wire rope breaking strength vs working load brands

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.

Rope strength is a misunderstood metric. One boater will talk about tensile strength, while the other will talk about working load. Both of these are important measurements, and it’s worth learning how to measure and understand them. Each of these measurements has different uses, and here we’re going to give a brief overview of what’s what. Here’s all you need to know about rope strength.

Each type of line, natural fiber, synthetic and wire rope, have different breaking strengths and safe working loads. Natural breaking strength of manila line is the standard against which other lines are compared. Synthetic lines have been assigned “comparison factors” against which they are compared to manila line. The basic breaking strength factor for manila line is found by multiplying the square of the circumference of the line by 900 lbs.

As an example, if you had a piece of ½” manila line and wanted to find the breaking strength, you would first calculate the circumference. (.5 X 3.14 = 1.57) Then using the formula above:

To calculate the breaking strength of synthetic lines you need to add one more factor. As mentioned above, a comparison factor has been developed to compare the breaking strength of synthetics over manila. Since synthetics are stronger than manila an additional multiplication step is added to the formula above.

Using the example above, letÂ’s find the breaking strength of a piece of ½” nylon line. First, convert the diameter to the circumference as we did above and then write the formula including the extra comparison factor step.

Knots and splices will reduce the breaking strength of a line by as much as 50 to 60 percent. The weakest point in the line is the knot or slice. However, a splice is stronger than a knot.

Just being able to calculate breaking strength doesn’t give one a safety margin. The breaking strength formula was developed on the average breaking strength of a new line under laboratory conditions. Without straining the line until it parts, you don’t know if that particular piece of line was above average or below average. For more information, we have discussed the safe working load of ropes made of different materials in this article here.

It’s very important to understand the fundamental differences between the tensile strength of a rope, and a rope’s working load. Both terms refer to rope strength but they’re not the same measurement.

A rope’s tensile strength is the measure of a brand-new rope’s breaking point tested under strict laboratory-controlled conditions. These tests are done by incrementally increasing the load that a rope is expected to carry, until the rope breaks. Rather than adding weight to a line, the test is performed by wrapping the rope around two capstans that slowly turn the rope, adding increasing tension until the rope fails. This test will be repeated on numerous ropes, and an average will be taken. Note that all of these tests will use the ASTM test method D-6268.

The average number will be quoted as the rope’s tensile strength. However, a manufacturer may also test a rope’s minimum tensile strength. This number is often used instead. A rope’s minimum tensile strength is calculated in the same way, but it takes the average strength rating and reduces it by 20%.

A rope’s working load is a different measurement altogether. It’s determined by taking the tensile strength rating and dividing it accordingly, making a figure that’s more in-line with an appropriate maximum load, taking factors such as construction, weave, and rope longevity into the mix as well. A large number of variables will determine the maximum working load of a rope, including the age and condition of the rope too. It’s a complicated equation (as demonstrated above) and if math isn’t your strong point, it’s best left to professionals.

However, if you want to make an educated guess at the recommended working load of a rope, it usually falls between 15% and 25% of the line’s tensile strength rating. It’s a lotlower than you’d think. There are some exceptions, and different construction methods yield different results. For example, a Nylon rope braided with certain fibers may have a stronger working load than a rope twisted out of natural fibers.

For safety purposes, always refer to the information issued by your rope’s manufacturer, and pay close attention to the working load and don’t exceed it. Safety first! Always.

If you’re a regular sailor, climber, or arborist, or just have a keen interest in knot-tying, be warned! Every knot that you tie will reduce your rope’s overall tensile strength. Some knots aren’t particularly damaging, while others can be devastating. A good rule of thumb is to accept the fact that a tied knot will reduce your rope’s tensile strength by around 50%. That’s an extreme figure, sure, but when it comes to hauling critical loads, why take chances?

Knots are unavoidable: they’re useful, practical, and strong. Splices are the same. They both degrade a rope’s strength. They do this because a slight distortion of a rope will cause certain parts of the rope (namely the outer strands) to carry more weight than others (the inner strand). In some cases, the outer strands end up carrying all the weight while the inner strands carry none of it! This isn’t ideal, as you can imagine.

Some knots cause certain fibers to become compressed, and others stretched. When combined together, all of these issues can have a substantial effect on a rope’s ability to carry loads.

Naturally, it’s not always as drastic as strength loss of 50% or more. Some knots aren’t that damaging, some loads aren’t significant enough to cause stress, and some rope materials, such as polypropylene, Dyneema, and other modern fibers, are more resilient than others. Just keep in mind that any knots or splices will reduce your rope’s operations life span. And that’s before we talk about other factors such as the weather or your rope care regime…

When it comes to choosing the right rope for the job, it helps to know what variables are at play, like working load, rope tension, and tensile strength of rope. But exactly what is working load, what is tensile strength, and why does rope tension matter? Keep reading to find out!

