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 TB 740-97-4
sion of the hatch opening. The timbers will be spaced at approximately equal intervals over the hatch opening. The ends of the
timbers will extend approximately 6 inches beyond the hatch coaming and will be notched to a depth of inch, plus or minus 1/8
inch, at lines of intersection with the coaming. The four sides of the cargo hatches will be blanked with exterior grade plywood or
galvanized sheet metal. The blanks will be sealed with strippable coating and bituminous coating. The strippable coating and
bituminous coating will extend to assure watertight seal between blanks, the hatch tops and lower coamings, and around the
protruding ends of the 4-x4-inch timbers.
(c)
Stack. The covers under the stack hood will be secured in closed position and sealed with strippable coating and
bituminous coating.
(d)
Exhaust lines and vent lines. The engine exhaust lines and the vent line located in the stock will be closed with
caps, plugs, blanks or pressure sensitive tape, and sealed with strippable coating and bituminous coating.
(e)
Vents, fills, and overflow lines. All vent, fill, and overflow lines opening into the dehumidified area will be closed with
caps, plugs, blank or pressure-sensitive tape, and sealed with strippable coating and bituminous coating.
(f) Doors, hatches and manholes. All exterior doors, hatches, manholes leading into a dehumidified zone, except those
used for introduction of dehumidification piping, and the one exterior door used for inspection purposes, will be closed and sealed
with tape. The exterior port or starboard door used for monthly inspection of refrigerator compartments will be left unsealed and
marked accordingly. Where hatch or manhole cover fits over a raised coaming, bituminous coating will be troweled into the aperture
between the closed cover and the coaming. Flush-type doors and covers will be sealed with strippable coating and bituminous
coating. Recesses in covers for opening devices will be masked with pressure sensitive tape and coated with strippable coating.
(g) Dehumidification piping system. The connecting points to 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 will be similarly sealed.
(4) Dehumidification Installation.
(a)
Dehumidification systems, zone 1. A package dehumidifier, single desiccant bed, absorbent type, 10,000 cubic foot
capacity, 110-volt, alternating-current, will be installed, generally, as shown in figure 51. The machine will be mounted on a stand
and protected with a cover, fabricated in accordance with figure 52. One machine will service the port and starboard engineroom and
stack. The machine will be installed on the barge deck adjacent to the port or starboard engine access hatch, as shown in figure 51.
An extension, terminating in a 90elbow, 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.
1. Duct installation No. 1. One engineroom access hatch cover shall be removed and stowed in the engineroom. A
galvanized sheet metal or -inch exterior grade plywood blank will be installed over the hatch opening. The blank will be sealed with
strippable coating and bituminous coating. Holes of sufficient size will be provided to introduce the air ducts, humidistat cable, and
sensing elements. The air from the dehumidification machine will enter one side of the engineroom bulkhead and will be removed
from the opposite side. Connect one length of flexible 4-inch hose, conforming to MIL-H-8796, to the moist-air return connection at
the machine to remove the moist air from the lower extremities of the engineroom.
2. Air duct installation and machine connections. Four-inch, No. 26 gage, galvanized tubing, with necessary cells,
tees, reducing fittings, supports, and connections, will be installed. Ducts will run with a minimum of bends, as shown in figure 51.
Connections of the duct to the dehumidification machine will be made with unions or slip joint connections, which permit easy
removal of the machine for servicing.
3. Humidistat. A hair-type humidistat is set to maintain a 40-percent relative, humidity, plus or minus 5 percent, within
the enginerooms and may be installed in either the port or starboard engineroom. The humidistat will be located approximately 3 feet
above the floor plate and secured to the centerline bulkhead. The humidistat will be connected to the dehumidification machine by a
No. 18, two-conductor, rubber covered cable with suitable connectors.
4. Sensing elements. Two sensing elements with cable will be installed, one in each engineroom, as shown in figure
51.
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