BS ISO 23467:2020 pdf free.Ice plug isolation of piping in nuclear power plant.
BS ISO 23467 1 Scope This document specifies requirements for the ice plug technique with liquid nitrogen or dry ice as refrigerant (cryogenic medium) on metal pipes of nuclear power plants. The freezing liquid can be water or water mixture (e.g. boric acid mixture). This document specifies technical requirements of ice plug generation, formation judgment and removal, measures before, during and after ice plugging and requirements for personnel and non- destructive testing. The application of the ice plug isolation technique is principally not allowed on cladded pipes or pipes with internal coatings. The application for pressure test is not in the scope of this document and will be qualified separately. The pipe shall be made of metal [carbon steel or stainless steel). Welds are not allowed in the area of the ice plug (no circumferential neither longitudinal weld). Unless it can be demonstrated that there is no
better solution, and that there are no defects in the welds, ice plug operations on welds can be done. Cast copper pipe, cast iron pipe, cladded pipe and lining pipe shall not be subject to ice plugging isolation. Material inspection certificate or alternative consideration should be confirmed in order to avoid low temperature brittle fracture, when applying ice plugs on carbon steel piping, which is connected to most important components or piping for safety.Vibration and external shock like falling parts (e.g. tools) or mechanical stress e.g. moving of valves, starting of pumps) shall be avoided during ice plug generation. In addition, stainless steel pipe shall be protected from contact with halogen-containing medium to prevent stress corrosion. If the distance between the ice plug from the weld and the pipe fttings or the ice plug and the closed end are not in accordance with this document, the distance can be used if it is verified by a mock- up test. For the distance, it is important that the needed NDT could be done in proper performance. BS ISO 23467 pdf download.