nominal strength of wire rope quotation

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Understand that most of the people out from the industry always face the problem of having no idea with the terms of wire rope when receiving quotation. In this update, we will explain in the most simple way and hopefully it is applicable to anyone.

6X36 = Construction of wire rope (There are quite a lot different constructions available for different application for example like, 6X25, 6X29, 6X31, 4X39, 19X7, 8X26 etc.)

RHOL = Right hand ordinary lay, it is the wire lay direction and very important to select the right direction of wire when dealing with multi-reeving, crane and hoist application.

EIPS (1960) = Extra improved plow steel and 1960 stands for the tensile strength 1960N/mm2. The figure is telling you the grade of wire rope, lower or higher tensile strength will result in different breaking strength.

UNGALVD = Ungalvanized, the surface finishing of wire rope. Galvanized and Ungalvanized are the basic surface finishing selection with different grade of lubrication.

G411 THIMBLE EYE = Thimble eye model. Soft eye will be stated with the effective working length and the size of soft eye is based on nominal diameter x 15times according to EN131411 standard.

MECH SPLICED = Mechanical splicing is the process of using hydraulic pressure to press the aluminum sleeve or metal sleeve and a loop is formed. This phrase is always telling you the terminal of both end wire rope. It can be plain, socketed, fuse tapered or eye formed.

Wire rope could have a lot of variation upon the application which I will cover in the next update. The essay above is good enough to tell the basic and hope it helps for procurement department while dealing with steel wire rope. Last but not least, selecting the right wire rope is crucial to your company"s long term expenditure and safety purposes. Do not take the risk because of cheap.

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.

When you purchase line you will buy it by its diameter. However, for purposes of the USCG license exams, all lines must be measured by circumference. To convert use the following formula.

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…

Actual operating loads may vary. NEVER exceed the recommended design factor of 20% of catalogue strength. Wire Rope must have the strength required to handle the maximum load plus a design factor. The design factor is the ratio of the breaking strength of the rope to the maximum working load.

CONSTRUCTION: Expressed in numbers of strands x number of wires. 6 x 25 indicates that the wire rope consists of 6 strands, which in turn have 25 individual wires.

How to measure (or caliper) a wire rope correctly. Since the "true" diameter (A) lies within the circumscribed circle, always measure the larger dimension (B). Actual diameter can be 5% larger than nominal wire rope diameter.

There are numerous ways to cut wire rope - use only appropriate tools specifically designed to cut wire rope. Safety goggles and work gloves must always be worn. Observe other precautions peculiar to the tools used. Wire rope should be properly seized on both sides of the cut with wire or strand. Seizing wire diameter and the number and length of the seizings will depend on the diameter of the wire rope, and whether or not it is preformed.

Since wire rope is a machine with many moving parts, it requires careful installation and breaking in procedures for maximum safety and long service life. After proper installation, allow the wire rope to run through a cycle of operation at a very low speed. Keep a close watch on the wire rope, its attachments and any working parts such as sheaves, drums, rollers, etc. to make certain that the wire rope runs freely. If no problems appear at this stage, run the wire rope through several cycles of operation under light load at reduced speed. This procedure allows the component parts of the new rope to make a gradual adjustment to the actual operating conditions.

Wire rope will develop 100% efficiency, that is, break at or above minimum acceptance strength (not less than 2 1/2% below nominal breaking strength) under controlled laboratory conditions. Once fittings such as sleeves, clips, sockets, etc. are attached and/or the wire rope passes over a curved surface such as sheaves, pins, etc. its strength is decreased. In the case of wire rope passing over a curved surface this decrease in strength depends on the severity of the bend. In the case of wire rope fittings, the decrease in wire rope strength will depend on the type of fittings used. The wire rope efficiency usually ranges from 70% - 100%. For more detailed information consult the strength efficiency of wire rope table on page 86. Note, that hand spliced wire rope, while not using any fittings, has less efficiency than properly flemished and swaged wire rope. There are other factors, depending on the application of wire rope, that can cause a decrease in nominal wire rope strength. They must be considered when choosing a design factor. Refer to the Wire Rope Users Manual and/or other qualified sources for details.

