A Planning Advisory Notice issued by NATE, The Communications Infrastructure Contractors Association, outlined best safety practices for slings, ropes, harnesses, and hard hats to help technicians identify and prevent environmental exposure and ultraviolet degradation.
In 2017, Brigham Young University conducted a study on webbing strength loss, “Long-Duration Environmental and Blood Effects on Webbing Strength Degradation.” The methodology of the study was simple, they took 6’ sections of nylon webbing and hung them outside for one year in seven separate climates and elevations across North America. Some of the chosen locations were Arapahoe Basin Ski Resort in Colorado, Bishop, California, and Anchorage, Alaska. Two control samples were stored in a climate-controlled environment away from direct sunlight in Columbus, Ohio. At the end of the year all samples were returned and subjected to a uniform strength test.
The study identified four key factors for environmental degradation: wind, temperature, precipitation, and UV radiation. The result of the test determined webbing exposed to the elements for one year led to an average strength loss of 27.7 percent. As a reminder, this equipment was not used for its intended purpose but simply exposed to the elements. Zero percent of this strength loss was due to any usage factors. Additionally, safety harness webbing, rope, and slings are typically comprised of nylon, polyester, or a combination of the two. Since these materials will experience comparable degradation from exposure to wind, temperature, precipitation, and UV radiation. The study was designed to provide guidance for equipment subjected to these types of environmental exposure.
Wind, temperature, and precipitation combined for roughly 51 percent of the total average strength loss from the study. Barring a significant weather event, wind itself is not a strong factor in the degradation of nylon webbing. However, wind does open the potential for airborne particles and dirt to attach to equipment and the opportunity for slings and rope to repeatedly impact the structure or surface that it is attached to. This impact abrasion can lead to signs of wear, fraying, breaks, loosened/pulled threads, or cuts.
The impact of temperature on webbing strength is theorized to be relatively minimal (barring high extremes that will burn or glaze) but it is still important to take precautions. Inspection must be conducted to identify glazing, discoloration, or hard/soft sections. Rain and other precipitation also did not significantly degrade the rope compared to other sources. Though, climates with high airborne salt content could cause damage to harness hardware or rope terminations. It’s important to inspect buckles, attachment points, and hardware for proper function and for signs of corrosion, pitting, rust, cracks, or breaks.
Roughly 41 percent of the total average strength loss was attributed to UV radiation. The most notable negative impacts of UV radiation included the loss of tensile strength, loss of flexibility, and decreased elasticity. These findings were confirmed by the lesser degradation of samples in Canada and Alaska due to the shallower angle of the sun for many parts of the year. Further, large portions of the day in these areas would have cast the webbing in the shade. Fortunately, UV degradation is relatively easy to identify. Inspect for significant fading, stiffness, lack of pliability, or a fuzzy texture along the length of webbing or rope.
About 5.5 percent of the total strength loss was attributed to the age of the nylon webbing. This places emphasis on tracking the date of manufacture and inspecting and documenting the date equipment is put into service. If the equipment is not marked with a date of manufacture, it becomes impossible to know the age of the product unless there is a log of when it was put into service. For additional information, visit the link below to see OSHA’s Guidance on safe sling usage:
To put all of these strength losses in context, consider a nylon webbing sling with a breaking strength of 5,000 lbs. Over the course of this study, this sling will have experienced an average of 27.7 percent overall strength degradation, reducing its breaking strength to 3,615 lbs. (loss of 1,385 lbs.). Contributors to the loss are wind, temperature, and precipitation will be responsible for 710 lbs. of strength loss, UV radiation 567.5 lbs., age 75 lbs., and some minor miscellaneous factors 32.5 lbs.
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