Tension isthe pulling forceacting along a stretched, flexible connector like aRope. If you want to hang, pull, swing, or support an object with a rope, you must first create enough tension in the rope to the point where the rope is pulled tight enough to cause the object to move. This tension created by the pulling of the rope in the opposite direction of the object you’re trying to move is calledtension force.

When a rope supports an object’s resting weight, the rope’s tension is equivalent to the object’s weight. The simplest way to determine the tension in a rope is using the followingformula:

It’s important to note that rope tension can change based on several variables, and the example above is a simple breakdown of how to find the tension of a non-moving object being pulled straight and not at an angle.

Simply put, tensile strength is the resistance of a material to breaking under tension. In other words, tensile strength is the stress in which a rope can take before breaking or failing. Another common name for the tensile strength of rope is breaking strength.

The tensile strength of a rope can vary based on the thickness, material, and style (braided vs. twisted). Also,Knotsthat are tied into the rope can affect tensile strength. For instance, a ⅜” thickDouble Braid Nylon Docklineboasts a tensile strength of 4,200 pounds, while the same dockline in a ½” thickness can support 7,400 pounds before breaking.

It’s important to recognize that the maximum tensile strength of a rope is not the same weight you should be applying to said rope while expecting it to perform safely. For this, you should limit the weight you plan to support based on the rope’s working load.

Working load is the amount of weight a rope cansafely support without fear of breaking. As previously mentioned, working load is always going to be less weight than tensile strength weight. In fact, most ropes have a working load between 15 to 25% of the rope’s tensile strength. Working load and tensile strength will change based on whether or not you have knots. If you are wondering whether your rope product has an adequate working load to support your needs, contact the manufacturer directly.

No matter what your rope andCordproduct needs may be, SGT KNOTS is sure to have the perfect solution to help you get the job done safely and effectively. Visit SGT KNOTS onFacebookandInstagram, andPinteresttoday to see how our rope products are used every day, Or if you need some inspiration of your own, visit theSGT KNOTS Blog!

The tensile strength is the load at which a new rope, tested under laboratory conditions, can be expected to break. Rope strength is the approximate average for new rope tested under ASTM test method D-6268. To estimate the minimum tensile strength of a new rope, reduce the approximate average by 20%. Age, use and the type of termination used, such as knots, will lower tensile strengths significantly.

One area of misunderstanding that needs to be brought to the surface is the proper interpretation of rope strength, appropriate usage and care. Let"s start by defining two important terms: "tensile strength" and "working load". Tensile strength is the average strength ofnewrope under laboratory conditions. This is determined by wrapping the rope around two large diameter capstans and slowly adding tension to the line until it breaks. The manufacturer"s recommended working load is determined by taking the tensile strength and dividing it by a factor that more accurately reflects the maximum load that should be applied to a given rope to assure a comfortable safety margin and longevity of the line. Of course that factor varies with the type of fiber and the weaving construction. There are however always exceptions, most notably the fact that rope is susceptible to degradation and damage in numerous ways that are not controllable by the manufacturer.

It may surprise you to find out that the working load for most kinds of rope is between 15% and 25% of the tensile strength. Now consider the fact that any time you tie a knot in a rope you effectively cut the tensile strength in half. The knot when tensioned cuts the line. While certain kinds of knots damage the line less than others, the 50% loss of tensile strength is a good general rule to live by. Research has shown that the figure 8 knot reduces the tensile strength by approximately 35% instead of 50% for other common knots tested.

At Ravenox, we use a third-party mechanical services company to test the failure point or break strength of our ropes. There are two common types of breaks: the sharp break and the percentage break. The sharp break is referred to the measurement when load or force drops by 5% from its peak load measurement. A percentage break is another form of break and is generally determined by the sample material and its relationship to load degradation from a peak load measurement. We measure the percentage break.

When it comes to rigging like ratchet straps, winch straps, and just about any other type of strap in the industry, working load limit (WLL) and breaking strength are commonly used measuring metrics.

Every piece of load-bearing wire or rigging equipment carries its own working load limit and break strength rating. These numbers let the user know how much weight that piece of rigging is capable of securing. Though they are usually clearly stated, there is often some confusion about what the two terms mean.

WLL refers to the maximum allowed weight that a piece of rigging can handle under normal conditions. For instance, a winch strap with a WLL of 6,000 pounds should not be used to secure any load above that weight, as it exceeds what it is rated for. WLL is 1/3 of the breaking strength rating, therefore a strap with a WLL of 6,000 pounds would have a breaking strength of 18,000 pounds.

