wire rope load calculator manufacturer

Wire rope is also known by many other names, such as: wire, multi-strand wire, flexible wire, cable, cord, steelcord, etc. but it is essentially a collection of small filaments wound around each other in a manner that largely retains its shape when bent, crushed and/or tensioned.

It is a system for significantly increasing the strength and flexibility of steel wire and is used in almost every important application we see around us. For example: suspension bridges, tyres, brake and accelerator cables (in cars), high-pressure flexible pipes, lifting and rigging cables, electrical conductors, etc. and it comes in many different forms. Fig 2 shows just a very small sample of available designs.

With minor variations, the generally accepted method for designating a wire rope construction in the industry is by describing it numerically. For example:

Whilst "IWRC" wire ropes offer a slightly greater tensile capacity (≈7%) than those with fabric or polymer fillers, the additional strength does not come from the tensile capacity of the core filaments but from improved dimensional stability under load. And whilst they are also much more resistant to crushing, they are stiffer than fibre core ropes and therefore not recommended for applications where tension occurs under bending.

Warrington (Fig 1) is a parallel lay construction with an outer layer comprising wires of alternating large and small diameters, each outer layer having twice the number of wires as the layer immediately beneath. The benefit of this design is to increase packing and therefore strength density, however, unless the different diameter filaments are of the same strength (unlikely), this construction is limited by the strength of the weakest filaments.

Seale (Figs 1 & 2 6x36) is also a parallel lay construction but with the same number of wires in each wire layer. All the wires in any layer are the same diameter. This is an alternative to the Warrington construction, with similar benefits and disadvantages.

Regular lay constructions are used much more widely (than Lang lay) because they have excellent structural stability and less tendency to unwrap under tension (see Rotating vs Non-Rotating below). However, because it has a knobbly (undulating) surface it will wear both itself and any surface over which it is run much more quickly than Lang lay wire rope.

Lang lay constructions have a flatter surface than regular lay constructions giving them better resistance to wear and bending fatigue, especially when made from flattened (elliptical) filaments. They are, however, much less structurally stable and subject to birdcaging if the wire rope is over-bent or twisted against its wrapped direction.

"Regular Lay", multi-strand constructions are normally subject to slightly less rotation under tension (than Lang lay) due to the opposite helical direction of the filaments (within the strands) and the strands (within the rope), however, you can improve their rotation characteristics still further by;

Fillers (Fig 2) may be fabric, polymer or even smaller diameter filaments (e.g. 6x36). Whilst they contribute little to the tensile strength of wire rope, they can significantly; improve performance under bending (fabric and polymer cores only), reduce axial growth, reduce rotation in rotation-resistant constructions, improve structural stability and increase fatigue life.

This filler material should not be included in strength (tensile capacity) calculations, but must be included in those for axial stiffness (extension). If it is ignored, your calculations will reveal excessive extension as the wire rope collapses.

Suspension bridges tend to be constructed from densely packed, single strand plain "Wire Rope" constructions using large diameter galvanised filaments. Little heed is paid to rotational resistance as strength is paramount and once tensioned, they should remain in that loading condition for their design life.

Lifting & winching normally require wire ropes of good flexibility and fatigue resistance. Therefore they tend to be similar to 6x36 but with fibre core instead of the IWRC in Fig 2

Remote operating cables such as hand-brakes and accelerators on cars normally only work in tension so they need to be strong but not necessarily stiff (as they are fully contained in reinforced outer sheaths). These tend to be manufactured from large diameter "TyreCord" or small diameter single-strand "Wire Rope".

Wire rope does not obey Hooke"s law. Therefore, you cannot accurately predict how much it will stretch for any specified force. This unpredictability applies to any section removed from the same manufactured length of cord and even between cords produced to the same specification but by different manufacturers.

CalQlata has decided that the accuracy of axial stiffness (EA) of wire rope falls outside its own levels of acceptability and therefore does not include it in the wire rope calculator. The extension calculated in the Wire Rope calculator (δLᵀ) is based upon the effect of axial tension on packing density. It is therefore important that core material is not ignored when using the calculator to evaluate this characteristic.

Wire rope does not obey Hooke"s law. Therefore, you cannot accurately predict how much it will twist for any specified torque. This unpredictability applies to any section removed from the same manufactured length of cord and even between cords produced to the same specification but by different manufacturers.

CalQlata has decided that the accuracy of torsional stiffness (GJ) of wire rope falls outside its own levels of acceptability and therefore does not include it in the wire rope calculator.

1) No wire rope calculator, whether dedicated or generic, will accurately predict the properties of any single construction under a wide range of loading conditions

2) No wire rope calculator, whether dedicated or generic, will accurately predict any single property for a range of constructions under a wide range of loading conditions

The only wire rope that can be reliably analysed is that which is used for suspension bridges, because; it comprises a single strand, is very densely packed, has negligible twist, contains filaments of only one diameter, is never subjected to minimum bending and every filament is individually tensioned.

