wire rope breaking strength vs working load supplier

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…

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.

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 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!

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.

Wire ropes are essential for safety purposes on construction sites and industrial workplaces. They are used to secure and transport extremely heavy pieces of equipment – so they must be strong enough to withstand substantial loads. This is why the wire rope safety factor is crucial.

You may have heard that it is always recommended to use wire ropes or slings with a higher breaking strength than the actual load. For instance, say that you need to move 50,000 lbs. with an overhead crane. You should generally use equipment with a working load limit that is rated for weight at least five times higher – or 250,000 lbs. in this case.

This recommendation is all thanks to the wire rope safety factor. This calculation is designed to help you determine important numbers, such as the minimum breaking strength and the working load limit of a wire rope.

The safety factor is a measurement of how strong of a force a wire rope can withstand before it breaks. It is commonly stated as a ratio, such as 5:1. This means that the wire rope can hold five times their Safe Work Load (SWL) before it will break.

So, if a 5:1 wire rope’s SWL is 10,000 lbs., the safety factor is 50,000 lbs. However, you would never want to place a load near 50,000 lbs. for wire rope safety reasons.

The safety factor rating of a wire rope is the calculation of the Minimum Break Strength (MBS) or the Minimum Breaking Load (MBL) compared to the highest absolute maximum load limit. It is crucial to use a wire rope with a high ratio to account for factors that could influence the weight of the load.

The Safe Working Load (SWL) is a measurement that is required by law to be clearly marked on all lifting devices – including hoists, lifting machines, and tackles. However, this is not visibly listed on wire ropes, so it is important to understand what this term means and how to calculate it.

The safe working load will change depending on the diameter of the wire rope and its weight per foot. Of course, the smaller the wire rope is, the lower its SWL will be. The SWL also changes depending on the safety factor ratio.

The margin of safety for wire ropes accounts for any unexpected extra loads to ensure the utmost safety for everyone involved. Every year there aredue to overhead crane accidents. Many of these deaths occur when a heavy load is dropped because the weight load limit was not properly calculated and the wire rope broke or slipped.

The margin of safety is a hazard control calculation that essentially accounts for worst-case scenarios. For instance, what if a strong gust of wind were to blow while a crane was lifting a load? Or what if the brakes slipped and the load dropped several feet unexpectedly? This is certainly a wire rope safety factor that must be considered.

Themargin of safety(also referred to as the factor of safety) measures the ultimate load or stress divided by theallowablestress. This helps to account for the applied tensile forces and stress thatcouldbe applied to the rope, causing it to inch closer to the breaking strength limit.

A proof test must be conducted on a wire rope or any other piece of rigging equipment before it is used for the first time.that a sample of a wire rope must be tested to ensure that it can safely hold one-fifth of the breaking load limit. The proof test ensures that the wire rope is not defective and can withstand the minimum weight load limit.

First, the wire rope and other lifting accessories (such as hooks or slings) are set up as needed for the particular task. Then weight or force is slowly added until it reaches the maximum allowable working load limit.

Some wire rope distributors will conduct proof loading tests before you purchase them. Be sure to investigate the criteria of these tests before purchasing, as some testing factors may need to be changed depending on your requirements.

When purchasing wire ropes for overhead lifting or other heavy-duty applications, understanding the safety dynamics and limits is critical. These terms can get confusing, but all of thesefactors serve an important purpose.

Our company has served as a wire rope distributor and industrial hardware supplier for many years. We know all there is to know about safety factors. We will help you find the exact wire ropes that will meet your requirements, no matter what project you have in mind.

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.

The use of rope for any purpose results in friction, bending and tension. All rope, hardware, sheaves rollers, capstans, cleats, as well as knots are, in varying degrees, damaging to ropes. It’s important to understand that rope is a moving, working, strength member and even under the most ideal conditions will lose strength due to use in any application. Maximizing the safety of rope performance is directly related to how strength loss is managed and making sure ropes are retired from service before a dangerous situation is created. Ropes are serious working tools and used properly will give consistent and reliable service. The cost of rope replacement is extremely small when compared to the physical damage or personnel injury that can result from using a worn out rope.

