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Breaking up the Job.—The job can mostly be broken up into a
number of well-defined and easily recognizable units, each of which can
have a separate section in the data record. These units will be further sub-
divided, and under each subdivision will be indicated the job identification
number and the important dimensions. The material to be used should
be entered, the thickness, the working pressure for which the part is designed,
the test pressure, the stress per square inch at working load, &c. It is a
good plan to mark in the data-book, at the head of each section, the charac-
teristic formulae applied, and also the safe working load.
Data-books.—It is usual to keep a list of significant dimensions and
arrangements, because frequently the thing wanted most rapidly from the
design office is the arrangement of an installation, and the accommodation
which will be necessary to house it. At the head of such a section should
be a list of normal clearances. A specimen page of such a section is given
herewith for a marine engine and boiler installation, which will fully explain
NORMAL CLEARANCE. ENGINE ROOM
A = distance between H.P. and L.P. centres.
B = distance between M.P.j and M.P.2 centres.
C = distance between M.P.2 and L.P. centres.
D = distance to outside of H.P. casing + 3 ft.
E = distance to outside of M.P.j casing + i ft. 9 in.
F = distance from C.L. of cylinders to C.L. of shaft.
G = distance from C.L. of shaft to tank top + 2| in.
H = A + distance to H.P. casing + distance to L.P. joint + i ft. 9 in.
J = 2 distance from C.L. to column foot + 2 ft.
Size of Cylrs.
Fig. 3.—Specimen Page of Data-book (i)
N.B.—Sketch, table, and column all form page of Data-book in each case.