Overview
ISO 4305:2014 - Mobile cranes - Determination of stability defines how to verify the stability of mobile cranes by calculation. It applies to cranes mounted on wheels (tyres) or crawlers, with or without outriggers (excluding loader cranes), operating on a firm, level surface (up to 1% gradient). The standard sets required safety margins, loading factors, tipping-angle criteria and procedures to ensure stability-limited rated capacities are safe under practical operating conditions.
Key topics and requirements
- Scope and definitions: Applies to mobile cranes as defined in ISO 4306-2; includes terms such as fixed-length boom, telescoping boom, fly jib and tipping angle.
- Stability calculations: Establishes how to calculate overturning and stabilizing moments; all dead loads, counterweights and accessories must be considered in their least-favourable positions.
- Load factors (Table 1): Simulates dynamic effects during controlled operation. Examples:
- On outriggers/crawlers: Applied load = 1.25·P + 0.1·F
- On wheels (tyres): Applied load = 1.33·P + 0.1·F
- Higher factors apply for travel speeds > 0.4 m/s
(P = rated capacity; F = boom/fly-jib mass effect per ISO 4310.)
- Wind and dynamic effects (Table 2): Requires wind load S·W (calculated per ISO 4302) and inertia forces D for motions. Partial safety factor S varies by wind application (e.g., S = 1.2 for wind on structure).
- Tipping-angle minima (Table 3): Specifies minimum tipping angles by configuration (e.g., 4.0° on outriggers/crawlers; up to 6.0° for wheels at higher travel speeds). Slopes >1% must be accounted for in calculations and load charts.
- Backward stability: Limits on counterweighting and minimum support loads on tipping lines - typically not less than 15% of total mass in normal configurations and as low as 5% with boom removed, with manufacturer visible cautions where limits are not met.
- Out-of-service wind: Manufacturers must provide precautions and working limits when crane is out of service.
Applications and users
ISO 4305:2014 is used by:
- Crane manufacturers and designers to verify rated capacities and specify counterweights, outriggers and load charts.
- Structural and safety engineers performing stability calculations and risk assessments.
- Certification bodies, test laboratories and conformity assessors applying ISO 4310 test methods.
- Fleet managers, operators and site safety officers who rely on load charts, operator cautions and wind-related operating limits.
Benefits include consistent stability verification, clearer manufacturer guidance (counterweight and outrigger use), and improved safety when planning lifts under wind or dynamic conditions.
Related standards
Keywords: ISO 4305:2014, mobile cranes, stability calculation, tipping angle, outriggers, wind load, crawler-mounted, wheel-mounted, crane manufacturer, load chart, counterweight.
