GB/T 28757 Bridge and Gantry Crane Terminology Standard
GB/T 28757, "Bridge and Gantry Cranes—Terminology," serves as the foundational terminology standard for the crane industry, administered by the National Technical Committee for Standardization of Lifting Appliances (SAC/TC 227). This standard establishes unified definitions for core terms and their meanings related to the design, manufacturing, inspection, operation, and maintenance of bridge and gantry cranes. It applies to general-purpose bridge and gantry cranes with a rated lifting capacity of no less than 3.2 t.
Standardized terminology is the cornerstone of effective technical communication within the crane industry. In real-world projects, misunderstandings arising from inconsistent terminology frequently lead to contractual disputes, technical integration errors, and costly installation rework. GB/T 28757 establishes a comprehensive terminology framework that spans from complete machinery to individual components, organized into the following six key categories.
1. Crane Classification Terms
| Term | Definition | English Equivalent |
|---|---|---|
| Bridge Crane / Overhead Crane | End-carriage supported directly on elevated runway via travel mechanisms Crane Railoncrane | Overhead travelling crane |
| Gantry Crane | Bridge supported on both sides Outriggersupported on the ground Crane Railor on foundationscrane | Gantry crane |
| Electric Single-Girder Crane | with Electric Hoistas Hoisting mechanism, single-girder Main Girderon Bridge Crane / Overhead Crane | Single girder overhead crane |
| Electric Double-Girder Crane | with Trolleyas Hoisting mechanism, double-girder Main Girderon Bridge Crane / Overhead Crane | Double girder overhead crane |
| Suspension Crane | underslung from roof trusses or supporting structure bottom chords Bridge Crane / Overhead Crane | Underslung crane |
| Metallurgical Crane | for metallurgical process applications Special overhead crane | Metallurgical crane |
Key Parameters and Definitions
- Rated Lifting Capacity (Gn): The maximum load mass the crane is permitted to lift, expressed in tons (t). This includes the weight of the lifting spreader but excludes the hook block's dead weight.
- Span (S): The horizontal distance between the centerlines of the bridge runway rails, expressed in meters (m).
- Lifting Height (H): The vertical distance between the lowest and highest working positions of the lifting spreader, expressed in meters (m).
- Work Duty / Classification: A grading parameter that characterizes the crane's operational profile, determined by combining the utilization class (U0–U9) and the load spectrum (Q1–Q4). General purpose bridge cranes commonly fall within A3 to A7.
- Working Speeds: Includes lifting speed, cross-travel speed, and long-travel speed, each expressed in m/min.
- Duty Classification (S1–S10): Defined per IEC 60034-1 for motor operating modes. The hoisting mechanism typically uses S3 (intermittent periodic duty) or S4 (intermittent periodic duty with starting).
Structural Component Terminology
| Term | Definition | common structural configuration |
|---|---|---|
| Main Girder | to withstandlifting loadand Dead Weightprimary load-bearing member | box girder, Truss Girder, offset rail box girder |
| End Carriage | connecting Main Girderboth ends and Crane Travel Mechanismconnecting member | box-type End Carriage, forged wheel End Carriage |
| Trolley Frame | supporting Hoisting mechanismand Trolley Travel Mechanismframe structure | Weldingframe, Casting Trolley Frame |
| Outrigger | Gantry Craneconnecting within Main Girderto the ground Crane Railvertical orinclination/tiltsupport member | rigid Outrigger, flexible Outrigger |
| Cabin / Operator Cab | for operationcraneenclosed or semi-enclosed working space | Fixingcommon structural configuration, with Trolleymobile |
| Walkway / Platform/Guardrail | maintenance and access platforms with guarding | per GB 4053.3design |
Mechanisms and Component Terminology
- Hoisting mechanism: The assembly that raises and lowers the lifting spreader, comprising the electric motor, brake, reducer, drum, wire rope, and hook block.
- Trolley travel mechanism: Drives the trolley along the main girder rails, typically using individually driven wheels.
- Crane travel mechanism: Drives the entire crane along the runway rails in the workshop.
- Drum: The cylindrical component around which the wire rope is wound to raise and lower the load. Its diameter is determined per GB/T 3811 Crane Design Standard.
