Process Control and Data Acquisition Systems

1. Process Control and Data Acquisition Systems CM4120 Chemical Plant Operations January 2008

2. Outline • Types of Control Systems • Control System Architecture for the PSCC • Brief Recap of Process Instrumentation Connections to Control System • Data Archival and Retrieval System

3. 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 the mainframe computers of the 1970’s • non-distributed • single point of failure • Added a high level of robustness to control systems • Pre-configured functionality geared toward process industries, but have a relatively high cost

4. Programmable Logic Controller (PLC) Architecture • Used for control where the devices are primarily discrete • 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

5. Safety Instrumented Systems (SIS) Architecture • An over-ride control system that takes the process to a safe state when predetermined abnormal conditions occur • Also called Emergency Shutdown System (ESD, ESS), Safety Shutdown System (SSD), and Safety Interlock System • Includes the logic control system and all the associated instrumentation including sensors, solenoids, valves, and actuators • Typical applications are burner controls on furnaces and exothermic reactors • Used with, but always physically separated from, process control systems

6. 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 • Used in large plants or across several plant sites where data from many sources must be collected into a single location

7. PSCC Control System Architecture What we have in the PSCC: • Field instrumentation for measurement and final control • DCS for process control and data acquisition • Uses OSIsoft PI for data archival, retrieval, process management • Windows networking and TCP/IP for communications

8. mtu.edu Network PSCC Router PI Server PSCC_DeltaV Redundant Hub Pilot Plants – valves, xmitters DeltaV ProPlus Station Professional WorkStations MD Controller and I/O Cards Emerson Process Management DeltaV and OSISoft PI in PSCC – System Overview • ProPlus DeltaV server • 4 Operator Workstations • MD controller w/ I/O interface cards • Field instruments and interconnecting wiring systems • PI Server

9. Emerson Process Management DeltaV and OSISoft PI in PSCC – Networking mtu.edu Network • Business systems need access to data from control systems and production areas • PSCC_DeltaV is a secure Control Network (green) • Plant Network is local network for plant operations (red) • Plant data is available to the outside thru alias “steam.we.mtu.edu” Plant Network Router steam.we.mtu.edu PI Server uolab-pi PSCC_DeltaV Redundant Hub DeltaV ProPlus Station (4) Operator WorkStations MD Controller and I/O Cards

10. MD Controller 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

11. DeltaV & MD Controller – How it works • PID control, discrete control, signal conversions, alarming, Fuzzy control, 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.

12. 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

13. Process Instrumentation • Input devices used to “see” what’s going on in the process • Output devices control the process • Wiring systems used to connect instrumentation to the DCS

14. Input-type Field Devices – Transmitters Wiring to field junction cabinet Level transmitter RTD or T/C head Wiring from transmitter to temp measuring element Temperature transmitter

15. 8 pr. Cables to controller cabinet Field Junction Cabinet Single pairs from field devices

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

17. Output-type Field Devices – Transducer 8-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

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

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

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

21. Data Acquisition and Process Management System OSIsoft PI system including: • ProcessBook • DataLink • Batch Management, SPC, Performance Equations, etc.

22. PI – Plant Information System to MTU’s network Router steam.we.mtu.edu • PI is a process data historian and data retrieval system • PI server (uolab-pi) is isolated from mtu.edu thru router “steam” • PI data are available anywhere with access to www and PI client software • PIPC is Excel add-in • ProcessBook is graphical tool for viewing process data PI Server PI-to-PI Interface PSCC_DeltaV hub DeltaV PI Server • Operator Stations • -Excel • PIPC • - ProcessBook

23. PI – Plant Information System • Data Historian system is required part of process management system • Long-term data storage/ retrieval system • Access to real-time snapshot data without risking unauthorized access to control system • Optimizes use of hard drive storage space and permits quick recall of archived data • Includes data retrieval client 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

24. 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 time series, the individual points are extrapolated between the stored data • Tags can also store manually entered (lab) data