Explains 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 of non-metallic tubes (e.g. plastic) used in evaporating and/or condensing sides of refrigerating systems and heat pumps.