For example, if a ratchet strap is made with end fittings, webbing, and a ratchet that are all rated for 10,000 pounds breaking strength, the overall strength of the product is 10,000 pounds. If any component of the ratchet strap has a lower breaking strength though, the break strength of the unit drops to the rating of the weakest component.

It is critical to understand the differences between the two figures and to make sure that any time you are securing a load, you do so with capable rigging. A failure could not only be costly, but dangerous as well.

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Any job site that utilizes heavy-duty industrial hardware will have a higher rate of job site hazards than the average workplace. Construction zones, transportation services, and manufacturing plants that rely onindustrial chainsfor hoisting, tie-downs, or tension can create dangerous scenarios if they are not mindful of theworking load limit. Miscalculations can cause even strong chains to warp or even break – leading to dangerous and disastrous consequences.

Properly calculating theworking load limitforindustrial chainsis just one of the preventative measures to take to lower these risks. Even though these chains are made from incredibly durable materials, the load-bearing weight should never exceed or even approach the breaking strength. Theworking load limit(WLL) of a chain is a safety precaution to prevent this from happening.

Lower-grade chains (30, 43, and 70) are most commonly used for construction, tie-downs, towing and logging. While these chains are quite durable and have working load limits of up to 15,800 lbs., they are not safe for overhead lifting or rigging applications.

Grade 80 chainsare made from a steel alloy, meaning it contains additional metals for added strength and durability. Grade 80 chains have a breaking load limit of up to 190,800 lbs. and a WLL of 47,700 lbs. They are extremely rugged and often come in a black lacquer finish, which protects the links from damage and wear.

Grade 100 chainsare 25% stronger than Grade 80 and are most commonly used for chain hoists and overhead or even aerial lifts. This style of chain is available in varying lengths and diameters, which can change the breaking load limit and WLL of the entire chain.

Apart from deciding on the grade, length, and chain link diameter required for the intended application, the WLL is one of the most important factors to note before purchasing. This number is the absolute maximum tension that can be safely applied to anindustrial chainwithout compromising its strength.

The WLL is far lower than the maximum breaking strength of a chain. This is to account for added factors that will create additional tension on the chain apart from the load itself. These factors could include:

If you are buying from a reputableindustrial chain supplier, the WLL should be clearly stated for each chain style option. This number is determined by dividing the minimum breaking strength by the safety factor rating for the chain.

The safety factor is a ratio that states how strong of a weight force the chain can withstand before breaking. For most industrial chains, thesafety factor will be 5:1, meaning that if its working load limit is 10,000 lbs. it can technically withstand 50,000 lbs. before snapping. However, this chain should never be used for a 50,000 lbs. load.

Grade 30 and 43 chains are approved for use with construction, securement, and agricultural use. Galvanized or stainless-steel chains may also be used with marine applications, as they are corrosion resistant. Grade 70 has a far higher strength than 30 or 43 and is generally used for transport tie-downs. And remember that overhead lifting is reserved for Grade 80 and higher-grade chains only.

Finally, be sure to consider other factors that could lower a chain’s strength, such as its age or condition. The WLL is calculated with brand-new chains, not ones that are worn from previous use. This is why close inspection of chains is always necessary before using them for a new load or application.

Theworking load limitforindustrial chainsis not overly complicated, but you should understand the basic concepts when using this type of hardware. Before placing an order from anindustrial chain supplier, always double-check the WLL along with the accurate load calculation.

Manufacturing companies choose to use Dyneema rope over steel wire rope for heavy lifting applications such as heavy lift slings, crane rope, and other rigging operations because Dyneema rope:

Dyneema fiber rope is made from Ultra-High Molecular Weight Polyethylene (UHMWPE) fiber. Dyneema 12 strand rope is a common Dyneema fibered rope used for heavy-duty rigging applications. USA Rope & Recovery manufactures several different types of Dyneema fiber rope including the popular 12 Strand, and 24 Strand ropes, as well as others. No matter the application, USA Rope provides strong, durable, and efficient rope for the marine, arborist, nautical, off-roading, and other manufacturing industries.