There are basically three steps to consider in providing the longest possible service life for ropes, the safest conditions and long range economy: Selection, Usage and Inspection.

Selecting a rope involves evaluating a combination of factors. Some of these factors are straight forward, like comparing rope specifications. Others are less qualitative, like color preference or how a rope feels while handling. Cutting corners, reducing design factors, sizes or strengths on an initial purchase creates unnecessary replacements, potentially dangerous conditions and increased long term costs. Fiber and construction being equal, a larger rope will outlast a smaller rope, because of greater surface wear distribution. By the same token, a stronger rope will outlast a weaker one, because it will be used at a lower percentage of its break strength and corresponding Work Load Limit with less chance of overstressing. The following factors should be considered in your rope selection: Strength, Elongation, Firmness, Construction and Abrasion.

When given a choice between ropes, select the strongest of any given size. A load of 200 pounds represents 2% of the strength of a rope with a 10,000 Lbs. breaking strength. The same load represents 4% of the strength of a rope that has a 5,000 Lbs. breaking strength. The weaker rope will work harder and as a result will have to be retired sooner. Braided ropes are stronger than twisted ropes that are the same size and fiber type.

Please note that the listed break strengths are average break strengths and do not consider conditions such as sustained loads or shock loading. Listed break strengths are attained under laboratory conditions. Remember also that break strength is not the same as the Work Load Limit.

It is well accepted that ropes with lower elongation under load will give you better control. However, ropes with lower elongation that are shock loaded, like a lowering line, can fail without warning even though the rope appears to be in good shape. Low elongating ropes should be selected with the highest possible strength. Both twisted ropes and braided ropes are suitable for rigging. Size for size, braided rope has higher strength and lower stretch than a twisted rope of similar fiber. See page 390 for additional information on rope elongation.

Select ropes that are firm and hold their shape during use. Soft or mushy ropes will snag easily and abrade quickly causing accelerated strength loss.

Rope construction plays an important role in resistance to normal wear and abrasion. Braided ropes have a basically round, smooth construction that tends to flatten out somewhat over the bearing surface. Flattening distributes wear over a much greater area, as opposed to the crowns of a three strand or to a lesser degree, an eight strand rope.

All rope will be severely damaged if subjected to rough surfaces or damaging edges. All rope must be protected against damaging or abrasive surfaces. Wire rope will score and gouge chocks and bitts creating cutting edges that can damage synthetic ropes. Chocks, bitts, drums and other surfaces must be kept in good condition and free of burrs and rust. Weld beads on repaired capstans, fairleads, etc., are equally damaging, unless dressed down smoothly. Pulleys must be free to rotate and should be of proper size to avoid

Avoid using a rope that shows signs of aging and wear. If in doubt, do not use the rope. Damaged rope must be destroyed to prevent any future use. No visual inspection can be guaranteed to accurately and precisely determine the residual strength of the rope. When fibers show wear in any area, the damaged area must be removed and the rope should be re-spliced or replaced. Check regularly for frayed or broken strands. Pulled strands should be rethreaded into the rope if possible. A pulled strand can snag on a foreign object during usage. Both outer and inner rope fibers may contribute to the strength of the rope. When either is worn the rope is naturally weakened. Open the strand of the rope and inspect for powdered fiber, which is one sign of internal wear. A heavily used rope will often become compacted or hard, which indicates reduced strength. The rope should be discarded and made unusable if this condition is detected. See pages 395 and 396 for additional inspection information.

New rope tensile strength is based upon tests of new and unused spliced rope of standard construction in accordance with Samson testing methods, which conform to Cordage Institute, ASTM and OCIMF test procedures. It can be expected that strengths will decrease as soon as a rope is put into use. Because of the wide range of rope use, changes in rope conditions, exposure to the many factors affecting rope behavior and the possibility of risk to life and property, it is impossible to cover all aspects of proper rope applications or to make generalized statements as to Work Load Limits.

