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Introduction
Terry Elmy– retired, 31 years, Pt. Comfort,
Massena, Pt. Henry, and Tennessee
– started Pro Crane ServicesPro Crane Services in 1996
– services include operator & maintenance training, systems audits, crane procurement, accident investigation, and expert witness services
– recently added structural and BTH device analysis capability
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SAFE
LIFTING
THE SAFETY TRIANGLE
EFFECTIVE, EQUIPMENT
MAINTENANCE
TRAINED, QUALIFIED
OPERATORS
PROPER EQUIPMENT
DESIGN
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Training Objectives:
• Review fundamentals of rigging– the load– the hitch– attachments– sling angle– D/d ratio
• General use guidelines• Provide answers to
technical questions
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Rigging
The handling, setting and erection of materials and equipment is a hazardous occupation. Each operation presents its own peculiar problems and no two jobs are alike. With proper consideration taken, each job can be performed free of bodily harm to the employee and without damage to the equipment.
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Rigging
Rarely does the typical worker get the opportunity to actually select the rigging. It is normally provided at the work site by others. This in itself can create serious problems. Workers need to be trained in the proper use of rigging and not to use rigging improperly because “it’s all I had to work with.”
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Rigging - Plan
• Who is responsible for the rigging?
• Is the equipment in safe condition?
• Are the working load limits adequate?
• Will the load be under control?
• Are there any unusual loading or environmental conditions?
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Rigging Basics – The Load
• Load weight shall be within rated capacity of the sling* ASME B30.9
*such that no part of the rigging is overloaded
A COMPLETE UNDERSTANDING OF THE LOAD FORCES IS REQUIRED!
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Rigging Basics – The Load
• Load weight may be obtained from:– equipment nameplate– packing list– drawings– shipping tag– weighing the load– an estimate or calculation of
load weight
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Rigging Basics – The Load
Load information:
• Size
• Weight
• Center of gravity
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Rigging Basics – The Load
Load information:• Size• Weight• Center of gravity
– The center of gravity is the point at which a load will balance - and that point must be directly below the hook or principal lifting point.
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Rigging Basics – The Load
Load information:• Size• Weight• Center of gravity
– The center of gravity is the point at which a load will balance - and that point must be directly below the hook or principal lifting point.
– An object will tilt until its center of gravity IS directly below the hook.
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Rigging Basics – The Load
Load information:• Size• Weight• Center of gravity
– The center of gravity is the point at which a load will balance - and that point must be directly below the hook or principal lifting point.
– An object will tilt until its center of gravity IS directly below the hook.
– If an object is evenly shaped measure to find the center of gravity
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Rigging Basics – The Load
Load information:• Size• Weight• Center of gravity
– The center of gravity is the point at which a load will balance - and that point must be directly below the hook or principal lifting point.
– An object will tilt until its center of gravity IS directly below the hook.
– If an object is evenly shaped measure to find the center of gravity
– Determination of center of gravity of unevenly shaped objects can be very complicated – mistakes or bad assumptions can result in disastrous consequences
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Rigging Basics – The Load
Load information:• Size• Weight• Center of gravity
– The center of gravity is the point at which a load will balance - and that point must be directly below the hook or principal lifting point.
– An object will tilt until its center of gravity IS directly below the hook.
– If an object is evenly shaped measure to find the center of gravity
– Determination of center of gravity of unevenly shaped objects can be very complicated – mistakes or bad assumptions can result in disastrous consequences
– Always make the load connection point is above the center of gravity
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Center of GravityFinding the center of gravity based on weights
3000 #6000 #
2000 #
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Center of GravityFinding the center of gravity based on weights
6000 #
2000 #
6000/(6000+2000)= 3/4 = 75%
75%
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Center of GravityFinding the center of gravity based on weights
8000 #
8000/(8000+3000)= .73 = 73%
3000 #73%
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Center of Gravity
• Other methods of establishing COG– require supplier to mark COG– find by trial lifts– find by trial and error
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Center of Gravity
• Other methods of establishing COG– require supplier to mark COG– find by trial lifts– find by trial and error
Caution: weight must be known and rigging may need to be oversized before using any
trial method
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Rigging Basics - Hitches
Vertical – having the load suspended vertically on a single part or leg of the sling.
