This type of device has a flow restriction in the line that causes a differential pressure or “head” to be developed between the two measure-ment locations. Differential pressure flowmeters are also known as head meters, and, of all the head meters, the orifice flowmeter is the most widely applied device. Italian physicist Giovanni B. Venturi (1746-1822) in 1797 performed the first recorded work that used orifices for the measurement of fluid flows.
Orifice Plate with weld neck flange union
The weld neck flange is normally referred to as ” high Hub” flange. It is designed to transfer stresses to the pipe, thereby reducing high stress concentrations at the base of the flange. The pressure tappings are provided through the flangewhich arte at a distance of 1″ from the face of the plate (shown in the drawing attached). Weld neck flanges are prefered where radiography on welding is involved.
Orifice Plate with slip on flange union
The slip on flange has a low hub because the pipe slips into the flange prior to welding. It is welded both from inside and out to provide sufficient strength and prevent leakage. The slip on flanges are bored slightly larger than the OD of the matching pipe.
Orifice Plate with male-female carrier ring and flanged union
The construction is similar to the above except male-female carrier ring is provided to facilitate pressure tapping through it (corner tapping). This construction is generally used for lower line sizes (normally less than 2″). Carrier rings are also available for bigger sizes on request. Carrier ring machined from single block is also offered in place of male-female carrier. For better accuracy, honed meter run assemblies are recommended which employ upstream and downstream straight lengths. The end connection in such case can be plain (suitable for welding) or flanged.