GB/T 27996-2011 Mobile Crane Hoisting Mechanism Standard
GB/T 27996-2011 "Mobile Cranes—Hoisting Mechanisms" is the dedicated standard governing hoisting mechanisms for mobile cranes. It specifies the technical requirements, safety requirements, and test methods for hoisting mechanisms used in mobile cranes—including truck cranes, all-terrain cranes, and crawler cranes—and applies to both hydraulic-driven and mechanically driven hoist winch mechanisms.
Scope and Role of the Standard
GB/T 27996-2011 provides comprehensive requirements specifically for the hoisting mechanisms of mobile cranes. As the most critical load-bearing system on a mobile crane, the hoisting mechanism's reliability directly impacts lifting operation safety. The mechanism comprises five major components: a hydraulic motor, reducer, drum, brake, and wire rope. The hydraulic motor is typically a variable-displacement piston type, enabling stepless speed regulation—automatically delivering high speed under light loads and low speed under heavy loads. The reducer uses a planetary gear design, offering compact dimensions, high transmission ratios, and excellent load-bearing capacity.
The drum is a welded structure rolled from Q345B (≈S355J2) steel plate, with a machined spiral rope groove that guides the wire rope into orderly layers. Two independent brakes are mandatory: a service brake (normally closed, spring-applied with hydraulic release, mounted on the high-speed shaft at the hydraulic motor output) and a safety brake (normally open, mounted on the low-speed shaft at the drum, which automatically engages upon hydraulic system failure). The wire rope is high-strength steel with a nominal tensile strength of ≥1770 MPa and a safety factor of ≥5. Kelude Heavy Industry manufactures in strict compliance with national standards.
Technical Performance Requirements
The standard defines performance criteria covering rated lifting speed, minimum stable speed, brake slip distance, and hydraulic system efficiency. Rated lifting speed refers to the hook's hoisting or lowering speed (m/min) under rated load. Mobile cranes typically feature automatic speed regulation—reaching maximum speed at 20%–30% of rated load and reducing speed as load increases. The minimum stable speed must not exceed 2 m/min, meeting the demands of precision lifting and fine positioning.
Brake slip distance must be ≤100 mm for lifting heights up to 20 m, or ≤200 mm for lifting heights above 20 m. Drum rope capacity must be at least 1.2 times the rated lifting height, including two safety wraps and allowance for end fastening. Total hydraulic motor efficiency (mechanical × volumetric) must be ≥90%. Single-stage planetary reducer efficiency must be ≥96% (≥88% for three stages). The hydraulic system must maintain oil temperature at ≤80°C after one hour of continuous operation under rated conditions, with an absolute maximum of ≤90°C—exceeding this requires shutdown for cooling.
Safety Devices and Testing & Inspection
Safety devices required by the standard include dual brakes, a counterbalance valve, over-hoisting protection, over-lowering protection, overload protection, and a free-fall lowering function. The dual brake system comprises a service brake (high-speed shaft brake) and a safety brake (low-speed shaft brake), each independently controlled—either brake alone must be capable of holding the rated load. Both brakes must be of the normally closed type (spring-applied), engaging automatically upon any loss of power. The counterbalance valve is installed in the lowering circuit of the hoist motor; in the event of a hydraulic pipeline rupture, it locks automatically to prevent uncontrolled load descent, with its set pressure at 1.3 times the system's maximum working pressure.
The free-fall lowering function allows the hook and suspended load to descend by gravity via a clutch that disengages the drum from the reducer. This function is permitted only with an empty hook or light loads (≤30% of rated load), with descent speed controlled by the operator using a foot-operated brake. The standard mandates the following tests: a no-load test (at least 5 hoisting and lowering cycles), a rated load test (3 full hoisting and lowering cycles with brake slip distance measurement), a 1.25× static load test (1.25 times rated load held for 10 minutes), and a 1.1× dynamic load test (3 full hoisting and lowering cycles, with each brake independently verified for reliable braking).
