BOILER CONTROL SYSTEMS THEORY OF OPERATION MANUAL(u .
RD-R124 868UNCLASSIFIEDBOILER CONTROL SYSTEMS THEORY OF OPERATION MANUAL(u)ULTRASYSTENS INC IRVINE CR FEB 83 NCEL-CR-83.SI]U62474-81-C-93B8F/G 13/112N
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CR 83.013fNAVAL4,EECIVIL ENGINEERING LABORATORYPort Hueneme, CaliforniaSponsored byNavy Energy and Natural Resources R&DOffice, Washington, DCNaval Facilities Engineering CommandAlexandria, VirginiaBOILER CONTROL SYSTEMS THEORY OF OPERATION MANUALFebruary 1983An Investigation Conducted byULTRASYSTEMS, INC.2400 Michelson DriveIrvine, CaliforniaN62474-81 -C-9388EC.1.J.Approved for public release; distribution unlimitedC.3o0,23088
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UnclassifiedSECURITY CLASSIFICATION OF TIlS PAGE flh-Do. Entered)REPORT DOCUMENTATION PAGEBEFORE COPEIGFORM2. GOVT ACCESSION NO. J. RECIPIENT' CATALOG NUIMBER1REPO0T NUMERCR 83.0134.zS.TITLE (and S.beteft)TYPE oF RE1PORT a PERIOD COVEREDBoiler Control Systems Theory ofFin82Operation Manual6. PERFORMING7.8.AUTI4OR(8JUltrasystems, Inc.9.10.NC.AREAULTRSYSTMS,MONITORING AGEN4CY NAME II AOORESS(of diftec.I.I.0. C orliffict12. REPORT OATEFebruary 1983NUNBER DO PAGESIunmCA9031.1e)Navy Energy and Natural Resources R&DOffice, CNM , Washington, DC 20360ineering Commnandi EngNaa2TTMENTPROGRAM ELEMENT. PROJECT.4 WORK UNIT. NUMBERSZ02-14B2400 Michelson DriveIrvine, CA 92715I I. CONTROLLING OFFICE NAME AND ADDRESSNaval Civil Engineering LaboratoryPortHuenmeCA9043136IS. OSTRISTIONCONTRACT OR GRANT NUMUERI.N62474-81-C-9388PERFORMING ORGANIZATION NAME ANO ADDRESS14ORG. REPORT NMEIS. SECURITYCLASS.(of IS npq)nlssfeUnlssfeSHDL(.f Ind. R*0ped)Approved for public release; distribution unlimited17. DISTRIBUTION STATEMENT (of theo011IICC"htaredIn I.lock 20. it iEf I"Ot froIS.SUPPLEMENTARY19. KEYWSORDS (ContnROPeWI)NOTESo009 mwrsw.de 01-roa.a.d.WIi .Attb oc110konw)Automatic control, boiler control, combustion control20.AGSTR ACT (ContiI.an@,eWoo*IdeIt ne.cessary aIINdo*.Iror block n.Mwb.)Report reviews-4the fundamentals of combustion, safety, andfeedwator control systems coimmonly used on small industrialboileri j''Report is educatiionali material for boiler operationand maintenance personnel.\DOA71473EGITION OF INOV55IS OUSOLE[TEUnclassifiedSECURITY CLASSIFICATIONOF TNIS PAGE (Wk-in DOI* ErO)
TABLE OF CONTENTSPage1.0S2.0*2.2. . .**.1-1General .2-1Burner Control. .2-12.3Feedwater Control.2.4Flame Safety.3.0BASIC CONTROL THEORY .3.2Open-Loop Control3.3Closed-Loop Control .3.4Control Signal Functions.3.5Proportional Control*3.6. . . . . . . .2-32-6. .3-13-2.3-2.3-3.3-4. .Integral Control. 3-63.7Derivative Control.3-6*4.0BURNER CONTROL SYSTEMS . 4-1*4.1General.4.24-1Parallel Positioning Control Systems. 4-1Jackshaft System .-4.2.1.4-2*4.2.3Pneumatic Parallel Positioning System.4Electric Parallel Positioning System. 4-5*4.3Series Positioning Control Systems .-4.2.24.3.14.3.24.BACKGROUND. 2-12.1-.INTRODUCTION. .4-6Pneumatic Series Positioning System. 4-7Electric Series Positioning System .
