Accident Prevention Manual
for Business & Industry:
Engineering & Technology
13th edition
National Safety Council
Compiled by
Dr. S.D. Allen Iske, Associate Professor
University of Central Missouri
CHAPTER 17
ROPES, CHAINS, AND SLINGS
Ropes, Chains, and Slings
• The ability to handle materials—to move them from one
location to another, whether during transit or at the
worksite—is vital to all segments of industry.
• Materials must be moved, for example, in order for
industry to manufacture, sell, and utilize products. In
short, without materials-handling capability, industry would
cease to exist.
• Ropes, chains, and slings require special safety
precautions for use and storage.
• Know the properties of the various types of ropes, chains,
and slings used.
Types of Fiber Rope
• Manila fiber—best suited natural fiber for cordage
• Sisal fiber—20% less breaking strength than Manila
• Acids and caustics deteriorate both manila and sisal fibers
• Other natural fiber—cotton, flax, straw, asbestos, silk,
rawhide, and many others
• Synthetic fiber—nylon, polyester, and polyolefin
• used more often than natural fibers
• more known about their properties
• splices can be made readily and develop nearly full strength of rope
Types of Fiber Rope
• Nylon rope
• has 2.5x the breaking strength of manila and four times its
working elasticity
• highly resistant to organisms that cause mold and mildew
• breaking strength is reduced by 10–15% when wet or frozen
• vulnerable to drying oils, mineral acids, phenols, and heat
• absorbs and stores energy in the same manner as a spring
Types of Fiber Rope (Cont.)
• Polyester
• best general-purpose rope
• does not absorb moisture and retains full strength when wet
• it has half of the absorption capability of nylon
• shows little deterioration from sunlight and resists abrasive wear
well
• safe operating temperature range is –20° to 180°F
Types of Fiber Rope (Cont.)
• Polyolefin
• similar to nylon and polyester
• highly resistant to a variety of acids
• it swells and softens when exposed to hydrocarbons, especially at
temperatures above 150°F
• easily deteriorates under abrasion
Types of Fiber Rope (Cont.)
• Composite rope
• made by combining several types of synthetic or combining
synthetic and natural fibers
• can be made to match specific job requirements
• Other types of rope
• paper, glass, acrylic, rayon, pvc, rubber, cellulose acetate,
fluorocarbon, and polyurethane
Fiber Rope Working Load
• Working loads are for rope in good condition, with
appropriate splices in noncritical applications, under
normal service conditions, and under very modest
dynamic loads.
• Exercise caution when using load ratings as the safety
factor is not the same for all ropes.
• Rope use, condition, and exposure can affect the degree
of risk to life and property.
• See Tables 17–A and 17–B for specifications.
Working Load Selection
• Select a higher working load only with expert knowledge
of conditions and a professional estimate of the risks
involved.
• Working load figures generally do not apply when rope is
subject to dynamic loading.
• Working load figures may apply for light dynamic loading,
meaning the load is be handled slowly and smoothly to
minimize dynamic effects.
• In towing lines, lifelines, safety lines, and climbing line
applications, working loads in Tables 17–A and 17–B do
not apply.
Fiber Rope Inspections
• Inspect the entire length of new ropes before use to
determine that no damage or defects exist.
• Any irregularity in appearance is evidence of the
possibility of degradation or weakness.
• Under ordinary conditions rope must be inspected every
30 days.
• OSHA requires rope that is used to connect a load to a
material handling device to be inspected each day before
use.
Fiber Rope Inspections (Cont.)
• External
• Examine the entire length of the rope inch by inch, for wear,
abrasions, powdered fiber between strands, broken or cut fibers,
displacement of yarns or strands, variation in size or roundness of
strands, discoloration, and rotting.
• The “fingernail test” is a quick test for chemical damage.
• Internal
• Untwist the rope in several places to see whether the inner yarns
are bright, clear, and unspotted.
• In rope with a central core, the core should not break away in small
pieces when examined.
Care of Fiber Rope in Use
• Recognize the effects of chafing, cutting, elasticity,
diameter-strength ratio, and general mishandling.
• Do not drag rope.
• Handle twisted rope so it retains the amount of twist (balance) that
the rope seeks when free and relaxed.
• Kinking strains the rope and may overstress the fibers.
• Avoid sharp bends over unyielding surfaces.
• Splice lengths of rope that must be joined, do not knot them.
• A proper splice will retain 100% strength, while a knot retains only 50%.
Care of Fiber Rope in Use (Cont.)
• Thoroughly dry rope that has become wet, otherwise it will
quickly deteriorate.
• Do not allow wet rope to freeze; if rope does freeze,
completely thaw before use. Frozen fibers will break as
they resist bending.
• Do not use wet rope or rope reinforced with metallic
strands near power lines or other electrical equipment.
Care of Fiber Rope in Storage
• Store away from fumes, heat, chemicals, moisture,
sunlight, and rodents.
