Furnace Pressure Flue Port Size and Location

FURNACE PRESSURE FLUE PORT SIZE AND LOCATION (see also references 51 and 59  

In most industrial process heating, the pressure in the heating chamber should be atmospheric, or only very slightly positive, at all firing rates. 

The lower the temperature to which the material is to be heated, the greater the necessity for thorough gas circulation in the heating chamber, especially if loads are placed compactly in the furnace or oven (e.g., piled or coiled material that is to be heated rapidly and uniformly. (See sec. 6.6.) 

In a tall furnace, it is impossible to have the same pressure at all levels because the furnace acts as a chimney, with its internal pressures increasing with elevation within the furnace. Depending on the magnitude of (a) pressure created by a forced draft fan or blower or (b) suction created by an induced draft fan, eductor, or natural chimney draft, the furnace may have any of the following situations  

How should an engineer select situation 1, 2, 3, 4, or 5 (i.e., automatic furnace pressure control setpoint) for the pressure sensor location And is the pressure sensor located properly for the process  

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