EQUIPMENT LAYUP
Preservation program
works for outages from one
month to several years
hen Araucaria Power alcanti de Albuquerque (Fig 1) told hydropower, and when reservoirs are
Station successfully com- the editors that OEM recommenda- full, thermal generating plants may
pleted acceptance tests tions were strictly followed during be in layup for months. To learn more
in September 2002, no this process.
about the countrys energy sector,
one thought the facility would spend
Proof of the programs success was visit www.psimedia.info/handbooks.
the next four years in layup and, that recommissioning and commer- html and click on the 2010 Brazil
in the process, become a center of cial operation were achieved in only Energy Handbook at the upper right
excellence for equipment preserva- seven weeks following the long out- corner of your screen.
tion that would earn plant personnel age, and plant availability is consisthe respect of combined-cycle owner/ tently above 98%, except for a forced Program overview
operators worldwide.
outage caused by a short circuit in
The 484-MW, 2 1, 501FD2-pow- the steam turbines generator stator Albuquerque described plant preserered facility was built in southern in early 2008.
vation as a combination of protecting
Brazil, near Curitiba, the capital of
Recently, the plant O&M team equipment against degradation
Parana state, by a consuch as is caused by corsortium consisting of El
rosion, erosion, sunlight
Paso Corp, Copel, and
effects, etcand mainPetrobras. El Paso is the
taining its operability
gas producer known to
through periodic operamost readers, Copel is
tion and/or testing.
the state-owned electric
To achieve these goals,
and telecommunications
long-term preservation
firm known officially as
programs were develCompanhia Paranaense
oped for the gas turbine/
de Energia, and Petrogenerators (GTG), heatbras is the semi-privarecovery steam generatized oil giant controlled
tors (HRSG), steam turby the Brazilian governbine/generator (STG),
ment and known formaland balance-of-plant
ly as Petroleo Brasileiro
(BOP) systems.
SA. El Paso later sold its
The foundation for
60% share in the facilthis effort was the experiity to Copel, which now
ence Copel personnel had
owns 80% and operates
gained at other plants,
the plant; Petrobras holds
assistance from NAES
the remaining shares and 1. Marcos Freitas, operations supervisor; Fernando Albuquerque, Corp (sidebar), and, as
manages the gas supply operations manager; and Jean Ferreira, operations shift leader (l
mentioned earlier, docuand electric sales.
to r), are members of the team that developed the long-term pres- mentation from OEMs
The hold-up in com- ervation program for Araucaria
and service providers.
mercial operation had
Regarding the HRSGs
to do with contractual terms in the reviewed and improved the long-term specifically, some of the lessons
power purchase agreement that were program to enable faster installation learned and best practices described
not consistent with the intent of Bra- and removal of preservation systems, in the HRSG Users Handbook, comzilian laws.
thereby enabling their deployment piled by Robert C Swanekamp, PE, of
Over the four-year layup, Araucar- for shutdowns of one month or more the HRSG Users Group, were incorias O&M team developed and imple- in duration when economical and porated into the Araucaria plan.
mented a comprehensive equipment consistent with grid requirements.
Key features of the program
preservation program for the outdoor In a typical year, the plant operates included the following:
plant. Operations Shift Leader Jean at or near base load in winter and as n Maintain relative humidity (RH)
Carlos Nunes Ferreira, Operations needed during the hydro season.
on the gas side of the HRSGs, and
Supervisor Marcos de Freitas, and
Note that more than 80% of Brain the ST low-pressure (LP) secOperations Manager Fernando Cav- zils electricity needs are met by
tion, at less than 40%. Fig 2, from
92
COMBINED CYCLE JOURNAL, First Quarter 2010
EQUIPMENT LAYUP
Weight increase, milligrams/square decimeter
120
100
80
60
40
20
0
20
40
60
80
Relative humidity, %
100
2. Relationship between corrosion
rate and the moisture content of air
shows the importance of maintaining
relative humidity below about 40%
a maintenance guide supplied by
STG manufacturer Alstom Power,
shows corrosion products are produced at an exponential rate when
RH exceeds about 60%.
