ASME Section VIII div 2 2010. ASME Boiler and Pressure Vessel Code. Alternative Rules
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2010 SECTION VIII, DIVISION 2
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particle or liquid penetrant method in accordance with Part 7. This requirement does not apply to
weld overlay.
2) When such surface weld metal buildup is used in welded joints that require radiographic
examination in accordance with Part 7, the weld metal buildup shall be included in this examination.
6.2.5 Miscellaneous Welding Requirements
6.2.5.1 Preparation of Reverse Side of Double-Welded Joints
The reverse side of double-welded joints shall be prepared by chipping, grinding, or melting out, so as to
secure sound metal at the base of the weld metal first deposited before applying weld metal from the reverse
side. These requirements are not intended to apply to any process of welding by which proper fusion and
penetration are otherwise obtained and by which the base of the weld remains free from impurities.
6.2.5.2 Aligning and Separating Components of Single-Welded Joints
If single-welded joints are used, the components to be joined shall be aligned and separated so that there will
be complete penetration and fusion at the bottom of the joint for its full length.
6.2.5.3 Peening
a) Weld metal and heat affected zones may be peened by manual, electric, or pneumatic means when it is
deemed necessary or helpful to control distortion, to relieve residual stresses, improve fatigue life, or to
improve the quality of the weld. Peening shall not be used on the initial (root) layer of weld metal or on
the final (face) layer unless the weld is subsequently postweld heat treated. In no case, however, is
peening to be performed in lieu of any postweld heat treatment required by these rules.
b) Controlled shot peening and other similar methods, which are intended only to enhance surface proper-
ties of the vessel or vessel parts, shall be performed after any nondestructive examinations and pressure
tests required by these rules.
6.2.5.4 Identification Markings or Records for Welders and Welding Operators
a) Each welder and welding operator shall stamp the identifying number, letter, or symbol, assigned by the
Manufacturer on or adjacent to and at intervals of not more than 0.9 m (3 ft.) along the welds they make
in plates 6 mm (0.25 in.) and over in thickness. Alternatively, a record shall be kept by the Manufacturer
of those employed on welding each joint that shall be made available to the Inspector.
b) If a multiple number of permanent nonpressure part load bearing attachment welds, non-load-bearing
welds, such as stud welds, or special welds, such as tube-to-tubesheet welds, are made on a vessel, the
Manufacturer need not identify the welder or welding operator that welded each individual joint provided:
1) The Manufacturer's Quality Control System includes a procedure that will identify the welders or
welding operators that made such welds on each vessel so that the Inspector can verify that the
welders or welding operators were all properly qualified; and
2) The welds in each category are all of the same type and configuration and are welded with the
same Welding Procedure Specification.
c) Permanent identification of welders or welding operators making tack welds that become part of the final
pressure weld is not required, provided the Manufacturer's Quality Control System includes a procedure
to permit the Inspector to verify that such tack welds were made by qualified welders or welding
operators.
6.2.5.5 Friction Welding Visual Examination
The welded joint between two members joined by the inertia and continuous drive friction welding processes
shall be a full penetration weld. Visual examination of the as-welded flash roll of each weld shall be made as
an in-process check. The weld upset shall meet the specified amount within ±10%. The flash shall be
removed to sound metal.
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6.2.5.6 Capacitor Discharge Welding
Capacitor discharge welding may be used for welding temporary attachments and permanent nonstructural
attachments without postweld heat treatment provided the following requirements are met.
a) The Welding Procedure Specification shall be prepared in accordance with Section IX, insofar as
possible describing the capacitor discharge equipment, the combination of materials to be joined, and
the technique of application. Qualification of the Welding Procedure is not required.
b) The energy output shall be limited to 125 W-sec.
6.2.5.7 Burr Grinding of Completed Weld Joints
Burr grinding of weld joints to improve fatigue life performance shall be in accordance with Figure 6.2 when
specified in the User's Design Specification. The remaining ligament after burr grinding ( i.e. t – g, see
Figure 6.2) shall be greater than or equal to the minimum required wall thickness for the component obtained
using Part 4 or Part 5, as applicable.
