Purchasing
overhead cranes is a significant investment for the company. Numerous factors need to be considered during the procurement process, such as workshop specifications, lifting capacity, span, and working environment. Another crucial factor is the working class of the bridge crane. The working class (A1–A8) is a comprehensive indicator measuring
overhead crane usage intensity and load condition, and it has a critical impact on procurement decisions.
overhead crane Working Class Classification
According to ISO 4301 and GB/T 3811 standards, bridge cranes are classified into 8 working classes (A1 to A8) based on usage frequency and load conditions, as follows:
1. Classification Standards
A1-A3 (Light): Such as maintenance workshops and installation sites, with an average annual working hour ≤ 200 and a load rate ≤ 25%.
A4-A5 (Medium): Such as machining workshops, with an average annual working hour 200-600 and a load rate 25%-50%.
A6-A7 (Heavy): Such as
metallurgical plants and ports, with an average annual working hour 600-2000 and a load rate 50%-75%.
A8 (Extra Heavy): Such as continuously operating steel mills, with an average annual working hour > 2000 and a load rate > 75%.
2. Grading Criteria
Load Spectrum Coefficient (Kp): Reflects the frequency of load changes, calculated as (K_p = \sum (P_i/P_{max})^3 \times t_i/T ).
Total Working Cycles (C): Grade A1 requires ≥16,000 cycles, Grade A8 requires ≥2,000,000 cycles (Data source: Appendix B of GB/T 3811-2008).
Electromagnetic bridge crane weihua
Based on overhead crane Working Class recommendations for crane procurement
1. Choosing the Appropriate Working Class to Match the Bridge Crane's Working Scenario
Light Industry/Warehousing: Prioritize A3-A4 class bridge cranes, balancing economy and reliability.
Heavy Industry/High-Frequency Operations: Such as metallurgical bridge cranes, steel plant cranes, etc, A6-A8 class is mandatory; otherwise, overload can easily lead to structural fatigue and safety issues.
Important Note: Working class is not directly related to lifting capacity. For example, a 500-ton crane with low usage frequency can be selected as A3 class; while a 5-ton warehouse equipment requiring frequent lifting should be selected as A7 class.
2. Bridge Crane Procurement Recommendations
Define Working Conditions: Assess daily lifting frequency, average load rate, and environmental conditions (temperature, dust, etc.).
Prioritize Safety and Compliance: Ensure the equipment complies with national standards such as GB/T 3811, and obtain the calculation basis for the main beam safety factor.
Focus on Total Life Cycle Cost: Avoid comparing only prices; comprehensively evaluate reliability, energy consumption, and after-sales support.
