POWER May 2023 - 24

MARNIE SURFACEBLOW
again. " Out at Desert Moon, we've got
more than 1,000 acres of rows and rows
of shiny mirrors-you never saw such a
sight. It is a super high-tech system compared
to those old steam coal plants we
had at DeYoung, but I reckon about the
same thing. I mean, the sun heats the
water into steam, and we send it through
a double-casing reheat steam turbine at
2,400 psia. On a good day, we top out at
180 MW, but most of the time we run
about 90 to 140 MW. One difference, we
use an air-cooled condenser, so no more
zebra mussels, although, we sometimes
get bats hiding in it when the plant is offline
for a major outage. "
" Bat country ... I ... see. " Marnie
sipped her coffee and mused, " It's funny.
We love training new engineers, but
most of them think steam turbines are
old technology, nothing but mechanical
dinosaurs, making every turbine deck
like the Land of the Lost. Wait, I have an
idea. Yes, dinosaurs. It's so crazy it simply
must work ... "
As Marnie drifted off for a second,
Maya shared a concerned look with Willie.
" Moving on, " Marnie continued, " the
truth is steam turbines are likely to be
around for the rest of this century. Solar
plants like yours, Willie, geothermal
plants, nuclear fission-even someday
nuclear fusion-are likely to continue using
a steam turbine system to convert
heat into power. "
" And let us never be forgetful, ma'am,
fusion energy is only 25 years away. Always, "
Maya deadpanned.
" Well, I don't know about fusion power
or dinosaurs, " continued Willie, " but I
do know we got serious pump problems
at this plant. Here's the situation: we got
one small electric boiler feed pump [BFP]
to get us up to about 30 MW, one main
electric BFP to take us to about 130 MW,
and a steam BFP that can come online
at about 120 MW and take us to the top
of the cycle at 180 MW. Well, y'all may
know the plant is only four years old, and
it had a lot of problems with the solar reflector
actuators-those little things that
track the sun, " he said.
" I am aware of how power plants
work, young man, " said Marnie between
gritted teeth. " Maya, is there a problem
here we need to solve? "
" Perhaps you could proceed to show
Miss Surfaceblow what you demonstrated
on your laptop, Mr. McCoy, " interjected
Maya, seeing the exasperation
beginning to emanate from her boss.
" Sure, um, anyhow, because we
24
weren't running very much, the steam
plant only just had its first full maintenance
outage last month, and nothing
has worked right since, " Willie said
as he tapped away on his laptop and
showed Marnie some graphs from the
plant's distributed control system (DCS)
historian. " Well, as soon as we came
back online after the outage, the first
thing we noticed was that the bearing
temperatures on the two electric BFPs
read -999F. Now, everyone knows that
ain't right, so I had the instrumentation
and controls [I&C] techs check it out.
Turns out they were covered with extra
grease. In fact, there was grease all
over the place. I guess they figured just
spread it everywhere, and maybe some
will get into the bearings, right? The
steam pump uses a sealed oil system,
so it wasn't affected. Anyhow, the I&C
techs cleaned up everything, regreased
the bearings, and we started up the
next morning. "
" Oh dear, " Marnie said and shook her
head. Maya nodded for Willie to continue.
" But, the problem is, now the thermocouples
are reading too high. Before
the outage they ran about 100F, but now
they're running about 150-160F. So, the
I&C guys replaced the thermocouples,
but we didn't see any change. " Willie
displayed trend after trend on his laptop,
confirming his observations.
" Maya, do you have an idea what
went wrong? " asked Marnie.
" Yes, probably, " nodded Maya eagerly.
" This is why I wished to do this work and
help Mr. McCoy. "
" Well, shoot, if you two ladies know
the answer, don't keep a fellow waiting
at the altar, so to speak, " Willie said,
then regretted it immediately, as he was
faced with two withering stares.
Maya cleared her throat. " Mr. McCoy,
your I&C personnel, are they trained
properly in the maintenance practice of
lubricating electric motor bearings? "
Willie scratched the back of his sunburned
neck. " Well, Miss Sharma, I assume
since they are electric BFPs and
the I&C techs deal with electric items,
they would know the ins and outs of it
all, " he said. " Of course, they were the
ones who put too much grease in the
first time. " Willie paused, faced again
with two hard stares. " Maybe I should
ask them if they read the maintenance
job guide and did everything by the
book, huh? "
Maya shook her head. " There is no
need, as I am certain what happened.
www.powermag.com
It seems very likely they set the grease
pump at excessive pressure, or applied
excessive volume of grease to the bearings.
Perhaps ... no, I
will wager, as
Miss Surfaceblow often says, the power
station personnel did not remove the
grease drain plug prior to adding new
grease. This is done so the new grease
can push the old grease out and not overpressurize
the bearings. Grease was
then forced from the seals and leaked
from the pumps, but I believe it has also
leaked internally. We see this when too
much grease is applied, and the seals are
bypassed, and then the grease enters
the motor windings. "
" That's not good, but do you think
that's the problem? " asked Willie.
" I strongly believe it to be true, " replied
Maya. " When this happens, the
grease begins to cook onto the windings
with a hard shell. Just as when my auntie
Indira forgot to remove the frying pan
from the heat after making paratha roti-
the oil burned onto the bottom and never
was it fully removed. This will increase
electric resistance, and can quickly damage
insulation. You can see the increase
in resistance here in your trends after the
outage. See? The motor amperage is rising
immediately and leading the trend in
the temperature increase. "
" Gosh, " replied Willie. " We're going
to have to take all the doggone motors
apart and clean them out, right? "
" Maybe more than that, " Marnie added,
staring out at the night sky and adding
another empty paper coffee cup to
the stack balanced delicately on her tray
table. " You're going to have to make sure
the windings are so clean that they sparkle
like diamonds, fully test the windings
for shorts or arcing, test all the electrical
components, replace every seal, and
then carefully re-grease the whole thing
over again, and using a grease gun at the
pressure recommended by the manufacturer.
And make sure you have the
drain plugs out while doing this, so any
extra grease takes the path of least resistance-better
into a bucket than back
into the windings. "
Willie nodded the entire time, typing
notes furiously into his laptop. " I'm
sending an email right now to my maintenance
manager, and ... "
Oil and Water a Bad Mix
" Wait a minute, " Marnie said, turning to
face Willie. " You said you had other problems
too? Well, let's hear them. "
" Well, I think it's only one other probPOWER
| May 2023
http://www.powermag.com
POWER May 2023

Table of Contents for the Digital Edition of POWER May 2023
