SLING TYPES zGenerally one of six types: yChain yWire rope yMetal mesh yNatural fiber rope ySynthetic fiber rope ySynthetic web
THREE MAIN GROUPS zBased on inspection procedures: yChain yWire Rope and Mesh yFiber Rope Web
ADVANTAGES & DISADVANTAGES zTo choose the best sling look at the following factors: ySize yWeight yShape yTemperature ySensitivity of the material to be moved yEnvironmental Conditions
CHAINS zStrength and Ability to Adapt to the load zAs with all slings, care should be taken to prevent damage. zSling failure has injured employees. zIdeal for lifting hot materials-up to 1000º zVisually inspect before each use- stretching, wear in excess of allowances, nicks and gouges.
WIRE ROPE zConsists of individual wires twisted to form strands. zStrands are then twisted to form a wire rope. zFiber Core-more flexible but less resistant to environmental conditions. zWire Core-stronger and more resistant to heat damage.
ROPE LAY zThe lay of the rope can mean one of three things: yOne complete wrap of a strand is a One Rope Lay.
STRAND DIRECTION zDirection the strands are wrapped around the core: zRight Lay Rope is one where the strands are wound in a right hand direction.
Direction of Wires in Strands to Direction of Strands to Core zRegular Lay Rope- wires in strands laid in one direction while strands in the rope are laid in the opposite direction.
LANG LAY ROPE zLang Lay Rope- wires are twisted in the same direction as the strands.
WIRE ROPE SLING SELECTION zFour Characteristics to Consider When Selecting a Wire Rope Sling: yStrength: function of size, grade & construction. yMust accommodate maximum load. yMaximum load determined by multiplier. yUltimate strength is divided by multiplier to determine working load limit.
THEREFORE: Ultimate Strength = 10,000 lbs. Multiplier*=5 Working Load Limit= 2,000 lbs. * New wire rope slings have a design factor of 5. After use ultimate strength is reduced. INSPECT!!
FATIGUE Result of the development of small cracks under repeated applications of bending loads. (When ropes make small radius bends) To prevent use blocking or padding to increase the radius of the bend.
ABRASIVE WEAR A rope withstands abrasion depending on its size, number of wires and construction. Smaller wires are more flexible but are less able to withstand abrasion. Larger wires are just the opposite.
ABUSE zAll factors being equal abuse will cause a rope to become unsafe long before any other factor. zTherefore, safe practices and use of wire ropes must be strictly adhered to.
WIRE ROPE SLING INSPECTION zVisually inspect before each use. zCheck twists or lay of rope. zIf 10 randomly distributed wires in one lay are broken or 5 wires in one strand are damaged, the sling must not be used. zEnd fittings and other components must also be inspected.
FIELD LUBRICATION zNO SET RULE. zDepends on conditions under which slings are used. zThe heavier the loads, the greater number of bends, or the more adverse the conditions-the more frequently the sling should be inspected.
STORAGE zWell ventilated, dry building or shed. zNever on the ground or left in weather. zNOTE: More frequently used slings give far more useful service than slings that are idle.
DISCARDING SLINGS zThe following factors require discarding of slings: ySevere Corrosion. yLocalized wear on the outside (shiny spots). y1/3 reduction of outer wire diameter. yDamage or displacement of end fittings. yDistortion, kinking, bird caging, etc. yExcessive broken wires.
FIBER ROPE AND SYNTHETIC WEB zFor temporary work-construction, painting, and marine operations. zBest choice for expensive loads, highly finished parts, fragile parts and delicate equipment.
FIBER ROPE zPreferred because they are pliant, grip the load and do not mar the surface of the load. zUse on light loads. zNot on objects with sharp edges and don’t expose to high temps or chemicals.
FIBER ROPE zChoice of rope type and size depend on application, weight to be lifted and sling angles. zInspect carefully before use as rope slings deteriorate quicker than wire rope. zTheir strength is harder to estimate.
INSPECTING FIBER ROPE zLook at its surface-look for dry, brittle, scorched or discolored fibers. zIf noted, Supervisor should be notified to determine if it should be discarded. zCheck interior-should be clean with no powder build up. zScratch the surface-if fibers come apart it has suffered damage and should not be used.
SYNTHETIC WEB SLINGS zMany advantages. zMade of nylon, dacron, polyester. zHave the following common properties: yStrength yConvenience ySafety yLoad Protection
COMMON PROPERTIES: zLong Life zEconomy zShock Absorbency zTemperature Resistance
UNIQUE PROPERTIES zNylon-use in neutral conditions or when alkaline or greasy conditions exist. Is resistant to chemicals and solvents. zDacron-use where high concentrations of acids exist. Alkaline deteriorates Dacron. zPolyester-use where acids or bleaching agents are present and when minimum stretching is important.
REMOVE IF DEFECTS EXIST zAcid or Caustic Burns. zMelting or Charring of any Part of the Surface. zSnags, Punctures, Tears or Cuts. zBroken or Worn Stitches. zWear or Elongation. zDistortion of Fittings.
PRIMARY SAFETY FACTORS 1. Size, Weight, and Center of Gravity. 2. Number and Angle of Legs. 3. Rated Capacity. 4. History, Care and Usage of the Sling.
SIZE, WEIGHT, CENTER OF GRAVITY zThe center of gravity is considered to be where the entire weight of the load may be. zThe crane hook must be directly above the center of gravity of the load. zVariations may cause tilting, stress on legs and potentially losing the load.
NUMBER OF LEGS AND ANGLES zAs the angle decreases, the rated capacity of the sling decreases. zThe smaller the angle, the greater the stress on the sling leg. zHeavier loads can be safely moved if the weight of the load is distributed among more sling legs.
RATED CAPACITY zRated capacity of sling depends on type and size of sling and type of hitch. new zManufacturers charts give ratings for new slings. Older slings must be used with more caution. zNever exceed sling’s rated capacity.
HISTORY OF CARE AND USAGE zMishandling and misuse are the leading cause of accidents. zProtect from sharp bends and sharp edges. zProperly Secure. zAccurately determine weight and balance. zDo not allow load to drag on ground.
Proper Care, continued: zPosition hook directly over the load. zSeat sling squarely in hook bowl. zTake up slack slowly-avoid jerking. zCheck tension-raise slowly and check for balance. zKeep all personnel clear. zAlways use tag lines.
ALWAYS OBEY THE NEVERS! zNever allow more than one person to control a lift or give signals. zNever raise the load more than necessary. zNever leave the load suspended in the air. zNever work under a suspended load.
MAINTENANCE OF SLINGS zCHAIN SLINGS: yClean prior to each inspection. yLook for Stretching, Binding, Wear, Nicks or Gouges. yFile heavy nicks and gouges, then check with caliper to ensure size is to recommendations. yCheck inside surface of links for wear.
Maintenance, continued: zWIRE ROPE: yClean prior to each inspection. yLubricated to manufacturers recommendations. yLubrication reduces corrosion and wear due to friction. yRope should be dry before lubricating.
Maintenance, continued: zFiber Ropes and Synthetic Webs- are generally discarded rather than repaired. zAlways follow manufacturers recommendations.