What is the minimum upward thrust that hangers for power-operated doors should withstand?

The minimum upward thrust that hangers for power-operated doors should withstand being set at four times their weight is based on safety and performance standards in elevator design. This requirement ensures that the hangers can effectively support the dynamic loads and forces that occur during operation, including impacts and stress that can arise from the impact of the doors opening and closing.

By requiring hangers to withstand four times their weight, the design takes into account safety margins to accommodate unexpected loads and wear over time. This precaution helps prevent structural failure, which could lead to potentially dangerous situations for both passengers and maintenance personnel.

Other options suggest different multipliers of weight, but the established standard is focused on striking a balance between safety and reasonable design practices in elevator systems. Adhering to the four times standard helps maintain compliance with safety regulations and enhances overall reliability in the system's operation.