6.2.5.8 Corrosion Resistance of Alloy Welds
Alloy welds that are exposed to the corrosive action or environmental degradation of the contents of the
vessel should have a resistance to corrosion that is not substantially less than that of the base metal. The
use of filler metal that will deposit weld metal with practically the same composition as the material joined is
recommended. Alternatively, filler metal of a different composition may be used provided the strength of the
weld metal at the operating temperature is not appreciably less than that of the high alloy material to be
welded, and the user or an agent acting on behalf of the user is satisfied that its resistance to corrosion is
satisfactory for the intended service. The columbium content of weld metal shall not exceed 1.00%, except
that ENiCrMo-3, ERNiCrMo-3, and ENiCrMo-12 weld filler metal made to SFA-5.11 and SFA-5.14 may be
used to weld S31254, S31603, S31703, S31725, and S31726 to a maximum design temperature of 480°C
(900°F).
6.2.6 Summary of Joints Permitted and Their Examination
6.2.6.1 Types of Joints Permitted
The types of weld joints permitted for each Weld Category are given in paragraph 4.2.
6.2.6.2 Examination Requirements
Examination requirements shall be in accordance with Part 7.
6.2.7 Repair of Weld Defects
6.2.7.1 Removal of Unacceptable Defects
Unacceptable defects detected visually or by the examinations in Part 7, and defects detected by leakage
tests, shall be removed by mechanical means or by thermal gouging processes.
6.2.7.2 Re-welding of Areas to Be Repaired
The areas to be repaired shall be re-welded by qualified welders using qualified welding procedures.
6.2.7.3 Examination of Repaired Welds
Repaired welds shall be reexamined by the methods of the original examination of the weld. The repaired
weld shall not be accepted unless the examination shows the repair to be satisfactory.
6.2.7.4 Postweld Heat Treatment of Repaired Welds
The postweld heat treatment rules in paragraph 6.4 shall apply to all weld repairs.
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6.2.8 Special Requirements for Welding Test Plates for Titanium Materials
6.2.8.1 If a vessel of welded titanium contains Category A or B weld joints, then a production test plate of
the same specification, grade, and thickness shall be made of sufficient size to provide at least one face and
one root bend specimen or two-side bend specimens dependent upon plate thickness. Where longitudinal
joints are involved, the test plate shall be attached to one end of the longitudinal joint and welded continuously
with the joint. Where circumferential joints only are involved, the test plate need not be attached but shall be
welded along with the joint, and each welder or welding operator shall deposit weld metal in the test plate at
the location and proportional to that deposited in the production weld.
6.2.8.2 Test plates shall represent each welding process or combination of processes or a change from
machine to manual or vice versa. At least one test plate is required for each vessel, provided not over 30 m
(100 ft.) of Category A or B joints are involved. An additional test plate, meeting the same requirements as
outlined above, shall be made for each additional 30 m (100 ft.) of Category A or B joints involved. The bend
specimens shall be prepared and tested in accordance with Section IX, QW-160. Failure of either bend
specimen constitutes rejection of the weld.
6.3 Special Requirements for Tube-To-Tubesheet Welds
6.3.1 Material Requirements
Tubes may be attached to tubesheets by welding provided the tubes and tubesheets or tubesheet facings are
of weldable materials covered by this Division.
6.3.2 Holes in Tubesheets
6.3.2.1 Preparing Holes in Tubesheets
Tube holes in tubesheets shall be drilled full size or they may be punched to three-quarters size and then
drilled, reamed, or finished full size with a rotating cutter.
6.3.2.2 Clearance between Tubes and Tube Holes
The clearance between the outside surface of the tubes and the inside surfaces of the tube holes shall not
exceed the clearance used in the welding procedure qualification tests.
6.3.2.3 Finish of Holes
The edges of the tubesheet at the tube holes on the side to be welded shall be free of burrs, and the edges of
the tubesheet at the tube hole on the side opposite the weld shall have sharp corners removed. The
surfaces of tube holes in tubesheets shall have a workmanship-like finish.
6.3.3 Weld Design and Joint Preparation
The weld dimensions and weld detail, and joint preparation, if used, shall comply with the details included in
the Welding Procedure Specification.
