EngA DJM3 - Page 21

A DJM3
IOM-17 21 of 27 Mar 99 R3
PropaneGas
Combustionsetupforpropanefuelsforeitherthehighturndownorthestandardburneraresimilarto
theabove.Theonlymodificationsuggestedisitmaybedesirabletoincreasetheoxygensettingsby1%
to1.5%abovethosefornaturalgas.
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Due to the quantity of fuel that can be drawn off a propane tank,itisoftennecessarytoequipa
propanefuelsystemwithavaporizer.Theusualsignthatavaporizerisrequiredisthattheequipment
fuelsupplyfallsoffastheline“freezes”.Thefollowingcouldbeobserved:
 Lackoftemperaturerise,
 Rumblingorshakingburnerduetoair/fuelmix,
 Afterturningtheunitoffforaperiodoftimethefuellinethawsandrestartingit,allappears
tobenormal.
Highturndownburnersoperatingonpropanefuelwillgenerallyexhibitthefollowing:
HighFire At 3.5% O
2
 will appear yellow from behind the burner. However, if you could
view it from the other side of the burner you would see blue astheflame
lengthensout.
LowFire At16%O
2
theflamewilllikelybeyellow.At17%O
2
theflamewilllikelybeblue
andyellow.
Inlet/ManifoldPressureSettings
Manifoldpressuresettingsthattheunitwastestedandclockedatinthefactoryarerecordedonthe
unitratingplate.Anyattempttoclockaunitinthefieldshouldbedonewithcareascorrectionsfor
density (altitude and station pressure), temperature, and for themeterareoftenoverlooked,thus
leadingtoanincorrectconclusion.
Inletgaspressuresarerecordedontheunitlabel.Athighfireinletgaspressuretotheunitshouldnot
fallbelow6.25"onunits designed for 7" inlet pressure.If designis for14"pressures should notfall
below12".
Ifdesignisfor11"propanegas,theninletpressuresshouldnotfallbelow10".Notethatwithpropane
firedunitsitmaybenecessarytoequipthepropanesystemwithaproperlysizedvaporizer.
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