Investigation of application delays in Australian train brake systems

A brake pipe system consisting of 120m of pipe and four triple valves was assembled to test the response of the pipe and triple valves with variations on branch pipe, bulb size and the triple valve design. The rig included one combined reservoir relay type and three triple valves directly connected to auxiliary reservoirs and cylinders. The research work established that it was possible to propagate valve operations in a pipe at sonic velocity if pressure profiles and bulb volumes were optimal. The reasons why propagations are limitedto 100-150m/s for minimum and service applications and 250 m/s for emergency applications are discussed.It was also established that larger ‘gulps’ in brake pipe pressure can be achieved with either larger bulbsand/or less restrictions to bulb mass flow. Branch pipe diameter was also found to be significant to bulbmass flows. The change to the use of combined reservoir relay type systems was identified as a significant source of reduced performance of the bulb resulting in reduced ‘gulp’ in the brake pipe. Recommendations are made for the improvement of existing systems and for directions of future research.