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 TB 55-1900-201-45/1
plans, in the form of strapping fitted to increase the hull girder strength and stiffness. Where so used the plating to which
they are attached should be in good condition to insure efficient attach- ment, by fillet welding along the edges. Plug
welding, in the body of the doubler, can be used. The corners of the doubler should be tapered and well rounded.
c. Doublers may be accepted in non-strength areas where their purpose is essentially to restore watertight integrity
and local strength. Such areas include:
(1) Deck plating well inboard between cargo hatches.
(2) House tops and superstructure decks except the first
deck above the main deck in vessels with long superstructures.
(3) Forecastle decks and poop decks limited to approximately the forward or after one-tenth length of the vessel.
(4) Platform decks.
d. Even in these locations, doublers should not be permitted where special local strength is required. For example,
the plating forming the house top of a small deck house is not involved in basic hull strength. Repair by doubler would be
perfectly acceptable if the deck house served as a bosn's locker or the plenum of a ventilation system. However, if the
house top plating tied together the framing intended to fix the position of a mast or kingpost, a doubler patch would not
be permissible. Another example in the same category is the superstructure deck plating in way of a lifeboat installation.
e. When a doubler is deemed appropriate and is installed over a crack, the ends of the crack should be drilled and,
if possible, the crack should be veed and welded.
f. On vessels without double bottoms operating on protected waters or in other similar circumstances on such ves-
sels, doublers may be accepted for repairs in way of engine or boiler rooms where it would be necessary to remove
heavy equipment, etc. in order to provide access for plating replacement. However, in such cases, care should be taken
that existing plating has enough thickness for efficient attachment.
g. Doublers on tank vessels in way of cargo or fuel tanks are a special problem. The interface between a doubler
and the plate beneath can constitute a gas pocket which is hazardous and completely inaccessible to gas-freeing proce-
dures. Doublers should not be permitted in such locations except as detailed on approved plans.
h. Plan approval is usually not necessary for installations made in accordance with paragraphs (c) and (d) above.
However, a record of each installation, including its size and location, should be maintained in the vessel's inspection file.
E-19
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