ISA Boiler Control System Fundamentals

© 2003, ISAES15w (1.0)

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© 2003ISA67 Alexander DriveResearch Triangle Park, NC 27709

© 2003ISA67 Alexander DriveResearch Triangle Park, NC 27709 Version 1.0

ES15w

Introduction toBoiler ControlSystems

© 2003, ISAES15w (1.0)

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Seminar Logistics

• Seminar materials− Downloadable presentation

− Question and Answer session (audio and email)

− Survey

− Earn 1 Professional Development Hour (PDH)

• Seminar length− 60 minute presentation

− Three 10-minute question and answer sessions

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Audio Instructions

• As a participant, you are in a “listen-only”mode.

• You may ask questions via the internet, usingyour keyboard, at any time during thepresentation. However, the presenter maydecide to wait to answer your question untilthe next Q&A Session.

• If you have audio difficulties, press *0.

• If you have visual difficulties, call (866) 493-2825.

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Audio Instructions





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Audio Instructions





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Audio Instructions for Q&A Sessions

• Questions may be asked via your telephone line.

• Press the *1 key on your telephone key-pad.

• If there are no other callers on the line, the operator willannounce your name and affiliation to the audience andthen ask for your question.

• If other participants are asking questions, you will beplaced into a queue until you are first in line.

• While in the queue, you will be in a listen-only mode untilthe operator indicates that your phone has been activated.The operator will announce your name and affiliation andthen ask for your question.

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Introduction of Presenter

• ISA Presenter− Gerald F. Gilman, PE

− Consultant to companies for safety applications anddeveloper of training programs.

− He started consulting after 37 years at Proctor & Gamble asa Control and Information Systems Manager in the SoapSector Engineering Department.

− He was responsible for the control and information systemsat three P&G sites, the coordinator for safety instrumentedsystems and safety standards worldwide, and a keyresource for boiler control systems and boiler start-ups.

− Contact information: [email protected] or (513) 522-4154

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Key Benefits of Seminar

• Understand control systems and instrumentation for boilers

• Understand process dynamics of a boiler and the processcontrol interactions

• Be able to describe− boiler components and their function

− how the systems interact and how to set up the controls

− swell and shrink

• Be able to configure

− Furnace draft

− Drum level feed water control

− fuel air control

− steam temperature

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Boiler Fuels

• Gas

• Oil

• Coal

• Fuel combinations

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SAMA Symbols (Scientific Apparatus Makers Association)

ENCLOSURE SYMBOLSTable 1

Function Symbol

Measuring orReadout

Manual SignalProcessing

Automatic SignalProcessing

Final Controlling

Within a circle use a letter symbol from Table IIWithin other enclosures us a symbol from Table III

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SAMA Symbols (cont’d)

MEASURING/READOUT LETTERSTable II

Process Variable FunctionA = Analysis**C = ConductivityD = DensityF = FlowL = LevelM = MoistureP = PressureS = SpeedT = TemperatureV = ViscosityW = WeightZ = Position

R = RecordingI = IndicatingT = TransmitterRT = Recording TransmitterIT = Indicating Transmitter

FRT

FR

**Self-defining symbols such as O 2, pH, etc., can be used in place of A.

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SAMA Symbols (cont’d)

SIGNAL SIGNALFUNCTION PROCESSING

SYMBOLFUNCTION PROCESSING

SYMBOL

SUMMING ∑ or + INTEGRATE OR TOTALIZE Q

AVERAGING ∑/n HIGH SELECTING

DIFFERENCE ∆ or - LOW SELECTING

PROPORTIONAL K or P HIGH LIMITING

INTEGRAL ∫ or I LOW LIMITING

DERIVATIVE d/dt or D REVERSE PROPORTIONAL -K or -PMULTIPLYING X VELOCITY LIMITING VDIVIDING ÷ BIAS ±ROOT EXTRACTION √ TIME FUNCTION f(t)EXPONENTIAL Xn VARIABLE SIGNAL

