Dan Sullivan wrote:There was a discussion about the shelf life of nylon products on the last DB. I believe 5 years was the number given, which would be a manufacturing or sellers shelf life.
Yes, it's true that manufacturers often suggest a rather short shelf life - both to sell more product and to minimize their liability. Consequently many rescue squads wrote SOPs requiring retirement of rope and webbing after 5 years, regardless of use or condition.
Studies, however, have shown that shelf life and even use life can be much longer than that.
CMC Rescue
Technical Report #1
November 1998, CMC Rescue, Inc.
ROPE LIFE: When to Retire Your Rescue Lifeline
According to DuPont, the shelf life of their Nylon T707 (such as Wellington Commercial Cordage uses to make CMC Rescue Lifeline) should be indefinite unless altered by excessive exposure to certain chemicals, heat and sunlight. In the safety field, 1 to 2 years of use and 5 years of storage are recommended for synthetic ropes. (Ellis, J. Nigel. Introduction to Fall Safety. Des Plaines, IL: American Society of Safety Engineers; 1998.)
In June of 1990, Wellington Commercial Cordage tested samples of Rhino Rescue Rope stored for seven years by Bridger Coal's mine rescue team in Wyoming. The sample was 1/2-inch (12.7 mm) diameter, low-stretch kernmantle rope. The manufacturer's new rope tensile strength rating was 9,000 pounds (40.34 kN). For comparison, the independent lab tests on new Rhino Rescue Rope in 1983 averaged 10,495 pounds (47.04 kN). The test results from the Bridger Coal samples suggest minimal strength loss when the rope is properly stored.
Break #1 11,200 pounds (50.20 kN)
Break #2 10,600 pounds (47.51 kN)
Break #3 11,000 pounds (49.30 kN)
Average 10,933 pounds (49.00 kN)
Section 5.2.2 of ASTM F 1740 - 96 Guide for Inspection of Nylon, Polyester, or Nylon/Polyester Blend, or Both Kernmantle Rope, recommends ten years as a maximum rope life. How a rope is used and stored has a greater effect on rope life than any other factor.
[ASTM #F-1740 - Standard Guide for Inspection of Nylon, Polyester, or Nylon/Polyester Blend Kernmantle Rope says: Retire any rope which is greater than 10 years old, regardless of rope history and usage because there is no universally agreed upon “shelf-lifeâ€