Typically the base which is bolted into a large concrete pad provides the crucial support for a tower crane. The base is connected to a mast or a tower and stabilizes the crane that is connected to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is usually a triangulated lattice structure that measures 0.9m2 or 10 feet square. Connected to the very top of the mast is the slewing unit. The slewing unit consists of a motor and a gear that allows the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the minimum lifting capacity of a tower crane is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are used to be able to make sure that the operator does not overload the crane. There is also one more safety feature referred to as a load moment switch to ensure that the driver does not exceed the ton meter load rating. Finally, the tower crane has a maximum reach of 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will at first have to be brought to the construction location by utilizing a huge tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the equipment portion of the jib and the crane. These sections are then connected to the mast. Next, the mobile crane adds counterweights. Forklifts and crawler cranes may be some of the other industrial machinery which is commonly used to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height can match the building's height. The crane crew uses what is known as a top climber or a climbing frame that fits between the top of the mast and the slewing unit. A weight is hung on the jib by the work crew in order to balance the counterweight. When complete, the slewing unit is able to detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an extra 6.1m or 20 feet. Next, the crane operator utilizes the crane to insert and bolt into position one more mast part piece.