DeltaV installation pays for itself on installation
In late 1997, Conoco Canada Ltd. activated the first application
of Microsoft Windows NT-based DeltaV digital automation system from
Emerson Process Management, communicating to remote SCADA
systems using OPC (OLE -- object linking and embedding --
for process control).
The 70-million cu. ft. per day (cfd) capacity Peco gas plant
near Edson, Alberta processes the Peco field's naturally sweet
gas and refines accompanying natural gas liquids into condensate
and fraction fluids. Until recently, control had been by panelboards
and single-loop controllers. The plant was too small to justify
conventional DCS (distributed control systems).
Conoco viewed the DeltaV system installation as paying
for itself as soon as it took over control.
Because the automation's I/O modules and channels could be
added while the controller is live, cutover was accomplished
over a 20-hour period without taking the plant off-line. A
20-hour outage, which would have been necessary with a conventional
DCS, would have cost $150,000 in lost revenue -- an amount
greater than the cost of the new system.
Problem
Efficiency problems drove Conoco's upgrade decision. Process
swings from gas liquids slugging at the plant inlet were a
continual issue with the former controls, because control
components weren't integrated. The various vessels in a process
train couldn't sense what others were doing, so steady-state
conditions were difficult to achieve.
Significant revenues in recovery of high-value liquids were
lost because processes could not be run at the edge of tolerance
windows at the high end of capacity. Excessive flaring, though
within regulatory limits, still reduced revenues up to $40,000
per year -- again because of process swings.
Unexpected shutdowns from major upsets, wide variations between
day and night temperatures during times when the plant was
unmanned, control failures, and other meddlesome variables,
cut revenue a minimum of $300 per lost hour.
Conoco also wanted to reduce. An example of excess was time
spent driving to wells -- the farthest of which is 1-1/2 hours
away--because a rudimentary SCADA system could not provide
remote compressor starts, among other deficiencies.
Solution
The solution Conoco Canada and Emerson assembled
consisted of: a single DeltaV controller fitted with 15 I/O
modules, three Pentium PCs running Windows NT 4.0 and DeltaV
workstation software, IEEE 803.2 Ethernet network linking
the above components, two-way SCADA radio, and Emerson
remote operating controllers as intelligent RTUs (remote terminal
units) at the well sites.
A second controller is being added to the network to concentrate
in one device the serial communications for the plant ESS
PLC, a gas chromatograph to fine-tune fractionating towers,
and several other instruments. A microwave link under construction
will permit the new automation system to tie into the Conoco
intranet.
Of the three PCs, one is configured as an operator station,
another as an engineering workstation (used also as a second
operator station), and the third as a DeltaV RTU-to-OPC integration
station for the SCADA system.
The new automation allowed Conoco to configure using IEC
1131 graphical methods rather than forms-based data entry.
Graphical configuration has proved a big timesaver. Also,
because our configurations are basically graphically generated,
documenting them is just a simple matter of printing out the
configuration worksheets.
Results
With the DeltaV quick response and increased control information,
process swings and discontinuities have been largely eliminated.
Shutdowns are rare. Flaring costs and greenhouse emissions
have been cut in half. And the plant is operating closer to
full capacity, so output is up.
Also with the increased information and easily-implemented
control the DeltaV system delivered, production of high-value
fluids has been maximized, and the relative volumes of the
different fluid types can be better adjusted to suit market
conditions. The new online gas chromatograph incorporated
into the automation system will further fine-tune and automate
the fraction towers with updates every few seconds. The improved
SCADA system has made well sites as automated and easy to
monitor and control as in-plant processes.
The remote location of well sites is transparent to the operators
in plant stations. The sites are presented as just another
set of real-time graphics, and the sites are alarmed and adjusted
the same as in-plant equipment. Driving to wells has been
reduced to maintenance efforts only.
OPC for seamless SCADA
Conoco Canada was a pioneer in the application of OPC in the
SCADA system to permit data passing to and from the ROC RTUs
to readily flow in and out of the Windows NT-based DeltaV
software, as well as in and out of Microsoft Excel and Microsoft
Access packages loaded into the PCs for recordkeeping, calculations,
and reporting.
OPC enables the radio-linked RTUs to appear and act as seamless
extensions of the in-plant portion of the system. In the near
future, worldwide users on the Conoco intranet will be able
to access Peco Field well-site data in real-time by accessing
the Windows packages.
Because of its scalability, the DeltaV process-control system
will grow with the plant and well sites, providing only as
much control -- and consuming only as much investment -- as
required at the moment. And with the easy integration of Windows
NT, the OPC standard, and Microsoft business packages, the
DeltaV system will continue to improve Conoco Canada's operations
-- from remote well sites, to the plant, to the business office.
Connect your OPC servers FREE with Emerson Process Management's
breakthrough OPC
Mirror Lite freeware. OPC is a key technology in the revolutionary
PlantWeb architecture, which changes the economics of process
automation. And the DeltaV system makes it easy.
back to top
|
