New composite yarn developed for Slingmax-TPXC Twin-Path Extra slings

By Don Pellow, P.E. Engineering Consultant

win-Path slings impacted the high density filaments to follow. world of the rigging industry But development and curiosity did Tseveral years ago, as they have not lie dormant at Slingmax. Following revolutionized the sling industry. With thousands of hours of testing and their light weight, high capacity development, plus field performance advantages over other types of slings, evaluations, Slingmax developed its they have found their way into every own optimum high strength area of lifting in many countries. The combinations for use in the fabrication innovative design and use of special of the Twin- Path slings. This new yarn high density, high strength have is a composite known as K-Spec, which played a key role in furthering the ad- Photo #1 is a combination of Technora and vancement of large and difficult lifts Spectra fibers. These combined fibers found in every type of industry. But markets, including that of sling (Photos #1 & #2) provides extremely today, another giant leap is evident in fabrication. This unusually strong high strength and low elongation along the new and improved Twin-Path fabric was meeting equivalent tensile with superior resistance to abrasion, Extra Sling with Covermax (TPXC), strengths of steel, while weighing only fatigue and chemical attack. These available through Slingmax. about 10% as much. After several years combined fibers are wound into strands The use of synthetic fibers and of using in round bodied slings, which then form the load bearing materials in the fabrication of slings other hybrids of high strength fibers elements of the TPXC slings. Continu- began in the 1930’s with the develop- were being developed and introduced, ous testing and evaluation has also ment of the , , such as Technora, Spectra, enlightened sling manufacturers and and polypropylenes. The and from manufacturers nylons and polyesters have found great around the world. Each of these fibers usage in manufacturing of synthetic are significantly greater in strength flat bodied and round-bodied slings, than previously known synthetics, yet particularly since the 1970’s. In fact, each has its own specific properties and the first Twin-Path slings, patented in characteristics. So with the develop- 1989, incorporated the use of ment of these high strength synthetic as load bearing filaments as well as the fibers, the Twin-Path slings took a new outer tubular coverings. direction – that is, Kevlar was first In the 1960’s, Kevlar, a dramatically introduced as the new load-bearing new, high strength material from elements within the Twin-Path sling Dupont, made great inroads into many design, with use of some of these other Photo #2

