ARTICLE D-9
ATTACHMENTS AND SUPPORTS
AD-900 GENERAL REQUIREMENTS
(a) Supports, lugs, brackets, stiffeners, and other
attachments may be welded or stud bolted to the outside
or inside of a vessel wall. All stud bolted attachments
require a detailed fatigue analysis in accordance with
the requirements of Appendices 4 and 5 unless the
conditions of AD-160 are met. Attachments shall con-
form reasonably to the curvature of the shell to which
they are to be attached.
(b) Resistance welded studs may be used for minor
nonpressure attachments only to materials other than
those listed in Table AQT-1 and are prohibited for use
with materials listed in Table AQT-1.
(c) Other types of welds are illustrated in Fig. AD-
912.1 and limitations are given in AD-911 and AD-
912. Minimum weld sizes for the various types shall
conform to Fig. AD-912.1 except for welds covered
by AD-901.1.
(1) All welds joining nonpressure parts to pressure
parts shall be continuous except as permitted in (2)
below. Fillet or partial penetration welds where permit-
ted shall be continuous on all sides.
(2) Welds joining minor attachments
1
to pressure
parts constructed of materials other than those listed
in Table AQT-1 need not be continuous.
(3) Attachments may be welded directly to weld
deposit cladding without restriction.
For clad construction where design credit is taken
for cladding thickness, attachment may be made directly
to the cladding for loadings producing primary stresses
in the attachment weld not exceeding 10% of the design
stress intensity value of the attachment or the cladding
material, whichever is less; for higher loadings there
shall be sufficient attachment welding either directly
to the base metal or to weld overlay cladding to develop
the strength for the primary stress loadings (portions
1
Parts of small size (not over
3
⁄
8
in. thick or 5 cu in. volume)
carrying no load or insignificant load requiring no stress calculation
in designer’s judgment, such as nameplates, insulation supports, and
locating lugs.
137
of weld not required for strength, e.g., for weld continu-
ity or sealing, may be welded directly to the cladding).
For other integral clad construction the preceding
practice is a recommended guide with due consideration
to the degree of assurance of the lining bond and the
desired reliability of performance in service.
For applied linings, attachments should generally be
made directly to the base metal or to weld overlay
cladding; careful analysis and tests should be made to
establish the adequacy and reliability of attachment
before making any attachments directly to the lining
(successful experience with similar linings in compara-
ble service may provide a basis for judgment).
(d) For postheat treatment after welding, the fabrica-
tion requirements of the vessel base metal apply.
AD-901 Materials for Attachments to Pressure
Parts
Those attachments welded directly to pressure parts
shall be of a material listed in Part AM. See AF-623
for limitations for quenched and tempered materials.
Exceptions to the material requirements of AF-623.1
are given in the next paragraph. The material and the
deposited weld metal shall be compatible with that of
the pressure part.
Lightly loaded attachments, as defined in AD-912(a),
of nonhardenable austenitic stainless steels conforming
to either SA-240, SA-312, or SA-479 are permitted to
be fillet welded to pressure parts conforming to either
SA-353, SA-553 Type 1 and Type 2, or SA-645.
AD-901.1 Materials for Minor Attachments to
Pressure Parts. Except as limited by AF-623 or for
forged fabrication, AF-741, where no welding is permit-
ted, minor attachments
1
may be of noncertified material
and may be welded directly to the pressure part pro-
vided:
(a) the material is identified and is suitable for
welding;
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