The lineis classified as a general freight corridor and is known for its challenging topography. To achieve an annual throughput of 16 million tonnes per annum on a predominantly single-track line, a review of existing train operating practices was carried out, and with the advances in train handling technology, the logical step was to increase train lengths to the maximum safe limit.
After extensive computer train handling simulations, TFR's Technology Management Train Design department conducted the first in-service test to study lengthening the current 104-wagon trains with head-end power to 208 wagon (two sets of 104 wagons) consists with eight locomotives positioned throughout each train. The locomotives are controlled from the lead unit using Radio Distributed Power (RDP).
The optimal locomotive distribution was based on initial simulations with four locomotives at the front, three in the middle and one at the rear of the train. The distribution of traction throughout the train not only improves train handling through difficult terrain but also lowers in-train forces and reduces brake charging and stopping distances. The introduction of 208-wagon trains would increase the volume per train from 6552 tonnes to 13,104 tonnes.
The objective was to evaluate the performance of RDP on the line, determine the appropriate train handling techniques for various gradient profiles, and develop train handling guidelines. The test team benefited from experience gained in the development and commissioning of the 342-wagon RDP train on the Sishen – Saldanha iron-ore line.
In-service testing was split into two phases. During the static tests on September 11-12, brake propagation and recharging times were measured at Mamathwane yard. Dynamic testing commenced on September 13, monitoring in-train forces and brake system characteristics, and comparing the data with simulated results. In addition, radio receptivity was monitored and measured, particularly in tunnels, to determine the appropriate positions of the radio signal repeaters.
TFR says the initial results of the RDP system were positive and the in-train dynamics were within safe limits.