“The Pro Rigger” by Mike Parnell

As you know in ASME B30.9 SLINGS and other industry documents that highlight sling capacities, there are stated design factors. Also in B30.26 RIGGING HARDWARE which covers shackles, swivel hoist rings, eye bolts, rigging blocks and the like lists design factors between 4 and 5.

The first primary reason is to account for some measurable amount of wear to the sling or component during its lifespan. This wear will reduce its overall minimum breaking force (ultimate strength). This may occur in the form of metal loss in links of a chain sling or in the bow or pin of a shackle. The respective manufacturers have pre-calculated the amount of loss they can live with before calling for the equipment’s removal from service.  Read more…