A STUDY OF VENTURI TUBES

The purpose of this study is to examine the American Society of Mechanical Engineers (ASME) Venturi Tube. This study is conducted with regard to published standards for design and installation, manufacturing, and the comparative analysis of laboratory flow calibrations to the theoretical predictions of the coefficient of discharge. Design considerations will be investigated for venturi standards such as ASME MFC 3Ma-2007, ISO 5167-4 (2003-03-01) and ASME PTC 19.5-2004. Summaries for the ranges of use will be presented for diameters, beta ratio, and Reynolds Number. The types of venturi such as As Cast, Machined and Rough Welded Sheet Iron Inlet, will be presented as well as some alternative designs which do not fit well into these categories. The alternative designs include designing with heavy wall pipe and other material concerns. Manufacturing techniques and limitations will also be discussed. The data from many laboratory flow calibrations are utilized to examine the prediction equations for the Coefficient of Discharge and to determine the effects of materials and manufacturing processes such as post weld stress relieving. ASME MFC 3Ma-2007 (MFC 3Ma) and ISO 5167-4 (ISO 5167) predict a constant coefficient of discharge for a limited Reynolds number range based on the type of venturi. ASME PTC 19.5- -2004 (PTC 19.5) states that the coefficient of discharge varies with the Reynolds number and should have the same prediction equation as a throat tap flow nozzle. In conclusion, preliminary results based on flow calibration data from an independent laboratory indicate the prediction of coefficient of discharge from the equation published in ASME PTC 19.5-2004 more closely agrees with the laboratory determined coefficient of discharge.