Wire News & Sling Technology August 2002 1 EXHIBIT #1 fibers perpendicularly against a second TWIN-PATH® EXTRA COVERMAX SPECIFICATIONS strand of the same type of fibers were United States Canadian conducted. The abrasion cycles Rated Capacities (Lbs.) 5-1 D/F Patent #4,850,629 Patent #1,280,458 continued until at least one strand Choker Vertical Basket Hitches Twin-Path® Approximate Approximate Extra Covermax 0° 60° 45° Weight Body Width failed. The load used to compress these Stock No. (Lbs. per FL) (Inches) (Bearing-Bearing) strands was based upon about 3% of TPXC 1000 8,000 10,000 20,000 17,320 14,140 .31 3" the known breaking strength of the TPXC 1500 12,000 15,000 30,000 25,980 21,210 .40 3" TPXC 2000 16,000 20,000 40,000 34,640 28,280 .55 3" fiber strand. The polyester strands TPXC 2500 20,000 25,000 50,000 43,300 35,350 .65 4" failed after 1,574 cycles, while the K- TPXC 3000 24,000 30,000 60,000 51,960 42,420 .80 4" Spec fibers, tested under identical TPXC 4000 32,000 40,000 80,000 69,280 56,560 1.12 5" TPXC 5000 40,000 50,000 100,000 86,139 70,700 1.50 5" conditions, failed after 8,672 cycles. TPXC 6000 48,000 60,000 120,000 103,920 84,840 1.60 5" Technora fibers also perform much TPXC 7000 56,000 70,000 140,000 121,240 98,980 1.68 6" TPXC 8500 68,000 85,000 170,000 147,220 120,190 1.85 6" better at elevated temperatures than TPXC 10000 80,000 100,000 200,000 173,200 141,400 2.20 6" other high strength fibers, as well as TPXC 12500 100,000 125,000 250,000 216,500 176,750 3.00 8" TPXC 15000 120,000 150,000 300,000 259,800 212,100 3.36 8" and polyester. Although the TPXC 17500 140,000 175,000 350,000 303,100 247,450 4.00 10" recommended maximum temperature TPXC 20000 160,000 200,000 400,000 346,400 282,800 4.37 10" TPXC 25000 200,000 250,000 500,000 433,000 353,500 5.50 11" of 180 degrees Fahrenheit is listed in TPXC 27500 220,000 275,000 550,000 476,300 388,850 6.90 11" catalogs and applicable standards, TPXC 30000 240,000 300,000 600,000 519,600 424,200 7.50 12" testing by shows Technora still PLEASE NOTE: Capacities shown include both paths and are for one complete sling. Ratings based on diameter one-half the sling width. DO NOT EXCEED RATED CAPACITY DO NOT EXCEED RATED CAPACITY retains up to 80% of its strength when held at 482 degrees Fahrenheit (Exhibit #5). Chemical exposure tests of Spectra and Technora reveal users to additional benefits, such as The extra high strength achieved excellent resistance to deterioration by light weight per loading capacity; cost from the K-Spec fabric in conjunction acids, alkalis and salt water (Exhibit efficiency and minimum creep under with Covermax tubing is reflected in #6, #7 & #8). Therefore, the composite load. the catalog rated capacity chart K-Spec material has superior resis- (Exhibit # 1). The Technora is a para- EXHIBIT #2 tance to chemicals, and when exposed fiber developed by Teijin and to such conditions such as salt water, FIBER ON FIBER ABRASION has 7 times the strength of steel per acids, alkalis and organic solvents for TESTING unit weight. The Spectra is a high six months, it still retained 100% of its SEPTEMBER 14th, 1996 density polymer manufactured by original strength. These tests were to determine the Allied Signal and has 10 times the An extra value of TPXC slings which difference between K-Spec core yarn strength of steel per unit weight. is oftentimes overlooked is the and polyester core yarn as used in Technora has excellent abrasion and Covermax outer covering. Slingmax SLINGMAX® rigging products. bending fatigue resistance as compared has spent considerable time and energy The yarns were each weighted to tootherhighstrengthfibers.For in working with suppliers to develop 2.7% of their breaking strength. They example, abrasion of the Technora the optimum covering providing were water and air cooled so that there fibers when tested against itself lasted strength and flexibility, while provid- would be no deterioration caused by almost three times as long before ing resistance to abrasion, cutting and heat. The polyester has a breaking failing as did other high strength fibers chemical attacks. The Covermax strength of 600 lbs. in a sling and was tested in an identical manner. The tubing is a bulked nylon construction weighted to 16 lbs. The K-Spec was composite K-Spec fibers perform even which provides these features along weighted to 48 lbs. The test consisted of better than Technora, outlasting it by 3 with reduced stretching under load. raising and lowering this load through to 1 (Exhibit #2). In bending fatigue, Photograph #3 shows a cutaway of both a 2" arc consisting of a loop of the same the Technora retained 52% of its Covermax coverings over the inner load material. This is a very severe test and original strength after 2000 cycles, as bearing K-Spec fibers. Field results it is highly unlikely that similar con- compared to only 36% strength of other from actual usage show that the ditions would ever be present in the high strength fibers (Exhibit #3). When field use of these products. Technora is combined with Spectra, the resultant is K-Spec, which has similar 9000 - results in bending fatigue as noted for EXHIBIT #3 8000 - • K-SPEC Technora. Twin-Path slings made with Characteristics of Technora® K-Spec outperform previously manu- 7000 - factured Twin-Path slings with Kevlar; 6000 - and compared to wire rope slings, Fatigue resistence (2) Bending fatigue resistence CYCLES 5000 - TO Twin-Path slings with K-Spec far FAILURE Retension of tensile strength 4000 - outdistance wire rope slings in cyclical loading tests (Exhibit #4). Technora® 52% 3000 - • A2 ARAMID The abrasion resistance of the K- PPTA 36% 2000 - • POLYESER Spec yarns is also far superior to the Roller Sample cord : 1670T/1X2 1000 - • A1 ARAMID previously used polyester fibers. This Bending conditions : fact has been established by laboratory Roller diameter 10mm D/d 15 FIBER ON FIBER ABRASION testing and by performance evaluation Yarn cord TESTS Load 1.8kg in actual lifting conditions. Tests Number of cycles 2,000 SEPTEMBER 1996 consisting of abrading one strand of

2 Wire Rope News & Sling Technology August 2002 EXHIBIT #4 FATIGUE TEST SUMMARY OCTOBER 1997 Product Description Actual Tension Test % of # of Retained Pin Breaking Strength Breaking Member Load Ultimate Cycles Strength Size asa%of Strength Catalog Strength

Flemish Eye6x25IWRCEIP 68,000 Wire Rope 20,000 29% 29,407 0 2" 0% Wire Rope Sling Steel Sleeves

