The snap switch is located inside the HSR switch and EPD is used to detect whether the switch rail and crossing of the turnout is tightly adhered to the stock rail. Snap switch modules include single-row (used in EPD), four-row (used in switches) and six-row modules.
Manufacturing defects are the major cause of snap switch malfunctions that will result in incomplete contact. Incomplete contact at any point will cause short circuit and the signals indicating adhesiveness of the turnout will not be successfully transmitted. Then, the switch will display turnout error leading to malfunction of train operation. When encountering this error, engineers will be dispatched to the site immediately to confirm the error and troubleshoot to restore normal operation as soon as possible. Although the process will cause inconvenience and delay to passengers, operational safety will not be jeopardized.
Currently, measures to improve the troubleshooting process of snap switch errors include:
1. Enhancing manufacturing Inspection measures- the manufacturing company has implemented improvement measures to the original snap switch manufacturing process and added optical inspection procedure to their QC routine.
2. Increasing incoming inspection measures- each incoming snap switch will have to pass over 100 tests on the snap switch testing platform performed by THSRC before taken into the warehouse.
3. Increasing outgoing inspection measures- each snap switch taken out of the warhouse will have to pass over 1000 tests on the snap switch testing platform before being sent to construction site.
4. Enhancing installation tests- after installation of the snap switch in switches or EPD, the turnout has to be tested over 10 times before official operation.