PageMetering Control Systems.,4.5Oxygen Trim.4-94.6Cross-Limiting Control .4-115.0FEEDWATER CONTROL SYSTEMS . .5.2Single-Element Feedwater Control.5-15.3Two-Element Feedwater Control .5-35.4Three-Element Feedwater Control. 5-45.5Mechanical Feedwater Regulator .6.0FLAME SAFETY SYSTEMS .6.2SatU.6.3Normal Operation .7.0CONTROL SYSTEM COMPONENTS7 .1Burner Controls .7 .1.2Manual Auto Station. . . . . . . .Ai r/Fuel Ratio Relay.7.1.3Master Pressure Controller .7 .2Feedwater Controls .Feedwater Controller.7-77.2.2Mechanical Feedwater Regulator.7-107.2.3Drum Level Transmitter .7.2.4Flow Transmitter.7.3Flame Safety Systems. .7.3. 1Flame Scanners. .7.4Drive Mechanisms*.7.1.1*7.2.1*4-84.4. . . . .5-15-6.6-1.6-2. .THEORY OF OPERATION. 7-1-. .7-5.7-7.7-12. .7-17-17-3. .Vi. .6-4. .7-14.7-16. .7-16. .7-17
Page7.4.1Pneumatic Control Drive . 7-17Electric Control Drive . 7-187.4.27.4.37.4.5Pneumatic Vaive Actuator . 7-19Electric Valve Actuator7-217.Hydraulic Valve Actuator . 7-237.5Recording Devices .7.5.1Circular and Strip Chart Recorders .7.4.4APPENDIX ASIGNAL PROCESSING FUNCTIONSAccession ForNTISGRA&IPTIC TAB*Jus-t ific nt i .By .Av:Co'eSoovii. . 7-247-24
LIST OF FIGURESFigure Number3-1Figure DescriptionBlock Diagram - Open-Loop Control Mode3-2Block Diagram - Closed-Loop Control Mode3-3Fuel Valve Opening for Various Pressure Deviations in aProportional Control System3-4Response of Steam Pressure to Step Increase of Load ina Proportional Control System3-5Response of Steam Pressure to Step Increase of Load ina Proportional-Plus-Integral-Control ve Action4-1Block Diagram4-2Jackshaft Burner Control System4-3Adjustable Jackshaft Cam Mechanism4-4Functional Schematic Diagram Jackshaft System4-5Parallel Positioning Control System (Pneumatic)4-6Functional Schematic Diagram Parallel Positioning-Simple Parallel Positioning SystemSystem (Pneumatic)4-7Parallel Positioning Control System4-8Functional Schematic Diagram Parallel Positioning*System (Electric)4-9Block Diagram-Simple Series Positioning Control System4-10Series Positioning Control System (Fuel Leading Air)4-11Series Positioning Control System (Air Leading Fuel)4-12Functional Schematic Diagram Series Positioning System(Pneumatic) Fuel Leading Airviii,r/e."
Figure Number4-13Figure DescriptionFunctional Schematic Diagram Series PositioningSystem (Pneumatic) Air Leading Fuel4-14Functional Schematic Diagram Series PositioningSystem (Electric) Fuel Leading Air4-15Functional Schematic Diagram Series PositioningSystem (Electric) Air Leading Fuel4-16Parallel Metering Control System4-17Parallel Positioning System with Oxygen Trim4-18Series Positioning System with Oxygen Trim4-19Oxygen Trim System with Damper Mounted Trim Device4-20Oxygen Trim System with Tory Link Trim Positioner4-12Response of Air and Fuel Flow to a Step Change inBoiler Load with Time Delay Feature5-1Single-Element Feedwater Control5-2Offset Experienced with Proportional-OnlyFeedwater Control5-3Response of Single-Element Feedwater Control5-4System to Rapid Load ChangeResponse of Three-Element Feedwater Control Systemto Rapid Load Change-. .-. .-S -5-5Two-Element Feedwater Control5-6Three-Element Feedwater Control5-7Thermo-Hydraulic Feedwater Control System5-8Thermostatic Expansion Tube Feedwater Regulator-.S. ----. r.t.t. t.t."
