Choosing the right differential pressure flow meter for an application can be challenging. This article outlines the considerations and trade-offs in selecting the optimal technology.

Selecting the right differential pressure flow meter is a balancing act—one that involves defining the purpose of the measurement, specifying the application parameters, understanding the environmental and safety needs, and prioritizing the selection criteria to determine the optimal flow technology.

Purpose of Measurement
Understanding the purpose of the measurement is the first step in the selection process. What will be done with the flow information? How critical is the measurement? What decisions will the user make with the information? In general, flow information is used for either the controlling or monitoring of processes. There are many reasons to measure flow, some more critical than others. They can range from batching, continuous blending, custody transfer and mass balance, to inventory control, governmental regulation compliance and safety.

Flow Application
Of the many flow meters available for measuring fluid flow, the type of flow meter used often depends on the phase of the fluid—liquid, gas or steam—and the conditions under which the fluid is measured. These conditions include line size, flow rate, process pressure and temperature, ambient pressure and temperature, and chemical properties. For example, insertion flowmeters are more frequently used in steam, large line sizes and in situations where process shutdown is not a possibility.

Wet gas applications, where the presence of liquid in a gas stream can pose significant challenges, are another example. Technologies like conditioning orifice plates eliminate damming and provide predictable and correctable results when the moisture content is known. Inline metering technologies are the best practice for small line sizes as the possibility of errors caused by installation are reduced.