Values in the chart are taken from the compressed Air and Gas Handbook, published by the Compressed Air and Gas Institute, 2130 Keith Building, Cleveland, Ohio 44115.

Remember, the sharper the edge of the orifice, the less the flow and pressure drop will be affected by changes in the fluid viscosity and temperature.įigures in the chart are theoretical SCFM air flows through perfect orifices (See text) PSI The orifice plug must be machined by the user. Be sure plug is installed with shoulder facing toward the pressure. A shoulder on the plug keeps it from being pushed out of place by hydraulic pressure. An orifice plug may be installed next to a nipple, elbow, or tee. For low pressure applications using steel pipe, a very thin orifice plate may be installed in a gasket-type union as indicated in this figure.įigure 2. Countersink finished hole for a sharp edge.įigure 1. Drill orifice undersize to start and run a preliminary test then enlarge as necessary using standard twist drills. Orifice Diameter, InchesĬaution! Calculated values of pressure drop are approximate. Pressure Drop (ΔP) = 2įigures in this chart are PSI pressure drops across sharp edge orifices, petroleum type hydraulic oil. For values not shown in the chart, use this formula: The chart was calculated from information furnished by Double A Products Co., in which the constant 23.5 was developed by trial and error for average orifices. Multiply all chart values by 1.23 for water flow.

For example, to find the pressure drop of water, with a specific gravity of 1.00: Using a heavier fluid, a multiplying factor should be applied to chart values. Specific gravity of the fluid makes a significant difference in the pressure drop through a given orifice, and increases approximately as the square of the increase in specific gravity, The chart was calculated for a fluid with 0.9 specific gravity, a close approximation for all petroleum hydraulic oils. Chart values must be considered as approximate because a number of factors such as specific gravity, orifice efficiency, plumbing ahead of and behind the orifice may cause variations from the values shown.īy making the orifice with a knife edge, it becomes insensitive to temperature, and the flow and pressure drop will remain the same over a reasonable range of oil temperatures (and viscosity changes). It may be used for designing limiting flow orifices in hydraulic systems. The chart shows approximate pressure drops which may be expected at various flows rates through sharp edge orifices for petroleum type hydraulic oil.

Orifice size chart