• Store in a dry place with circulating air, but air should not
be extremely dry.
• Hang up small ropes and lay larger ropes on gratings so
air can get underneath and around them.
• Do not store rope unless it has been cleaned.
Wire Rope
• more widely used than fiber rope
• greater strength and durability under severe working
conditions
• physical characteristics do not change when used in
varying environments
• controlled and predictable stretch characteristics
Wire Rope Classification
• The most widely used construction of rope are six-strand
ropes of these two classifications:
• 6  19
• 6  37
• There are other variations in rope sizes with different
cores.
• The more wires per strand, flexibility increases.
• The fewer wires per strand, crush and abrasion resistance
increases.
Wire Rope Service Requirements
• Different jobs will require different types of ropes.
• Consideration of the properties of different rope types,
core components, and strand count must be evaluated
prior to selecting wire rope.
• Consult engineers from reliable rope manufacturers for
assistance in rope selection.
Design Factors for Rope
Used in Hoisting
• Calculate by dividing the nominal catalog strength of the
rope by the sum of the maximum loads to be hoisted.
• Federal, state, or locals codes may describe exactly how
design and operating factors should be figured.
• Check what codes are in force before final selection.
Wire Rope Inspection
and Replacement
• OSHA minimum for wire rope or cable includes installation
and yearly inspections. However, more frequent
inspection is highly recommended.
• Rope should be inspected for crown wires, kinking, high
strands, loose wires, nicking, and lubrication.
• Measure rope diameter and length for sudden changes
that may indicate the rope is nearing the end of its useful
life.
Wire Rope Wear and Damage
Wire Rope Inspection
and Replacement
• Replacement is based on the number of broken wires per
strand in one rope lay or on the number of broken wires
per rope lay in all strands.
• OSHA specifications for unacceptable rope
• running ropes
• 3 broken wires in 1 rope lay and 6 random broken wires in 1 rope lay
• wire rope slings
• 5 broken wires in 1 strand in one rope lay and 10 random broken wires
in 1 rope lay
Care of Wire Rope in Use
• Factors affecting rope condition
• vary widely; corrosion and moisture cause wear that is
dangerous and difficult to detect
• also kinks, fatigue, drying of lubrication, overloading, over
winding, and mechanical abuse
• Recommendations for care
• Apply alkali and acid-free lubricants to clean and dry rope.
• Clean rope monthly with light lubricants and avoid cleaning
fluids, which can damage the core.
Sheaves and Drums
• Wire rope bending stresses depend on the diameter of
drums and sheaves.
• Condition and contour of sheaves grooves is important for
the service life of wire rope.
• Check sheave tolerances to ensure they are the correct size for the
rope to be used.
• Avoid multi-layer winding of rope on drums when possible.
• If unavoidable limit the number of layers to three.
Wire Rope Installation
During the entire installation process make sure that:
1.
2.
3.
4.
The appropriate rope is attached to the drum.
Appropriate tension on the rope is maintained as it is wound.
Each turn is guided as close to the preceding turn as possible so
that there are no gaps between turns.
There are at least two dead turns on the drum when the rope is
fully unwound during normal operating cycles.
Wire Rope Installation (Cont.)
Wire Rope Fittings
• Wire rope can be attached to fittings in a variety of ways
depending on the needs of the job.
• Pressed fittings, mechanical sleeve splices, hand-tucked
splices, clips and clamps, sockets, or knots are
acceptable means of rope fittings.
• Maximum strength of an attachment is attained only when
the connection is made according to the manufacturer’s
instructions.
Rigging
• The most important job of any lifting operation is rigging
the load.
• It is estimated that 15–35% of crane accidents may
involve improper rigging.
• Loads vary in weight, physical dimension, and shape,
therefore a rigger needs to know what method of
attachment can be used properly.
• The single most important rigging precaution is to
determine the weight of the load before lifting it.
Fiber and Wire Rope Slings
• Safety considerations for rope sling assembly:
• proper rope selection
• fittings suitable for the load
• selecting the proper fastening method
• proper selection of sling type
• proper hitch selection
• regular inspection and maintenance
Fiber and Wire Rope Slings (Cont.)
• OSHA stipulates that fiber rope slings must be made with
new fiber rope.
• Fiber rope is suitable for handling loads that would otherwise be
damaged by contact from metal slings.
• Wire rope slings provide the greatest strength for slings.
• Cable-laid slings, made from multiple wire ropes laid into
one rope structure, provide more flexibility than strand-laid
slings.
• Braided slings are used where flexibility, high strength,
and resistance to corrosion are essential.
Fiber and Wire Rope Slings (Cont.)
• Methods of attachment
• All hooks and rings used as sling connections should develop the
full capacity of the wire rope sling.
• Working load
• Reference rated load capacities given from manufacturer.