Work Load Limits are the load that a rope in good condition with appropriate splices in non-critical applications is subjected to during normal activity. They are normally expressed as a percentage of new rope strength and should not exceed 20% of the stated break strength. Thus, your maximum Work Load Limit would be 1/5 or 20% of the stated break strength.

A point to remember is that a rope may be severely overloaded or shock loaded in use without breaking. Damage and strength loss may have occurred without any visible indication. The next time the rope is used under normal Work Loads and conditions, the acquired weakness can cause it to break.

Normal Work Load Limits do not cover dynamic conditions such as shock loads or sustained loads, nor do they apply where life, limb or property are involved. In these cases a stronger rope must be used and/or a higher design factor applied.

Normal Work Load Limits are not applicable when rope is subjected to dynamic loading. Whenever a load is picked up, stopped, moved or swung there is increased force due to dynamic loading. The more rapidly or suddenly such actions occur, the greater the increase in the dynamic loading. In extreme cases, the force put on the rope may be two, three or many more times the normal Work Load involved. Examples of dynamic loading would be: towing applications, picking up a load on a slack line or using a rope to stop a falling object. Dynamic loading affects low elongation ropes like polyester to a greater degree than higher elongation, nylon ropes. Dynamic loading is also magnified on shorter length ropes when compared to longer rope lengths. Therefore, in all such applications, normal Work Load Limits do not apply.

IMPORTANT NOTE: Many industries are subject to state and federal regulations for Work Load Limits that supersede those of the manufacturer. It is the responsibility of the user to be aware of and adhere to those laws and regulations.

Work Load Limits as described do not apply when ropes have been subjected to shock loading. Whenever a load is picked up, stopped, moved or swung, there is an increased force due to dynamic loading. The more rapidly or suddenly such actions occur, the greater this increase in force will be. The load must be handled slowly and smoothly to minimize dynamic effects. In extreme cases, the force put on the rope may be two, three or even more times the normal Work Load involved. Examples of shock loading are picking up a tow on a slack line or using a rope to stop a falling object. Therefore, in all applications such as towing lines, life lines, safety lines, climbing ropes, etc., design factors must reflect the added risks involved. Users should be aware that dynamic effects are greater on a low elongation rope such as manila than on a high-elongation rope such as nylon and greater on a shorter rope than on a longer one.

The shock load that occurs on a winch line when a 5,000 Lbs. object is lifted vertically with a sudden jerk may translate the 5,000 Lbs. of weight into 30,000 Lbs. of dynamic force, which could cause the line to break. Where shock loads, sustained loads or where life, limb or valuable property is involved, it is recommended that a much higher design factor than 5 be used.

Remember, shock loads are simply a sudden change in tension, from a state of relaxation or low load to one of high load. The further an object falls, the greater the impact. Synthetic fibers have a memory and retain the effects of being overloaded or shock loaded. Ropes that have been shock loaded can fail at a later time, when used within Work Load Limits.

Wire rope is the lifeline of your tow truck. We’ll help you understand the terminology, construction and ratings of wire rope. We’ll also give you advice on what type of rope to buy, how to attach it to a hook without losing towing capacity, how to inspect and maintain it, how to prevent damage, and how to tell when it’s time to replace it. We’ll also give the pros and cons of synthetic versus wire rope.

“Wire rope,” “line,” “rope” or “wire” are the only correct ways to refer to wire rope, but many tow operators refer to it as cable. Wire rope is not cable. Cable is only an acceptable term when referring to a piece of wire rope that is terminated on both ends. When that cable is connected to a power source, such as a winch, it’s no longer acceptable to call it cable.

The Egyptians were among the first to twist and braid strands of plant material together to form rope. Today’s rope is made of different materials and using different methods, but the basic principle remains the same: smaller diameter material is twisted to form strands, and then those strands are twisted to form the rope (or wire, if the rope is made from steel).