Wire rope is an elastic member; it stretches or elongates under load. This elongation can be permanent or recoverable. The extent of elongation will depend on the wire rope used and the design factor chosen. While it may be acceptable for many wire rope uses to neglect its elastic properties, they are of critical importance for some uses. When in doubt about the importance of wire rope elongation consult professional help. Pre-stretching wire rope will only remove some of the constructional stretch and will not totally eliminate elongation under load.

Installation of wire rope on a plain or grooved drum requires a great deal of care. Make certain the wire rope is properly attached to the drum. Keep adequate tension on the wire rope as it is wound onto the drum. Guide each wrap as close to the preceding wrap as possible, or follow the groove in case of a grooved drum. No blanket recommendations can be given concerning direction of winding, desirable drum diameter, fleet angle, etc. Consult the Wire Rope Users Manual for this and other important technical information.

Note: The maximum CAPACITY, WORKING LOAD LIMIT (WLL), or LINE PULL of the rope usually is 1/5 of the below stated values. For specific information consult the standards applicable to your rope application.

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A 6X19 class wire rope contains 6 strands with 16 through 26 wires per strand. Our 6x19 class typically has either 19 (6X19) or 26 (6X26) wires per strand. It is a general purpose rope most commonly used for wire rope chokers and other rigging. 6X19 and 6X26 offfer great abrasion resistance and crush resistance when spooling.

A 6X37 class wire rope contains 6 strands with 27 through 49 wires per strand. Our 6X37 typically has 36 wires per strand. It is a general purpose wire rope with excellent flexibility for spooling. With the smaller wires per strand, the trade off for excelelnt flexibility is reduced abrasion resistance.

IWRC (Independent Wire Rope Core) wire ropes offer more crush resistance when spooling while FC (Fiber Core) wire ropes offer more flexibility. FC wire ropes are not as crush resistant when spooling compared to an IWRC wire rope.

The 6 x 19 classification of wire ropes includes standard 6 strand, round strand ropes with 16 through 26 wires per strand. The 6 x 36 classification of wire ropes includes standard 6 strand, round strand ropes with 27 through 49 wires per strand. All rope of the same size, grade and core have the same nominal strength and weight per foot. Different constructions within each classification differ in working characteristics. These characteristics must be considered whenever you are selecting a rope for a specific application.

Although Carl Stahl Sava Industries is known for producing the world’s tungsten, stainless steel and galvanized steel mechanical cable, exotic wire rope materials remain a less common, yet critical member of our family of cable offerings. Nitinol, titanium, Vitallium®, Inconel® and Molybdenum round out Sava’s compliment of specialty mechanical cable materials...

This compacted wire rope construction is available in both galvanised and ungalvanised finish with either ordinary or langs lay. The construction family includes 32X7, 35X7 and 37X7. Depending upon your requirement for higher breaking load or better wear characteristics, these wire ropes are available in different finishes and lubrications as well as being available with plastic impregnated or in compacted constructions.

The 7x7x7 Cablaid Wire Rope is galvanized and preformed – good general purpose construction for strength and flexibility. Can be used over pulleys. TO BE USED FOR MECHANICALLY SWAGED SLINGS ONLY. Do not use for hand-spliced assemblies or for general purpose operating rope.

These ropes offer greater strength than standard ropes of the same diameter while providing greater resistance to drum crushing, scrubbing and similar wear. When producing our 6×26 Swaged rope, we utilize a rotary swaging process to produce a compact cross-section with minimum voids and greater surface area on outer wires.

For use in an application where a single-part hoist rope is used to lift a free load – or where rotation-resistant properties are essential for rope performance.

Our 8 strand constructions are regular lay and either 19 Seale or 25 Filler Wire. The size relationship between strands and cores gives these ropes increased bendability over six strand ropes of the same diameter.