Session: 12-03-05: General: Mechanics of Solids, Structures and Fluids

Paper Number: 144445

144445 - Failure Analysis for Lock Sensing Limit Switch on Emu Door System 

The door system on modern railway vehicles is a crucial key to ensuring smooth operation and passenger safety. The safety loop, including the lock sensing limit switch and close position limit switch of the door system, is a key part to ensure the safe routine operation. Any malfunction in these switches during operation could disrupt traction initiation, posing significant operational challenges. At the beginning of 2021, railway authorities report incidents of safety loop failures in plug sliding doors across different train series. These failures prompt a comprehensive analysis to identify the root cause and propose effective solutions to ensure safety and normal operation of the mentioned Electric Multiple Unit (EMU) series. Initial data collection reveals that safety loop failures occur across different EMU series built based on different train platforms. Comparative analysis across vehicle models shows consistent safety loop configurations, typically consisting of the main lock limit switch and the closed position limit switch wired in series.

Upon inspection of current units, sporadic lock sensing limit switch malfunctions emerge as the primary cause of safety loop failures. Consequently, this paper aims to conduct an in-depth analysis of lock sensing limit switch failures on different train series, focusing on identifying the underlying issues and proposing practical solutions.

The limit switch is composed of a shell, contact point sliding seat, leaf spring, reset spring, holding shaft, static contact points, dynamic contact points, enforced disconnection pressing pad. Based on it, the analysis process involves several key steps using the fault tree method.

First, measuring and comparing the actuation forces of failed lock sensing limit switches with properly functioning ones to identify any discrepancies or abnormalities.

Second, measuring the cooperation between the leaf spring and the operation sliding plunger to ensure smooth operation and proper engagement for the switch’s actuation.

Third, measuring the fit between the operation sliding plunger and the shell to identify any misalignments or inconsistencies that could affect switch performance.

Fourth, testing for looseness in the static contact points and examining the dynamic contact points for deviations in position to identify potential sources of malfunction.

Fifth, observing the contact points for signs of electrochemical oxidation, which could degrade switch performance and reliability over time.

Through the examination, the root cause of safety loop failures is identified. It is determined that a manufacturing defect in the cooperation between the leaf spring and the operation sliding plunger is causing the failure. The activation distance of the limit switch exceeds the proper working range. Based on these findings, practical solutions are proposed to address the malfunction effectively and enhance the safety and reliability of plug sliding doors across different train series.

Overall, this comprehensive analysis provides valuable insights into the underlying issues affecting safety loop performance and lays the groundwork for implementing targeted solutions to mitigate future failures and improve overall system reliability.

Presenting Author: Hang Lu CRRCMA

Presenting Author Biography: Hang Lu is a newly joined mechanical engineer within the railway vehicles industry. She completed her bachelor’s degree at Rensselaer Polytechnic Institute, where she spent four years studying various fundamental aspects of mechanical engineering. Subsequently, she pursued advanced academic studies in the integration of mechanical engineering, electrical engineering, and software at Columbia University, earning her master’s degree.

Her entry into the industry commenced with CRRC MA, marking her initial step. Here, she developed a profound interest in door systems. Under the guidance of knowledgeable door system engineers, she applied her knowledge to address authentic industry challenges and was inspired to seek enhancements.

Authors:

Lvxian Wu CRRCMA
Haifeng Hong CRRCMA
Xiaoming Zhang CRRC Changchun
Long Zhang CRRCMA
Hang Lu CRRCMA
Dong Li CRRC Changchun
Yanbo Yin CRRC MA Corporation
Yuxuan Tang CRRCMA
Wei Huang CRRCMA
Qiubo Chen CRRCMA