6.3.4 Qualification of Welding Procedure
Tube-to-tubesheet welding procedure specifications shall be qualified in accordance with the requirements of
QW-193 of Section IX.
6.4 Preheating and Heat Treatment of Weldments
6.4.1 Requirements for Preheating of Welds
6.4.1.1 The Welding Procedure Specification for the material being welded shall specify the minimum
preheating requirements in accordance with the weld procedure qualification requirements of Section IX.
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Where preheating is not required by the welding procedure, preheating may be employed during welding to
assist in completion of the welded joint. The need for and temperature of preheat are dependent on a
number of factors, such as the chemical analysis, degree of restraint of the parts being joined, elevated
temperature physical properties, and material thicknesses.
6.4.1.2 Guidelines for preheating are provided in Table 6.7 for the materials listed by P-Numbers of
Section IX. It is cautioned that the preheating parameters shown in this table do not necessarily ensure
satisfactory completion of the welded joint, and requirements for individual materials for the P-Number listing
may have preheating requirements that are more restrictive.
6.4.2 Requirements for Postweld Heat Treatment
6.4.2.1 Before applying the detailed requirements and exemptions in these paragraphs, satisfactory
qualification of the welding procedures to be used shall be performed in accordance with all the variables of
Section IX and paragraph 6.3.4, including conditions of postweld heat treatment or its omission, and the
restrictions listed in this paragraph.
6.4.2.2 Postweld heat treatment requirements for all materials of construction are shown below.
a) Postweld heat treatment requirements for quenched and tempered high strength steel materials listed in
Table 3.A.4, are covered in paragraph 6.6.6.
b) Postweld heat treatment requirements for nonferrous materials are covered in paragraph 6.4.6.
c) 2¼Cr-1Mo-¼V and 3Cr-1Mo-¼V-B Materials – The final postweld heat treatment shall be in accordance
with the requirements of this Division for P-No. 5C materials.
d) 2¼Cr-1Mo Materials – The final postweld heat treatment temperature shall be in accordance with the
requirements of this Division for P-No. 5A materials, except that, for the materials listed in Table 3.1, the
permissible minimum normal holding temperature is 650
o
C (1200
o
F) and the holding time shall be 2.5
minutes/mm (1 hr/in.). For thicknesses over 125 mm (5 in.), the holding time shall be 5 hours plus 0.6
min for each additional mm (15 minutes for each additional inch) over 125 mm (5 in.).
e) Postweld heat treatment requirements for all other materials are covered in the tables listed below.
Except as otherwise provided in these tables, all welds in pressure vessels or pressure vessel parts shall
be given a postweld heat treatment at a temperature not less than that specified in the applicable table
based on the nominal thickness as defined in paragraph 6.4.2.7. The materials shown below are
identified by P-Numbers and Group Numbers in accordance with QW /QB-422 of Section IX and are
provided in Annex 3.A. for each material specification.
1) Table 6.8 – Materials P-No. 1, Group 1, 2, 3
2) Table 6.9 – Materials P-No. 3, Group 1, 2, 3
3) Table 6.10 – Materials P-No. 4, Group 1, 2.
4) Table 6.11 – Materials P-No. 5A, P-No. 5B Group 1, and P-No. 5C Group 1, P-No. 5B Group 2
5) Table 6.12 – Materials P-No. 6, Group 1, 2, 3
6) Table 6.13 – Materials P-No. 7, Group 1, 2 and P-No. 8
7) Table 6.14 – Materials: P-No. 9A, Group 1 and P-No. 9B, Group 1
8) Table 6.15 – Materials: P-No. 10A, Group 1; P-No. 10B, Group 2; P-No. 10C, Group 1, P-No. 10E,
Group 1; P-No. 10F, Group 6; P-No. 10G, Group 1; P-No. 10H, Group 1; P-No. 10I, Group 1; and
P-No. 10K, Group 1
9) Table 6.16 – Alternative Postweld Heat Treatment Requirements For Carbon And Low Alloy Steels
6.4.2.3 Additional postweld heat treatment requirements, other than those cited in paragraph 6.4.2.2.e,
may be mandatory based on the requirements of paragraph 3.11.
