Drum
Spooling: What to Do
When you're installing
a new rope onto a crane, there's
a primary objective: spool the
rope onto the equipment tightly
without trapping any twist in
the rope on the drum. (See installation
guidelines for details.)
For multiple-layer spooling,
it's essential to get the first
layers of rope tight with each
wrap snug against the preceding
wrap. Since the first layer provides
the "grooving" for upper
layers, wraps must be placed tightly
together. If not, wraps in upper
layers will pull down between
wraps already on the drum, which
can cause crushing damage and
reduced rope strength and service
life.
When you encounter spooling problems,
check the following list to identify
the possible cause. If any of
these are incorrect, the result
can include open (or loose) spooling,
random spooling or stacking of
rope against drum flanges.
- Drum alignment.
Before spooling, make sure the
drum is level and at right angles
to the boom. Many drums are
mounted on the frame so that
adjustment can be made in alignment.
- Drum winding.
Wire rope should wind onto the
smooth-faced drum. Make sure
you wrap the rope left or right
and over or under as recommended.
- Use of a swivel.
A swivel end termination will
let the rope lay lengthen when
loaded. As the rope spools onto
a drum, the unlaid rope travels
over the point sheave and accumulates
between the drum and point sheave.
This leads to block rotation,
erratic spooling, unbalancing
and decreased rope service.
- Fleet angle.
One of the most important factors
in proper winding of rope on
drums. For smooth-faced drums,
this angle should be between
1/2º and 1 1/2º. For
grooved drums, it should be
between 1/2º and 2º
Fleet angles larger than these
can cause spooling problems
and the rope to rub against
the flanges of the sheave --
plus may lead to rope crushing
and abrasion on the drum. Fleet
angles smaller than these may
cause the rope to pile up at
the flanges.
- Point sheave.
When more than one sheave is
in use at the boomtip, make
sure the lead line presents
the optimum fleet angle to the
drum.
- Grooved drums.
Groove spacing must be adequate
to prevent the rope from crowding
out adjacent wraps as the rope
spools across the drum. In addition,
groove spacing must not be excessive,
which can allow wraps of the
next layer to pull down between
wraps of the previous layer,
causing abrasion and crushing.
- Drum flanges.
Flanges should be perpendicular
to the drum face and not worn,
deformed or spread outward.
These conditions can cause spooling
problems at the change-of-layer
point as additional layers are
spooled.
- Improper installation.
When a rope has been
installed in such a way that
twist has been introduced into
the rope, spooling problems
can result. (See installation
guidelines for details.)
- Riser strips and kick
plates. If spooling
problems persist after you've
considered the above conditions,
try using riser strips and kick
plates.
