Choosing the Correct Regulator: Part IV – Flow

Flow

Flow is an important factor to consider when selecting an air pressure regulator because it determines the amount of air that can pass through the regulator at a given pressure.  The flow rate through a pressure regulator is determined by the pressure difference across the regulator and the size of the orifice or valve opening that controls the flow.  The flow rate is generally expressed in terms of standard cubic feet per minute (SCFM) or liters per minute (LPM), and it can be calculated using various equations depending on the specific conditions of the system.

Valve flow coefficient (Cv) is a measure of the flow capacity of a valve, which is typically used to size regulators and other control valves for a particular application.  Using the Cv when choosing a regulator should be done carefully. For more information on Valve Flow Coeffiecient (Cv), please refer to blog ‘Cv and Your Pressure Regulator’. Some Cv values that manufacturers publish could be based on a fully open valve in a regulator.  This should not be the normal operating condition of a regulator.  In some cases, the limiting factor is the port sizes on the regulator.  The actual internal valve could be the choke point, so an increase in port size may not be appropriate.

There is also a phenomenon called droop to be considered.  As flow increases, the set output pressure will drop.  Precision regulators lessen the effect of droop. For more information on droop and reading flow curves for different regulators, take a look at the blog: Understanding a Regulator Flow Characteristic Curve. If the flow rate through a regulator surpasses the maximum, the output pressure will drop and become erratic.

When selecting an air pressure regulator, it is important to consider the flow rate required by the application and choose a regulator with an appropriate flow capacity to ensure optimal performance and safety.