Thursday 6th Aug, 2020

KLP Hybrid Polymer Sleepers ensure stable gauge and reduced noise levels

KLP

KLP Hybrid Polymer Sleepers offer a clever combination of high bending stiffness and low thermal expansion coefficient of steel, coupled with the dampening characteristics of polymer. This delivers affordable, reliable sleepers to track owners looking for a low-maintenance and easily installable solutions for bridges, turnouts, and track.

Stable gauge, despite high lateral loads
Trains running at speed going through turns cause high loads within sleepers. Weak materials will stretch too much resulting in gauge widening. The steel-reinforced KLP Hybrid Polymer Sleeper delivers the longitudinal strength and dimensional stability to maintain the required gauge, even in overload situations. The sleepers can be engineered to emulate the stiffness and dynamic behaviour of the sleeper it replaces to provide comparable stiffness. They are thus well suited for interspersing with existing timber sleepers.

Stable gauge, despite high thermal variances
Temperature variation cause excessive widening or narrowing of the gauge if the wrong materials are selected. Whereas polymer has a high thermal expansion coefficient, the strong steel reinforcement in KLP sleepers contains these contractions and expansions, resulting in thermal expansion comparable to concrete and steel.

Deutsche Bahn performed various in-track gauge measurements in Augsburg on KLP sleepers. The measurements were taken in different seasons, with temperatures ranging between -10°C and +51°C. The maximum measured expansion was 2mm based on a gauge of 1435mm. After testing, the inspection showed the system was still correctly tensioned and no effect on the rail fastenings were observed. No cracks and no other defects such as bending were found on the KLP sleepers, and the results contributed to Type Approval by Deutsche Bahn. Steel-reinforced polymer construction

 

Stable gauge, through lateral stability in the ballast
Independent laboratory tests for the French rail authorities confirm that the KLP Hybrid Polymer Sleeper Type 101 ensures durable and stable binding with ballast. The combination of its stiffness, geometry and polymer interface prevents longitudinal and/or lateral movement ensuring the track geometry is maintained.

The unique shape of the KLP 100-series sleeper provides additional lateral & horizontal stability due to the profile base, the scalloped shape and ballast coverage. The weight of the sleepers is lower than conventional rectangular sleepers and provides advantages where weight is an issue e.g. when cranes are used to lift pre-assembled sections of track into position or on bridges where the reduced mass of the track reduces the structural demands. KLP 100-series

 

Stable gauge, low maintenance turnouts

The low thermal expansion is particularly beneficial for turnouts. The switch mechanism in turnouts is precisely adjusted to the track gauge. If the track gauge changes, the switch tongue no longer connects properly to the rail which can cause damage to the tongue. Low thermal expansion results in less inspection and maintenance of the turnout. KLP handles like timber: easy to install.

 

Quieter bridges
The chosen polymers in KLP products absorb and dampen vibrations and impacts, thereby reducing noise. Measurements on a steel girder bridge confirmed a 3-5dB noise reduction after replacing wooden sleepers with KLP sleepers.

Dependable bending stiffness on bridges with offset loads
Steel reinforcement in KLP Hybrid Polymer Transoms provides the bending strength required in bridges with offsets between the rail and the girders. The most suitable combination of rebar size and polymer type provide the required bending stiffness for given axle load, stiffness requirements and climate conditions.

Height adjustable bridge transoms
Height difference in bridge support I-beams can be compensated by milling the transom, to achieve a level track. KLP transom types 203 and 401 have a 25mm milling zone that can be milled to compensate for height variations in bridges without affecting the strength of the transom. They are available in multiple gross heights: 150, 180, 210, 240, and 270mm.

As an alternative to milling, KLP Shims, made from the same polymer as the bridge transoms, can be used to either compensate for height variations, or achieve a desired camber in curved tracks. KLP Shims are available in thicknesses of 2mm, 5mm, and 10mm. Type 301 uses insert blocks and offers the solution for bridges with canted conditions, with a total height range of 130 – 240 mm per mm. Using a combination of the various solutions offers a potential stepless height range from 130 – 270mm.

Low-profile solutions
For track owners with shallow ballast beds or the need to lower their track, low profile KLP Hybrid Polymer Sleepers can be an attractive option. Despite their height of only 130mm, the strength of steel reinforcement combined with the dampening characteristics of polymer delivers the required dynamic stiffness of the sleepers they replace. These sleepers can handle 25 tonne axle loads.

Quality control
The reliable function of hybrid sleepers is very dependent on consistent quality of the raw materials used, together with reliable manufacturing processes and effective quality control. KLP are made from recycled polymers. If the raw material used in the manufacture is not properly controlled, recycled polymers can vary hugely in consistency and performance. Effective processes are required to prevent the risk of inconsistent quality of raw materials. The principles of ISO standards 9001 (Quality), 14001 (Environment) and 45001 (Safety) are embedded in our corporate culture.

Manufacturer Lankhorst sources raw materials from reliable suppliers with proven quality control processes who deliver to Lankhorst’s exacting quality requirements. A sample from each batch of raw materials delivered to the factory is analysed. Properties verified include the melting point, impact, moisture, and density. Prior to producing the sleeper, a laboratory sample is made of the composite polymer. Tests such as stiffness, strength, stretch, and impact are performed on this sample, making sure that the final product will be fit for purpose. Sleepers are checked for weight and dimensions. Verification of materials.

 

Approvals have been obtained in several countries for the sleepers. Extensive testing on various parameters like thermal expansion test, bending and cyclic test, vibration abrasive test, electrical resistance test, lateral resistance test confirmed compliance to requirement. Test results are available on request via info@linkap.com.au.


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