SLINGS

SLINGS SAFETY

Rigging Equipment slings

The types of slings covered are those made from alloy steel chain, wire rope, metal mesh, natural or synthetic fiber rope (conventional three strand construction), and synthetic web (nylon, polyester, and polypropylene). 

Sling Inspection

Each day before being used, the sling and all fastenings and attachments shall be inspected for damage or defects by a competent person designated by the employer. Additional inspections shall be performed during sling use, where service conditions warrant. Damaged or defective slings shall be immediately removed from service.

alloy steel chain slings

•Adapts to shape of the load

•Can damage by sudden shocks

•Best choice for hoisting very hot materials

•When one link in a chain fails, the load will come down.

•

Must have an affixed tag stating size, grade, rated capacity, and sling manufacturer

It must be marked with grade or manufacturer's mark

 Inspection of Chain

Must be visually inspected prior to use.

Pay special attention to any stretching (any elongation from the original length.

The diameter of the worn chain link should be measured at the point of the greatest wear and compare with minimum allowable diameters in tables.

Chain Sling Wear Chart

Chain Size (inches)	Minimum Allowable Chain Size (Inches)	Chain Size (inches)	Minimum Allowable Chain Size (Inches)
¼   3/8    ½   5/8    ¾   7/8	15/64       19/64       25/64       31/64       19/32       45/64	1          1 1/8          1 ¼          1 3/8          1 ½          1 ¾	13/16          29/32          1          1 3/32           1 3/16           1 13/32

Wire Rope Slings

Strength — Function of size, grade, and construction.  It must be sufficient to accommodate the maximum load that will be applied. The maximum load limit is determined by means of a multiplier.  This multiplier is the number by which the ultimate strength of a wire rope is divided to determine the working load limit.  Thus a wire rope sling with a strength of 10,000 pounds and a total working load of 2,000 pounds has a design factor (multiplier) of 5.  New wire rope slings have a design factor of 5.  As a sling suffers from the rigors of continued service, the design factor and the sling's ultimate strength are proportionately reduced.

Fatigue — A wire rope must have the ability to withstand repeated bending without the failure of the wires from fatigue.  Failure is the result of the development of small cracks under repeated applications of bending loads.  It occurs when ropes make small radius bends.  The best way to prevent this is to use blocking or padding to increase the radius of the bend. 

Abrasive Wear — The ability to withstand abrasion is determined by the size, number of wires, and construction of the rope.  Smaller wires bend more readily and therefore offer greater flexibility but are less able to withstand abrasive wear.  Conversely, larger wires of less flexible ropes are better able to withstand abrasion. 

Abuse — Abuse will cause a wire rope sling to become unsafe long before any other factor.  Abusing a wire rope sling can cause serious structural damage to the wire rope, such as kinking or bird caging which reduces the strength of the wire  rope.  (In bird caging, the wire rope strands are forcibly untwisted and become spread outward.)  Therefore, in order to prolong the life of the sling and protect the lives of employees, the manufacturer's suggestion for safe and proper use of wire rope slings must be strictly adhered to.

 Inspections

-Each day before use, the sling, all fastenings and attachments must be inspected by a competent person

-Additional inspections performed during use, where conditions warrant

-Damaged slings must be removed from service

Wire rope clips

When using U-bolt wire rope clips to form eyes, ensure the "U" section is in contact with the dead end of the rope

Lubrication

Regularly lubricate ropes and chains

Remove From Service When

6 broken wires in 1 lay

3 in one strand

Outer wire diameter worn 1/3 original diameter

Bird caged , crushed, kinked 

Synthetic Web Sling Markings

•Mark or code to show:

Ø-Name or trademark of manufacturer

Ø-Rated capacities for the type of hitch

Ø

-Type of material

Synthetic Web Sling Stitching

The thread shall be in an even pattern and contain a sufficient number of stitches to develop the full breaking strength of the sling.

Synthetic Web Slings - Remove from Service

•Remove from service if any of these are present:

ØAcid or caustic burns

ØMelting or charring of any part

ØSnags, punctures, tears or cuts

ØBroken or worn stitches

ØDistortion of fittings

This sling should be removed from service. The red wear threads (red arrow) are showing through and there is obvious damage to the sling

NOTE:A 1000 lbs load is lifted using two true vertical hitches; the load is evenly divided between the two legs. However, go from a true vertical hitch to a non-vertical hitch, the load applied to the legs increase as the horizontal angle degrees.