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I have a question regarding NFPA 86 Ovens and Furnaces, Ch 8 on Purging of Combustion Systems

Question asked by infocenter on Nov 19, 2020

Our client has two Regenerative Afterburners (RABs) which are used to oxidize organic vapors and carbon monoxide from a sludge thermal conditioning system. Each RAB has two gas fired burners at the top of the oxidizer. Before an RAB burner can be lit the duct work and sludge holding tanks upstream of the RABs are purged for a 20 minute purge cycle which is always done before a burner is lit. 

Sometimes they have difficult getting either RAB burner lit and they exceed the time limit for lighting a burner in which case they presently go through another 20 minute purge cycle before they attempt to light the burners again. 

Question is; When they have purged the system for 20 minutes and then cannot get a burner lit, can they continue to try and light a burner beyond their preset time limit for lighting a burner as long as they continue to purge the system. In other the words the initial purge cycle would continue for longer than 20 minutes to provide more time for the plant to get the burners lit. Thus, the initial purge might go on for 40 or 60 minutes. The plant would be able to lit the burners after the initial 20 minutes of the purge.