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Multiple steps collide to activate 'missing step' switch and halt escalator

Incident Investigation

Multiple steps collide to activate 'missing step' switch and halt escalator

March 11, 2018

Elevating Devices

Reference Number:

II-663374-2018



Incident overview

Multiple steps collided with each other at the lower landing, causing a missing step switch to activate and shut the system down.

Regulated industry sector

Elevating Devices - Escalator

Location

Vancouver, BC

Investigation conclusions

Site, system and components

Escalator is an vertical transportation system in the form of a moving staircase which carries people between floors. It consists of a motor-driven chain linked to aluminum steps on a track which cycles on a set of guides. Multiple safety switches are in place to ensure that the system is running as intended, any deviation from the manufacturer’s specification causes the system to shut down.

Failure scenario(s)

The escalator controller shut the system down due to a “missing step” switch being activated. A gap between two escalator steps was larger than the allowed manufacturer’s specification, resulting in the controller faulting out as designed.

Facts and evidence

During a Site visit:

  • 2 steps were fractured completely due to the pileup, the step chain was damaged due to the incident.
  • Photos of the gap between steps
  • The last fault log in the escalator controller indicates a missing step switch being activated.
  • Indentation on the landing plate indicating a heavy impact to the plate.

Causes and contributing factors

It is highly likely that the visible indentation on the landing plate indicates a heavy impact, possibly causing the steps to not be aligned and piling up at the bottom landing.

Impact

  • Injury
    • Qty injuries: No injuries reported
    • Injury description: N/A
    • Injury rating: N/A

Damage

  • Damage description: Several escalator steps, and the step chain were damaged due to a pile up (steps colliding with each other) at the bottom landing.
  • Damage rating: Minor
  • Incident rating: Minor
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