This document specifies the terms and definitions, classification, structural types and main parameters, basic requirements, technical requirements, test methods, inspection rules, signs, certificates, instructions for use, and packaging of double-walled pipes for marine gas transportation (hereinafter referred to as double-walled pipes). , transportation and storage and quality commitment. This document is applicable to gas inner pipes with a design pressure of not more than 60.0 MPa, a design temperature of not less than -196°C, a nominal diameter of DN20 to DN450, a transmission medium of natural gas, liquefied natural gas, liquid ammonia, methanol, etc., and a double-layer structure. Rigid pipe made of stainless steel. Double-walled pipes with nominal diameters of gas inner pipes smaller than DN20 or larger than DN450 may also refer to this document. Note: In this standard, unless otherwise noted, pressure refers to gauge pressure.