"R" Stamp - for the Repair and Alteration of Boilers and Pressure Vessels
Other Design, Piping, and/or Fabrication Codes include:
ASME B31.1 - Process Piping
NFPA 53 - Materials, Equipment, and Systems used in Oxygen Enriched Atmospheres.
NFPA 54/ANSI Z223.1 - National Fuel Gas Code
NFPA 86 - Standards for Ovens and Furnaces
CGA G-4.4 Oxygen Pipeline Systems