Burj Khalifa BMU's by CoxGomyl
To service the facades of the 828 m high structure, 3 permanent parapet mounted BMUs were installed at each of Levels 40, 73 and 109. These track-mounted and telescoping systems are operate on a horizontal track which has been installed on Burj's exterior façade. The machines are very flexible in their operation and are able to luff, telescopic, hoist, slew and travel. The average outreach of these machines is 10 m, retracting to 5 m for the parking configuration.
3 further fixed position machines are located at Tiers 19, 20 and 21 with outreaches of 21.5 m from the centre of rotation.
The Tower Spire above Tier 21 (624.1 m) is maintained by 6 separate systems, including 3 smaller Hawk Units and 3 davits for the uppermost areas.
A total of 18 machines have been delivered to the building and the higest operating BMU in the world working at 715 meters.
More info here