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 TB 55-1900-201-45/1
generally in line with the procedures and methods set forth in Section IV of these notes.
E-7. If the vessel is in class, and/or is assigned a load line, the nature and extent of the repairs as determined by the
classification society surveyor is to be given full consideration. However, if there is a difference of opinion as to what
should be required, the inspector cannot discharge his responsibility by deferring to anyone else's judgment. In such
cases, he should refer the matter to his superior officer for assistance and/or decision before the final requirements are
written. A working liaison between the Officer in Charge, Marine Inspection and the local representative of the classifica-
tion society will generally serve to iron out such difficulties. The repair measures set forth in Section IV of these notes
are to be considered as general principles rather than specific "rules" to be rigidly enforced in all cases. They should be
employed as a guide taking into account the interests of the ship owner while, at the same time, fulfilling the Coast
Guard's statutory responsibility with respect to seaworthiness and safety of life.
SECTION III. Notes on Inspection
E-8. Deterioration:
Deterioration of the metal structure is probably the most common, single defect in steel vessels. It can be due to
a number of different causes or combinations thereof including age, inadequate maintenance, working of the hull struc-
ture, chemical or erosive action of the cargoes carried, electrolysis, local Wear, some improper feature of design, etc. In
some cases, such as deep pitting and external grooving, deterioration is easy to detect. In other cases, such as the gen-
eral erosion of age or incipient joint or member failure, it is impossible to ascertain the deterioration without actually
gaging or very careful examination. In any case judgment is required to evaluate and determine
and to what extent
repair is necessary.
E-9. Gaging:
a. The only practical way of determining the degree of deterioration is to measure the thickness of the member
in question and compare it with the original thickness. This comparison is usually expressed in terms of percentage of
wastage from the original scantling. Since this determination usually requires drilling of the hull or other expensive
preparation, it should not, in general, be undertaken unless there is a reasonable basis for doubt as to the present scant-
lings.
b. Thickness measurements can be made by drilling and gaging or by ultrasonic measurement. In the following
remarks, the term "gaging" is meant to include both methods of measurement; drilling
E-3
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