terminals must be proof-tested before placing the sling in initial service.

The COMSECOND/COMTHIRDNCBINST 11200.11 has rated capacity charts enclosed for numerous wire rope classifications. You must know the diameter, rope construction, type core, grade, and splice on the wire rope sling before referring to the charts. The charts provide you the vertical-rated capacity for the sling. The test weight for single-leg bridle slings and endless slings is the vertical-rated capacity (V. R. C.) multiplied by two or (V.R.C. x 2 = sling test weight).

The test load for multi-legged bridle slings must be applied to the individual legs and must be two times the vertical-rated capacity of a single-leg sling of the same size, grade, and wire rope construction. When slings and rigging are broken out of the TOA for field use, they must be proof-tested and tagged before being returned to CTR for storage.

Check fiber line slings for signs of deterioration caused by exposure to the weather. Ensure none of the fibers have been broken or cut by sharp-edged objects.

SLING SAFE WORKING LOADS

There are formulas for estimating the loads in most sling configurations. These formulas are based on the safe working load of the single-vertical hitch of a particular sling. The efficiencies of the end fittings used also have to be considered when determining the capacity of the combination.

The formula used to compute the safe working load (SWL) for a

BRIDLE HITCH with two, three, or four legs (fig. 6-17) is SWL (of single-vertical hitch) times H (Height) divided by L (Length) times 2 = SWL. When the sling legs are not of equal length, use the smallest H/L measurement. This formula is for a two-leg bridle hitch, but it is strongly recommended it also be used for the three- and four-leg hitches.

NOTE: Do NOT forget it is wrong to assume that a three- or four-leg hitch can safely lift a load equal to the safe load on one leg multiplied by the number of legs.

Other formulas are as follows:

Single-basket hitch (fig. 6-18):

For vertical legs:

SWL = SWL (of single-vertical hitch) x 2.

For inclined legs:

SWL = SWL (of single-vertical hitch) x H divided by L x 4.

Double-basket hitch (fig. 6-19):

For vertical legs:

SWL = SWL (of single-vertical hitch) x 4.

For inclined legs:

SWL = SWL (of single-vertical hitch) x H divided by L x 4.

Single-choker hitch (fig. 6-20):

For sling angles of 45 degrees or more:

SWL = SWL (of single-vertical hitch) x 3/4 (or .75).

Sling angles of less than 45 degrees are not recommended; however, if they are used, the formula is as follows:

SWL = SWL (of single-vertical hitch) x A/B.

Double-choker hitch(fig. 6-21):

For sling angle of 45 degrees or more:

SWL = SWL (of single-vertical hitch) x 3 divided by 4 x H divided by L x 2.

Sling angles of less than 45 degrees:

SWL = SWL (of single-vertical hitch) x A divided by B x H divided by L x 2.

When lifting heavy loads, you should ensure that the bottom of the sling legs is fastened to the load to prevent damage to the load. Many pieces of equipment have eyes fastened to them during the process of manufacture to aid in lifting. With some loads, though, fastening a hook to the eye on one end of each sling leg suffices to secure the sling to the load.

Use a protective pad when a fiber line or wire rope sling is exposed to sharp edges at the comers of a load. Pieces of wood or old rubber tires are fine for padding.

SLING ANGLE

When using slings, remember that the greater the angle from vertical, the greater the stress on the sling legs. This factor is shown in figure 6-22.