ISO International Standard

ISO 13971:2012 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.

ISO 13971:2012 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.

ISO 13971:2012 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.