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 TB 740-97-4
(c) Cab openings. The opening caused by the removal of the fabric canopy top and back sections will be covered
with No. 20 gauge galvanized sheet metal cover for top of windshield assembly (hull numbers below 732) and for back section of all
hull numbers. Covers shall be flanged and secured with sheet metal screws using existing fastenings where feasible. Reposition the
existing windshield assembly top cross members to eliminate interference and provide stiffeners to support cover blanks. Install a
readily removable access panel approximately twenty-four (24) inches in the back cover of the operator's cab. Panel shall be
designed for sealing by means of tape and strippable compound. All dimensions for covers shall be taken from LARC V applicable
series. Install galvanized sheet metal or plywood panels over operator's cab windows to fit window frame. All joints will be sealed
with strippable compound and bituminous coating. Drain openings at rear of cab including air and fuel vents on bulkhead aft of cab,
and vent in strong back will be masked and sealed with strippable compound and bituminous coating.
(d) Dehumidification piping system . The points of entry of all air ducts into compartments and the connecting joints
of all air ducts 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.
(4) Installation of dehumidification system . Normally a dynamic dehumidification system will be installed for each group
of four lighters. Installation of the dynamic dehumidification system will be generally as shown in figures 33, 34, or 35. When
dehumidification of the lighters is accomplished on an individual basis, installation of the dynamic dehumidification system will be in
accordance with this bulletin.
(a) Dehumidification machine . A package dehumidifier, single desiccant bed, absorbent type, 10,000 cubic feet
capacity, 110 volt, alternating current, will be installed as shown on figures 33, 34 or 35. The machine will be mounted on a stand
and protected with a cover fabricated generally in accordance with figure 36.
1. The machine will be installed on the engine hatch cover (for light rs stored as shown in figures 33 and
e
34) in a manner to require a minimum of turns in the ductwork and will be secured in place to prevent movement.
2. Lighters stored stern to stern as shown in figure 35 the machine will be mounted on a stand at lighter's
stern and the stand will be secured in place with existing bolts in a position to provide the most direct connection for ducting to the
hull access openings. The machine stand will be fabricated as shown in figure 37. The machine will be protected with a cover
fabricated in accordance with figure 36.
(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 gauge galvanized tubing, with necessary ells, reducing fittings and
connections will be installed as shown on figures 33, 34 and 35. Flanges of galvanized metal will be joined to the ductwork to attach
it to openings in the blanks prepared for its entrance into the lighter. The flanges will be constructed with collars or suitable tabs to
resist dislodgment from the blank openings. Ductwork will be supported as necessary by use of wooden or metal A-frames or other
structures.
(d) Humidistat. A hair type humidistat will be set to maintain a 40 percent relative humidity, plus or minus 5
percent, within the dehumidified areas. The humidistat will be installed approximately three feet above the floor plate level in the
compartment of the lighter from which the moist is ducted back to the humidifier. A bracket will be provided to retain the humidistat.
The humidistat will be wired to the dehumidifier with No. 18, two-conductor, rubber covered cable. The cable will follow moist air
return ducting to support and shall penetrate the hull through the blank as shown in figure 33 and 34 and at the adapter fitting as
shown in figure 35.
(e) Humidity sensing elements . Humidity sensing elements will be installed in the blanks for lighters stored as
shown on figure 33 and 34. Lighters stored stern to stern as shown in figure 35, fabricate adapter plate and install humidity sensing
elements in one (1) hydraulic bilge pump overboard discharge hull fitting of each lighter. Mount the sensing element on the most
accessible fitting near the moist air outlet of each hull as shown in figure 35. Remove hose from bilge pump overboard pipe to
provide opening in hull.
c. Preparation of Rubber Tires for Storage.
(1) Blocking lighters during storage. Lighters will not require blocking during storage. Pneumatic tires will be inflated to
30 lbs. per sq. inch.
(2) Protection of tires during storage.
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