Smooth spooling of wire rope on a winch drum is crucial to

WI NCH ES
Smooth spooling of wire rope
on a winch drum is crucial
to maximise rope life. CRIS
SEIDENATHER answers some
frequently asked questions
Spools out
Why is it necessary to break in a new
rope?
A new rope needs to be run through its operating
cycle several times under light load and reduced
speed. This allows the rope to adjust itself to
the working conditions and enables all strands
and wires to become seated. Depending on rope
type and construction, some stretch and a slight
reduction in diameter will occur as the strands and
core are compacted. Breaking in makes the rope
less liable to be damaged when full load is applied.
In many cases the equipment has to be tested
prior to use. During the test, the equipment gets
purposely overloaded to varying degrees. The
magnitude of overloading depends on the type and
capacity of the lifting equipment.
Never test equipment before the rope has been
broken in. Overloading a rope that has not yet been
broken in may inflict permanent damage to it. This
is especially important in multi-layer spooling as
severe overload of the top layers may damage the
lower ones and/or crush the rope.
If possible, the winch should be tested with the
rope spooled on the first drum layer only.
degrees. Where the speed is low and the load
is high, the fleet angle should be towards 1.5
degrees. In borderline cases, a specialist should be
consulted.
What tension is required when putting
wire rope onto a drum?
The cable should be spooled with a minimum
tension of either a) 10% of working load or b) 1%
to 2% of the rope’s breaking strength, where the
breaking load to working load safety factor is 5 to
1 the higher factor (a or b) must be used. Where
safety factors are 3 to 1 or less, the tension should
be about 30% of the maximum load. The smaller
the D:d (i.e. the smaller the drum), the more tension
is needed.
A factor to consider is the D:d ratio, where D is
the drum diameter and d is the diameter of the wire
rope. The ideal D:d is 23:1. Where the D:d ratio is
smaller (i.e. where the drum is small) more tension
is needed.
In any case, hand spooling will not give the
required tension. The use of another hoist, or
storage reel with capstan, is advisable. For this
reason, it is best to plan ahead.
What is the significance of fleet
angles?
The fleet angle refers to the angle at which the
rope comes off the sheave onto the winch. It is
measured between the first fixed sheave and the
flange of the winch. Correct fleet angle is crucial to
smooth spooling. If the rope comes onto the drum
at the wrong angle, the rope is likely to experience
spooling problems and rope life will be affected. For
a winch with Lebus grooving, experience has shown
that the angle should be between 0.5 degrees
and 1.5 degrees. At the same time, however, the
design, tension and speed of the cable must be
taken into account.
Where the speed is high and the load value
is low, fleet angle should be more towards 0.5
Copyright of KHL Group International Cranes and Specialized Transport
IC 0706 Winches.indd 33
Are hard ropes better than soft ropes?
In multi-wrap applications the general answer is
yes, because hard or stiff ropes (compacted ropes)
are better able to withstand the crushing effects
of the outer layers than more flexible ropes and so
are more likely to retain their roundness rather than
deform to oval like an egg. The harder and rounder
the rope, the better the pyramid shape as each
layer of rope is added onto a parallel grooved drum.
However, a compromise is needed because the rope
also needs to be sufficiently soft and flexible to wrap
around the drum and stay in the groove, or on outer
layers to follow the perfect smooth spooling pattern.
What causes mis-spooling?
There are five classes of problem that either alone
or in combination can cause mis-spooling. These
are:
■ Wrong rope
Mis-spooling sometimes occurs when a new
rope is installed that is slightly larger in diameter
than the groove pitch. Check that the rope is
staying in the grooves in the first layer.
■ Wrong drum or D:d ratio
Mis-spooling may also occur when the rope
becomes worn and its diameter is reduced. Look
for the rope beginning to lie low in the wraps
adjacent to the drum flange and/or any cuttingin of the rope.
■ Wrong fleet angle
If the fleet angle is too large or too small the
rope will not spool correctly.
■ Wrong tension
Slack line may have worked its way down into
the dead turn, causing the rope to miss a wrap
by a rope being high or misplaced.
■ Wrong operator
Human error.
Wrong rope, wrong drum design (including wrong
D:d), wrong fleet angle, tension problems,
■
incompetent operator.
INTERNATIONAL CRANES AND SPECIALIZED TRANSPORT ■ JULY 2006
33
04/07/2006 15:22:23