Pocket Guide to Flan..

common in 150-1b and 300-1b classes. Heavier rat-
ings are ~/4-in. raised faces. A ring type joint is
available in all classes, but more common in the
600-1b and greater classes.
5. Bore (also known as the nominal wall thickness of
matching pipe)--the measure of the flange wall
thickness, which matches the inside dimension of
the pipe being used.
6. Material designation--ASTM specifications that
describe the raw materials from which the flange is
made, such as ingots, blooms, billets, slabs, or
bars.
7. Ring gasket number--used when the flange face is
a ring type joint style.
8. Heat number or code--the batch number used by
steel forgers to identify a particular batch number
of steel forgings and test results. The mill test re-
sults are made available to the purchasers of the
flanges.
Flange Bores
Weldneck and socket weld flanges are drilled (ma-
chined) with the wall thickness of the flange having the
same dimensions of the matching pipe. The lighter the
pipe is, the larger the bore; conversely, the heavier the
pipe, the smaller the bore.
Other flanges are drilled to match the outside diameter
of pipe sizes, and do not have bore markings to indicate
a pipe schedule.
6