SWL, WLL, and Rated Capacity are terms used in lifting and rigging to specify load limits, but they have distinct meanings and applications, with some terms being replaced over time for clarity and safety.

💡 Safe Working Load (SWL)

  • SWL stands for Safe Working Load and was historically used to indicate the maximum load that lifting equipment could safely lift, lower, or suspend under normal operating conditions.
  • It was calculated by dividing the equipment’s Minimum Breaking Load (MBL) by a safety factor, typically ranging from 4 to 6, or higher if failure risk to life existed.
  • However, SWL is now considered an outdated term and has been replaced because it implied a guarantee of safety, which is legally problematic and ambiguous in risk management.
  • SWL is no longer used in modern lifting standards and has been replaced by WLL for equipment below the crane hook and Rated Capacity for cranes, hoists, and winches.

💡 Working Load Limit (WLL)

  • WLL means Working Load Limit and is the maximum load that lifting equipment such as chains, hooks, slings, or ropes is designed to raise, lower, or suspend.
  • It is calculated by the manufacturer based on the equipment’s breaking strength (Minimum Breaking Load) divided by a factor of safety.
  • Unlike SWL, WLL indicates a limit rather than a guaranteed safe load, reflecting the maximum load under ideal conditions.
  • WLL is specific to the equipment below the crane hook and is used to ensure that the equipment is not overloaded, considering factors such as wear, damage, and environmental effects.
  • The WLL can vary depending on the configuration and use, for example, the angle of sling legs affects the WLL of a sling assembly.
  • WLL is the preferred and current term for specifying load limits on lifting accessories and below-hook equipment.

💡 Rated Capacity (also known as Maximum Rated Capacity – MRC)

  • Rated Capacity refers to the maximum gross load that a crane, hoist, or winch can lift in a particular working configuration and condition.
  • It includes the weight of attachments, spreader beams, or lifting devices below the crane hook.
  • Rated Capacity has replaced the term SWL for cranes, hoists, and winches due to the legal and safety implications of the word “safe.”
  • It is often called the Manufacturer’s Rated Capacity (MRC) or Maximum Rated Capacity to avoid confusion with maximum gross load.
  • Rated Capacity is a broader term than WLL, applying to the entire lifting machine and its configuration rather than just the lifting accessories below the hook.

In conclusion, SWL is an older term largely replaced by WLL for lifting accessories and Rated Capacity for cranes and hoists. WLL defines the maximum load limit for equipment below the hook, while Rated Capacity defines the maximum load for the lifting machine and its attachments. Respecting these limits ensures safe lifting operations.