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 TB 55-1900-201-45/1
g. Longitudinal and Transverse Bulkheads. Cargo hold bulkheads are usually not troubled by excessive corrosion
except along the lower boundaries and in way of bilge wells. In the case of the longitudinal and transverse bulkheads in a
tankship, especially where light pro- ducts have been carried, corrosion is to be expected. Wastage up to 35 percent
may be accepted provided there is no evidence of deformation when subjected to a hydrostatic test. The top strake of
the bulkhead plating in a tankship is usually made heavier in anticipation of the increased corrosion to be expected in this
area which is usually wet but not submerged. Therefore, when referred to the original scantling, an increased allowance
for deterioration may be permitted. Applying a 35 percent wastage to the original scantling of the next to topmost strake
will serve to establish the minimum thickness acceptable in the topmost strake.
h. Frames, Beams and Stiffeners. Generally, the flanges and portions of the webs next to the flanges are more
highly stressed, more subject to mechanical damage, and corrode faster than the balance of the member.
SECTION III. Fractures
2-3. Types of Fractures.
a. Fractures in hull plates, etc., usually start in localized, high stressed areas. In the preliminary inspection, the
first thing to be determined is whether or not the fracture started in a notch or sharp angle, and if it did, to eliminate this
feature.
b. When major fractures occur and where considerable material is to be removed and new plates, frames, etc.,
are to be inserted, the repair may involve less favorable welding conditions than for new construction. The type of repair
to be made and welding procedure to be used should be carefully evaluated.
c. Cracks in the deck or in the bottom within about the amid- ships half length and which originate in structural
interruptions will frequently require the fitting of a suitable repair insert in order to minimize weld restraint in the local area
of stress concentration. Cracks which have opened too far or are too irregular to permit satisfactory weld preparation, or
which are located so that access is in- sufficient for producing sound, full penetration welds, also call for the fitting of in-
serts. Evidence of deterioration or poor quality of the fractured plate are additional reasons for plate replacement.
d. Localized bands of accelerated corrosion should ordinarily be taken as evidence of such deterioration and the
affected portion of plating replaced. Where none of the foregoing conditions exist, the crack may be repaired by welding
without replacement of plating.
e. Special care should be taken in the repair of surface cracks. Care should be taken that the defect is com-
pletely removed by grinding or other suitable means. The use of nondestructive test (NDT) method such as magnetic
particle may be useful in detecting any remaining subsurface defect.
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