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Process Control > Intro > Flashcards

Intro Flashcards

1
Q

What is Instrumentation

A

(according to ISA) A
collection of instruments or their application for
the purpose of observation, monitoring, and
control.

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2
Q

What is Control

A

To regulate, to have power, to rule

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3
Q

Scope of Instrumentation and Control

A 
1. Computers, IT, Communications,
Telecommunications, Data Handling, Telemetry
2. Aerospace/Avionics
3. Marine Science/Marine Biology
4. Metrology
5. Automation – Mechanical
6. Automation – Process
7. Analytical
8. Bio-medical
9. Cryogenics
10.Nuclear Instrumentation
11.Power Instrumentation
12.Others/unclassified
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4
Q

Process Automation covers the measurement and control of what process variables?

A

pressure, temperature,
flow, level, viscosity, humidity, specific gravity,
ph, thickness, weight, conductivity, oxygen level,
etc

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5
Q

In order to monitor a process

A

a characteristic
or parameter of the process must be
measured.

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6
Q

The accuracy and repeatability of the

measurement

A

is a must before the controller

can do its job of controlling the process.

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7
Q

What is Process Control

A

a technique of balancing supply and demand
over a period of time at a predetermined level
of operation called the Set Point (SP).

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8
Q

How to attain Process Control

A

the controller compares the
measured variable (Process Variable) with the
set point and then makes the adjustment in
the final control element based on the
difference between the set point and the
process variable

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9
Q

What is an error signal?

A

difference between the

set point and the process variable.

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10
Q

What is the objective of process control

A

Its objective is to make e equal to zero

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11
Q

Why is process control important?

A

high quality products and safety

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12
Q

Why is process control necessary?

A

To minimize/eliminate the effect of

disturbances

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13
Q

How is control design documented?

A

Process and Instrumentation Diagrams (P and

ID’s provide the documentation.

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14
Q

Why Process and Instrumentation Diagrams are used?

A
  • system is too complex to describe in text.

- standard symbols must be used.

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15
Q

Seven Control Objectives:

A
  1. Safety
  2. Environmental Protection
  3. Equipment Protection
  4. Smooth Operation
  5. Product Quality
  6. Profit
  7. Monitoring and Diagnosis
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16
Q

What is a flash separator

or vapor–liquid separator?

A

is a
device used in several industrial
applications to separate a
vapor–liquid mixture.

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17
Q

In a flash separator, how is SAFETY / ensured?

A

High pressure drum is dangerous, therefore a pressure controller is used

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18
Q

In a flash separator, how is ENVIRONMENTAL PROTECTION ensured?

A

Hydrocarbons are never released to the atmosphere. Excess hydrocarbons are burned

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19
Q

In a flash separator, how is EQUIPMENT PROTECTION ensured?

A

No flow could damage the pump

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20
Q

In a flash separator, how is SMOOTH OPERATION PRODUCTION RATE ensured?

A

Flow Control is used to make a continuous feed to the pressure tank

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21
Q

In a flash separator, how is PRODUCT QUALITY ensured?

A

Adjust L.Key by adjusting the heating

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22
Q

In a flash separator, how is HIGH PROFIT ensured?

A

Use the least costly heating

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23
Q

In a flash separator, how is Monitoring and Diagnostic ensured?

A

Calculate and plot key parameters

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24
Q

What happens when the seven control objectives are not achieved

A

It will lead to UNPROFITABLE or UNSAFE operation

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25
Q

When we control a process,

A

we reduce the
variability of key variables to achieve the seven
control objectives.

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26
Q

Variability is moved from?

A

controlled variable to

the manipulated variable.

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27
Q

What is process performance

A

efficiency, yield, production rate, etc. It measures performance for a control objective

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28
Q

Note when calculating the process performance

A

Use the distribution not the average value of the key varable

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29
Q

AAH Co

A

Analyzer Alarm High Carbon Monixide

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30
Q

FE

A

Flow Element (for example, orifice)

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31
Q

FIC

A

Flow Indicating Controller

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32
Q

FO

A

Flow Orifice (Restricting Orifice used in a pump bypass loop to maintain a minimum flow through the pump)

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33
Q

FSH

A

Flow Switch High

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34
Q

HC

A

Hand Control (manual Control)

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35
Q

LG

A

Level Glass or Gage Glass

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36
Q

LR

A

Level Recorder (maintains record of level over several days or months)

