may be used, provided they are of the same nominal
composition as the filler metal, will not cause detrimental
alloying of the weld metal, and the welding procedure
using them is qualified as required by para. 328.2.
Some commonly used types are shown in Fig. 328.3.2.
328.4 Preparation for Welding
328.4.1 Cleaning. Internal and external surfaces to
be thermally cut or welded shall be clean and free
from paint, oil, rust, scale, and other material that
would be detrimental to either the weld or the base
metal when heat is applied.
328.4.2 End Preparation
(a) General
(1) End preparation is acceptable only if the surface
is reasonably smooth and true, and slag from
oxygen or arc cutting is cleaned from thermally cut
surfaces. Discoloration remaining on a thermally cut
surface is not considered detrimental oxidation.
(2) End preparation for groove welds specified in
ASME B16.25, or any other which meets the WPS,
is acceptable. [For convenience, the basic bevel angles
of ASME B16.25 and some additional J-bevel angles
are shown in Fig. 328.4.2 sketches (a) and (b).]
(b) Circumferential Welds
(1) If component ends are trimmed as shown in
Fig. 328.3.2 sketch (a) or (b) to fit backing rings or
consumable inserts, or as shown in Fig. 328.4.3 sketch
(a) or (b) to correct internal misalignment, such trimming
shall not reduce the finished wall thickness below
the required minimum wall thickness tm.
(2) Component ends may be bored to allow for
a completely recessed backing ring, provided the remaining
net thickness of the finished ends is not less
than tm.
(3) It is permissible to size pipe ends of the same
nominal size to improve alignment if wall thickness
requirements are maintained.
(4) Where necessary, weld metal may be deposited
inside or outside of the component to permit alignment
or provide for machining to ensure satisfactory seating
of rings or inserts.
(5) When a girth or miter groove weld joins
components of unequal wall thickness and one is more
than 11⁄2 times the thickness of the other, end preparation
and geometry shall be in accordance with acceptable
designs for unequal wall thickness in ASME B16.25.
328.4.3 Alignment
(a) Circumferential Welds
(1) Inside surfaces of components at ends to be
joined in girth or miter groove welds shall be aligned
within the dimensional limits in the WPS and the
engineering design.
(2) If the external surfaces of the components are
not aligned, the weld shall be tapered between them.
(b) Longitudinal Welds. Alignment of longitudinal
groove welds (not made in accordance with a standard
listed in Table A-1 or Table 326.1) shall conform to
the requirements of para. 328.4.3(a).
(c) Branch Connection Welds
(1) Branch connections which abut the outside
surface of the run pipe shall be contoured for groove
welds which meet the WPS requirements [see Fig.
328.4.4 sketches (a) and (b)].
(2) Branch connections which are inserted through
a run opening shall be inserted at least as far as the
inside surface of the run pipe at all points [see Fig.
328.4.4 sketch (c)] and shall otherwise conform to para.
328.4.3(c)(1).
(3) Run openings for branch connections shall
not deviate from the required contour more than the
dimension m in Fig. 328.4.4. In no case shall deviations
of the shape of the opening cause the root spacing
tolerance limits in the WPS to be exceeded. Weld
metal may be added and refinished if necessary for
compliance.
(d) Spacing. The root opening of the joint shall be
within the tolerance limits in the WPS.
328.5 Welding Requirements
328.5.1 General
(a) Welds, including addition of weld metal for
alignment [paras. 328.4.2(b)(4) and 328.4.3(c)(3)], shall
be made in accordance with a qualified procedure and
by qualified welders or welding operators.
(b) Each qualified welder and welding operator shall
be assigned an identification symbol. Unless otherwise
specified in the engineering design, each pressure containing
weld or adjacent area shall be marked with the
identification symbol of the welder or welding operator. In lieu of marking the weld, appropriate records shall
be filed
(c) Tack welds at the root of the joint shall be made
with filler metal equivalent to that used in the root
pass. Tack welds shall be made by a qualified welder
or welding operator. Tack welds shall be fused with
the root pass weld, except that those which have cracked
shall be removed. Bridge tacks (above the weld) shall
be removed.
(d) Peening is prohibited on the root pass and final
pass of a weld.
(e) No welding shall be done if there is impingement
on the weld area of rain, snow, sleet, or excessive
wind, or if the weld area is frosted or wet.
(f) Welding End Valves. The welding sequence and
procedure and any heat treatment for a welding end
valve shall be such as to preserve the seat tightness
of the valve.
328.5.2 Fillet and Socket Welds. Fillet welds (including
socket welds) may vary from convex to concave.
The size of a fillet weld is determined as shown in
Fig. 328.5.2A.
(a) Typical weld details for slip-on and socket weld ing flanges are shown in Fig. 328.5.2B; minimum
welding dimensions for other socket welding components
are shown in Fig. 328.5.2C or MSS SP-119.
(b) If slip-on flanges are single welded, the weld
shall be at the hub.
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.
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