POWER March 2014 - 55

OPERATIONS & MAINTENANCE
Table 1. Payback analysis for a
typical 500-MW coal-fired unit. The
savings calculations are based on an 85% capacity
factor, 10,550 kJ/kWh heat rate, and
average coal heat content of 5,500 kcal/kg at
$80/ton. The incremental electricity sale price
is assumed as $30/MWh off peak (75% of the
operating hours) and $150/MWh on peak (25%
of the operating hours). Source: Sealeze
Economic factors
Fuel savings
Auxiliary power savings
Total savings
Installed cost of brush APH
seals
Payback
Savings/cost
$1.5 million/year
$0.52 million/year
$2 million/year
$100,000
~18 days
tegral protective shield.
Since that design update, the brush seals
continue to outperform the original steel strip
seals more than five years after installation
and are expected to continue to perform to
specification through at least four outage
cycles. During the past five years, the plant
has been able to postpone two planned APH
outages-another significant cost savings.
Two other brush seal installations have experienced
similar results. Radial and circumferential
brush seals were installed in 2010
on two 8-m-diameter horizontal APHs at a
300-MW coal-fired unit located in the U.S.
(the plant wishes to remain anonymous). The
plant reports leakage rates remain well under
10%. In fact, air leakage tests confirmed
leakage rates of 5% and 7% on APH-A and
APH-B, respectively.
In 2010, radial and axial brush seals were
installed on a 10-m-diameter vertical Ljungström
APH at a 750-MW coal-fired plant
located in the U.S. (this plant also wishes to
remain anonymous). Both the radial and axial
brush seals remain in excellent condition after
more than 2.3 million impacts to the sector
plates during 11,760 hours of service over
490 days (Figure 5). The brush profiles remain
essentially in the as-installed condition. Seal
integrity remains intact as the seal conforms to
gap size variations and surface irregularities.
APH seal degradation is difficult to identify
and is often overlooked as responsible for
loss of fan margin, loss in boiler efficiency,
and consequential problems with downstream
air quality control equipment, particularly
the SCR. Chances are your plant is currently
troubled by poor APH performance caused by
increased seal clearances in the hot condition,
5. Seal inspections. The radial (top)
and axial (bottom) brush seals remain in asinstalled
condition after 11,760 hours of operation.
Source: Sealeze
seal erosion, inappropriate seal materials, or
improper seal settings. Installing stainless steel
brush seals is one of the few low-risk, highreward
upgrades that can be easily completed
during a typical planned maintenance outage.
Better yet, the cost of the stainless steel brush
seal retrofit will likely be repaid by improved
boiler efficiency quicker than the duration of
the outage. ■
-Pavan Ravulaparthy (pkumar@sealeze.
com) is business development manager
for Sealeze. Ravi Krishnan (ravi@
krishnaninc.com) is managing director of
Krishnan & Associates.
Creating Client VALUE
is our Business
SCAFFOLDING | COATINGS | INSULATION | REFRACTORY | FIREPROOFING | CUI MANAGEMENT
HOT TAPPING | CATHODIC PROTECTION | FORMING AND SHORING | FIELD MACHINING
Providing you access to
the safest, smartest and
most efficient specialty
services.
For more information contact us at:
281.404.9397 or info@beis.com
Brand Energy & Infrastructure Services is a leading provider of specialty
services to the power industry. Our unique multi-service approach
delivers significant savings to our clients on their maintenance, outages
and capital projects by reducing manpower requirements, improving
communication through a single point of contact, and ultimately,
delivering enhanced productivity.
www.beis.com
CIRCLE 22 ON READER SERVICE CARD
March 2014 | POWER
www.powermag.com
53
©2014 Brand Services, LLC All Rights Reserved.
http://www.beis.com http://www.powermag.com
POWER March 2014

Table of Contents for the Digital Edition of POWER March 2014
