Installation on drum
When the rope is coiled on a drum, it is bent and slightly twisted: a drum with right pitched
grooves induces untwist into a left hand lay rope, a drum with left pitched grooves
induces untwist into a right hand lay rope.
When the rope leaves the drum, a certain amount of additional twist builds up in the rope.
Redaelli fully non rotating wire ropes are specially designed to resist the additional twist
so as not to affect the performance of the product.
As a general rule, for the coiling operation on a single layer grooved drum having a right
hand pitch, a left hand lay rope is recommended. Similarly, for a grooved drum having a
left hand pitch, a right hand lay rope should be used.
The general rule must be observed with fully non-rotating ropes like Flexpack to avoid
permanent changes of the structure of the rope. These ropes are particularly sensitive to
twist, since their core is closed in the opposite direction to the outer strands.
With non rotation-resistant ropes (RED1 or PACK9), which have a good degree of compactness
and robustness, the use of a rope with the apparent wrong direction of lay
according to the general rule may be allowed.
In the case of coiling on multiple-layer grooved winches (like Lebus models), the direction
of the lay is not strictly determined by the direction of the pitch of the grooves in the drum.
In some particular cases, it could be advantageous to select a rope having the same lay
direction of the layer that is more frequently wound and unwound on the drum.
In the case of multiple layer on plain drums, it is recommended to design the rope length
in order to utilize the first layer as a bedding for the following ones. This layer should also
be painted in order to clearly identify it and to avoid to utilize it for the working operations.
When installed on the drum, the wire rope must be properly tensioned in order to allow a
correct coiling and uncoiling operation.
The preload or “backtension”, which is the load on the cable on the cable drum, should be at least 2% of the minimum breaking force or 10% of the working load
limit (considering the highest among the two values).
Every rope should be trained before use.
A wire rope is composed of several components (wires, strands, core), which have been
laid, during the production, using forces which are much lower than those applied during
The rope denotes a non linear behavior at very low tension, while for higher values of load
and further loading cycles, it keeps the memory of the solicitations and shows a progressive
reduction of the non-linear portion of the curve with the reduction of the total rope
This behavior is due to the fact that at low tensions some wires or strands are more stressed
than others, while at higher tension values the rope stabilizes and its components have
a better cooperation level.
The torque produced by the rope depends on torque factor, diameter and tension, which
is proportional to the depth.
The rope rotation is proportional to the torque and depends on the rope rotation factor
For more details regarding wire rope torque, see the dedicated section of this catalogue.
In Abandonment and Recovery application, before the beginning of pipeline abandonment,
the rope should be lowered in single fall configuration at the same depth required
for abandonment and left in such a position for some minutes in order to allow the
elimination of its inertial movement, then it must be re-wound on the winch. To achieve a
full balance, these lowering and re-winding operations should be performed 3 times.
During the last preliminary winding cycle, it is useful to paint a straight line parallel to the
winch axis for each rope layer, which will be used as a reference to monitor the possible
wire rope rotation.
It is important to remark that, since after the rope torsional stabilization the storage winch
contains a geometrically distorted rope, the rope must always be under tension to avoid
the generation of twists and kinks.
The maximum operating depth of the rope must be determined depending on the rope type.
Typically, 6 strand ropes can work up to 1300 m depth, 8 strand ropes up to 1000 m, non
rotating ropes have no practical limitations.