Control system for a multiplicity of muffle burners

Claim 1

A control system for at least two swirl-type muffle burners connected to a common supply conduit for supplying combustion air to said burners, each said burner having at least two coaxial ducts for conveying parallel flows of combustion air; each duct having means therein for imparting a swirl to the flow of air flowing therethrough, a control element connected to the outer of said ducts for controlling the flow of air to said outer duct, and a blower for supplying air to said conduit; said control system including a pair of first controllers, each controller receiving a load dependent set value and being connected to a respective burner to receive a measured value of the amount of air flowing to said burner, each controller being connected to said control element of said respective burner to adjust said control element in response to a differential between said set value and said measured value to control the flow of air through said outer duct; and a second controller connected between and to a first point located between said blower and said swirl-imparting means in the inner duct of one of said burners and a second point located downstream of said swirl-imparting means for measuring a pressure difference between said points, said second controller being connected to said blower for controlling said blower in response to a predetermined pressure difference between said points to control the amount of air delivered through said blower.