Wire Rope

The norm is expressed as:

No. of strands x No. of wires per strand (refer to diagram above)

There are several geometric arrangements in the design of wire ropes, known as the construction of a wire rope. These include (not exhaustive) 6x19; 6x24; 6x25; 6x29; 6x36; 6x41 etc.

An additional acronym that is used in the expression of a wire rope construction (i.e. S, W or Fi) expressed the alignment of wires in a strand of a wire rope. This acronym is placed next to the numerical expression of the construction of a wire rope. The types of expression are :

So the full expression of a construction will look something like 6x29Fi ; 6x36WS.

The core forms the heart of the rope and is the support for the strands around it. The core may take one of the several forms :

• Fiber Core (FC),
• Independent Wire Rope Core (IWRC) - in 7 x 7
• Wire Strand Core (WSC) - in 1 x 7
• PVC - impregnated core (PVC) (IWRC)

The rope must possess sufficient strength to take the maximum load that may be applied, with a factor of safety of at least 5 to 1. In the case of carrying personnel, a factor of safety of 10 to 1 is recommended.

The wire ropes that are supplied as rigging on mobile cranes must possess factors of safety of 3.5 : 1 under operating conditions and 3 : 1 when erecting the boom.

As for wire ropes that are used as pendants or in standing conditions, a safety factor of 3 : 1 under oprating conditions is recommended, and 2.5 : 1 when erecting boom is recommended.

The Safe Working Load is defined as the strength of a wire rope to support the load upon the necessary factor of safety in a situation under consideration.

Therefore :

The term rope lay signifies the direction of the rotation of the wires and the strands in the rope. Rotation is either to the right (clockwise) or to the left(anticlockwise).

In Regular Lay Ropes, the wires in the strands are laid in one direction while the strands in the rope are laid in opposite direction. These ropes are stable, have good resistance to kinking and twisting and are easy to handle. They are also able to withstand considerable crushing and distortion due to the short length of exposed wires.

In Lang Lay Ropes, the wires in the strands and the strands in the ropes are laid in the same direction. With the outer wires presenting greater wearing surfaces, Lang Lay Ropes have greater resistance to abrasion. They are also more flexible and possess greater resistance to fatigue. They are more liable to kinking and untwisting and are not capable of withstanding the same abuse from distortion and crushing. Lang Lay Ropes should have both ends permanently fastened to prevent untwisting and as such they should not be recommended for use on single part hoistlines, swivel end terminals.

The following are representations of commonly-used wire rope lays :

Left Hand Ordinary Lay (LHOL/LHRL), Left Hand Lang's Lay (LHLL) Right Hand Ordinary Lay (RHOL/RHRL) Right Hand Lang's Lay (RHLL)

Several commonly used grades of tensile steel which are taken as acceptable standards in the manufacture of wire ropes include :

• 1570 N/mm²(160kg/mm²),
• 1770 N/mm²(180kg/mm²), also known as IPS
• 1960 N/mm²(200kg/mm²), also known as EIPS
• 2160 N/mm²(220kg/mm²), also known as EEIPS

• Galvanized;
• Ungalvanized;
• PVC-coated;
• Stainless Steel

Whilst JIS standard is the more widely-accepted standard in Malaysia, we have also the following available :

• Japanese Standard: JISG3525
• British Standard : BS302
• American Standard :API9A
• German Standard : DIN 3057,3058,3064,3069

Flexibility or Resistance to Bending Fatigue : the wire rope must have the ability to bend over small sheaves or wind onto relatively small drums without the wires breaking due to bending fatigue.

Strands containing a large number of small wires have greater resistance to bending fatigue than strands containing a few large wires.

Lang Lay has greater fatigue resistance than Regular.

Performing increases the wire rope's resistance to bending fatigue.

Large outer wires are better able to withstand abrasive wear.

Lang Lay provides greater resistance to wear than Regular Lay.

An Independent Wire Rope (IWRC) provides greater support for strands under heavy bearing pressure.

The coarser wire rope construction provide greater resistance to flattening on drums.

Ungalvanized 6x29Fi+IWRC

Ungalvanized 6x36WS+IWRC

Ungalvanized 6x37+IWRC

Ungalvanized 6x19S+PVC(IWRC)

Ungalvanized 6x29Fi+PVC(IWRC)

Galvanized 6x36WS+IWRC

Galvanized Swaged 4x39+FC

Ungal or Gal 19x7+IWRC

Galv. Compacted 35x7+IWRC

PVC-coated 6x7+FC

PVC-coated 6x19+FC

Stainless steel 7x7

Stainless steel 7x19