28 July 2005
The capstan, receiving several winds of the messenger line, provides the pulling
power needed to draw out the wire rope hawser. The messenger line is then
returned to the ship. Capstans are also used as primary guidance (breasting and
in-haul) to berth ships in drydocks and slip-type berths (Trident facilities). For
these uses, the capstans are of larger capacity and are typically two-speed.
The quick-release hook, generally mounted on a swivel base, is a deck fitting
used to receive mooring lines. When a ship is required to make a hasty
departure from its berth, a tug on the hook's release mechanism unfastens the
mooring line. The mechanism can also be tripped from the ship when a tag line
is provided. Thus, a ship can make a sudden departure without the assistance of
shore personnel. Quick-release mooring hooks with integral power capstans are
necessary for securing the steel mooring lines on petroleum tankers at fuel piers,
while bollards are needed for the supplementary lines other than steel.
The required strength of mooring hardware and its fastenings is determined by
the breaking strength of the strongest mooring line or lines that may be fastened
to it. Mooring hardware can and does receive more than one line and as many
as three are not unusual. The sizes of mooring lines are limited to those that can
be conveniently handled by deck hands. Thus, wire rope lines generally do not
exceed 1-3/4 in. diameter.
If a berthing facility were always to receive the same class of ship, each of which
had identical arrangements for putting out mooring lines, a specific pattern for
mooring hardware spacing, based on the ship's fittings, would be satisfactory.
However, most naval berthing facilities require a high degree of flexibility in order
to be able to receive several types and sizes of ships. Therefore, a universal
pattern for mooring hardware spacing is preferred. Mooring hardware spaced at
60 ft on centers along the berthing face of a structure will, in most instances,
provide the number of fittings required to secure the ships during the periods of
time that wind velocities and conditions of sea do not exceed the design criteria
established for mooring service types I and II. Mooring service types III and IV
will likely require additional high capacity storm bollards which are normally set
back at least 100 feet from the face of the berth to provide a shallow line angle.
a. A berthing facility that will accommodate ships having large wind
presentments, such as aircraft carriers, should be outfitted with 12 100
ton bollards at 100-ft (30.5 m) centers and 4 200 ton storm bollards at
each end. Locate the storm bollards, which would be used to secure
breasting lines, inshore from the face of the wharf, thus reducing vertical
angles and permitting the use of longer (safer) mooring lines.