A Comparison Study of Testing 120 Control Valves on Two Different Test Rigs for Second-Phase Emergency Brake

As a 120 control valve may be tested by either 705 test rig or new 120 valve test rig,the equivalency of the test results by above two test rigs is assessed by using a pneumatic brake simulation model.The simulation model,based on air flow theory and functionalities of both the 120 control valve and the two types of test rigs,simulates the test of 120 control valves during second-phase emergency brake by both the 705 Test Rig and New 120 valve test rig.The simulation results show that the two test rigs are not equivalent when qualifying the 120 valves during the second-phase emergency braking.It is possible that a 120 control valve that is qualified by one test rig would fail to be qualified by the other.It is shown that a 120 valve,with very slow charging speed and low initial charge pressure to the brake cylinder but meeting the test criteria on the 705 test rig,may not meet the test criteria by the New 120 valve test rig;conversely,a 120 valve that has very fast charging time and high initial charge pressure to the brake cylinder on the new 120 valve test rig,may be disqualified if it were tested on the 705 test rig.This study provides helpful insight into the design and criteria setting of brake control valve test rigs.