More times than not, Dyneema fiber rope and steel wire rope are compared by most manufacturing companies–likeThe Rigging Company–for certain maritime, mooring, and towing rope applications. Pound for pound, Dyneema fiber rope is up to 15 times stronger than steel and up to 40% stronger than aramid fibers–otherwise known as Kevlar rope. The high-performance strength and low weight of Dyneema rope ensures that it is safer to use than steel wire rope. Ideally, Manufacturing companies want a rope that can withstand tremendous weight while being light enough to move, use, and work with when needed. Traditionally, steel wire rope is used for heavy-duty maritime, rigging, and mooring rope applications. Although steel wire rope is known for being used for heavy-duty rigging, the disadvantage is the serious risks that come from its heavy-weight and uneven breakage behavior. When a steel wire rope breaks, the combination of the enormous energy and incredible force causes unpredictable recoil. This unpredictable recoil comes from how wire rope is coiled. Essentially, wire rope is several strands of metal wire twisted into a helix, forming a composite rope. When breakage occurs, the helix formed rope unravels, creating a snaking behavior which can cause sharp edges of the broken strands to release at a dangerous force. The lack of strength compared to Dyneema rope shows that steel wire rope is more susceptible to breaking. This can increase risk factors for manufacturing companies that use steel wire rope for rigging, mooring, and heavy duty lifting.

For example, when comparing a ⅜ inch 12 Strand Dyneema rope to a ⅜ inch steel wire rope, the 12 strand Dyneema rope is significantly stronger and presents safer breaking characteristics. The ⅜ inch steel wire rope withstands a load of 14,478 pounds. As the video shows, even in the event of a partial rupture, the steel wire ropes higher mass and recoil provides a greater risk over 12 Strand Dyneema rope. With a ⅜ inch 12 Strand Dyneema rope, it can withstand 18,857 pounds. With the Dyneema fibers low mass and recoil, it reduces the risks for manufacturing companies using rigging rope for heavy-duty lifting applications.

Dyneema is 7 times lighter than steel wire rope at the same strength. In the event of a break, the recoil force is considerably less. Furthermore, the different construction of a Dyneema rope shows a linear recoil without any snaking behavior. This is due to the fact that Dyneema rope is manufactured from UHMWPE, which is comprised of extremely long chains of polyethylene oriented in the same direction, resulting in an overlapping effect. The overlapping of the UHMWPE increases the bond of the chains and thereby strengthens the Dyneema fiber. Dyneema rope offers durable characteristics that can withstand an immense amount of strength while having very little weight to the rope. Because Dyneema fiber is lighter and has a lesser impact when breakage occurs, choosing Dyneema rope over steel wire rope is the safer choice for manufacturing companies working with heavy lifting and below the hook rigging applications for the industrial, nautical, and arborist industries.

When choosing the best rope for any maritime, mooring, towing, or heavy-duty lifting application, choose a rope that can withstand extremely heavy loads and has a long enough lifetime to handle external factors in the nautical, industrial, or arborist industry. In order to decide which rope is best for the job, there are four main challenges that rigging, heavy-duty lifting, mooring, and towing ropes need to overcome:

Dyneema rope is the only high modulus synthetic fiber that has been scientifically engineered–from Ultra-High Molecular Weight Polyethylene (UHMWPE)–to overcome all four of these challenges. Dyneema is the world’s strongest fiber producing ropes that are 15 times stronger than steel wire ropes of the same weight and has become one the most trusted fiber ropes over generic HMPE ropes and steel cable wire ropes for all rigging, maritime, mooring, and towing rope applications.

Manufacturing companies that work with maritime and mooring applications need a durable rigging rope to withstand the constant pulling that comes from the rope running through fairleads and over capstans. Also, in heavy-duty lifting and towing applications, ropes come in contact with rough surfaces such as chocks and the vessel’s deck. These applications can potentially provide severe abrasions to the ropes and degrade the exposed fibers, eventually breaking them. Choosing a Dyneema fibered rope provides manufacturers with a durable, lightweight rope that carries an abrasion lifetime that is four times longer than steel wire rope and rope made with regular HMPE and polyester. With Dyneema’s extended abrasion lifetime, manufacturers are choosing Dyneema rope over steel wire rope for all mooring, towing, maritime, and heavy-duty lifting applications throughout the nautical, arborist, and industrial industries.

Bending fatigue occurs every time a rope flexes under tension. For heavy-duty lifting applications, rope experiences potential bending-fatigue every time something needs to be moved. For example, when a steel beam manufacturer has completed a 15-ton custom-made beam for a military-grade application, the finished product needs to be moved onto a truck for shipment. Rigging ropes are then attached to a crane to then lift, move and place the steel beam from the warehouse to the truck. This can wear out the rope. Another example is when the rope runs over fairleads and pedestals in maritime and mooring applications. This stresses the fiber both inside and outside of the rope causing bending fatigue and decreases the useful life of the rope. Certain conditions in towing and mooring applications can also lead to compression fatigue. This happens when ropes become slack during services and the fibers compress. Due to the molecular properties (UHMWPE) engineered to make Dyneema fiber– and its extremely long chains of polyethylene oriented in the same direction–threats of compression and bending fatigue are far less over other synthetic fibers and steel wire ropes.