TPXC 1,000 x 11' 60,300 Kevlar® 20,000 33% 55,148 0 2" 0% Photo #5 Twin-Path® Extra 3 Strand

K-2,000 x 6' Single-Path 100,000 Kevlar 30,000 30% 50,000 86,500 2" 86.5% Single-Strand TPXC 2,000 x 6' Twisted Twin-Path® Extra 100,000 K-Spec 30,000 30% 50,000 105,500 2" 105%

Note: 1. Clearly the K-Spec gives the best results 3. 3 Strand Kevlar® suffers from yarn on yarn abrasion 2. Wire Rope suffers from severe fatigue 4. Single strand twisted Kevlar® shows less abrasion but is rapidly declining in ultimate strength. The TPXC with K-Spec is the only sling in the world that does not lose strength as a result of use. Photo #6

The Covermax material shows only a few of the outer fibers snagged after 10 cutting cycles but none were cut (Photo #5). After 46 repetitions of cutting cycles, the Covermax fibers begin to be cut (Photo #6); and after 56 cycles of cutting, the internal load bearing K- Spec fibers are exposed (Photo #7). Photo #7 The superior characteristics of TPXC Photo #3 EXHIBIT #5 Characteristics of Technora®

Graph 11 Heat resistance ofTechnora® for long periods

100 180°C

80 200°C Photo #8 60 Photo #4 250°C 40 slings have been proven by hundreds of

Covermax tubing has enhanced Retention of strength (%) 300°C tests and ongoing research and 20 longevity of the TPXC slings. One 350°C development. But how do the overall outstanding example is that of the 0 physical properties of TPXC slings 1 10 100 1000 slings used in a Toyota factory, where Time (hrs.) compare to the competitive slings in TPXC slings made more than 30,000 the marketplace? First, by comparing lifts without rupturing of the the properties of TPXC slings to other Covermax tubing. types of slings available, the advan- EXHIBIT #6 Additionally, Covermax is much tages of TPXC slings immediately more resilient and resistant to cutting Strength Retention After Chemical Immersion becomes obvious. Exhibit #9 shows that (% Retention) than other types of sling covers. Spectra Fiber TPXC slings have the lowest Laboratory tests using repetitive Agent 6 Months 2 Years weight/strength ratio of all known cutting motions have shown that Sea Water 100 100 slings, providing a significant advan- Covermax is many times more difficult Hydraulic Fluid 100 100 tage in handling and reduced rigging to severe than conventional nylon or Kerosene 100 100 time. Exhibit #10 graphically displays Gasoline 100 100 polyester coverings. A knife edge with a the comparable stretch characteristics Toluene 100 96 of TPXC slings to those fabricated from cutting pressure of 10 pounds was Glacial Acetic Acid 100 100 repeatedly run across the same 1M Hydrochloric Acid 100 100 wire rope, chain and nylon. TPXC location of both a Covermax jacket and 5M Sodium Hydroxide 100 100 slings will stretch about 1% at rated a comparative polyester jacket. After Ammonium Hydroxide (29%) 100 100 capacity, and exhibit approximately 3% 10 repetitions of cutting, the polyester Perchloroethylene 100 100 elongation at ultimate breaking material had been cut to where the load 10% Detergent Solution 100 100 strength. Wire rope stretches about bearing yarns are exposed (Photo #4). Clorox 91 73 this same 1% at rated capacity, while

Wire Rope News & Sling Technology August 2002 3 EXHIBIT #7 added assurance of complete inspection lifted with a TPXC sling weighing

® in a minimum amount of time. about 100 pounds. This weight Characteristics of Technora TPXC slings play a major role in reduction is not only significant in the

Graph 12 Acid resistance of Technora® enhancing rigging safety. A notable areas of safety and cost reduction in example where safety is of primary man-hours, but TPXC slings allow

® 100 Technora concern is that of attaching slings from greater loads to be lifted with the crane a crane hook to a load at elevated by reducing the weight of the rigging 80 heights where handling techniques and below the hook. 40% H24 SO aq. at 95°C 60 personnel are limited. A load requiring Another intangible advantage of a 500 pound wire rope sling to be TPXC slings is their cleanliness, 40 attached can be dangerous, time particularly when compared to wire

Retention of strength (%) 20 PPTA consuming and may be impossible at rope slings. This is not only a personal PPTA: Poly-(p-phenylene terephthalamide) these heights. This same load can be hygiene matter, it can be an environ- 0 20 40 60 80 100 Time of immersion (hrs.)

