FEM 9.321 Main Girder Design Specification: Standard Interpretation
FEM 9.321 Main Girder Design Specification is a key technical standard in the crane industry, serving as a dedicated specification for the steel structure design of bridge crane main girders.
This standard provides a unified technical basis for design personnel, inspection bodies, and end users. Kelude Heavy Industry strictly adheres to its technical requirements throughout product development and manufacturing.
Scope and Positioning of the Standard
FEM 9.321 Main Girder Design Specification defines the technical requirements and safety indicators for crane main girder design, covering all types of lifting appliances with a rated lifting capacity above 0.5t.
Core Technical Parameter Framework
Under FEM 9.321, the design and manufacturing of main girders must satisfy a stringent set of core technical parameters. These parameters are established through extensive test data and safety engineering principles, covering the full spectrum from material selection to structural design. The safety factor ranges specified in the standard account for fatigue life and limit load conditions under severe operating environments. In engineering practice, design personnel must translate these requirements into concrete design parameters, ensuring that the load capacity of every component meets the mandated safety requirements. The parameter cards below summarize the standard's core technical indicators:
Comparative Analysis of Key Technical Parameters
| Item | technical requirements | Description |
|---|---|---|
| Girder Type Selection | Box(General Purpose)/I-Beam(Light)/Folded Plate(Long Span) | According to Spanand Lifting Capacity |
| Deflection | Full load≤L/800, No-load Camber≥L/1500 | Side bow / lateral bow≤L/2000 |
| Web plate Stability | h0/tw≤160Add Horizontal Stiffeners When Required | Vertical Stiffener Spacing1.0~1.5hw |
| Safety factor | ≥1.5(Yield)/2.0(Ultimate) | dynamic load factor1.1~1.4 |
| Fatigue Design | A6Grade and Above | Infinite Life Method/Finite Life Method |
| camber | Main Girder No-load Camber≥L/1500 | Compensation Elasticity Deformation |
Inspection Requirements & Intervals
FEM 9.321 sets out clear inspection requirements for main girder design specifications, covering Factory Acceptance Test, Type Test, and periodic inspection. Factory Acceptance Test must be carried out on each crane at the manufacturer's facility by the quality control department, and each unit that passes inspection must be accompanied by a detailed inspection report and a certificate of conformity. Type Test is required when a new product enters production for the first time, when manufacturing is transferred to a different facility, or when significant structural changes are introduced. For cranes already in service, the periodic inspection interval is determined by the work duty and operating environment, and generally must not exceed 12 months. For heavy-duty cranes operating continuously at A7~A8 level, the inspection interval should be shortened to 6 months.
| Item | technical requirements | Description |
|---|---|---|
| main girder deflection | Level Instrument Measurement | Annual+≤L/800 |
| Weld Seam UT | ultrasonic testing | Annual+100%Main Weld Seam |
| Web plate Stability | Stiffener Inspection | Annual+Deformation/Weld Detachment |
| Coating Corrosion | Visual+539aThickness Gauge | Annual+Damage>5%Repair |
Safe Operation and Management Requirements
Under FEM 9.321, safe operation and routine management are central to compliance. The standard places strong emphasis on operator qualification and training, requiring that all operators complete specialized training and obtain the necessary certifications before operating equipment. User units must establish a comprehensive equipment file management system that documents the full lifecycle of the equipment, including installation, use, maintenance and inspection. Any safety hazard identified must be addressed through the rectification procedure specified in the standard to keep the equipment safe and controllable at all times. In addition, the standard imposes operational restrictions under extreme operating conditions—for example, lifting operations are prohibited when wind speed exceeds the prescribed limit.
FEM 9.321 FAQ: Deflection, Camber & Fatigue Design
Q: What are the main girder deflection limits under FEM 9.321?
A: Full-load deflection ≤ L/800, no-load camber ≥ L/1500, and side bow ≤ L/2000. Exceeding these limits affects Cross Travel and Positioning Accuracy.
Q: How are web plate stiffeners arranged?
A: When h0/tw > 80, add vertical stiffeners; when > 160, add horizontal stiffeners as well. Vertical spacing should be 1.0–1.5 hw.
Q: When is fatigue design mandatory?
A: Fatigue design is required for FEM duty class A6 and Above. Welding details are classified per FAT80–100.
Q: What is the purpose of camber?
A: Camber compensates for elastic deflection caused by the Dead Weight of the Main Girder and the Lifting Capacity. It ensures optimal Levelness when the Trolley reaches mid-span.
Kelude — Specialized in crane design and manufacturing, with products fully compliant with the FEM 9.321 standard system.
