Used Self Erect Cranes Virginia - The tower crane's base is typically bolted to a huge concrete pad which provides very crucial support. The base is connected to a tower or a mast and stabilizes the crane that is attached to the inside of the building's structure. Often, this attachment point is to an elevator shaft or to a concrete lift.
Usually, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is attached to the very top of the mast. The slewing unit is made of a motor and a gear which enable the crane to rotate.
Tower cranes may have a max unsupported height of 80m or two hundred sixty five feet, while the minimum lifting capacity of a tower crane is sixteen thousand six hundred forty two kilograms or 39,690 lbs. with counter weights of twenty tons. Moreover, two limit switches are used in order to make certain that the driver does not overload the crane. There is also one more safety feature referred to as a load moment switch to ensure that the operator does not exceed the ton meter load rating. Lastly, the maximum reach of a tower crane is 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, particularly due to their extreme heights. First, the stationary structure has to be transported to the construction site by utilizing a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the machinery portion of the crane and the jib. Afterwards, these parts are connected to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes may be some of the other industrial equipment which is used to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height is able to match the building's height. The crane crew utilizes what is called a climbing frame or a top climber which fits between the slewing unit and the top of the mast. A weight is hung on the jib by the work crew in order to balance the counterweight. Once 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 additional 20 feet or 6.1m. Next, the crane driver utilizes the crane to insert and bolt into place one more mast section piece.
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