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 fiber 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 fibers 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 Kevlar 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 nylons, polyesters, such as Technora, Spectra, Vectran enlightened sling manufacturers and polyethylenes and polypropylenes. The and Twaron 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 polyester 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 Rope 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" nylon 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 Teijin 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 aramid 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.