Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Process Control and Data Acquisition Systems CM4120 Chemical Plant Operations 1 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 Added a high level of robustness to control systems Pre-configured functionality geared toward process industries, but a relatively high cost 2 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 3 SCADA – Supervisory Control and Data Acquisition System Scalable systems that 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 4 Rockwell Automation ProcessLogix DCS and OSISoft PI in PSCC PI is process data management system WE Network “External” historized and real-time data requests are served thru PI Server Operator Stations and other “internal” data users communicate thru PLX Server Control executes at PLX Controller Plant Area – valves, xmitters PI Server Control Room Network Switch ProcessLogix Server PLX Controller and I/O Cards Operator Stations 5 ProcessLogix – How it works Control Room network is Windows 2000 domain – PSCC PDC is PI Server Control system configuration is done thru PLX Server – creates configuration database PLX server stores configuration database and stores/updates an active, real-time database Operator stations access process thru PLX server PI Server Control Room Network Switch ProcessLogix Server Operator Stations 6 ProcessLogix – How it works Communications via ControlNet Controller configuration is downloaded to PLX Controller PLX Controller continuously updates copy of active database at PLX server PLX Controller continuously executes all control logic, alarming, PID loops, indicators, etc. ProcessLogix Server PLX Controller and I/O Cards Controller continues to function, even after loss of communication w/ server 7 ProcessLogix – How it works Plant Area – valves, xmitters PLX Controller and I/O Cards I/O cards are specific to device requirements •4-20 mA input, 4-20 mA output •24 VDC input, 24 VDC output, etc. A pair of wires runs from each device back to the I/O card Typically 8 to 16 devices per I/O card 8 PLX Controller Cabinet PLX controller I/O cards Zener barriers 8 pr. cables from field junction cabinet 2nd I/O chassis 9 Field Junction Cabinet Single pairs from field device 8 pr. Cables to controller cabinet 10 Field Devices – Transmitters Level transmitter Wiring to field junction cabinet Thermocouple head Wiring from transmitter to measuring element Temperature transmitter 11 Field Devices – Transducer Solenoids for 2-position air-actuated ball valves Single pr. cable from field termination cabinet Air lines to ball valves Current to pneumatic transducers Air lines to control valves Wire prs. to solenoids Wire prs. to transducers 12 Field Devices – Regulatory Control Valve Air line from transducer Actuator w/ positioner Control valve Block valves Bypass valve 13 Field Devices – Ball Valve w/ Actuator Air line from solenoid Ball valve body Actuator Process line 14 PI – Plant Information System PI is a process data historization/ data retrieval system WE Network - PIPC - ProcessBook PI server (Steam) is PDC for control room network and is also on WE network PI data are available anywhere on campus network PI Server - OPC Interface Control Room Network Switch ProcessLogix Server - OPC Server PIPC is Excel add-in ProcessBook is graphical tool for viewing process and process data Operator Stations - PIPC - ProcessBook 15 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 16 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 be manually entered – lab data 17