Analyze and maintain coolingwater chemistry on a regular basis
according guidelines provided by
the tower supplier and GE Water
& Process Technologies.
Protect exposed surfaces by painting in accordance with recommendations from Lactec, a local
technology institute and formerly
part of Copel.
Perform tests and inspections
according to long-term shutdown
procedures provided by the manufacturers and conduct preventive,
predictive, and corrective maintenance as recommended in the
plant maintenance manual. The
foregoing activities must comply
with environmental, safety, and
health regulations and are facilitated by use of Copels computerbased O&M operations management system.
Keep all space heaters for electric
3. Dual-pressure HRSGs produce
steam at 1465 psig/977F and 81
psig/507F
4. Curtains prevent air from entering
the gas turbines compressors
motors and generators on automatic when the equipment is not
in service and check heater performance quarterly.
HRSGs, steam systems
Each of the plants two dual-pressure
HRSGs (Fig 3) has a kettle boiler
incorporated in the LP section. Its
purpose is produce steam
while removing heat from
compressor discharge air
used for rotor cooling. Arau- Stack
carias dry layup procedures
call for first draining the (1) water
side of the boiler, including superheater, evaporator, and economizer
panels; (2) HP and LP steam piping,
(3) kettle boilers, and (4) the water
side of the fuel gas heater.
Step two: Backfill those sections
with nitrogen and pressurize the
inert atmosphere to about 7 psig.
Finally, check the concentration of
oxygen in the inert atmosphere quarterly, bleeding and filling with fresh
nitrogen as necessary. Albuquerque mentioned the desire to reduce
nitrogen pressure to decrease its
consumption. Copel is investigating
the installation of more sensitive
pressure gages for this use during
layups, as well as the advantages of a
nitrogen generator.
A plastic curtain closes off the air
inlet to the gas turbine (Fig 4). Initially, a curtain also was installed
at the stack entrance to isolate the
HRSG but that has been replaced
by a duct balloon, which is easier
to deploy (Figs 5, 6). Dehumidifiers
installed outside the HRSG (originally portable and installed inside)
condition the space from the turbine
inlet to the stack balloon to 40% RH.
Space temperature and humidity are
monitored via the DCS and alarms
sound when limits are exceeded.
Such improvements have reduced
dramatically the manpower requirements and time needed to install
and break-down the preservation
system. Specifically, the total effort
now takes 25% or less time than was
required originally, making the system viable for outages of about one
month and longer.
To illustrate: The plastic curtain
at the HRSG outlet took four people
16 hours to install, including erection of the scaffolding required, and
four people 12 hours to remove it.
Two people can deploy the duct balloon in about an hour, and take it
out of the stack with the same level
of effort. Also, it originally took four
Stack balloon
Plastic curtain
Compressor
Turbine
Heat-recovery
steam generator
Gas-turbine
air inlet
Dehumidifier
Humidity
indicator
Corrosion
test coupon
5. Curtain and stack balloon prevent outside air from entering the gas turbine
and the gas side of the HRSG. When the preservation system was first
installed, there was a curtain between the HRSG and the stack and portable
dehumidifiers were located inside the boiler casing. The arrangement shown is
the optimum solution
COMBINED CYCLE JOURNAL, First Quarter 2010
6. Duct balloon is simple to install
through manhole accessible from
catwalk
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EQUIPMENT LAYUP
Dry air
Process air
Wet air
Air heater
Reactivation air
Drive motor
7, 8. Dehumidifier located outside the HRSG casing (left) works as illustrated at right
man-days to install electric heaters
and dehumidifiers inside the HRSG
and another three to remove them.
Both steps are avoided by use the
permanently installed dehumidifier
described in Figs 7 and 8.
Today the major effort in preservation system implementation is installation of the plastic curtain in the GT
inlet, a task that takes two people
about six hours to complete. Removal
takes two people four hours.