The pictures below show a 6 x 19 wire rope. The ‘19’ refers to the number of smaller diameter wires that are twisted together to form a single strand. The ‘6’ refers to the number of strands that are twisted together to make the wire. The middle of the rope, which isn’t included in either number, is referred to as “the core.”

You might have seen the term “lay” when a manufacturer specifies the type of wire to be used on a piece of their equipment. Lay refers to the direction of the twist of the wires in a strand (right or left) and to the direction that the strands are laid in the rope (regular or lang).

When you inspect a rope with regular lay, the wires appear to run straight down the length of the rope. With lang lay, the wires twist in the same direction as the strands, giving the appearance that the wires run across the rope. Regular lay rope is the most common wire sold today.

Just because your wire rope says it’s rated for an ultimate load (UL, or breaking strength) of 39,000 lbs doesn’t mean you can use that rope to tow 39,000 lbs. That’s because every wire rope has a working load limit (or WLL), which is the actual mass or force the product can support. It’s the working load limit you shouldn’t exceed, not the ultimate load limit.

So why don’t rope manufacturers make our lives easier by giving the WLL on their packaging instead of the UL? That’s because wire rope can handle different weights depending on how it’s being used. Different industries have different WLLs.

For example, standard 1/2” 6 x 19 wire rope has an ultimate load of 26,600 lbs. The working load limit for towing and recovery is 26,600 divided by 4, which is 6,650 lbs.

Synthetic rope is becoming a popular tool in the towing and recovery industry for many reasons. It has a significantly higher rating compared to standard wire, it is much lighter and, because it has no memory, there is less risk of damage caused by bird nesting.

Over the last few years, synthetic rope has also become more available to our industry. There are a wide range of distributors stocking the common sizes.

As with any synthetic product, synthetic rope is more susceptible to damage from sharp edges, but synthetic ropes made with Dyneema fiber is incredibly durable.

The three most common terminations used when attaching a hook to a wire rope are a Flemish eye with thimble splice, open swage socket, and wedge and socket (Becket). The most common of all the terminations is the Flemish eye with thimble splice.

In all cases except the open swage socket (pictured below), the rated capacity of wire rope is reduced when a termination is added to the end of the wire. When a Flemish eye with thimble splice is installed properly, it preserves 90 to 96% of the rope’s rated capacity.

The wedge and socket (pictured below) is the least recommended termination and should only be used to repair a wire that has been damaged in the field. The termination efficiency for the wedge and socket is 80% of the wire’s rated capacity. That means if we install a wedge and socket on the standard 1/2” 6 x 19, our working load limit is reduced to 5,320 lbs (WLL of 6,650 lbs x 0.8 = 5,320 lbs).

We don’t recommend using wire rope clips to terminate a hook on wire rope. Many times these clips are not installed correctly, which significantly reduces the termination efficiency.

Grade of steel. Wire rope is constructed with different grades of steel the same way that chain is manufactured. The most common wire rope grade is extra improved plow steel (EIPS) but you can also select extra extra improved plow steel (EEIPS) that is 10% stronger.

Steel core vs fiber core. When wire rope is constructed, the strands and wires are wrapped around a center core made of either independent wire rope core (IWRC) or fiber core (FC). IWRC, which is made of steel, provides additional strength. Fiber core cushions the strands by accepting lubricant more effectively. For the towing industry, we feel that the benefit of increasing our single line rating with steel core wire outweighs the benefits that fiber core offers.

Strength of rope. When it comes to wire rope, as with many things in life, you get what you pay for. A 1/2” standard 6 x 19 steel core wire rope has a working load limit of 6,650 lbs. If you go for a ½” Python COMPAC 6 steel core rope, your WLL increases to 7,550 (14% increase). Opt for a ½” Python COMPAC 35 steel core rope and your WLL increases to 9,100 (a 37% increase over then standard wire). The COMPAC 35 rope will cost you three times the price of the standard 6-strand wire, though.

Lang lay or regular lay. There are advantages and disadvantages to both lang and regular lay wire rope, depending on the application. Most manufacturers specify the types and lays of wire rope to be used on their piece of equipment. Be sure to consult the operator’s manual for proper application.

