Professor robert l heider pe
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Professor Robert L. Heider, PE. Adjunct Professor, ChE, Washington University ~45 years experience doing “Process Control” Professor for the DPCL, ChE433. Lecture Includes:. What is "process control"? Hardware and Software (firmware)

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Professor robert l heider pe

Professor Robert L. Heider, PE

Adjunct Professor, ChE, Washington University

~45 years experience doing “Process Control”

Professor for the DPCL, ChE433


Lecture includes

Lecture Includes:

  • What is "process control"? Hardware and Software (firmware)

  • Process measurement instruments; transmitters, transducers, sensor elements, control valves

    • Flow

    • Level

    • Pressure

    • Temperature

    • pH

  • Comments on topics in text


Process control

Process Control

  • Macro vs. micro and nano

  • Process Control views the process in macro terms

  • Concerned with interactions of all process variables rather than exact solution of the details of one variable

  • Can use simulations but does not necessarily require it


Just what is process control

Just what is “Process Control?”

“Operating a processing plant or facility such

that the product quality and production rate

specifications are met in a safe and

reliable manor.”

Involves both hardware and software or

firmware functioning together.


Professor robert l heider pe

Process Control is a general term for the whole plant.Control Loop is the term used to define a single process parameter.

  • Measurement

  • Controller

  • Process Manipulation

  • Connections or communication between them


Process control spc

Process Control - SPC

  • Statistical Process Control (SPC) is a technique where the process output or PV is monitored in order to detect an out of control process.

  • Frequently done with Control Charts

  • More processes are batch rather than continuous, discrete batches or things properties are controlled through SPC


Process control spc1

Process Control - SPC

  • Shewhart control chart, X-BAR R chart used to detect out of control process

  • CUSUM and EWMA Charts

  • SPC does not dictate how much to move or change the process, only that it is out of control

  • Run-by-Run control is frequently used in semiconductor manufacturing


Measurement

Measurement

  • Devices that convert a physical or chemical plant condition to a usable signal.


Process manipulation moves or changes the process

Process ManipulationMoves or changes the process

  • Control Valve

  • Adjustable Speed Drive


Controller

Controller

  • The device or software (firmware) that moves the process to keep the measurement where we want it.


Process instrumentation diagram feedback control basic format

CONTROLLER

Temperature

TE

Element

Temp.

101

TC

Set

101

Point

Temperature

TT

Transmitter

101

TT

TRANSMITTER

101

(line in middle indicates

Temperature

TC

remote control)

Controller

101

FY

ACTUATOR

101

TE

SENSOR

Flow

101

FE

Element

101

Cooling

Manual

Water

Valve

(automatic valve)

Pneumatic Valve

Electrical Signal (4-20 mA)

Pneumatic Signal (3-15 psig)

(arrow indicates flow/signal direction)

Material Flow Line

Process Instrumentation Diagram: Feedback Control – Basic Format

Current to pneumatic

(I/P) converter

AFC

Valve failure

position chosen

for safety and

operability

Often the sensor is integrated into the transmitter and the I/P converter is integrated into a

position controller or “valve positioner” on the actuator that is also not shown on the P&ID.


Process instrumentation diagrams standard control instrumentation symbols

Process Instrumentation Diagrams:Standard Control Instrumentation Symbols

Preceded by area or plant number

H

L

nnn

# that uniquely identifies instrument

Low Alarm


Lecture topics

Lecture Topics

  • Terminology

  • Instruments

    • Temperature

    • Pressure, level, flow

  • Control Valves


Professor robert l heider pe

  • Transducer – Element; Latin word

    From Latin trānsdūcere, to transfer : trāns-, trans- + dūcere, to lead

    A device that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer

    Also called an “Element”

  • Transmitter

    A transducer which responds to a measured variable by means of a sensing element, and converts it to a standardized transmission signal which is a function only of the measured variable.


Discussion items

Discussion Items

  • Pressure Flow

  • Level

  • Control Valves

  • Temperature Instrumentation


Text comments chapter 9

Text Comments, Chapter 9

Output final element linearity – usually is not, consider:

SCR Silicon Controlled Rectifier – AC power phase control


Scr phase controlled load results in non linear output

SCR phase controlled load results in non-linear output


Instrument selection

Instrument Selection

  • Page 209 of Seborg text

  • Point 4 MOC, Instruments require better service requirements than pipe or vessel MOC, thin diaphragms, etc

  • Add point 9, International Codes and Standards as well as special instructions for service requirements

    • Oxygen cleaning

    • Nuclear service


Manufacture support

Manufacture Support

  • Most major companies now rely on instrument and control system manufactures for their technical support.

  • Users groups now substitute for technical societies

ABB

Siemens


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