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 TB 740-97-4
element contact. The blank will be sealed with strippable coating and bituminous coating.
(b) 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, adapters, and other devices used to
attach or introduce the ducts. All joints and seams in the ducts will be similarly sealed.
(c)
Miscellaneous sealing . Edges of doors, portlights, hatches, hoods, ventilation openings having installed covers, and
all other openings, in the nature of seams or joints between closely opposed surfaces, will be sealed with strippable coating and
bituminous coating.
(5) Dehumidification installation.
(a)
Main dehumidification system . A rotary, desiccant, electric dehumidifier, solid wheel type 20-153, 150,000 cubic
feet capacity, 440-volt, alternating-current, 60-cycle, 3 kW, will be installed atop the main deckhouse, generally as shown on figure
54. Install an electrical system whereby the operation of the machine and the fans specified in (3) above will be controlled by the
humidistat specified in (e) below, without overload of any component. The bottom plate will be removed from the ventilator located
aft of the midship deckhouse, tagged, and stowed within the deckhouse. A steel metal flange, fabricated and fitted in accordance
with figure 57, will be installed in place of the ventilator cover. Six-inch diameter, No. 26 gage, galvanized tubing will be installed
between the dry air outlet and moist air return openings on the machine and the appropriate fittings on the sheet metal flange. A dry
air dispenser of 6 inch diameter, No. 26 gage, galvanized tubing, fabricated in accordance with figure 57, will be attached to the
flange through the opening in the machine shop overhead. The horizontal section of the dry air dispenser will face fore and aft.
Nominal 6-inch-diameter flexible hose will be run from the moist air return fittings in the sheet metal flange down through the hatch to
the carpentry shop, as shown on figure 54. The lower end of the hose will be no more than 18 inches above carpentry shop deck.
Sensing elements will be installed in accordance with (f) below.
(b) Aft deckhouse dehumidification system. 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 58. The machine will be mounted on a
stand and protected with a cover, fabricated in accordance with figure 56. A portlight in the forward bulkhead of the aft deckhouse
will be opened. A No. 20 gage galvanized sheet metal flange or a -inch plywood blank will be fitted into the portlight opening. The
blank will contain two 4-inch-diameter holes with fittings for attachment of sheet metal ducts. One hole of sufficient size to receive a
humidistat cable, and one hole of sufficient size to receive the sensing element assembly. Four-inch-diameter, No. 26 gage,
galvanized sheet metal ducts will be installed between the dry air outlet and the moist air return opening on the dehumidification
machine and the fitted opening in the flange. Within the deckhouse, the dry air duct will extend to a point approximately 3 feet from
the aft bulkhead of the galley and approximately 3 feet from the aft bulkhead of the galley and approximately 6 feet above the deck.
The moist air return line will extend from the flange to a point approximately 2 feet above the deck. An electronic humidistat will be
installed within the deckhouse as specified in(e) below. A sensing element will be installed as specified in (f) below.
(c) Crane cab dehumidification system. A package dehumidifier, of the same type and capacity specified in (b), above
will be installed generally as shown on figure 55. The machine will be mounted on a stand and protected with a cover, fabricated in
accordance with figure 56. The bolted portable plate on the port side front of the crane cab will be removed and replaced with a -
inch thick exterior grade plywood or No. 20 gage galvanized sheet metal blank. The blank will contain holes and fittings for the 4-inch
dry air and moist air ducts, for the humidistat cable, and for the sensing element assembly. Four-inch-diameter, No. 26 gage,
galvanized sheet metal ducts will be installed from the dry air and moist air connection of the dehumidification machine to the
openings in the blank. The dry air duct will extend to the after starboard corner of the cab and terminate approximately 3 feet from
the bulkhead. The moist air return duct will terminate at the blank. Humidistat installation will be in accordance with (e) below.
Sensing element will be installed as specified in (f) below.
(d) Duct connections. Connection of air ducts to the dehumidification machines will be made by unions or slip joint
connections, which permit easy removal of the machines for servicing.
(e) Humidistat installation . Hair-type electronic humidistats will be set to maintain a 40 percent relative humidity, plus or
minus 5 percent, within the dehumidified areas. The humidistats will be installed at a height of approximately 3 feet above deck and
at a distance of approximately 3
Change 2 P-2
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