HRSG and main-steam system
fluid handling equipment operated or
tested periodically are the following:
n Water-level control valves for the
HRSG drums.
n D e s u p e r h e a t e r s p r a y - w a t e r
valves.
n Blowdown valves.
n HP and LP superheater drain
valves.
n Fuel-gas heater valves.
n All HP and LP steam-system
valves.
n Blowdown-system sump pumps.
n Turning-gear motors.
n Control oil pumps.
n Evaporative-cooler pumps (every
Gas turbine/generators
The 164-MW Alstom ST is comprised
of HP and LP turbines arranged on
one shaft. HP superheated steam flows
through the former and into the latter, where it is supplemented by steam
from the HRSGs LP superheater.
The condenser hotwell was drained
in accordance with the OEMs recommendations and the ST LP section
originally was separated from the
condenser with a plastic curtain like
that used in the GT inlet. Reason for
the curtain here was that the circulating water system had to remain in
service to prevent wood members in
the six-cell mechanical-draft cooling
tower from drying out.
Heaters and dehumidifier were
installed at the ST exhaust to keep
the moisture level below 40% RH. Air
temperature and humidity inside the
turbine were monitored continuously.
As was done for the HRSG, a
ST dehumidifier was permanently
The preservation plan for the GTGs
was based on the OEMs recommendations, which proactively guard
against corrosion. The inlet curtain
and stack balloon described in the
HRSG section are the first line of
defense against corrosion. In addition,
compressor bleed valves, manholes,
inspection doors and other openings
were sealed to prevent atmospheric
air from entering the dehumidified
engine. Any leakage through seals,
walls, roof, doors of the GTC enclosure were repaired to prevent contamination by outside air.
The following equipment was tested or operated weekly, according to
the test schedule developed for Araucaria, except where noted:
n Main lube-oil (LO) pumps.
n DC emergency LO pumps.
n LO vapor extractors.
94
other day).
n Compressor washing systems
(monthly).
n Igniters (command test).
The plants valve test schedule
called for periodic testing or operation of these flow-control devices:
n LO-cooler temperature control
valve.
n Main-gas-line vent valve.
n Stages A, B, and C gas control
valves (command).
n Pilot-gas control valve (command).
n Kettle-boiler air bypass valve.
n Coolant-flow control valve for disk
cavities 2 and 3.
n IGV command.
n LP and HP compressor bleed
valves (command).
n Instrument-air valve (command).
Steam turbine/generator
installed outside the LP section (Fig
9) and arranged as shown in Fig 10
to eliminate the need for installing/
removing plastic curtains and the
scaffolding needed to accommodate
their installation and removal.
ST auxiliaries operated or tested
weekly:
n Main lube-oil (LO) pump.
n DC emergency LO pump.
n LO vapor extractor.
n Turning-gear motor.
n Control oil pump.
n LO purifier pump.
n Gland seal-steam condenser
exhausters.
n Jacking-oil pump.
Condensate system
The condensate system has two fullsize pumps, preserved as follows with
motor and pump coupled throughout
the layup period:
n Pump pit maintained dry.
n Pump shafts manually turned
twice monthly.
n Bearing lube replaced semiannually.
n Condensate piping from the pump
to the HRSGs was pressurized to
about 7 psig with nitrogen.
n Suction and discharge piping was
drained monthly.
Valves operated or tested as part
of the preservation program were the
following:
n Condenser makeup control valve.
n Condenser rejects control valve.
n Condensate minimum-flow control
valve.
n HP and LP steam-bypass desuperheater spray-water control valves.
n Spray-water control valve for HP
steam serving steam seals.
n Steam-jet air-ejector hogging and
holding valves.
n Spray-water valve in condenser
neck.
n Fuel-gas-heater temperature control valves.
COMBINED CYCLE JOURNAL, First Quarter 2010
EQUIPMENT LAYUP
Condenser
Steam-turbine
exhaust
Cooling
water
Hotwell
Dehumidifier
Humidity indicator
Corrosion
test coupon
9, 10. Steam turbine has a separate dehumidifier (left) which is located external to the unit (right)
n Backpressure control valve for
STG seal water to the STG vacuum-breaker valve.
