A majority of industrial processing systems use flow instruments for measuring the flow rate. Flow ranks third when it comes to the most measured magnitudes in industrial processes.

Flow measurement is important as with the use of appropriate flow meter experts can carry out accurate measurements of fluid flow which ensures fluid control processes operate smoothly, cost-effectively and safely.

There are primarily two types of flow measurements that are carried out and according to which the flow meter types are available. Volumetric flow and Mass flow are the two kinds of flow measurements.

Continue to read till the end to find out all about them and differences between the two.

Mass Flow

Mass flow refers to the measure of a mass moving per unit time. This mass is represented by the molecular number present in a substance. The mass of a gas doesn’t alter in pressure and temperature, its weight remains constant.

The mass flow rate is expressed in - lb/min and kg/hr. But the unit for gas measurement is calculated in either standard cubic feet per minute (SCFM) or standard cubic meters per hour (m3n/hr).

Volumetric Flow

This is also referred to as actual flow, is basically a volume of medium passing per unit time. Some common measuring units of volumetric flow are CFM or ACFM, m3/min or m3/hr.

Volume is a substance that occupies a three dimensional space and when the volume is a gas, it either expands or shrinks with alterations in pressure and/or temperature. In case of rise in temperature, the space that is occupied by the volume tends to increase.

Whereas when the pressure is increased, the volume relatively decreases. Therefore, when it comes to measurement of volumetric flow, the experts are needed to take into account the gas temperature and pressure.

Comparing Flow Meter Results

It is likely to install multiple flow meters in an industrial plant. But how do you compare the results between the two flow instruments? Since the temperature and pressure differs from one another. Well, the action really depends on which type of flow meter used -

For Mass Flow Meter - Users can compare the results directly and there is no need for extra calculation.

For Volumetric Flow Meter - Pressure and temperature are the two factors taken into account. Therefore, this makes the comparison of results a bit tricky than mass flow meters.

When to Use Which Type of Flow Meter

Volumetric flow meter is used when volume of the fluid flow is required and high accuracy is not necessarily needed. However, users must note that volumetric flow meters require additional compensation for pressure and temperature.

On the contrary, mass flow meters are for measuring flow rate independent of fluid temperature and pressure. Therefore, they are much more reliable offering more repeatability and high accuracy.