What Is a Gantry Crane?
A Gantry Crane is a machine designed for lifting, moving, and lowering heavy loads.
It features a structure resembling legs at both ends of the overhead beam (girder) of an overhead crane, traveling on rails laid on the ground or elevated on the floor. Some gantry cranes use wheels, like tires, for movement, eliminating the need for rails.
While its appearance is reminiscent of a gate, hence the name “Gantry Crane,” it is also referred to as “bridge crane” or simply “gantry.” The term “gantry” refers to a structure with a horizontal beam supported by multiple legs.
The upper part of the gantry crane has a girder spanning both sides of the legs, and a trolley, called a “hoist,” is attached to the girder to lift and move loads. Various types of gantry cranes exist based on the structure of this trolley. Gantry cranes are widely used in machine workshops for transporting machinery and parts and have diverse applications, including container loading and unloading at docks.
Uses of Gantry Crane
The application of a gantry crane varies widely based on its lifting capacity and functionality, making it a versatile machine in terms of size and purpose.
While portable versions exist that can be moved or disassembled manually, larger ones are designed for handling loads such as large containers weighing several tons. Specialized gantry cranes designed exclusively for container handling are equipped with a container crane spreader that allows for attaching and detaching operations from the driver’s cabin.
Commonly seen gantry cranes in urban areas often use a hoist-style trolley for lifting and lowering loads, primarily employed in tasks like material handling in machinery and equipment.
Principle of Gantry Crane
As mentioned earlier, gantry cranes are highly versatile machines with a broad range of sizes and applications, including specialized structures for specific purposes. Here, we’ll focus on explaining the principle of a standard gantry crane.
1. Hoist
The primary component responsible for lifting and lowering loads, the hoist typically incorporates an electric winch for hoisting operations. In smaller types, manual chain blocks may be used instead of electric winches.
2. Girder
The structure supporting the hoist, also known as a girder or beam, consists of a main beam that directly supports the load and auxiliary beams that withstand horizontal forces. The basic girder cross-section includes horizontal members and diagonal and cross members.
3. Legs
Gantry crane legs are often constructed using box or pipe structures. One leg is designed to be a rigid structure, while the other is often made slender to avoid imposing excessive forces on the running rail due to girder deflection. This design ensures the crane withstands horizontal forces from load lifting, its self-weight, various movements, as well as forces from wind and seismic activity.
Types of Gantry Crane
While gantry cranes are commonly made of steel, smaller ones made of aluminum for easy portability also exist.
1. Standard Gantry Crane
Comprising basic components of a standard gantry crane, variations include hoist-type, club trolley-type, rope trolley-type, and man trolley-type, each determined by the type of trolley.
2. Specialized Gantry Crane
Specialized gantry cranes include structures like the jib crane on top of the gantry-shaped structure or the retractable crane with a retractable mechanism.
A lifting machine similar in shape to a gantry crane is the gantry lifter. While gantry cranes lift and lower loads using hoists, gantry lifters extend and retract their legs using hydraulic cylinders, achieving load lifting through this action.
How to Choose a Gantry Crane
When selecting a gantry crane, it is crucial to confirm that the lifting capacity matches the weight of the load. Additionally, consider specifications such as the distance between legs, girder height, and the type of wheels for movement, ensuring they meet the usage conditions.
For gantry cranes with a lifting capacity exceeding 5 tons, a “Crane and Derrick Operator” license is required to operate them. Therefore, it is essential to verify this qualification when choosing a machine.