OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

large ships. The disadvantage of the split drum is the more diflicult operation, a factor which can

be overcome with proper instructions and operator experience. Anor.her reason for their use is that

ISO Standard 3730, Annex A, recommends that synthetic ropes under tension should not be wound

OD a drum in more than ooe layer or shorl life wiU result, and this can normally only be avoided

by using spur drUIOs.

For either type of drum, the mlOlluum drum diameter should be 16 times the wire rope diameter.
Split drums should allow \0 turns of rope on the tension section.

While many VLCC owners and operators prefer {he split drum type, the undivided drum has its

proponents also. The following discusses the pros and CODS for each type and also discusses !.he

effects that the number of layers of wire on the tertSion or working drum has 00 each.

7.3.1 Split Drums

As shown in Figure 7.1 the split drum winch is a common drum divided by a notched flange into

a wire storage section and a tension section. It is operated with only one layer of wire on the

tension section and theorelically can maintain a constant, high brake uoJding power.

The split drum winch was designed as a solution 10 !.he spooJing problem encountered with undivided

drum winches. Wben wires are bandied directly off drums, (he final turns of thc outer layer when

under tension tended to bite into (he lower layers. This could result in possible wire damage and

difficulties when releasing the line. Also the mechanical spooling devices which were used on un-

divided drUIDS were round to be susceptible to damage.

Manual

Band Brake

Tension Drum

Cou rtesy of Pusnes

Storage Drum

FIGURE 7.1: THE SPLIT DRUM WINCH

Warping

rum End