Working with Gases

The Lee Company has developed the Lohm Laws, a simple method of defining and measuring resistance to fluid flow for pneumatic components. Just as the Ohm is used in the electrical industry, we find that we can use a liquid Ohm or “Lohm” as an advantage when performing fluidic computations.

The benefit of using the Lohm Laws is that you can forget about coefficients of discharge and dimensional tolerances on drilled holes. These factors are automatically compensated for in the Lohm calculations and confirmed by our testing of each component to establish flow tolerances. The resistance to flow of any fluid component can be expressed in Lohms.

The Lohm has been selected so that a 100 Lohm restrictor will permit a flow of 250 standard liters per minute of nitrogen at a temperature of 59°F, and an upstream pressure of 90 psia discharging to atmosphere.

Due to the differences in fluid properties between gases and liquids, the equations for calculating the relationship between flow restriction, pressure differential, and flow rate are different.

View the resources below to learn all about Lohm Laws in applications for gas flow: