GB/T 14407-2011 Crane Hoisting Mechanism Guide
ISO 4306-5:2011, the dedicated technical standard for hoisting mechanisms in overhead and gantry cranes, specifies design requirements covering type parameters, drive configurations, braking systems, wire rope winding, and rope reeving. The standard is used in conjunction with ISO 4306-1 and ISO 4306-2.
ISO 4306-5:2011 is the dedicated technical standard for hoisting mechanisms in general-purpose overhead and gantry cranes, published and implemented in 2011. The hoisting mechanism is the most critical working component of a crane, directly responsible for raising and lowering loads. Its design quality and operational reliability have a direct impact on equipment performance and lifting safety. The standard applies to the design, manufacturing, and inspection of hoisting mechanisms for electric overhead and gantry cranes.
Hoist Drive Configurations and Type Selection
The standard classifies hoisting mechanisms into two drive configurations: single-drive and dual-drive. In a single-drive arrangement, one motor drives the drum through a gearbox, offering a simple structure suitable for general-purpose cranes with a rated lifting capacity of 50 t or less. The dual-drive configuration uses two motors and two gearboxes driving the same drum from both ends, and is intended for large-tonnage cranes above 50 t or for metallurgical foundry cranes where reliability requirements are exceptionally stringent. In the dual-drive setup, if either motor or gearbox fails, the remaining drive can still operate for a limited period at a reduced rated load (approximately 60%).
Drive configuration must meet the following requirements: motor power is calculated based on rated lifting capacity, lifting speed, and mechanism efficiency (gear transmission efficiency 0.92–0.95; drum efficiency 0.96–0.98), with a motor power reserve factor of 1.2–1.4. The gearbox load-bearing capacity must not be lower than AGMA Class 10 (hardened tooth flank gears). The connection between the drum and the gearbox output shaft must use a crowned gear coupling or a shrink disc locking assembly to accommodate angular and radial misalignment. The coupling rated torque must be no less than twice the motor rated torque. For work duty classifications above A6, the hoisting mechanism must be equipped with a dual-brake configuration (service brake plus safety brake), with the two brakes operating independently.
Speed control is another key focus of the standard. Standard cranes may use a two-speed motor (8/2-pole or 6/4-pole) for two-step speed switching, suitable for general lifting operations. Applications requiring precise positioning must adopt a variable-frequency speed control system with a speed ratio of no less than 10:1 and a low-speed positioning speed not exceeding 1.5 m/min. Foundry and metallurgical cranes must use variable-frequency speed control with speed control accuracy of no less than ±1% of rated speed. The VFD system must also provide torque boost and DC injection braking, capable of delivering rated torque at zero speed to prevent load slipping. Kelude hoisting mechanisms come standard with variable-frequency speed control and a dual-brake configuration, meeting the requirements for precise positioning and safety redundancy.
Wire Rope Winding and Rope Reeving
The standard sets out detailed requirements for the wire rope winding system. Number of winding layers on the drum: single layer winding applies where the wire rope diameter is 16 mm or greater; multi layer winding is permitted where space is constrained or drum length is limited, but must not exceed 4 layers (work duty A1–A4) or 3 layers (work duty A5 and above). The ratio of drum diameter to wire rope diameter (D/d) must not be less than 20 (work duty A1–A6) or 25 (work duty A7–A8). The ratio of sheave diameter to wire rope diameter must not be less than 18 (equalizer sheaves: no less than 14). The wire rope must be secured to the drum using a clamping plate or wedge fixing method, with a fixing strength of no less than 80% of the wire rope breaking force.
The selection of rope reeving (number of wire rope falls / number of ropes leaving the drum) directly affects lifting speed and wire rope tension. The standard recommends common reeving ratios: 2–4 falls for 5–10 t rated capacity, 4–6 falls for 16–50 t, and 6–8 falls for 75–100 t. A higher reeving ratio reduces lifting speed but also lowers the tension in each individual rope, allowing smaller drum, sheave, and wire rope specifications. The reeving ratio should be selected so that the wire rope diameter does not exceed 1/20 of the drum diameter, while balancing lifting speed requirements and the mandatory wire rope safety factor of no less than 5.
The standard also specifies limits for the wire rope fleet angle (the included angle between the rope centerline and the centerline of the drum or pulley groove): the fleet angle must not exceed 3.5° when the rope winds onto or off the drum, and the maximum fleet angle in the pulley groove must not exceed 4°. Excessive fleet angles can cause the rope to lift out of the groove or rub severely against the groove sidewalls, accelerating wire rope wear. When the hook is at its extreme position, no fewer than 3 safety wraps must remain on the drum, not counting the wraps secured at the rope termination. The purpose of the safety wraps is to support the suspended load through friction force in the event of a failure at the rope fixing point, preventing the load from falling.
Braking System Configuration Requirements
The braking system of the hoisting mechanism is the most critical safety component of any crane. The standard specifies that the braking torque of the hoist brake must not be less than 1.5 times the rated hoisting torque (calculated based on the motor's rated rotational speed and the gearbox speed ratio). The brake should be mounted on the high-speed shaft of the reducer (motor side), where it delivers faster response, requires lower braking torque, and allows for a more compact brake size. The brake drum diameter is determined by the motor shaft extension dimensions and the required braking torque. The contact area between the brake shoe and the brake wheel must not be less than 80% of the shoe area. The brake release gap should be uniform on both sides, with the difference between the two shoe gaps not exceeding 0.3mm.
For hoisting mechanisms with a Work Duty Classification of A6 or above, or with a Rated Lifting Capacity exceeding 50t, the standard requires a Double Brake configuration: a service brake (for normal operational braking) plus a Safety Brake (automatic braking upon power loss). The two brakes must be installed and controlled independently, and either brake alone must be capable of reliably holding the rated load. The braking torque is distributed as follows: the service brake carries 80% of the braking torque, while the Safety Brake carries 100% (meaning the Safety Brake can brake independently on its own). The Safety Brake's actuation lag time must not exceed 0.2 seconds, ensuring rapid Brake application after a power failure. The brake's electromagnet or hydraulic push rod should be equipped with a manual release device, allowing the suspended load to be lowered slowly in the event of a power outage.
Hoist Configuration Parameter Comparison Table
The comparison table below summarizes the core configuration parameters for hoisting mechanisms across different Lifting Capacity ratings, serving as a reference for design and selection as well as user Acceptance.
| Lifting Capacity | rope reeving | Lifting Speed(m/min) | drum diametermm | wire rope diametermm | Brakingconfiguration |
|---|---|---|---|---|---|
| 5~10t | 2~4 | 5~12 | 300~400 | 12~16 | Single Braking |
| 16~32t | 4~6 | 4~8 | 400~500 | 16~22 | Single/Dual Brake |
| 50~100t | 6~8 | 2~6 | 500~800 | 22~32 | Dual Brake |
| >100t | 8~12 | 1~4 | 800~1200 | 32~42 | Dual Brake |
Brake Slip Distance and Load Test Requirements
The standard sets clear acceptance criteria for brake slip distance on the hoisting mechanism. Under rated load, the allowable load drop after brake application must not exceed 1/65 of the hoisting distance per minute (approximately 0.46 mm/kN). For example, a crane with a lifting speed of 8 m/min (0.133 m/s) has a theoretical travel distance of about 0.133 × 0.25 = 33 mm during the brake response time (calculated at 0.25 s). Adding the residual travel after full brake application, the total slip distance is typically controlled within 50–120 mm. When the slip distance exceeds the allowable limit, possible causes include excessive brake clearance, worn brake shoes, fatigued brake springs, or oil contamination on the brake wheel surface.
The load test performed before delivery is a critical step in verifying hoisting mechanism performance. The standard requires the following tests to be conducted unit by unit: No-Load Test — each mechanism runs at rated speed for 30 minutes to check operating stability and noise levels, with bearing temperature rise not exceeding 40°C; Rated Load Test (100% SWL) — lift the rated load and perform at least 5 hoisting and lowering cycles while measuring brake slip distance; Dynamic Load Test — lift 1.1 times the rated load with at least 3 hoisting and 3 lowering cycles, checking for abnormal deformation or noise in all components; Static Load Test — hold 1.25 times the rated load stationary for 10 minutes to inspect main girder deflection, weld seam integrity, and brake holding performance. Only after all tests pass can the Factory Certificate be issued.
FAQ: Brake Slip, Dual Brakes, and Reeving
Q: What should be done when the hoist brake slip distance exceeds the limit?
A: First, check whether the brake clearance is excessive and adjust it to 0.5–1.0 mm. Replace the brake shoes if wear exceeds the allowable limit. Next, inspect the brake springs for fatigue — replace them if the free height has decreased by more than 5%. Finally, check the brake wheel surface for oil contamination and clean it with alcohol.
Q: What maintenance considerations apply to dual brake systems?
A: The two braking systems in a dual brake configuration must be maintained and inspected separately. A single-brake test should be performed quarterly — de-energize one brake and operate with the other alone. The braking torque of each brake should be measured and recorded independently.
Q: Is a higher rope reeving ratio always better?
A: Not necessarily. A higher reeving ratio reduces wire rope tension but also lowers the lifting speed. The reeving selection should ensure that the wire rope diameter does not exceed 1/20 of the drum diameter, while still meeting the required lifting speed and maintaining a wire rope safety factor of no less than 5.
Q: What is the relationship between GB/T 14407 and GB/T 3811?
A: GB/T 3811 serves as the general design standard for cranes, defining the general methodology for load calculation and structural verification. GB/T 14407 is the dedicated product standard for hoisting mechanisms, specifying type parameters and configuration requirements. The latter is based on the design principles established in the former.
