redandysafc;
The P-No classification was established by ASME Boiler and Pressure Vessel Code, SC IX to group metals having similar weldability characteristics.

The S-No was developed for metals that were not endorsed by ASME Boiler and Pressure Vessel Code, SC II. Again, the same premise applies regarding S-No classification as P-No classification.

The F-No is a classification for filler metals, similar to P and S-No classification.

The A-No define chemical composition for various filler metals and was established by AWS, years ago.

metengr I am doing a project on welding procedures and I need to know if they stand for anything. Or a good websitye that might help me.

Ok. Here you go;

http://www.pnumbers.com/

The above will get you started. Get a copy of ASME Boiler and Pressure Vessel Code, Section IX, you should read Article 1 and 2.

We had a discussion on this at the ASME Section IX Subcommittee meeting a year or two ago. Dr. D'or Doty, who probably was the longest subcommittee member at that time said that the "P" originally designated materials approved for welded "pressure" applications.  The "S" numbers were developed sometime after P-Numbers and originally referred to materials approved by Code Cases for "structural" applications.  That description would no longer be correct today, as there are many S-number materials that are used for pressure applications, such as piping.

Thanks a lot you have really helped me there.Thanks Welder 4965 also thanks Metengr your hrlp is always appreciated