Standard Comparison and Application Recommendations
GB/T 27996-2011 overlaps with ISO 4301 (crane design specification) and JB/T 5317 (chain electric hoists) in certain hoisting mechanism design requirements, but each takes a different focus. This standard is specifically tailored to the operating characteristics and environment of mobile crane hoisting mechanisms, imposing stricter requirements on hydraulic drive system reliability, dual brake redundancy, and counterbalance valve protection against hydraulic line failure.
In practice, mobile crane operators are advised to use this standard in conjunction with complementary standards such as JB/T 8713 (conductor rails) and GB/T 28264 Safety Monitoring and Management System to ensure comprehensive safety coverage from design and manufacturing through operation and maintenance. Regularly scheduled no-load and load testing of the hoisting mechanism—verifying brake and counterbalance valve reliability—is a critical element of equipment management.
Kelude Heavy Industry: Engineered for the Toughest Lifting Challenges
Kelude Heavy Industry specializes in the design and manufacture of heavy-duty industrial cranes and hoisting solutions. Our product range is built to deliver exceptional performance, reliability, and safety in the most demanding environments, from steel mills and shipyards to power plants and general manufacturing facilities.
Comprehensive Crane Solutions for Industrial Applications
We provide a full spectrum of overhead traveling cranes, gantry cranes, and electric hoists, each engineered to meet specific operational requirements. Our offerings include single-girder and double-girder bridge cranes, low-headroom designs for space-constrained facilities, and explosion-proof configurations for hazardous areas. Every crane is designed with advanced features such as anti-sway control, variable-frequency drives for precise load positioning, and robust safety systems to ensure smooth, secure operation.
| Crane Type | Typical Capacity Range | Key Application Areas |
|---|---|---|
| Single-Girder Bridge Crane | 1 – 20 short tons (0.9 – 18.1 metric tons) | Workshops, warehouses, maintenance bays |
| Double-Girder Bridge Crane | 10 – 150 short tons (9.1 – 136.1 metric tons) | Steel yards, foundries, heavy fabrication |
| Gantry Crane (Rubber-Tired or Rail-Mounted) | 5 – 300 short tons (4.5 – 272.2 metric tons) | Shipyards, precast yards, intermodal terminals |
| Electric Wire Rope Hoist | 1 – 50 short tons (0.9 – 45.4 metric tons) | General lifting, machine shops, assembly lines |
Our engineering team works closely with clients to customize cranes for specific duties, including high-cycle applications, extreme ambient conditions, and specialized material handling needs. From initial design and finite element analysis to fabrication, testing, and on-site commissioning, Kelude provides a turnkey solution backed by comprehensive after-sales support.
Precision Engineering and Robust Safety Standards
Safety and reliability are at the core of every Kelude crane. Our designs adhere to international standards including ISO 4301 for crane classification, ISO 12480 for safe use, and IEC 60204-32 for electrical equipment. We integrate multiple redundant safety features such as load limiters, buffer systems, anti-collision devices, and emergency stops, ensuring fail-safe operation even under peak loads.
All critical components—from hoist mechanisms and end carriages to control systems—are sourced from reputable manufacturers and subjected to rigorous quality checks. Our production facilities are equipped with advanced machining and testing equipment, allowing us to maintain tight tolerances and deliver consistent product quality. Every crane undergoes a full-load test and functional verification before shipment, providing our customers with complete peace of mind.
Customized Solutions and Global Support Network
We understand that every facility has unique lifting requirements. Kelude offers extensive customization options, including special spans, lifting heights, and control systems (pendant, radio remote, or cabin operation). Our in-house engineering team can adapt our standard designs to integrate with existing infrastructure or to meet specific process demands, ensuring seamless integration into your workflow.
With a global service network, we provide prompt technical support, spare parts availability, and maintenance services across the United States and Europe. Our commitment extends beyond the initial sale—we partner with our customers to optimize crane performance, extend equipment lifespan, and enhance operational efficiency throughout the entire lifecycle of the product.
Contact Kelude for Your Material Handling Needs
Whether you require a standard electric hoist or a large-capacity custom-engineered gantry crane, our team is ready to assist. Contact Kelude Heavy Industry today to discuss your project with our application specialists and discover how our solutions can improve your productivity and safety.