EXHIBIT #9 displaying about 4%-5% elongation at COMPARISON OF INDUSTRY SLINGS ultimate breaking strength. So the Sling Type Size Rat. Cap. Wt/Ft. % Elon. @ Max. Temp. behavior of TPXC slings is very (lbs.) (lbs.) Rat. Cap. ( F.) comparable to wire rope slings under load. However, synthetic web and Twin-Path Extra TPXC 6000 60,000 1.6 1.0 180 round bodied slings behave much Kevflex (Kevlar) Ken 800 66,000 1.9 1.0 250 differently. Nylon web slings stretch approximately 6% and polyester web Nylon Web 3, 4-Ply, 4" 54,600 4.0 8.0 194 slings stretch about 3% at rated Round-Bodied (Poly) EN 800 66,100 3.0 6.0 194 capacity. Polyester round bodied slings will stretch this same 3%, unless the Wire Rope 1/7/8", EIP 64,000 6.5 + Eyes 1.0 400 polyester is braided into a multi-part sling, where elongation at rated Chain (Grade 100) 1" 59,700 10.7 0.5 600 capacity can reach 9%. This TPXC property of minimum stretch under load provides better load control; permits minimum overhead clear- EXHIBIT #10 ances; and allows more predictability in determining resultant sling angles Destruction test results of various Lifting Slings during lifting. JULY 31, 1996 Scope: To demonstrate the difference in elongation and the types of failures. The advantages of high strength and Slings used: (All slings having a length of 12 ft) light weight are dramatic in reducing Type WLL (DF 5:1) MBS Breaking Strength the time involved in rigging and handling, thus leading to reduced 1) 1-1/8" diameter wire rope sling, overall labor costs. Slings can be 6x36 IWRC, IPS, RRL 22,000 lbs 110,000 lbs 114,390 lbs installed in less time and with fewer 2) TWIN-PATH® EXTRA sling, personnel, and inspection time is Type TPXC 2000 20,000 lbs 100,000 lbs 124,540 lbs greatly reduced due to ease of han- 3) UNI-WEB™ Nylon Web Sling dling. Proprietary inspection tech- Type EE2-908-3 22,700 lbs 113,500 lbs 129,970 lbs niques of Slingmax TPXC slings is an 4) 5/8" Alloy Chain Sling with Coupling Links and Master Links 18,100 lbs (I) 72,400 lbs 67,240 lbs Note: 1) WLL based on DF 4:1 only. Sling broke premature due a link failure. Elongation recorded is lower than normally expected. A second test on August 1, 1996 in which the ram speed was considerably LOWER, a sling made from the same batch of chain broke at 73,980 lbs. EXHIBIT #8 This information was passed on to the chain manufacturer with the request for an explanation. Stress Characteristics of Technora® Wire Rope Sling Nylon Web Sling

Graph 13 Alkali resistance of Technora®

Twin-Path® Extra Sling 100 Technora® Chain Sling 80

60 10% NaOH aq. at 95°C

40

Retention of strength (%) PPTA 20 Strain Wire Rope Eleongation - 2-1/2" 0 Twin-Path® EXTRA Elongation - 3" 20 40 60 80 100 Chain Sling Elongation - 18" Time of immersion (hrs.) Web Sling Elongation - 28"