There is a very good reason why manufacturers do not present calculated performance data for construction or design proposals, because even they cannot accurately predict such properties and quite rightly rely on, and publish, test data.

During his time working in the industry, the wire rope calculator"s creator has seen, created and abandoned numerous mathematical models both simple and complex. He has gradually developed his own simplified calculation principle based upon his own experience that still provides him with consistently reliable results of reasonable accuracy.

The purpose of CalQlata"s wire rope calculator is to provide its user with the ability to obtain a reasonable approximation for a generic construction, after which, accurate test data should be sought from the manufacturer for the user"s preferred construction.

The calculation principle in the wire rope calculator is based upon changes in the properties of the wire rope that occur with variations in packing density under tension

Bearing in mind the above limitations CalQlata can provide the following assistance when generating (manipulating) the wire rope calculator"s input data and interpreting its output

Alternatively, for wire rope with multiple filament diameters, you need to find an equivalent diameter with the following proviso; you must enter the minimum filament yield stress (SMYS)

It is expected that apart from fillers, all the material in the wire rope will be identical and therefore have the same density, i.e. using different materials will result in less than "best" performance. However, if such a construction is proposed, you can calculate an equivalent density as follows:

It is expected that apart from fillers, all the material in the wire rope will be identical and therefore have the same tensile modulus, i.e. using different materials will result in less than "best" performance. However, if such a construction is proposed, you should enter the highest tensile modulus.

The wire rope calculator simply adds together the total area of all the filaments and multiplies them by the SMYS entered, which represents a theoretical maximum breaking load that would exist if this load is equally shared across all of the filaments and the lay angles have been arranged to eliminate localised (point) loads between adjacent filaments.

If the wire rope has been properly constructed it is likely that its actual break load will be greater than 80% of this theoretical value. However, given the vagaries of wire rope construction, the actual break load can vary considerably dependent upon a number of factors. CalQlata suggest that the following factors may be used to define the anticipated break load of any given construction:

The axial stiffness and strain under load will be affected by this value, hence the reason why the most reliable (predictable) constructions tend to be minimum [number of] strands and single filament diameter. The Warrington and Seale constructions and combinations thereof tend to provide the highest packing density (but lowest flexibility) and there is little to be gained from using these constructions in more than single stranded wire rope as the benefit of high-packing density will be lost with no gain in flexibility.

The anticipated second moment of area of the wire rope at tension "T" due to deformation but insignificant flattening as it is assumed the wire rope will be bent over a formed (shaped) sheave or roller.

The anticipated tensile modulus of the wire rope at tension "T" due to deformation but insignificant flattening as it is assumed the wire rope will be bent over a formed (shaped) sheave or roller.

It is not advisable to induce this bend radius in operation due to uncertainties associated with wire rope construction, especially for dynamic applications. CalQlata suggests that a similar approach to that used for the break load (Fb) above also be applied here, i.e.:

A change in diameter will occur in all wire rope, irrespective of construction, until packing density has reached a limiting value. The value provided in the wire rope calculator is that which would be expected if the construction remains intact at the applied tension "T"

Unreliability of this value increases with complexity in wire rope due to its longitudinal variability and the increased likelihood of premature failure.

The accuracy of this data will range from about ±1% for wire rope with a single strand and a single filament diameter, up to about ±15% for constructions of similar complexity to OTR cord

A change in length of any wire rope will occur due to the fact that the packing density increases with tension. This is not, however, a linear relationship.

This can be an unreliable value as illustrated by tests carried out (by the author) on two pieces of wire rope supplied by the same well-known manufacturer both of which were cut from the same length, varied in tensile capacity by only 1.5%, but the tensile modulus (and strain at break) varied by 34%. Whilst this was an extreme case, significant variations have been seen in wire rope manufactured by a number of manufacturers.

Whilst the wire rope calculator does not calculate axial stiffness (see Calculation Limitations 9) above), CalQlata can suggest the following rule-of-thumb that will provide reasonable results for most constructions at the applied tension "T":

Where: θ = the "absolute" sum of the average filament lay angle and the average strand lay angle⁽²⁾. Note; the angle of twist (θ) will reduce as tension approaches break load.

Whilst the wire rope calculator does not calculate bending stiffness (see Calculation Limitations 8) above), CalQlata can suggest the following rule-of-thumb that will provide reasonable results for most constructions at the applied tension "T":

Low complexity means single strand and single wire diameter. Medium complexity means multi-strand and single wire diameter. High complexity means multi-strand and multiple wire diameters.

