DIN 906 specifies dimensions and technical delivery conditions for pipe plugs which are intended to be screwed into holes with parallel thread as specified in DIN 13 Part 12, DIN 158, DIN 3858 or ISO 228 Part 1. Since tightness is a function of pressure, temperature, the materials Involved and the fluid with which the threaded parts are in contact, such connections cannot be assurned to be tight. Therefore, it is recommended that a sealant or seal ring should be provided where the hole has a thread as specified in DIN 13 Part 12.
Note For pipe plugs for use in gas and water supply systems, see Technische Regeln für Gasinstallationen (DVGW Code of practice for gas supply installations) 1) and DIN 1988 Part 2.