aken out of the steam in any one set of nozzles. The idea
is to keep the velocity of the steam in each stage as nearly constant as
possible. The nozzles in the diaphragms and the intermediates do not,
except in the lowest stage, take up the entire circumference, but are
proportioned to the progressive expansion of steam as it descends toward
the condenser.

Clearance

While the machine is running it is imperative that there be no rubbing
contact between the revolving and stationary parts, and this is provided
for by the clearance between the rows of moving buckets and the
intermediates. Into each stage of the machine a 2-inch pipe hole is
drilled and tapped. Sometimes this opening is made directly opposite a
row of moving buckets as in Fig. 10, and sometimes it is made opposite
the intermediate. When opposite a row of buckets, it will allow one to
see the amount of clearance between the buckets and the intermediates,
and between the buckets and the nozzles. When drilled opposite the
intermediates, the clearance is shown top and bottom between the buckets
and intermediates. (See Fig. 11.) This clearance is not the same in all
stages, but is greatest in the fourth stage and least in the first. The
clearances in each stage are nearly as follows: First stage, 0.060 to
0.080; second stage, 0.080 to 0.100; third stage, 0.080 to 0.100; fourth
stage, 0.080 to 0.200. These clearances are measured by what are called
clearance gages, which are simply taper slips of steel about 1/2-inch
wide accurately ground and graduated, like a jeweler's ring gage, by
marks about 1/2-inch apart; the difference in thickness of the gage is
one-thousandth of an inch from one mark to the next.

[Illustration: FIG. 10]

[Illustration: FIG. 11]

To determine whether the clearance is right, one of the 2-inch plugs is
taken out and some marking material, such as red lead or anything that
would be used on a surface plate or bearing to mark the high spots is
rubbed on the taper gage, and it is pushed into the gap between the
buckets and intermediates as far as it will go, and then pulled out, the
marking on the gage showing just how far in it went, and the nearest
mark giving in thousandths of an inch the clearance. This is noted, the
marking spread again, and the gage tried on the other side, the
difference on the gage showing whether the wheel is high or low.
Whichever may be the case the hight is corrected by the step-bearing
screw. The wheels