pwr_may-2024 - 23

PLANT EQUIPMENT
coal-fired power plants, these pumps
can be up to 60,000 horsepower, so assessing
the operation of these pumps
regularly to maintain optimal efficiency
can result in significant energy savings. "
2. This multistage boiler feed pump would
be one of the most power-consuming
pumps within a power plant. Proper maintenance
of such pumps is important for
continued optimal performance. Courtesy:
North Ridge Pumps
designs of pumps which are a higher
initial investment but much quicker to
service, or have the option for 'pump
inserts' where the main working parts
of pumps can be easily changed, thus
not requiring complicated or time-consuming
service. "
" There are many pump types used
in power plants and it is difficult to rank
the importance because they all serve
a dedicated purpose, " said Gaydon.
" However, if we focus on the feedwater
system, the condensate pumps start
the process by pumping saturated water
to heaters and eventually to the boiler
feed pumps. The boiler feed pumps
then pump the liquid into the boiler. "
Gaydon told POWER: " These pumps
are engineered specifically for the demanding
application considerations. For
example, the condensate pumps are designed
to have low net positive suction
head [NPSH] requirements because the
liquid is very close to its vapor pressure,
and the boiler feed pumps are designed
for high flowrates and high differential
pressures so that the feedwater can be
forced into the boiler. "
" Boiler
feed pumps [Figure 2] are
variable speed to accommodate fluctuations
in demand, " said Martinez-Moore.
" Due to water being pumped at high
temperature there are often low levels
of suction pressure available, meaning
they are often fed by booster pumps to
eliminate such issues. Sealing on such
pumps is normally performed by mechanical
seal or by packed gland, which
can be preferred in applications where
low NPSH conditions may be present,
as mechanical seals can experience accelerated
wear in such conditions. "
Said Gaydon, " The boiler feed pumps
will be the highest power-consuming
pumps because of the high flowrates
and differential pressures. In traditional
May 2024 | POWER
Know the Variables
Power plant operators should consider
several variables in determining
the correct pump for use in a power
plant. " The specific application considerations
are the first place to start
[flow, head, NPSH, temperature, fluid,
etc.] and understand how variable they
are, " said Gaydon. " Manufacturers that
supply pumps for the power generation
market will have designs targeted to
each application. "
Gaydon told POWER, " Operationally,
the most important consideration is selecting
a pump that will operate near
its best efficiency point, or BEP, during
normal operations, and will always operate
within its allowable operating region
[AOR] for all conditions. The AOR is a
range of flowrates where the operational
reliability of the pump is acceptable. "
Some plants, such as combined
heat and power, or those using oil- or
diesel-powered turbines, will need
fuel transfer pumps. Martinez-Moore
told POWER, " Fuel transfer pumps,
also known as fuel forwarding or feed
pumps, ensure the turbines receive the
required volumes of fuel, at the required
pressure for burning efficiently. Fuels
may be pumped to a nozzle where the
fuel may be atomized, or directly to a
burner where it should meet a defined
duty point for the burner to produce the
required heat. "
Martinez-Moore said, " A typical fuel
forwarding pump set consists of a duty
and standby pump to ensure redundant
capacity, transducers to record the operating
pump pressure, and an integrated
control panel with variable frequency
drive to vary pump speed according to
the flow required. "
Moving Equipment
Pumping systems in power plants go
beyond those used to move liquids;
they also can help move equipment.
" High-pressure hydraulic pumps that
allow the positioning of heavy objects
within power plants are important to
give users added flexibility and portability
of what was traditionally a very
onerous task, " said David Lundquist,
global product manager of the SPX
FLOW Power Team. " SPX FLOW, under
the Power Team brand, manufactures
www.powermag.com
pumps that feature The Power Team motion
control system. This system was recently
used for a 36-point hydropower
rotor separation project. The project required
a tilt feature to level the rotor before
a 24-inch synchronous separation
of the rotor for maintenance. "
Lundquist told POWER, " Customers
have been asking for more solutions
around several common challenges,
including options to improve portability
and usability, equipment that better
pairs power with high flow capacity,
and pumps that are durable enough
for the most demanding applications. "
Those applications include compatibility
with piping systems, which can
encompass water piping, including service
and cooling water; fuel piping (for
gas or fuel oil); and chemical piping (for
ammonia, acid, etc.).
" When water is continually reused
from cooling towers within a closedloop
system, the water can become
contaminated due to it encountering
particles such as dust, as well as [becoming]
acidic due to the characteristics
of the process and the materials in
which the water comes into contact, "
said Martinez-Moore. " In boiler feed
applications, due to the nature of the
process with the water being repeatedly
boiled, the level of dissolved solids
within the water continually increases,
which can lead to scale accumulation
and calcification forming within the [piping]
system, with dosing pumps used
for the control of water quality and efficient
operation of the boiler. "
Martinez-Moore said water discharged
from a plant should meet
certain standards. " Dosing pumps are
used to dose flocculant for the clarification
of water, and [add] chemicals
to correct water pH to ensure it meets
the required levels for discharge consent, "
he said.
Martinez-Moore noted that piping
systems at power plants " can create
the ideal conditions for the growth of
Legionella bacteria, giving rise [to] the
requirement for a dosing system for microbial
control with biocides dosed to
prevent Legionella, " referring to bacteria
that causes Legionnaires' disease. The
U.S. Centers for Disease Control and
Prevention has said controlling Legionella
bacteria is an important consideration,
and a major reason pipe systems
at power plants must be " properly disinfected
and maintained. " ■
-Darrell Proctor is a senior
associate editor for POWER.
23
http://www.powermag.com
pwr_may-2024

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