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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