Quality of manufacturer. Talk to your wire rope supplier about the rope manufacturer. Imported wire rope is very common in today’s marketplace and many of these suppliers are quality manufacturers. The only way you can tell the quality is by asking questions about the product you’re buying.

It’s important to regularly inspect your wire rope for damage. The most common signs of damage are broken strands, kinks, and flat spots from improper wrapping on the winch drum. Constantly inspect your wire during a recovery to ensure that the winch is gathering wire properly on the winch drum and the wire is properly layered on the winch. If you want to prolong the life of your rope, take the time to unwind and rewind your wire at the first sign of overlapping or bird nesting and always stay within the working load limit.

Depending on the amount of wear and tear your wire is exposed to, you may need to replace it more often. In order to determine when you need to replace your wire, you must unwind it from the winch drum and inspect each foot of wire to determine if it needs attention. This is also a perfect time to lubricate your wire when you wind it back onto the winch. We recommend replacing your wire rope at the first sign of overloading.

It’s important to remember that most wire ropes fail from the inside out. Wire rope lubricant prolongs the life of your wire by protecting it from rust and corrosion while at the same time keeping it flexible. The best lubricant is one that was specifically designed for wire rope. Select a lubricant that doesn’t contain acids or alkalis. We recommend a moly or asphalt-based lubricant. Don’t apply used oils.

In order to protect ourselves and others from injury we must have the confidence in the equipment we are using. You can now speak to your rope supplier with confidence. Ask questions about the product you are about to buy. You never know if it is a quality manufactured piece of equipment.

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.

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.

It turns out that there is little margin of safety with steel cable equipped winches. Why is this? Unlike the lifting industry, the recreational pulling industry is unregulated, consequently winch manufacturers typically equip winches with steel cables with minimum breaking strengths that are very close to the max winch capacities. The lifting industry requires a 5:1 safety factor due to the overhead dangers. The pulling industry does not. In fact many steel equipped winches possess a safety factor of less than 1.5!

Take for instance common 5/16 steel cable supplied on most winches up to 10K capacities. The working load limit (WLL) on common 5/16 steel cable is only 2000 pounds. The minimum breaking strength is approximately 10K pounds. So in many cases a 10K winch can be supplied with a steel cable with a minimum breaking strength of 10K. Take a look at the steel cable writeup from our friend Tyler at Roundforge (Roundforge.com) for more comprehensive data on steel cable types and classes.

One of the reasons that cable failures are relatively infrequent is mostly due to vehicle recoveries being in the 4-5k pulling load range, well below the cable breaking strength. Also, often times steel cables can possess ultimate strengths above the minimum breaking loads. So what’s the takeaway here? Due to the little margin of safety in steel cables, make sure you properly maintain the cable and be on the lookout for weakening factors like kinks, broken wires etc., and when possible use a snatch block to reduce the cable load.

Picture supplied by our friend James Pickard. James snapped his steel cable while using the UltraHook. The UltraHook possesses a breaking strength of 31,000 pounds(hook opening) to 48,000 pounds(shackle pin mount). Engineering facts matter.

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LANDMANN WIRE ROPE PRODUCTS, INC. assumes no responsibility for the use or misapplication of any product sold by this firm. Responsibility for design and use decisions rests with the user. All products are sold with the express understanding that the purchaser is thoroughly familiar with the correct application and safe use of same. USE ALL PRODUCTS PROPERLY, IN A SAFE MANNER AND FOR THE APPLICATION WHICH THEY ARE INTENDED.

WORKING LOAD LIMIT: This is the term used throughout the catalog. There are, however, other terms used in the industry which are interchangeable with the term WORKING LOAD LIMIT. These are WLL, SWL, SAFE WORKING LOAD, RATED LOAD VALUE, RESULTING SAFE WORKING LOAD, and RATED CAPACITY.

