GB/T 22437.4-2009 is Part 4 of the crane load and load combination series, establishing load classification and combination calculation rules tailored to the load characteristics and operating conditions of jib cranes. Unlike overhead and gantry cranes, jib cranes operate with luffing motion and are significantly affected by the dead weight of the boom. This article provides a systematic interpretation of the standard's core content.

Standard Scope and Jib Crane Characteristics

GB/T 22437.4-2009 applies to jib-type cranes, primarily including portal cranes, mast cranes, floating cranes, deck cranes, cantilever cranes, and railway cranes. The structural characteristic of jib cranes is that the boom serves as the primary load-bearing member, rotating about the slewing center, with loads transmitted through the boom to the slewing bearing and the base. Unlike overhead and gantry cranes, load analysis for jib cranes must account for: the variation of load distribution at different working radii and slewing angles, the additional loads imposed on floating cranes by vessel motion (pitch, roll, and heave), and the effect of the boom's stowed position on wind loads during non-working conditions.

Load Classification for Jib Cranes

The standard classifies loads into main loads, additional loads, and special loads:

Main loads (P) — including dead weight (all fixed components such as the boom, hoisting mechanism, slewing mechanism, counterweight, and operator cab), lifting load (rated lifting capacity plus the lifting spreader and suspended wire rope), slewing inertia load (horizontal inertia forces generated by masses during slewing start and braking), and luffing inertia load (forces from changes in the horizontal component of mass during boom luffing). For portal cranes, the dead weight of the portal frame system accounts for a significant share of the total dead weight (approximately 30%–40%).

Additional loads (A) — including wind load (working condition calculated for wind force 7; storm condition based on the maximum wind speed with a 50-year return period), temperature load (significant when temperature differentials exist in the steel structure, particularly for portal cranes exposed to sun and shade in open stockyards), and seawater load (additional wave impact, hydrostatic pressure, and weight gain from marine growth for floating cranes).

Special loads (S) — including test loads (1.25 times static load, 1.1 times dynamic load), collision loads, erection and dismantling loads, and for floating cranes, vessel inclination loads (static inclination moment at roll ≤5° and pitch ≤2°) and hull motion acceleration loads (heave acceleration up to 0.2–0.5g).

Load Combinations and Operating Conditions

The standard defines three basic operating conditions: Condition A (normal operation without wind, safety factor n≥1.22), Condition B (operation with wind, safety factor n≥1.22), and Condition C (storm, non-working, safety factor n≥1.10). Unlike overhead and gantry cranes and mobile cranes, jib cranes under Condition B require separate calculation of the most unfavorable load combination for each boom position — minimum radius, intermediate radius, and maximum radius. This is because the bending moment generated by the boom's dead weight changes direction at different working radii, so the critical load position must be verified at each radius individually.

For portal cranes, the standard further requires verification under Conditions A and B with the boom positioned both directly facing the portal frame opening (the direction of lower portal frame stiffness) and perpendicular to the portal frame opening.

Kelude Heavy Industry: Overhead & Gantry Crane Solutions

Kelude Heavy Industry is a professional manufacturer of overhead cranes, gantry cranes, and electric hoists. We provide comprehensive material handling solutions for industrial applications, with a strong focus on safety, reliability, and long service life.

Overhead Cranes Built for Heavy-Duty Performance

Our overhead crane range includes single-girder and double-girder designs, available in capacities from 1 ton to 100 tons. These cranes are engineered for demanding workshops, warehouses, and production lines, offering smooth operation and precise load control. All major components are sourced from reputable brands to ensure consistent quality and minimal maintenance.

Gantry Cranes for Flexible Outdoor & Indoor Use

Kelude gantry cranes are designed for versatility, with options for rail-mounted and rubber-tired configurations. They are ideal for loading docks, storage yards, and prefabricated construction sites. Capacities range from 5 tons to 300 tons, with spans customized to your site requirements. Our gantry cranes feature robust steel structures and advanced safety systems, including overload protection and anti-sway technology.

