1.1 This specification covers requirements and test methods for excess flow valves for use in thermoplastic natural gas piping systems. However, it is expected that excess flow valves manufactured to the requirements of this specification may also be used in other natural gas piping systems.1.2 Excess flow valves covered by this specification are designed for insertion into components for natural gas systems such as pipe, tubing, or fittings in sizes from 1/2 CTS to 2 IPS.1.3 Th