Before machining a flange face back to working condition you must be able to identify the specification of the flange that is to be machined. On the outside diameter of the base of each flange you should be able to find a stamp containing the following information:
- Manufacturer's name.
- Nominal pipe size (NPS).
- Pressure rating (150 lb., 300 lb., etc.)
- Face designation - the machined gasket surface.
- Bore - the nominal pipe size (NPS).
- Material designation
- Ring gasket number - used for ring joint flange.
- Heat number of code - the batch number used when forged and tested
Each flange should have been hard stamped with clear recessed markings. In circumstances where the identifcation markings cannot be easily read, the flange must be measured by hand, including taking measurements of the bolt sizes, the pipe size and the number of bolts.
Image credit: Piping Designer