This International standard describes requirements, design and installation of flexible pipe elements (e.g., metallic flexible pipe, metallic flexible tube, vibration isolator, expansion joint) and non-metallic tube used in the refrigerant circuits of refrigerating systems and heat pumps. It also describes the requirements to qualify the tightness and permeability of non-metallic tubes (e.g., plastic) used in evaporating and/or condensing sides of refrigerating systems and heat pumps. This International standard does not apply to flexible pipes that are only occasionally stressed beyond the elastic limit (e. g., during repair work), or to joints that are free to rotate or hinge.