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

Process Control Priyatmadi Overall Course Objectives Develop the skills necessary to function as an industrial process control engineer. –Skills Tuning loops Control loop design Control loop troubleshooting Command of the terminology –Fundamental understanding Process dynamics Feedback control

Process Control Priyatmadi Control Relevant Aspects of Control Loop Hardware Necessary for control loop troubleshooting: –To determine if each subsystem (control computer, actuator system, and sensor system) is functioning properly –To understand the proper design and operation of all the components that make-up each of the subsystems of a control loop

Process Control Priyatmadi Process Control Classification Manual Control Automatic Control Feedback Control Feed forward Control Analog Control Digital Control

Process Control Priyatmadi Manual Control

Process Control Priyatmadi Automatic Control TT TIC I/P 4-20 mA 3-15psi Set point Cold water in hot water out steam in Plant Controller Sensor + - Set point e(t) m(t) c(t)

Process Control Priyatmadi Control Diagram of a Typical Control Loop

Process Control Priyatmadi Components and Signals of a Typical Control Loop

Process Control Priyatmadi Controller Development Pneumatic controllers Electronic analog controllers Supervisory control computers Distributed Control Systems (DCS) Fieldbus technology

Process Control Priyatmadi 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 Priyatmadi 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 Priyatmadi Pneumatic Controller Installation

Process Control Priyatmadi 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 Allowed for advanced PID control: ratio, feedforward, etc.

Process Control Priyatmadi Electronic Controller Installation T F 2 T 2 Thermocouple millivolt signal Transmitter 4-20 ma Electronic Analog Controller 3-15 psig 4-20 ma T sp I/P Air F 1 T 1 Thermowell

Process Control Priyatmadi 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 Had reliability limitations.

Process Control Priyatmadi Supervisory Control Computer

Process Control Priyatmadi 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 Priyatmadi DCS Architecture

Process Control Priyatmadi 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 Priyatmadi 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 Priyatmadi 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 Priyatmadi Fieldbus Architecture