Wire Rope - Lay and Construction
Lay of Wire Rope
The lay of a wire rope describes the manner in which either the wires in a strand, or the strands in the rope, are laid in a helix.
Left and right hand lay
Left-hand ordinary lay (LHOL) wire rope (close-up). Right-hand lay strands are laid into a left-hand lay rope.
Right-hand Lang's lay (RHLL) wire rope (close-up). Right-hand lay strands are laid into a right-hand lay rope.
Left hand lay or right hand lay describe the manner in which the strands are laid to form the rope. To determine the lay of strands in the rope, a viewer looks at the rope as it points away from them. If the strands appear to turn in a clockwise direction, or like a right-hand thread, as the strands progress away from the viewer, the rope has a right hand lay. The picture of steel wire rope on this page shows a rope with right hand lay. If the strands appear to turn in an anti-clockwise direction, or like a left-hand thread, as the strands progress away from the viewer, the rope has a left hand lay. (The rope in the left hand lay photo shows one left hand lay rope from left to right and top to bottom, with 5 right hand lay strands, and part of a sixth in the upper left. It is not 5 right hand lay ropes adjacent to each other.)
Ordinary, Lang's and alternate lay
Ordinary and Ducay's lay describe the manner in which the wires are laid to form a strand of the wire rope. To determine which has been used, first identify if left or right hand lay has been used to make the rope. Then identify if a right or left hand lay has been used to twist the wires in each strand. (On ordinary lay, the outer wires approximately follow the alignment of the rope: with Lang's lay they are cross at an angle of about 45°.) Lang's laid rope is able to flex over sheaves more easily (with less damage) but it has the disadvantage of having a high torque tendency (it tends to untwist when tension load is applied) compared with ordinary laid rope. Untwisting can be dangerous with a steel-cored rope: load is shed from the strands and may cause the core to fail as it becomes higher loaded. For this reason, swivel termination units can be dangerous.
|The lay of wires in each strand is in the opposite direction to the lay of the strands that form the wire.
|The lay of wires in each strand is in the same direction as the lay of the strands that form the wire.
|Strands alternate between Lang's lay and ordinary lay; e.g.: in a 6-strand wire, 3 strands are ordinary lay, and 3 are Lang's lay.
|Alternate term for ordinary lay.
|Archaic term for Lang's lay.
|Alternate term for alternate lay.
|This is not a term used to classify a lay as defined in this section. It refers to a specific construction type of wire rope.
Construction and specification
The specification of a wire rope type – including the number of wires per strand, the number of strands, and the lay of the rope – is documented using a commonly accepted coding system, consisting of a number of abbreviations.
This is easily demonstrated with a simple example. The rope shown in the figure "Wire rope construction" is designated thus: 6x19 FC RH OL FSWR
Wire rope construction
|Number of strands that make up the rope
|Number of wires that make up each strand
|Right hand lay
|Galvanized Steel Wire Rope
|Flexible steel wire rope