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37
Q

PDC

A

Pressure Differential Controller

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38
Q

PP

A

Pressure Point (test point)

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39
Q

PRC

A

Pressure Recorder and Controller

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40
Q

PSD

A

Pressure Safety Disc (Rupture disc which fails at high pressure and or temperature to protect vessel from damage

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41
Q

PSV

A

Pressure Safety Valve

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42
Q

PV

A

Pressure Valve (located on the pipeline)

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43
Q

SIC

A

Speed Indicating Controller

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44
Q

SSH

A

Speed Switch High

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45
Q

SSHH

A

Speed Switch High High

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46
Q

TIC

A

Temperature Indicating Controller

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47
Q

TW

A

Temperature Well (used to protect temperature measuring element from harsh environment of a process)

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48
Q

Instrument supply or connection to process

A

_________________________

49
Q

Undefined Signal

A

______/_________/_________

50
Q

Pneumatic(air) signal

A

______//________//_________

51
Q

Electric Signal

A

______///________///_________
or
————————————————–

52
Q

Hydraulic Signal

A

________L_______L_________

53
Q

Capillary Tube or filled system

A

_________X_______X________

54
Q

Electromagnetic or sonic signal (guided)

A

_________~________~________

55
Q

Electromagnetic or sonic signal (not guided)

A

~ ~

56
Q

Software or Data Link

A

_______O__________O_______

57
Q

Mechanical Link

A

_______(.)__________(.)________

58
Q

Pneumatic Binary signal (on-off)

A

______//\__________//\_______

59
Q

Electric Binary Signal (on-off)

A

______///\__________///\_______
or
————-———————–-—————–

60
Q

Instrument Supply: AS

A

Air Supply 7000 kPa

61
Q

Instrument Supply: ES

A

electrical supply 24v dc

62
Q

Instrument Supply : SS

A

Steam Supply 350 kPa

63
Q

Instrument Supply: WS

A

Water Supply: 350 kPa

64
Q

Instrument Supply: NS

A

Nitrogen Supply: 210 kPa

65
Q

Pneumatic Signal is typically in what range?

A

20 to 100 kPa oe 3-15 psig

66
Q

pneumatic signal medium

A

air, natural gas or nitrogen

67
Q

electrical signal is typically in what range?

A

4 to 20 mA

68
Q

Common Hydraulic medium

A

oil filled system

69
Q

What is a capillary tube

A

sensing line which connects the process to the instrument.

70
Q

What is a capillary tube filled with?

A

filled with inert material (silicone oil)

71
Q

What is the use of silicone oil in capillary tubes?

A

To protect the instrument from the deleterious effects of the process fluid

72
Q

What are sonic signals

A

frequency signals, guided in a co-axial cable or not guided as in radio telemetry or satellite transmission

73
Q

What is included in sonic signals?

A

it includes nuclear radiation and light

74
Q

What does DCS mean?

A

Distributed Control System

75
Q

Controller Properties

A

Good Performance - feedback measures
Wide Applicability - adjustable parameters
Timely Calculations - avoid convergence loops
Switch to/from manual - bumplessly
extensible - enhanced easily

76
Q

Time Domain and Transfer Function and Final Value after Disturbance of Proportional Controller

A 
Mv(t) = Kc*e(t) + Ip (bias constant)
Gc(s) = MV(s)/E(s) = Kc
Cv(t) = deltaD*Kd/(1+Kc*Kp)
77
Q

Time Domain and Transfer Function and Final Value after Disturbance of Integral Controller

A 
Mv(t) = Kc/Ti  integral of e(t) from 0 to infinity + Ii(bias constant)
Gc(s) = MV(s)/E(s) = Kc*Ti * 1/s
Cv(t) = 0
78
Q

Time Domain and Transfer Function and Final Value after Disturbance of Derivative Controller

A 
Mv(t) = Kc*Td  d(e(t))/dt+ Id(bias constant)
Gc(s) = MV(s)/E(s) = Kc*Td * s
Cv(t) = deltaD*Kd
79
Q

Integral mode is also known as

A

persistent mode

80
Q

Derivative mode is also known as

A

predictive mode

81
Q

What is open loop test

A

A test of process characteristics with the loop controller in manual mode. The feedback loop has been “opened” and is no longer a complete loop

82
Q

Three major classification of process response

A

Self Regulating
Integrating
Runaway

83
Q

What is self regulating response?

