The correct ballast cross-section, as defined by the permanent way regulations, is very important. Above all, it is important for the safety of the track geometry against track buckling. Moreover, any unnecessary spreading of the ballast bed represents a cost factor.
To counteract this, it is vital to produce the right ballast cross-section both in the course of track maintenance, as well as when placing new ballast. If this work is not carried out regularly, huge quantities of ballast could be lying unused in the track network.
An important factor for cost-efficiency is the correct distribution of the ballast in the track and the reclamation of ballast from the shoulders, especially using machines with a ballast hopper or in combination with larger ballast stores such as the material conveyor and the Plasser-Knape system hopper units. The quantities of ballast saved or reclaimed in this way in the course of a year enable the machines used for this purpose to pay for themselves in a very short time. Treatment of the ballast bed surface using ballast profiling machines, especially on the shoulders, also has a favourable effect in combating plant growth. Primarily, this is a purely mechanical effect on the ballast surface; there is no other environmental pollution. On high-speed lines treatment of the sleeper surfaces and the sleeper cribs by thorough sweeping is important to prevent ballast stones being swirled up by passing trains at high speeds. Ballast distribution and profiling machines can, depending on the design, use the following facilities.
Sweeper unitWith reversible lateral conveyor belt for depositing the surplus ballast on either ballast shoulder.
Rail fastening brush:
To remove ballast stones around the rail fastenings.
To level the ballast unloaded from the wagons.
For treating the crown of the ballast bed, depending on position on the machine either as a front plough or centre plough. Centre ploughs can generally be used in both directions, front ploughs only in one direction.
A grading plough consists of fixed and adjustable baffles as well as tunnel plates in the area around the rails and the rail fastenings. The action of the grading plough causes a flow of ballast on the ballast crown crosswise to the track axis in any direction required. The halves of the plough can be adjusted individually which means that the quantity of ballast remaining on the ballast crown can be dosed exactly. The tunnel plates protect the rail fastenings from damage.
For ploughing on tracks with line conductors, centre ploughs with hydraulically displaceable protective plates are used, to prevent ballast covering the line conductor. In combination with shoulder ploughs, ballast movements can be performed crosswise across the track profile, from one shoulder to the other or from the shoulder to the centre section or vice versa.
These draw the ballast from the ballast shoulders to the ballast crown. The shoulder ploughs are operated hydraulically from the control desk of the machine. The shoulder angle can be set between 0° and 45°. The ploughs are adjustable in the plane of the shoulder. As a result when there are obstacles that the ploughs must get out of the way, the shoulder angle must not be changed and no piles of ballast are left behind.
Depending on the particular model, work can be performed in both directions or a ballast box can be formed to displace the ballast along the track.
In compliance with the regulations of some railways concerning treatment of the centre section on double track lines, the machines can be equipped with an automatic slewing limitation for the shoulder ploughs. This limit is dependent on the relevant provisions from the regulations of the administrations or the loading gauge, and after entering the appropriate parameters are automatically determined by the system. Therefore, when the shoulder plough is working it cannot inadvertently foul the adjacent loading gauge.
Systems for ballast management:
The ballast needed for a functioning track network is an important capital asset. Enormous investment costs for substantial quantities of ballast make cost-efficient management of the raw material essential.
Economical distribution of ballast over the complete network is a big source of potential savings. On one hand, many sections of track have far too much ballast in relation to the standard profile, which could be picked up. On the other hand, the insertion of new ballast in areas lacking ballast requires additional expenditure.
A uniform ballast bed also improves the durability of the track geometry, whereas irregular placement of ballast increases the risk of buckling. Too much ballast may hinder proper drainage. Also track conversion from wood to concrete sleepers can generate a surplus of ballast.
Conventional methods of ballast manipulation, i.e. loading, transporting, distributing, picking up and removal of excess ballast, require a lot of time, staff and resources. Economic management in this way is not possible.