The present form of the ASME type venturi as manufactured by Energy Flow was first developed as a practical differential pressure producing device for flow measurement by Clemens Herschel in 1887. Since that time, it has been universally accepted as the most efficient primary device available. No other type of venturi or flow lube design has been more thoroughly researched, tested and proven than the ASME type. Energy Flow Venturis have been in operation in petrochemical, refining. gas pipeline, metals, water, sewage and power plants since 1964. They are used wherever low pressure loss, high accuracy. piping restrictions or liquids containing solids are encountered.