A

responds to a step change in the final control element’s status by settling to a new, stable value

84
Q

What is an integrating response?

A

responds by ramping either up or down at a rate proportional to the magnitude of the final control element’s step change

85
Q

What is a runaway response?

A

by ramping either up or down at a rate that increasing over time, headed toward complete instability without some form of corrective action from the controller

86
Q

Self regulating processes are characterized by?

A

their natural ability to stabilize at a new process variable value following changes in the control element value or loads

87
Q

Self regulating processes absolutely require what controller?

A

it requires integral controller action to eliminate offset between process variable and setpoint

88
Q

Faster integral controller action results in?

A

quicker elimination of offset

89
Q

The amount of integral controller action tolerable in a self-regulating process depends on?

A

the degree of time lag in the system.

90
Q

Too much integral action will result in?

A

oscillation, just like too much proportional control action

91
Q

Example of integrating response?

A

filling a water tank and the water level acting as the process variable

92
Q

What is mass balance?

A

Process variable (pressure, level) will remain constant if and only if incoming mass = outgoing mass

93
Q

What is energy balance?

A

Process variable (temperature, speed) will remain constant if and only if incoming energy = outgoing energy

94
Q

common examples of integrating processes

A

liquid level control, gas pressure control
storage bin control (conveyor belt)
temperature control (energy balance)
speed control (energy balance)

95
Q

Integrating processes are characterized by?

A

ramping of the process variable in response to a step-change in the control element value or load

96
Q

The integration occurs as a result of either _________ or ______________ in and out of the process

A

Mass flow imbalance or energy flow imbalance

97
Q

integral controller action guarantees __________ in a purely integrating process

A

setpoint overshoot

98
Q

some integral controller action will be required in integrating processes to _____________

A

compensate for load changes

99
Q

The amount of proportional controller action tolerable in an integrating process depends on?

A

the degree of time lag and process noise in the system

100
Q

Too much proportional action will result in _____ or ________

A

oscillation (time lags), erratic control element motion (noise)

101
Q

Runaway processes are characterized by ?

A

exponential ramping of the process variable in response to a step change in the control element value or load(s)

102
Q

what causes runaway processes?

A

it is a result of some form of positive feedback happening inside the process

103
Q

Runaway processes cannot be controlled with proportional or integral controller action alone. What does it require?

A

it always requires derivative action for stability

104
Q

some integral controller action will be required in runaway processes to?

A

compensate for load changes

105
Q

Example of runaway process?

A

nuclear fission reaction when mother atoms split to daughter atoms to continue the nuclear reaction; pendulum in a cart

106
Q

how can runaway processes be self regulating

A

if sufficient feedback is naturally introduces, as in the case with water moderated fission reactors

107
Q

Example of a lag time?

A

inserting a square wave in an rc filter.

108
Q

gravity drained level control process exhibits similar response to?

A

a sudden change in control valve position

109
Q

What is stated in newton’s cooling law?

A

Higher temperature results to faster rate of cooling

110
Q

what is one time constant?

A

the amount of time required for the variable to change 63.2 percent of the way from its starting point to its terminal value

111
Q

How is lag time defined?

A

the difference in time between when the process variable ramps to a certain value and when it would have ramped to that same value were it not for the existence of the first order lag in the system

112
Q

example of lag time involving heating?

A

heating a potato wrapped in aluminum foil. A lag time exist between the temperature of the element, temperature of the oven and temperature of the potato

113
Q

What is dead time?

A

it refers to a period of time during which a change in manipulated variable produces no effect whatsoever in the process variable

114
Q

Types of lag in a system

A

first-order lag-time, multiple order lag time, pure dead -time response

115
Q

Dead time is also referred to as?

A

transport delay,

116
Q

why is dead time also called transport delay?

A

because the mechanism of dead time is often a time delay caused by the transportation of material at finite speed across some distance

117
Q

What is the difference between a lag time and dead time

A

a lag time function has a phase delay and a corresponding different gain. Dead time has only phase delay with unity response

118
Q

What is the difference between first-order, second-order and higher order response?

A

The higher the order of the response, the longer the higher the phase delay

119
Q

What is a hysteresis?

A

There is a lack of responsiveness to a change in direction.

Process Control (1 decks)

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