Siemens LMV52.440B1 - Introduction; O 2 Trim (O 2 Control) Fundamentals; 

TechnicalInstructions  LMVSeries
DocumentNo.LV5‐1000
Section6 Page2 SCCInc.


Introduction

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.

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.

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.

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.

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.

O
2
Trim(O
2
Control)Fundamentals

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.




HOME