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 TB 740-97-4
holes in each cab will be blanked in order to permit installation of a sensing element.
(b) Engine room.
1. Access hatch. The access hatch to the engine room will be sealed by troweling bituminous
coating into the aperture between the coaming and closed cover.
2. Ventilator trunk openings. The openings not used for dehumidification system ducts (Figures 5
and 6) will be plugged or capped from the outside, using 1/4-inch exterior grade plywood or No. 20 gage galvanized
sheet metal, and sealed with strippable coating and bituminous coating. The timber holes in the cowl vent box will be
sealed with strippable coating and bituminous coating.
bituminous coating.
4. Hull penetrations. All openings in the hull that lead to the engine room, except the raw water
intake pipe in the keel cooler recess, will be closed with fitted wood plugs, then sealed with strippable coating and
bituminous coating.
(c) Seal7l,g of Dehumidification piping system,. The connecting points of all air tubing or ducts to areas
to be 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 tubing or ducts. All Joints in the tubing or
ducts will be similarly sealed.
(d) Ramp gasket. The area between the free edge of the gasket and the hull will be coated with
strippable coating.
(e) Ramp hinges. The exposed rubber surfaces of the hinges will be coated with strippable coating.
(f) Propellers and shafts. Using strippable coating a seal will be applied around the propeller shaft at
the stern tube, at both ends of the strut bearing, at the propeller, an over the propeller shaft nut. The stern tube sea
water scoops will be sealed with the same coating.
(g) Deleted.
(4) Dehumidification installation.
cubic feet capacity, 110-volt alternating current, will be installed as shown on figure 5 or 6. The machine will be mounted
on a stand and protected with a cover fabricated in accordance with figure 7.
(b) Machine connections. Connections of ducts to the dehumidification machine will be made of unions
or slip Joint connections which permit easy removal of the machine for servicing.
(c) Duct Installation. Four-inch diameter,
No. 26 gage, galvanized tubing, with necessary ells, reducing fittings and connections, will be installed generally as
shown on figure 5 or 6. Flanges of galvanized metal or /2-inch thick exterior grade plywood will be Joined to the
ductwork to attach it to the vent trunk openings. A hole in the flange for the passage of the humidistat cable will be
provided in accordance with figure 5 or 6. The flanges will be constructed with collars or suitable tabs to resist
dislodgment from the vent trunks.
(d) Ductwork support. Ductwork run on deck will be supported on metal or wood stanchions. The ducts
will be fastened to the stanchions by galvanized strapping secured to the stanchions.
(e) Humidistat. A hair type humidistat will be set to maintain a 40 percent relative humidity, plus or
minus 5 percent, within the dehumidified area. The humidistat will be installed in the engine room of the landing craft
remotely serviced by the dehumidification machine as shown in figure 5 or 6. The humidistat will be secured
approximately 3 feet above the floor plate level. The humidistat will be wired to the dehumidification machine by means
of No. 18, two-conductor, rubber covered cable, passing through the vent trunk opening. The cable will be secured to
prevent any movement of the cable with respect to the flange over the opening.
(f) Humidity sensing elements. Humidity
sensing elements will be installed as follows:
1. Engine room. A humidity sensing element with cable will be installed in each engine room. The
sensing element contact will be mounted in the side of the duct, just above the connection to the vent trunk opening. The
sensing element and cable will be run down the inside of the duct and will be supported in such a manner that they are
secured against motion and contact with metal or other conductive surfaces.
2. Cab. A humidity sensing element without cable will be installed in the cab of each vessel. The
sensing element will be mounted in the opening provided in the blanked peephole of each cab.
B-2 Change 2
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