NEVER EXCEED THE WORKING LOAD LIMIT The Working Load limit is the maximum load which should ever be applied to a product, even when the product is new and when the load is uniformly applied -straight line pull only. AVOID SIDE LOADING. All catalog ratings are based upon usual environmental conditions, and consideration must be given to unusual conditions such as extreme high or low temperatures, chemical solutions or vapors, prolonged immersion in salt water, etc. Such conditions or high risk applications may necessitate reducing the Working Load limit. WORKING LOAD LIMIT WILL NOT APPLY IF PRODUCT HAS BEEN WELDED OR OTHERWISE MODIFIED. It should also be noted that it is the responsibility of the ultimate user to determine a Working Load limit for each application.

MATCHING OF COMPONENTS Components must match. Make certain that components such as hooks, links, or shackles, etc. used with wire rope (or chain or cordage) are of suitable material size and strength to provide adequate safety protection. Attachments must be properly installed and must have a Working Load Limit at least equal to the product with which they are used. Remember, chain is only as strong as its weakest link.

RAISED LOADS KEEP OUT FROM UNDER A RAISED LOAD. Take notice of the recommendation from the National Safety Council Accident Prevention Manual concerning all lifting operations -.’All employees working at cranes or hoists or assisting in hooking or arranging a load should be instructed to keep out from under the load. From a safety standpoint, one factor is paramount to know: conduct all lifting operations in such a manner that if there were an equipment failure, no personnel would be injured. This means keep out from under a raised load and keep out of the line of force of any load. “DO NOT OPERATE A LOAD OVER PEOPLE. DO NOT RIDE ON LOADS”

SHOCK LOADS Avoid impacting, jerking or swinging of load as the Working Load limit could be exceeded and the Working Load limit will not apply. A shock load is generally significantly greater than a static load. AVOID SHOCK LOADS.

REMEMBER: ANY PRODUCT WILL BREAK IF ABUSED, MISUSED, OVERUSED OR NOT MAINTAINED PROPERLY. Such breaks can cause loads to fall or swing out of control, possibly resulting in serious injury or death as well as major property damage.

WORKING LOAD LIMIT (WLL) The Working Load Limit is the maximum load which should ever be applied to the product, even when the product is new and when the load is uniformly applied -straight line pull only. AVOID SIDE LOADING. All catalog ratings are based upon usual environmental condition and consideration must be given to unusual conditions such as extreme high heat or low temperatures, chemical solutions or vapors, prolonged immersion in salt water, etc. NEVER EXCEED THE WORKING LOAD LIMIT.

PROOF TEST LOAD (PROOF LOAD) The term “Proof Test” designated a quality control test applied to the product for the sole purpose of detecting defects in material or manufacture. The Proof Test Load (usually twice the Working Load Limit) is the load, which the product withstood without deformation when new and under laboratory test conditions. A constantly increasing force is applied in direct line to the product at a uniform rate of speed on a standard pull-testing machine. The Proof Test Load does not mean the Working Load Limit should ever be exceeded.

BREAKING STRENGTH / ULTIMATE STRENGTHDo not use breaking strength as a criterion for service or design purposes. Refer to the Working Load Limit instead. Breaking Strength is the average force at which the product, in the condition it would leave the factory, has been found by representative testing to break, when a constantly increasing force is applied in direct line to the product at a uniform rate of speed on a standard pull testing machine. Proof testing to twice the Working Load Limit does not apply to hand-spliced slings. REMEMBER: Breaking Strengths, when published, were obtained under controlled laboratory conditions. Listing of the Breaking Strength does not mean the Working Load Limit should ever be exceeded.

DESIGN FACTOR (sometimes referred to as safety factor) An industry term usually computed by dividing the catalog Breaking Strength by the Catalog Working Load Limit and generally expressed as a ratio. For example: 5 to 1.

SHOCK LOAD A load resulting from rapid change of movement, such as impacting, jerking, or swinging of a static load. Sudden release of tension is another form of shock loading. Shock loads are generally significantly greater than static loads. Any shock loading must be considered when selecting the item for use in a system. AVOID SHOCK LOADS AS THEY MAY EXCEED THE WORKING LOAD LIMIT.