of suitable size. In view of the fact
that a turbine by-pass valve opens only when the unit is required to
develop overload, or the vacuum fails, a good feature of this governing
mechanism is that the valve referred to can be kept constantly in
motion, thereby preventing sticking in an emergency, even though it be
actually called into action only at long intervals. Another feature of
importance is that the oil supply to the bearings, as well as that to
the governor, can be interconnected so that the governor will
automatically shut off the steam if the oil supply fails and endangers
the bearings. This mechanism is also so proportioned that, while
responding quickly to variations in load, its sensitiveness is kept
within such bounds as to secure the best results in the parallel
operation of alternators. The governor can be adjusted for speed while
the turbine is in operation, thereby facilitating the synchronizing of
alternators and dividing the load as may be desired.

In order to provide for any possible accidental derangement of the main
governing mechanism, an entirely separate safety or over-speed governor
is furnished. This governor is driven directly by the turbine shaft
without the intervention of gearing, and is so arranged and adjusted
that, if the turbine should reach a predetermined speed above that for
which the main governor is set, the safety governor will come into
action and trip a valve which entirely shuts off the steam supply,
bringing the turbine to a stop.

Lubrication

Lubrication of the four bearings, which are of the self-adjusting, ball
and socket pattern, is effected by supplying an abundance of oil to the
middle of each bearing and allowing it to flow out at the ends. The oil
is passed through a tubular cooler, having water circulation, and pumped
back to the bearings. Fig. 33 shows the entire arrangement graphically
and much more clearly than can be explained in words. The oil is
circulated by a pump directly operated from the turbine, except where
the power-house is provided with a central oiling system. Particular
stress is laid by the builders upon the fact that it is not necessary to
supply the bearings with oil under pressure, but only at a head
sufficient to enable it to run to and through the bearings; this head
never exceeding a few feet. With each turbine is installed a separate
direct-acting steam pump for circulating oil for starting up. This will
be referred to again under t