GENERAL NOTE:
(A) PWHT is not mandatory for P-No. 4 material under the following conditions:
(1) welds in pipe or attachment welds to pipe complying with all of the following conditions:
(A) a nominal material thickness of /2 In. (13.0 mm) or less;
(B) a specified carbon content of the material to be welded of 0.15% or less;
CC) application of 250'F 120°C) minimum preheat during welding.
(2) for seal welding of threaded or other mechanical joints provided:
(A) the seal weld has a throat thickness of 31a in. (9.0 mm) or less;
(B) a minimum preheat of 250°F (120 0
C) Is maintained during welding.
(3) Attachmentwelds fornon-load-carrying attachments provided in additionto (A)(2) and (A)(3) above:
(A) stud welds or fillet welds made by the SMAW or GTAW process shall be used;
(B) the hardened portion of the heat affected zone (HAZ) shall not encroach on the minimum wall
thickness of the pipe, as determined by welding procedure qualification using the maximum
welding heat Input. The depth of the HAZ shall be taken as the point where the HAZ hardness
does not exceed the average unaffected base metal hardness by more than 10%.
(C) If SMAW is used, the electrode shall be the low hydrogen type;
(D) the thickness of the test plate used in making the welding procedure qualification of Section IX
shall not be less than that of the material to be welded;
(E) the attachment weld has a throat thickness of 3/16 in. or