Electric Single-Girder Crane Specifications & Acceptance
JB/T 1306-2008, the product standard for Electric Single-Girder Cranes, governs the design and manufacture of these machines.The standard specifies the type parameters, technical requirements, test methods, and inspection rules for Electric Single-Girder Cranes, covering the complete technical specifications for common models including LD Type, LDA Type, and LX Type.
JB/T 1306-2008 is the industry product standard for Electric Single-Girder Cranes, released in 2008 to replace the 1994 edition. As the most common type of light and small lifting equipment, Electric Single-Girder Cranes offer a Rated Lifting Capacity of 1–20 t and spans from 7.5 m to 31.5 m, making them widely used for Material Handling in factory workshops, warehouses, storage yards, and maintenance bays. The standard applies to Electric Single-Girder Cranes that use an Electric Hoist as the Hoisting mechanism, and it defines the full technical requirements from Design & Manufacturing through inspection and acceptance.
Type Parameters and Structural Requirements
The standard defines the basic types and parameter series for Electric Single-Girder Cranes. Based on the Main Girder structure, cranes are classified into two configurations: I-Beam main girders (suitable for 1–5 t / short spans) and Box girder main girders (suitable for 5–20 t / medium-to-long spans). In terms of Control Method, cranes are available with floor-mounted controls (pendant station / Remote Control) or cabin operation. The Rated Lifting Capacity series includes seven levels: 1 t, 2 t, 3 t, 5 t, 10 t, 16 t, and 20 t. The Span series ranges from 7.5 m to 31.5 m, increasing in increments of 1.5 m or 3 m. Standard Lifting Height options are 6 m, 9 m, 12 m, 18 m, 24 m, and 30 m. Work Duty is classified into three levels based on usage frequency: A3 to A5; general workshop operations typically select A3, while frequent-duty applications use A4 to A5.
The Main Girder is the most critical structural component of an Electric Single-Girder Crane, and the standard sets out specific requirements for its design and manufacture. I-Beam main girders must use hot-rolled I-Beam sections conforming to GB/T 706, in Q235B or Q355B material. Box girders are fabricated from welded Steel Plate, with Web plate and Flange plate thicknesses of no less than 6 mm (for cranes under 10 t) or 8 mm (for 10 t and Above). After fabrication, the main girder must be pre-cambered to a value of 1/800 to 1/1000 of the Span, compensating for elastic Deflection under Full load. The static deflection of the main girder under rated load must not exceed 1/800 of the Span. Main girder Weld Seams are subject to Visual inspection and sampling-based Ultrasonic Testing (UT), with a minimum sampling rate of 20% for Butt Welds.
The End Carriage structure is equally important. The standard specifies that End Carriages must use a Box girder or C-section welded structure with material grade no lower than Q235B. The connection between the End Carriage and the Main Girder is made using High-Strength Bolts or Welding. When High-Strength Bolts are used, the bolt property class must be no lower than 8.8, and Tightening Torque must be applied in accordance with the specification. The mounting base for the crane bridge wheel on the End Carriage must be machined as an integral unit after welding and stress-relieving, ensuring the Flatness and positional accuracy of the wheel mounting surface. Both ends of the End Carriage must be fitted with Buffer mounting bases and limit stops. The Reducer / Gearbox of the Crane Travel Mechanism is mounted using either a shrink-disc or flange-mounted arrangement, and the connection between the Reducer output shaft and the Wheel Axle is made through a crowned gear coupling, which accommodates a certain Angle deviation.
Electric Hoist Matching Requirements
Electric Single-Girder Cranes use an Electric Hoist as the Hoisting mechanism, and the standard specifies the requirements for hoist selection and matching. The Electric Hoist must comply with the technical provisions of JB/T 9008.1, with a typical Lifting Speed of 4–8 m/min (8/0.8 m/min for two-speed hoists) and a Travel Speed of 20–30 m/min. The Hoisting Motor must be a Conical-Rotor Brake Motor, and the brake slip distance under rated load must not exceed 80 mm. The Travel Motor uses either a side-magnet brake or a Conical-Rotor Brake Motor, ensuring reliable Braking after power-off. The Wire Rope safety factor of the hoist must be no less than 5, and the Hook must comply with GB/T 10051. The hoist is suspended using an electric trolley arrangement, with the trolley running on the lower flange of the I-Beam.
The matching and installation of the Electric Hoist to the Main Girder is a critical aspect of product design. The trolley wheel must run on the tread surface of the lower flange of the I-Beam, and the Wheel Tread must be machined to a conical profile that matches the flange slope of the I-Beam. Horizontal Guide Rollers (anti-sway rollers) must be fitted on both sides of the trolley to prevent skewing during operation. Electrical control of the hoist is provided via a pendant station or Remote Control, with the pendant station control voltage set to safety extra-low voltage (36 V or 42 V). The hoisting limiter is a power-cutoff type limit switch mounted on the hoist body, while Travel Limit Switches (for both Long Travel / Bridge Travel and trolley travel) use Micro Switch types installed at both ends of the Crane Rail. Kelude Heavy Industry equips its Electric Single-Girder Cranes with CD1/MD1 type Electric Hoists, keeping the brake slip distance during Hoisting within the limits specified by the standard.
