Fillet weld

Butt-welded joint, reducer, or weld-neck flange Double-welded slip-on flange Fillet welded joint or pocket-weld flange... 

Head attachment. UW-13. Fig. UW-13.1 Fillet welds. UW-18. UW-36 Table UW-12 Knuckle radius. UG 32. UCS-79 Torispherical head. Pressures. 

For the attachment of heads convex to pressure to shells not over A-in. required thickness, only with use of fillet weld on inside of shell or For attachment of heads having pressure on either side to shells not over 24-in. inside diameter and not over 11-in. required thickness with fillet weld on outside of head flange only. 

NOTE When the angle between members exceeds 105 deg, size is of less significance than effective throat (see also throat of a fillet weld). 

Fig. GR-3.4.4(a)j. The minimum weld reinforcement O.D. or I.D. shall be flush to the adjoining surfaces. For fillet welds and added reinforcement to nonbutt groove welds, height is measured from the theoretical throat [Fig. GR-3.4.7(a)[ internal protrusion does not apply. 

Fillet welds (including socket welds) may vary from convex to concave. The size of a fillet weld is determined as shown in Fig. GR-3.4.7(a). 

Equal Leg Fillet Weld [Note (1)] Unequal Leg Fillet Weld [Note (2)]... 

The size of an equal leg fillet weld is the leg length of the largest inscribed isosceles right triangle (theoretical throat = 0.707 X size). 

Structural attachments may be made by complete penetration, partial penetration, or fillet welds. 

---