IR looks to innovate, make better use of existing resources, tests Push Pull configuration
Going ahead with a long-delayed push to increase average speeds of trains, Indian Railways announced ‘Mission Raftaar’ in the Railway Budget of 2016-17. The mission targeted increasing the average speed of all non-suburban passenger trains by 25 kmph over the next 5 years.
Under Mission Raftaar, one of the measures IR has begun testing is the ‘Push-Pull’ mode of operation on passenger carrying trains for the first time.
The Push-Pull mode
Push–pull is a configuration for locomotive-hauled trains, allowing them to be driven from either end. In this mode, one loco each is attached to the train at both ends. The train is then pulled and pushed by the locomotives simultaneously. The train is operated by the crew from the leading unit. A single loco pilot is stationed in the rear locomotive to monitor parameters of the rear loco.
Benefits
IR plans to run trains with WAP-5 and WAP-7 electric locomotives in this mode. This configuration is expected to be beneficial in several ways. One of the key benefits from the provision of two locomotives is twice the power for a given load. This will lead to improved acceleration times. The doubled power-to-weight ratio will also allow the crew to maintain Maximum Permissible Speed (MPS) for longer durations. Theoretically, this should lead to increase in average speed of such trains.
Another important benefit is the reduction in turnaround time that accrues from having driving cabs at both ends. Shunting the loco around to the other end for the return journey is no longer necessary. Reduced platform occupancy durations will also improve utilisation of existing station capacity.
DPWCS: The Wireless Mode for Freight
The push pull concept, though in a different form, is already in operation in some zones. So far, this mode has been tested with freight trains. Several locomotives in zones like SCR have been equipped with Distributed Power Wireless Control System (DPWCS). Locos paired through DPWCS, though physically as far apart as 600-1200 metres, communicate in realtime with each other over wireless radio signals. The lead loco sends control signals to the slave loco(s) along the rake and receives confirmation and telemetry data from the slave over the same medium.
The Cable Mode for Passenger Services
However, rakes configured for push pull use on passenger carrying trains will have a International Union of Railways (UIC) standard cable running along the undercarriage end to end. Transmission of control signals between the two locomotives will be through this cable. A cable of approximately 600 metre length will be needed for a 22 coach LHB rake formation. For redundancy, a spare cable will also be strung along with the primary cable.
Several modifications are also required to the control software and cabling in both locomotives for compatibility with this configuration.
Trials with this configuration have been conducted between New Delhi – Bandra Terminus over the Western Railway route in October. More trials between Chhatrapati Shivaji Maharaj Terminus, Mumbai and New Delhi over the Central Railway route are underway. The testing process Is expected to be completed soon.
IR has set a deadline to start commercial services with a train running on push pull mode by 10th February 2019 on both these sections. The deadline is subject to issue of final speed certificate by Research Design and Standards Organisation (RDSO) and requisite sanctions as per policy.
What is the need to station a second loco pilot in the trailing engine? Surely there must be some way to monitor the trailing engine from the front?