Electrical Control System Requirements
The electrical system of an electric single-girder crane is relatively straightforward, yet it must comply with stringent safety requirements. The standard specifies that the entire machine's electrical control circuit must operate at safety extra-low voltage (36V/42V), with the main circuit rated at 380V/50Hz. The control cabinet (or electrical cabinet) should be mounted at one end of the main girder or on the side of the end carriage, with a protection rating of at least IP43. Main circuit conductors are sized at 1.25 times the motor's rated current, while control circuit conductors must have a cross-section of no less than 1.0mm². Cables should be YCW rubber-sheathed or RVV PVC-jacketed types, secured to a cable trolley or cable tray along the main girder side, allowing free movement with the trolley without tangling.
Safety protection devices are mandatory on electric single-girder cranes. The standard requires the following safety devices: a lifting height limit switch (break-contact or counterweight type, which cuts power to the hoisting circuit when activated), crane bridge and trolley travel limit switches (micro switch type, cutting power to the travel circuits when activated), an overload limiter (pin-type or plate-ring sensor, which triggers an alarm and cuts the hoisting circuit at 110% overload), an emergency stop button (red mushroom-head type, installed on the pendant station and cabin control panel), earthing protection (with a total grounding resistance no greater than 4Ω), undervoltage protection (preventing automatic restart after a power interruption), and zero position protection (ensuring the main power can only be energized when all mechanism controllers are in the neutral position).
Electric Single-Girder Crane Specification Comparison
The comparison table below outlines the core parameters for standard electric single-girder crane configurations, serving as a reference for user selection and acceptance.
| Lifting Capacity(t) | Span Range(m) | Main Girdertype test | Hoist Model | travel speed(m/min) |
|---|---|---|---|---|
| 1~5 | 7.5~22.5 | I-Beam | CD1/MD1 Type | 20~30 |
| 5~10 | 10.5~25.5 | Box-type | CD1/MD1 Type | 20~30 |
| 16~20 | 13.5~31.5 | Box-type | HC Type | 15~25 |
Test Methods and Factory Acceptance
Every electric single-girder crane must undergo individual inspection and testing before delivery. The No-Load Test runs each mechanism at rated speed for 30 minutes to verify operating stability, noise levels, and bearing temperature rise (not exceeding 40°C). The Rated Load Test (100% SWL) exercises the full duty cycle—hoisting, lowering, Long Travel, and Cross Travel—while measuring brake slip distance (max 80 mm) and main girder static deflection (max L/800). The Dynamic Load Test lifts 1.1 times the rated load with each mechanism cycled at least three times, confirming no abnormal deformation of structural components, no weld seam cracking, and proper brake function. The Static Load Test holds 1.25 times the rated load for 10 minutes, then checks for permanent deformation of the main girder (residual deflection after unloading must not exceed L/2000).
The standard also specifies acceptance testing requirements after on-site installation. The acceptance test must include: crane rail installation accuracy checks (span deviation, straightness, elevation difference, etc.), insulation resistance testing of the complete crane (main circuit ≥ 0.5 MΩ), verification of all safety device functions (limit switch actuation points and accuracy, overload limiter alarm and cut-off points, emergency stop button coverage), grounding resistance measurement (≤ 4 Ω), and confirmation of travel direction and speed for all mechanisms. Upon successful completion, an Acceptance Report is issued containing all test data and conclusions, which serves as a mandatory document for equipment handover and special equipment use registration.
FAQ: Single Girder Crane Essentials
Q: Why does the main girder of an electric single-girder crane need pre-camber?
A: Pre-camber compensates for the elastic deflection that occurs under full load. Without it, the girder would sag visibly when loaded, undermining operator confidence and trolley travel smoothness. The pre-camber value is typically set at L/800 to L/1000.
Q: What is the difference between single-girder and double-girder electric cranes?
A: An electric single-girder crane has one main girder and uses an electric hoist as the hoisting mechanism, with a Rated Lifting Capacity of 1 to 20 t. A double-girder crane has two main girders and uses a trolley hoist, with capacities starting at 5 t and reaching several hundred tons. Single-girder cranes are more cost-effective but have lower capacity and Lifting Height limits.
Q: What is the service life of an electric single-girder crane?
A: Under proper design life and maintenance conditions, the main girder structure of an electric single-girder crane has a design service life of typically 20 years. The electric hoist itself has a service life of approximately 10 to 15 years. Consistent routine maintenance can extend the actual service life of the entire crane.
Q: Does an electric single-girder crane require special equipment use registration?
A: According to the special equipment catalog and TSG 51 Safety Technical Specification for Special Equipment, electric single-girder cranes with a Rated Lifting Capacity above 3 t are classified as special equipment and must undergo use registration and periodic inspection. Cranes rated at 3 t or below fall outside the scope of special equipment regulation.
