1 process control and data acquisition systems cm4120 chemical plant operations january 2006
TRANSCRIPT
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Process Control and Data Acquisition Systems
CM4120
Chemical Plant Operations
January 2006
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Outline
Types of Control Systems Control System Architecture for the PSCC Process Instrumentation Connections to
Control System Data Acquisition System Data Retrieval
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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
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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
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Safety Instrumented Systems (SIS) Architecture
An over-ride control system that takes the process to a safe state when predetermined conditions occur
Commonly 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 physically separated from, process control systems
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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
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PSCC Control System Architecture
PSCC uses:
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
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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
DeltaV ProPlus Station
Pilot Plants – valves, xmitters
mtu.edu Network
PI Server
PSCCPSCCRouterRouter
PSCC_DeltaVPSCC_DeltaVRedundant HubRedundant Hub
Professional WorkStationsMD Controller
and I/O Cards
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Emerson Process Management DeltaV and OSISoft PI in PSCC – Networking
Business systems need access to data from control systems and production areas
PSCC_DeltaV is a secure Control Network (green)
Plant Network is an invisible local network for plant operations (red)
Plant data is available to the outside thru alias “steam.we.mtu.edu”
DeltaV ProPlus Station
mtu.edu Network
PI Servermtu-PI
Plant Network RouterPlant Network Routersteam.we.mtu.edusteam.we.mtu.edu
PSCC_DeltaVPSCC_DeltaVRedundant HubRedundant Hub
Professional WorkStationsMD Controller
and I/O Cards
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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
DeltaV System – How it works
ProPlus station stores configuration and archives data, displays information
Operator stations archive data, display information
Operator WorkStations
PSCC_DeltaVPSCC_DeltaVRedundant HubRedundant Hub
ProPlus Station
MD Controller
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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.
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MD Controller I/O – How it works
MD Controllerand 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
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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
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Input-type Field Devices – Transmitters
Wiring to field junction cabinet
RTD or T/C head
Temperature transmitter
Wiring from transmitter to temp measuring element
Level transmitter
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Field Junction Cabinet
Single pairs from field devices
8 pr. Cables to controller cabinet
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MD Controller Cabinet
MD controller
8 pr. cables from field junction cabinet
Power-limiting Zener barriers
I/O cards
2nd I/O chassis
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Output-type Field Devices – Transducer
Wire prs. to transducers
Current to pneumatic transducers
Air lines to control valves
8-pr. cable from field termination cabinet
Solenoids for 2-position air-actuated ball valves
Air lines to ball valves
Wire prs. to solenoids
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Output-type Field Devices – Regulatory Control Valve
Air line from transducer
Actuator w/ positioner
Control valve
Block valves
Bypass valve
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Output-type Field Devices – Ball Valve w/ Actuator
Air line from solenoid
Actuator
Ball valve body
Process line
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DeltaV & Foundation Fieldbus
(4) mass flows, (4) densities, (4) RTD temps
(3) 8-multiplexed RTD temps
(2) temp-only transmitters
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Data Acquisition and Process Management System
OSIsoft PI system
ProcessBook
DataLink
Batch Management, SPC, Performance Equations, etc.
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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 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
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PI is a process data historization and data retrieval system
PI server (mtu-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 – Plant Information System
PI ServerPI-to-PI Interface
PSCC_DeltaVPSCC_DeltaVhubhub
Operator Stations-Excel- PIPC- ProcessBook
DeltaV PI Server
to MTU’snetwork
RouterRoutersteam.we.mtu.edusteam.we.mtu.edu
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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