BASIC RIGGING

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BASIC RIGGING
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MSHA REGULATIONS

• S 77.210 Hoisting of materials.
• (a) Hitches and slings used to hoist materials
  shall be suitable for handling the type of
  materials being hoisted.
• (b) Men shall stay clear of hoisted loads.
• (c) Taglines shall be attached to hoisted
  materials that require steadying or guidance.

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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.

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TOOLS OF RIGGING

• Hoists
• Cranes
• Slings
• Special lifting devices

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HOISTS AND CRANES

• Different types of hoisting equipment
• Manual and powered devices
• underhung and top running cranes
• monorails
• various types of jig cranes

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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

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The rigging system

• Load
• Sling
• Hoisting equipment
• Rigger (Designer and Operator of the system)
• Single, complex rigging system

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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..

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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?

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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?

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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?

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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

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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

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Volume Area Formulas
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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

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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.

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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

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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

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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

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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

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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

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Procedures to determine center of gravity

• Connect slings and hoist based on estimate of
  objects 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

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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

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Horizontal Force

• When a sling angle is 300 the total force is
  twice that of the load
• Sling Angles of 450 are not recommended

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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

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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