What is claimed to be the world’s highest compact work platform is in action on the world’s tallest building, the Petronas Towers in Kuala Lumpur, Malaysia.

The Spider TST 55 access platform, which has a 55m reach, was developed and built in Denmark by E Falck Schmidt and is equipped with Danfoss hydraulic components, whose PVG 32 proportional valves control functions, such as lift, extend, slew, outriggers and torque regulation.

E Falck Schmidt introduced the Spider concept for work platforms in the 1970s and has since shipped several hundred machines based on this concept all over the world.

Though produced for working heights between 14m and 55m, the platforms are compact when lowered for storage.

The Spider TST 55 forms part of the permanent maintenance equipment in the newly built Kuala Lumpur City Centre (KLCC), of which the 452m-high Petronas Towers are a part.

The two towers are connected by a “sky bridge” 175m up. In addition to the twin towers, KLCC also has offices, museums, hotels, congress centres, banks, and a large shopping centre – all amid large tropical parks and gardens.

In line with the rest of the building complex, the shopping centre at the foot of the Petronas Towers is also of impressive dimensions. The height to the ceiling is more than 55m. The roof of this building is a huge glass and steel dome. When the shopping centre was being built, consideration was first given to installing permanent walkways to give maintenance personnel access to the various installations, and to the large areas of glass in the roof. But this idea proved too expensive and inelegant, offering an opportunity for the Spider to show what it could do.

Because the specially-designed access platform has to work both inside and outside the shopping centre, it has additional power and safety system features. The TST 55 is self-propelled and sits on a five-axle chassis in which propulsion is provided through hydraulic transmission. It has a telescopic boom with seven extending sections. All functions are operated by means of Danfoss joysticks type PVRES.

The work platform has outrigger support legs with individual adjustment both horizontally and vertically, enabling it to work where space is limited or outdoors on uneven terrain.

There are three power systems all capable of operating independently of each other: a diesel drive system; an electric (415V, 50Hz) oil pump system; and a battery-driven pump system for emergency lowering of the basket should the two other systems fail.

The diesel drive system means that the platform is not dependent on the building’s power supply and allows the platform to be used outdoors. For indoor duty it can be connected to the electricity supply and operate more quietly.

The platform chassis can be operated from a portable control panel in either normal drive, round steering or crab steering for added manœuvrability around the obstacles of the shopping centre. It is operated via a programmable TM 4210-PVG hydraulic controller and a feedback potentiometer from each of the ten wheels.

The slewing function is equipped with a Reggiana Riduttori gear type RR 180/70 with integrated negative brake built together with a Danfoss motor type OMSS 315.

Another constraint on the designers of the Spider TST 55 was that maximum surface pressure could not exceed 7kg/cm2, for fear of cracking the specially imported Italian marble floor tiles. The 17t unit exerts a maximum of 5kg/cm2.

Since the work platform was to be kept in the basement car park of the centre when not in use, it had to be able to negotiate a gradient of 7°. The new work platform will climb gradients up to 10°.

The dimensions of the platform when lowered were also restricted as it had to be able to get through a normal doorway to get to the basement. This was facilitated by making the basket removable without using tools. The height of the unit when lowered is 2.1m, its length is 10.5m and its width 1.6 m.