ICS 23.100.01                         PGD 36

New Standard from Last Update.

NATIONAL FOREWORD

This Indian Standard (Part 1) (First Revision) which is identical with ISO 6358-1 : 2013 'Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids - Part 1: General rules and test methods for steady-state flow' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on recommendation of the Fluid Power Systems Sectional Committee and approval of the Production and General Engineering Division Council.

In pneumatic fluid power systems, power is transmitted and controlled through a gas under pressure within a circuit. Components that make up such a circuit are inherently resistive to the flow of the gas and it is necessary, therefore, to define and determine the flow-rate characteristics that describe their performance.

IS 14740 was developed to determine the flow-rate characteristics of pneumatic valves, based upon a model of converging nozzles. The method included two characteristic parameters: sonic conductance, C, and critical pressure ratio, b, used in a proposed mathematical approximation of the flow behaviour. The result described flow performance of a pneumatic valve from choked flow to subsonic flow, based on static pressure. This new edition uses stagnation pressure instead, to take into account the influence of flow velocity on the measurement of pressures. Experience has demonstrated that many pneumatic valves have converging-diverging characteristics that do not fit the IS 14740 : 1999 model very well. Furthermore, new developments have allowed the application of this method to additional components beyond pneumatic valves. However, this now requires the use of four parameters (C, b, m, and Δpc) to define the flow performance in both the choked and subsonic flow regions.