| What happens when a highly efficient cogeneration plant meets
resistance from an inefficient wastewater pump? Engineers
at the 95-MW Cokenergy electrical generating facility discovered
the costly answer—crippling wastewater spills, and plenty
of them, due to the high particulate matter in the water drawn
from Lake Michigan.
Cokenergy is located at Ispat Inland Inc.'s Indiana Harbor
Works on the shores of East Chicago, IN. It's a steam turbine
generator facility, which provides electricity and process
steam to Ispat's steel-making operation. Cogeneration supplies
25% of the plant's electricity and 85% of its process steam.
Clean water is critical for making steam, but the ability
to deliver it was hampered by an outdated wastewater system—one
that relied on a single, undersized pipe to transport wastewater
and other liquids.
Because the pumps were constant-speed centrifugal types feeding
into the single pipeline, backpressure caused cavitation and
breakdowns. Overflowing tanks and environmental problems made
the situation all the worse.
Such problems aren't unusual. In fact, inefficient pumps
are so common throughout the industry that the DOE has devoted
programs to their improvement. The DOE advocates a new generation
of "intelligent" pumps that rely on sensors and microprocessors.
Just the energy reductions alone make a compelling argument
for an upgrade. How does saving $30,000 a year on a 200-horsepower
pump sound? Add in quick paybacks (months, not years), reliability,
plus maintenance savings, and it's easy to see why they're
an attractive solution for wastewater problems.
Cokenergy chose a "PumpSmart" system from ITT Goulds Pumps.
Based on variable-speed drive (VSD) technology, the systems
use sensors to adjust the pump's speed and flow rate, and
have built-in protection against a pump's unkindest enemies:
dry run and cavitation. Moreover, VSD technology makes it
easier to tie into existing pipelines because their sensors
can prevent overflow.
According to Mike Pemberton, manager of business development
and marketing for ITT PumpSmart Control Solutions, VSD control
systems with embedded intelligence offer more than protection
against system breakdowns—they save energy. "Let's say you
have a pump that can run at 1,000 rpm. If you slow it down
to about 900 rpm, the power consumption drops at a cubed rate,"
explains Pemberton. "So if a pump is slowed down 10%, the
energy consumption at that load may drop 30% to 40%."
Such savings haven't gone unnoticed by wastewater-intensive
industries, such as paper manufacturing—nor by the DOE. In
1998 the agency identified centrifugal pumps as the single
largest energy consumers in pulp and paper mills. When ITT
Goulds upgraded a pump system at Augusta Newsprint, DOE's
Office of Industrial Technology sponsored an event to showcase
the energy-saving technology.
Augusta had a compelling story. All told, the plant's use
of more than 150 pump systems accounted for a staggering 21%
of total power usage. For the showcase, ITT Goulds provided
a typical example of pump intelligence benefits with its upgrade
of Augusta's storage tower pump system.
The system was originally designed with a throttling-flow
control valve to manage flow from a 200-horsepower fixed-speed
pump. The valve put the pump under constant strain due to
backpressure and cavitation. Not surprisingly, excess energy
usage and costly maintenance nagged the system.
ITT Goulds retrofitted the pump with a variable-frequency
drive (in which frequency determines motor speed) incorporating
intelligent flow control. The motor's running speed dropped
from 1,150 rpm to an average of 450 rpm. Aside from the benefits
to the pump, the system eliminated the need for a control
valve and its cost of maintenance. Augusta calculated a total
savings of $720,000 over the pump's 20-year life cycle. Estimated
energy savings amounted to $30,000 per year. Along with three
additional pump upgrades, Augusta projected its energy reduction
at more than 5,200 MWh per year.
The savings reflect the research in the DOE's Motor Market
Assessment Report, which explains that replacing throttling
valves with VSD lowers the system's total energy use and can
result in savings ranging from 5% to 50%.
Why would plant designers create such inefficient systems
in the first place? Augusta's situation is typical. The design
was based upon a prevailing philosophy of the times: "Too
much is better than not enough."
