Siemens LMV5 Series - Introduction; O 2 Trim (O 2 Control) Fundamentals; 

TechnicalInstructions  LMVSeries
DocumentNo.LV5‐1000
Section6 Page2 SCCInc.
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Introduction
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TheLMV52.240andtheLMV52.440bothhaveO
2
(oxygen)trimandO
2
alarm(previouslycalled
“monitor”)capability.Inaddition,theLMV52.440offersadvancedfeaturessuchastemperature
compensatedlight‐offandmoredynamicO
2
trimcapabilities.Ingeneral,theLMV52.440is
recommendedformoredifficultapplica tionssuchaslowandultra‐lowNOxburnerswheretheburner
stabilitybandismuchsmallerthanatraditionalnozzle mixingburner.Somefeatures intheLMV52.440
werespecificallydesignedforultra‐lowNOxmeshburners.
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TheO
2
trimfunctionsbyusinganin‐situO
2
sensorinstalledintheboilerstack,andthenadjusting
actuatorsand/orVSDtomaintaina%O
2
setpoint.Onlyair‐related(airinfluenced)actuatorsare
adjusted,thustheO
2
trimdoesnotadjustthefiringrate(fuel‐relatedload).Onlytheairrate(air‐related
load)isadjusted.
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EachRatioControlCurvePointthatisentered(seeSection4)willhaveacorrespondingO
2
trimsetpoint,
richlimit(O
2
alarm)andleanlimit(O
2
maxvalue).TheexceptiontothisruleisthatO
2
trimcannotbe
performedonPoint1.If10pointsareenteredontheRatioControlCurve,therewillbe9trimpoints
and10richlimit(O
2
alarm)points.Having10pointsontheRatioControlCurveisrecommended.
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AsisthecasewithadvancedsystemssuchasO
2
trim,thefundamentalsystemsthatlieunderneaththe
advancedsystemmustbeinplaceandworkingcorrectlytoenabletheadvancedsystemtowork
correctly.Forexample,ifthegaspressuresupplyisnotrepeatableupstreamofthefiringratecontrol
valve(fundamentalsystem),thentheO
2
trim(advancedsystem)islikelytodeactivate.The
fundamentalsystemsontheburner/boilerthatmustbeworkingcorrectlyareoutlinedindetailinthe
Pre‐RequisiteslistedinSection4.ThePre‐RequisitesforLMV52systemswithO
2
trimmustbemet
beforeO
2
trimcommissioningisattempted.
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IfthePre‐Requisitesaresatisfied,thenreliableoperationoftheO
2
trimdependsoncorrectparameter
settingsfortheapplicationandcorrectcommissioningoftheO
2
trim.Thissectionwilloutlinethebasics
behindhowtheO
2
trimsystemoperates,andwilloutlinethetypicalcommissioningprocedurefora
traditionalnozzlemixingburner(standardemissions)andapre‐mixmeshburner(loworultra‐lowNOx).
NozzlemixingburnersthatuseahighpercentageofFGRtoachievelowNOxtypicallybehaveinaway
thatissimilartoapre‐mixmeshburner,sothecommissioningprocedureforthese
typesofburnersis
similartoapre‐mixmeshburner.
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O
2
Trim(O
2
Control)Fundamentals
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Bydefinition,anO
2
trim(O
2
control)systemmonitorsthelevelofO
2
intheexhaustgasesoftheboiler
andadjuststhefuelorairflowtomaintainanO
2
setpoint.TheLMV52accomplishesthistaskbyreading
the%O
2
(wetbasis)withanin‐situO
2
sensorandbyadjustingtheangularpositionofairflowinfluenci ng
actuators.IftheburnerisequippedwithaVSD(variablespeeddrive)fortheblower,theO
2
trimcan
alsoadjusttheblowerspeedtoinfluencetheburn erairflow.
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