Questions Over Web Slings Four Years in the Making

Lucy Perry

June 14, 2006 — Does the crane construction industry really need quantitative rejection criteria for web slings? Apparently, the question is still on the table. Pose it to the Web Sling & Tie Down Association (WSTDA), and it will tell you it's taking no action on the issue at the moment. Ask one industry consultant, and he'll tell you sitting on this issue could come back to bite slingmakers.

 

The issue came up in 2002 when a sling user wrote to industry consultant Mike Parnell, of Industrial Training International, asking for clarification on OSHA's Title 29 requirement. Currently, OSHA regulations and ASME standards provide no specifics on the amount of damage a synthetic web sling can incur and still be used safely. Web sling users are asked to continue adhering to existing inspection criteria language.

 

That language calls for sling removal upon observation of cuts, tears, punctures, snags, crushing, abrasion, ultraviolet ray damage, missing or illegible identification, chemical or heat damage, knots, worn or broken stitching, damaged or corroded end fittings, “or other evidence which calls into question the continued use of the sling.”

 

One of the points of confusion among users is Title 29 could be construed as calling for zero tolerance for any wear or minor defects in synthetic web slings. “Such requirements are largely unattainable as even first time use of new web slings on cargo can result in abrasions, cuts, tears or the like, merely due to cargo shifting during transport,” one source states.

 

Parnell reiterated the sling user's observations. “This cosmetic change may have virtually no impact on the web sling's overall tensile strength; however in the eyes of a sling inspector the sling would meet the current published removal language,” he says.

 

In the interest of the industry as a whole, the issue was turned over to the WSTDA with the request that it develop a recommended guideline that would identify quantitative criteria for the removal of synthetic web slings. WSTDA, in turn, asked that the Associated Wire Rope Fabricators (AWRF) conduct a series of destructive tests on slings subjected to edge and surface cuts. According to Parnell, the AWRF Testing Committee found there was not a definable value range of damage that could repeatedly result in a specific amount of loss.

 

“In essence, the webbing responds with too many variables to allow the establishment of specific loss of cross-section which repeatedly corresponds to a specific loss of tensile strength,” states Parnell's correspondence.

 

WSTDA notified AWRF it would take no action for now, and sent a letter back to Parnell last December stating that the Web Sling Technical Committee is “not in a position to issue removal from service criteria.”

 

The letter, dated last December, stated the association's position is that “slings must be removed from service if any damage is detected.” WSTDA further stated it would pursue the issue in the future and keep Parnell apprised of its progress. Contacted at press time for this column, WSTDA reserved comment until after publication.

 

One suggestion is to adopt wording similar to the Transport Canada Marine Safety standard in the document “Wear Standards for Cargo Gear.” The standard categorizes damage relative to thickness or sling surface area, offers service rules based on safety factors, and provides acceptable wear limits based on edge damage, abrasion, local damage, and reasonable combinations of those.  

 

If, as Parnell says, “there is no value to the web sling manufacturers to open themselves up to litigation” over possible misinterpretation of a vaguely worded standard, then slingmakers may find they have everything to lose and nothing to gain by sitting on more measurable standards for sling rejection.