Q: What is the typical lead time for a custom crane order?
A: Lead times vary based on crane configuration and complexity. Standard hoists can ship within a few weeks, while custom-engineered bridge or gantry cranes typically require 12-20 weeks from design approval to delivery.
Q: Do you provide installation and commissioning services?
A: Yes, we offer complete installation, testing, and commissioning services performed by our certified technicians. We also provide operator training and comprehensive documentation to ensure safe and efficient crane operation.
Q: What after-sales support and warranty do you offer?
A: We provide a standard 12-month warranty covering parts and workmanship. Our global support network offers extended service contracts, preventive maintenance programs, and rapid response spare parts dispatch to minimize downtime.
| Hoisting mechanism Component | type test | Critical Parameter | safety requirements |
|---|---|---|---|
| Hydraulic Motor | Piston-Type Variable Displacement | Efficiency≥90% | stepless speed regulation |
| Reducer / Gearbox | planetary gear | Single-Stage Efficiency≥96% | Three-Stage≥88% |
| Drum | Q345B (≈S355J2)Welding | rope capacity≥1.2Times H | spiral rope Groove |
| Brake | Normally Closed Spring Type | Double Brake | Individually Operable Set Braking |
| Wire Rope | High Strength | Tensile≥1770MPa | Safety factor≥5 |
| Test Type | test conditions | Acceptance Criteria | inspection interval |
|---|---|---|---|
| No-Load Test | Lifting and Lowering≥5Cycles | Smooth Operation | factory/after installation |
| Rated Load Test (100% SWL) | Full Travel3Cycles | Braking Load Drop≤100mm | Annual |
| Static load test | 1.25Times×10min | Nonepermanent deformation | type test |
| Dynamic Load Test | 1.1Times×3Cycle | reliable braking | type test |
| Hydraulictemperature rise | Continuous1h | Oil Temperature≤80°C | Per500h |
Related Standards: ISO 12480-2:2008 — Cranes — Safe Use — Part 2: Mobile Cranes · FEM 1.001 — Cranes — Vocabulary — Part 1: General (replacing GB/T 26474-2011)
Related Standards
Frequently Asked Questions
Q: Why are two brakes required on the hoisting mechanism of a mobile crane?
A: The service brake is mounted on the high-speed shaft (at the hydraulic motor output). It delivers low braking torque but responds quickly, handling normal braking duties. The safety brake is mounted on the low-speed shaft (at the drum) and provides high braking torque as a backup in the event of a hydraulic system failure. The two brakes are independently controlled, so if one fails, the other still ensures reliable braking.
Q: What is the function of the counterbalance valve?
A: The counterbalance valve is a combination valve (check valve + relief valve) installed at the lowering port of the hoisting motor. During normal lowering, hydraulic oil flows freely through the check valve into the motor. If the hydraulic pipeline ruptures, the counterbalance valve automatically locks the lowering circuit, hydraulically locking the motor so the hook cannot drop. The counterbalance valve prevents "runaway lowering" of the hoisting mechanism.
Q: When is the free-fall lowering function used?
A: Free-fall lowering (with the clutch disengaging the drum from the gearbox) is used for pile-driving operations (where the pile hammer free-falls for impact) and for rapid no-load lowering to improve cycle efficiency. Free-fall lowering is permitted only under no-load or light-load conditions (≤30% of rated load) and must be controlled by the operator using the foot brake to regulate lowering speed. It must never be used at rated load.
Q: What are the risks of excessive hydraulic oil temperature in the hoisting mechanism?
A: When hydraulic oil temperature exceeds 90°C: oil viscosity drops significantly, reducing lubrication performance; seal aging accelerates; the oil oxidizes and decomposes, forming sludge; and the volumetric efficiency of the hydraulic system decreases. Control measures include: keeping the radiator surface clean, selecting the appropriate viscosity grade of hydraulic oil (L-HM32 or L-HM46), and allowing the machine to rest between extended heavy-load cycles.
