A conductor consists of several twisted strands, the
individual wires change their position with varying
degrees of frequency between bending and
compression areas, so that the tensile and compression
stress virtually offset each other.
Consequently, such offsetting processes can take place
more frequently if the length of lay is shortened.
By this way, all handling cables from NEXANS are
optimized regarding the best bending qualities and
flexibility for reeling and festoon applications.
Direction of lay
The stranding of a conductor is clearly
defined when the twisting direction of
the strand is also defined.
The two possible twist directions are
usually indicated with the letters S and Z,
respectively (regardless of the observer’s
position).
Right Hand Lay or “Z” direction
Left Hand Lay or “S” direction
Length of lay
The length of lay is defined as the
quantifiable twist completed by a strand
around the conductor axle, as measured
in the axial direction. Frequently, the
length of lay is also measured as a
multiple of the conductor diameter: e.g.
10 x D.
Frequently used strands and ropes
Bunched wires
This type of conductor is characterized by the fact that the position of individual wires is not clearly defined.
Any number of wires can be bundled and twisted – they are bunched.
Copyright © July 2008 - Nexans
Copyright © July 2008 - Nexans
Nexans uses this conductor type in their flexible handling cables only for ≤ 10 mm2.
Concentric rope lay conductors
Rope-lay conductors consist of a number of rope-lay
elements characterized by regular concentric
stranding layers. Within the stranded conductor, the
position of each member in relation to its
neighbouring members is clearly defined. Rope-lay
conductors are characterized by uniform surface and
almost roundness.
Definition
Equal-lay
For the different applications we find following
various rope-lays:
Reversed-lay
All lay directions in the strand
and rope lays are uniform
The lay directions of the
individual layers in the rope-lay
conductor alternate.
However, the lay direction in the
rope lay still corresponds to that
of the respective strand layer
Z
Rope
lays
Characteristics
Z
S
Z
1st layer
(6)
2nd layer
(12)
Z
Z
Z
Rope
lays
Z
Z
Strand
- High flexibility
Z
S
Center
(1)
Strand
Z
S
Z
Design
Z
S
Z
Z
Z
Alternate lay directions in
successive layers of the strand
and opposite lay direction of
rope-lays and stranded layers.
Z
Z
Z
Cross-lay
Center
(1)
1st layer
(6)
2nd layer
(12)
Z
S
Z
Rope
lays
S
Z
Strand
- Good flexibility
- Resistant refering to torsional
stress
- Good axial compression and
bending strength
In the case of a 3 layer design, the 3rd layer is Z stranded.
The inner layers are in the same direction as shown in the drawings.
Center
(1)
1st layer
(6)
2nd layer
(12)
S
Z
S
S
Z
- Very resistant refering to
torsional stress
- Very good axial compression
and bending strength
Copyright © July 2008 - Nexans
Rope-lay
type
Its bending stability is high; its shape stays round and
circular.