Dear All members

These days I am confusing about the counterboring in ASME Sec.III.

I understand that the requirement of ASME Sec.III NB-4250(c) is ruled for the length of the counterboring if the pipe or components are conterbored.

Is my understanding correct?

thanks

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NB-4250      WELDING END TRANSITIONS —
MAXIMUM ENVELOPE

The welding ends of items shall provide a gradual change  in  thickness  from  the  item  to  the 
adjoining item. Any welding end transition which lies entirely within the envelope shown in Fig.
NB-4250-1 is accept- able provided:
(a) the wall thickness in the transition region is not less than the minimum wall thickness of the
adjoining pipe;
(b) sharp  reentrant  angles  and  abrupt  changes  in slope in the transition region are avoided.
When the included angle between any two adjoining surfaces of a taper transition is less than 150
deg., the intersection or corner (except for the weld reinforcement) shall be provided with a
radius of at least 0.05tmin; and
(c) if  the  weld  is  subject to  preservice inspection,
the  length of the  counterbore shall be 2tmin  for  pipe and tmin  for components and fittings, as
shown in Fig.
NB-4250-2 or Fig. NB-4250-3.