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Electro-Voice® EVA Series User Manual 25
6.0 Rigging-Strength Ratings and Safety Factors
6.1 Working-Load Limit and Safety Factor Definitions
The structural ratings for all of the EVA rigging components and complete loudspeaker systems are based
on test results in which parts were stressed to failure. Manufacturers typically present the structural-
strength ratings of mechanical components or systems as either the working-load limit (WLL) or the ulti-
mate-break strength. Electro-Voice chooses to present the structural-load ratings of the EVA loudspeaker
systems as the working-load limit. The working-load-limit rating represents the maximum load that should
ever be applied to a mechanical component or system.
THE USER SHOULD NEVER APPLY A LOAD THAT EXCEEDS THE WORKING-LOAD LIMITS
OF ANY OF THE RIGGING COMPONENTS OR COMPLETE LOUDSPEAKER SYSTEMS DE-
SCRIBED IN THIS MANUAL.
The working-load limits for the EVA 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 working-load limit, where the ultimate-break strength represents the
force at which a part will structurally fail. For example, if a part has a working-load limit of 1,000 lb (454
kg), it would not structurally fail until a force of at least 8,000 lb (3,629 kg) was applied, based on an 8:1
safety factor. However, the user should never apply a load to that part that exceeds 1,000 lb (454 kg).
The safety factor provides a margin of safety above the working-load limit to accommodate normal dynam-
ic loading and normal wear.
CAUTIONS for Working-Load Limits and Safety Factors
The working-load limits defined by the manufacturer of any rigging component should never be exceeded.
Electro-Voice bases the working-load limits of its EVA products on a minimum of an 8:1 safety factor.
Other manufacturers of rigging components may base their working-load limits on safety factors other
than 8:1. For example, 5:1 safety factors are fairly common amongst rigging manufacturers because many
regulatory agencies call for a minimum safety factor of 5:1.
When an EVA loudspeaker system is installed where local regulations only require a safety factor of 5:1,
Electro-Voice insists that the working-load limits of the EVA rigging never be exceeded and that an 8:1
safety factor be maintained for the EVA loudspeakers.
The user is cautioned that some local regulations may require safety factors higher than 8:1. In that cir-
cumstance, Electro-Voice insists that the user maintain the higher safety factor as required by the local
regulations throughout the entire EVA installation. It is the responsibility of the user to make sure that any
EVA installation meets all applicable local, state or federal safety regulations.