Process Control and Data Acquisition Systems

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. 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. MD Controller PI Server Steam PSCC_DeltaV Redundant Hub ProPlus Station Operator WorkStations DeltaV System – How it works • 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. Plant Area – valves, xmitters MD Controller and I/O Cards MD Controller I/O – How it works • 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. 8 pr. Cables to controller cabinet Field Junction Cabinet Single pairs from field devices

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. WE Network - PIPC - ProcessBook Control Room Network Switch DeltaV PI Server • Operator Stations • -Excel • PIPC • - ProcessBook PI – Plant Information System • 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