WORKING LOAD LIMITS OF SLINGS
Observing the WLL is a critical safety aspect in all overhead lifting operations. Exceeding the WLL of a chain sling can cause chain failure and, consequently serious injury. To avoid hazards, consider:
- Always accurately determine the load, force, or weight that is to be lifted or carried with the chain sling.
- Do not attempt to use a chain sling without complete and accurate knowledge of the force or weight carried by each part of the sling. Even if the sling as a whole may be within the WLL, non-uniform center of gravity locations can result in unbalanced loading conditions.
- Include all applicable capacity reduction factors when determining the WLL. These factors can substantially reduce the ability of the chain sling to carry a load safely.
- Do not use slings at angles of less than 30 degrees, as measured from the horizontal plane.
- Chemically active environments can reduce the strength and WLL of an alloy steel chain sling, or even make the sling unusable.
- Shock or impact loading can substantially increase the chain sling's force to a level well beyond the WLL.
- Consult an engineer for approval prior to performing a lifting application if the load's weight or chain sling's WLL is unknown.
INSPECTION AND MAINTENANCE
In order to ensure a safe operation of chain slings, inspection and maintenance are very important. Excessive wear of any single component can result in a failure of the sling and serious injury.
Proper safety practices should be followed, including never walking under a suspended load.
In order to avoid this hazard, keep the following points in mind:
- Inspect slings in accordance with federal OSHAregulations and ASME B30.9 standards
- Perform and record frequent and periodic inspections of chain slings
- Prior to use, order an inspection of all new, altered, modified, or repaired chain slings to verify compliance with ASME B30.9
- Visually inspect chain slings for damage before use each day
- Proper measurements using precision instruments of each link and each component should be performed to provide a benchmark for allowable tolerances
- Written records containing the most recent periodic inspection should be maintained by the owner or user of the chain sling.
— Michael W. Uhrenbacher is the general manager of Pewag Inc., Burr Ridge, Ill.Safety checklist
- Ensure all slings have identification and warning tags
- Maintain records, including test certifications, drawings, instructions, warnings, and maintenance records of each chain sling
- Ensure that personnel performing overhead lifting applications are properly trained
- Ensure that slings are inspected before use
- Establish an inspection and maintenance plan in accordance with ASME
- Perform sizing and load calculations to ensure loads remain within working load limits
- Review and approve lifting applications to ensure loads remain within working load limits and that lifts remain stable
- Familiarize yourself with federal OSHA requirements and ASME B30.9 standards.
- Choosing the right chain
- Determine the maximum load to be lifted
- Determine the type of slings needed (single, double, etc.)
- Estimate the proper angle between the leg of the sling and the load
- Select the proper fittings (hooks, master rings, etc.)
- Determine the overall reach (measured from the bearing point on the master link to bearing point of fitting)
- Choose a chain size that meets your required work load, angles, and reduction factor
- Choose1222222 grade, type, and finish of steel that meets your requirements.