Limiting Orifice Gas Valves regulates the flow of gas in the burner for adjustment of air / gas ratio. Limiting Orifice Valves are installed in upstream of nozzle mix gas burner for adjustment air /gas ratio. A V-port plug is adjusted to increase or decrease of flow of gas. Limiting Orifice valves are not designed for turning off gas for which suitable shut-off valves are to be installed in the upstream.