real 95 minutes between CSMT-NZM.

Real WAP7 Push-Pull Modification (RDSO Scheme)

Per real RDSO letter no. EL/3.1.35/4 dated 11.12.2018, a scheme for modifying WAP7 locos for push-pull operation was issued, implemented in real 5 WAP7 loco pairs of ELS/Ajni. In push-pull mode, one loco is in FRONT of the rake ('Master loco') and one is at the REAR ('Slave loco'). The modification adds an additional BL switch, additional BPFA, and additional LSDJ on the 'D' panel in each cab of BOTH master and slave locos. The real ZTEL switch on the 'A' panel is renamed the ZNN switch, used for negotiating a neutral section.

Real Coupler System — IVC & UIC Couplers

WAP7 locos are provided with real 4 couplers on each cab side: (i) IVC coupler — 2 nos., for power connection of Hotel load; ON command pins of the hotel-load converter are provided in the IVC coupler only. Real positions: LP side for Hotel load converter-2, ALP side for Hotel load converter-1. (ii) UIC couplers — 2 nos.: LP side for Push-Pull operation (with an additional coupler on ALP side for MU provided in real locos 30579 & 30580 only), ALP side for Hotel load converter.

UIC couplers (for hotel-load converter and push-pull operation) provided on the loco cab are FEMALE sockets; IVC couplers (for hotel-load converter power connections) provided on the loco cab are MALE couplers. On the rake side, each power car has MALE sockets at BOTH sides (LH & RH) for push-pull operation — both sockets are connected in parallel. For push-pull operation, one flexible jumper with male & female couplers at either end is required: the male end goes into the LP-side female socket on the loco cab, the female end goes into either of the 2 male sockets on the power car.

A similar jumper connects the rear power car and slave loco. Real note: though both jumpers are 18-pin, their internal wire connection differs — one is called STRAIGHT jumper, the other CROSSED jumper. Push-pull operation MUST use one of each. If a straight jumper connects master loco to front power car, the cross jumper must connect slave loco to rear power car, and vice versa. Real 61375 IEC-compliant communication train line uses modular connectors for this purpose. Real fact: one additional straight and one additional cross coupler is required for locos 30579 & 30580; this modification is planned for extension to all locos.

Real Energisation Procedure — Master & Slave Loco

Real note: in Master loco, panto selector switch 85 must be MANUALLY selected so the rear pantograph is raised. Step 2: connect BP and FP pipe of both locos with the train rake's BP & FP pipe and open angle cocks. Step 3, in slave loco: (a) keep SA-9 released in both cabs, observe '0' pressure on the BC gauge; (b) move A-9/DBC to emergency position — brakes apply on loco and rake; (c) move A-9/DBC to neutral position and remove the handle.

Real Neutral-Section Negotiation Instructions

• (a) At the 500m board, following signal aspects and section speed restrictions, attain maximum speed. (b) At the 250m board, bring throttle to zero and switch ON ZNN. (c) At the DJ-open board, switch OFF BLDJ and ensure LSDJ is glowing. (d) At the DJ-close board, switch ON BLDJ and ensure LSDJ extinguishes. (e) The additional BLDJ on master loco's 'D' panel remains extinguished continuously throughout.
• Real neutral-section timing logic for slave loco DJ: (I) After master loco's DJ turns OFF, slave loco's DJ opens after real 330 metres (considering minimum rake length). (II) After master loco's DJ turns ON, slave loco's DJ closes after real 750 metres (considering maximum rake length). Opening/closing of the slave loco's VCB can be verified from the Node information screen in the master loco.

Real Fault Handling in Push-Pull Operation

• In push-pull operation, NO fault messages pop up on the slave loco's DDU — fault messages are only RECORDED in the slave loco and can be seen in its DDS (Diagnostic Data Set). Fault messages instead pop up on the MASTER loco's DDU with LSFI glowing, along with the loco number — the LP must understand from the loco number whether the fault is in master or slave loco, and take corrective action per TSD (Trouble Shooting Directory).
• Real communication-failure behaviour: if communication between master and slave loco fails, a 'COMMUNICATION DISTURBANCE' message displays on the master loco's DDU, and 2 real actions happen AUTOMATICALLY: (i) VCB tripping in master loco; (ii) VCB tripping AND lowering of pantograph in slave loco. Master loco can then be worked normally by closing VCB.
• Real 1-hour self-hold limit: after communication failure + VCB tripping + panto lowering in the slave loco, it remains in self-hold mode for ONLY 1 hour. During this window, either reconfigure the master-slave combination at any convenient halt, OR make the slave loco dead per TSD at a convenient halt/unscheduled-halt station. Either reconfiguration or making the slave loco dead MUST be done within this 1-hour self-hold window — otherwise EMERGENCY BRAKES apply in the train from the slave loco, halting it at any (possibly inconvenient) location.

In push-pull operation, hotel-load converters of the MASTER loco only (if provided) are in service — so IVC & UIC couplers of the Hotel load are provided with jumpers from the front power car ONLY. NO IVC & UIC jumper of hotel-load converter is to be connected between slave loco and rear power car.