POWER February 2014 - 35

InstrumentatIon & Control
4. One of these trends is not like the others. In this case, the higher alarm point
did not detect low oil level, but the remote monitoring engineers weren't fooled. Source: Black
& Veatch
Because this was well below the alarm
point of 195F, no notice was taken of the
temperature increase (Figure 4). However,
remote monitoring engineers noticed the
trend and asked the operators to investigate
the issue. The problem was quickly determined
to be a very low oil level, which had
led to a loss of oil flow to the air heater's upper
guide bearing.
After adding 9 gallons of oil to bring
4B AH HOT END BRG TEMP
now running +20F hotter than oil temp
it back to proper level, bearing temperatures
returned to normal, and a potential
unplanned outage and expensive repairs
were avoided.
Case 4: Failure Is Not an Option. Alengineering
expertise. This remote M&D
implementation was highly successful, allowing
the operators to uncover and fix several
serious problems at the unit. Two notable
examples include an internal extraction line
failure and unexpected turbine deposits.
In the case of the extraction line failure,
a deviation in pressure ratios in the lowpressure
turbine pointed to an expansion
joint failure (Figure 3). Upon inspection
during a weekend outage, it was found
that the expansion joint had completely
failed, allowing steam admission directly
into the condenser.
In the case of the turbine deposits, six
months following a high- and intermediate-pressure
turbine upgrade, unit capacity
dropped approximately 17 MW, high-pressure
turbine efficiency dropped 4.8%, and
intermediate-pressure turbine efficiency
dropped 3.5%. Remote diagnostic efforts
ruled out stop and governing valve issues and
instead pointed to turbine deposits as the root
cause. This allowed for a shorter reparative
outage, during which a chemical wash restored
the capacity.
The monthly savings in fuel costs for these
reparative actions was estimated at $25,500
and $37,500, respectively.
Case 3: Oil Is the Lifeblood of Your
Bearings. In some instances, operators are so
busy responding to plant alarms and keeping
the power flowing that they can miss subtle
trends that point to potentially serious maintenance
problems down the road. Such was the
case with one unit, where the air heater guide
and support bearing temperatures suddenly increased
from their normal 140F to 160F.
5. A heat transfer short-circuit. Partition plate failures are a common source of hidden
efficiency loss in a feedwater heater. Source: Black & Veatch
coa's Warrick Power Plant is critical for
providing both power and steam for its aluminum
smelting operations in Newburgh,
Ind. So when continuous monitoring efforts
detected a slow increase in the feedwater
heater terminal temperature difference, it
was time to investigate. The increase was
confirmed by redundant sensors, so after
ruling out externally accessible options, an
internal visual inspection revealed a partition
plate failure in the feedwater heater
(Figure 5). The impact of this failure was
significant, resulting in a loss of 40 Btu/
kWh heat rate and 0.4 MW.
After repairs were made, another partition
plate failure was detected in the same manner
less than two years later.
Early Detection Saves Money
With the exception of the JTEC turbine deposit
case, most of these problems were not
easily detected by an already overworked
plant staff. According to Stan Piezuch, senior
performance engineer at Black & Veatch,
" There are many examples where
statistical anomaly detection has uncovered
a developing problem which is still below
alarm thresholds. And of course that's the
point, since it's beneficial to detect problems
as early as possible, giving the plant
staff more time and flexibility to deal with
the problem before damage occurs or they
lose production. "
An old saying in the data analysis world
posits: " uncontrolled information is noise
and risk; controlled information is power and
security. " Not only is this true, but in the case
of coal power plant operations, controlled information
is profit. ■
-Una Nowling (nowlinguc@bv.com)
is a project manager and technology
lead for fuels at Black & Veatch. She
has worked on fuels-related issues and
analyses at more than 550 different units
over 20 years, specializing in coal, natural
gas, and biofuels. She is also an adjunct
professor of mechanical engineering at
University of Missouri-Kansas City.
February 2014 | POWER
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POWER February 2014

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