Process Control and Data

clashjudiciousΗλεκτρονική - Συσκευές

8 Νοε 2013 (πριν από 4 χρόνια και 1 μήνα)

82 εμφανίσεις

1

Process Control and Data
Acquisition Systems

CM4120

Chemical Plant Operations

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


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 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

5

Rockwell Automation ProcessLogix DCS
and OSISoft PI in PSCC

WE Network

PI Server

Control Room

Network Switch

Operator Stations

ProcessLogix
Server

PLX Controller

and I/O Cards

Plant Area


valves, xmitters


PI is process data management system


“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

6




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

ProcessLogix


How it works

Control Room

Network Switch

Operator Stations

ProcessLogix
Server

PI Server

7

ProcessLogix


How it works

ProcessLogix
Server

PLX Controller

and I/O Cards


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.


Controller continues to function, even
after loss of communication w/ server

8

ProcessLogix


How it works

PLX Controller

and 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.


A pair of wires runs from each device back to the I/O card


Typically 8 to 16 devices per I/O card

9

PLX Controller Cabinet

PLX controller

8 pr. cables from
field junction cabinet

Zener barriers

I/O cards

2
nd

I/O chassis

10

Field Junction Cabinet

Single pairs from
field device

8 pr. Cables to
controller cabinet

11

Field Devices


Transmitters

Wiring to field
junction cabinet

Thermocouple head

Temperature
transmitter

Wiring from
transmitter to
measuring element

Level transmitter

12

Field Devices


Transducer

Wire prs. to transducers

Current to pneumatic
transducers

Air lines to
control valves

Single pr. cable
from field
termination cabinet

Solenoids for 2
-
position
air
-
actuated ball valves

Air lines to
ball valves

Wire prs. to solenoids

13

Field Devices


Regulatory Control Valve

Air line from transducer

Actuator w/ positioner

Control valve

Block valves

Bypass valve

14

Field Devices


Ball Valve w/ Actuator

Air line from
solenoid

Actuator

Ball valve body

Process line

15




PI is a process data historization/
data retrieval system


PI server (Steam) is PDC for
control room 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


Plant Information System

PI Server

-

OPC Interface

Control Room

Network Switch

Operator Stations

-

PIPC

-

ProcessBook

ProcessLogix


Server

-

OPC Server

WE Network

-

PIPC

-

ProcessBook

16

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


17

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