Lifting Sling Terminology Guide

Safety Terms and Definitions

1. Rated Capacity

The term "Rated Capacity" represents the ratio of the minimum breaking strength divided by the design factor of 5 under the following conditions:

•In a straight pull
•When the sling is new
•Ideal sling conditions
•Ideal test conditions

Expressed as a formula, with a design factor of 5:
Rated Capacity = Minimum breaking strength /5

Catalog rated capacity charts are determined by actual tests. Do not exceed sling rated capacity.

The term "Rated Capacity" does not represent the sling's lifting capacity under all lifting conditions or at any time during the working life of the sling. When calculating a sling working load it is necessary to consider:

  • The increased sling loading from lifting at angles. Refer to sling-to-load angle chart.
  • The loss of sling strength through age, wear, or damage.
  • The added sling loading of acceleration, deceleration and shock.

2. Design Factor

"Design Factor" is the ratio between the sling's minimum breaking strength and the sling's rated capacity. Wear-Flex designs all slings to a minimum design factor of 5.

3. Tolerance

These slings are manufactured to a tolerance of + or - 2% for single and double ply slings and + or - 4% for three and four ply slings.

4. Breaking Strength

The load at which any part of a sling breaks to destruction.

5. Proof Test

A load factor of two (2) times the rated capacity of the sling applied during a testing procedure.

6. Elongation

The measurement of stretch determined as a % of the no-load length. Wear-Flex nylon slings stretch approximately 5-7% at rated capacity and 30-33% at breaking strength. Elongation varies with web and sling construction. Polyester stretches approximately one half as much as nylon.

7. Temperature

The upper use limit for nylon and polyester as a sling material is 194º Fahrenheit (90º Celsius).

8. Ultraviolet Light

Untreated nylon is adversely affected by ultraviolet light exposure. For prolonged exposure to sunlight or other sources of ultraviolet light, slings should be treated or coated.

9. Sharp Edges

Do not use on sharp edges without proper sling protection.