Thirty years without a
complete oil change usually
would be considered impos-
sible. In this case, there was
makeup fluid over the 30+ years, which
amounted to slightly more than the system
volume on each of the two units. The testing
parameters for acid levels, particle counts,
water and conductivity were maintained
within specifications with a few exceptions.
Varnish was identified, but no exclusive
tests such as membrane patch colorimetry
(MPC) or quantitative spectrophotometric
analysis were conducted to confirm or
quantify the amount of varnish. Of course,
the 30 years without an oil change did not
come without consequences, as was discov-
ered after the system flush and chemical
cleaning were completed.
The System and
Components
The Seminole Electric Cooperative is a
two-unit, 1,300-megawatt coal-fired gener-
ating station south of Jacksonville, Florida.
The electrohydraulic control (EHC) reser-
voirs and systems are larger than normal,
utilizing 2,400 gallons of fluid per unit.
Three 170-gallon-per-minute submerged
screw pumps are located in the reservoir.
When required, they provide flow at 580
pounds per square inch at the turbine level.
There are 10 control-valve and 10 stop-
valve hydraulic actuators on the
high-pressure, intermediate-pressure and
low-pressure turbines. A full-flow filter
offers 25-micron filtration up to the turbine
New oil vs. 30-year-old oil
By Brian Thorp, Seminole Electric Cooperative
6
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January - February 2017
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www.machinerylubrication.com
COVER STORY
