Hello Patrick and all,

You may want to take a look at the "engineeringtoolbox.com" site. More to the point of the topic you may want to look at the information regarding the B31 Codes for Pressure Piping on this page:

http://www.engineeringtoolbox.com/17_39.html

While you are there look around, as this site seems to have lots of general information for engineers of all disciplines.

Best regards, John.