1. Process Control and Data Acquisition Systems
CM4120
Chemical Plant Operations
January 2005

2. Distributed Control System (DCS) Architecture
Used for continuous control of chemical processing
Control functions are distributed throughout redundant, deterministic networked computer architecture
I/O interface and level 1 control functions
advanced control functions
human interface
DCS replaced mainframe computer controllers
non-didtributed
single point of failure
Added a high level of robustness to control systems
Pre-configured functionality geared toward process industries, but a relatively high cost

3. Programmable Logic Controller (PLC) Architecture
Used for control where the devices are primarily discrete (the controlled devices are energized/de-energized and the inputs are open/closed circuit)
Provide very fast response (< .1 sec) to system changes
Typical applications are packaging, material conveyance, and waste water treatment
Very little, if any pre-configured functionality, but PLC’s are relatively low cost
In chemical processing, often are used along side DCS

4. SCADA – Supervisory Control and Data Acquisition System
Scalable systems that may provide some additional level of control and data acquisition “above” the controller, DCS and/or PLC level
Typically use non-redundant TCP/IP communications and therefore are not considered appropriate for direct process control
Built upon non-proprietary, off-the-shelf hardware
Very useful in large plant environments where data from many sources must be collected into a single location

5. DeltaV ProPlus Station
Emerson Process Management DeltaV and OSISoft PI in PSCC – System Overview
WE Network
DeltaV consists of a ProPlus station, several Operator Workstations, an MD controller, associated field instruments, and interconnecting wiring systems
PI communicates with the control system to collect, compress, and archive process data
PI Server
Steam
PSCC
Network Switch
PSCC_DeltaV
Redundant Hub
Plant Area – valves, xmitters
DeltaV ProPlus Station
Professional WorkStations
MD Controller
and I/O Cards

6. Emerson Process Management DeltaV and OSISoft PI in PSCC – Networking
WE Network
Control systems must be “invisible” to the outside world – use isolated networks
PSCC_DeltaV is a “Control Network”
PSCC is a “Plant Local Area Network” w/ Steam as the gateway to the “Office Network” (WE domain)
PI Server
Steam
PSCC
Network Switch
PSCC_DeltaV
Redundant Hub
Plant Area – valves, xmitters
DeltaV ProPlus Station
Professional WorkStations
MD Controller
and I/O Cards

7. DeltaV System – How it works
PI Server
Steam
Operator WorkStations
PSCC_DeltaV
Redundant Hub
ProPlus Station
MD Controller
Control network is Windows XP Workgroup – PSCC_DeltaV, uses Windows Networking and TCP/IP protocol
Control system configuration and operations graphics building are done thru ProPlus and/or Professional Workstations
ProPlus station stores configuration and archives data, displays information
Operator stations archive data, display information

8. DeltaV & MD Controller – How it works
PID control, Fuzzy control, discrete control, signal conversions, alarming, etc. are continuously executed by the MD controller
Field instruments and final control elements are wired individually to the I/O cards in the MD controller
Also, “networked instrumentation” available – Foundation Fieldbus, ASi bus, DeviceNet, etc.

9. MD Controller I/O – How it works
and I/O Cards
Plant Area – valves, xmitters
I/O cards are specific to device requirements
4-20 mA input, 4-20 mA output
24 VDC input, 24 VDC output, etc.
ASi Interface
Foundation Fieldbus Interface

10. Input-type Field Devices – Transmitters
Wiring to field junction cabinet
Level transmitter
Thermocouple head
Wiring from transmitter to temp measuring element
Temperature transmitter

11. Field Junction Cabinet
Single pairs from field devices
8 pr. Cables to controller cabinet

12. MD Controller Cabinet MD controller I/O cards Zener barriers
8 pr. cables from field junction cabinet
2nd I/O chassis

13. Output-type Field Devices – Transducer
Single pr. cable from field termination cabinet
Solenoids for 2-position air-actuated ball valves
Air lines to ball valves
Current to pneumatic transducers
Wire prs. to solenoids
Wire prs. to transducers
Air lines to control valves

14. Output-type Field Devices – Regulatory Control Valve
Air line from transducer
Actuator w/ positioner
Control valve
Block valves
Bypass valve

15. Output-type Field Devices – Ball Valve w/ Actuator
Air line from solenoid
Ball valve body
Actuator
Process line

16. DeltaV & Foundation Fieldbus
(4) mass flows and (4) densities
(3) 8 multiplexed RTD temps
(2) temp-only transmitters

17. PI – Plant Information System
Control Room
Network Switch
Operator Stations
-Excel
PIPC
- ProcessBook
DeltaV PI Server
WE Network
- PIPC
PI is a process data historization and data retrieval system
PI server (Steam) is PDC for the Plant network and is also on WE network
PI data are available anywhere on campus network
PIPC is Excel add-in
ProcessBook is graphical tool for viewing process and process data
PI Server
PI-to-PI Interface

18. PI – Plant Information System
Data Historian system is required part of process management system
Long-term data storage/ retrieval system
Optimizes use of hard drive storage space and permits quick recall of archived data
Includes data retrieval software tools
OSISoft, Inc. PI system
Import process data into supervisory control or process monitoring applications
Link process control systems with business management systems
Provide data for production and compliance reporting

19. PI – How it works
A PI “tag” is configured for every piece of data you want to archive
Collected tags are scheduled to retrieve data periodically or upon the occurrence of an event
Data are brought into the archive thru a filtering and compression algorithm
Data are not archived unless they pass the filter and compression tests
When data are retrieved from the archive and presented in a series, the individual points are extrapolated between the stored data
Tags can also store manually entered (lab) data