The Horizontal Steam Turbine For Stationary Plants 1920
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Fig. 11. “Broken
down" oil
One source of water accumulation in the
oil is the steam leakage of the giand packing
(A3, Fig. 4). The steam blows past the
packings into the housings of the main bear-
ings (F2) and condenses.
Water may also leak into the oil from the
water cooling coils in the oil cooler (T6), or
from the water jackets (K)
in the housings of the main
bearings.
Where leakage of water
into the oil system cannot be
avoided, a water trap (Ti 1),
fitted in a vertical position,
to the bottom of the oil tank,
has been found of great ser-
vice. The water, circulating
with the oil, will separate
and drain into the trap. Once
there, it cannot mix with
the oil again. This water
trap should be drained every
twenty-four hours, letting
the water and sludge run
until clear oil appears.
The drain cocks on the oil
tanks should be opened be-
fore starting up the turbine,
and at least once every
twenty-four hours to remove
water and impurities.
The suction of the oil
pump should be from 2 to 4
inches above the bottom of
the oil tanks, as otherwise
any separated water will be
taken up by the pump,
the oil, and passed into the
the unfavorable influence of
water upon the oil, it is well to remove each
clay, from the bottom of the oil tank., 3 to 6
gallons of oil for treatment in a steam-heated
separating tank and later in a good filter.
The purified oil should be returned to the
circulating system at the same time that a
corresponding quantity is drawn off for treat-
ment. In this way the vitality of the oil
can be maintained at a high standard.
If the oil capacity of the system is small,
it is particularly desirable to follow this
treatment.
It is good practice to have a large quantity
of oil in circulation, with large oil tanks in
churned with
oil system.
of
which the oil has time to rest and separate
from the air, water, dirt and other impurities
it collects in the system.
Broken Down Oil
The length of service of an oil is dependent
upon the quality of the oil. An unsuitable
oil breaks down quickly and “goes to pieces”
badly. The correct high-grade oil, under
normal conditions, will give good service for
10,000 working hours at least; and under
severe- and very unfavorable working condi-
tions, for 3,000 working hours at most.
Fig. 11 is a photograph of an actual
sample of broken down oil. The original oil
has separated -into three distinet bodies.
At the top is clear oil; at the bottom is
clear or somewhat cloudy water; between
the two is a slimy mixture, a large portion of
which is water intimately mixed with less
than 5 per cent of oil.
This slime represents the broken down oil
and may be due to unsuitability, incorrect
manufacture, or to some Chemical action on
the oil in the service.
Broken down oil accumulates in the most
dangerous places, namely, the oil pipes which
lead the oil from the distributing pipe (T1,
Fig. 4) into the main bearings (F2). Partial
stoppage of the pipes may result.
Broken down oil also accumulates, as a
slime, on the water cooling coils in the oil
cooler, thereby decreasing the efficiency of
the cooler. The circulating oil assumes a
temperature higher than normal which, in
extreme cases, greatly impairs the life of
the oil.
If broken down oil forms in the oil pipe
leading to the governor, or inside of the
governor gear, the governor may stick and
fail to act. In consequence, the turbine
either will gradually slow down or gradually
inerease in speed mueh above the normal.
The parts of the governor gear with which
the oil comes in contact are very sensitive,
and the oil must be absolutel y clean and of
high quality to guarantee smooth working
of the parts.
Foreign Substances
Because of the penetr ating and cleansing
effeet of oil in a circulation system, every oil
circulation system must be thoroughly cleaned
after an initial run of 150 hours.
15