Below Rail Infrastructure

Hybrid polymer sleeper solution for bridges, viaducts, tunnels, switches and mainlines

The increasing scarcity of hardwood and the ban on creosote-treatment of timber sleepers has resulted in their reduced availability and lifespan. The replacement of timber sleepers with stiffer or weaker materials creates new track stability problems. Lankhorst developed its KLP Hybrid Polymer Sleeper to mimic the dynamic behaviour of a traditional timber sleeper, with the added benefit of a design life of 50 years.

In operation since 2006, KLP Hybrid Polymer Sleepers consist of highly ductile recycled polymer, reinforced with steel rebar. The steel increases bending stiffness and provides elastic resilience against deformation. Reinforcement does not interfere with the installation of fastening systems and achieves longitudinal and lateral stiffness, maintaining track gauge under all load and climate conditions. The recycled polymer acts both as effective impact absorber and sound damper. KLP Hybrid Polymer Sleepers are now  operational in bridges, turnouts, and mainlines in 11 countries on three continents. That success recently expanded into Australasia through close teamwork between Lankhorst and regional agents Link Asia Pacific.

Steel reinforced for strength.

KLP Hybrid Polymer Sleepers are backed up by solid engineering and extensive laboratory testing, enabling its use in railways operating at axle loads up to 35 tonnes. Lankhorst has successfully put the sleepers through a series of tests, including static and dynamic loading, destructive testing, water absorption, electrical insulation, UV testing, slip and wear resistance, screw spike pull-out tests, flammability and more.

Whereas composite sleepers can be brittle, KLP Hybrid Polymer Sleepers offer better ductility and shock absorption. They offer a high bending stiffness due to their discrete steel reinforcing elements and don’t catastrophically break or tear under overload. Extreme overload bending tests confirmed this. Hybrid polymer sleepers are well-suited for strength and impact critical applications, such as on bridges, track where the ballast bed does not provide sufficient elasticity, and track subjected to very high horizontal or vertical impact forces resulting from high-speed or high axle-load traffic loading.

Compared to alternative products, KLP Hybrid Polymer Sleepers offer some unique benefits:

  • Maintain track stiffness, even with interspersed replacement (Dynamic stiffness comparable to that of replaced sleeper),
  • No hazardous fibre dust released during drilling; no respiratory protection equipment required,
  • Low weight, easy installation and reduced transport costs,
  • Standard equipment required during installation,
  • Machinable like timber,
  • Thermal expansion rate is six times lower than that of fibreglass – comparable to concrete and timber,
  • High strength through steel rebar reinforcement,
  • Exceptional impact dampening and noise dampening through ductile polymer,
  • Compatible with most rail fasteners used for timber sleepers,
  • 100 per cent recyclable, being made of steel and recycled polymers, and
  • Low carbon footprint, using recycled polymers.

KLP Hybrid Polymer Bridge Sleepers

Designed for offset load applications.

Bridges with offset girders benefit most from the KLP hybrid design. The steel reinforcement provides the strength required to handle the high bending moments in bridges with offset girders. In-track performance confirms the design intent: no gradual plastic deformation occurs. Extreme overload situations will not result in catastrophic (brittle) fracturing.

Unballasted bridge structures are very stiff and have limited ability to flex during cyclic loading. The high impact on structure can result in microcracking in steel-reinforced concrete structures. Here KLP Sleeper’s polymer both absorbs and spreads impact energy, lowering load levels in the bridge structure. Reduced impact also results in noise reductions: Replacing timber sleepers with KLP Hybrid Polymer Bridge Sleepers on a steel girder bridge yielded a 3-5dB noise reduction.

Girder based bridges with canted rail can utilise the KLP Hybrid Polymer Bridge Sleeper type 401. Height differences for canter can be compensated by milling up to 25mm at our factory or on location. KLP Shims between the sleeper and the base plate can compensate for minor height differences. Voestalpine, having fitted dozens of bridges with KLP Hybrid Polymer Bridge Sleepers since 2010, confirms: “no maintenance is required, performance on all bridges is satisfactory”. 

KLP Hybrid Polymer Switch & Crossing Sleepers

Switches: built on or off site.

KLP Hybrid Polymer Switch & Crossing Sleepers absorb and distribute impact better than timber and concrete. This delivers a significant benefit at crossings and turnouts, which are typically exposed to severe impact and lateral forces. Unlike concrete (where every hole must be pre-cast in the factory), KLP Hybrid Polymer Sleepers can be drilled throughout the full length of the sleeper onsite or prefab.

KLP Hybrid Polymer Sleepers have a low thermal expansion, resulting in a track gauge that stays within tolerance, even for longer sleepers. The KLP Hybrid Polymer Sleeper 200-series (length of up to 5.2m) have been optimized for the fixation of base plates with a larger rotation. The KLP Hybrid Polymer Sleeper 500-series have a connectable joint, enabling the connection of two sleepers together resulting in a maximum sleeper length of 10.4m. The KLP Hybrid Polymer 500-series can be installed with limited working space and do not require deep holes to be dug. These sleepers provide a constant bending stiffness throughout their entire length.

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 during 12 years of accumulated exposure of more than 300 million tonnes of load passing.”

KLP Hybrid Polymer Mainline Sleepers

Handles and installs like timber.

The KLP optimised hybrid polymer mainline sleepers are profiled and therefore use up to 30 per cent less material, resulting in an even more economic 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.

Visit us at:

Rail Solutions Asia
Stand 124
12 – 14 August 2020
Kuala Lumpur, Malaysia

Hall 21 / Stand 310
22 – 25 September 2020
Berlin, Germany

Stand 13
1 – 2 December 2020
Adelaide, Australia