In all rigging applications, synthetic ropes elongate when over a long period of time when loaded in higher temperatures–commonly referred to as creep. Creep is irreversible and when combined with abrasions or other risks, it can lead to rope failure. With regular HMPE rope, in heavy-duty lifting and towing applications where high loads and high temperatures are constantly a factor, the creep process can accelerate. This can be a major risk for ropes made from generic HMPE. In contrast, Dyneema rope has up to four times longer creep lifetime. When comparing Dyneema fiber to Spectra, another synthetic fiber rope, under 122 degrees Fahrenheit and 600 MPa load, Dyneema rope has a significantly longer creep lifetime than Spectra fiber rope.

eAfter comparing Dyneema rope to steel wire rope–a ⅜ inch 12 Strand Dyneema rope to a ⅜ inch steel wire rope–there is a guarantee that Dyneema rope is 15 times stronger and better at dealing with abrasions over steel wire rope. For manufacturing companies, Dyneema rope is also considered to be superior to Nylon rope due to Dyneema fiber having low ability to stretch, is UV resistant, and possesses an immense amount of strength. USA Rope properly manufactures Dyneema fibered ropes that are synthetically engineered to uphold incredible weight while enduring constant friction for application uses involving heavy-duty lifting, crane rope support, and below the hook rigging.

Understanding that Dyneema fiber rope is better used for manufacturing companies over steel wire rope, USA Rope & Recovery works hard to manufacture the highest quality rope by using top-of-the-line supplies from across the USA. Dedicating time and effort to finding the next best and technologically advanced products in the market is our main goal at USA Rope in order to help our customers gain the best competitive advantage in their respective field. USA Rope & Recovery also manufactures additional ropes including Spectra, Nylon, Polyester, Polypro, and Kevlar (Aramid) fiber ropes. No matter the application, USA Rope is a leader in custom rope manufacturing for industries including nautical, industrial, arborist, and marine.

In general, running rigging should be replaced whenever it shows visible signs of damage – core hemorrhaged through the cover, several broken strands close together, “rot” from UV exposure, or green and stiff from disuse. There’s a rule of thumb, but it varies rigger to rigger. The Rule of thumb says to replace all rigging hardware every 5-10 years. However, depending on how much everyday usage, weight, and environmental factors the rigging ropes take on can make the rule of thumb shorter or longer.

There are multiple different types of synthetic winch lines available today, many of them are made from Dyneema fibers, while others are made fromPolyester,Nylon,Spectra, orKevlar. Each fiber has benefits and disadvantages and can be chosen depending on your unique application. Spectra is similar to Dyneema fiber but is not as strong or as durable. Because of its strength and durability, Dyneema is the premier synthetic fiber for winching applications.

Minimum Breaking Strength (MBS) and Working Load Limit (WLL), formerly known as Safe Working Load (SWL), are two important strength ratings when it comes to rigging and safety equipment. They vary based on what type of rigging or safety equipment and are identified by manufacturers.

MBS is precisely what it says, the minimum amount of weight you can put on the equipment that would result in equipment failure. This manufacturer’s recommendation is its maximum weight load for lifting equipment.

Due to legal implications the US, and shortly after Europe, began using “working load limit” rather than SWL “safe working load”. However, they mean the same thing.  WLL or SWL is “the breaking load of a component divided by an appropriate factor of safety giving a safe load that could be lifted or carried.”

Both of these load numerical limits are assigned to lifting and/or rigging equipment. Overhead lifting equipment include hooks, shackles, straps, rope, line and equipment like cranes or other lifting devices. Manufacturers assigned a working load limit on these products.

The incorporation of various materials changes your working load limits. The strength of these materials is known as the mechanics of materials and deals with the behavior of solid objects and how they handle stress and strain.

The strength of a material is its ability to withstand an applied load without failure. A load applied to a mechanical member will induce internal forces within the member called stresses when those forces are expressed on a unit basis. The stresses acting on the material cause deformation of the material in various manner. Deformation of the material is called strain when those deformations too are placed on a unit basis. Therein lies the importance of knowing what materials are working with and what your load limits are for all equipment involved in your rigging and hauling.

There is a wide array of rigging accessories needed in hoisting and rigging. Henssgen Hardware is an industrial rigging hardware supplier. The rigging hardware we carry include: snap hooks, pulleys (fixed eye and swivel with single and double sheave), quick links, shackles, wire rope clips, drop forged clevis grab and clevis slip hooks.

Our rigging hardware is manufactured in stainless steel, solid brass, die cast zinc alloy, zinc plated malleable iron and zinc plated. All of our snap hooks are equipped with stainless steel springs. When dealing with expensive equipment, important loads and your safety, you must have quality hardware. Henssgen is committed to providing each one of our customers with the best.