During the era of low-cost energy, designers specified oversized
pumps to ensure throughput during peak production periods
or to accommodate future capacity growth. In this new era
of studies to track high-energy consumption, throttling down
oversized pumps with flow control valves is commonly identified
as an energy waster.
PumpSmart Control Solutions made five studies of Georgia
Pacific paper plants, and the typical assessment results show
substantial savings from low upgrade investments. For example,
at one plant the total installation cost to upgrade nine pumps
was $532,000. Total savings for three years was $1,022,000.
The mean payback period took just 13 months.
New plants can save much more, says Pemberton. "It depends
on the plant and a lot of factors, but at a minimum, 60% of
pumps could run in variable speed," he notes. "We've done
studies and at 60% it would cost less in capital and have
a smaller footprint. It's what I call de-materializing the
plant, taking the valves out of the pipes and sizing the pumps
properly. It means using smaller motors, smaller pumps, and
less models, which reduces inventory for spare parts. You
can also eliminate bypass valves, and all of their piping."
Another plus for industrial plants is the relief from manual
control. "Their problems are usually blamed on the operator,"
says Pemberton. "But it's impossible to get the valve and
pump to run without problems because it wasn't properly designed."
It's no surprise that the blame game disappears with pump
intelligence. Yet there's an additional benefit beyond running
the motor at its optimum efficiency point. These next-generation
pumps now collect data. In many cases, pumps reside on the
manufacturing floor, and are ideally located to access data
from the production process. Also, data from the pump's performance
can be used for predictive maintenance.
The new approach runs counter to traditional methods of pump
maintenance, which centered on scheduled preventive programs.
In the past, repairs and replacements were made whether needed
or not, and technicians often relied on experience and intuition
for their decisions. Intelligent pumps let technicians monitor
conditions in real time. Information on wear, stress, and
operation status allow for repairs on a need-to-be-made basis.
"We have software that can tell where the pump is wearing
out," says Pemberton, "such as the impeller. You can see declining
performance and set a schedule to coincide with the plant's
outage instead of having an emergency, which could shut the
plant down."
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Aside from lower energy, capital, and maintenance costs,
intelligent pumps offer a tangible benefit to the environment—reduced
pollution. Pemberton says the largest leak paths at refineries
and most chemical plants are the valves and pumps. Variable-speed
controls remove the valve and run the pump at a slower speed,
thus reducing internal stress on the pump and leakage.
With the many benefits intelligent pump systems offer, the
technology is far from a slam-dunk in terms of commercial
acceptance. However, it's certainly not a question of market
size. The ARC Advisory Group, a manufacturing and logistics
consultancy, expects the worldwide market to grow to $184
million by 2006. Outside of the US, the EU is advocating the
use of energy-saving pumps. The EU's motor challenge program
estimates that industry could save 10 billion euros a year
by using more energy-efficient motors. Carbon dioxide emission
would also fall by 100 million tons, equivalent to one-quarter
of the EU's Kyoto commitment. So why aren't manufacturers
rushing to make the intelligent choice?
The ARC group cites culture change among engineers as one
problem. From Pemberton's perspective, it's a lack of concern
for demand reduction in energy and production management systems,
and plugging that leak in the bottom line.
"Managers look at their budgets and the areas where they
need to optimize, such as pumps," says Pemberton, "but next
year the upgrades get lumped in with all capital projects
and usually fall to the bottom of the priorities. Upgrading
may have a great payback, but it's a relatively small one-time
shot compared to a bigger capital project worth a million
dollars. So there needs to be a management system that recognizes
the priority of optimizing pumps and getting long-term improvements."
Despite the resistance, Pemberton predicts continued growth.
He notes that in many mature industries, such as paper, lower
manufacturing costs are the only method of raising profits.
Moreover, new industries, such as Cokenergy, use intelligent
pumps as an efficient method for handling wastewater. That
makes overflowing tanks and pollution less of a threat to
the environment, and the bottom line.
ED RITCHIE, a writer specializing in technology, is a
frequent contributor to Forester publications.
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- September/October 2005
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