Differences Between Working Load Limit and Safe Working Load
A clear understanding of WLL and SWL is essential for everyone involved in lifting and hoisting operations. Because these terms directly influence safety, compliance and decision-making in lifting plans, Cranes for You includes this topic in the Knowledge Centre to help organisations prevent incidents and work according to Dutch/EU standards.
What Are WLL and SWL?
The Working Load Limit (WLL) is the maximum load a component, lifting accessory or machine is designed and certified to handle under normal conditions.
The Safe Working Load (SWL) is an older, derived value historically used to indicate a permissible load, often based on an additional safety factor applied by the operator or organisation rather than the manufacturer.
Why WLL Replaced SWL
Modern standards (EN, ISO, OSHA, ASME) have phased out the term Safe Working Load (SWL) because it was ambiguous and the word “safe” could be misleading. It suggested that operators or organisations could determine an extra safety margin themselves, leading to inconsistent interpretations.
Working Load Limit (WLL) replaced SWL because it provides a precise, manufacturer-defined maximum load under specified conditions. WLL is:
- calculated and certified by the manufacturer
- traceable and verifiable
- aligned with conformity assessment and CE-marking requirements
- objective and not open to interpretation
- the standard terminology used across modern ISO and OSHA-related guidance
As a result, all contemporary lifting operations, lifting plans, and hoisting accessories must use WLL as the reference limit.
Practical Relevance in Lifting Operations
For the Appointed Person and all personnel involved in lifting operations:
- All calculations in lifting plans must be based on WLL, not SWL
- Lifting accessories must display WLL on markings and certificates
- Risk assessments rely on the correct interpretation of WLL
- SWL may appear in older documentation but is no longer acceptable for compliance
Official Source
1. EU Machinery Directive (2006/42/EC)
The Machinery Directive requires manufacturers to define and declare the maximum permissible load of lifting machinery and accessories. This declared value — the Working Load Limit (WLL) — forms the legal and technical basis for safe use within the EU. The directive explicitly requires that equipment must not be operated beyond its declared limits and that these limits must be clearly marked and verifiable.
2. EN Standards (European Norms)
Several harmonised EN standards specify how WLL must be determined, verified, marked and used in lifting operations.
3. ASME B30 Series (United States)
Although focused on the US market, ASME B30 standards use comparable concepts to WLL, providing requirements for rated loads, marking, testing and safe use. They contribute to global industry alignment replacing older concepts such as SWL with precise, defined load limits.
Related Knowledge Articles
- Crane Stability & Ground Pressure: CICA & CANZ Guidance Note
- Guidance on Ground Conditions for Construction Plant
- Empowering Safety – The Appointed Person and His Role in Your Workplace
- Guide to the Safe Use of Overhead, Gantry & Jib Cranes
Ready to Improve Safety and Efficiency?
Understanding WLL is a core requirement for safe lifting operations.
If your team needs guidance on correct capacity evaluation, lift planning or compliance, our specialists are ready to help—get in touch or download the full document on this page.
