Dutch company Lankhorst recently made its local entry with a significant order for its KLP steel-reinforced Hybrid Polymer Sleepers to the Australasian region.
The increasing scarcity of hardwood and the ban on creosote-treated wood for sleepers have created challenges in the maintenance of timber infrastructure.
Lifespan of timber sleepers is dropping and the replacement of timber with stiffer or weaker materials creates new problems. Lankhorst, a global firm whose Dutch origin began in 1803, has developed its modern Hybrid Polymer Sleeper to mimic the dynamic behaviour of a traditional wooden sleeper with an extended life span.
First installed on the Dutch rail network in 2006, KLP Hybrid Polymer Sleepers consist of highly ductile recycled polymer, reinforced with steel rebar. Lankorst says the steel reinforcement is located where it is most effective, and does not interfere with the installation of fastening systems. This helps it achieve longitudinal and lateral stiffness to maintain track gauge under all load and climate conditions, while the recycled polymer simultaneously acts as an effective impact absorber and sound damper, resulting in a reduced noise and longer lasting infrastructure.
Gerhard Klooster, business development director of Brisbane-based Link Asia Pacific (LinkAP) – which represents Lankhorst in Australia and New Zealand – tells Rail Express the combination of metal and synthetic material was immediately recognised by operators as a good solution to transition from traditional wooden sleepers.
“It did not take long for other track operators to see the logic and benefits of this design,” Klooster says. “KLP Sleepers are now operational in mainlines, bridges and turnouts in the Netherlands, Belgium, France, Austria, Germany, Sweden, Switzerland, UK, Gabon, Malaysia and Mexico.” That success has continued more recently in the Australia and New Zealand region. After Lankhorst and LinkAP participated jointly in AusRAIL PLUS 2017, they were pleased to see an increased interest in the hybrid polymer product.
“We were impressed with the progressive approach towards new technologies,” Lankhorst commercial director Stefan Hofman says. “We are now reaping the first fruits from our joint efforts. We recently received a significant order for supply of mainline sleepers and turnouts in the Australasian region. We are working towards first delivery of product in early 2020.”
“We knew that the demand for alternative sleepers would increase with time,” LinkAP’s managing director Pieter-Jan van Driel adds. “We believe that no other product in the global market matches the comprehensive and balanced offering of the brilliantly engineered products from Lankhorst. We believe that the KLP sleeper products not only offer environmental and functional benefits, but also that their ‘value-for-money’ offer is in a sweet spot compared to alternative offerings.”
When asked what the future holds, Van Driel smiles. “We are in discussion with various Australasian track owners regarding test installations and type approvals,” is all he can say.
Engineered and tested solutions
Lankhorst technical director, Aran van Belkon, said the product is backed up by solid engineering and extensive laboratory testing, which has enabled its use in railways operating at speeds up to 180km/h.
“Hybrid polymer sleepers combine the consistency and durability of concrete sleepers with the favourable impact and sound damping behaviour of timber sleepers,” van Belkon said.
“With more than 13 years of practical product performance at various clients in a variety of applications in 11 countries, we have proof that our engineered hybrid solutions meet customer requirements.”
The combination of the respective strengths of steel and recycled polymers is designed to achieve a number of desirable objectives throughout the Lankhorst range of sleepers:
- structural soundness, with dynamic stiffness comparable to timber sleeper it replaces;
- staged implementation, with 1-in-2 to 1-in-4 interspersed implementation possible due to designed stiffness;
- gauge stability, thanks to high lateral and vertical stability under working load across broad temperature range, due to steel/polymer combination and unique footprint;
- safety, with no sudden catastrophic failures under extreme overload situation, only gradual deformation;
- environmental, with a certified net carbon store, a negative CO2 footprint and full recyclability;
- easy handling, as the range can be machined on-site and handles and installs like timber sleepers; and,
- health benefits, as the sleepers contain no fibres, meaning no special respiratory equipment must be warn during installation.
To satisfy the demands of various clients for type approval over the years, Lankhorst has successfully put the range through a range of testing, including static and dynamic loading, destructive testing, water absorption, electrical insulation, UV testing, slip and wear resistance, storage, handling, screw spike pullout tests, flammability and more.
The result of the testing and implementation of the sleepers in the field is satisfied customers. Voestalpine, which has fitted dozens of bridges with KLP Bridge Transoms since 2010, says there is “no maintenance required [and] performance on all bridges is satisfactory”. LEAG’s head of rail track infrastructure in Germany, Torsten Scharnetzki, adds: “The KLP Switch Sleepers were installed in 2008, handle 25 tonne axle loads and have remained within tolerance without maintenance after 10 years accumulated exposure to more than 250 million tonnes of load passing.”
Optimised KLP Mainline Sleepers, the “everyday” member of the Lankhorst range, are designed to use up to 30 per cent less material, resulting in a more economic and environmentally friendly product. A unique bottom profile and increased ballast on top of the sleeper are designed to offer the required lateral and vertical stability, even against uplift. The reduced weight allows for easier handling during installation and maintenance.
Meanwhile, the KLP Turnout & Crossing Sleepers are designed with an enhanced ability to absorb and distribute impact when compared against timber and concrete; a benefit at crossings and turnouts, which are typically exposed to severe impact and lateral forces. Unlike concrete (where every hole must be pre-cast), KLP Sleepers can be drilled and milled. This saves costs and time.
Finally, Klooster says its KLP Bridge Transoms benefit most from the hybrid design. “The steel reinforcement provides the strength required to easily handle the high bending moments in bridges with offset girder applications,” he says. “The design offers enough safety margin to ensure no gradual plastic deformation occurs.
Unballasted bridge structures are very stiff and do not have the ability to flex during load and unload cycles; this is where the KLP Sleeper’s polymer absorbs and spreads impact energy, resulting in lower loads in the bridge structure.”
Measurements conducted on a steel girder bridge in Amsterdam yielded a 3-5dB noise reduction, following replacement of timber sleepers with KLP Bridge Transoms, Klooster adds.