WIRE ROPE SLING RESOURCES
Grommets
Wire Rope Slings
GROMMETS
Grommets are a unique type of sling. They form a complete circle and automatically double the number of lifting legs. Several types are available, such as strand laid hand tucked, strand laid mechanical, cable laid hand tucked and cable laid mechanical. Grommets work well in basket and choker hitches and general applications will find them used in this manner. Another unique advantage to grommets is that the load contact points may be rotated or moved around the sling to even out the wear points. The only area that should not come into contact with the load is the splice area. The sling manufacturer will usually mark the area of hand tucked grommets with paint to help the user more easily identify the splice area.
Tolerances for grommets are generally plus or minus 1% of the circumferential length or 6 body diameters whichever is greater.
A minimum circumference of 96 body diameters is recommended. This measurement is normally an inside circumferential measurement. The requirement for a minimum circumference of 96 times the body diameter for grommets and endless slings was based on the requirement to have at least three free rope lays on either side of the tuck of a hand spliced endless grommet prior to being bent around a hook or pin five times the body diameter. To eliminate the possibility of confusion, this requirement was adopted for mechanically spliced endless grommets as well. Consult the sling manufacturer for smaller circumferences.
The same general precautions apply to grommets as apply to all other types of slings. However, it should be noted that since a grommet is a continuous circle, the D/d ratio becomes a very important consideration. The D/d ratio must be applied to the lifting pins as well as to the load. Normally the lifting pins will be the smallest diameter in the system other than the diameter of the grommet. No loads should be handled on D/d smaller than 5 times the sling body diameter. If they must, consult the sling manufacturer. Rated capacities covered in this section are based on a D/d ratio of 5.
STRAND LAID HAND TUCKED GROMMETS are made from one continuous length of strand. No sleeves are used to make the joint. This results in a very smooth circular sling. Because of the sling body construction, grommet slings react differently than standard wire rope slings in a choker type hitch therefore the presence of the nominal splice efficiency factor in the equation. Rated capacity adjustment Table 1 applies.
STRAND LAID MECHANICAL SPLICE GROMMETS are made from one continuous length of wire rope joined by pressing or swaging one or more sleeves over the rope juncture. This type of grommet is not as smooth as the hand tucked, but offers economy and ease of manufacture. An advantage is that the swaged sleeves give clear indication of the splice area.
CABLE LAID HAND TUCKED GROMMETS are fabricated in the same manner as strand laid hand tucked grommets except one continuous length of wire rope is used. This makes for a flexible smooth sling. The body diameters are somewhat odd sized because the grommet body is built up from a standard diameter component rope.
CABLE LAID MECHANICAL SPLICE GROMMETS are fabricated from one continuous length of cable laid wire rope fabric with the ends joined by one or more mechanical sleeves. They are similar to strand laid mechanical splice grommets, but offer greater flexibility. (See Rated Capacity Tables Section)
| TABLE 7 | |||
| NOMINAL SPLICE EFACIENCIES CABLE LAID HANO TUCKED GROMMETS | |||
| Rope Ola. | Nominal Eff. Factor | Rope Dia. | Nominal Eff. Factor |
| 3/8 | .78 | 1 11/16 | .750 |
| 9/16 | .78 | 1 7/8 | .745 |
| 5/8 | .78 | 2 1/4 | .735 |
| 3/4 | .775 | 2 5/8 | .725 |
| 1 5/6 | .770 | 3 | .715 |
| 1 1/8 | .765 | 3 3/8 | .705 |
| 1 1/2 | .755 | ||