Figure NumberFigure Description7-1Bailey Electronic Manual/Auto Station7-2Bailey Pneumatic Manual/Auto Station7-3Bailey Electronic Manual/Auto Station with Bias Control7-4Hays-Republic Electronic Manual/Auto Station7-5Hays-Republic Pneumatic Manual/Auto Station7-6Hays-Republic Pneumatic Air/Fuel Ratio Relay7-7Hays-Republic Electronic Ratio Relay7-8Bailey Pneumatic Ratio Relay7-9Bailey Electronic Ratio Relay7-10Hays-Republic Pneumatic Master Pressure Controller7-11Hays-Republic Electronic Feedwater Controller7-12Bailey Thermo-Hydraulic Feedwater Regulator7-13Copes-Vulcan Thermostatic Expansion Tube FeedwaterRegulator! 7-14Bailey Level Transmitters7-15Bailey Flow Transmitters7-16Bailey Flow Transmitters with Square Root Extraction7-17Bailey Pneumatic Square Root Extractor7-18Honeywell UV Flame Detector7-19Bailey Combination UV and Flicker Flame Detector7-20Bailey UV Flame Detector7-21Flreye Infrared Detector System7-22Fireye UV Detector System7-23Hays-Republic Pneumatic Control Drivex. . .
Figure NumberFigure Description7-24Bailey Pneumatic Control Drive7-25Hays-Republic Compact Pneumatic Control Drive7-26Hays-Republic Electric Control Drive7-27Bailey Electric Control Drive7-28Bailey Pneumatic Valve Actuator-Diaphragm Type7-29Bailey Pneumatic Valve Actuator-Piston Type7-30Bailey Pneumatic Valve Positioner7-31Honeywell Solenoid Valve7-32Honeywell Hydraulic Valve Actuator7-33Hays-Republic Hydraulic Valve Actuator7-34Hays-Republic Circular Chart Recorder7-35Hays-Republic Strip Chart Recorder7-36Bailey Strip Chart Recorder
1.0INTRODUCTIONThe purpose of this manual is to familiarize boiler operatingpersonnel with the concepts which govern industrial boiler controlsystems.*It is intended for use by those who do not necessarily havean extensive background in instrumentation and control technology, butwho do have a basic knowledge of boilers and their ancilliary systems.The manual focuses on boilers in the 60 million BTU per hour (MMvBTU/hr) range, but many of the concepts are applicable to boilers ofany size.The three major areas of industrial boiler control are covered.These are: burner (or combustion) control, feedwater control, andflame safety systems.Section 2.0 provides pertinent backgroundinformation regarding the need for, and the objectives of, these threemajor subsystems. Section 3.0 is a discussion of control theory thatacquaints the reader in general terms with various control techniquesand concepts.Sections 4.0, 5.0, and 6.0 describe the control schemesthat are normally employed to provide the desired control of each ofthe respective boiler subsystems.Section 7 provides detailedinformation regarding the function and operational theory behind thevarious control components. Also included in Section 7.0 is vendor'scatalog data for selected control components.
.2.0BACKGROUND2.1General.The purpose of any boiler control system is to provide safe,efficient operation of the boiler at the desired output without theneed for constant operator supervision.This means that thecombustion process inside the furnace must be controlled as well as-:the steam conditions at the boiler outlet.The boiler must be able torespond to changes in load without jeopardizing safety or performance.Although all boiler control systems perform essentially the samefunctions, the systems themselves may be either quite simple or quiteintricate.Generally, the more complex the system the more precisethe control capability.However, the more complex the system, themore difficult it is to maintain, and the more susceptible it is tomalfunction.A variety of control techniques are available, and thechoice of which technique is the "best" is often merely a matter ofpersonal preference.Boiler control systems are generally broken down into three mainfunctions:controls.burner controls, feedwater controls, and flame safetyThe three are interrelated as far as actual operation ofboiler is concerned, but they are basically independent systems.*theThey will, therefore, be discussed separately here.2.2Burner Control SystemsIt is the responsibility of the burner control system to supplyair and fuel to the furnace in the correct proportions to meet thesteam demand.It is important that the correct air to fuel ratio be2-1
maintained, regardless of steam flow.Too much air will result ininefficient operation, and too little air may be dangerous as well asbeing inefficient.As the combustion process takes place in the furnace, oxygen inthe combustion air combines chemically with the carbon, hydrogen, andsulfur (if present) in the fuel to produce heat.The amount of airthat contains enough oxygen to combine exactly with all thecombustible matter in the fuel is called the "theoretical" combustionair.In actual practice, it is impossible for every molecule of oxygenthat enters the furnace to combine with the fuel.For this reason, itis always necessary to provide more air than the theoreticalrequirement.For oil and gas fired boilers it is customary to provide10 to 20 percent more air than the theoretical requirement to ensurecomplete combustion.This additional air is called "excess air," anda boiler firing at 1.2 times the theoretical air requirement would besaid to be firing at 20 percent excess air.Since air isapproximately 21 percent oxygen, a boiler firing at 20 percent excessair is also said to be firing at 4.2 percent "excess oxygen."If insufficient oxygen is introduced into the furnace, incompletecombustion of the fuel will occur.This not only wastes fuel, but itcan cause hazardous conditions in the boiler.*QThe unburned fuel maylater ignite in the boiler or breeching and result in a dangerousexplosion.Providing too much combustion air eliminates the explosionisdanger, but this, too, results in inefficiency.By far, the largestenergy loss in any boiler is the heat which escapes as hot flue gas.2-2
