15 August 2002
FITTINGS, SHIP BLOCKING, SUPPORTING FACILITIES AND SHIP SERVICES
FITTINGS. Major fittings, and fittings peculiar to graving docks, are
covered in this section; other fittings are merely mentioned. All fittings must be made of
corrosion resistant materials and installed in a way that will minimize maintenance.
Ferrous metal fittings must be zinc coated; small fittings may be cadmium plated.
Capstans. Capstans are used at graving docks for pulling vessels into
the dock chamber, and entrance caissons into seat or stowed position.
Location. Locate one capstan on the centerline of the dock at the head
end; one at each side of the caisson seats at the entrance end; and others on the sides
of the graving dock, spaced not more than 91.44 m (300 ft) apart. Set capstans
shoreward of the outermost crane rail of the track nearest to the centerline of the dock.
Requirements. Use capstans of the reversing gypsy-head type
consisting of a barrel mounted on a vertical shaft and driven by a two-speed squirrel-
cage induction type electric motor through reduction gearing. For electric control should
be by means of 460-volts, three-phase 60 Hertz current, a magnetic reversing
controller, including transformer and relay cabinet, push-button station and flexible cord,
providing for full voltage starting at both speeds. Arrange the completed equipment to
operate with a minimum of noise and vibration.
Arrange all parts subject to wear so that they may be accessible for
inspection, lubrication, and cleaning. Secure all fastenings that are likely to become
loosened by vibration by locknuts or other suitable devices. Use material commonly
used for the service required and marine environment. The entire capstan unit should
be designed and furnished by the same fabricator. Templates should be furnished for
setting anchor bolts.
Capacity and Speed. Capstans must be capable of pulling up to 13,500
kg (30,000 lbs) at a line speed of 0.1524 m/s (30 fpm) and up to 6750 kg (15,000 lbs) at
0.3048 m/s (60 fpm) with slack speed of 0.4572 m/s (90 fpm). Design capstans to also
be used as bollards with a line pull of 45,000 kg (100,000 lbs) applied at the center of
the barrel and directed upward at an angle of 30 degrees with the horizontal. Any
required variations in the above indicated line pulls and speeds will be specified in
Capstan Pits. Locate capstan driving mechanisms and foundations
below coping elevation in pits generally consisting of shallow concrete chambers
founded on heavily reinforced concrete slabs firmly anchored and supported by batter
and vertical piles. To avoid interference with lines, expose only the capstan barrel and
the watertight cover of the capstan pit.