GB/T 6974.5-2008 Overhead and Gantry Crane Terms

GB/T 6974.5-2008 is Part 5 of the crane terminology series, specifically governing the definitions of terms for overhead and gantry cranes. As the most widely used crane types, a unified terminology framework is essential for design & manufacturing, installation acceptance, and operation and maintenance. This article provides a systematic breakdown of the core terms defined in the standard.

Standard Scope and Terminology Framework

GB/T 6974.5-2008 is the fifth part of the GB/T 6974 "Cranes — Vocabulary" series, dedicated to standardizing terminology for overhead and gantry cranes. These crane types account for the largest share of industrial lifting equipment, and their terminology spans a wide range of structural and technical concepts. The standard compiles approximately 180 specialized terms, organized in a logical sequence: bridge configuration → main structural components → travel mechanisms → hoisting mechanism → trolley → safety devices → performance parameters. These terms serve not only as the standard language for design and manufacturing but also as the common basis for equipment selection, operator training, and fault description.

Bridge Configuration Terminology

The standard clearly defines the terminology for each overhead and gantry crane type: Overhead crane — a crane whose bridge is supported directly on factory building crane rails via travel mechanisms at both ends. Based on bridge structure, it is classified into: Single-girder bridge crane — consisting of a single I-beam main girder and a trolley (or electric hoist), typically with a lifting capacity of ≤10 t. Double-girder bridge crane — a bridge comprising two box-section main girders and end carriages, with the trolley running on rails atop the main girders, offering lifting capacities from 5 to 500 t. By main girder cross-section, types include box girder, truss girder, and cellular girder bridge cranes.

Gantry crane — a crane whose bridge is supported on ground rails by legs on both sides. By main girder configuration: single-girder gantry crane (one main girder + one leg on each side) and twin-girder gantry crane (two main girders + two legs). By leg type: L-type legs (one leg L-shaped, the other C-shaped), A-type legs (both legs A-shaped), and U-type legs (both legs U-shaped, allowing loads to pass through the leg opening). By cantilever configuration: non-cantilever gantry crane, single-cantilever gantry crane, and double-cantilever gantry crane.

Main Structural Component Terms

The standard precisely defines the terms for the main structural components of overhead and gantry cranes: Main girder — the primary load-bearing member of the bridge, resisting bending moments and shear forces from the trolley dead weight and the lifted load; typically of box-section or truss construction. End carriage — the transverse member connecting the ends of the main girders, carrying the crane bridge wheels and travel mechanism, and transmitting the main girder loads to the wheels. Trolley frame — the steel structure platform that houses the hoisting mechanism and trolley travel mechanism, running on rails along the main girders. Outrigger (leg) — the vertical structural member (one of a pair) in a gantry crane that connects the main girder to the ground foundation and transmits the main girder loads. Bottom cross beam — the connecting beam between the lower ends of the two legs in a gantry crane, carrying the bridge travel mechanism. Cabin (operator cab) — the enclosed space from which the operator controls the crane, suspended from one end of the bridge (overhead crane) or mounted on one side of the portal frame (gantry crane).

Mechanism and Performance Parameter Terms

The standard standardizes the performance parameter terminology for overhead and gantry crane mechanisms: Hoisting speed — the lifting/lowering speed of the lower hook driven by the hoisting motor (m/min), typically available in fast/slow two speeds (main hoist and auxiliary hoist). Long travel speed — the travel speed of the entire crane along the factory building crane rails (m/min), typically in the range of 20–80 m/min. Cross travel speed — the travel speed of the trolley along the main girder rails (m/min), typically in the range of 20–60 m/min. Work duty (classification) — a comprehensive grading indicator reflecting the degree of full-load operation and frequency of use, with 8 grades from A1 to A8. Utilization class — a grade indicating the frequency of use of the crane (U0–U9, classified by the total number of working cycles). Load spectrum — a grade indicating the magnitude of loads the crane is subjected to (Q1–Q4).

Safety Device Terminology

The standard unifies the terminology for safety devices on overhead and gantry cranes: Lifting capacity limiter (load limiter) — a safety device that monitors the lifting capacity and triggers an alarm and cuts power to the hoisting-up direction in the event of overload. Height limit switch — a device that cuts power to the hoisting-up direction when the hook reaches its maximum permissible height. Travel limit switch — a device that cuts power to the travel motors before the crane bridge or trolley reaches the end of the rail. Buffer — a device that absorbs the residual kinetic energy of the crane at the end of travel and cushions impact. Rail clamp — an anti-wind safety device specific to outdoor gantry cranes, which clamps onto the rail via grippers to prevent the crane from sliding in strong winds. Anchor device — a device used in conjunction with the rail clamp that secures the crane to the rail by means of pins or tie bars. Anti-collision device — a device used when multiple cranes operate on the same rail, which detects the distance between adjacent cranes and stops travel within a safe distance. Kelude technical personnel strictly use the standard terminology specified in GB/T 6974.5 in solution design and customer communication.

Overhead and Gantry Crane Terminology Comparison Table

The comparison table below outlines the core parameter configurations for overhead and gantry crane terminology, providing a practical reference for equipment selection and operational use.

FAQ