The definition for safe working load is the breaking load of a component divided by an appropriate factor of safety giving a safe load that could be lifted or be carried.

The working load limit is that it is the maximum mass or force which a product is authorized to support in general service when the pull is applied in-line, unless noted otherwise, with respect to the centerline of the product.

Working load limits are calculated on straight line pulls only. Never side load. Other conditions such as extreme temperatures, chemicals solutions or spills, vapors, or immersion in salt water can reduce the Working Load Limit. Welds to any steel products can also void out a Working Load Limit rating.

It can be confusing to decrypt all of these acronyms like SWL, NWL, WLL and MBS. But Henssgen Hardware is here for you, to educate you on terms like Working Load Limits and everything you need to know about our products.

Safe Working Load, SWL, (or Normal Working Load, NWL) is an outdated term that was used to indicate the amount of weight that a lifting device could safely carry without fear of breaking. It is a calculation of the Minimum Breaking Strength, or MBS.

The specific definition for the Working Load Limit (WLL) is: The maximum mass or force which a product is authorized to support in general service when the pull is applied in-line, unless noted otherwise, with respect to the centerline of the product.

The manufacturer designates the right or approximate WLL value for each lifting device or use, and considers many factors including the applied load, the length of each rope or line, and many other factors.

It is critically important to heed this number, which is set forth by the manufacturer, when lifting with any device, including a line, rope or crane. The number is calculated by dividing the Minimum Breaking Strength (MBS) by a safety factor that is assigned to that type and use of equipment, generally ranging from four to six unless a failure of the equipment could pose a risk to life. In the event that the failure of the equipment could pose a risk to life, the safety factor is ten.

For example, if a hook has a Minimum Breaking Strength (MBS) of 1,000 pounds and a safety factor of five, then the Working Load Limit (WLL) would be 200 pounds.

There were legal implications to the term Safe Working Load, so USA standards phased this term out more than twenty years ago, followed by European and ISO standards just a few years afterward. This change took place because of the legal significance placed on the word ‘safe’.

The Americans and Europeans then developed a more appropriate term and definition for the maximum load capacity of a particular lifting device, agreeing to use the term Working Load Limit (WLL) for equipment such as hooks, slings and shackles.

In the cases of cranes, hoists and winches, the term Safe Working Load (SWL) was replaced by Manufacturer’s Rated Capacity (MRC), which is the maximum gross load which may be applied to the crane or hoist or lifting attachment while in a particular working configuration and under a particular condition of used.

Are you planning your next overhead lifting project and unsure about the best type of lifting sling to use? Or, maybe you’re not getting the service life you would expect out of the slings that you’re currently using? Alloy chain slings, wire rope slings, synthetic slings, and metal mesh slings can all be used to safely and efficiently lift, move, and position a load.

But, choosing the right type of lifting sling is dependent on a complete understanding of the application, the environment it’s being used in, and how the sling will be used to support and lift the load.

At Mazzella, we provide ideal lifting solutions—offering all styles of lifting slings, rigging hardware, wire rope, overhead cranes and hoists, and engineered lifting devices. Our goal for this article is to help you understand the basics of overhead lifting slings and provide you with the advantages and disadvantages of each type so you can make an informed decision and select the best lifting sling for your particular application.

Wire rope is a preferred lifting device for many reasons. Its unique design consists of multiple steel wires that form individual strands laid in a helical pattern around a fiber or steel core. This structure provides strength, flexibility, and the ability to handle bending stresses.

Wire rope slings are popular in construction, automotive, oil and gas, and general manufacturing industries where a variety of heavy loads and rugged conditions exist. They’re also very popular in steel mills and forging facilities where the durability of the rope is really put to the test.

Different configurations of the material, wire, and strand structure will provide different benefits for the specific lifting application—including abrasion resistance, strength, flexibility, and fatigue resistance. Wire rope slings have a lower initial cost than alloy chain, while remaining fairly lightweight in design.

Wire rope slings are available in single-leg or multi-leg assemblies and can be used in a variety of hitches including vertical, choker, and basket hitches. The Design Factor for wire rope slings is a 5:1 ratio, meaning the breaking strength of the sling is five times higher than the rated Working Load Limit (W.L.L). Per the Wire Rope Users Manual, a design factor is necessary to allow for conditions such as wear, abrasion, damage, and variations in loads which are not readily apparent. Although wire rope slings have a design factor, the user should never exceed the rated Working Load Limit.

When it comes to toughness and dependability—alloy chain slings are the bulldogs of lifting slings. Chain slings can be used to lift very heavy and bulky loads on a regular or repetitive basis. Their flexible design provides strength and durability so they can withstand impact, extreme temperatures, and exposure to chemicals and UV rays.

