What is the working class of a bridge crane? How are working classes A1-A7 categorized?

The working class of a bridge crane indicates the intensity of its operational workload, specifically reflecting the time-based workload and load capacity of the crane. Hook-type cranes are classified into three levels and seven categories: A1-A3 (light duty); A4-A5 (medium duty); A6-A7 (heavy duty). The magnitude of a bridge crane's duty class is determined by two capabilities: the frequency of crane usage, termed the utilization rate; and the magnitude of loads borne, termed the load condition. During its effective service life, a bridge crane undergoes a specific total number of duty cycles. A duty cycle encompasses the entire operational process from preparing to lift a load until the next lifting operation commences. The total number of work cycles indicates the crane's utilization rate and serves as a fundamental parameter for classification. This total represents the sum of all work cycles performed during the specified service life. Determining an appropriate service life requires consideration of economic, technical, and environmental factors, while also accounting for the effects of equipment aging.

Overall Work Class of Bridge Cranes: Light Duty (A1-A3): Rarely lifts rated loads, typically handles light loads. Primarily used for equipment installation and maintenance in power plants or other workplaces, or in workshops and warehouses with infrequent operation. Medium Duty (A4-A5): Occasionally lifts rated loads, typically handles medium loads. Used in heavily utilized workshops and garages, such as general machining and assembly shops. Heavy Duty (A6-A7): Frequently lifts rated loads, typically handles heavy loads. Used in intensively operated workshops and warehouses, such as those requiring prolonged, frequent handling of heavy items or metallurgical plants.

It should be noted that the working class of a bridge crane and its lifting capacity are two distinct concepts. Lifting capacity refers to the mass of material lifted in a single operation, while working class represents the crane's comprehensive performance characteristics. A higher lifting capacity does not necessarily imply a higher duty cycle; conversely, a lower lifting capacity does not necessarily mean a lower duty cycle. For cranes of the same type and lifting capacity, different duty cycles result in varying safety factors for components. Focusing solely on lifting capacity while ignoring the duty cycle—such as frequently operating a crane with a low duty cycle at full load—accelerates wear and tear on vulnerable parts, increases failure rates, and may even lead to accidents.

Additionally, it should be noted that the working level of the bridge structure and metal framework differs from the working level of the hoisting mechanisms. For a single crane, due to inconsistent loading and uneven operational cycles across different working mechanisms, the working levels of individual mechanisms often diverge from the overall bridge crane working level. This discrepancy requires particular attention during component retirement and replacement for different mechanisms.

Today, the duty cycle has become a critical parameter for bridge cranes. When ordering overhead cranes, it is essential to consider not only whether the tonnage meets requirements but also the actual usage conditions of the bridge crane to ensure the purchase of suitable equipment.

As a globally leading crane supplier, Henan Mine Crane offers a comprehensive product range from 5 tons to 500 tons. We provide customized designs based on client site drawings, load characteristics, and environmental parameters. Our full lifecycle services deliver one-stop solutions including site surveys, design planning, installation and commissioning, as well as regular maintenance.