What Is An Overhead Crane

What Is An Overhead Crane

Meta Description: Discover what an overhead crane is and its key types, components, benefits, and selection considerations. Learn how these cranes work and their applications in various industrial settings.

An overhead crane, also known as a bridge crane, is a vital heavy-duty lifting equipment commonly found in industrial facilities. This article provides an overview of overhead cranes, including their types, components, working principles, benefits, and considerations for choosing the right crane for specific industrial applications.

Key Takeaways:

• Overhead cranes are industrial lifting machines that transport heavy materials horizontally across facilities.
• They come in different types like bridge, gantry, jib, and workstation cranes suited for various applications.
• Understanding crane components like hoists, beams, and controls is essential for safe operation.
• Proper selection depends on factors like load capacity, span, and frequency of use.
• Overhead cranes are commonly used in manufacturing, construction, mining, and other industries for material handling needs.

What Is An Overhead Crane?

An overhead crane, also known as a bridge crane, is a heavy-duty type of crane found in many industrial facilities that requires the frequent lifting and movement of heavy materials.

Overhead cranes have various components that lift and transport loads horizontally across wide areas. Some key things to know about overhead cranes include:

Types of Overhead Cranes

Several common overhead cranes are suited to different lifting needs and industrial environments. The main types include:

• Bridge cranes – Feature two overhead beams and move loads across vast spaces. Varieties are single-girder and double-girder bridge cranes.
• Gantry cranes – Similar to bridge cranes, they run on legs along the floor instead of suspended runway beams. Common in shipyards and other outdoor applications.
• Monorail cranes – Utilize a single I-beam track for lifting loads in straight lines, like along assembly lines.
• Jib cranes – More compact wall or ceiling-mounted cranes that rotate but do not traverse long distances.
• Workstation cranes – Lighter duty cranes optimized for ergonomic lifting by workers within a small work area.

Critical factors like the load weight, type of material handled, required range of motion, and available floor/ceiling space determine the best crane type for each industrial setting and application.

How Overhead Cranes Work

Overhead cranes function by using various components working together to lift and transport loads across vast areas. The main components include the bridge beams, girders, hoists, trolleys, end trucks, and control panels.

Bridge cranes use overhead bridge beams supported by end trucks along fixed runway beams. The electric hoist and lifting trolley can then traverse the bridge beams horizontally. Gantry cranes lift loads but run on ground-level legs along an industrial floor space instead of suspended beams.

The hoist contains a lifting mechanism, such as a wire rope or chain hoist, which can utilize electric, pneumatic, or hydraulic power to raise or lower loads attached to the hoist hook or lifting device. The powered trolley moves the hoist laterally across the bridge.

Operators control the overhead crane from a ground-level or pendant control station to facilitate precise load lifting and transportation as needed.

Benefits of Using Overhead Cranes

There are several key benefits to utilizing overhead cranes in industrial and manufacturing facilities:

• Increased efficiency – Overhead cranes allow for faster loading and unloading of materials compared to manual labor or ground-level lifting equipment.
• Improved safety – Cranes remove risks to workers from lifting very heavy or hazardous loads. They provide fall protection and reduce ergonomic injuries.
• Higher load capacities – Overhead cranes can lift and move much heavier loads than forklifts or other ground-level load-lifting devices.
• Frees up floor space – Without cranes taking up overhead space, facilities have more room for inventory storage and material flow on the plant floor.
• Reduced costs – Overhead cranes boost productivity and reduce costs associated with manual labor and injuries over time.

Components of an Overhead Crane

Overhead cranes have various components that lift and transport loads horizontally across wide areas. Understanding each component is important for selecting the right crane system for your facility’s needs.

Bridge and Girders

The bridge beams provide the main horizontal structure of the crane. Bridge cranes commonly use single or double bridge beams, also known as girders, to bear the weight of loads. These load-bearing beams are made of rolled steel or fabricated box sections for strength.

• Single girder cranes utilize a single steel beam supported on each end by end trucks.
• Double girder cranes contain two parallel bridge beams to allow for increased load capacities and longer spans across large industrial spaces like steel mills and shipyards.

The bridge beams are supported at either end by end trucks. These wheeled trucks connect the beams perpendicularly and facilitate the movement of the entire crane bridge along fixed runway beams embedded in the building structure.

Single and double-girder cranes can be customized with various beam styles and materials based on the weight and size of the lifted loads.

Hoist and Trolley

The electric hoist and lifting trolley lift and transport loads horizontally. Hoists may use wire rope or chain mechanisms to raise loads. A powered trolley traverses the bridge beams using an integrated lifting mechanism like a motor, reducer, and wheels. This allows operators to position loads precisely using pendants or remote controls.

End Trucks

End trucks connect the bridge and runway beams, facilitating the crane’s movement. These wheeled trucks support either end of the single or double bridge beams.

Most end trucks contain multiple wheels, often four or eight, depending on the weight capacity of the crane. The wheels ride along the top surface of embedded crane runway beams. Both powered and non-powered end truck designs are available, with powered options allowing additional crane functionality.

Controls

Overhead cranes require a control system to direct crane functions from a safe position. Control panels are usually mounted in a ground-level control box or on a wireless pendant that operators can move with them.

Controls regulate functions like powering electric overhead traveling bridge movements, lifting and lowering loads using wire rope or chain hoists, and powering any top running trolley hoists needed to move the lifting device horizontally along bridge beams. This allows for precise load positioning and transport.

Bridge Cranes

Bridge cranes are among the most common overhead cranes used across various industries. These cranes consist of bridge beams that traverse overhead runway beams.