Electric Hoists & Trolleys for Precise Lifting

We offer a complete line of electric wire rope hoists and chain hoists, with lifting capacities from 0.5 tons to 50 tons. Our hoists are available with fixed or motorized trolleys, and can be integrated into new or existing crane systems. Features include dual-speed motors, low-headroom designs, and optional explosion-proof configurations for hazardous environments.

Custom Engineered Solutions for Specialized Applications

Beyond standard models, Kelude specializes in custom-engineered cranes for unique industrial processes. This includes low-headroom cranes for tight spaces, explosion-proof cranes for chemical plants, and heavy-capacity cranes for steel mills and power stations. Our engineering team works closely with you to develop a solution that meets your exact load, span, and duty cycle specifications.

Global Standards & Quality Assurance

All Kelude cranes are designed and manufactured in compliance with international standards, including ISO 4301 for crane classification and IEC 60204-32 for electrical equipment. Our quality management system is certified, and every crane undergoes rigorous testing before delivery. We provide comprehensive documentation, including load charts, wiring diagrams, and maintenance manuals.

Comprehensive After-Sales Support & Spare Parts

We are committed to long-term customer satisfaction. Our after-sales service includes on-site installation supervision, operator training, and prompt technical support. A full range of spare parts is available for fast delivery, ensuring minimal downtime for your operations. Our service network covers major industrial regions across the US and Europe.

Frequently Asked Questions

Q: What is the typical lead time for a standard overhead crane?
A: For standard single-girder cranes up to 10 tons, lead time is typically 30-45 days. Double-girder and custom-engineered cranes may require 60-90 days depending on complexity and current production schedule.

Q: Do you provide installation services?
A: Yes, we offer professional installation services either by our own technicians or through our certified local partners. We also provide detailed installation drawings and video guidance for self-installation if preferred.

Q: Can you customize the crane span and lifting height?
A: Absolutely. Span and lifting height are customized based on your building dimensions and operational needs. Our engineers will conduct a site survey or work from your architectural drawings to determine the optimal configuration.

Q: What is your warranty policy?
A: We offer a standard 12-month warranty on all crane components, covering manufacturing defects. Extended warranty options are available upon request. Our after-sales team is available 24/7 for emergency technical support.

Q: Do you supply cranes that meet ATEX or explosion-proof requirements?
A: Yes, we manufacture explosion-proof cranes and hoists certified for use in hazardous areas, compliant with ATEX and IECEx standards. Please specify your zone classification and gas/dust group when requesting a quote.

Q: How do I request a quotation?
A: Please send your inquiry with the following details: capacity, span, lifting height, duty cycle, power supply, and any specific requirements. Our sales team will respond within 24 hours with a detailed quotation and technical proposal.

Special Provisions for Floating Cranes

A: Load analysis for floating cranes is the most complex, and the standard specifically adds considerations for vessel motion-induced loads. During operation, the hull of a floating crane experiences roll, pitch, and heave motions due to wave action. Roll periods range from approximately 6 to 12 seconds, with amplitudes reaching 5° to 10°; pitch periods range from 4 to 8 seconds, with amplitudes of 2° to 5°; heave periods align with wave periods (approximately 5 to 10 seconds), with amplitudes of 0.5 to 2 meters. These motions generate additional inertia loads on the crane, requiring the dynamic load factor for the lifting load to be multiplied by an amplification factor of 1.2 to 1.5. The anti-overturning stability of floating cranes is verified in accordance with marine stability specifications, accounting for the combined effects of wind, waves, and the suspended load. Operations shall be stopped and the boom secured when wave heights exceed the design limit, typically 1.5 to 2.5 meters. Kelude Heavy Industry rigorously applies this standard to load combination analysis for its portal base and floating cranes supplied to shipyards and ports, ensuring structural safety under all operating conditions.

Jib Crane Load Combination Comparison Table

The comparison table below outlines the core parameter configurations for jib crane load combinations, serving as a reference for selection and operational personnel.

Frequently Asked Questions