Overhead Crane Specifications

Lifting capacity, often referred to as the rated load capacity, is one of the most crucial specifications of an overhead crane. It indicates the maximum weight that the crane is designed to lift. This capacity is measured in tons (t) and can vary widely depending on the crane’s design and intended application.

For example, the lifting capacity of overhead bridge cranes can range from smaller cranes with a 5t capacity to much larger models capable of lifting up to 450t. Some cranes are designed with dual hooks, with the main hook having a higher lifting capacity than the auxiliary hook. For instance, a 15t/3t overhead crane means the primary hook can lift 15 tons, while the auxiliary hook is rated for 3 tons.

The overhead crane capacity needed for a specific application depends on the weight of the loads being lifted, which is critical in choosing the right crane for your business or facility.

The span of an overhead bridge crane is the distance between the rails on which the crane runs, measured horizontally. It defines how wide the crane can cover and is critical for determining whether the crane can operate across the entire area where lifting operations will occur.

Overhead cranes typically have spans that range from 10.5m to 31.5m, and customized to customer’s requirements.

The span chosen depends on the layout of the workspace and the distance the crane needs to cover. A larger span is required for bigger or more spacious work areas.

Lifting height refers to the vertical distance between the highest and lowest points a crane’s hook or lifting device can reach. This specification determines how high a crane can lift its load, which is essential for applications involving multi-story facilities or areas with obstacles.

Common lifting heights for overhead cranes range from 6m to 30m, and can also be customized according to your specific requirements. The height is often provided in two values: the primary hook lifting height and the auxiliary hook lifting height. For example, a crane with a lifting height of 12m/14m means the main hook can lift to a height of 12m, and the auxiliary hook reaches up to 14m.

Choosing the right lifting height depends on the height of structures or equipment that need to be lifted, as well as the required clearance for operation.

The speed of a bridge crane is another critical specification, as it determines how quickly the crane can lift and move loads. Speed specifications typically include:

• Hoist Speed: The speed at which the crane’s hoist moves vertically to lift or lower the load.
• Travel Speed: The speed at which the crane moves horizontally along the runway.
• Trolley Speed: The speed at which the hoist trolley moves along the bridge or girder.

Each of these speeds is essential to optimizing crane operations, ensuring efficiency and safety. For instance, higher speeds may be necessary in high-output environments but should be balanced against the risk of load instability.

The duty cycle or service class refers to the amount of use a crane will experience over a certain period. It essentially represents how intensively the crane will be used, and it can range from light-duty (occasional use) to heavy-duty (continuous or high-frequency use).

• Light Duty: Cranes used in lighter, less frequent operations, such as maintenance or installation in power plants or hydropower stations. These light duty overhead cranes operate under light loads and are not subjected to heavy continuous use.
• Medium Duty: These cranes handle moderate loads and are used in general workshops, assembly lines, and production facilities. They work at a medium speed and can handle frequent lifting tasks without continuous heavy-duty usage.
• Heavy Duty: Cranes that are used for heavy load lifting in industries such as metallurgy or foundries, where they regularly handle large and heavy materials. These heavy duty overhead cranes are built to withstand tougher conditions and operate under frequent heavy loads.
• Extra Heavy Duty: These cranes are designed to operate continuously at or near their maximum rated load. They are often used in environments where heavy loads are the norm, such as in steel production or large-scale manufacturing.

• Identify the Maximum Load: Assess the typical and heaviest loads that will be lifted. It’s essential to factor in the weight of materials, equipment, or goods, as well as any additional components like slings, grabs, electromagnetic chucks, or spreader beams.
• Add Safety Margin: It’s always wise to add a safety margin when selecting the crane’s load capacity. A general rule of thumb is to choose a crane that offers at least 25% more load capacity than your heaviest expected load. This helps prevent overload situations and extends the crane’s lifespan.
• Consider Future Growth: Consider potential increases in workload over time. Opting for a custom overhead crane with a slightly higher load capacity than needed can accommodate any future changes in your operations without requiring an upgrade.

• Measure Your Facility: Start by measuring the distance between support columns or walls where the crane will be installed. This will give you a clear idea of the span needed to cover the workspace.
• Consider Future Layouts: If you plan to expand your facility or alter the layout, ensure the span allows for flexible coverage of the area.

• Define Clearance Requirements: Determine the height of the items being lifted and the clearance required for storage or transport. It’s vital to choose a crane that can reach these heights comfortably.
• Account for Overhead Structures: Consider any existing overhead structures or obstructions in the facility, such as beams, ductwork, or other equipment. The crane’s lifting height must be able to clear these obstacles while operating.

• Select Load Handling Speed: Different tasks require different lifting speeds. For precise material handling, a slower speed might be necessary, while for quick loading and unloading, faster speeds are more effective.
• Determine Control Modes: Cranes typically offer different speeds for hoisting, traveling, and trolley movement. Depending on the application, you may need different control modes (e.g., variable speed controls or two-speed systems) for smoother, more efficient operations.

• Consider Frequency of Use: How often will the crane be in operation? Cranes that operate continuously or for long hours will require a higher-duty cycle (i.e., more robust components), while cranes used occasionally may need less.
• Evaluate Work Intensity: The duty cycle also takes into account how heavy the loads are and how much time the crane spends lifting them. Cranes used for light-duty tasks may only need an A3 or A4 rating, while cranes in heavy-duty environments will require an A5, A6, or higher rating.
• Factor in Environmental Conditions: If the crane is operating in extreme environments (e.g., high-temperature or corrosive conditions), it may require a more durable and reliable duty cycle rating to handle the stress.