What is the primary function of a "spud" or burner orifice?

The primary function of a "spud" or burner orifice is to regulate gas flow to the burner. This component is critical because it controls the volume of gas that mixes with air before it is ignited in the combustion chamber. By limiting the amount of gas that can pass through, the orifice ensures that the gas-to-air ratio is maintained at an optimal level for efficient and safe combustion. This regulation helps prevent conditions such as high emissions or unsafe operation of the furnace, thereby enhancing performance and safety.

While air and gas do need to be properly combined for combustion, that function is more pertinent to the overall design of the burner rather than the role of the orifice itself. The orifice does not control ignition timing, which is managed by the ignition system, and it also does not function as a filter for impurities from the gas. Therefore, the main role of the burner orifice is undeniably about regulating the gas that reaches the burner.