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 TB 740-97-4
such that the sheet metal cover fits snugly over the vertical faces. The cover will be fastened to the coaming by No. 12
sheet metal screws spaced approximately 2 feet apart. The cover will be provided with three holes: one to introduce the
moist air return duct; another for the humidistat cable; and the third for mounting the sensing element. Apertures between
the coaming and the deck will be filled with bituminous coating. All other joints and seams will be covered with strippable
coating and bituminous coating.
(t) Dehumidification piping system The connecting points of all air ducts to areas being dehumidified will be
sealed with strippable coating and bituminous coating. The sealing will be carried over and around flanges, adapter, and
other devices used to attach or introduce the ducts. All joints and seams in the ducts will be similarly sealed.
(u) Miscellaneous sealing . Window drain holes and openings resulting from removal of windshield wipers,
horn, searchlights, and other such items will be sealed with strippable coating. All other exterior openings that led to
dehumidified areas and not specified herein will be sealed with strippable coating and bituminous coating.
(4) Dehumidification installation.
(a) Dehumidification machine No. 1 . A package dehumidifier, single desiccant bed, absorbent type, 10,000
cubic foot capacity, 110-volt, alternating current will be installed generally as shown on figure 22. The machine will be
mounted on a stand and protected with a cover fabricated in accordance with figure 24. An extension, terminating in a 90
elbow, will be fitted to the reactivation air outlet on the dehumidification machine in order to extend the outlet beyond the
exterior side of the sheet metal cover. The elbow will be turned away from the reactivation air inlet side and turned
downward 45to prevent the direct entry of water.
(b) Duct installation No. 1. Four-inch diameter, No 26 gage galvanized sheet metal ducts with necessary ells,
reducing fittings and connections will be installed generally as shown on figure 22. A pilothouse window will be secured in
open position ' and the opening will be blanked with galvanized sheet metal or exterior grade plywood. The blank will be
provided with a hole of sufficient size to permit the introduction of the dry air duct. The blank will be secured in the window
and sealed with strippable coating and bituminous coating. The ductwork will be run up the stairway from the main deck to
the pilothouse. A duct will be run from the anchor windlass cover to the moist air return connection on the
dehumidification machine.
(c) Dehumidification machine No. 2 . A dehumidification machine, similar to that described in (a) above and
with a similar stand and cover, will be installed generally as shown on figure 23.
(d) Duct installation No. 2. Ductwork, of a similar type and size and with similar fittings and connections as
they described in (b) above, will be installed generally as shown on figure 23. The dry air duct will be introduced into the
hole provided in the blank on the skylight. The moist air return duct will be run from the blank on the portside aft fire
monitor to the dehumidification machine.
(e) Dehumidification machine No. 3 . A dehumidification machine, similar to that described in (a) above and
with a similar stand and cover, will be installed generally as shown on figure 23.
(f) Duct installation No. 3. Ductwork, of a similar type and with similar fittings described in (b) above, will be
installed generally as shown on figure 23. The afterpeak hatch cover will be removed and stowed in the stores place. A
galvanized sheet metal or exterior plywood blank will be installed over the hatch opening. The blank will be sealed with
strippable coating and bituminous coating. It will be provided with a hole of sufficient size to introduce the dry air duct, and
a hole of sufficient size to mount a sensing element contact. The hatch cover to the store area will be removed and stowed
below in the stores space. The resulting opening will be covered with a blank fabricated from galvanized sheet metal or
exterior grade plywood. The blank will be sealed with strippable coating and bituminous coating It will be provided with
three holes: one, of sufficient size to introduce the moist air return duct; another, to permit passage of the humidistat cable;
and the third, to permit the mounting of a sensing element Vessels of the first flight will have the steering ram under
dehumidification. Dry air will go from the dehumidification machine to the starboard side of the hydraulic ram cover. The
moist air return line will run from the portside of the hydraulic ram to the afterpeak hatch blank. For vessels of the second
flight, dry air will go directly from the machine to the afterpeak hatch blank.
(g) Machite connections. Connection of ducts to the dehumidification machines will be made of unions or slip
joints connections which permit easy removal of the machines for servicing.
Change 2 G-3
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