Cranes are machines used for lifting and moving heavy loads in literally all kinds of heavy industries and construction sites. The most common variants include overhead cranes, also called bridge cranes, or overhead travelling cranes, which are indispensable in factories, warehouses, distribution centres, and generally in any type of industrial environment.
These cranes are designed to provide complex lifting operations in confined spaces and combine flexibility, effectiveness, and safety. In this blog, we will look into what an overhead crane is, its various components, how it works, the different types of overhead cranes, and the industries that apply them. We will also look at some advantages of using overhead crane systems, and insight into their installation and maintenance.
What Is an Overhead Crane?
An overhead crane, also popularly known by its other two names; ceiling crane or crane overhead, is a special type of crane system designed for lifting and moving heavy components horizontally across a work area as needed.
Unlike mobile cranes, which operate on wheels or tracks, most overhead cranes are installed on fixed tracks or beams running along the ceiling of a building or workshop. This design allows the crane to move large loads without large ground footprints and, therefore, is designed for use in tight or limited spaces.
An overhead crane typically includes a bridge, a hoist, and a trolley mechanism that works together to move and lift materials in a controlled and efficient manner. Such cranes are highly demanded in industries related to automobile manufacturing, aerospace, heavy construction, steel mills, foundries, and other high-challenging operational sectors requiring strong, precise, and adaptable lifting capabilities.
How Does an Overhead Crane Work? The Overhead Crane Working Principle
The principle behind the working scheme for an overhead crane system is basically a load moving horizontally through a workspace and being moved vertically by lifting and lowering. Following is a breakdown of how these cranes work:
- Bridge: The main structure of the crane; essentially spans over the length of the workplace. The bridge travels on rails attached to the structure of the building.
- Hoist: This is the lifting equipment usually fitted with a motor that lifts or lowers the load. It is attached to the trolley.
- Trolley: A motor-driven or manually operated unit that travels the hoist across the bridge, thus providing motion of the load in a horizontal direction across the area.
- Control System: Most overhead cranes are controlled by a pendant – a control station with buttons – operated from the floor by a wireless remote or a fixed control room. An operator directs the movement of the bridge, the hoist, and the trolley to position the load as desired.
- Rail: In most instances, when referring to a runway rail, it is a fixed track that the crane travels on, either mounted to the floor – such as in the case of a gantry crane – or overhead, as in a bridge crane. It is a moving bridge that enables the crane to move around its workplace and by a hoist mechanism that allows moving the load up or down safely.
Depending on how a crane is designed, it can be controlled by manual mode, semi-automatic, or fully automated systems where the task is either complex or repetitive.
What Are the Components of an Overhead Crane?
The components of an overhead crane can be designed as mechanical, electrical, and safety elements in their performance. Let’s have a look at the overhead crane components and functions:
Bridge Structure
- Girder: It is the large horizontal beam that forms the main load-bearing structure of the bridge. The girder supports both the hoist and the trolley.
- End Trucks: Wheeled units at either end of the crane, allowing the bridge to traverse the runway rails, ensuring smooth movement across the entire workspace.
Trolley and Hoist Mechanism
- Hoist: The lifting unit that raises and lowers the load. Electric Motors generally power the hoists and include gearboxes to transmit power to the lifting mechanism.
- Trolley: The platform that carries the hoist along the length of the bridge, facilitating horizontal load movement.
Runway System
- Runway Rails: The fixed rails or beams that support the crane’s end trucks and allow horizontal travel. These rails are typically mounted on the building ceiling or structure.
Control Systems
- Pendant Controls: A hard-wired control system with push button operation of the crane’s movements.
- Wireless Remote: This is one of the more modern control systems, whereby operators can work the crane from some distance.
- Operator Station: A stationary control room or cabin, in larger industrial settings, is used to oversee real-time operation of the crane.
Motors and Gearboxes
- Motors: These are usually electric motors that drive the movement of the bridge, hoist, and trolley for the smooth operation of the crane system.
- Gearboxes: Gearboxes transfer power from the motors into the moving parts. They alter speeds and torque to suit the operation requirements.
Safety Features
- Overload Protection Devices: These devices prevent the crane from lifting loads that exceed its rated capacity, a factor that causes structural failure.
- Limit Switches: Limit switches keep the crane from moving beyond the stipulated operational limits, enabling the entire system to stay within its limits.
- Emergency Stop Buttons: These are located at strategic positions on the crane and provide a means for the operators to stop all crane operations instantly in case of an emergency.
Types of Overhead Cranes
Overhead cranes are available in various configurations to suit specific applications, load capacities, and spatial constraints. Some of the most common types of overhead cranes include:
- Bridge Cranes (Overhead Cranes): Probably the most common type, these cranes are used for more general-purpose lifting in factories, warehouses, and distribution centres.
- Gantry Cranes: Essentially the same as bridge cranes but are mounted on legs and run on tracks inside or outside the building.
- Jib Cranes: The jib cranes are designed to execute minor tasks in cramped areas such as workshops or along an assembly line.
- Workstation Cranes: Lightweight, modular cranes used in ergonomic material handling applications.
- Single Girder Cranes: These cranes have only one girder upon which the hoist will travel with its trolley.
- Double Girder Cranes: Having two girders means more strength and lifting capacity.
- Semi-Gantry Cranes: A hybrid design, whereby one side runs on tracks compatible with a gantry style, while the other runs along an overhead runway.
- Portal Cranes: Basically, a rigid gantry crane that serves loads outdoors on heavy or oversized lots.
- Underhung Cranes: These are directly mounted onto the ceiling with a particular design for light-duty applications.
- Top Running Cranes: The cranes moving along the top of the runway beams maintain greater clearance and higher lifting capacity, hence being suitable for heavy-duty industries such as steel mills.
What Are the Advantages of Overhead Cranes?
Overhead cranes provide several advantages in industrial settings, including:
- Increased Efficiency: Overhead cranes save time by easily lifting and moving heavy loads, reducing manual labour.
- Space Efficiency: Since they are mounted overhead, these cranes can save floor space, particularly in crowded warehouses or factories.
- Improved Safety: Most accidents can be avoided by installing limit switches, emergency stops, and overload protection on an overhead crane system.
- Flexibility: Overhead cranes can be customised for specific lifting needs, allowing them to be adapted to different industries and tasks.
Overhead Crane Installation & Maintenance with Ocean
Overhead cranes are essential to modern industrial operations, providing unmatched versatility, safety, and efficiency in material handling across diverse sectors, including manufacturing, construction, and warehousing. These cranes can handle a wide range of tasks, from lifting lighter loads to managing heavy materials, making their proper selection crucial for optimising performance and safety.
However, the effective operation of overhead cranes depends not only on choosing the correct crane and installing it properly but also on regular maintenance and inspections. Proper installation, performed by experienced professionals, ensures the crane meets safety standards, functions efficiently, and aligns with operational needs. Ongoing maintenance and inspections are equally important, helping to identify potential issues before they lead to costly breakdowns and extending the crane’s lifespan.
At Ocean, a leading engineering company in Oman, we offer high-quality services, including expert crane installation, routine inspections, preventative maintenance, and timely repairs. To learn more about our crane services or schedule a consultation, visit our website or contact our team today.