CRANE CRITIQUE
CRANE RIGGING ACCIDENTS WHY DO THEY EVER HAPPEN?
A monthly crane and rigging informative column for all personnel directly or indirectly involved with crane safety. Each month we will attempt to explain a different technical issue pertaining to crane operations here on Guam, addressing the sometimes over-looked or misunderstood topics by management and operators alike. By Dave Barnhouse
We have all witnessed an accident or near-miss involving a crane lift while using rigging gear. Crane operators must pass rigorous written as well as practical tests before being found competent to operate a particular type of crane. Riggers must also prove to be competent by testing. All rigging gear has a safety factor of 5:1, meaning the safe working load, or SWL, is one fifth the actual tested breaking strength. With these requirements one would think there should never be an accident caused by a rigging failure. Unfortunately there are rigging failure accidents and most likely more than most supervisors are aware of. Rigging accidents, most of the times, can be avoided provided one is vigilant and follows the best safety practices. From shipyards to construction sites, rigging plays a major role in all kinds of industrial and commercial activities. Without rigging, one cannot imagine moving heavy loads easily and quickly. No matter how much a load is over-sized and overweight, rigging services make it possible to relocate heavy loads in the most secured manner. In spite of following safety precautions and OSHA guidelines, lifting rigging accidents do occur at workplaces and result in severe injuries or property damage. Two major reasons I believe rigging accidents exist: ignorance and the ‘don’t care’ attitude. Both can and must be addressed with training and supervision. Most of my students attending a rigging class have years of experience rigging for your cranes on your job sites. Yet they are completely unaware of some very important issues regarding safe rigging practice, namely inspections and rating of gear, sling angle tension factors, proper hitch usage, and the importance of softener use on sharp pick-points.
26 | MAY2015
The 'soft sling' synthetic sling or round sling, is very much misused. We use the soft sling when lifting heavy parts to help safeguard an abrasion on the connecting part of machinery, it has a more flexible wrap on tension, unlike chain or wire rope, which tend to cut or bite in more aggressively regarding its lifting weight. The problem with riggers using soft slings is they use little or no protection on the connecting parts. Softeners are used not only to protect sling from cuts but also slippage at pick-points. Smaller sling angles will exacerbate this condition. Using flat slings of more than 4" width for angular lifts is dangerous, particularly on flat base sharp cornered materials, as the load at each pick point is not
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equally distributed upon the full width but is concentrated more at the outer edges of the sling which can result in tearing apart the sling. It is recommended that in such cases the slings should be used vertically. In addition correct type of shackles must be used for flat slings as standard types are not suitable due to crimping or bunching. And who has not witnessed synthetic slings placed over the blades of a fork truck? Although the blades do not appear to be sharp, effectively the angle of the sling is 90 degrees off the blade, creating a cutting strain. If your company uses a forklift or telehandler for lifting suspended loads a hook attachment must be used. Also the operator is now more
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