Practical Pointers | Fives North American

REGULATORS

Control valve

Air

Air and gas mix in venturi

Mixer

Gas

Atmospheric (0) pressure

A

Built-in limiting orifice

Atmospheric (0) pressure

Drip leg

Air/gas ration regulator

ATMOSPHERIC REGULATOR SUPPLYING A PREMIX BURNER SYSTEM

As air flow through the venturi increases, increased suction causes more gas flow through the limiting orifice valve. This in turn slightly reduces the pressure at "A" which causes the regulator to open and allow more gas to flow and maintain the atmospheric or "zero gauge" outlet pressure. Because a slight amount of force is required to raise the internals and open the regulator, the pressure at "A" may drop off 1 or 2 tenths of an inch w.c. at full flow. This "droop" has only a minor effect on accuracy of control when the regulator is properly sized.

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