First, 1G, 2G, 3G, etc. are "test" positions that may include one or more welding positions. Welding positions are shown in Table 4.9 as F, H, V, OH. So, a 3G plate test would qualify for welding the F, H or V portion of a pipe groove or fillet joint over 24 in. O.D. If the weld joint is oriented the same as a 2G or 1G rotated, then the welder is qualified for the entire circumference. If the weld joint is oriented the same as a 5G, then the welder is qualified for the vertical and flat portions, but not the overhead (bottom of pipe). Figures 4.1 and 4.2 attempt to show this, although they are tough to interpret.

If you look at TABLE 4.9 under Production Pipe Welding Qualified (Fillet),
it does not refer to the note 3, which restricts welding on pipe under 24 in. That is why I came to the conclusion that the pipe can be any diameter, as long as it is in positions qualified in this case F,H & V.

Is this a miss understanding and if so, where did you come up with your understanding. Thank You for your assistance.

I originally answered on another thread but found this here also. I agree with the above statemant about test positions vs. positions qualified. Looking at Table 4.9, I see:

(1) over 24 in., CJP & PJP (butt-groove), 1G Rotated & 2G... to this add vertical

(2) over 24 in., PJP (T,Y,K-groove) consider note 5, 1G Rotated & 2G... to this add vertical

(3) Any size, FILLET, 1F & 2F Rotated & 2F... to this add vertical

I would agree with your interpretation that any size pipe welded with a fillet weld is OK such as welding a base or cap plate on a pipe column or welding shear tabs on a pipe column. Diameter restrictions are on butt, TKY joints.

Also see Table 4.10 and notes. If the test coupon was 1", then the thickness is 1/8" to unlimited. If less than 1", then limited to 1/8" to 2T.