6.4.2.4 The exemptions from postweld heat treatment permitted in paragraph 6.4.2.2 are not permitted
when welding ferritic materials greater than 3 mm (1/8 in.) thick with the electron beam welding process, or
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when welding P-No 3, P-No 4, P-No 5A, P-No 5B, P-No 5C, P-No 6, P-No 7 (except for Type 405 and Type
410S), and P-No 10 materials using the inertia and continuous drive friction welding process.
6.4.2.5 When Holding Temperatures and Times May Be Exceeded
Except where prohibited in paragraph 6.4.2.2, holding temperatures and/or holding times in excess of the
minimum values given in these tables may be used. A time-temperature recording of all postweld heat
treatments shall be provided for review by the Inspector. The holding time at temperature specified in the
table references of paragraph 6.4.2.2 need not be continuous. It may be an accumulation of time of multiple
postweld heat treat cycles.
6.4.2.6 Heat Treatment of Pressure Parts Consisting of Different P-Number Groups
When pressure parts of two different P-Number groups are joined by welding, the postweld heat treatment
shall be that required by the material having the higher postweld heat treatment temperature. When
nonpressure parts are welded to pressure parts, the postweld heat treatment temperature of the pressure part
shall control.
6.4.2.7 Definition of Nominal Thickness Governing Postweld Heat Treatment
The nominal thickness as used in this paragraph is the thickness of the welded joint as defined below. For
pressure vessels or parts of pressure vessels being postweld heat treated in a furnace charge, it is the
greatest weld thickness in any vessel or vessel part which has not previously been postweld heat treated.
a) When the welded joint connects parts of the same thickness, using a full penetration butt weld, the
nominal thickness is the total depth of the weld exclusive of any permitted weld reinforcement.
b) For groove welds, the nominal thickness is the depth of the groove.
c) For fillet welds, the nominal thickness is the throat dimension. If a fillet weld is used in conjunction with
a groove weld, the nominal thickness is the depth of the groove or the throat dimension, whichever is
greater.
d) For stud welds, the nominal thickness shall be the diameter of the stud.
e) When a welded joint connects parts of unequal thicknesses, the nominal thickness shall be the following:
1) The thinner of two adjacent butt welded parts including head to shell connections;
2) The thickness of the shell in connections to tubesheets, flat heads, covers, flanges, or similar
constructions;
3) For nozzles, the thickness of the weld across the nozzle neck or shell or head or reinforcing pad or
attachment fillet weld, whichever is the greater;
4) The thickness of the nozzle neck at the joint in nozzle neck to flange connections;
5) The thickness of the weld at the point of attachment when a nonpressure part is welded to a
pressure part;
6) The thickness of the weld in tube-to-tubesheet connections.
f) For repairs, the nominal thickness is the depth of the repair weld.
6.4.2.8 Heat Treatment of Electroslag Welds in Ferritic Materials
Electroslag welds in ferritic materials over 38 mm (1 1/2 in.) in thickness at the joint shall be given a grain
refining (austenitizing) heat treatment. For P-No.1 materials only, the heating and cooling rate restrictions of
paragraphs 6.4.4.b and 6.4.4.e do not apply when the heat treatment following welding is in the austenitizing
range.
6.4.3 Procedures for Postweld Heat Treatment
6.4.3.1 The postweld heat treatment shall be performed in accordance with one of the procedures of
paragraph 6.4.3.1 through 6.4.3.7. In the procedures that follow, the soak band is defined as the volume of
metal required to meet or exceed the minimum PWHT temperatures required in paragraph 6.4.2.2. As a
minimum, the soak band shall contain the weld, heat affected zone, and a portion of base metal adjacent to
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the weld being heat treated. The minimum width of this volume is the widest width of weld plus the nominal
thickness defined in paragraph 6.4.2.7 or 50 mm (2 in.), whichever is less, on each side or end of the weld.
For additional detail recommendations regarding implementation and performance of these procedures refer
to Welding Research Council (WRC) Bulletin 452, June 2000, “Recommended Practices for Local Heating of
Welds in Pressure Vessels”.
