Screening car carrying three 3-level eccentric vibratory screens

Excavating chain

Excavating chain

Track lifting and slewing units

Ballast distributing conveyor belts and profiling plough with lifting and slewing device

Ballast chutes

Stabilising unit

Measuring equipment

Drive unit/measuring/transfer car

High working speed for ideal utilisation of the shrinking windows available for maintenance, high cleaning quality to ensure a stable track and the recycling of ballast, as a costly resource, paired with a variety of applications (cleaning with new ballast placement, total excavation with or without subsequent supply of new ballast) led to the development of the RMW 1500 high-capacity ballast cleaning machine with integrated supply of new ballast.

Stable ballasted track - the foundation for faultless track geometry

The most important functions of the ballast bed are:

• to distribute the wheel loads uniformly on the subgrade
• to guarantee the elasticity of the track in order to reduce the dynamic stresses
• to secure a firm and unshifting position of the ties
• to easily restore and conserve the track geometry obtained during track maintenance
• good permeability and ventilation to ensure a long service life of the ties and avoidance of frost heaves

A fouled ballast bed cannot meet these criteria. Therefore, neglected ballast cleaning can lead to increased maintenance costs and operating costs (speed restrictions) and to a shorter service life of the permanent way (e.g. ties).

Criteria for a ballast cleaning machine with high output and quality

The formation must have:

• a formation slope of approx. 4-5% to guarantee good drainage of water falling on the ballast bed
• a smooth longitudinal level to assure a uniform settlement behaviour under traffic load

Inbuilt irregularities in longitudinal direction lead to track geometry faults that imitate the substructure.

Ballast bed cleaning using the RMW 1500

The RMW 1500 is a high-capacity ballast cleaning machine with integrated supply of new ballast which fulfils all the above mentioned requirements.

The machine is equipped with two excavating chains. The screening car is designed with three triple-level screening units to ensure a high cleaning quality. The first chain takes up the top layer of ballast up to a width of 3.900 mm and a depth of 800 mm below top of rail.

The second chain excavates the remaining ballast bed to a maximum width of 5.600 mm (incl. feeder plates) and a depth of 1.100 mm below top of rail.

Two track lifting and slewing units are positioned in the vicinity of the two excavating chains. These lift and slew the track in the construction gap and ensure the correct geometry of the track in longitudinal level and alignment after cleaning work is completed.

Cleaning using 3-screen unit and returning the cleaned ballast and/or new ballast

The ballast excavated by the two excavating chains is taken to the 3-screen unit mounted on a separate screening car. Over-sized stones and fine stones are separated with the help of triple screen layers in each screen. The second screen layer in each screen is fitted with a grid screen which improves the quality of the screened ballast. To ensure a high quality of screening even on superelevation, the screen car can be placed in horizontal position hydraulically.

The cleaned ballast is taken on conveyor belts to the profiling plough immediately behind the excavating chain and returned to the track using two slewing ballast distribution conveyor belts.

New ballast can be added, if required, taken from MFS units positioned at the rear via the new-ballast conveyor belt and the ballast chutes. The hydraulically adjustable flaps make exact metering of the quantities of ballast possible and the tamping zones can be filled with the required amount.

The cleaned ballast, and if necessary the new ballast, can be compacted using the stabilising unit and this achieves an initial homogenisation of the ballast bed. The track's resistance to lateral displacement is also raised following cleaning.

The spoil separated from the ballast in the three screening units is taken away in the direction of work to the MFS units at the front of the machine.

During all working processes the recording unit records the parameters: excavating depth, formation crossfall, track lowering, twist, versine and cross level. The excavating chains are guided automatically by electronic transducers mounted on them and, if necessary, adjusted automatically. The data can also be saved and processed electronically.

Measuring system of RMW 1500

The machine is equipped with 2 measuring systems: Integrated surveying in the drive unit, transfer of data to the excavating car. The track geometry after cleaning corresponds to the track geometry before cleaning.

Guidance of the machine with the help of target geometry data using the integrated ALC. Both measuring systems guide the machine both in longitudinal level and alignment. Optional extra: guidance by laser.

Method of Work

To prepare the machine for work, the front four-axled bogie is shifted forwards. This produces a sufficiently large gap and a smooth bending line of the track.

Using the RMW 1500 the following stages of work are performed in one operation:

1. Track grid is lifted and held in the construction gap

2. Top layer of ballast is excavated

3. Remaining ballast bed material is excavated

4. Material is transported to screening car carrying three screening units

5. Large stones and fine particles are sifted out in three-layer screens

6. Cleaned ballast is transported back

7. Placement of the cleaned ballast using ballast distributing and profiling devices

8. Supply of new ballast from MFS units at rear of machine, inserted via ballast distributing chutes

9. Stabilisation of the track grid using DGS unit

10. Geometry of the cleaned track and various operational parameters are measured and recorded

11. Spoil is taken away to the MFS units at front of machine

• Two-axled drive unit/measuring/transfer car with new-ballast conveyor belts and two drive engines.
• Twelve-axled excavating car with the two excavating chains, lifting and lining units, ballast distributing conveyor belts, the profiling plough, the new ballast insertion chutes, the digger to dig a trench under the track, crane to insert and lift out the chain cutter bar, the stabilising unit and the crew cabin.
• Four-axled screening car carrying three eccentric screens each with three screening levels.
• Four-axled drive unit/spoil transfer car.

High output combined with highest quality

• Better utilisation of short track possessions
• Transport of material solely in the track under construction
• No hindrance to the adjacent track
• High quality of the cleaned ballast due to triple screen unit and the incorporated grid screen
• Homogenisation of the ballast bed and increased resistance to lateral displacement following cleaning

RMW 1500

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