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 TB 55-1900-201-45/1
b. Where extensive work is required on both sides of the vessel, it is better practice to have the welding progress
simultaneously on both sides rather than to complete one side before starting the other.
c. In general the order of welding should be such as to allow the maximum freedom for contraction of the weld-
ment. For example, it would be poor procedure to fix both shorter edges of a plate before welding the longer edges.
d. Temperature is an Important factor in welding. Where weld- ing is done at temperatures appreciably below
freezing, pre-heat and/or shelter should be provided to reduce the rate of chilling. More caution in this regard is neces-
sary when welding on thick plating than on thinner plating.
For ordinary thicknesses and temperatures not far below freezing, work within a ship or on a ship's bottom within a grav-
ing dock may usually be considered as sufficiently sheltered.
E-34.
Procedure.
a. Besides proper shipfitting and edge preparation, there should be careful alignment of the structure. Local eccen-
tricity in butts of intercostal longitudinal beams, girders, and bulkheads attached to strength deck and shell is conducive
to service cracking. The webs of such members should be carefully aligned on both sides of the interrupting (transverse)
structure before welding, and changes of girder depth and flanges occurring at the interrupting section
should be provided with transition fairing.
b. Tack welds which are used to position the weldment in the fit-up should be chipped out before making the final
weld. Frequently, they have been overstressed and may contain sub-surface cracks. The welding machines employed
should be adequate for the job, in good condition and operated at the correct setting for the work at hand. Butt welds,
except in very thin plates, call for back- chipping with a round-nosed tool or by means of flame-gouging in order in insure
complete penetration. The use of a backing strip, flux back-up, etc., are satisfactory alternatives.
E-23
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