Characteristics:• Load capacity is 100 % that of a single part• Taglines should be used if the load tends to rotate
as rotation can damage the sling.• Use on items with lifting eye bolts or shackles or
when a second sling is used in a spreader bar application
• Do NOT use when lifting loose or lengthy material, anything difficult to balance
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Rigging Basics - Hitches
Basket - loading with the sling passed under the load and both ends on the hook, master link, or lifting device
Characteristics:• Effectively doubles the capacity of a single vertical sling
• Stress on each leg tends to be equalized• Use on straight lifts when the load is shaped so that the sling (or slings) will not slide over the surface.
• Do NOT use on loads that are difficult to balance and could tilt or slip out of the sling(s).
• When terminating to a common point (like a hook), sling angle can reduce sling capacity.
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Rigging Basics - Hitches
Choker – loading with the sling passed through one eye or choker hook and suspended by the other end
Characteristics:• Choker hitch is easy to attach & forms a noose that tightens as the load is lifted• Rated capacity is 75% of the single part*.• Use to turn a load (if possible use a double choker hitch) or when handling bundles of bars or pipes• Do NOT use on loads difficult to balance or which
may slip out the choke
* based on wire rope and chain slings, 120 degree angle of choke
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Rigging Basics - Hitches
Choke angle – the angle formed between the load line and the noose
Angel of Choke Rated Capacity Factor*120 - 180° = 100% 90 - 119° = 87% 60 - 89° = 74% 30 - 59° = 62% 0 - 29° = 49%
*based on wire rope slings
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Rigging Basics - Hitches
• Do not confuse choke angle with angle of inclination of the load
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Rigging Basics - Hitches
• Choker hitches are not suited to long loose bundles
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Rigging Basics - Hitches
• Double Wrap Basket Hitch– adjustment of slings is required while taking
up slack to avoid overloading one side of the sling (this applies to all basket hitches)
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Rigging Basics - Hitches
• Turning loads with a choker hitch
Loads in legs will equalizeduring lifting
Loads in legs will tend not to equalize during lifting
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Rigging Basics – Sling Angle
Sling angle has a dramatic effect on the actual load on the sling. Take a sling that has a 1000 pound vertical lifting capacity in a basket hitch:
Sling with 500# vertical hitch capacity
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Rigging Basics – Sling Angle
As angle decreases - tension on each leg increases - increasing the strain on each leg
Sling with 500# vertical hitch capacity
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Rigging Basics – Sling Angle
A different look, with the same load and sling, changing the angle has a similar dramatic effect
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Rigging Basics – Sling Angle
A different look, with the same load and sling, changing the angle has a similar dramatic effect
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Rigging Basics – Sling Angle
• The sling angle factor equals H divided by L, the inverse, L/H, can also be used to calculate sling load
L/H is useful to calculate sling load when the vertical force is known. L/H for common angles is approximately: 60º - 1.2; 45º - 1.4; 30º - 2
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Rigging Basics
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Sling Angle Example Problem Select slings to pick up the load shown below.
CG2’8’
10,000#
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Sling Angle Example Problem Select slings to pick up the load shown below.
CG2’8’
10,000#
First, we need to know the vertical load at eachconnection point, A and B to support the load.
A B
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Sling Angle Example Problem Select slings to pick up the load shown below.
CG2’8’
10,000#
The vertical load is offset, proportioning givesthe following information:
ForceA x 10’ = 10,000# x 2’
ForceA = 2,000#
therefore, ForceB = 8,000#
A B
FAFB
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
We know we want to position the hookdirectly over the center of gravity
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Next we know the sling furthest away from the hookwill have the smallest angle, so we’ll size it first andbase our sling angle at the optimal angle of 60º.
60º
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Since the angle is 60º, the height of the hook is nowfixed as is the sling length. Because the angle is 60º,the sling length is twice the base length (2 x 8’ = 16’).
60º
16’
Cosine 60º = 0.5
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Knowing the L/H = 1.2 for 60º sling angle, the height of the hook is
L/H = 1.2H = 16/1.2H = 13.3 feet
60º
16’
13.3’
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Additionally, knowing that L/H = 1.2 for 60º sling angle, the load
on sling A = 1.2 x ForceA or 1.2 x 2,000# = 2,400#.
