An overhead crane system covers a rectangular area which moves load side to side and backward and forward. To move extremely heavy or bulky loads through the overhead space in a facility, instead of through aisles or on the floor, an overhead crane (also called an industrial crane, crane, or overhead traveling crane) is a machine that lifts, lowers and moves a load horizontally. An overhead crane system has high lifting capacities for load movement. There is a lifting device called a hoist which is mounted on a trolley for horizontal movement across a bridge beam connected to one or more horizontal girders that are supported at either end by end truck. The end trucks are attached at right angles to the girders and move on fixed runways. The horizontal travel of push type cranes is powered manually by the operator; alternatively, an electric overhead crane system is powered by electricity while some other cranes are air-powered. Crane travel is directed by an operator, either manually or with a wired pendant station or wireless controls that guide their electric- or pneumatic-powered travel. Typical uses include multi-directional movement of materials to support manufacturing, storage, loading or unloading activities inside a facility, outside in a yard, or at a railway or shipping port. Cranes come in a variety of styles and are used with a number of attachments to facilitate load lift, including:
Overhead Crane System | Types
Single girder crane – This utilizes a single bridge beam attached to the two runways and end trucks. This bridge beam or single girder supports a lifting mechanism or hoist that runs on the bottom flange of the bridge beam; also referred to as an under running crane or underhung crane.
Double girder crane – These cranes utilize two bridge beams set atop the runway end trucks. They typically incorporate a top running trolley hoist which moves along the top of the two bridge beams on its own set of wheels for increased headroom under the crane; also called a top running crane.
Box girder crane – Utilizes a four-sided box configuration in fabricating the bridge girder. This enhances the crane’s load capacity and accommodates wider bridge distances. Generally, they are utilized in pairs with the hoisting mechanism operating on rails attached to the top of each box girder.
Truss girder crane – A crane designed with structurally reinforced bridge girders for greater span and loading capabilities.
I-beam crane – Utilizes standard I-beam as the bridge girder and may also employ I-beams as the runway beams.
Straddle crane – Configured to straddle a load and often on wheels, these cranes are typically used in lumber yards or to move large containers at seaports.
Tower crane – This can handle very large, heavy loads at construction sites and for the loading and unloading of shipping containers.