Orifice Meter vs. Venturi Meter: Flow Measurement Explained with Diagrams

Orifice meters and venturi meters are widely used devices for measuring fluid flow. Both operate based on the principle of pressure drop across a flow restriction created by their unique geometry. However, there are distinct differences between these two methods.

Orifice Meter

An orifice meter comprises a flat plate with a circular hole at its center, positioned within the flow path. As the fluid passes through the orifice, it experiences a pressure drop, which is measured using pressure taps located upstream and downstream of the orifice plate. The pressure difference is directly proportional to the flow rate. Typically, orifice plates are installed between flanges in a pipe, and the orifice size is determined by the pipe diameter.

Diagram of Orifice Meter:

Venturi Meter

A venturi meter consists of a tapered tube featuring a constricted throat section. When fluid flows through the venturi meter, its velocity increases in the throat, resulting in a pressure drop. This pressure drop is measured using pressure taps placed upstream and downstream of the venturi meter. Similar to the orifice meter, the pressure difference is proportional to the flow rate. Venturi meters are usually installed between flanges in a pipe, and the size of the throat section is determined by the desired flow rate.

Diagram of Venturi Meter:

In Summary

The primary distinction between the two lies in their design: the orifice meter uses a flat plate with a hole, while the venturi meter employs a tapered tube with a constricted throat. While both methods measure the pressure drop across a flow restriction to determine flow rate, the orifice meter measures the pressure drop across the orifice plate, whereas the venturi meter measures the pressure drop across the throat section.