Lay of steel wire rope

Types of lays affect how rope behaves. Find information here on ordinary lay, Lang's lay and pre-formed, post-formed and non-rotating ropes.

Lay is the spiral direction the wires are formed into strands and the strands are formed into the finished rope.

The strands can be laid or wound either to the left or right around the core of the wire rope. In left hand lay the strands are laid anti-clockwise, while in right hand lay they are laid clockwise.

Lay does not affect the Working Load Limit of the rope, but it does determine characteristics such as the spin of the rope. .

Types of lays

Ordinary lay

Ordinary lay is where the wires are laid in the opposite direction to the strands.

This is a right hand ordinary lay (RHOL):

Right hand ordinary lay

Most general-purpose ropes are right hand ordinary lay.

This is a left hand ordinary lay (LHOL):

Left hand ordinary lay

Lang's lay

Lang's lay is where the wires are laid in the same direction as the strands. For example, Lang's Lay may be used in passenger devices and chairlifts.

Lang's lay is used where both ends of the rope are fixed to prevent rotation. For example, for luffing. Lang's lay is not preferred to be used for lifting slings (refer to AS1666.1).

This is a right hand Lang's lay:

Right hand Lang's lay

This is a left hand Lang's lay:

Left hand Lang's lay

Pre-forming and post-forming

Flexible steel wire ropes used as crane rope and for slinging are either pre-formed or post-formed.

Pre-formed ropes have the spiral (helix) put in the individual wires before the wire is laid into the strand.

Post-formed ropes are put through a series of offset sheaves to bend the spiral into the individual wires after the rope is laid into the strand.

Rope being put through offset sheaves to bend the spiral

Pre-formed and post-formed ordinary lay ropes are more resistant to unlaying when cut than unformed or Lang's lay ropes.

Non-rotating ropes

Under load, all steel wire ropes have a tendency to unwind. This includes pre-formed, post-formed, ordinary and Lang's lay.

Note: these ropes should never be fitted with a swivel under service.

To minimise risk of wire rope rotating, non-rotating ropes are typically used to prevent twist or torque. Non-rotating ropes have the inner and outer strands laid in the opposite directions during manufacturer.

Non-rotating ropes are usually used as crane hoist rope.

Under strain, the opposite spiral in both the inner and outer layers are counter balanced and the rope has low rotation properties or torque neutral.

Typical non-rotating rope constructions are:

• 18x7
• 19x7
• 32x7, or
• 35x7

Here are images of a typical 35x7 non-rotating constructed wire rope. There is a total of 35 strands, each strand having 7 wires:

35x7 non-rotating constructed wire rope

When the layers of strands lay opposite to each other, they have a balancing effect. Tension is taken up in opposite directions, meaning the rope itself does not rotate. This is safe to use where it is critical to prevent loads, including personnel, from spinning.

Here is an image of non-rotating rope:

Non-rotating rope

This type of rope has a higher fill factor of steel, and as such has a higher breaking strain. This often means a smaller diameter rope can be used. Smaller diameter rope reduces weight off the crane boom and subsequent winch sizes.