Case Study – Amusement Park Ride Breakdown

Assigned Task:

S-E-A was asked to consult with respect to the cause of the accident and review the existing expert report.

S-E-A’s investigation began with an exhaustive review of the existing documentation and photos including witness reports, product specifications, maintenance records, parts orders and safety procedures.

S-E-A also observed the machine in operation and took field notes and photos.

S-E-A performed laboratory inspection of the seal, roller bearings, locknuts, locking washer and spacer.

Observations were recorded in the form of laboratory notes and photographs.

Test evidence was evaluated resulting in the following findings:

• The ride was operating normally when the rotation and lift assemblies decoupled. This caused the lift arms to descend and lower the rider’s seats. Since the ride’s tilt function was operating at the time, some of the seats contacted the ground as the ride came to a stop.
• The cause of the decoupling was a poor fit within the assembly.
• The poor fit allowed the rotating spacer to transfer torque to elements not built to handle the force.
• The torque magnitude increased over time, eventually causing part of the lock washer to shear off.
• The cause of the loose fit was due to the spacer being misshaped.
• The oxidized grease observed on the spacer was an indication that it had been involved in a previous failure.
• Under normal application conditions, the spacer would not have experienced significant wear, but it may have been damaged during a previous rebuild.
• There was no evidence of poor or inappropriate design.

As a result of S-E-A’s findings, the manufacturer and their customers realized this was an isolated incident which was unlikely to occur again. The manufacturer and their customers were able to move forward without the devastating financial and logistical ordeal of a mandatory recall.

While painstaking research, engineering expertise and sophisticated lab equipment are key elements in reaching a sound scientific conclusion, the multi-disciplinary teams at S-E-A are a large part of the reason why we have been able to help so many clients find real answers. Our scientific methodologies cross all disciplines and our wealth of experience solving a wide range of problems is invaluable in assuring broad perspective and thinking unfettered by familiarity and repetition.