Dual Valve

  • Thread starter Alberto Maldonado
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Thread Starter

Alberto Maldonado

Dear List:

We have an Old Furnace to temper metal sheet at 500 Fahrenheit Degree. This Furnace has a "dual Valve" it means 1 Valve for the Gas and Another for the Air to Mix both of them at the Burner. They are mechanically linked with a range appropiated and determined with the practice, for every Valve. I ask if there is another technology to control every Valve independently or in another way could we use a servomotor for this application ?, I think that the curve Aperture
versus constant mixed gas flow gives not a good burning maybe can shut off the flame.

Thank You for your Attention.

Mr. Alberto Maldonado
E-Mail: [email protected]

David Gwinup

It sounds to me that even if you do control each valve independently, the control system would only mimic the mechanical linkage that you are now
using because it would still rely only on the percentage opening of the valves.

However, the next level of automation would be to add pressure & temperature compensated flowmeters to the gas and air headers so that you can accurately determine the flows and provide a good air/fuel mix.

Going further, you could add a flue gas oxygen analyzer to determine the excess air and provide feedback control to the air supply so that you always have just enough combustion air.

William T. Dolan Raytheon Engineers & Co

Cross-limited fuel/air control is a more precise method for combustion control. You will need separate fuel and airflow measurements, which may be relative, but must be repeatable.
My reply may be too late. Still, before doing any modification, check first your country code
if these separation is accepted. I doubt because some undesirable puffing condition may develop
and will surely develop accordingly to Murphy's law !!!