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Calculating Liquid Flow Through Orifices — A Technical Guide
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For the broad array of industrial applications concerned with liquid flow control, extremely accurate, repeatable results are necessary to successful operation. To achieve such precision, it is crucial to understand the various technical factors that are involved in determining the correct orifice size that will create the desired results. These include pressure, temperature, type of liquid and others.
To help facilitate selection, precision orifice manufacturers often provide flow charts within a common range. However, not all applications fall within this data set. Our Technical Guide details a number of formulas, with examples, which can be used to extend orifice flow data beyond the charts.
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Overview
This O’Keefe Controls Co. technical document focuses on precision calculation of liquid flow through orifices, essential for numerous industrial flow control applications. Achieving highly accurate and repeatable flow control requires a clear understanding of multiple technical factors influencing orifice sizing and flow rate. Key variables include pressure, temperature, and the specific liquid type, all of which affect flow characteristics and orifice selection.
The guide emphasizes the importance of precision orifice manufacturers providing flow charts as a foundational tool to help engineers select the appropriate orifice size within common operating ranges. However, because some applications extend beyond typical chart data, the document supplements these charts with detailed formulas and methods for calculating flow under varied conditions such as different pressures, temperatures, or liquid types other than water. This extension enables tailored and reliable orifice sizing for specialized use cases.
On page 7, the document includes comprehensive data tables for metal orifice water flow rates expressed in liters per minute. These data are calculated from the flow coefficient (C_v) for each orifice diameter, using the formula: Flow = 3.875 × C_v × ΔP, where ΔP is the differential pressure in psi. The assumption is that the orifice is surrounded by fully flooded liquid with no air pockets. The table lists orifice diameters (from 0.005 inches to 0.125 inches), sizes (numbered for reference), their corresponding C_v values, and the resulting flow rates at various supply pressures ranging from 1 to 100 psig. This detailed tabulation provides practical, ready-to-use flow values for engineers specifying orifices in water systems.
Overall, the document serves as a critical reference for engineers and system designers seeking precise orifice sizing and flow calculations. It combines theoretical explanation, practical charts, and formula-driven calculations, catering to both standard and specialized industrial liquid flow control needs. The company offers further technical support to ensure optimal application solutions. This resource underscores O’Keefe’s commitment to precision and technical expertise in flow control components.