Published on: Mar 19, 2017
To a layman a tower crane may appear insecure and about to fall over anytime when lifting or hauling loads but the handlers of the cranes know very well that this is unlikely. That’s because, tower cranes are constructed according to tried and tested methods based on sound engineering measurements. Right from constructing the crane to handling it, there are best practices that the operators follow in order to ensure optimum performance of the cranes and also to ensure that there are no mishaps or accidents due to poor handling.
The basic components
The base comprises of a large concrete pad which normally measures 30 ft x 30ft on the surface and 4 feet deep below the surface. The total weight of the pad is 182,000 kgs. The tower or mast stands on this pad and is held tight and erect with the help of anchor bolts that are embedded deep into the pad. The strong pad at the base is what gives the tower its strength when it is given height. At the top of the tower is the slewing unit which includes the gear and motor that helps the crane to rotate.
Tower cranes normally have four main specifications. Maximum unsupported height refers to the maximum height that will be supported by the base pad. In this case, the maximum unsupported height of a tower crane is 265 feet and beyond that height, it would have to be tied to a rising building closest to it. Maximum reach refers to the horizontal arm of the crane at the top known as the jib, which can reach up to a maximum of 230 feet. Maximum lifting power of the crane is 19.8 tons when the load is closest to the vertical tower of the crane.
It needs to be noted that if the load is barely 30 meters away from the tower, the load-lifting capacity goes down to a maximum of 10.1 tons. Counterweights weighing 20 tons are needed to balance the load that the crane lifts during operations. For the operator of the crane, there are limit switches that inform him about the loading limit during the process of loading. When the tower crane arrives at the construction site the handling crew assembles the units with the help of a mobile crane. The tower mast has a triangulated lattice structure that adds to its strength to remain firm and steady.