Contents I. Introduction
Block brake is an important safety component of passenger elevator, and its reliability is the key guarantee for passengers' life. With the long-term use of a passenger elevator, the parts such as the brake shoes on a brake will be worn out due to long-term use, which leads to its braking performance represented by braking torque cannot meet the design requirements, and it affects the safe use of passenger elevator, and in serious cases, even leads to safety accidents. According to statistics, the failure of the brake and other safety components accounts for a sizable portion of the total number of causes of elevator safety accidents[1]. In March 2020, the inspection unit in Guizhou Province carried out an upward overspeed protection action test on an elevator that had been in use for 12 years, and the brake was de-energized but could not act normally until the counterweight compacted the buffer under the action of gravity, and the potential safety hazard was eliminated in a timely manner after the incident[2]. On May 23, 2021, the A elevator hoisting accident occurred in a small area of Zhanjiang City, Guangdong Province. The elevator accelerated from the 1st floor and crashed into the roof of the 30th floor, resulting in the unfortunate death of a passenger[3]. After investigation, it was found that the elevator lacked maintenance for a long time and no brake capacity test was conducted. This paper explores the failure mode and performance degradation process of passenger elevator brakes according to the working principle and characteristics of brakes, analyzes the degradation pattern of braking performance, evaluates the reliability of the block brakes, predicts the remaining working life of the block brakes, warns of failures in advance, and improves the safety of elevators to maximize the safety of passengers' lives.