GENERATIONA

NON-LINEAR FUNCTION f(x) TRANSFER TTRI-STATE SIGNAL(RAISE, HOLD, LOWER)

b SIGNAL MONITOR H/, H/L, /L

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Simple Feedback ControlPRIMARY VARIABLE

XT

K

A T A

f(x)

SET POINTPROCESS

MANIPULATED VARIABLE

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Feedforward Plus Feedback ControlPRIMARY VARIABLE

XT

YT

SECONDARYVARIABLE

A T A

f(x)


PROCESS

SET POINT

K

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Cascade ControlPRIMARY VARIABLE

XT

ZT

K

K

SET POINTA AT

PROCESS

f(x)


SECONDARYVARIABLE

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Ratio Control

A T A

f(x)


K

RATIO SET

X

YT

UNCONTROLLED VARIABLE

CONTROLLEDVARIABLE

XT

PROCESS

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• If there are no other callers on the line, the operator willannounce your name and affiliation to the audience and thenask for your question.

• If other participants are asking questions, you will be placedinto a queue until you are first in line.

• While in the queue, you will be in a listen-only mode until theoperator indicates that your phone has been activated. Theoperator will announce your name and affiliation and then askfor your question.

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Live Question and Answer Session

• During Q&A, questions may be asked via your telephone line.


• If there are no other callers on the line, the operator will announceyour name and affiliation to the audience and then ask for yourquestion.

• If other participants are asking questions, you will be placed into aqueue until you are first in line.

• While in the queue, you will be in a listen-only mode until theoperator indicates that your phone has been activated. Theoperator will announce your name and affiliation and then ask foryour question.

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Basic Control Functions

• Regardless of thehardware and softwareused certain controlfunctions are required

• These controls are

− Furnace Draft

− Drum Level Feedwater

− Fuel Air

− Steam Temperature

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Boiler Components

COLD AIR

SUPERHEATER

DESUPERHEATER

STEAM DRUMSTEAMFROMSECONDBOILER

STEAMFROMTHIRDBOILER

STEAM TOTHE PROCESSSTEAM HEADER

COLD AIR

FEED WATER

FLUE GASES

AMBIENTAIR

F.D. FANINLETVANES

I.D. FAN INLET DAMPER

TOTALAIR

AIR HEATER

SPRAY WATER FROMFE DWATER PUMP

HOT AIRDAMPER

HOT AIR

PULVERIZEDCOAL WITHPRIMARY AIR

(P.A.)

PULVERIZED

FEEDER

P.A. CONTROLDAMPER

P.A. FAN

FROM OTHERPULVERIZERS

COLDAIRDAMPER

SECONDARYAIR

E

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Block Diagram of Boiler Control

+INPUT OUTPUT

FIRINGRATE

DEMAND

FUEL DEMAND

AIR DEMAND

FEEDWATER CONTROL

STEAM TEMPERATURECONTROL

BOILER

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Furnace Pressure Control

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System Reliability & Availability ISA-77.41

• Field transmitter device redundancy should beprovided to the extent necessary to achieve desiredsystem reliability. The following conditions apply:− When two transmitters are employed, excessive deviation

between the transmitters shall be alarmed and the associatedcontrol loop shall be transferred to manual

− When three transmitters are employed, excessive deviationbetween the transmitters shall be alarmed

• A transmitter select scheme shall be used for controlpurposes

• Furnace pressure shall be measured with threefurnace pressure transmitters, each on a separatemeasurement tap.

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+INPUT OUTPUT

FIRINGRATE

DEMAND

FUEL DEMAND

AIR DEMAND

FEEDWATER CONTROL


BOILER

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Boiler Steam Drum/Swell Shrink

STEAM

STEAM

SATURATED

WATER

WATER

FEEDWATER

WATER-MIXED STEAM BUBBLES

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Single Element Feedwater Control

SET POINTK

T

f(x)

A

A

X

LT PT

f(x)

FINAL CONTROL DEVICE

M/A CONTROL STATION

PRESSURECOMPENSATION

DRUM PRESSUREDRUM LEVEL

∫∆

Typical single-drive control system. For simplicity, redundant transmitters have not beenshown on this typical control drawing. See Figure 2A for ANSI/ISA-5.1-1984 format.