6.4.3.2 Heating Vessel in a Furnace in One Heat
Postweld heat treatment is performed by heating the vessel as a whole in a closed furnace. This procedure
is preferable and should be used whenever practicable.
6.4.3.3 Heating Vessel Portions in a Furnace in More Than One Heat
Postweld heat treatment is performed by heating the vessel in more than one heat in a furnace, provided the
overlap of the heated sections of the vessel is at least 1.5 m (5 ft.). When this procedure is used, the portion
outside of the furnace shall be shielded so that the temperature gradient is not harmful. The cross section
where the vessel projects from the furnace shall not intersect a nozzle or other structural discontinuity.
6.4.3.4 Heating Shell Sections, Heads, and Other Portions before Joining
Postweld heat treatment is performed by heating of shell sections, heads, and/or portions of vessels for
postweld heat treatment of longitudinal joints or complicated welded details before joining to make the
completed vessel. If it is not practical to postweld heat treat the complete vessel as a whole or in two or
more heats as provided in paragraph 6.4.3.3, then any circumferential joints not previously postweld heat
treated may be locally postweld heat treated by any appropriate means that will assure the required
uniformity. For such local heating, the soak band shall extend around the full circumference. The portion
outside the soak band shall be protected so that the temperature gradient is not harmful. This procedure
may also be used to postweld heat treat portions of new vessels after repairs subject to the owner/user’s
approval.
6.4.3.5 Heating Vessel Internally
Postweld heat treatment is performed by internally heating the vessel. The internal heating may be provided
by any appropriate means. Adequate indicating and recording temperature devices shall be utilized to aid in
the control and maintenance of a uniform distribution of temperature in the vessel wall. Previous to this
operation, the vessel shall be fully enclosed with insulating material.
6.4.3.6 Local Heating of Nozzles to Vessels and External Attachments
a) Local heating of nozzles and attachments shall be performed by heating a circumferential band
containing nozzles or other welded attachments that require postweld heat treatment in such a manner
that the entire band shall be brought up uniformly to the required temperature and held for the specified
time. Except as modified in the paragraph below, the soak band shall extend around the entire vessel
and shall include the nozzle or welded attachment.
1) The portion of the vessel outside of the circumferential soak band shall be protected so that the
temperature gradient is not harmful; this procedure may also be used for local heat treatment of
circumferential joints in pipe, tubing, or nozzle necks. In the latter case, proximity to the shell
increases thermal restraint, and the designer should provide adequate length to permit heat
treatment without harmful gradients at the nozzle attachment, or heat a full circumferential band
around the shell, including the nozzle.
2) The circumferential soak band width may be varied away from the nozzle or attachment weld
requiring PWHT, provided the required soak band around the nozzle or attachment weld is heated
to the required temperature and held for the required time. As an alternative to varying the soak
band width, the temperature within the circumferential band away from the nozzle or attachment
may be varied and need not reach the required temperature, provided the required soak band
around the nozzle or attachment weld is heated to the required temperature, held for the required
time, and the temperature gradient is not harmful throughout the heating and cooling cycle. The
portion of the vessel outside of the circumferential soak band shall be protected so that the
temperature gradient is not harmful.
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b) The procedure in paragraph 6.4.3.6.a may also be used to postweld heat treat portions of vessels after
repairs.
6.4.3.7 Local Area Heating of Double Curvature Heads or Shells
Postweld heat treatment is performed by heating a local area around nozzles or welded attachments in the
larger radius sections of a double curvature head or a spherical shell or head in such a manner that the area
is brought up uniformly to the required temperature and held for the specified time. The soak band shall
include the nozzle or welded attachment. The minimum soak band size shall be a circle whose radius is the
widest width of the weld attaching the nozzle, reinforcing plate, or structural attachment to the shell, plus the
nominal thickness as defined in paragraph 6.4.2.7, or 50 mm (2 in.), whichever is less. The portion of the
vessel outside of the soak band shall be protected so that the temperature gradient is not harmful.