Boiler feedwater system
Two full-size feedwater pumps are
provided with each HRSG. Each pump
transfers water from the LP section to
the HP section and is equipped with
an auxiliary LO pump.
The boiler-feed pumps were drained
and suction, discharge, and recirculation valves opened. This allowed
nitrogen in the HRSG steam/water
circuit to inert the BFPs and connecting piping as well. Pump shafts were
manually rotated quarterly as recommended by Sulzer, the pump OEM.
The BFP auxiliary LO pumps also
were exercised quarterly.
Auxiliary systems
Fuel gas system piping was
drained, vented, and pressurized
with nitrogen. Valves were tested
periodically.
Instrument and service air systems remained in service during the
layup. Use of the redundant compressors and dryers was alternated
according to the Plant Equipment
Test Schedule.
Closed cooling-water (CCW)
system also remained in service and
the use of redundant equipment
alternated.
Condensate/feedwater chemical control system (amine and oxygen scavenger for condensate and
phosphate for feedwater) was out of
service and inspected and maintained
NAES forms company in Brazil
NAES Corp, Issaquah, Wash, recently formalized its presence in Brazil by
launching NAES Servicos de Operacao e Manutencao Eletrica Ltda, with
headquarters in Rio de Janeiro state.
The company sees a bright future for
Brazil, the worlds fifth most populous nation and 10th largest electricity market.
NAES Corp is not new to international markets. It began working
outside the US in the mid 1990s,
following the lead of powerplant
developers chasing promising
opportunities in Latin America and
the Caribbean. At one point, NAES
had as many contracts in those
markets as it had at home. Today
the company provides O&M services
for generating plants in Canada,
Mexico, and Colombia, and recently
signed an agreement to operate and
maintain one Brazilian project as it
actively pursues others.
NAES was working in Brazil prior
to establishing NAES Servicos.
Activities included participation in
the development and implementation of Araucaria Power Stations
long-term preservation program.
Operations Manager Fernando
Albuquerque said NAES advisors, who were onsite to assist
in the development of O&M programs before plant commissioning, remained after the facility was
placed in layup to share their preservation experience. Albuquerque
recalled their significant contributions in the areas of valve and motor
care and testing that were the first
steps towards a more comprehensive preservation program.
NAES remains involved with the
Araucaria project to this day, advising Copel on gas-turbine matters.
NAES has deep experience in 501F
technology, having operated and
maintained more than two dozen of
these engines.
COMBINED CYCLE JOURNAL, First Quarter 2010
according to the Plant Maintenance
Program.
Steam and water analysis system remained in service with a continuous flow of demineralized water.
Demineralized water system
was operated quarterly to produce
boiler-quality water and maintain
the normal level in the demin tank.
All functions of all equipment in the
two parallel trains were tested and
verifiedincluding demin-water production, rinse quality, regeneration,
backwash, etc.
The circulating water system
serves the surface condenser and
CCW plate heat exchangers and provides quench water to the HRSGs
blowdown systems. Operation of the
3 50% pumps was alternated to
assure one pump was on at all times
to keep the cooling towers wood
members wet and to provide blowdown for the wastewater system
clearwell. Operation of the six tower
fans also was alternated weekly.
The raw water system remained
in service to supply water to the GT
evap coolers. Filter feed pumps and
the filter backwash pump were run
quarterly.
The wastewater system, including the sewage treatment system,
operated continuously. The waste
neutralization tank was operated
quarterly (in concert with the demin
water system), sump pumps and
the oil/water separator whenever it
rained.
Chemical feed system remained
in service and chemistry was monitored daily.
Plant DCS and major equipment
control systems were kept in service
and exercised as recommended by
the manufacturers.
The plant auxiliary electric systems, backfed from the grid, remained
in service. The emergency diesel/generator also was maintained ready to
enter service when required. ccj
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