North American Pneumatic Combustion Air Blower (using) 3070 Inspirator with Compressed Air
Sheet 3070-1
Inspirated Air = Aprox. 79%
Low pressure combustion air to burner
INSPIRATORS AS A COMBUSTION AIR SOURCE
Compressed Air = Aprox. 21%
Specially sized 3070 inspirator mixers can be used to supply combustion air as an alternative to a traditional blower. While this sacrifices the economy of a blower, it may be a good option for applications where it’s difficult or expensive to install a combus- tion air blower, and the cost of compressed air can be tolerated. Example applications: - If a burner or pilot only needs to run for a limited time. - It is difficult to instal a blower - It is difficult to provide electricity for a blower To use a 3070 mixer as a substitute combustion air blower, compressed air is connected to what would normally be the gas inlet. The compressed air entrains nearly 4X the volume of addi- tional air into the mixer which provides a low-pressure air stream at the outlet. Approximately 21% of the total air discharged from the mixer outlet is from the compressed air inlet. For most applications inlet pressure must be at least 40 times the desired outlet pressure. Like a traditional blower, the mixer air inlet must be in a place where clean air can be pulled into it. If there are products of combustion or other inert gases nearby the oxygen content of the combustion air could be reduced which will effect burner performance. 3070 inspirator mixers used with compressed air to provide combustion air are known as “Compressed Air Reducers.” For this application use the tables in this sheet to pick the appropriate 3070 mixer size. See table 1 if using US Customary Units or table 2 for SI units. See Bulletin 3070 for detailed 3070 dimensions, parts list, and additional information.
3070 inspirator mixer
The spud drill size in 3070 mixers used to supply combustion air are much larger than those used with standard 3070 air/ gas mixers. Otherwise the mixers are identical and can be easily converted for use in either application by replacing the spud. In the photo at below, a North American 3070-8 Inspirator (arrow a) supplies combustion air to a 4422-8-A Burner in the cover of a charging bucket preheating 20 tons of scrap for an electric melting furnace. The 3070 replaces a traditional blower and permits the use of two small flexible supply lines (arrow b) for compressed air and gas – a great convenience in a case such as this, where the burner must move with the cover.
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