June 2019

n BRAKES, CLUTCHES AND COUPLINGS Ensuring that Singapore airport’s floating petals do not drop V isitors to Terminal 4 of Singapore’s Changi airport can now experience a large kinetic sculpture above their heads in the form of ring-shaped aluminium“petals”that move slowly in time to specially composed music. The 96 elements are based on the shape of orchid leaves. They move in a precisely coordinated pattern, constantly forming new arrangements. The installation, called Petalclouds, has been operating since last year in the terminal which opened in 2017. A stylised orchid petal runs as a red theme throughthe terminal. Hence the shape of the elements and the name of the work of art. The TÜV-certified installation was designed by Berlin-based ART+COM Studios, and built and installed by another German firm, MKT, based near Munich. Safety was paramount when designing and constructing the assembly which“floats”above the passengers with no protective screen. If just one of the petals were to fall, there would be a high risk of injury to people in the busy concourse below. “We have installed hundreds of safety elements in the Petalclouds,”says Dipl-Ing Werner Riebesel, who was responsible for the project at MKT.“The difficulty was to keep the system running smoothly without the safety components shutting everything down with false alarms. That was especially important because of the project’s location in Singapore – you can’t go there for every little problem.” Although it might appear lightweight, each of the rings in the 200m-long sculpture weighs 40kg, and the total weight of the steel and aluminium structure is around four tonnes. Each element is suspended by four thin steel cables below the 25m-high ceiling of the terminal’s Central Galleria. The flowing movements of each petal are achieved using a pair of servomotor-driven winches. There are two emergency brakes on each winch. The Mayr Roba-stop-M brakes are controlled by Roba-SBCplus modules, also supplied by Mayr. The modules (which comply with PL e and SIL CL3) avoid the need for mechanical safety components. Each one controls two brakes, saving space in the control cabinet. They can evaluate the release monitoring of the brakes, thus determining whether they are open or closed at any time. The winch motors only run when the brakes are open, thus avoiding possible costly damage to the drives. The brakes used on the sculpture work on the failsafe principle. They close in a de- energised condition, and also in event of a power failure or an emergency stop. When the current is switched on, the brake generates a magnetic field, pulling the armature disk towards the coil carrier against the pressure of a spring. A rotor, connected to the bearing- mounted pinion shaft via a gear hub, is therefore free and the brake is released. The motor can run freely, and the wire rope hoist can move in either direction. If there is a power failure or an emergency stop, the brakes will intervene immediately and bring the wire rope hoist reliably to a rapid stop. Even if the brake is damaged – for example, due to cable breakage or failure of a magnetic coil – the braking torque will be maintained. n The sculpture’s“petals”are controlled by servomotor- driven winches, each tted with electronically- controlled emergency brakes The Petalclouds sculpture moves gently above the heads of passengers at Singapore’s Changi airport CENTAFLEX-B 01274 531 034 • WWW.CENTA-UK.CO.UK/DRIVES

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