Preface This is the third edition of CSA Standard CSA 6.18, Service Regulators for Natural Gas . It supersedes the previous editions published by the Canadian Gas Association in 1995 and 1991 as CGA 6.18, Internal Relieved Service Regulators for Natural Gas. The following are the most significant changes from CGA 6.18-M95: (a) the title has been changed and the scope expanded to include provisions for overpressure cut-off (OPCO) devices; (b) a new comprehensive clause on definitions has been added; (c) this edition requires that all regulators be capable of operation over a temperature range of –40°F (–40°C) to 150°F (65.6°C); and (d) a new appendix (Appendix B) describing a variable temperature performance test has been included to determine how the regulator components will perform when subjected to variable temperatures observed under field conditions. This Standard was prepared by the CSA 6.18 Technical Committee on Service Regulators for Natural Gas, under the jurisdiction of the Strategic Steering Committee for the Gas Industry, and has been formally approved by the Technical Committee and the Interprovincial Gas Advisory Council. Scope 1.1 These provisions apply to the construction, materials, performance, and testing of NPS 1-1/4 in and smaller self-acting service-type regulators with internal relief valves or overpressure cut-off (OPCO)* devices, or both, utilized to control the pressure of gas delivered to a customer's piping at a delivery pressure of 5 to 9 in water column (1.24 to 2.24 kPa), for installations designed for capacities up to 250 SCFH (7.1 m3/h). *Overpressure cut-off (OPCO) devices are also referred to as overpressure shut-off (OPSO) devices. 1.2 The yard-pound units provided are the standard. The SI (metric) equivalents in parentheses may be approximate values and are provided for information only, or for markings where both units of measurement are required.