The most commonly used venturi tubes are of the ASME classical or Herschel style (Figure 500-9). Venturi tubes are used primarily in low static line pressure applications where high pressure recovery is important. They may be used in air, steam, water, gas, chemical, and light slurry.
The long-term permanent head loss is typically between 10 to 14% of the measured differential. Figure 500-10 compares the overall pressure loss through several primary elements.