4 Wire Rope News & Sling Technology August 2002 mental concern. The lubricants applied and each sling had 25% of the core based upon industry testing. Manufac- to the wire rope for lubricity and yarns cut. The material used for turers limit the lift cycles to 500 corrosion protection can sometimes be tension members in both slings was K- because of concerns over fatigue and harmful to the environment. So with Spec fiber. The calculated breaking internal wear. TPXC slings have no TPXC slings, both the hygiene and strength of each sling with no cut limitation on number of lifts since environmental problems are elimi- strands was 125,000 pounds. The testing shows no degradation after nated. Single Path sling was pulled to thousands of lifts. Other significant advantages of the ultimate breaking strength, and (7) Twin-Path slings provide TPXC slings are ease and completeness ruptured at 65,400# (52% of calculated redundant back-up protection by of inspection. With the increase in strength). The Twin Path sling pulled having two independent connections weights of loads being lifted and in two at 114,100# (91% of calculated between the hook and the load, number of lifts being made, safety is a strength).” whereas single path slings have no major player in determining the type of This dramatic difference makes it backup. This redundancy of Twin-Path sling to use. ASME B 30.9 and applica- quite clear that the efficiency of a Twin- design allows holding of the load at ble OSHA regulations lists procedures Path sling is far superior to a Single high design factors under the condition to follow when inspecting various types Path configuration. The twin path of having one path cut.....not the case of slings. All of these inspection design provides higher strength with single bodied slings. standards have been established by efficiency by allowing the fibers to more (8) Round bodied polyester slings thousands of tests, research, and equally carry a proportionate share of weigh about 2.3 times that of Twin- comprehensive evaluation. However, the total load by dispersing the fibers to Path slings for equivalent lifting TPXC slings takes inspection to a locations closer to the bearing surfaces. capacities. This is quite a savings in higher level. TPXC slings not only In a single path sling, the outer fibers time to rig and offers much easier incorporate the normal inspection are distanced further from the load handling with fewer personnel. criteria, but add the extra precaution- bearing area, thus causing more The advantages of TPXC slings are ary patented “tell-tails” and “fiber disparity among the load bearing very clear and have been proven by optics” technologies (Photos #8). These fibers. testing and performance. Like all easy to use inspection techniques can (2) As discussed, Twin-Path slings slings, precautionary measures must be quickly accomplished and provide provide additional inspection tech- be taken and correct usage practices additional assurance that the sling has niques which provide safer lifting must be followed. The instructions and been thoroughly inspected. practices and makes the user more warnings on the use of these slings, as The tell tails, one in each independ- knowledgeable of the sling conditions. listed on the sling tags and in the ent sling path, indicate if a sling has Round bodied slings have no “tell tails” brochures, must be read, understood been overloaded. These exposed tails of to indicate overloading and no “fiber and followed. Always inspect slings internal fibers are preset to an exposed optic cables” to indicate internal before each use in accordance with length, and if they are found to be damage. ASME B 30.9 standards. Notably, shorter after use, or have pulled back (3) The new outer Covermax inspection is faster and more complete into the body of the sling, this is an covering of Twin-Path slings provides with TPXC slings than with any other indication of overload. The fiber optic superior wearing properties and type of sling. cables will transmit light throughout enhanced resistance to cutting, Because one of the primary causes of the entire length of the sling if no abrasion and chemical attack over the synthetic sling failures is cutting or damage has occurred. However, the covers of competitors’ round bodied abrasion, it is recommended that transmission of light will be termi- slings. corner protectors or “softeners” be used nated if the sling has experienced (4) The K-Spec filaments of the if the slings are to be exposed to sharp significant crushing, heat damage, Twin-Path slings provides much less edges, small bend radii or rough chemical attack or cutting of the load stretch than polyester filaments of surfaces. Under heavy loading bearing fibers. Both of these additional some round bodied slings. Twin-Bodied conditions, a metal/manufactured inspection features benefit the end user slings stretch approximately 1% at rated protector or equivalent should be in helping to prevent accidents. rated capacity, whereas polyester used. An additional product from the The advantages that TPXC slings slings stretch 3%, and braided polyes- Slingmax group is a patented corner have over wire rope, chain and other ter slings stretch up to 9%. protector specifically designed for lower strength synthetics may now (5) The manufactured length synthetic slings. This product has seem fairly obvious. But how do these tolerances of Twin-Path slings are proven its worth in handling heavy TPXC compare to round bodied slings easily held to a maximum of +/- ½", loads with small radii corners without using other high strength synthetic which is far superior to the round any evidence of cutting, abrasion or fibers? Comparison of these slings bodied construction, where length other type of damage. reveal several important facts as noted tolerances, at best, are +/- 1", but Overall, Slingmax offers the most below: mostly much greater. Braided polyes- advanced and safest slings available (1) The twin-body configuration, ter, round bodied slings list length today. With the availability of TPXC using an identical number of fibers, tolerances of +/- 5%. There is no dispute slings, no other sling offers the high and compared to a single body design, regarding the superiority of Slingmax strength, low weight capabilities; long provides higher strength. Recent test Twin-Path slings when it comes to service life; and enhanced resistance to results state: meeting close tolerances. chemical attacks, cutting and abrasion. “A single Path round sling and a (6) Round bodied slings using Kevlar The TPXC slings are the “high tech” Twin Path sling were fabricated with as the load carrying fibers are limited slings available today and are quickly the same number of core yarn strands, to the number of lifts they can make, proving to be the slings of choice. o

Wire Rope News & Sling Technology August 2002 5 Contacts: www.slingmax.com - 800-874-3539 - fax 610-494-5835 - [email protected]

6 Wire Rope News & Sling Technology August 2002