• Abrasion, nicking, distortion, corrosion, and bending will affect the
load rating.
Fiber and Wire Rope Slings (Cont.)
• Working load
• Use pads or saddles to protect ropes or chains.
• Thimbles spliced in the ends of slings will reduce wear.
• Consider the angle formed, as this greatly affects the working load
of a sling.
Angle Strength Loss
from Rated Capacity
• Slings can be used at various angles.
• Rope stress increases rapidly with the angle of lift.
• Make adjustments in maximum load ratings based on the angle of
the hoisting rope.
• The rated load capacity of the sling decreases sharply as the angle
formed by the sling’s leg and the horizontal becomes smaller.
• When this angle is 45 degrees, the rated load capacity has decreased to
71% of the load that can be lifted when the legs are vertical.
• The actual stress is equal to the amount of the load that a leg must
support, divided by the cosine of the angle that the leg is from the vertical.
• To avoid excessive angles, use longer slings, if head room permits.
Angle Strength Loss
from Rated Capacity
Fiber and Wire Rope Sling Inspection
• Ensure a trained and competent person inspects the
slings at least every 12 months.
• Employees should promptly report any questionable
conditions.
• Immediately withdraw from service slings that fail
inspection requirements.
• Ensure removed slings are unusable by further destroying them
before they are discarded.
Safe Operating Practices for Slings
(ANSI/ASME) B30.9 recommendations for sling use:
• load control
• load positioning
• inspections
• communication
Chains and Chain Slings
• Alloy steel is the standard material for chain slings.
• Special purpose alloys are available.
• ASTM-approved alloy steel chains have minimum tensile
strength of 115,000 psi and a minimum elongation of 15%.
• Alloy steel chains are suitable for high-temperature
operations.
• Always use a chain rated for a higher working load if
severe impact loading may be encountered.
Chain Sling Hooks and Attachments
• Should be made of identical or equivalent material to that
of the chain.
• In emergency conditions that require replacement, select an
attachment with extreme care.
• OSHA prohibits the use of makeshift links, fasteners, or
other attachments.
• Handles attached to assembly hooks to prevent hand and
finger injuries and can increase operating efficiency.
Chain Sling Inspection
Three types of inspections required:
1. initial inspection for new and repaired slings
2. frequent inspections by the person handling it each
time it is used
3. periodic inspections on a semiannual or more frequent
inspection by a competent person
•
based on frequency of use, severity of service conditions, and
service life
Chain Sling Inspection (Cont.)
• Maintain documentation of inspections.
• The competent person should have authority to remove
damaged assemblies from service.
• Link-by-link inspection is the best way to detect wear and
stretching.
• Overall measurements of sling length, and even measurements of
1 to 3 ft are inadequate.
• Measure between the shank and narrowest point of the
hook.
Safe Practices for Chain Slings
• Purchase complete chain slings from the manufacturer
•
•
•
•
and do not remove identification tags.
Never splice a chain or put strain on a kinked chain.
Remember decreasing the angle between the legs of a
chain sling and the horizontal increases the load of the
legs.
See that the load is always properly set in the bowl on the
hook.
Store chains not in use in a suitable rack.
Synthetic Web Slings
• Nylon and polyester are the fibers most commonly used.
• Each has advantages and disadvantages.
• Synthetic web slings can be cut easily and are not abrasion
resistant.
• ASTM B783 states the minimum breaking strength shall
be 5x the rated capacity.
• Sling capacity is reduced when used in a basket hitch
when used with one crane hook.
Synthetic Web Sling Inspection
1. Initial
2. Frequent
3. Periodic
• OSHA requires synthetic web slings to be inspected each
day before and during use
Synthetic Web Sling Inspection (Cont.)
• Types of damage to look for:
• excessive abrasive wear on webbing and any fittings
• cuts, tears, snags, punctures, holes, crushed fabric
• worn or broken stiches
• burns, charring, melting, or weld spatter damage
• knots
• chemical damage
• broken, distorted, or excessively worn fittings
Metal Mesh Slings
• Classifications: heavy duty, medium duty, or light duty
• All metal slings are proof tested to a minimum 200% of
their rated load capacity, which removes permanent
stretching when used at rated load capacity.
• Safely handle sharp-edged materials, concrete, and high
temperature materials up to 500°F.
• The design factor of metal mesh slings is 5 to 1.
Metal Mesh Slings Structure
Safe Practices for Metal Mesh Slings
• Safe use depends on the use of the right sling for the right
load and the construction of the sling.
• Any danger in their use stems mainly from improper use.
• Follow manufacturer’s recommendations for certain
hitches.
Metal Mesh Sling Inspection
• OSHA requires annual inspections by a qualified person.
• Initial, periodic, and frequent inspections are
recommended.
• Maintain written inspection records.
• Look for signs of wear, lack of flexibility, visible distortion,
and other indicators of damage.