328.5.3 Seal Welds. Seal welding shall be done by
a qualified welder. Seal welds shall cover all exposed
threads.
328.5.4 Welded Branch Connections
(a) Figures 328.5.4A through 328.5.4E show acceptable
details of branch connections with and without
added reinforcement, in which the branch pipe is connected
directly to the run pipe. The illustrations are
typical and are not intended to exclude acceptable types
of construction not shown.
(b) Figure 328.5.4D shows basic types of weld attachments
used in the fabrication of branch connections.
The location and minimum size of attachment welds
shall conform to the requirements herein. Welds shall
be calculated in accordance with para. 304.3.3 but shall
be not less than the sizes shown in Fig. 328.5.4D.
(c) The nomenclature and symbols used herein and
in Fig. 328.5.4D are:
tc p lesser of 0.7Tb or 6 mm (1⁄4 in.)
Tb p nominal thickness of branch
Th p nominal thickness of header
Tr p nominal thickness of reinforcing pad or saddle
t min. p lesser of Tb or Tr
(d) Branch connections, including branch connection
fittings (see paras. 300.2 and 304.3.2), which abut the
outside of the run or which are inserted in an opening
in the run shall be attached by fully penetrated groove
welds. The welds shall be finished with cover fillet
welds having a throat dimension not less than tc. See
Fig. 328.5.4D sketches (1) and (2).
(e) A reinforcing pad or saddle shall be attached to
the branch pipe by either:
(1) a fully penetrated groove weld finished with
a cover fillet weld having a throat dimension not less
than tc; or
(2) a fillet weld having a throat dimension not
less than 0.7t min.. See Fig. 328.5.4D sketch (5).
(f) The outer edge of a reinforcing pad or saddleshall be attached to the run pipe by a fillet weld having
a throat dimension not less than 0.5Tr . See Fig. 328.5.4D
sketches (3), (4), and (5).
(g) Reinforcing pads and saddles shall have a good
fit with the parts to which they are attached. A vent
hole shall be provided at the side (not at the crotch)
of any pad or saddle to reveal leakage in the weld
between branch and run and to allow venting during
welding and heat treatment. A pad or saddle may be
made in more than one piece if joints between pieces
have strength equivalent to pad or saddle parent metal,
and if each piece has a vent hole.
(h) Examination and any necessary repairs of the
completed weld between branch and run shall be made
before adding a pad or saddle.
328.5.5 Fabricated Laps. Figure 328.5.5 shows typical
fabricated laps. Fabrication shall be in accordance
with the applicable requirements of para. 328.5.4.
328.5.6 Welding for Severe Cyclic Conditions. A
welding procedure shall be employed which provides
a smooth, regular, fully penetrated inner surface.
328.6 Weld Repair
A weld defect to be repaired shall be removed to
sound metal. Repair welds shall be made using a
welding procedure qualified in accordance with para.
328.2.1, recognizing that the cavity to be repaired may
differ in contour and dimensions from the original joint.
Repair welds shall be made by welders or weldingoperators qualified in accordance with para. 328.2.1.
Preheating and heat treatment shall be as required for
the original welding. See also para. 341.3.3.
330.1 General
Preheating is used, along with heat treatment, to
minimize the detrimental effects of high temperature
and severe thermal gradients inherent in welding. The
necessity for preheating and the temperature to be
used shall be specified in the engineering design and
demonstrated by procedure qualification. The requirements
and recommendations herein apply to all types
of welding including tack welds, repair welds, and seal
welds of threaded joints.
330.1.1 Requirements and Recommendations. Required
and recommended minimum preheat temperatures
for materials of various P-Numbers are given in
Table 330.1.1. If the ambient temperature is below 0°C
(32°F), the recommendations in Table 330.1.1 become
requirements. The thickness intended in Table 330.1.1
is that of the thicker component measured at the joint.
330.1.2 Unlisted Materials. Preheat requirements for
an unlisted material shall be specified in the WPS.
330.1.3 Temperature Verification
(a) Preheat temperature shall be checked by use of
temperature indicating crayons, thermocouple pyrometers,
or other suitable means to ensure that the temperature
specified in the WPS is obtained prior to and
maintained during welding.
(b) Thermocouples may be temporarily attached directly
to pressure containing parts using the capacitor
discharge method of welding without welding procedure
and performance qualifications. After thermocouples are
removed, the areas shall be visually examined for
evidence of defects to be repaired.
330.1.4 Preheat Zone. The preheat zone shall extend
at least 25 mm (1 in.) beyond each edge of the weld.
330.2 Specific Requirements
330.2.3 Dissimilar Materials. When materials having
different preheat requirements are welded together,
it is recommended that the higher temperature shown
in Table 330.1.1 be used.
330.2.4 Interrupted Welding. If welding is interrupted,
the rate of cooling shall be controlled or other
means shall be used to prevent detrimental effects in
the piping. The preheat specified in the WPS shall be
applied before welding is resumed.
331 HEAT TREATMENT
Heat treatment is used to avert or relieve the detrimental
effects of high temperature and severe temperature
gradients inherent in welding, and to relieve residual