Ride operating at a speed higher than manufacturer's instructions causes discomfort

Incident Investigation

Ride operating at a speed higher than manufacturer's instructions causes discomfort

August 7, 2018

Amusement Devices

Reference Number:

II-729058-2018 (8210)

Incident overview

The amusement ride was operating at a speed (RPM) over the manufacture specifications. A rider became unconscious and complained of sore ribs and neck.

Regulated industry sector

Amusement Devices - Amusement ride



Investigation conclusions

Site, system and components

The amusement ride is driven by hydraulic power. A hydraulic pump provides the flow of hydraulic fluid to hydraulic motors. The hydraulic motor execute the operation of the ride. A hydraulic flow control (restrictor) valve is placed between the pump and motor. It is used to reduce the fluid flow rate which will reduce actuator (hydraulic motor) speed.

Failure scenario(s)

The hydraulic flow control valve was not secured in a set position. This amusement ride is setup and moved on weekly basis, allowing for components to become inadvertently adjusted.

Facts and evidence

Incident Investigation the following day discovered:

  • A lock nut (jam nut) was missing on the hydraulic flow control valve
  • Ride was recorded operating 20% over speed
  • Daily ride checks did not include ride RPM
  • No documentation of ride speed for this setup location

As reported by the rider:

  • Fell unconscious during ride
  • Complained of sore ribs and back
  • Seated with son and daughter

As reported by the contractor:

  • Rider exited by herself unassisted
  • Daily checks were performed prior to operation
  • Each setup owner/contractor operates each ride, not documented

Causes and contributing factors

It is very likely that a missing lock nut on the hydraulic flow control valve caused the valve to be adjusted resulting in ride operating too fast. The incompleteness of the daily and setup checks of ride speed is a contributing factor.


  • Injury
    • Qty injuries: 1
    • Injury description: Sore ribs and neck; fell unconscious; squished by other passengers
    • Injury rating: Minor


  • Damage description: None
  • Damage rating: None
  • Incident rating: Minor
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