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 TB 740-97-4
APPENDIX E
DYNAMIC DEHUMIDIFICATION INSTRUCTIONS FOR
TUG, HARBOR, DIESEL, 200 HP, STEEL,
45 FOOT, DESIGN 320
1. General. This appendix provides detailed instructions for preparation of the harbor tug, design 320, for dynamic
dehumidification.
2. Preparation Instructions. a. Disassembly and Stowage.
(1) Pilothouse. The following items will be removed, identified and stored in the pilothouse:
(a) Windshield wiper.
(b) Life raft.
(c) Life ring.
(d) Horn.
(e) All exterior lights with plug-type connections.
(f) Bell.
(2) Crew quarters. The following items will be removed, identified, and stowed in the crew quarters:
(a) Canvas covers.
(b) Anchor windlass and handle.
(c) Fire hose and nozzle.
(d) Portable davit and falls.
(e) Halyards.
(f) Vent cowls.
(g) Port light screens.
(h) All deck keys and dog wrenches.
(3) Rope locker. The anchor rope will be detached from the anchor and stowed in the rope locker.
b. Preparation for Dynamic Dehumidification.
(1)
Dehumidified area. The entire tug will be prepared for dehumidification. The mid-ship section, including
the engine room, pilothouse, and crew quarters, will be prepared for dynamic dehumidification. The lazaret and forepeak
compartments will be preserved by a combination of static and dynamic dehumidification. Dry air will enter these
compartments through the open sluice valves and in addition, sufficient bagged desiccant, conforming to MIL Spec D-
3464, to maintain relative humidity of 40 percent will be secured in each compartment.
(2)
Provisions for air circulation. The door between the engine room and the crew quarters will be secured in
open position. The hatch cover will be removed from the hatch in the pilothouse seat. All dampers in the ventilation
system will be turned to open position. The valves leading from the forepeak area and the lazaret will be turned to open
position.
(3)
Sealing for dehumidification. Methods and materials used in sealing for dehumidification will be in
accordance with this bulletin. Detailed sealing requirements are as follows:
(a) Dehumidified area. Edges of doors, portlights, windows, hatch covers and all other openings in the nature
of seams or joints between closely opposed surfaces which give access to dehumidified areas will be sealed with
strippable coating and bituminous coating. When sealing portlights, the strippable coating will be extended outward over
adjacent surfaces of the bulkheads.
(b) Stack. All openings to the stack will be masked with pressure-sensitive tape and sealed with strippable
coating and bituminous coating.
(c) Air supply openings. The supply openings for the mechanical ventilation system, which is located on the
aft bulkhead of the house, will be sealed as specified for stack openings.
(d) Exterior valves, vents, fills and discharges. All vents, fill and discharge openings located on decks, will be
sealed with strippable coating and bituminous coating. If necessary to attain the required air tightness, all exterior valves
will be masked with pressure-sensitive tape and sealed with strippable coating and bituminous coating.
(e) Hull openings. All exterior hull openings leading to dehumidified areas of the vessel will be closed with
caps, plugs, blanks or pressure sensitive tape and sealed with strippable coating and bituminous coating.
(f) Hatches. The perimeters of the hatches over the engine room and crew quarters will be sealed by
troweling bituminous coating into the aperture between the coaming and the closed cover. Recesses in the covers will be
masked with pressure-sensitive tape. The tape and all joints around the operating mechanism and dogs will be
Change 2 E-1
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