Increasing the excess air flow merely causes more hot flue gas to go,.*up the stack as wasted energy.It is, therefore, desirable to maintain the correct ratio ofcombustion air to fuel flow, or "air/fuel ratio," at all boileroutputs.Thus, the burner control system must simultaneously regulatethe fuel and air supply to the furnace any time a change in load isrequired.As mentioned earlier, burner control systems may become as simpleor complex as desired.For boilers in the 60 MM BTU/hr range, thecontrol systems are usually relatively simple, since the performanceimprovements possible generally cannot justify the cost of morecomplex systems. The firing rate of the boiler is normally determinedby steam header pressure only.This is called "single element" control since only one controlelement, pressure, is used.control may be used.In larger boilers, two or three-elementThat is, the firing rate of the boiler is notonly controlled by header pressure, but may also be controlled bysteam flow, steam temperature, or by a process signal such as theopening of a flow control valve.Burner control systems are discussed in detail in Section 4.0.2.3Feedwater ControlThe function of the feedwater control system is to providemake-up water to the boiler to replace the feedwater leaving as steamand/or blowdown.This is normally accomplished by maintaining aspecified water level in the steam drum.water level2-3It is essential that this
remain in the appropriate range.Too high a water level may causewater to be carried over into the superheater (if there is one) oreven to the load devices, either of which can cause significantdamage.tubes.Too low a water level may result in burn out of the boilerThe range of safe water level in the drum is usuallydetermined by the boiler manufacturer.It is dependent upon a numberof factors, such as the size and shape of the boiler drum, the designof the boiler, and the characteristics of the steam load.Maintaining a constant water level in the drum is not asstraightforward as one might think."level" usually does not exist.First of all, a clearly definedInstead there is a zone where steamand water are almost indistinguishable.The steam in the zone isentrained with many fine droplets of water.The water in the zonecontains a multitude of steam bubbles in an almost continuous mass.What is more, the volume of these bubbles can increase or decreaserapidly, giving a false indication of changing water level in thedrum.When the steam bubbles expand, this is known as drum "swell,"and when they contract, it is called "shrink."Drum swell is influenced by several factors.Among these are thedrum pressure, boiler design, firing rate, steam load, feedwatertemperature, and feedwater flow.The boiler design influences drum swell in a number of ways.*Theratio of heating surface to the volume of water in the boiler, thespeed of circulation of the water, and the surface area of the drumwater in relationship to the volume all have an effect on drum swell.2-4
At low drum pressures, the volume of pound of steam is muchgreater than the volume of a pound of water at the same temperature.Because of this, greater swelling occurs in boilers with loweroperating pressures.Rapid fluctuations in steam load or in boiler firing rate have amarked effect on drum swell or shrink.For example, if the steam loadis suddenly increased, the drum pressure will decrease, and the volumeof the steam bubbles will increase.More bubbles will also be createdsince the lower pressure will allow an additional portion of the drumwater to vaporize.The result is an apparent increase in drum levelwhen the actual quantity of water in the drum is less.An increase in firing rate will raise the drum pressure, whichin turn tends to decrease the volume of the steam bubbles and lowerthe drum level.However, increased firing also creates more steambubbles, and the net effect is usually an apparent increase in drumlevel.Increasing the feedwater flow will at first tend to decrease theboiler drum level.The feedwater has a cooling effect which collapsesthe steam bubbles in the drum.The colder the feedwater, the morepronounced the effect.%The problems associated with feedwater control become obviouswhen one considers the effects of drum swell and the difficulties that4can be encountered in determining the actual quantity of water in thedrum at any given time.Feedwater control systems, like burnercontrols, may be quite simple or may become rather sophisticated.4Again, the more complex the system, the more precise the control.2-51,-i-. ,.- -.-.2 . -.i .i ., -,. 2 , . .:. .