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Two Element Feedwater Control

∆∫

f(x)

K

TA

A

X X

K

LTPT PT FT TE

f(x) f(x) f(x)

FINAL CONTROL DEVICE

M/A CONTROL STATION

SET POINT


TEMPERATUREAND PRESSURECOMPENSATION

LEVEL

PRESSURE

STEAM

TEMPERATUREFLOWDRUM

PRESSURE

Typical single-drive control system. For simplicity, redundant transmitters have not beenshown on this typical control drawing. See Figure 3A for ANSI/ISA-5.1-1984 format.

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Three Element Feedwater Control


f(x)

A

X

PT FT TE

f(x) f(x)

X

LT PT

f(x)

X

FT TE

f(x)

K

K

∆

∆

T A

FINALCONTROLDEVICE

M/A CONTROLSTATION

SET POINT

PRESSURE ANDTEMPERATURECOMPENSATION

STEAM

TEMPERATUREFLOWPRESSURE

Typical single-drive control system. For simplicity, redundanttransmitters have not been shown on this typical control drawing.See Figure 4A for ANSI/ISA-S5.1-1984 format.

LEVEL PRESSURE

DRUM

TEMPERATURECONDENSATION

FLOW TEMPERATURE

FEEDWATER

Typical single-drive control system. For simplicity, redundanttransmitters have not been shown on this typical control drawing. See

Figure 4A for ANSI/ISA-5.1-1984 format.

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+INPUTBOILER

OUTPUT

FEEDWATER CONTROL


FUEL DEMAND

AIR DEMAND

FIRINGRATE

DEMAND

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Firing Single Fuel/Cross Limiting

AIR CONTROL

FT PT FT

A

A T

P I

A T

P I

A T

P I

f(x)

f(x)

Fuel FLOWSTEAM

HEADER PRESSURE AIR FLOW

SP SP

LO SELECT HI SELECTFuel CONTROL

Fuel FeedAIR DAMPER

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Dual Fuel O2 Trim

P I

TA

X

Y

X

X

C

Z YY

Y

Y

X X

Y

BSP

A X

P I

TA

X

P I

TA

X

P I

TA

X

X

P I

A T

P I

A T

A

GAS FLOW0-90,000 SCFH

FT FT

OIL FLOW0-10,000 PPH

0-30” WCFUEL

SUMMERYX

FUELCONTROL

SP

STEAM HEADERPRESSURE

PT0-850 PSI

PVSP SP

GAS CONTROL OIL CONTROL

LOW SELECT HIGH SELECT

GAS VALVE OIL VALVEFAN DAMPER

AIR CONTROL

PV

SUBMASTER

HEADERPRESSURECONTROL

AIR FLOWCHARACT...

f(x)

AIR FLOW

FT AT0-5” WC

BOILER O2

O2 10%

f(x)

O2 TRIMCONTROL

SP

STEAMFLOW

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Excess Air vs. Boiler LoadEXCESS AIR

(% o2)

BOILER LOAD(%)

0 50 100

5

4

3

2

1

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Non Linear Flow

0 10 20 30 40 50 60 70 80 90 100

0 1 4 9 16 25 36 49 64 81 100

Flow in %

0

10

20

30

40

50

60

70

80

90

100

0 14

916

25

36

49

64

81

100

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11

Series1

Series2

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Characterization

0 10 20 30 40 50 60 7 0 80 O U T

0 7 .5 15 22 .5 30 37 .5 45 52 .5 60 IN

0

10

20

30

40

50

60

70

80

0

7 .5

15

22 .5

30

37 .5

45

52 .5

60

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6 7 8 9

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+INPUTBOILER

OUTPUT

FIRINGRATE

DEMAND

FUEL DEMAND

AIR DEMAND

FEEDWATER CONTROL


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Water Side Control MechanismsDESUPERHEATER

SUPER-HEATER

SECTIONS

PURE WATER SPRAYED INTO THE SUPERHEATED STEAMVAPORIZES; DEGREE OF SUPERHEAT IS REDUCED HEAT

OF VAPORIZATION.

