f fact an oil-temperature curve plotted from periodical readings
taken over a continuous run of considerable length usually reaches a
maximum early, afterward falling to a temperature about which the
fluctuations are only slight during the remainder of the run. Fig. 64
illustrates an oil-temperature curve plotted from readings taken over a
period of twenty-four hours. In this case the oil system was of the
gravity description, the capacity of the turbine being about 6000
kilowatts. The bearings were of the ordinary white-metal spherical type.
Over extended runs of hundreds and even thousands of hours, the above
deductions may be scarcely applicable. Running without break for so
long, a small turbine circulating its own lubricant would possibly
require a renewal of the oil before the run was completed, in the main
owing to excessive temperature rise and consequent deterioration of the
quality of the oil. Under these conditions the probabilities are that
several temperature fluctuations might occur before the final maximum,
and more or less constant, temperature was reached. In this connection,
however, the results obtained are to a very large extent determined by
the general mechanical design and construction of the oiling system and
turbine. A reference to Fig. 63 again reveals at once a weakness in that
design, namely, the unnecessarily close proximity in which the oil and
water tanks are placed.

[Illustration: FIG. 65]

A design of thermometer cup suitable for oil thermometers is given in
Fig. 65 in which A is an end view of the turbine bedplate, B is a
turbine bearing and C and D are the inlet and outlet pipes,
respectively. The thermometer fittings, which are placed as near the
bearing as is practicable, are made in the form of an angular tee
fitting, the oil pipes being screwed into its ends. The construction of
the oil cup and tee piece is shown in the detail at the left where A is
the steel tee piece, into which is screwed the brass thermometer cup B.
The hollow bottom portion of this cup is less than 1/16 of an inch in
thickness. The top portion of the bored hole is enlarged as shown, and
into this, around the thermometer, is placed a non-conducting material.
The cup itself is generally filled with a thin oil of good conductance.

Allied to the oil system of a turbine plant is the water service, of
comparatively little importance in connection with single self-contained
units of small capacity, where the enti