Smaller boilers in the 60 MM BTU/hr range normally use simple systemswhere only the drum level is monitored.*(This is single-elementcontrol since only one parameter is monitored.)-Larger boilers usetwo or three-element control, where steam flow or pressure andfeedwater flow are monitored in addition to drum level.The varioustypes of feedwater control systems are discussed in detail in Section5.0. 2.4Flame Safety SystemThe purpose of the flame safety system is to prevent thoseconditions which can lead to a boiler explosion.Such conditions canoccur any time unburned fuel vapors are present in the furnace orductwork,4,,jignition, either intentional or accidental, takes place.Start-up is an especially critical period, since explosions canresult from a variety of causes at that time.If the furnace is notproperly purged, fuel that has seeped past faulty shut-off valvesduring the boiler outage may explode when the ignitors are lit.Ifthe fuel that is intentionally introduced into the furnace duringstart-up does not ignite quickly, it too can accumulate with hazardousresults.During normal operation, an explosion can occur anytime theburner flame is extinguished and the fuel supply is not shut offimmediately.The flame can be lost for a number of reasons, includingimproper fuel pressure, interruption in fuel supply, contaminatedfuel, and burner malfunctions.2-6*
As mentioned earlier, h
The three major areas of industrial boiler control are covered. These are: burner (or combustion) control, feedwater control, and flame safety systems. Section 2.0 provides pertinent background information regarding the need for, and the objectives of, these three major subsystems. Section 3.0 is a discussion of control theory that
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A Lochinvar Crest series condensing boiler, model FBN2001 was installed to replace "Boiler 2" in January 2019. Boiler 2 was an AERCO Benchmark 2.0, serial number G-08-0799. New Boiler Information-SUN-224 Boiler Identification: Boiler 2 Location: Boiler Room Boiler Make/Model
the boiler and they have to enter the registration number of the boiler along with the following details a. Boiler Details : User need to provide following details of the boiler i. Types of Boiler/ Economizer ii. Total Heating Surface Area (Sq. mt) iii. Name of Manufacturer iv. Boiler/ Small Industrial Boiler/ Economizer Works Number v.
Fire tube steam boilers may be either high or low pressure boilers. There are three types of fire tube steam boilers: (i) horizontal return tubular boiler, (ii) scotch marine boiler, and (iii) vertical fire tube boiler. The boiler studied in the present experiment is horizontal return tubular boiler. This boiler is a 3 pass fire tube boiler.
8 UNIVERSAL steam boiler U-ND/U-HD 12 UNIVERSAL steam boiler U-MB 16 UNIVERSAL steam boiler UL-S/UL-SX 20 UNIVERSAL steam boiler ZFR/ZFR-X 24 Self-fired waste heat boiler 26 UNIVERSAL heat recovery steam boiler HRSB 27 Series UL-S and UT-H as waste heat boilers 28 Boiler control BCO 29 Service 30 References middle of 2012 the systems were sold .
Inspect boiler jacket door gaskets on front of cabinet and reinstall boiler jacket door after start or servicing. The boiler jacket door must be securely fastened to the boiler to prevent boiler from drawing air from inside the boiler room. This is particularly important if the boiler is
EU-34.2 Nebraska Boiler - #2 fuel oil EU-34.3 Nebraska Boiler - soybean oil EU-34.4 Nebraska Boiler - animal fats EU-34.5 Nebraska Boiler - biodiesel heavies EU-34.6 Nebraska Boiler - biodiesel EP-34.2 EU-34.21 Nebraska Boiler (Heat Recover Stack) - natural gas 02-A-387-S1 EU-34.22 Nebraska Boiler (Heat Recover Stack) - #2 fuel oil
stove, briquet COAL stove, coal briquet stove, anthracite LIGHT FUEL OIL boiler boiler, condensing LPG boiler, refinery gases boiler, NGL NATURAL GAS boiler boiler, condensing HEAT PUMP natural gas CC hydro nuclear WOOD CHIPS softwood hardwood tonnesCO2eq/GWhth Figure B.3 (cf. Figure 6.3) Figure C.1 (cf. Figure 6.4) D. TRANSPORTATION
