Liquid vs. Gas Calibration

Should it be necessary to use a gas calibrated component for liquid service, or a liquid calibrated component for gas service, the following factors should be considered. Allowance should be made for variations in liquid/gas correlation of up to ±15%. This is caused by the response of different fluids to the orifice geometry. Single-orifice restrictors will correlate directly from gas to liquid service, subject to the ±15% normal variation. Multi-orifice restrictors will correlate directly only when the pneumatic pressure ratio is very low (P1 / P2 < 1.2). When multi orifice restrictors are used at higher pressure ratios, the gas flow will be up to 30% higher than expected from a liquid calibration. This is caused by gas compressibility which results in a non-uniform distribution of pressure drops through the restrictor.

STANDARD CONDITIONS

U.S. Standard Conditions at sea level are per ICAO STD ATMOSPHERE
Pressure………………….. 14.70 psia (29.92 in. Hg)
Temperature…………….. 59°F (518.7°R)
Other references may use somewhat different conditions.

RElated Resources

• Lohm Laws – Working With Liquids
  Define and measure resistance to hydraulic flow to ensure the proper flow rate
• Fluid Mechanics for Liquids
  Accounting for the impact of various factors affecting hydraulic fluid mechanics
• Lohm Laws – Working With Gases
  Define and measure resistance to pneumatic flow to ensure the proper flow rate
• Fluid Mechanics for Gases
  Accounting for the impact of various factors affecting pneumatic fluid mechanics