6.4.3.8 Heating of Other Configurations
Postweld heat treatment performed by local area heating of other configurations such as “spot” or bulls eye”
local heating not addressed in paragraphs 6.4.3.2 through 6.4.3.7 is permitted provided that other measures
(based upon sufficiently similar documented experience or evaluation) are taken that consider the effect of
thermal gradients, all significant structural discontinuities (such as nozzles, attachments, head-to-shell
junctions), and any mechanical loads which may be present during PWHT. The portion of the vessel outside
of the soak band shall be protected so that the temperature gradient is not harmful. The soak band shall
include a circle that extends beyond the edges of the attachment weld in all directions by a minimum of the
nominal thickness defined in paragraph 6.4.2.7 or 50 mm (2 in.), whichever is less.
6.4.4 Operation of Postweld Heat Treatment
The operation of postweld heat treatment shall be carried out by one of the procedures given in paragraph
6.4.3 in accordance with the following requirements.
a) When post weld heat treatment is performed in a furnace (see paragraph 6.4.3.2), the temperature of the
furnace shall not exceed 430°C (800°F) at the time the vessel or part is placed in it.
b) Above 430°C (800°F), the rate of heating shall be not more than 220°C/hr (400°F /hr) divided by the
maximum metal thickness of the shell or head plate in inches, but in no case more than 220°C/hr (400°F
/hr) and in no case need it be less than 56°C/hr (100°F/hr). During the heating period there shall not be
a greater variation in temperature throughout the portion of the vessel being heated than 140°C (250°F)
within any 4.6 m (15 ft) interval of length.
c) The vessel or vessel part shall be held at or above the temperature specified in paragraph 6.4.2 for the
period of time specified in this paragraph. During the holding period, there shall not be a difference
greater than 85°C (150°F) between the highest and lowest temperatures throughout the portion of the
vessel being heated, except where the range is further limited in paragraph 6.4.2.
d) When post weld heat treatment is performed in a furnace (see paragraph 6.4.3.2), during the heating and
holding periods, the furnace atmosphere shall be so controlled as to avoid excessive oxidation of the
surface of the vessel. The furnace shall be of such design as to prevent direct impingement of the flame
on the vessel.
e) Above 430°C (800°F), cooling shall be done at a rate not greater than 280°C/hr (500°F/hr) divided by the
maximum metal thickness of the shell or head plate in inches, but in no case need it be less than 55°C/hr
(100°F/hr). From 430°C (800°F), the vessel may be cooled in still air.
6.4.5 Postweld Heat Treatment after Repairs
6.4.5.1 Except as permitted in paragraph 6.4.5.2 below, vessels or parts of vessels that have been
postweld heat treated in accordance with the requirements of paragraph 6.4 shall again be postweld heat
treated after welded repairs have been made.
6.4.5.2 Weld Repairs Made after Postweld Heat Treatment
Weld repairs to P-No.1 Gr. Nos. 1-3 materials and to P-No. 3 Gr. Nos. 1-3 materials, and to the weld metals
used to join these materials, may be made after the final PWHT but prior to the final hydrostatic test without
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additional PWHT provided that all the requirements below are satisfied. The welded repairs shall meet the
requirements shown below. These requirements do not apply when the welded repairs are minor
restorations of the material surface such as those required after the removal of construction fixtures and
provided that the surface is not exposed to the vessel contents.
a) PWHT is not a service requirement defined by the user.
b) The material is not required to be impact tested to quality toughness properties in accordance with
paragraph 3.11.
c) The Manufacturer shall give prior notification of the repair to the user or to his designated agent and shall
not proceed until acceptance has been obtained. Such repairs shall be recorded on the Data Report.
d) The total repair depth shall not exceed 38 mm (1 1/2 in.) for P-No. 1 Gr. Nos. 1-3 materials and 16 mm
(5/8 in.) for P-No. 3 Gr. Nos. 1-3 materials. The total depth of a weld repair shall be taken as the sum of
the depths for repairs made from both sides of a weld at a given location.
e) After removal of the defect, the groove shall be examined, using either the magnetic particle or liquid
penetrant examination methods in accordance with Part 7.
f) In addition to the requirements of Section IX for qualification of Welding Procedure Specifications for
groove welds, the following requirements shall apply.
