Patent GB-1493056-A (GB)
Title: Testing air brake systems
IPC: G01M17/007
Filed: 1975-01-31
Abstract: 1493056 Testing air brake systems SOUTHERN PACIFIC TRANSPORTATION CO 31 Jan 1975 [1 Feb 1974] 4352/75 Heading F2E [Also in Division G1] To test for excessive leakage in the air brake system of a railway train, a rail yard air supply is coupled to the head end of the brake system via a coupling 32 and air is supplied to the system until both a predetermined pressure (e.g. 75 p.s.i.) determined by a pressure transducer 38 has been obtained at the head end and until a predetermined time (e.g. about 11 min.) determined by a timer 102 has passed; thereafter the pressure at the head end is reduced to a second predetermined level (e.g. 60 p.s.i.) determined by a transducer 40; thereafter a further period of time (e.g. 1 min.) determined by a timer 130 is allowed to elapse and if during this time the pressure reaches a third level (e.g. 55 p.s.i.) as determined by a transducer 42 then an indication is provided that the brake system has failed the test.  Fig. 1 illustrates a railroad yard with a testing system wherein a valve, sensor, and control complex 14 is mounted near the track 10, and a control panel 18 is located remote from complex 14 but connected thereto by electrical conductors 20. Once the lead car 121 of the train has been connected to a rail yard air supply pipe 22 via coupling 32 of complex 14 and a hose 34, an operator at the control panel 18 can perform the test. The general arrangement of the testing system is illustrated in Fig. 2 (not shown) but Fig. 3 shows a more detailed view of the system. As shown in Fig. 3 the valve and sensor complex 14 includes a solenoid operated main valve 30 controlling the supply of air from pipe 22 and a solenoid operated reduction valve 46 to enable bleed-off of air from the brake system. A pressure sensing tube 36 connects with the transducers 38, 40, 42. The operator can control testing in accordance with the setting of a switch arm 54 movable between contacts 56, 60, 62, 63 When the switch arm 54 is moved to "test" contact 60 the transducer 38 and timer 102 are put into operable states, valve 30 is opened and the testing sequence is begun. After both 75 p.s.i. has been reached and the 11 minute period has passed, the main valve 30 is allowed to close and a relay 110 is operated to cause supply of current to a "system" charged indicator light 124 for a period of 45 seconds determined by a timer 112. After the 45 second period the light 124 goes out and a relay 117 is energized to cause supply of current to transducer 40. So long as transducer 40 senses a pressure greater than 60 p.s.i. the valve 46 is held open. When the 60 p.s.i. level is reached the transducer 40 delivers current to the 1 minute timer 130. If the pressure exceeds 55 p.s.i. at the end of 1 minute a pass light 64 is illuminated-if the pressure falls below 55 p.s.i. during the 1 minute the fail light 66 is lit. If a leakage test has been failed and a retest is necessary the arm 54 may be contacted to a contact 62 which causes a test as before but with the elimination of timer 102. A contact 63 may be used to hold main valve 30 open for an indefinite time for charging the brake system up to the pressure of the yard air source.