[RIGGER’S CORNER]
IS IT TENSILE STRENGTH? Or Working Load Limit?
BY: JANE BROWE, INDUSTRIAL WIRE ROPE SUPPLY COMPANY, INC.
It’s rare for a week to go by here without discussions about tensile strength or working load limit. We take it for granted that most people in our industry know there is a difference in the meaning of these terms.
Yet, these terms and others are highly interrelated, and we thought an overview of them on one page might be a helpful reference. For those who want to dive deeper into the definitions and how they apply on the job, we’re also providing links to sources with additional information.
TENSILE STRENGTH Let’s start with Tensile Strength. As we described in a post from 2017, “Tensile strength is a measurement of the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. Te tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking.” In our immediate world, tensile strength is the force
required to break the ropes we offer. Tensile strength is determined by testing. Obviously, it is different for every type of rope, being a function of the material and construction of each type.
Although tensile strength is a definitive quantity measuring the force required to break a rope, working load limit is a measure that takes a wide range of variables into account. And always, the tensile strength of a material is greater than the recommended working load limit.
WORKING LOAD LIMIT Te working load limit provides consideration for factors such as the abrasion, friction and rubbing the rope is subjected to, the variance in temperature extremes it is exposed to, harmful substances that may come into contact with it, age, and even knots in the rope. Working load limit is defined as “the maximum load which should ever be applied to the product, even when the product is new and when the load is uniformly applied”.
80 JANUARY–FEBRUARY 2020 WIRE ROPE EXCHANGE
Working load limit is always a fraction of tensile strength, allowing for a generous margin of safety. For wire ropes, it’s common for the working load limit to be set at 20% of tensile strength. However, you generally don’t have to be concerned about doing the math on your own. Rope manufacturers typically mark the working load limit on the products, so the information should be readily available to you. Te Wire Rope User’s Handbook (from Union Rope,
A WireCo WorldGroup Brand) is a great resource for information about rope materials, construction and strength. You can find that at this link:
www.unionrope.com/ technical-support/wire-rope-basics It includes a section beginning on page 30 on “how to extend rope service life”. Below are just some of the factors to consider:
• the manner in which you install and “break in” your new rope
• the operating technique and work habits of the machine operators
• physical maintenance of the rope throughout its service life
• physical maintenance of the system in which your rope operates
If you ever have questions about working load limit or other safety issues related to your industrial wire rope, we’re here to answer them. y
Industrial Wire Rope Supply Company is a family-owned business with main offices in Cincinnati and a branch office in St. Charles, Missouri. Tey provide Wire Rope, Wire Rope Fittings, Fiber Rope, Chain, Nylon Slings, and Wire Rope Slings worldwide. Learn more at
www.industrialrope.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84
