What is a Double Girder Overhead Crane Specification?

A double girder overhead crane is one of the most versatile and commonly used types of cranes in industrial settings. It consists of two main beams, called girders, that run parallel across a building or facility. These cranes are designed for heavy-duty lifting operations, allowing them to handle significant loads with high efficiency and safety. Understanding the specifications of a double girder overhead crane is essential for businesses that plan to use this equipment to optimize their operations. In this article, we will delve deep into the various specifications of double girder overhead cranes, including their components, load capacity, span, lifting height, duty classification, and other factors that influence their performance.

Key Components of a Double Girder Overhead Crane

The basic structure of a double girder overhead crane consists of several key components that work together to lift and transport heavy materials safely. These components are crucial in determining the double girder overhead crane specifications:

1. Girders: The two parallel girders are the backbone of the crane, providing support for the bridge and lifting mechanism. These girders are typically made from high-strength steel to ensure stability and durability under heavy loads.

2. Bridge: The bridge connects the two girders and is the part of the crane that moves along the runway tracks. It serves as the framework for the trolley and hoist mechanism, providing the necessary clearance for lifting loads.

3. Trolley and Hoist: The trolley is a carriage that moves along the length of the girder, carrying the hoist with it. The hoist is responsible for lifting the load and is usually equipped with a motorized winch, a drum, and ropes or chains to lift materials to the desired height.

4. End Trucks: The end trucks are mounted on the ends of the bridge and support the crane’s movement along the runway. These trucks are equipped with wheels that run on the rails, allowing the crane to traverse the building.

5. Control System: Double girder overhead cranes are typically equipped with a sophisticated control system, which can include manual controls, radio remote controls, or pendant controls. These systems allow operators to maneuver the crane with precision and ease.

Crane Specifications

When selecting or designing a double girder overhead crane, several specifications must be considered to ensure the crane meets the operational needs of the facility. Here are the most important specifications for these cranes:

1. Load Capacity

The load capacity of a double girder overhead crane is one of the most critical specifications. It defines the maximum weight the crane is designed to lift. Load capacity can range from a few tons to several hundred tons, depending on the application. Cranes designed for heavy-duty tasks, such as in shipyards, steel mills, or power plants, typically have higher load capacities (up to 500 ton gantry crane or more).

The load capacity should be chosen based on the specific requirements of the facility. Overloading the crane can result in equipment failure, accidents, and downtime. To ensure safety, it is essential to select a crane with a load capacity that exceeds the maximum weight of the materials being lifted.

2. Span

The span of a double girder overhead crane refers to the horizontal distance between the two girders. This measurement is important because it determines the coverage area of the crane. The span varies based on the building's layout and the range of the crane's lifting capability. Typical spans range from 5 meters to over 30 meters, depending on the size of the facility.

Choosing the right span is crucial to maximizing the crane’s reach and ensuring it can cover the entire workspace. A larger span allows the crane to lift materials from a broader area, improving productivity and efficiency.

3. Lifting Height

Lifting height, also known as lifting height or hook height, refers to the vertical distance the crane can lift a load from the ground to the highest point it can reach. Lifting height is typically measured from the surface of the crane’s runway to the underside of the hoist hook.

For double girder overhead cranes, lifting heights generally range from 6 meters to 30 meters, depending on the specific needs of the facility. A greater lifting height is essential for industries like construction, manufacturing, or mining, where large or heavy materials need to be lifted to considerable heights.

4. Duty Classification

Overhead cranes are classified into different duty classes, which indicate the frequency and intensity of use. The duty class is essential for determining the crane’s design and durability. The most common duty classifications for double girder overhead cranes are:

• A1 (Light Duty): The crane operates occasionally with light loads and low usage frequency.
• A3 (Medium Duty): The crane handles moderate loads and operates regularly, but not continuously.
• A5 (Heavy Duty): The crane is used for heavy lifting and operates at high frequencies with a greater load demand.
• A7 (Severe Duty): The crane operates in the most demanding environments with extremely heavy loads and continuous operation.

The duty class will affect the choice of motor size, gearbox type, and the overall design of the crane, ensuring it is capable of handling the required workload.

5. Control Mode

Modern double girder overhead cranes are equipped with various control options to enhance operational efficiency. Common control modes include:

• Ground Control: Operators control the crane from a position on the ground, usually with a pendant or push-button system. This mode is often used in less complex operations.
• Radio Remote Control: This allows operators to control the crane from a distance, providing greater flexibility and safety in hazardous environments.
• Cabin Control: The operator sits inside a cabin attached to the crane, offering complete control over the crane’s movement.

The choice of control mode depends on the complexity of the lifting operations and the level of precision required.

6. Hoist Mechanism

The hoist is a critical component that determines the hoist overhead crane lifting speed and power. The hoist mechanism is typically powered by an electric motor, but it can also be driven hydraulically, depending on the application. The speed of the hoist can vary, and cranes can be equipped with variable speed drives to provide greater control over the lifting process.

Hoists also come in different configurations, such as electric chain hoists or wire rope hoists, each suitable for specific applications based on the load size, lifting speed, and operational environment.

7. Safety Features

Safety is a top priority when designing and operating double girder overhead cranes. Several safety features can be integrated into these cranes to reduce risks and enhance operational reliability:

• Overload Protection: This feature prevents the crane from lifting loads beyond its rated capacity.
• Limit Switches: Limit switches ensure the crane moves within its designated operational range, preventing damage to the crane or surrounding equipment.
• Anti-Sway Systems: Anti-sway technology helps to reduce the swinging of loads, especially when lifting large or bulky items.
• Emergency Stop: A built-in emergency stop button allows operators to halt the crane immediately in case of an unexpected event.

Conclusion

Double girder overhead cranes are indispensable in industries that require heavy-duty lifting capabilities. Their specifications—ranging from load capacity, span, and lifting height to duty classification and safety features—determine the crane’s effectiveness in meeting operational needs. When selecting or designing a double girder overhead crane, it is crucial to consider the specific requirements of the facility and the materials being handled to ensure maximum safety, efficiency, and durability.

Whether used in manufacturing plants, steel mills, or construction sites, double girder overhead cranes provide businesses with the ability to lift and transport heavy loads with ease, ensuring smooth operations and high productivity. By understanding these essential specifications, companies can make informed decisions when investing in overhead crane systems that best suit their needs.