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Tuesday, 6 May 2008

Fittings, Bends, Miters, Laps and Branch Connections ASME B31.3 Process Piping

306 FITTINGS, BENDS, MITERS, LAPS, AND
BRANCH CONNECTIONS
Fittings, bends, miters, laps, and branch connections
may be used in accordance with paras. 306.1 through
306.5. Pipe and other materials used in such components
shall be suitable for the manufacturing or fabrication
process and the fluid service.

306.1 Pipe Fittings
306.1.1 Listed Fittings. Listed fittings may be used
in Normal Fluid Service in accordance with para. 303.

306.1.2 Unlisted Fittings. Unlisted fittings may be
used only in accordance with para. 302.2.3.

306.1.3 Specific Fittings
(a) Proprietary welding branch outlet fittings which
have been design proof tested successfully as prescribed
in ASME B16.9, MSS SP-97 or the BPV Code, Section VIII,
Division 1, UG-101 may be used within their established
ratings.
(b) The lap thickness of a proprietary “Type C” lapjoint
stub-end buttwelding fitting shall conform to the
requirements of para. 306.4.2 for flared laps.

306.1.4 Fittings for Severe Cyclic Conditions
(a) Only the following fittings may be used under
severe cyclic conditions:
(1) forged
(2) wrought, with factor Ej ≥ 0.90,8 or
(3) cast, with factor Ec ≥ 0.908
(b) Fittings conforming to MSS SP-43, MSS SP-119,
and proprietary “Type C” lap-joint stub-end welding
fittings shall not be used under severe cyclic conditions.

306.2 Pipe Bends
306.2.1 General
(a) A pipe bend made in accordance with paras.
332.2.1 and 332.2.2, and verified for pressure design in
accordance with para. 304.2.1, is suitable for the same
service as the pipe from which it is made.
(b) A pipe bend made in accordance with para.
332.2.2, but not meeting the flattening limits of para.
332.2.1, may be qualified for pressure design by para.
304.7.2 and shall not exceed the rating of the straight
pipe from which it is made.

306.2.2 Corrugated and Other Bends. Bends of other
designs (such as creased or corrugated) shall be qualified
for pressure design as required by para. 304.7.2.

306.2.3 Bends for Severe Cyclic Conditions. A pipe
bend designed as creased or corrugated shall not be
used under severe cyclic conditions.

306.3 Miter Bends
306.3.1 General. Except as stated in para. 306.3.2, a
miter bend made in accordance with para. 304.2.3 and
welded in accordance with para. 311.1 is suitable for
use in Normal Fluid Service.

306.3.2 Miter Bends for Category D Fluid Service. A
miter bend which makes a change in direction at a single
joint (angle _ in Fig. 304.2.3) greater than 45 deg, or is
welded in accordance with para. 311.2.1, may be used
only for Category D Fluid Service.

306.3.3 Miter Bends for Severe Cyclic Conditions. A
miter bend to be used under severe cyclic conditions
shall be made in accordance with para. 304.2.3 and
welded in accordance with para. 311.2.2, and shall have
an angle _ (see Fig. 304.2.3) ≤ 22.5 deg.

306.4 Laps
The following requirements do not apply to fittings
conforming to para. 306.1, specifically lap-joint stub ends
conforming to ASME B16.9, nor to laps integrally hotforged
on pipe ends, except as noted in paras. 306.4.3
and 306.4.4(a).

306.4.1 Fabricated Laps. A fabricated lap is suitable
for use in Normal Fluid Service, provided that all of the
following requirements are met.
(a) The outside diameter of the lap shall be within
the dimensional tolerances of the corresponding ASME
B16.9 lap-joint stub end.
(b) The lap thickness shall be at least equal to the
nominalwall thickness of the pipe to which it is attached.
(c) The lap material shall have an allowable stress at
least as great as that of the pipe.
(d) Welding shall be in accordance with para. 311.1
and fabrication shall be in accordance with para. 328.5.5.

306.4.2 Flared Laps. See para. 308.2.5 for requirements
of lapped flanges for use with flared laps. A flared
lap is suitable for use in Normal Fluid Service, provided
that all of the following requirements are met.
(a) The pipe used shall be of a specification and grade
suitable for forming without cracks, surface buckling,
or other defects.
(b) The outside diameter of the lap shall be within
the dimensional tolerances of the corresponding ASME
B16.9 lap-joint stub end.
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(c) The radius of fillet shall not exceed 3 mm (1⁄8 in.).
(d) The lap thickness at any point shall be at least
95% of the minimum pipe wall thickness T multiplied
by the ratio of the pipe outside diameter to the diameter
at which the lap thickness is measured.
(e) Pressure design shall be qualified as required by
para. 304.7.2.

306.4.3 Forged Laps. A lap integrally hot-forged on
a pipe end is suitable for Normal Fluid Service only
when the requirements of para. 332 are met. Its dimensions
shall conform to those for lap-joint stub ends given
in ASME B16.9.
306.4.4 Laps for Severe Cyclic Conditions
(a) A forged lap-joint stub end per para. 306.1 or a
lap integrally hot-forged on a pipe end per para. 306.4.3
may be used under severe cyclic conditions.
(b) A fabricated lap to be used under severe cyclic
conditions shall conform to the requirements of para.
306.4.1, except that welding shall be in accordance with
para. 311.2.2. A fabricated lap shall conform to a detail
shown in Fig. 328.5.5, sketch (d) or (e).
(c) A flared lap is not permitted under severe cyclic
conditions.

306.5 Fabricated Branch Connections
The following requirements do not apply to fittings
conforming to para. 306.1.

306.5.1 General. A fabricated branch connection
made and verified for pressure design in accordance
with para. 304.3, and welded in accordance with para.
311.1, is suitable for use in Normal Fluid Service.

306.5.2 Fabricated Branch Connections for Severe
Cyclic Conditions
. A fabricated branch connection to be
used under severe cyclic conditions shall conform to the
requirements of para. 306.5.1, except that welding shall
be in accordance with para. 311.2.2, with fabrication
limited to a detail equivalent to Fig. 328.5.4D sketch (2)
or (4), or to Fig. 328.5.4E.

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