Knowledge of hidden damage is paramount for any safety inspection program.
Fort Dodge, IA (PRWEB) January 29, 2013
Safety inspectors charged with validating the safety of rigging gear should be trained to identify hidden damage to wire rope slings and synthetic slings. Maximum Capacity Media, Fort Dodge, Iowa, has published an article on its website, http://www.craneandrigginghotline.com, on tips to overcome the obstacles of hidden damage due to corrosion and UV damage. In the article, Slingmax® Rigging Solutions discusses products to replace traditional wire rope slings, provide round sling covers to prevent UV light degradation, and improve lifting sling inspections.
Twin-Path® Synthetic Sling
In 1989, a presentation was made on heavy lifting slings to a rigging group at St. John Shipyard in New Brunswick. To make heavy lifts on the dry dock, the shipyard had been using a set of 4-inch diameter by 90 foot long wire rope slings and storing them outside. This subjected the lifting slings to cold, heat, salt air, and rain. After two years, the lifting slings were replaced because of the effects of corrosion from outdoor conditions.
At that time, Slingmax® had a relatively new high-performance fiber Twin-Path® synthetic sling. The benefits explained to the riggers included light weight and ease of handling compared to the heavy wire rope slings. Surprisingly, the shipyard team found the Twin-Path® synthetic slings could be stored inside after use and would not be subjected to the weather. They were willing to spend extra money on Twin-Path® synthetic slings with the same capacity as their 4-inch wire rope slings. The Twin-Path® synthetic slings were significantly less expensive in the long term because they synthetic slings continued working for the shipyard for 15 years.
Covermax® Round Sling Covers
One of the most common synthetic slings is the round sling, which has a strength bearing core inside a protective cover or jacket. Since the late 1970s when the round sling was invented, it was assumed that the round sling cover, no matter the thickness or color, protected the load bearing core from UV degradation because it appears to be opaque. Only recently has it been discovered that UV not only can cause damage to the breaking strength of round slings, but there is a wide variance in the protection levels provided by different round sling covers.
A study of the difference in the protection afforded by various types of round sling covers determines the green Covermax® is thicker than other round sling covers, and therefore, the sling loses negligible strength. Round slings protected by thinner, lighter colored covers lost the most strength.
A simple field test of any cover may indicate the level of UV protection. Hold a flashlight against the cover and see how much light shines through the material. The more light that penetrates the cover, the less UV protection on the round sling.
Check-Fast® Inspection System
A mechanical way to determine “hidden damage” in a round sling is with the Slingmax® Rigging Solutions’ patented Check-Fast® Inspection pre-failure warning indication system. A round sling made with the Check-Fast® Inspection System adds an extra winding of load bearing fiber called a “sacrificial strand,” which is independent of the load bearing core yarns. The ends of this independent strand are equally tensioned among the other load bearing core yarns via a “weak link.” The weak link material has a calculated breaking strength lower than the sling’s core yarn. Also, the weak link degrades faster than the core yarn when exposed to UV light.
If the round sling is exposed to damaging UV rays, the weak link is designed to break before the load bearing core yarn. The weak link is attached to an External Warning Indicator (EWI) cord, which is pulled inside the round sling cover. This system also reacts when the sling is subjected to an overload above its working load limit.
In the course of a lift, if a round sling is severely overloaded or serious degradation has occurred, the Check-Fast® weak link is designed to fail first, before the load bearing core yarns and whip the EWI cord inside the cover with a pop. The patented Check-Fast® Inspection system is also designed to detect damage caused by yarn on yarn abrasion, fatigue, heat and chemical damage.
The Slingmax® website (http://www.slingmax.com) has a video containing a detailed explanation on how the Check-Fast® Inspection System works and a break test.
For more information on Slingmax® Rigging Solutions or to receive a free Riggers Handbook, click here to submit your mailing address or email your complete mailing address to handbook(at)slingmax(dot)com.
About Maximum Capacity Media
Maximum Capacity Media's objective is to deliver information for the selection, maintenance and safe use of cranes, hoists, material handlers and aerial work platforms to the North American construction and industrial marketplaces. Our Its comprehensive and authoritative print magazines include Crane and Rigging Hot Line, Industrial Lift and Hoist and Lift and Access magazines.