1. Pengantar Pengendalian Proses
Priyatmadi
Jurusan teknik Elektro
FT UGM
Process Control
Priyatmadi

2. PROCESS CONTROL PRINCIPLE
Process control is methods to force process parameter to have specific values.
Objective to maintain the value of some quantity at some desired level regardless of influences.
Process Control
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3. PROCESS TYPE Self-regulating Processes Manual controlled processes
Automatic controlled process
Process Control
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4. Self-regulating Processes
The process outputs are not regulated, its value will easily change.
heat exchanger
cold water in
steam in
hot water out
steam out
Process Control
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5. Manual Control
Process Control
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6. Automatic Control - + Cold water in steam in hot water out 3-15psi
Set point TT
I/P
TIC
4-20 mA
4-20 mA
Plant
Controller
Sensor + -
Set point
Process Control
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7. Process Control Classification
Manual Control
Automatic Control
Feedback Control
Feed forward Control
Arithmetic control
Logic Control
Analog Control
Digital Control
Process Control
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8. Controller Development
Pneumatic controllers
Electronic analog controllers
Supervisory control computers
Distributed Control Systems (DCS)
Fieldbus technology
Process Control
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9. Pneumatic Controllers - Phase I
Introduced in the 1920’s
Installed in the field next to the valve
Use bellows, baffles, and nozzles with an air supply to implement PID action.
Provided automatic control and replaced manual control for many loops
Process Control
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10. Pneumatic Controllers - Phase II
Transmitter type pneumatic controllers began to replace field mounted controllers in the late 1930’s.
Controller located in control room with pneumatic transmission from sensors to control room and back to the valve.
Allowed operators to address a number of controllers from a centralized control room.
Process Control
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11. Pneumatic Controller Installation
Process Control
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12. Electronic Analog Controllers
Became available in the late 1950’s.
Replaced the pneumatic tubing with wires.
Used resistors, capacitors, and transistors based amplifiers to implement PID action.
Outsold pneumatic controllers by 1970.
Allowed for advanced PID control: ratio, feedforward, etc.
Process Control
Priyatmadi

13. Electronic Controller InstallationF 2
Thermocouple
millivolt signal
Transmitter
4-20 ma
Electronic
Analog
Controller
3-15 psig sp
I/P
Air 1
Thermowell
Process Control
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14. Computer Control System
Based upon a mainframe digital computer.
Offered the ability to use data storage and retrieval, alarm functions, and process optimization.
First installed on a refinery in 1959.
Had reliability limitations.
Process Control
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15. Supervisory Control Computer
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16. Distributed Control System- DCS
Introduced in the late 1970’s.
Based upon redundant microprocessors for performing control functions for a part of the plant SUPERIOR RELIABILITY
Less expensive per loop for large plants.
Less expensive to expand.
Facilitates the use of advanced control.
Process Control
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17. DCS Architecture
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18. DCS and Troubleshooting
The data storage and trending capability of a DCS greatly facilitate troubleshooting control problems. That is, the sources of process upsets can many times be tracked down through the process by trending a group of process measurements until the source of the process upset is located.
Process Control
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19. Control Relevant Aspects of a DCS
The most important control aspect of a DCS is the cycle time for controller calls. The shortest cycles times are typically around 0.2 seconds while most loops can be executed every 0.5 to 1.0 seconds. These cycle times affect flow control loops and other fast control loops.
Process Control
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20. Fieldbus Technology
Based upon smart valves, smart sensors and controllers installed in the field.
Uses data highway to replace wires from sensor to DCS and to the control valves.
Less expensive installations and better reliability.
Can mix different sources (vendors) of sensors, transmitters, and control valves.
Now commercially available and should begin to replace DCSs.
Process Control
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21. Fieldbus Architecture
Process Control
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