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SHAH ALAM – A safety certificate may confirm that an amusement ride meets requirements at the time of inspection, but it cannot guarantee that the machine will remain safe throughout its operation, engineering experts warn.
Malaysia University of Science and Technology School of Transportation and Logistics dean Associate Professor Dr Khairir Khalil said amusement ride safety should instead rely on a continuous system involving proper design, preventive maintenance, competent personnel, inspection, testing and monitoring.
Khairir, who has engineering and manufacturing experience involving machinery maintenance and safety audits, said repeated loading could cause fatigue in critical components of high-speed rides such as roller coasters.
He said thousands or even millions of load cycles could subject structural components to stresses from passenger and train weight, acceleration, braking, vibration and changes in direction.
“More commonly, a small crack develops at a location where stresses are concentrated, such as a weld, bolt hole, sharp change in geometry, joint or other discontinuity.
“The crack can then progressively grow with repeated loading until the remaining section of the component is no longer capable of carrying the load safely,” he said.
Khairir said similar fatigue mechanisms could potentially affect metal cables used in roller coaster cars, making fatigue assessment necessary both during the design stage and throughout the ride’s operating life.
He said routine visual inspections could detect visible cracks, deformation, corrosion and other abnormalities, but critical components might require non-destructive testing (NDT), including ultrasonic, magnetic-particle or dye-penetrant testing.
He said Occupational Safety and Health Department (DOSH) guidelines already recognised the importance of such examinations, including checks on critical welds, bolts, pins and joints, while technical documentation was also expected to include stress and fatigue analysis.
Universiti Sains Malaysia School of Civil Engineering lecturer in structural engineering Associate Professor Dr Fatimah De'nan similarly stressed that fatigue could develop when steel structures were subjected to repeated or cyclic loading over an extended period.
She said acceleration, braking, vibration and passenger loading could create fatigue stresses, particularly around welds, connections, bolt holes and other areas where stress was concentrated.
“Visual inspection is important, but it may not detect small or hidden fatigue cracks. Therefore, non-destructive testing (NDT) such as ultrasonic, magnetic particle or dye penetrant testing may be necessary for critical components,” she said.
However, Fatimah stressed that metal fatigue should not be assumed to be the cause of any particular incident before an official technical investigation is completed.
Her comments came after an incident involving an attraction at Sunway Lagoon on Aug 22. Sunway Theme Parks had said it was cooperating fully with the relevant authorities, while Subang Jaya police chief Assistant Commissioner Wan Azlan Wan Mamat reportedly said 10 people sustained minor injuries.
“The actual cause of the Sunway Lagoon incident, however, should only be determined after the official investigation,” she said.
Beyond identifying possible faults, both experts said the people responsible for inspecting and maintaining amusement rides must possess the appropriate technical expertise.
Khairir said a high-speed amusement ride was not merely a mechanical machine, but a complex system involving structural and mechanical engineering, materials, welding, electrical and electronic controls, hydraulics or pneumatics, safety systems and human factors.
“The DOSH guidelines are quite clear on this point.
“They state that a person inspecting an amusement device should have formal engineering qualifications and experience comparable to those of the designer, and should be capable of making engineering judgments about the seriousness of faults, inspection intervals and appropriate repairs,” he said.
He added that NDT work should also be conducted and evaluated by personnel recognised by the relevant industry body or regulatory authority.
Fatimah said amusement ride inspection was a specialised field requiring knowledge spanning structural and mechanical engineering, fatigue, welding, NDT and relevant safety standards.
“Malaysia has qualified engineers and NDT specialists, but amusement ride inspection is a relatively specialised field. For high-risk rides, I would support the involvement of competent and appropriately certified specialists, preferably through an independent inspection team,” she said.
The experts also cautioned against treating an inspection certificate as a permanent assurance of safety, as ride conditions could change after an examination.
Khairir said components could deteriorate, bolts could loosen, cracks could develop, safety devices could malfunction and maintenance or operating errors could occur after an inspection had been completed.
“An inspection or certificate should be understood as an important safety control, but not as a permanent guarantee that a machine will remain safe under all circumstances until the next inspection,” he said.
Fatimah said safety could also be affected by wear and tear, corrosion, maintenance quality, assembly, operating procedures and weather conditions.
“Therefore, safety should be treated as a continuous process, involving proper operation, daily checks, preventive maintenance and periodic detailed inspection, not simply relying on an inspection certificate,” she said.
Both experts said temporary amusement rides deserved particular attention because they could be repeatedly dismantled, transported and assembled at different locations.
Khairir said existing DOSH guidelines already required thorough inspection by an authorised person before a temporary amusement device was used at each installation.
He said the guidelines also required records covering erection, dismantling, storage, maintenance and inspection, while a certificate of fitness would become void once an amusement device was dismantled and relocated.
“A ride which has been transported and reassembled is no longer exactly in the same condition as when it was previously inspected,” he said.
Fatimah similarly supported additional scrutiny for temporary rides, saying transportation and reassembly could introduce risks involving damaged connections, misalignment and incorrect assembly.
“For critical rides, periodic independent inspection and NDT of fatigue-sensitive components would provide an additional layer of safety,” she said.
Khairir said inspections should ultimately be based on the level of risk rather than applying an arbitrary inspection frequency to every ride.
He also called for greater independence in safety inspections, particularly where commercial pressure could encourage operators to keep attractions running.
“The person responsible for inspecting the safety-critical condition of a ride should be sufficiently independent from the commercial pressure to keep the ride operating,” he said.
Fatimah said the objective should be to identify deterioration or defects early enough to prevent an accident rather than merely determine what went wrong after a failure.
“Overall, from a steel engineering perspective, the key is not only to detect a failure after it occurs, but to identify fatigue, deterioration or defects early enough to prevent failure,” she said.
Khairir said amusement ride safety should ultimately be approached in the same manner as other safety-critical machinery, where no single certificate, inspection or individual could carry the entire responsibility.
“Safety comes from a system of design integrity, competent people, preventive maintenance, inspection, testing, proper operation and continuous monitoring,” he said.