Single Girder Bridge Cranes

Single girder bridge cranes contain a single load-bearing bridge beam or girder attached at either end by end trucks. This allows the crane to move loads horizontally across wide areas below. They utilize a single i-beam constructed of rolled steel.

A hoist and under-running trolley then operate along the bottom flange of the girder to lift and transport materials. These cranes offer simpler designs and are often more economical for lighter-duty applications than double-girder cranes.

Double Girder Bridge Cranes

Double girder bridge cranes feature two parallel bridge beams to handle heavier lifting capacities and longer spans. Their two bridge girders are supported by end trucks at both ends and connected by lateral bracing for additional stability.

A hoist and top-running trolley operate along rails installed above the bridge beams. This crane type excels in applications like steel mills requiring frequent lifts of bulkier or heavier loads over broad industrial floor spaces.

Gantry Cranes

Gantry cranes are another important overhead crane used across various industrial sectors. These cranes have both similarities to and key differences from bridge cranes.

Design and Features

Unlike bridge cranes suspended above a work area on overhead runway beams, gantry cranes run on heavy industrial floor-level tracks or rails instead of an overhead system. This allows them to traverse open areas like shipyards or extensive manufacturing facilities.

Gantry cranes consist of a bridge structure mounted on a rail-guided movable platform supported by two or more legs. The bridge beams hold the trolley and hoist, while the legs allow the entire crane to move laterally on an embedded track system. Gantry cranes also commonly use wire rope hoists to lift heavy loads.

Applications

Given their ability to move loads at ground level, gantry cranes excel in environments like ports and shipbuilding yards where overhead infrastructure may not be possible. They are well-suited for tasks like loading and unloading cargo from ships and transporting bulky components throughout large industrial spaces.

Gantry cranes are also frequently used in steel mills, power plants, construction sites, and other outdoor applications requiring horizontal and lateral load movement without barriers above. Their design provides flexible material handling in wide-open and difficult-to-enclose industrial areas.

Monorail Cranes

Monorail cranes provide overhead lifting capabilities focused along a single plane of motion. Their design addresses some specific material handling needs.

Design and Mechanism

Unlike bridge cranes that span a work area using two end trucks and a bridge beam, monorail cranes consist of an overhead I-beam track mounted to the building structure or crane runway beams. This single-beam configuration lets them lift and transport loads linearly along an assembly line or process flow.

A trolley rides along the track system utilizing wheels. It supports the hoist, usually a wire rope or cable reel type, for vertically lifting loads. An electric chain hoist then helps maneuver the load horizontally as needed.

Uses in Industries

Monorail cranes excel in applications requiring straight-line material movement, such as assembly or production lines where loads must stop at designated workstations.

They see frequent use in manufacturing plants and factories where parts are added sequentially as they move down the line. Common uses include loading docks, shipping and receiving, and stock movement between warehouse aisles or storage racks in limited overhead spaces.

Jib Cranes

Jib cranes provide overhead lifting capabilities for smaller work areas and more precise load positioning than other crane types.

Types of Jib Cranes

Jib cranes are available in various styles to suit different lifting needs. Wall jib cranes feature a fixed jib arm attached to a wall or column for loads in a defined zone. Full-revolving jib cranes have a rotating jib that pivots around its base, allowing a full 360-degree range of motion.

Compact floor jib cranes are mounted to the floor on a rotating pedestal. Each jib crane type uses an electric chain or wire rope hoist to lift and lower materials along the jib arm.

Common Applications

Given their compact footprints, jib cranes excel in confined work areas with overhead lifting needs. They see widespread use in manufacturing applications requiring precise load positioning, such as assembly, quality control stations, and finishing processes.

Other common uses include loading docks, fabrication shops, and maintenance work, where loads must be lifted into equipment or structures. Jib cranes provide flexible overhead lifting solutions in space-restricted industrial environments.

Workstation Cranes

Workstation cranes are a specialized type of overhead crane designed to improve ergonomics in manufacturing environments.

Design for Ergonomics

Unlike other crane types, workstation cranes focus on lifting loads into and out of individual workstations where assembly or production tasks are performed. Their design prioritizes operator comfort and safety.

To reduce reaching and lifting stresses, workstation cranes often feature adjustable lifting heights, articulating arms, and compact footprints tailored for unobstructed movement around work cells. Many incorporate electric chain hoists or lightweight lifting mechanisms like cable reels that are easier for workers to operate.

Uses in Work Cells

By integrating lifting capabilities directly into workstations, these cranes help transfer loads efficiently while minimizing ergonomic risks to employees. Typical applications include automotive production, electronics assembly, machine tending, and other precision tasks requiring overhead access.

Workstation cranes free up floor space and improve workflow compared to stationary lifting tables. They provide flexible, operator-centered material handling in detailed manufacturing environments.

Selecting the Right Overhead Crane

Choosing the ideal overhead crane for your facility requires evaluating key application factors. Let’s examine the primary considerations for ensuring the best material handling solution.

Factors to Consider

1. Lifting capacity – Consider maximum load weights and potential future increases.
2. Lifting height – Sufficient height is needed to clear tall loads and machinery.
3. Span/clearance – Bridge, gantry, and monorail cranes need adequate overhead or floor space.
4. Duty cycle – Frequent or infrequent lifts impact motor sizing and crane design.
5. Environmental conditions – Outdoor use may require weatherproofing and corrosion protection.
6. Budget – Consider equipment, installation, power connection, and long-term maintenance costs.

Evaluating Your Needs

Thoroughly assess your specific lifting, maneuvering, and throughput needs to determine the ideal crane type, configuration, and optional features. Consultation with experienced crane suppliers addresses all-important application factors and industry standards.

Requesting demonstrations and references further aids evaluation. Proper evaluation leads to a solution that maximizes your operation’s safety, productivity, and ROI.