15 August 2002
fasteners. For all wedges and seating surfaces where sliding occurs, the
use of a metal sliding against a metal of the same alloy composition may
create galling problems. Use metals of different alloy composition or the
same metals with different hardnesses and anchor these seating surfaces
with dovetail grooves. For specific wearing problems, consult a
Draft Gages. Provide dock water level indicators as follows:
On each side of drydock walls near the entrance and also on each side of
dock walls near the head end. The indicators must be clearly visible from
the opposite side at the top of a drydock.
Mark gages with numerals 152.4 mm (6 in) high, with the bottoms of
numerals corresponding to multiples of one foot of draft.
The gages may be cast as recesses in wall concrete and painted, colored
tile cemented into a wall, or noncorrosive metal anchored into the
Vents. Vents must be provided behind each gate, leading from water duct
soffits to the free atmosphere on the coping where the vent openings shall be covered
by grating. A vent must be located at the highest point of a soffit before it curves down
into the flooding culverts proper.
Flooding Culverts. One of the two following types of culverts may be
used to conduct flooding water from entrance works into a drydock chamber.
Sidewall Type. Sidewall culverts are located in the lower parts of
sidewalls, connected to the sea through the entrance works. Floor openings and one or
two large sidewall openings are connected to them.
Advantages. This arrangement achieves filling without dangerous
currents. A flooding culvert often serves in part as a drainage and/or dewatering
culvert. The use of floor openings for filling provides a blanket of water to cushion the
force of water from the outlets and also flushes the floor drains.
Flooding Design. In a flooding culvert, maximum velocity occurs during
early flooding stages and is gradually reduced by loss of head resulting from the rising
water level inside a dock. The flooding time is greatly affected by the flow rate at
reduced heads when a dock is nearly full. Therefore, large culverts and openings are
Reduction of Obstructions
. It is important
to reduce friction, eddy
currents, and turbulence, by making interior surfaces of culverts smooth and all changes
of direction by means of gradual curves.