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Synthetic Slings, Ropes and Winch Lines 2011 Pennsylvania REC Key Man Conference
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The Good Old Days
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Chains and Wire Rope -Inexpensive -Durable -They work -Heavy, -Conductive -Wire rope kinks and cuts -Easy to damage the equipment
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Nylon-the First of the Common Synthetics Petroleum-Coal Based 1935 Toothbrush
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WW II Uses of Nylon Replace Silk for Parachutes
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WWII Use of Nylon Nylon Stockings
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Nylon Very Strong Good Value Degrades at 350 o F. Melts at 460 o F. Nearly 10% stretch at working load Absorbs moisture
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Polypropylene Made from Olefins Half of Nylon’s Strength Plastic Feel Lightweight-Floats Melts at 330 Degrees F. Inexpensive Will “Creep” with a sustained load Poor UV Resistance
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Polyester Synthetic Polymer As strong as Nylon Less Stretch than Nylon Less Water Absorption than Nylon Melts at 480 degrees F. Costs about the same as nylon
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Ultra High Molecular Weight Polyethylene (UHMWP) Trade names are Spectra or Dyneema (1980’s) Very high strength-3.5 times Nylon Very low stretch Floats Will “cold flow” Easier to shock load More expensive
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Aramid Fibers Kevlar-Technora (early 1960’s) Very low stretch Not as strong as UHMWP Used in body armor and FR Clothing Very high melting point- 800 degrees F. Absorbs moisture Expensive Abrasive
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Liquid Crystal Polymer Vectrus -1985 As strong as UHMWP Very little stretch 600 degree F. melting point Little moisture absorption Very expensive
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Making Thread from Fiber Times have changed…
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Webbing Manufacturing
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3 Strand Rope Oldest style
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Braided Rope No Twists-does not “unwind” when loaded No Hockling Less Stretch More design options
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Rope Braider
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Webbing and Rope Lifting Slings Versatile 5-1 Safety factor Lightweight Nylon and Polyester are inexpensive Available in high modulus fibers
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ANSI B30.9
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Sling Tags
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Sewn Splices-Eye Splices-Adjustables Splices are stronger than the body of the sling Hardware rated 5/1 Splices must be sewn with a contrasting color Fabricated eye splices should have a whipping or a tie on 3 strand Adjustable slings must have an appropriate bearing area and back- spliced end
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Methods of Hitching Loads Vertical Choker-Reduces capacity 30% Basket-Doubles capacity
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The Effect of the Angle
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Inspecting Web Slings Appropriate Tags Fuzzing Splice Integrity Broken Stitches Burns UV Degradation Cuts-Mechanical Damage Chemical Damage Hard or glazed surface
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Inspecting Rope Slings Appropriate Tags Fuzzing Splice Integrity-Broken whipping Mechanical Damage to adjacent pairs UV-chemical degradation Burns-thermal or chemical Hard or glazed surface Stiffness
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Tips for Using Synthetic Slings Avoid exposure to sharp edges-use pads No Knots-50% loss in strength Use appropriate lifting hardware Be aware of the lifting angles Balance the load Replace slings regularly Avoid shock loading
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Lifting and Pulling Lines A variety of constructions are available for different applications including: 3 Strand 8 Strand 12 Strand Double Braid Parallel core
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3 Strand Easy to manufacture Inexpensive Durable Stretches Unwinds when loaded
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8 Strand Easy to splice No twisting Straighter Lay Flattens under load
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12 Strand-Hollow Braid No Twisting Easy to splice Great for pulling lines
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Double Braid A rope in a rope Many manufacturing options Less flattening in a sheave Not the strongest option because of the angle
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Parallel Core Most efficient use of fiber-strongest Extremely durable Higher cost Harder to terminate
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1 Inch Diameter Double Esterlon vs. Maxi Braid Plus Double Esterlon 44,000 lb. avg. break 4% stretch at working load Balanced construction 35 lb per 100 feet Nearly 14% stretch at break Good energy absorption Priced as Nylon Maxibraid Plus 60,000 lb. avg. break Less than 1% stretch at working load Load bearing core 28 lb. per 100 feet 2 ½ % stretch at break Poor energy absorption At least 2 times as expensive as DE
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Elasticity Comparison
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Energy Absorption 1” x 100’ Double Esterlon Strength: 40,200# Weight/100’: 34.4# Maximum Energy Absorption: 8,000 Ft. Lb./Lb. Maximum Energy Absorption/100’: 275,200# 1” x 100’ Maxibraid Plus Strength: 60,000# Weight/100’: 28.2# Maximum Energy Absorption: 2,645 Ft. Lb./Lb. Maximum Energy Absorption/100’: 74,589#
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Work Load / Longevity
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Winch Line Inspection Lay the line out Inspect the eye-whipping Working area of the line Fuzzing Adjacent strand cuts- burns Stiffness-bulges Narrowing Glazing
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Tips for Pulling & Winch lines Appropriate line for vehicle and crew Minimum wraps 4 or 8 on drum Minimum 3/1 diameter sheaves No shock loading No Side loading Use a sling End for end at 6 months Clean the rope Stow the headache ball Know the rope-construction and time in service Never Assume
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The Bitter End Thank you
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