From Power magazine SpecialReport, “Steam Generation,”by R.J. Bender, Associate Ed.McGraw Hill, NY

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Typical Single Element Superheat Control

OPENCLOSE

K ∫

f(x)

TA

A

T T

A

A A

TT

SPRAY CONTROL VALVE SPRAY CONTROL VALVE

SPRAYINTERLOCK

SET POINT

0%

0%

100%

M / A CONTROLSTATION

FINAL STEAMTEMPERATURE

∆

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Typical Two-Element Superheat Control

OpenClose

Final SteamTemperature

FeedforwardCalculation

f(x)

TA

T T

A

A A

Spray Control Valve Spray Block Valve

SprayInterlock

0%

0%

100%

M / A ControlStation

K

∆∫

A

TT

Setpoint

ΣLoadIndex(es)

TransientCorrection

Signal(s)

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Typical Three-Element Superheat Control

Note: 1. Attemperator Outlet Temperature or Spray Flow

OpenClose

Final SteamTemperature

TransmitterFeedback (Note 1)

FeedforwardCalculation

f(x)

TA

T T

A

A A

Spray Control Valve Spray Block Valve

SprayInterlock

0%

0%

100%

M / A ControlStation

K

K

∆

∆

∫

∫

A

TTTT/FT

Set Point

ΣLoadIndex(es)

TransientCorrection

Signal(s)

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Related Resources from ISA

• Complete, hands-on course on this topicavailable through ISA Training Institute onlineat www.isa.org/training− Boiler Control Systems Engineering (ES15)

− Burner Management Systems Engineering (ES16)

− Available any time as on-site training

• Books, software, videotapes, interactivemultimedia

• Standards, journals, membership services

Phone: (919) 549-8411E-mail Address: [email protected]

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Additional ISA Resource Materials

• Fossil fuel power plant standards− Boiler Combustion Control ANSI/ISA-77.41-1992

− Feedwater Control System ANSI/ISA-77.42.01-1999

− Plant Demand Development ANSI/ISA-77.43-1994

− Steam Temperature Control System ANSI/ISA-77.44-1995

− Fossil Fuel Power Plant Instrument Piping InstallationANSI/ISA-77.70-1994

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Seminar Survey

• Web-based Seminar Surveys are tools to help ISAmaintain the quality of our training programs.

• Please complete the following four slides of thesurvey and fax to ISA when it is complete.

Please fax completed survey pages to (919) 549-8288.

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Seminar Survey (cont’d)

Date of Web-Seminar ___________________________Please mark only one circle for each question.Scale Definition: P-Poor; F-Fair; G-Good; VG-Very Good; E-Excellent

P F G VG E1. Seminar objectives were clear and attainable with the allotted time.2. Pre-program seminar description was accurate.3. How was registration process?4. How was the audio quality?


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Name of Presenter: _____________________ P F G VG E

5. Demonstrated practical knowledge about the subject.6. Provided clear answers to questions/comments.

7. How many people listened at your site? 1-5 6-10 11-15 16-20 21+


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8. Would you participate in another virtual seminar? Yes No9. Did the web component add to the value of the virtual seminar? Yes No10. Did the seminar satisfy your professional objectives? Yes No

11. How did you hear about this seminar? _____________________________________________ _____________________________________________



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12. List other topics you would like to view as a web seminar, along with your overall impression of the program. ________________________________________________ ________________________________________________

Name of Participant (optional) ____________________ Name of Your Company __________________________



ISA Boiler Control System Fundamentals

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