To accelerate the effect of “constant dripping”, the water pressure must be correspondingly high – for example in water jet cutting. This cutting technology uses a thin jet of water (sub-mm thickness) at high pressure (up to 5,000 bar) and high speed (up to 1,000 m/s nozzle outflow speed) to cut a wide range of materials (including steel up to a thickness of 50 mm).

RailRestore ‒ the beginning

Twelve years ago, a group of inspired Dutch engineers began to explore the idea of rail treatment using water jet technology. After extensive research, two application scenarios for rail treatment were identified: cleaning rail surfaces and reprofiling rails. Over the years, these ideas were developed further and refined, and a research partnership was entered into with a company specializing in water jet technology. In 2016, RailRestore was finally founded in Bavel, the Netherlands. Since 2021, it has been part of Digital Railway Solutions AG (DRS), a Plasser Group company.

Cleaning rails

A contaminated rail surface can directly affect the safety of railway operations. Depending on the railway system, various track vacancy detection systems are used for train control, which detect a railway vehicle in a block system via short-circuit currents. If the rail surface is contaminated (rust, leaves, lubricants, etc.), the axles of a vehicle cannot establish this short circuit and the vehicle is not detected. Another function of a contamination-free rail surface is to enable traction. In simple terms, sufficiently high coefficients of friction between the wheel and rail are necessary for a train to accelerate and brake safely. Especially in autumn, leaves that stick firmly to the rail can form a hard layer with extremely low coefficients of friction. However, excessive use of wheel flange or rail flank lubrication can also lead to low coefficients of friction.

Solutions based on high-pressure cleaning already exist for trams. The RailRestore system is different from them since it uses significantly higher water pressure combined with abrasive material (sand, corundum, etc.). This is how a higher cleaning output can be achieved with less water compared to all other systems available on the market. Seasonal foliage removal is a particular challenge for heavy rail systems. Also for this scenario, there are various solutions that utilize laser systems or dry ice pellets in addition to high-pressure cleaning. There are also stationary or vehicle-mounted systems that are used to break up the layer of leaves. None of these systems have yet provided a reliable solution to this problem.

A first prototype of an innovative cleaning system for trams was successfully tested by RailRestore in 2019 for a customer in the Netherlands. The experience gained led to a further development of the system and subsequent tests in 2021. The first commercial system has been in use at HTM The Hague since the end of 2023. Commercial shifts will also be implemented in 2024, which will be used to further develop the system. Demonstrations at other urban transport companies will also follow. Depending on demand, the plan is to launch a second modular system towards the end of 2024/beginning of 2025 that is suitable for use on a road-rail vehicle (tram) as well as for installation on a rail-only vehicle (heavy rail).

Rail treatment

Rail treatment is much more complex than rail cleaning. There are already existing and established technologies such as rail grinding or rail milling in this area. The advantages of water jet technology is that “cold” processing of the material is possible (no heating of the material) and the process is low-wear (no “tool” is in direct contact with the workpiece). It is also a dust-free and spark-free process (no risk of fire).

Based on a stationary test facility at RailRestore in Bavel, a first successful feasibility study was carried out on track with a prototype trailer in 2017. The findings from this pilot test led to improvements in the technology and further trials on the stationary system in Bavel. A new and improved test facility is currently being built at Plasser & Theurer’s Technology Centre in Purkersdorf, which will go into operation in the second half of 2024. It will be used to check the repeatability and the influence of individual parameters on the result under known conditions. This extensive basic research will thus be used for subsequent product development and system optimization.