Braking - Braking test bench conditions for simulating descents on steep gradients

UIC WG B 126.3 was tasked by SET 7 with checking the pertinence of the test conditions and acceptance criteria of UIC Leaflet 541-4 (3^rd edition, April 2007), which allow brake blocks to be guaranteed as suitable for braking wagons travelling downhill on the steep gradients of Alpine passes.

The aim of the present study is to determine whether the bench test method for assessing the suitability of brake blocks for use on steep gradients as per UIC Leaflet 541-4, which has been in use for many years already, still represents the latest state of the art and is compliant with operational requirements.

The process consisted in:

Preliminary work involving comparison between bench tests according to different brake application methods: saw-tooth brake applications, braking with a constant application force and braking with constant power.

Secondly, updating data concerning topography and operations on steep gradients.

Thirdly, determining maximum powers for reference trains.

Finally, the working group prepared recommendations for UIC Leaflet 541-4:

The tests currently prescribed in the UIC leaflet (45 kW and 34 mn) are pertinent.

An additional test phase at 40 kW for 30 mn can be prescribed as a supplement in case of non-compliance with the criteria for 45 kW - 34 mn. In such cases the brake block will have to be assessed on steep gradients during the service test.

The working group has also proposed that the acceptance criteria for drag braking on test benches be adjusted.