The New South Wales railway network commenced ballast cleaning operations in the 1970’s with one RM 62 and four RM 76 ballast cleaning machines in 1978 and 1979. Whilst these machines had performed well for many years, maintenance costs, reliability and safety factors led to a reduced operating fleet of two RM 76 ballast cleaning machines by the year 2000.

With the intention of introducing new technology, greater capacity, better reliability and improved safety, the Rail Infrastructure Corporation (now known as RailCorp NSW) invested in a new high performance ballast cleaning machine – the RM 900-HD – to replace the old machines. The order was placed in June 2002, which was the commencement of a two year project for the design, manufacture, testing and commissioning of the largest single machine ever manufactured by Plasser Australia at the Sydney workshops.

The RailCorp RM 900-HD has a number of unique features that distinguish it from other RM 900 ballast cleaners:

Two-stage screening of contaminated ballast

The first stage comprises two ‘Star Screens’, each of which has numerous rows of special rubber star-shaped rotors mounted on horizontal shafts. The high-speed rotation of the star screen rotors propels the excavated material forward, impacting it against vertically suspended plates to break up the material. The star screens are designed not only to separate the fine particles of contaminant but also to remove clay materials that have a tendency to stick to individual ballast particles.
The second stage comprises two conventional inclined vibrating screens, each of which is fitted with three decks of screen mesh. With most of the fine material removed in the Star Screens, it is possible to install a smaller mesh size on the bottom decks of the vibration screens and recover more ballast without overloading the screens.
The effectiveness of this system has already proven valuable in the field, even in the most severe conditions of moisture and contamination in which it would have been impossible for conventional (vibrating screen) ballast cleaners to operate successfully. The removal of the majority of the fine contaminants in the star screens allows more efficient operation of the second stage vibration screens, resulting in a significant increase in the amount of ballast that is recovered and returned to the track as well as greatly increase machine output. The major benefits to RailCorp include savings of large quantities of fresh make-up ballast as well as reduced quantities of spoil, resulting in substantial cost savings in new ballast (and fewer ballast trains) and spoil disposal.

Dust suppression system

Dust suppression is achieved by a combination of compressed air-atomised water spray nozzles and fine spray nozzles strategically placed near dust sources such as the excavation chain and conveyor belt transfer points. Water for the system is supplied by three 15,000 litre tanks mounted on a special water tanker wagon located at the rear of the machine. In addition, the water is supplied to each end of the RM 900-HD for connection to MFS 40 hopper conveyor wagons, also equipped with intermediate water tanks and spray nozzles.

Control System
The technologically advanced control system comprises a high-speed Programmable Logic Controller (PLC) handling all the digital and analog tasks required for traction, operation and data logging. An industrial network connects all of the various control elements on the machine, including three touch panels providing the operator and drivers with intuitive control of the various aspects of the machine. System faults are highlighted in real time and logged for historical purposes, as well as being indicated on mimic panels to assist their location and rectification. Critical operational parameters and timings are able to be altered in real time at the touch panels via password-protected screens, allowing a suitably-responsible person to fine tune the machine operation.

A total of twelve MFS 40 hopper conveyor wagons have also been manufactured by Plasser Australia to complement the RM 900-HD and manage the disposal of spoil from (as well as the supply of fresh ballast to) the machine. Effective use of MFS 40 type wagons enables very efficient handling and disposal of spoil without interrupting production of the ballast cleaning machine. When attached to the ballast cleaner, the MFS 40 hopper conveyor wagons are fully integrated with it, i.e. they are electrically interlocked so that, in the event of an emergency, the entire operation can be stopped from any one of numerous stop buttons located along the length of the whole consist. Each MFS40 hopper conveyor wagon is also equipped with its own independent dust suppression system and voice communication is possible throughout the entire 430 metre long consist.

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