Chain slings are preferred in high-temperature applications and for lifting heavy-duty loads. Their strength and durability allow them to be used in foundries, steel mills, heavy machine shops, and any other environment where repetitive lifts or harsh conditions would damage or destroy a wire rope sling or synthetic nylon or polyester sling. If any damage does occur on a chain sling, they are completely repairable and can be load tested-and re-certified after the repair.

Alloy chain slings can be heated up to temperatures of 1000°F, however the Working Load Limit must be reduced in accordance with the manufacturer’s recommendations when continually exposed to temperatures above 400°F.

The Design Factor for chain slings is a 4:1 ratio, meaning the breaking strength of the sling is four times higher than the rated Working Load Limit. Although chain slings have a design factor, the user should never exceed the rated Working Load Limit.

For highly finished parts or delicate equipment, nothing beats the flexibility, strength, and support that synthetic lifting slings can provide. Synthetic slings can be made from nylon or polyester materials and are lightweight, easy to rig, and extremely flexible. They’re extremely popular in construction and other general industries because they’re fairly inexpensive, come in a variety of standard sizes, and can be replaced easily.

Because they’re so flexible, they can mold to the shape of delicate and irregularly-shaped loads, or be used in a choker hitch to securely grip loads of round bar stock or tubes. The soft materials they’re made from are strong enough to lift heavy loads, but will protect expensive and delicate loads from scratches and crushing. Synthetic slings are extremely versatile, can be used in vertical, choker, and basket hitches and have a Design Factor of 5:1, meaning the breaking strength of the sling is five times higher than the rated Working Load Limit.

Because they’re made of non-sparking and non-conductive fibers, they can be used in explosive atmospheres. However, they’re also more susceptible to cuts, tears, abrasions. Exposure to heat, chemicals, and UV rays can also cause damage and weaken the strength and integrity of the sling.

Web slings are flat belt straps made of webbing material and most commonly feature fittings, or flat or twisted eyes, on each end. Web slings are the most versatile and widely-used multi-purpose sling. They’re strong, easy to rig, and inexpensive. Compared to alloy chain slings, they’re more flexible and lighter and can be used to help reduce scratching and denting to loads. They can also be fabricated with wide load-bearing surfaces up to 48” to provide significant surface contact for heavy and large loads.

They also have a relatively low heat-resistance and are not to be used in environments that exceed 194°F, or environments where temperatures are below -40°F. For loads with sharp edges, corner protectors or edge guards should be used to protect the sling from cuts and tears. Because there is a difference between abrasion-resistant protection and cut-resistant protection, be sure to identify the type of resistance required for your application.

If used outdoors, they should be stored away in a cool, dark, and dry environment to avoid prolonged exposure to sunlight and UV rays, which can damage and weaken the strength of the sling. When a lift is made at the W.L.L., the user can expect approximately 8-10% stretch when using a nylon web sling and 3% stretch when using a polyester web sling at rated capacity.

Endless roundslings have load-bearing fiber or core yarns that are protected by a woven outer jacket. They are strong, soft and flexible, and protect smooth or polished surfaces from scratches, dents, and crushing. Roundslings can be used in vertical, basket, or choker hitches—which are especially useful for lifting tubes and pipes.

The woven outer jacket is designed to protect the internal load-bearing fibers and core yarns against abrasion, dirt and grease, and UV degradation. Polyester roundslings are suitable for acidic environments, or near chemicals used as bleaching agents, but should not be used in alkaline environments.

Like web slings, roundslings are more susceptible to heat damage and should not be used in environments that exceed 194°F or below -40°F. For loads with sharp edges, corner protectors or edge guards should be used to protect the sling from cuts and tears.

If used outdoors, they should be stored in a cool, dark, and dry environment to avoid prolonged exposure to sunlight and UV rays, which can damage and weaken the strength of the sling. When a lift is made at the W.L.L., the user can expect approximately 3-5% stretch when using a roundsling.

Unlike standard roundslings, Twin-Path® roundslings utilize two paths of K-Spec®load-bearing fibers. The Twin-Path® patented design provides the rigger with two connections between the hook and the load for redundant back-up protection. They also feature other technologies like a Check-Fast® inspection system and an External Warning Indicator (EWI) that can provide visual indications of overloading, UV damage and degradation, or damage to the internal core fibers.

Twin-Path® slings are susceptible to cuts and tears to the jacket when used to support loads with sharp corners or edges. The specially-designed Covermax® Cover provides the best ultraviolet (UV) protection and the best abrasion protection of any commercially available synthetic lifting sling. CornerMax® Pads and CornerMax® sleeves are extremely cut resistant and can be used to protect the Twin-Path® slings in applications where cutting is a concern. If the outer jacket is cut or torn, and the load bearing fibers are not cut, Twin-Path® slings are repairable by applying a patch and proof-testing the sling after the repair is performed.

