2. MSHA REGULATIONS
• 56/57.16007 Taglines, Hitches, and Slings
(a) Taglines shall be attached to loads that may
require steadying or guidance while
suspended.
(b) Hitches and slings used to hoist materials
shall be suitable for the particular material
handled.
• 56/57.16009 Suspended Loads
Persons shall stay clear of suspended loads.
4. HOISTS AND CRANES
• Different types of
hoisting equipment
– Manual and
powered devices
– underhung and top
running cranes
– monorails
– various types of jig
cranes
5. SLINGS
• Main purpose is to suspend a load from a
hoist
• Commonly made of wire rope or welded
link chain
• Can be constructed from fiber
rope,synthetic webbing or metal mesh
• Most slings are assembled by sling
manufacturers
• Can be assembled at the job site
6. The rigging system
• Load
• Sling
• Hoisting equipment
• Rigger (Designer and
Operator of the
system)
• = Single, complex
rigging system
7. The Rigger
• Must apply intelligence, common
sense and experience
• Anticipate what will happen when the
load is moved
• Thought process must take place
before the work is started
• Must answer the following
questions…..
8. Questions that must be
answered by rigger
• What is to be done with the
load?
• What tools are needed?
• Do the tools have the
capacity to handle the loads
and forces involved?
9. Questions that must be
answered by rigger
• How can the hookup be made?
• What will happen when the load
is first moved?
• What will be the travel path of
the load to reach the desired
location?
10. Questions that must be
answered by rigger
• How will the load be set down at the
desired location?
• What other factors are involved
(weather, electrical wires, sloping
grades, visibility)?
• Are additional personnel needed to
control the load safely during the
process?
11. Planning a rigging system
• Determine the weight of the load
• Locating the center of gravity of a load
• Distinguishing the force components
(horizontal and vertical) at work in a
diagonal force(loads at some angles other
than 90 degrees to the horizontal)
• Limitations of each component of the
rigging system
12. Determining the weight of
the load
• Shipping paper
• Manufacturers information attached
to the load
• Catalogs or blueprints
• Tables of weights from
manufacturers or handbooks
• Make sure the weight has not
changed
15. Calculating an allowable
load
• Determine the breaking strength of
the rope
– Load which will cause the rope to break
– Refer to standard tables in rigging
handbooks
– Listed according to the diameter and
kind of rope
– Design or safety factor usually 5
16. Calculating an allowable
load
• Find the load limit by dividing the
breaking strength of the rope by the
design factor
• Example-
– If the table indicates that the breaking
strength of the rope you are using is
27,000 pounds. Dividing this figure by
the design factor of 5 gives you a 5400
pound maximum allowable load.
17. Determine the center of
gravity
• The point at which the load will balance
• Whole weight of the load is considered
concentrated at this balance point
• When suspended from a point, the load
tends to move so that the center of gravity
is directly below the point of support.
• Make sure the center of gravity is located
directly below the hoisting hook
18. Determine the center of
gravity
• Stable load
–Balanced about its center of
gravity
–Directly below the hoisting hook
• Unstable load
– has a tendency to tip or topple
–Creates a hazard to personnel and
equipment
19. Before Lifting any load
check for hazards
• If not directly below
the hook the load is
unstable
• If the sling is free to
slide across the hook
the center of gravity
will shift directly
below the hook
• If two slings are used
one will assume the
greater share of the
load
20. Before Lifting any load
check for hazards
• The sling must not be
attached to the load at
a point lower than the
loads center of gravity
– Exception to this
rule when lifting
loads on pallets or
skids
– Then apex of sling
must be above the
center of gravity
21. Determining the center of
gravity
• Marked on the load by manufacturer
• Located in catalogs or blueprints
• Some objects have lifting lugs
• Calculate or estimate it
–Make an educated guess and
correct through trial and error
before making the lift
22. Procedures to determine
center of gravity
• Connect slings and hoist based on
estimate of object’s center of gravity
• Take up slack in slings or hoist
• Lift the load just enough to check stability
• If stable, continue to lift
• If unstable, lower load and adjust the
rigging
– Lift point should be moved closer to
end that dips
• Repeat until load is stable
23. Horizontal Force
• Very often sling legs are attached at
an angle less than 900
• Then a horizontal force is added to
the vertical force
• Resulting Combined force is greater
than the weight of the load
• Horizontal force increases as the
angle becomes smaller
24. Horizontal Force
• When a sling
angle is 300 the
total force is
twice that of the
load
• Sling Angles of
450 are not
recommended
25. Horizontal Force
• Horizontal forces act
on the load causing
damage by
compression or
buckling
• Horizontal forces are
absorbed by using a
spreader beam making
the sling legs between
beam and load vertical
26. Sling Components
• Hooks
• Coupling Links
• Fittings
• Sling Legs
• Can be assembled at the job site but must
use recommended components and
assembly procedures
– May also require some sort of weight test
27. Hook Hazards
• Attachments should never be field welded to a
hook
• Heat should not be applied in an attempt to
reshape a hook
– Can reduce strength of hook
– Could result in hook failure at loads lower than the
rated load
• If handles or attachments are required they
should be obtained from the hook
manufacturer
28. Purpose of a latch?
• Purpose is to retain slings in the hook
– Not intended to support the load
– Should be sturdy enough to retain the sling
if the moving load should catch on
something
• Latches are used to close the throat opening
• Must be provided on hoist and crane hooks
29. Reasons For Removing a
Hook From Service
• Hook throat has increased by
more than 15%
• Wear exceeds 10% of the
original hook section
dimension, or there is a bend
or twist of more than 10%
from the plane of the unbent
hook
• Hook shows cracks,
excessive nicks, or gouges
30. Factors Affecting Wire-Rope
Strength
• Three major signs of loss of strength
– Flat spots worn on outer wires
– Broken wires
– reduction of rope diameter
• Other factors that can reduce strength
– Bending the rope over a curved surface
– Temperature
– Corrosion and environment
– Rope fittings or terminations
31. Bending The Rope Over A
Curved Surface
• Normal curved surfaces that ropes are
curved over include sheaves, pins and
other curved surfaces
• The rope is subjected to bending stress
• Reduces rope efficiency/nominal strength
by a certain percentage
• Efficiency depends upon the:
– D = Diameter of curved surface
– d = Nominal diameter of rope
32. Example (You will need to refer
to Fig. 2-5 and Table 2-1)
• Fiber-core 6 x 37
wire rope, 1” in
diameter (d)
• Sheave with a 30”
diameter (D)
• D/d ratio is 30/1
• Efficiency is 95%
• Load Rating
dropped 95% from
83,600 lb. To 79,420
lb.
33. Wire Rope Clips
• Two basic designs
• U section contacts dead end of the rope
• Tends to crush some wires
• Affects strength if u-bolt clip is installed wrong
• Fist Grip can be installed either way
• Use only forged steel for lifting slings
34. Removal From Service
• Rope Distortion such as
kinking, crushing,
unstranding, birdcaging
or core protrusion
• Heat Damage from any
source
– Look for damage from
weld and weld splatter
• Cracked or deformed
end fittings(hooks
particularly)
• Corrosive failure of one
wire adjacent to end
fitting
35. Removal From Service
• One broken or cut strand
• Pitting due to corrosion
• For Single Wire Rope Either:
– 10 broken wires in a section the length of one
rope lay
– 5 broken wires in one strand within a distance
of one rope lay
36. Chain Hazards
• Similar force acts on
the links if the chain
is knotted or twisted
• Never shorten a
sling by twisting or
knotting
• Never use bolts and
nuts or other
fasteners to shorten
a sling
