Winding on smooth or flat faced
drums
Start winding the rope in a straight helix angle. To assist with this, some
drums have a tapered steel part attached to one flange which 'fills' the
gap between the first turn and the flange (see picture 7).
The first layer must be wound tight and under tension. Take a mallet or
a piece of wood and tap the wraps tightly against each other (see picture
1); but not so tight that the rope strands interlock (see picture 2), but
tight enough that the rope can't be shifted on the drum. If the first layer
is wound too loose, the next layer will wedge a gap into the first layer
causing that layer to 'pull in' (see picture 3). A too tightly wrapped first
layer will not allow the next layers enough space between wraps (see picture
2).
In any case, the first layer, as well as all of the layers, must be wound
on to the drum with sufficient pre-tension (5-10% of the rope's WLL is a
good measure). If wound with no tension at all, the rope is subjected to
premature crushing and flattening caused by the 'under load' top layers
(see picture 4).
Even if wound on properly during installation, the first layer will loosen
somewhat during service. When the first layer becomes slack (the pre-tension
is gone), this initial procedure MUST be repeated in regular intervals.
Otherwise, the tensioned 'hard' wraps will severely crush the bottom layers
(picture 5). |
|
Winding on grooved drums
Basically, follow the same procedure as for smooth drums. Also here, pre-tension
is of utmost importance.
If the first layer, or layers, are only used from time to time, they will
loose their tension on the drum and start to flatten out due to the high
pressures of the loaded layers. Repeat this pre-tensioning procedure regularly.
As with tower cranes, for example, which have a long rope length installed
and rise as the building goes up, pre-tensioning will not be possible. In
these cases it may be advisable to install a shorter rope length first.
Otherwise, you may have to replace the entire rope length because of crushing
and flattening of the bottom layers. If this not possible, extra care must
be taken to pre-tension the rope on the drum during installation.
Whatever you do, DO NOT run the rope through a 'tightening' device (see
picture 6), e.g. two wooden blocks clamped together. YOU WILL DESTROY
THE ROPE! |
