Synthetic Slings, Ropes
and Winch Lines
2011 Pennsylvania REC
Key Man Conference
The Good Old Days
Chains and Wire Rope
-Inexpensive
-Durable
-They work
-Heavy,
-Conductive
-Wire rope kinks and cuts
-Easy to damage the equipment
Nylon-the First of the Common
Synthetics
• Petroleum-Coal Based
• 1935
• Toothbrush
WW II Uses of Nylon
• Replace Silk for
Parachutes
WWII Use of Nylon
• Nylon Stockings
Nylon
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Very Strong
Good Value
Degrades at 350o F.
Melts at 460o F.
Nearly 10% stretch at
working load
• Absorbs moisture
Polypropylene
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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
Polyester
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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
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
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 point800 degrees F.
• Absorbs moisture
• Expensive
• Abrasive
Liquid Crystal Polymer
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Vectrus -1985
As strong as UHMWP
Very little stretch
600 degree F. melting
point
• Little moisture
absorption
• Very expensive
Making Thread from Fiber
• Times have changed…
Webbing Manufacturing
3 Strand Rope
• Oldest style
Braided Rope
• No Twists-does not
“unwind” when loaded
• No Hockling
• Less Stretch
• More design options
Rope Braider
Webbing and Rope Lifting Slings
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Versatile
5-1 Safety factor
Lightweight
Nylon and Polyester are
inexpensive
• Available in high modulus
fibers
ANSI B30.9
Sling Tags
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 backspliced end
Methods of Hitching Loads
• Vertical
• Choker-Reduces
capacity 30%
• Basket-Doubles capacity
The Effect of the Angle
Inspecting Web Slings
• Appropriate Tags
• Fuzzing
• Splice Integrity
• Broken Stitches
• Burns
• UV Degradation
• Cuts-Mechanical Damage
• Chemical Damage
• Hard or glazed surface
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
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
Lifting and Pulling Lines
• A variety of
constructions are
available for different
applications including:
• 3 Strand
• 8 Strand
• 12 Strand
• Double Braid
• Parallel core
3 Strand
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Easy to manufacture
Inexpensive
Durable
Stretches
Unwinds when loaded
8 Strand
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Easy to splice
No twisting
Straighter Lay
Flattens under load
12 Strand-Hollow Braid
• No Twisting
• Easy to splice
• Great for pulling lines
Double Braid
• A rope in a rope
• Many manufacturing
options
• Less flattening in a
sheave
• Not the strongest
option because of the
angle
Parallel Core
• Most efficient use of
fiber-strongest
• Extremely durable
• Higher cost
• Harder to terminate
1 Inch Diameter Double Esterlon vs.
Maxi Braid Plus
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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
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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
Elasticity Comparison
Energy Absorption
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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#
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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#
Work Load / Longevity
Breaking
Strength
Working
Load
Application
Factor
# of Lifts
Before Failure*
30,000
5,000
6/1
1,000
30,000
6,000
5/1
750
30,000
7,500
4/1
500
30,000
10,000
3/1
300
30,000
15,000
2/1
100
30,000
20,000
1.5/1
25
30,000
28,000
1.1/1
5
* Relative Values Only
“The higher the application, the greater the service life”
Data from Cordage Institute Rope Manual
Winch Line Inspection
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Lay the line out
Inspect the eye-whipping
Working area of the line
Fuzzing
Adjacent strand cutsburns
• Stiffness-bulges
• Narrowing
• Glazing
Tips for Pulling & Winch lines
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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
The Bitter End
Thank you