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The Mass Flow Company: Why Mass Flow?

In most processes flowing gases like Air, N2, Methane etc... it is gas mass, not gas volume, which is the critical variable. Volumetric flow measurements are less reliable than mass flow measurements because changes in gas temperature and pressure will change the density of a fixed volume of gas.

In the control process, additional errors can be propagated by back pressure changes in the process. Unlike orifice plates, rotameters, variable area (VA) meters, differential pressure (DP) meters, turbine meters and all other volumetric flow devices, thermal mass flow meters and controllers are relatively immune to changes in inlet temperature and pressure. Because these instruments directly measure molecular flow (count gas molecules), they provide the most reliable, repeatable and accurate method for delivering gases from a supply volume to a process at a desired mass flow rate.

How it works: Watch Mass Flow Controller Video

Sizing & Selection

As a result, mass flow rate is the quantity of direct interest whenever the molecules of the gas are the control variable in your process — such as combustion, chemical reactions, ventilation, product drying and a variety of other process applications.

Conventional flow meter manufacturers know that you need mass flow.  They do their best. But when you must buy additional temperature and pressure transmitters to convert the volumetric flow signal, you lose more than just money; you lose accuracy and you lose reliability.

Today you need high perfor­mance, cost effective instrumentation—and thermal mass flow meters have been proven to meet this criteria in a wide range of process applications.

Mass Flow Benefits vs. Volumetric Flow Measurement

  • Lowest Cost of Ownership. No need for additional devices, easy installation, and neglible operating costs.
  • Widest Turndown. With turndowns 10 times that of AP meters, thermal mass flow meters offer unmatched flexibility and exceptional low flow sensitivity. Fast Response. 1 second.
  • Direct mass flow measurement is more accurate and cost effective.
  • Direct Mass flow does not need any pressure or temperature compensation equipment or flow computers.
  • Provides immunity to process changes in P & T; i.e., very repeatable measurements.
  • In Gases, density is highly variable. This makes Volumetric gas flow very sensitive to changes in pressure and temperature.
  • Over 80% of all industrial processes—such as those involving chemical reactions, combustion, respiration, and HVAC—are based on mass flow, not volumetric flow.

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