wire rope breaking strength vs working load pricelist

It’s rare for a week to go by here at Industrial Wire Rope 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.

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. The 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.

The 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”.

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.

For use in lifting and rigging, securement, and general purpose, the 6x19 wire rope class comprises either a wire rope core or a fiber core. The wire rope core is its own wire rope construction, most commonly 7x7. This is known as IWRC (Interdependent Wire Rope Core), meaning it moves independent to the outer strands. It’s mostly used in winch-type applications. Within the fiber core wire rope, the fiber core is made of natural or synthetic fiber, which can provide excellent flexibility and resistance to contact pressure, and can store lubrication to reduce the friction between wire strands effectively.

The bright class of industrial wire rope is produced without a surface treatment—making the rope less likely to untwist or kink while giving it a stronger crush resistance than lay ropes. Generally, they are fully lubricated to protect the rope from rust and corrosion.

Galvanized wire rope (steel) features a compressed zinc coating for providing excellent corrosion resistance. With higher break strength, yet lower price than stainless steel wire rope, galvanized steel wire rope is widely used in general engineering applications such as winches and security ropes.

The 6x19 wire rope class is made up of six strands of between 16 and 26 wires per strand for additional wire rope strength and durability, with a maximum breaking strength of 69 tons. The 6x19 features IPS (Improved Plowed Steel), EIPS (Extra Improved Plowed Steel), or EEIPS (Extra Extra Improved Plowed Steel) grade wire rope. Also available in USA-made.

Rigging and safety gear purchased from Westech Rigging Supply should be used in strict accordance with all industry and OSHA standards. At no time should rigging or safety gear be used beyond its certified load ratings (aka Working Load Limits). Normal wear and tear should be expected with use of rigging and safety gear; therefore, all gear should be thoroughly inspected before each and every use. Worn or unsafe rigging and safety gear should never be used.

In the shipping industry, items like winch straps and ratchet straps use two common measuring metrics. One of them is the working load limit, while the other is the strap’s break strength. At first glance, it’s understandable why some people might mix the two up. They kind of mean the same thing, don’t they? In this article, we’ll look at break strength vs. working load limit, explaining the differences and why those differences are so important.

We’ll start with break strength since this term is more self-explanatory than the other. Put simply, the break strength of a piece of rigging is the amount of weight that would cause the weakest part of the rigging to fail. Ideally, you’ll never actually test a rigging’s break strength, as the weight of the loads they’ll carry will usually be much lower than this limit.

If a cargo strapping system consists of fittings, webbing, and a tensioning device that all have a break strength of 12,000 pounds, that strapping system’s break strength would be 12,000. However, if one of those components (the fittings, webbing, or tensioning device) has a lower break strength of 9,000 pounds, then the entire strapping system has a break strength of 9,000 instead.

The difference in break strength vs. working load limit comes into play when you understand the concept of the working load limit means. A rigging’s working load limit is the amount of weight that it can handle under normal conditions. This number will always be smaller than the break strength, and that piece of rigging should never hold more than its working load limit.

The working load limit of a rigging system is equal to 1/3 the amount of the break strength. As such, a strapping system with a working load limit of 5,000 pounds has a break strength of 15,000 pounds. Remember, the working load limit will determine how much you should allow the system to hold, not the break strength.

Logistick makes our products able to stand the test of time. Our cargo strapping systems have all undergone extensive testing for both working load limit and break strength, so you can rest easy and trust the numbers you see. If you have any questions about our products or how they work, please give us a call. We’ll be happy to help you out.

All products are sold subject to the following Warnings and Cautions and with the express understanding that the purchaser and/or user are thoroughly familiar with their proper use. Fehr Bros. Industries, Inc. assumes no responsibility for the use, misuse or misapplication of its products.

WORKING LOAD LIMIT: The Working Load Limit (WLL) is the maximum load which should be applied to the product under any condition. WLL is based on a load being uniformly applied in a straight-line pull. It is the responsibility of the end user to determine a WLL for each application. Many factors should be considered including, but not limited to, loads applied, speed of operation, acceleration, length of cable, shock loads, abrasion, corrosion, size, condition of drums and sheaves, and the danger to life and property should a cable break.

MATCHING COMPONENTS: All attachments used with chain and wire rope must be of suitable material, type and strength to provide adequate safety protection. Attachments should have WLL at least equal to the other components with which they are used.

INSPECTION: No product can operate indefinitely at its rated capacity. Cables must be lubricated and maintained in accordance with normal safety standards. Do not kink, knot or crush. Cable, wire rope, chain and attachments must be inspected regularly for any deterioration which may result in the loss of original strength. User must determine whether further use of product would constitute a safety hazard to life or property.

WARNING: Use only Grade 80 Alloy Chain for overhead lifting purposes or where failure is likely to cause damage to property or persons. Proof Coil, High Test, and Grade 70 Transport Chains are not to be used for overhead lifting. Eliminate all twists and kinks in chain before using. All dimensions are nominal and all weights are approximate.

INSPECTION: All chain and attachments should be in­spected regularly for visible damage, distortion, elongation, corrosion, wear, bent links, cracks, or nicks which can cause breakage or seriously reduce the strength and ability to perform safely.

WARNING: Do not exceed the rated capacity of winches or other components. Winches are not to be used for lifting humans or loads overhead. Do not use winches to secure loads to a trailer; use appropriate tie-downs.

appli­cation. Many factors should be consid­ered included among, but not limited to: loads applied, speed of operation, acceleration or deceleration, length of rope or cable, shock loads, abrasion, corrosion, number, size, condition and location of drums and sheaves, facilities for inspection, and the danger to life and property should a rope or cable break.

Wire Ropes and Cables must be stored, used, lubricated and maintained in accor­dance with normal safety standards; and must be proper­ly designed, maintained, and operated. Inspect regularly. Do not kink, knot or crush.

INSPECTION: No product can operate indefinitely at its rated capacity. Wire Rope and Cable must be inspect­ed regularly for any deterioration which may result in the loss of original strength. User must determine whether further use of the rope would constitute a safety hazard to life or property.

The RoHS directive, enacted in the European Union in 2002 and ratified recently in 2015 (RoHS 3), stands for Restriction of Hazardous Substances. This directive impacts the Electronics and Electrical Equipment (EEE) industries and affects any business that sells applicable electronic products, equipment, sub-assemblies, cables (electrical), components or spare parts (as related to the product categories below) to EU countries.