Preface This is the second edition of ANSI Z21.93 / CSA 6.30, Excess flow valves for natural gas and propane gas with pressures up to 5 psig. It supersedes the previous edition published in 2013. Scope 1.1 This Standard applies to excess flow valves constructed entirely of new unused parts and materials intended for use after the service meter or second stage regulator (see Clause 3, Definitions), hereinafter referred to as valves, not to exceed 2 in (50 DN) nominal pipe size. 1.2 Valves covered by this Standard automatically limits the downstream flow of gas in the event that the flow reaches the valve's trip flow. 1.3 This Standard applies to valves for use with natural, manufactured and mixed gases, propane gas, and LP gas-air mixtures at pressures not to exceed 5 psi (35 kPa). 1.4 Valves are to have a minimum operating pressure of no greater than 5 in wc (1.24 kPa). 1.5 Valves are to be capable of operation within an ambient temperature range of -20°F to 150°F (-29 °C to 66 °C). Valves also are to be capable of operation at temperatures outside this specified range when so specified by the manufacturer. 1.6 If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification. 1.7 All references to pressure throughout this Standard are to be considered gauge pressures, unless otherwise specified. 1.8 This Standard contains SI (Metric) corresponding to the yard/pound quantities, the purpose being to allow the standard to be used in SI (Metric) units. (Standard for use of the International System of Units (SI): The Modern Metric System, IEEE/ASTM SI 10 or ISO 80000-1:2009 Quantities and units - Part 1: General are used as a guide in making metric conversion from yard/pound quantities.) If a value for a measurement and a corresponding value in other units are stated, the first stated value is to be regarded as the requirement. The given corresponding value may be approximate. If a value for a measurement and a corresponding value in other units are both specified as a quoted marking requirement, the first stated unit, or both shall be provided.