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Working Load Limit and Safety-Factor Definitions
Electro-Voice WLL
The structural ratings for all of the EVU rigging components and complete loudspeaker systems are based on test results in
which parts were stressed to failure (optional methods of rigging have not been tested by our facility). Manufacturers typically
present the structural-strength ratings of mechanical components or systems as either the WLL or the ultimate-break strength.
Electro-Voice chooses to present the structural-load ratings of the EVU loudspeaker systems as the WLL. The WLL rating
represents the maximum load that can be applied to a mechanical component or system.
WARNING:
The user should never apply loads that exceed the WLL of any of the rigging components or complete
loudspeaker systems described in the manual.
Factor of Safety
The WLL for the EVU rigging components and complete loudspeaker systems described in this manual are based on a
minimum 8:1 safety factor. The safety factor is defined as the ratio of the ultimate break strength divided by the WLL, where
the ultimate break strength represents the force at which a part fails structurally.
For example, if a part has a WLL of 35lb. (15.8kg.), it would not structurally fail until a force of at least 280lb. (127kg.) was
applied, based on an 8:1 safety factor.
WARNING:
The user should never apply a load to that part that exceeds the value listed in this manual for these products.
The safety factor provides a margin of safety above the WLL to accommodate normal dynamic loading and
normal wear.
WARNING:
For WLL and Safety Factors, the WLL defined by the manufacturer of any rigging component should never
be exceeded. Electro-Voice bases the WLL of its EVU products on a minimum of an 8:1 safety factor. Other
manufacturers of rigging components may base their WLL on safety factors other than 8:1. For example, 5:1
safety factors are fairly common among rigging manufacturers because many regulatory agencies call for a
minimum safety factor of 5:1.
Working Load Limits and Safety Notices
CHAPTER 3
25
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