Enter the diameter of the wire rope, in mm, into the calculator to determine the safe working load (SWL). This calculator is for education purposes only, follow manufacturing guidelines for true SWL values.

A safe working load of a wire rope is a measure of the total load or weight that a wire rope can safely support during operation. Values greater than the SWL could result in a failure of the rope.

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While it is virtually impossible to calculate the precise length of wire rope that can be spooled on a reel or drum, the following provides a sufficiently close approximation.

* This formula is based on uniform rope winding on the reel. It will not give correct results if the winding is non-uniform. The formula also assumes that there will be the same number of wraps in each layer. While this is not strictly correct, there is no appreciable error in the result unless the traverse of the reel is quite small relative to the flange diameter (“H”).

** The values given for “K” factors take normal rope oversize into account. Clearance (“x”) should be about 2 inches unless rope-end fittings require more.

Wire rope and chain are the important part of the hoist which are closely bound up with the safe work load, now let’s talk about how to calculate the SWL of ropes and chains.

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PFEIFER DRAKO wants to point out that the suitability and usability of the recommended PFEIFER DRAKO products also depend on the suitability of all other components of the elevator for this projected installation and its specifications accordingly. The determined data therefore has to be regarded as a suggestion not as a final elevator design calculation! It is imperatively necessary to do a final calculation regarding all relevant factors of influence. The calculated expected number of trips is the result of the influences of chosen elevator configuration on the chosen rope type. The basis for this calculation is the statistical data and the rope lifetime equations for running steel wire from taken from K. Feyrer, Wire Ropes, Springer Verlag 2018. The selectable rope types have the according PFEIFER DRAKO brand name. The calculation does not include a quality assessment of the products. The interaction of the chosen rope drive and the rope forces, caused by the applied masses but also further factors of the elevator (i.e. acceleration, rope force differences, friction) and the chosen rope construction is evaluated by means of an approved theoretical basis. Exact and smooth rope installation, good rope tensioning and sufficient re-lubrication must be guaranteed. The calculated data is not subject to be claimed as a legally binding statement for the end-user. It is to be seen as an indication based on the above described theoretical basis, which number of trips can theoretically be expected with the given configurations.

Have you ever wondered how much weight a wire cable can safely hold? It’s surprising how strong wire cables are. Although wire cables often have small diameters and look flimsy, their strength is impressive. Calculating how much weight a wire cable can hold is called a Safe Working Load (SWL), and involves a mathematical formula. The SWL is usually calculated by the manufacturer of the cable and is marked on the packaging to inform consumers. To ensure your safety, always take note of the SWL the manufacturer provides.

SWL can also apply to other lifting devices or components of lifting devices, such as a line, rope or crane. The SWL is also sometimes referred to as Normal Working Load or Working Load Limit. It is the mass that lifting equipment can safely hold without fear of breaking. The SWL or NWL is often a fifth of the Minimum Breaking Strength of the cable, although sometimes other fractions are used, depending on the manufacturer.

To calculate the SWL, you need to know the diameter of the cable or rope. While you may find this on the packaging, you can also calculate it manually by measuring it yourself. Ensure that you enclose all of the strands of rope when measuring the diameter, and measure from the top of one strand to the top of the strand which is directly opposite. If you’re worried about the accuracy of your measurements, conduct your measurements three times at different places on the cable, and use the average of your three measurements as the diameter of the rope.

Once you know the diameter of the rope, you can apply it to the formula, which is SWL = D2 x 8. D represents the diameter of the rope in inches. If you’re working with a 1.5-inch diameter cable, for example, then the formula would be SWL = 1.52 x 8 or SWL = 2.25 x 8. This calculation means the SWL of a 1.5-inch diameter rope is 18 tons.

Take note that most manufacturers will provide you with the SWL for their rope or cable under specific conditions. It’s important to use the SWL the manufacturer gives you. If you’re working with old rope or rope that is worn down, you may want to reduce the SWL of the rope by as much as half, based on the condition of the rope. You can also use the manufacturer’s Breaking Strength of the rope if it is available.

Block Division, Inc., has established through an accredited testing laboratory the capacity at which our products may be safely used. This may be defined as the safe working load limit, a chain or cable rope pulley block load calculation, or a force calculator.  The safe working load limit (mechanical advantage) is the maximum load in pounds which should ever be applied, and when the load is applied uniformly and in direct tension to a straight segment of wire rope.  By changing the degree of angle between lead and load angle, this also affects the stress on the block. The stress on the eye may be decreased by increasing the angle between the load and the lead angle.  See chart 1 and illustration below.

Safe Work Load Limit: This is the maximum load (in lbs.) which can be applied to the Block and which has been established by Block Division, INC. (Load Capacity)

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.

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.

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:

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.

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.