60º
16’
2,400#
13.3’
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Sling B’s length can now be calculated to an exact number.
Length of Sling B = √(13.3)2 + (2)2 = 13.44 feet
60º
16’
2,400#
13.3’
13.44’
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Sling B’s load can now be calculated:
L/H = 13.44/13.3 = 1.01LoadB = 1.01 x 8,000# = 8,084#
60º
16’
2,400#
13.3’
13.44’
8,084#
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Sling Angle Example Select slings to pick up the load shown below.
CG2’8’
10,000#
Using wire rope slings, EIPS grade, 6x19 class ropewith a mechanical splice, Sling A needs to be 3/8-in. diameter min.Sling B needs to be ¾-in. diameter min.
60º
16’
2,400#
13.3’
13.44’
8,084#
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Rigging Basics – D/d Ratio
• D/d ratio is the ratio of the diameter around which the sling is bent divided by the body diameter of the sling. Whenever a sling body is bent around a diameter, the strength of the sling is decreased.
Application: 6x19 and 6x37 Class rope, may not apply to cable laid or braided slings
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Rigging Attachments
• Sockets– swaged and poured
socket assemblies shall be proof tested
– mechanical splice single vertical leg slings test shall be 2 times vertical load limit
ASME B30.9
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Rigging Attachments
• Shackles– used only those rated
for overhead lifting
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Rigging Attachments
• Shackles– synthetic web slings
connected to shackles of sufficient size to not cause bunching or pinching of the sling
Use wide shackles to prevent pinching or bunching
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Rigging Attachments
• Hooks – inspect before use, use ASME B30.10 or a recognized Engineering Standard
Spreadhook
Where is the hook latch??
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Rigging Attachments
• Hooks – avoid eccentric loading of hooks
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Rigging Attachments
• Hooks– do not exceed 90
degrees included angle when connecting two slings in a hook. If you have an included angle more than 90 degrees, or more than two legs, use a shackle or a master link to connect.
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Rigging Attachments
• Turnbuckles– Turnbuckles can be used to adjust sling
length. Be sure to use only load rated components
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Rigging Attachments
• Eye bolts– use only forged eye bolts rated for lifting– never use if damaged, bent, elongated– never use regular eye bolts for angular lifts– always seat shoulder against the load
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Rigging Attachments
• Eye bolts– always shim eye bolts to seat shoulder in-line for
angular loading– for angular lifts reduce working load
• 45 degrees – 30% of rated working load• 90 degrees – 25% of rated working load
Angle of pull
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Rigging Attachments
• Eye bolt - rigging
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Rigging Attachments
• Eye bolt - rigging
How to prevent load buckling?
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Rigging Attachments• Spreader beam - A below-
the-hook lifting device that utilizes two or more hooks (attaching devices) located along a beam and the spreader beam attaches to the hoist by means of a bail. The spreader beam is used to handle long or wide load and serves to "spread" the load over more than one lifting point. Often used in conjunction with slings.
Note: a common misconception of spreader beams is that they equalize the loadingalong the beam. They do not! Spreaders only eliminate horizontal forces from affectingthe load being hoisted.
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Rigging Attachments
• Spreader beam
Spreader Beam
Center of gravity
¼ L
1/2 L
Fa
FbWith the CG off center of the hook as shown, the verticalforce at Fa will be 75% of theload weight and the vertical forceat Fb will be 25% of the totalload weight. No horizontal forces will be exerted on the load.
Total Weight = W
1/2 L
Load
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Rigging Attachments
• Spreader beam
Spreader Beam
Center of gravity
¼ L
1/2 L
Fa
FbWith the CG off center of the hook as shown, the verticalforce at Fa will be 75% of theload weight and the vertical forceat Fb will be 25% of the totalload weight. No horizontal forces will be exerted on the load.
Total Weight = W
1/2 L
Load
As shown, will the load be level duringhoisting?
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Rigging Attachments
• Spreader beam
The load will tilt untilthe center of gravityaligns with the hook.
