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 TB 740-97-4
APPENDIX U
DYNAMIC DEHUMIDIFICATION INSTRUCTIONS FOR
TUG, OCEAN GOING, DIESEL, 1530-HORSEPOWER,
STEEL, 143-FOOT, DESIGN 377A
1.
General. This appendix provides detailed instructions for preparation of tug, design 377A, for dynamic dehumidification.
2.
Preparation Instructions. a. Disassembly and Stowage.
(1) Pilothouse. The following Items will be removed, identified and stowed in the pilothouse:
(a) Pelorus stand.
(b) Blinker light and key.
(c) Rudder anchor directory.
(d) Jackstaff and anchor light staff.
(e) Ship's bell and bracket.
(f) Windshield wipers.
(g) Navigation lights.
(h) Searchlights.
(i) Halyards.
(j) Horn, air whistle and lanyard.
(k) Main deck fire station valves and fittings.
(l) Skylight glass - blank white sheet metal.
(2) Crew Quarters. The following items will be removed, identified, and stowed in the crew quarters:
(a) All canvas covers, curtains and dodgers.
(b) Lifeboat falls and equipment.
(d) Fire monitors and valves.
(e) Salvage hose.
(f) Grating from aft and main deck.
(3) Lifeboat. The lifeboat and/or float-away life raft will be stowed on the boat deck. The lifeboat will be inverted and
stowed on supports of sufficient height to hold the boat clear of the deck. The supports will be distributed to minimize stresses on the
boat. The grips will be used to hold the lifeboat in position.
b. Methods of dynamic dehumidification. Outlined below are two methods of preparing the ocean going tug, design 377/377A,
for dynamic dehumidification. Either method is acceptable.
(1) Method A. Method A utilizes a rotary desiccant electric dehumidifier, solid wheel type 20-153, 150,000 cubic foot
capacity, 440-volt, three phase 60-cycle alternating-current and uses the fire main (as the carrier) for transferring the dry air
throughout the vessel. This single machine will dehumidify the entire tug, including the windlass and towing motor. There are
approximately 67,000 cubic feet of space within the tug to dehumidify.
(2) Method B. Method B utilizes a total of seven to eight package type dehumidifiers, single desiccant bed, 10,000 cubic
feet capacity to dehumidify the tug. Under this method, the vessel is dehumidified by zones, consisting of specific areas of the
vessel. Like Method A, all areas of the tug, including the anchor windlass and towing motor, are under dehumidification.
c. Preparation for dehumidification for Method A.
(1) Dehumidified areas. The entire interior of the tug will be prepared for dehumidification.
(2) Provision for air circulation . To permit maximum circulation of air within the dehumidified zone, all interior doors,
including the door from the engineroom to the shaft alley, cabinet doors, controller doors, refrigeration doors, doors on similar items
will be secured in open position. All manhole covers will be removed and secured in other than normal position.
NOTE
Manhole covers and scuttles will be covered with 1 -inch perforated mesh wire to prevent injury during inspection.
The engine escape hatch and the hatch between the stores compartment and shaft alley will be secured in n open position.
a
Valves in the bilge suction line from the tank, voids and compartments and the bilge manifold valves will be opened. Ventilation
systems will be in an open position. Piping will be disconnected at the air storing tank and at the air valves. All air valves will be left
in open position.
Change 2
U-1
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