may be deemed quite safe to lock the thrust-block in
its position, by screwing the screws G up lightly, and then to turn on
steam and begin running slowly.

Next, the spindle may be very carefully and gradually worked in the
required direction, namely, in that direction which will tend to bring
the dummy rings and groove walls into contact, until actual but very
light contact takes place. The slightest noise made by the rubbing parts
inside the turbine can be detected by placing one end of a metal rod
onto the casing in vicinity of the dummy pistons, and letting the other
end press hard against the ear. Contact between the dummy rings and
spindle being thus demonstrated, the spindle must be moved back by the
screws, but only by the slightest amount possible. The merest fraction
of a turn is enough to break the contact, which is all that is required.
In performing this operation it is important, during the axial movements
of the spindle, to adjust the halves of the thrust-block so that there
can exist no possible play which would leave the spindle free to move
axially and probably vibrate badly.

After ascertaining the condition of the dummy rings, attention might
next be turned to the thrust-block, which must not on any account be
tightened up too much. It is sufficient to say that the actual
requirements are such as will enable a very thin film of oil to
circulate between each wall of the spindle thrust-grooves and the brass
thrust-blocks ring. In other words, there should be no actual pressure,
irrespective of that exerted by the spindle when running, upon the
thrust-block rings, due to the separate halves having been nipped too
tightly. The results upon a test of considerable friction between the
spindle and thrust-rings are obvious.

The considerations outlined regarding balancing pistons and dummy rings
can be dispensed with in connection with impulse turbines of the De
Laval and Rateau types, and also with double-flow turbines of a type
which does not possess any dummies. The same general considerations
respecting blade conditions and thrust-blocks are applicable, especially
to the latter type. With pure so-called impulse turbines, where the
blade clearances are comparatively large, the preliminary blade
inspection should be devoted to the mechanical condition of the blade
edges and passages. As the steam velocities of these types are usually
higher, the importance of minimizing the skin friction and eliminating