Although synthetic rope slings have been in use for over sixty years, the advancement of high-performance fibers has recently improved the perception of using rope slings for overhead lifting applications. These high-performance fibers are characterized by their light weight, strength, flexibility, and versatility. Not only are they becoming more widely-accepted, but are preferred in certain lifting applications in the construction, shipyard, and offshore and deepwater industries. Because there are various types of synthetic rope material, it’s critical to know the specific fiber that a rope is made from to help understand its environmental characteristics.

Diameter to diameter, a synthetic rope sling is approximately 1/8 the weight of a steel wire rope sling with similar specifications, and compared to chain slings, they offer even more significant weight-savings.

Another major benefit of synthetic rope slings, is that if a break or failure occurs, there is no whipping motion of the sling or projectiles that could injure nearby workers. When a steel rope or chain breaks, the reaction is often violent and explosive and can potentially injure workers or damage nearby equipment.

Synthetic rope slings are more prone to damage from abrasion or cutting when lifting loads with sharp corners or edges. Additional edge protection and abrasion protection is available, but can add significant costs to the slings to try and equal the durability and resistance that more traditional steel slings offer.

Depending on the type of fiber, some newer technology synthetic ropes can be used outdoors in harsh elements (UV exposure, rain, snow, freezing temperatures), in chemically-active environments, and are neutrally-buoyant so they can be used in freshwater or saltwater environments. Consult the sling manufacturer or a Qualified person to confirm how a specific sling material may react to sunlight, UV, or chemicals.

Disadvantages of Using Synthetic Rope SlingsSynthetic rope is not as durable as steel slings in that they will experience cutting, fraying, and abrasion if used to lift loads with sharp edges

Some synthetic rope sling material may be susceptible to chemically active environments or exposure to sunlight or UV light. Consult the sling manufacturer or a Qualified person to confirm how a specific sling material may react to sunlight, UV, or chemicals.

Metal mesh slings are made from high-tensile carbon, alloy, or stainless steel wire mesh and are used primarily in metalworking and other industries where the loads can be hot, abrasive, or have the tendency to cut through softer synthetic slings. They’re resistant to corrosion and they’re designed to last in demanding and rugged operating environments.

Metal mesh slings are flexible and have a wide bearing surface that can be used to firmly grip an irregular load without extensive stretching and can be used in vertical, basket, or choker hitches. They’re extremely resistant to abrasion and cutting, however if there is evidence of even one broken wire in the sling, the entire sling needs to be removed from service. The Design Factor for wire rope slings is a 5:1 ratio, meaning the breaking strength of the sling is five times higher than the rated Working Load Limit. Although metal mesh slings have a design factor, the user should never exceed the rated Working Load Limit.

As you can see, there are many different options when it comes to selecting the proper lifting sling for the job at hand. Many factors should be considered to ensure that the lifting sling you select will provide consistent performance over many safe and reliable lifts:Strength and rated capacity of the sling

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.

1. Turn back the specified amount of rope from the thimble. Apply the first clip one base width from the dead end of the wire rope. Place the U-bolt over the dead end; the live end rests in the clip saddle. Tighten the nuts evenly to the recommended torque.

3. Space additional clips, if required, equally between the first two. Turn on nuts, take up any rope slack, and tighten all nuts evenly to the recommended torque.

4. Apply the initial load and retighten the nuts to recommended torque. The rope will stretch and shrink in diameter when loads are applied. Inspect the clips periodically and retighten. Recommended torque values are based on the threads being clean, dry and free of lubrication.

Loads may slip or fall if proper eye bolt assembly and lifting procedures are not used. Always inspect eye bolts before use and never use eye bolts that show signs of wear or damage. Never use eye bolts if eye or shank is elongated or bent. Be sure all threads are clean. Do not exceed the following working load li

Fibrous and synthetic rope, wire rope and cable must be inspected regularly. No product, even when used in the proscribed manner, can function forever at its rated capacity. The end user must inspect the product frequently for any condition (abrasion, abuse, negligence, normal wear and tear, etc.) which, should the product be left in use, might result in its failure.

Working load is based upon static or moderately dynamic lifting/pulling operations. Instantaneous changes in load, up or down, in excess of 10% of the sling"s rated working load constitutes hazardous shock load, and would void normal working load recommendations.

These products are not designed or recommended for use in the entertainment rigging business, but are offered as a service to our customers who indulge in climbing or similar recreational activities. It is the responsibility of the end user to be properly trained in the inspection, maintenance and use of these products.

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.