MATERIALS HANDLING IN CONSTRUCTION

MATERIALS HANDLING IN CONSTRUCTION

SLING TYPES Generally one of six types: Chain Wire rope Metal mesh Natural fiber rope Synthetic fiber rope Synthetic web

THREE MAIN GROUPS Based on inspection procedures: Chain Wire Rope and Mesh Fiber Rope Web

ADVANTAGES & DISADVANTAGES To choose the best sling look at the following factors: Size Weight Shape Temperature Sensitivity of the material to be moved Environmental Conditions

CHAINS Strength and Ability to Adapt to the load As with all slings, care should be taken to prevent damage. Sling failure has injured employees. Ideal for lifting hot materials-up to 1000º Visually inspect before each usestretching, wear in excess of allowances, nicks and gouges.

WIRE ROPE Consists of individual wires twisted to form strands. Strands are then twisted to form a wire rope. Fiber Core-more flexible but less resistant to environmental conditions. Wire Core-stronger and more resistant to heat damage.

ROPE LAY The lay of the rope can mean one of three things: One complete wrap of a strand is a One Rope Lay.

STRAND DIRECTION Direction the strands are wrapped around the core: Right 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 Regular Lay Rope- wires in strands laid in one direction while strands in the rope are laid in the opposite direction.

LANG LAY ROPE Lang Lay Ropewires are twisted in the same direction as the strands.

WIRE ROPE SLING SELECTION Four Characteristics to Consider When Selecting a Wire Rope Sling: Strength: function of size, grade & construction. Must accommodate maximum load. Maximum load determined by multiplier. Ultimate 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 All factors being equal abuse will cause a rope to become unsafe long before any other factor. Therefore, safe practices and use of wire ropes must be strictly adhered to.

WIRE ROPE LIFE Many operating conditions affect wire rope life: Bending. Stresses. Corrosion. Loading Conditions. Jerking (Speed). Abrasion. Sling Design. Materials Handled. Environment. History of Previous Use.

WIRE ROPE SLING INSPECTION Visually inspect before each use. Check twists or lay of rope. If 10 randomly distributed wires in one lay are broken or 5 wires in one strand are damaged, the sling must not be used. End fittings and other components must also be inspected.

FIELD LUBRICATION NO SET RULE. Depends on conditions under which slings are used. The heavier the loads, the greater number of bends, or the more adverse the conditions-the more frequently the sling should be inspected.

STORAGE Well ventilated, dry building or shed. Never on the ground or left in weather. NOTE: More frequently used slings give far more useful service than slings that are idle.

DISCARDING SLINGS The following factors require discarding of slings: Severe Corrosion. Localized wear on the outside (shiny spots). 1/3 reduction of outer wire diameter. Damage or displacement of end fittings. Distortion, kinking, bird caging, etc. Excessive broken wires.

FIBER ROPE AND SYNTHETIC WEB For temporary work-construction, painting, and marine operations. Best choice for expensive loads, highly finished parts, fragile parts and delicate equipment.

FIBER ROPE Preferred because they are pliant, grip the load and do not mar the surface of the load. Use on light loads. Not on objects with sharp edges and don’t expose to high temps or chemicals.

FIBER ROPE Choice of rope type and size depend on application, weight to be lifted and sling angles. Inspect carefully before use as rope slings deteriorate quicker than wire rope. Their strength is harder to estimate.

INSPECTING FIBER ROPE Look at its surface-look for dry, brittle, scorched or discolored fibers. If noted, Supervisor should be notified to determine if it should be discarded. Check interior-should be clean with no powder build up. Scratch the surface-if fibers come apart it has suffered damage and should not be used.

SYNTHETIC WEB SLINGS Many advantages. Made of nylon, dacron, polyester. Have the following common properties: Strength Convenience Safety Load Protection

COMMON PROPERTIES: Long Life Economy Shock Absorbency Temperature Resistance

UNIQUE PROPERTIES Nylon-use in neutral conditions or when alkaline or greasy conditions exist. Is resistant to chemicals and solvents. Dacron-use where high concentrations of acids exist. Alkaline deteriorates Dacron. Polyester-use where acids or bleaching agents are present and when minimum stretching is important.

REMOVE IF DEFECTS EXIST Acid or Caustic Burns. Melting or Charring of any Part of the Surface. Snags, Punctures, Tears or Cuts. Broken or Worn Stitches. Wear or Elongation. Distortion 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 The center of gravity is considered to be where the entire weight of the load may be. The crane hook must be directly above the center of gravity of the load. Variations may cause tilting, stress on legs and potentially losing the load.

NUMBER OF LEGS AND ANGLES As the angle decreases, the rated capacity of the sling decreases. The smaller the angle, the greater the stress on the sling leg. Heavier loads can be safely moved if the weight of the load is distributed among more sling legs.

RATED CAPACITY Rated capacity of sling depends on type and size of sling and type of hitch. Manufacturers charts give ratings for new slings. Older slings must be used with more caution. Never exceed sling’s rated capacity.

HISTORY OF CARE AND USAGE Mishandling and misuse are the leading cause of accidents. Protect from sharp bends and sharp edges. Properly Secure. Accurately determine weight and balance. Do not allow load to drag on ground.

Proper Care, continued: Position hook directly over the load. Seat sling squarely in hook bowl. Take up slack slowly-avoid jerking. Check tension-raise slowly and check for balance. Keep all personnel clear. Always use tag lines.

ALWAYS OBEY THE NEVERS! Never allow more than one person to control a lift or give signals. Never raise the load more than necessary. Never leave the load suspended in the air. Never work under a suspended load.

MAINTENANCE OF SLINGS CHAIN SLINGS: Clean prior to each inspection. Look for Stretching, Binding, Wear, Nicks or Gouges. File heavy nicks and gouges, then check with caliper to ensure size is to recommendations. Check inside surface of links for wear.

Maintenance, continued: WIRE ROPE: Clean prior to each inspection. Lubricated to manufacturers recommendations. Lubrication reduces corrosion and wear due to friction. Rope should be dry before lubricating.

Maintenance, continued: Fiber Ropes and Synthetic Webs- are generally discarded rather than repaired. Always follow manufacturers recommendations.