Understanding Flow Capacity Standards in Pneumatics

This white paper outlines the various standards used to express flow capacity in pneumatic systems, focusing on the coefficient of flow (CV) and other related metrics. It explains that CV is a common standard, but there are multiple terms and methods, such as C (sonic conductance) and effective orifice size, that engineers may encounter. Each term has specific meanings and formulas, which can vary by manufacturer. The paper emphasizes the importance of understanding these differences to avoid miscalculations that could lead to improperly sized components. It also discusses the ANSI/NFPA T3.21.3 specification for calculating CV, highlighting the need for adherence to testing procedures. Additionally, it addresses the challenges posed by compressibility of air in pneumatic applications and the potential confusion arising from different manufacturers' practices. The paper concludes by stressing the necessity for engineers to grasp these flow measurement methods to ensure accurate application in pneumatic systems.