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Full text of "Modern Mechanical Engineering Vol-I"

FITTING AND  ERECTING

255

bottom half-bearings, say -gV in,, by means of the bottom pads, previously
described; this is a wise precaution to prevent damage to the brass labyrinth
packing strips which line the H.P. and L.P. glands, diaphragm collars, &c.,
to prevent leakage of steam out, or air in. Some oil should be poured over
the shaft journals and into the bottom half-bearings; the shaft should then
be carefully lowered till resting in the bearings, special care being taken
during this lowering operation that the wheels are clear of the fixed diaphragms
between them. The thrust block bottom half should then be put in position
and wedged up temporarily with wooden wedges, to prevent any axial move-

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Fig. 10.—Top Half of Turbine Cylinder turned over for fitting of Top-half Diaphragms, Glands, and Nozzles
ment. The shaft and wheels are then slowly revolved by hand, or if neces-
sary by means of the crane pulling on a rope previously wrapped round the
shaft. If the brass labyrinth strips are touching the shaft, they will mark
the shaft with a fine yellow line. Before lifting the shaft to scrape the laby-
rinth strips, it is advisable to fix the vertical guide-strips in position to prevent
the wheels fouling the diaphragms, and the shaft is then raised and the brass
labyrinth strips scraped and sharpened up again where the shaft has rubbed
them flat. The shaft is then lowered again into its final central position by
previously removing the ^V in. of liners added to the bottom pad under the
bearings.
In order to put the half-diaphragms in the top half-cylinder, the latter is
turned upside down and the diaphragms then put in position and secured by
" keeps " held in by screws. Before the diaphragms are put in position,