DeltaV improves boiler operation, efficiency for Norfolk
Southern
A new boiler control package installed with the DeltaV digital automation
system solved operating problems for the Roanoke, VA, locomotive
shops of Norfolk Southern Corp. Within a few hours of startup,
combustion efficiency dramatically increased in the company's
four 1950s vintage, stoker-fed, coal-fired boilers. The new
system virtually eliminated manual intervention of the control,
improved safety, and reduced oxygen levels in the stacks.
These improvements were achieved using the economically scalable
DeltaV system with a preconfigured boiler control,
rather than costly distributed controls and custom-engineered
strategies. The new package replaced a DCS that had been used
for the last 15 years. The steam from the four boilers, each
rated at 70K pph at 160 psig, is used to power three air compressors,
heat water for parts washers, and heats the facility.
The challenges
Limitations of the old controller made changes and efficient
boiler operation difficult. For example, when two units operated
at the same time, only one could be managed automatically.
The other had to be controlled manually with loads fluctuating
between the two. Many of the control loops had to be manually
controlled at all times.
Another problem was fan control. The induced draft fan ran
erratically and the control system occasionally shut it off
without stopping the forced draft and overfire fans. The furnace
would become pressurized, forcing the furnace doors open and
creating the potential for dumping burning coal onto the floor.
To ensure safety, operators had to control the fan manually
to stabilize boiler pressure and prevent smoke emissions.
Scalable control solution
The DeltaV system can accommodate even the biggest control
configurations, yet it can scale down to bring control to
many types of operations once considered too small for a fully
automated control system.
The new system automatically controls about 250 I/O. at the
Roanoke shop, controlling the four boilers, economizers, precipitators,
ID fans, water decarbonization units, deaerators, condensate
storage, and the feedwater pumping system. And there's plenty
of capacity left to expand control to the water treatment
system and the air compressor at a future date.
Applying the strategies
The pre-configured strategy and software simplifies system
engineering, installation, configuration, use, and maintenance,
while providing tight control of the medium-sized boilers.
Cost was a fraction of that generally required for a custom-engineered
strategy.
The new control package now operates the boilers automatically,
even when more than one boiler is online. The system also
monitors all the inputs from field sensors continuously. Operators
quickly accepted the system with its PC-based, Windows familiarity.
The 25 displays employ bright colors and high resolution to
help generate eye-catching, easy-to-read graphics.
Trend reports let the superintendent analyze any given time
period to determine if any change is needed. Totalizers in
the system track fuel use and steam production, providing
information for financial performance reports.
And the system's open architecture allows the company to
integrate intelligent field devices, assist management solutions,
and business applications to provide the information, control,
and management capabilities needed to increase performance
levels and control costs even further.
For additional information, visit Boiler Control
Package Solutions
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