• Oct 15, 2024
• News

Overhead Crane Parts and Functions

An overhead crane system consists of several core components, including the structural framework, and mechanical parts.

Overhead cranes are important lifting equipment in various industries, designed to lift and move heavy loads efficiently across a workspace. Their applications span across manufacturing, warehousing, construction, and transportation, making them an indispensable tool for industries that require precise material handling. Understanding the key components of an overhead crane is essential for ensuring proper operation, maintenance, and safety. In this article, we will take a detailed look at the various components that make up an overhead crane, providing a clear understanding of their functions and how they work together to facilitate smooth crane operations.

1. Bridge

The bridge is one of the primary structural components of an overhead crane. It is the large horizontal beam that spans the width of the workspace and supports the hoist and trolley. Depending on the type of crane, the bridge can either be a single girder or a double girder.

Single Girder Bridge

In a single girder crane, the bridge consists of a single horizontal beam. These types of bridges are typically used for lighter loads and shorter spans. Single girder cranes are cost-effective and simpler in design, making them suitable for many industrial applications where space or load limits are not too high.

Double Girder Bridge

For heavier loads and larger spans, double girder cranes are used. In this design, two parallel beams make up the bridge, providing additional strength and stability. Double girder bridges allow for greater lifting capacities and more complex configurations, such as the inclusion of a walkway or additional lifting mechanisms.

Both types of bridges move along the length of the runway, which is installed along the sides of the workspace, providing the crane with horizontal movement.

2. Runway and Rails

The runway is a track system that runs along the length of the facility, supporting the movement of the crane bridge. These runways are typically mounted to the building’s structure or are freestanding on columns. The rails on the runway allow the bridge to move back and forth, covering the entire workspace and enabling the crane to handle material throughout its range.

Runway systems are critical to the crane's performance, as they define the operational reach of the crane. Proper alignment and maintenance of the runway and rails are essential for smooth and safe crane operations.

3. Hoist

The hoist is one of the most critical components of an overhead crane, responsible for lifting and lowering loads. It is mounted on the trolley and moves horizontally along the bridge. Hoists can be classified into three main types depending on their construction and application: Wire Rope Electric Hoists, Chain Hoists, and Manual Hoists.

a. Wire Rope Electric Hoist

A Wire Rope Electric Hoist is a versatile and robust lifting device commonly used for handling heavier loads in industrial settings. It consists of a drum that winds a steel wire rope, which is capable of withstanding significant tension and pressure. This type of hoist is suitable for applications requiring higher lifting capacities, typically ranging from 1 ton to over 100 tons.

• High load capacity
• Greater lifting speed
• Suitable for long lifts and large spans
• Typical Applications: Wire rope electric hoists are commonly used in heavy-duty industries such as steel mills, shipyards, and manufacturing plants where frequent lifting of heavy loads is required.
• Wire rope hoists offer a high degree of reliability and are often used in environments that demand precise control over large and heavy materials.

b. Chain Hoist

A Chain Hoist uses a chain instead of a wire rope to lift loads. Chain hoists are typically available as both electric chain hoists and manual chain hoists. The chain is looped around a sprocket and wound around a gear mechanism to lift the load when operated. Chain hoists are known for their durability and are often used in lighter-duty applications or in areas where smaller loads need to be lifted frequently.

• Lower cost compared to wire rope hoists
• Compact design and ease of installation
• More portable and requires less maintenance
• Typical Applications: Chain hoists are widely used in smaller workshops, warehouses, and maintenance areas where lifting capacities usually range from a few hundred kilograms to several tons.
• Electric chain hoists offer the convenience of motorized lifting, while manual chain hoists are operated by pulling the hand chain, offering flexibility in locations without electric power.

c. Manual Hoist

A Manual Hoist, also known as a hand-operated hoist, relies on human power to lift loads using a simple pulley system. Unlike electric hoists, manual hoists do not require electricity, making them suitable for environments where electrical power is unavailable or undesirable.

• Inexpensive and highly portable
• Ideal for low-volume lifting or areas without electricity
• Simple to operate and maintain
• Typical Applications: Manual hoists are best suited for small-scale lifting tasks, maintenance work, and infrequent use in settings such as garages, workshops, or smaller construction projects.

4. Trolley

The trolley is the component that moves horizontally along the bridge, carrying the hoist and allowing it to position loads across the width of the crane’s span. Depending on the crane design, trolleys can either be top-running or under-running:

Top-Running Trolley

In this configuration, the trolley runs along the top of the bridge girders. Top-running trolleys are commonly found in double girder cranes, allowing for increased load capacity and greater stability.

Under-Running Trolley

In under-running cranes, the trolley is suspended from the bottom flange of the bridge. This setup is typically found in single girder cranes and is suited for lighter loads.

The smooth operation of the trolley is critical for the precise positioning of loads. Therefore, it requires regular maintenance to ensure that it can move freely and without obstruction.

5. End Trucks

End trucks are the components located at each end of the bridge that allow it to travel along the runway rails. They are equipped with wheels or rollers that move the entire bridge structure along the length of the crane system. End trucks are vital to the horizontal movement of the crane and are usually fitted with motorized drive systems to control the bridge’s motion.

The quality and condition of the end trucks play a large role in the overall performance of the crane. Worn-out wheels, improper alignment, or damaged components can lead to uneven movement and reduce the crane's efficiency.

6. Controls

Overhead cranes are operated using control systems, which allow the operator to direct the movement of the crane, hoist, and trolley. Crane controls come in various forms, including:

Pendant Control

A handheld device attached to the crane by a cable, allowing the operator to manually control the movements of the crane.

Radio Remote Control

Wireless control systems are increasingly common in modern cranes, enabling the operator to control the crane from a safe distance. This improves both safety and convenience, as the operator can stand in a position with a clear view of the load.

Cab Control

In some larger crane systems, a cab is installed on the bridge or trolley, allowing the operator to sit in an enclosed space and control the crane from within.

Modern control systems also incorporate variable frequency drives (VFDs), which enable precise control over the crane's speed, ensuring smooth acceleration and deceleration.

7. Electrical System

The electrical system of an overhead crane provides the power required to operate the motors, hoists, and controls. It consists of power supply lines, conductors, and control panels that distribute electricity throughout the crane components.

8. Brakes

Brakes are critical safety components of an overhead crane, ensuring that the crane can come to a controlled stop when necessary. They are typically installed on the hoist, trolley, and bridge motors, and serve two primary purposes:

Holding Brakes

These are designed to hold the crane or hoist in position once the motion has stopped, preventing unintentional movement.

Dynamic Brakes

Dynamic brakes are used during the deceleration phase to control the speed at which the crane or trolley slows down, preventing abrupt stops and potential load swinging. This is also often used by Yuantai.

The braking system plays a crucial role in both safety and precise load handling, particularly in environments where accuracy and control are important.

9. Bumpers and Safety Features

Safety is paramount in crane operations, and several features are built into the system to minimize the risk of accidents or equipment failure. Bumpers are installed on the end trucks and trolleys to absorb impact energy in case the crane or trolley reaches the end of the runway. These safety devices protect both the crane and the facility from damage.

Additional safety features include overload sensors, which prevent the crane from lifting loads beyond its rated capacity, and limit switches, which stop the crane’s movement when it reaches predefined endpoints.

Conclusion

Overhead cranes are complex machines made up of multiple components, each playing a critical role in the crane's ability to lift, transport, and position heavy loads with precision. From the bridge and hoist to the controls and electrical system, every part must function correctly for the crane to operate safely and efficiently. Proper understanding of these components, along with regular inspection and maintenance, is essential to ensuring that the crane remains in optimal working condition.