Spreader Beam
Load
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Rigging Attachments
• Spreader beam
Center of gravity¼ L
¼ L
Fa
Fb
Without the use of a spreaderbeam, the vertical forces remainthe same, however, the sling loadis a function of the sling angle andthe sling load will be higher thanthe sling between the spreaderand the load.There will, in this case, behorizontal forces exerted uponthe load, dependent upon thesling angle.
Total Weight = W
Fh
Fh
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General Use Guidelines
• Pre-use and periodic inspection is required on all sling and rigging components
OSHA 1926.251, 1910.184
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Periodic inspection frequency/records
Periodic inspection performed by ?
Frequent inspection frequency/records
Label*
Chain slings OSHA 1910.184(e)(3) – at least annually with records
ASME: normal – annually; severe service – monthly to quarterly with records
OSHA – competent person
ASME - competent person
OSHA – before use(1910.184(d) w/o recordsASME: normal –monthly;
severe service – daily to weekly w/o records
OSHA – size, grade, rated cap., & reach
ASME: mfgr., grade, size, no. of legs, reach, rated load for hitches
Wire rope slings
OSHA – noneASME – based on service, at
least annually with records
OSHA – no periodicASME – competent
person
OSHA – before use(1910.184(d)ASME – daily w/o records
OSHA – noneASME – mfgr., size, rated
load for type of hitch & angle
Synthetic web slings
OSHA – noneASME – recommended at
least annually based on service, records recommended
OSHA – no periodicASME - competent
person
OSHA – before use(1910.184(d)ASME - daily w/o records
OSHA – rating @ each type of hitch, type of material
ASME – mfgr., mfgr. Stock no., rated load for each type of hitch, material type & construction
Metal mesh slings
OSHA – noneASME - based on service, at
least annually; records recommended
OSHA – no periodicASME - competent
person
OSHA – before use(1910.184(d)ASME – daily w/o records
OSHA – rated @ vertical and choker hitch loading
ASME – mfgr., rated load for hitch & angle, width and gauge
* Sling I.D., per ASME B30.9, shall be maintained to be legible for the life of the sling
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General Use Guidelines
• Rigging equipment shall not be loaded beyond its recommended working load limit (WLL)
OSHA 1926.251
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General Use Guidelines
• When not in use, rigging shall be removed from work area and properly stored
OSHA 1926.251
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General Use Guidelines
• During lifting, personnel shall be alert for possible snagging
ASME B30.9
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General Use Guidelines
• Slings should be long enough so that rated load is adequate
ASME B30.9
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General Use Guidelines
• Multiple leg slings shall be selected so as not to introduce into the leg, a load greater than permitted
ASME B30.9
Note: select multiple leg slings based on twolegs supporting the entire weight of the load andthe other leg(s) balancing the load.
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General Use Guidelines
• Shock loading should be avoided
ASME B30.9
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General Use Guidelines
• The load shall be applied to the center of the hook (unless the hook is designed for point loading)
ASME B30.9
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General Use Guidelines
• When used in a choker hitch, prevent the load on any portion of the sling from exceeding the rated load
ASME B30.9
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General Use Guidelines
• Slings shall not be shortened by knotting or twisting
ASME B30.9
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General Use Guidelines
• Slings should not be pulled from under a load when the load is resting on the sling
ASME B30.9
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General Use Guidelines
• Slings should not be dragged on the floor
ASME B30.9
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General Use Guidelines
• Sharp corners in contact with the sling should be padded
ASME B30.9
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General Use Guidelines
The following slide is not for the faint of heart. If you are are botheredby accident scenes, do not look at the screen until the “All Clear” signal is given.
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General Use Guidelines
• Do not place body, fingers, etc. between the sling and load or hook
ASME B30.9
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General Use Guidelines
• Personnel shall not ride the sling (or load)
ASME B30.9
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General Use Guidelines
• Personnel should stand clear of suspended load
ASME B30.9
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General Use Guidelines
• And not “Be” the suspended load!!
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No Homemade Slings
WARNINGWARNINGNo wire rope sling shall be fabricated using wire rope clips!!
Preferred sling construction is to usea Flemish eye splice with a mechanicalsleeve (turn back construction is notrecommendable)
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Questions?
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