- Pulley: A grooved wheel that changes the direction of the wire rope or forms a pulley block.
- Hook block: The lifting attachment assembly consisting of the hook, cross beam, pulleys, and bearings.
Safety Device Terminology
- Lifting capacity limiter: A safety device that automatically cuts power to the hoisting drive when the load exceeds the preset value. Combined error ≤ ±5%.
- Lifting height limit switch: A limit device that prevents the lifting spreader from exceeding the designed lifting height. This is a mandatory safety device.
- Travel limit switch: A device that restricts the extreme travel positions of the crane bridge or trolley.
- Buffer: A device that absorbs impact energy when the crane or trolley contacts the end stops on the rail. Available in elastic and hydraulic types.
- Anti-wind anti-slip device: Prevents outdoor cranes from sliding along the rails under wind force. Includes rail clamps and anchor devices.
- Interlock protection: A safety device that automatically cuts power to the travel mechanisms when the cab door or access gate to the crane is opened.
Inspection and Testing Terminology
- Type test: A comprehensive verification test confirming that the product design meets all standard requirements. Mandatory before new product launch or after a standard update.
- Factory test: Functional and performance verification performed on each unit before it leaves the factory.
- Static load test: Conducted at 1.25 times the rated load to verify structural load-bearing capacity and permanent deformation of the main girder (≤ S/2000).
- Dynamic load test: Conducted at 1.1 times the rated load to verify the operational function of all mechanisms and the effectiveness of safety devices.
- Initial inspection: Safety performance inspection carried out after installation and before the equipment is put into service.
- Periodic inspection: In-service safety performance inspection performed at intervals specified by TSG Q7015, typically every 2 years.
FAQ
Q: What is the difference in application scope between GB/T 28757 and GB/T 6974.1 "Cranes — Vocabulary"?
A: GB/T 6974.1 is the general terminology standard covering all crane types, including mobile, tower, bridge, and gantry cranes. GB/T 28757 focuses specifically on bridge and gantry cranes, adding dedicated terms such as offset rail box girder, flexible outrigger, and C-type outrigger. For bridge and gantry crane projects, both standards should be used together — refer to GB/T 6974.1 for general terminology and GB/T 28757 for bridge-and-gantry-specific terms.
Q: What is the difference between duty classifications A1~A8 in GB/T 28757 and motor duty S1~S10?
A: The duty classification (A1~A8) is a service-life grading parameter for the complete bridge or gantry crane, determined per GB/T 3811 from the combination of utilization class (U0~U9) and load spectrum (Q1~Q4). It is used for crane selection and structural fatigue calculations. Motor duty (S1~S10) is classified per IEC 60034-1 and is used for motor thermal capacity verification and duty-cycle matching. Hoist motors are typically selected with S3-40% or S4-30% duty, while travel mechanism motors use Motor Duty S1 — Continuous Running at Constant Load Until Thermal Equilibrium. These two classification systems serve different purposes and must not be interchanged.
Q: How do the safety device definitions in GB/T 28757 align with the inspection requirements of GB 6067.1?
A: GB/T 28757 provides the standardized terminology (e.g., "lifting height limit switch," "lifting capacity limiter"), while GB 6067.1 "Safety Rules for Lifting Appliances" specifies the mandatory installation conditions, operating accuracy, and inspection requirements for these devices. For example, GB/T 28757 defines the buffer categories (elastic/hydraulic), while GB 6067.1 requires a hydraulic buffer when the impact speed exceeds 0.7 m/s. Equipment inspections are governed by the safety code, while technical documentation follows the terminology standard.
Q: How does Kelude apply GB/T 28757 to align international terminology in export projects?
A: Kelude uses GB/T 28757 as the terminology baseline for all technical proposals and factory documentation, while also preparing bilingual terminology cross-reference tables based on ISO 4306-1. A practical example: in the QD type 32t double-girder bridge crane export project, key terms such as "main girder camber," "trolley rail gauge," and "end carriage connection" were provided with definitions in both Chinese and English. This allowed the third-party inspection body (SGS/TÜV) to directly cross-reference ISO standards during review, eliminating technical clarification delays caused by terminology ambiguity. This approach has been standardized into the delivery workflow for all export projects.