1) The weld shall be deposited by the manual shielded metal arc process using low hydrogen
electrodes. The electrodes shall be properly conditioned in accordance with Section II, Part C,
SFA-5.5. The maximum bead width shall be four times the electrode core diameter.
2) For P-No. 1 Gr. Nos. 1-3 materials, the repair area shall be preheated and maintained at a minimum
temperature of 95°C (200°F) during welding.
3) For P-No. 3 Gr. Nos. 1-3 materials, the repair weld method shall be limited to the SMAW half bead
weld repair and weld temper bead reinforcement technique. The repair area shall be preheated
and maintained at a minimum temperature of 175°C (350°F) during welding. The maximum
interpass temperature shall be 230°C (450°F). The initial layer of weld metal shall be deposited
over the entire area using 3 mm (1/8 in.) maximum diameter electrodes. Approximately one-half
the thickness of this layer shall be removed by grinding before depositing subsequent layers. The
subsequent weld layers shall be deposited using 4 mm (5/32 in.) maximum diameter electrodes in
such a manner as to ensure tempering of the prior weld beads and their heat affected zones. A
final temper bead weld shall be applied to a level above the surface being repaired without
contacting the base material but close enough to the edge of the underlying weld bead to ensure
tempering of the base material heat affected zone. After completing all welding, the repair area
shall be maintained at a temperature of 205°C (400°F) to 260°C (500°F) for a minimum of 4 hours.
The final temper bead reinforcement layer shall be removed substantially flush with the surface of
the base material.
g) After the finished repair weld has reached ambient temperature, it shall be examined using the magnetic
particle or liquid penetrant examination methods in accordance with Part 7. If the examination is by
magnetic particle method, only the alternating current yoke type is acceptable. For P-No. 3 Gr. No.3
materials, the examination shall be made after the material has been at ambient temperature for a
minimum period of 48 hours to determine the presence of possible delayed cracking of the weld. In
addition, welded repairs greater than 10 mm (3/8 in.) deep in materials, and in welds that are required to
be examined using the radiographic method in accordance with Part 7, shall be examined using the
radiographic method in accordance with Part 7.
h) The vessel shall be hydrostatically tested after making the welded repair.
6.4.6 Postweld Heat Treatment of Nonferrous Materials
6.4.6.1 Postweld heat treatment of nonferrous materials is normally not necessary nor is it desirable.
Except as required in paragraphs 6.4.6.2, 6.4.6.3, and 6.4.6.4, postweld heat treatment shall not be
performed except by agreement between the purchaser and the Manufacturer. The temperature, time and
method of heat treatment shall be covered by agreement.
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6.4.6.2 If welded, castings of SB-148, Alloy CDA 954 shall be heat treated after all welding at
620°C-640°C (1150°F-1200°F) for 1.5 hours for the 25 mm (1 in.) of cross section thickness plus 0.5 hour for
each additional 25 mm (1 in.) of section thickness. The material shall then be air cooled.
6.4.6.3 Within 14 days after welding, all products of zirconium Grade R60705 shall be heat treated at
500°C-610°C (1000°F-1100°F) for a minimum of 1 hour for thicknesses up to 25 mm (1 in.) plus 0.5 hour for
each additional 25 mm (1 in.) of thickness. Above 430°C (800°F) cooling shall be done at a rate not greater
than 280°C/hr (500°F/hr) divided by the maximum metal thickness of the shell or head plate in inches but in
no case more than 280°C/hr (500°F /hr). From 430°C (800°F), the vessel may be cooled in still air.
6.4.6.4 Postweld Heat Treatment of UNS Numbers N08800, N08810 and N08811 Alloys.
a) Pressure boundary welds and welds to pressure boundaries in vessels with design temperatures above
540°C (1000°F) fabricated from UNS No. N08800 (Alloy 800), UNS No. N08810 (Alloy 800H), or UNS
No. N08811 (Alloy 800HT) shall be postweld heat treated. The postweld heat treatment shall consist of
heating to a minimum temperature of 885°C (1625°F) for 1.5 hours for thicknesses up to 25 mm (1 in.),
and for 1.5 hours plus 0.04 hr/mm (1 hr/in.) of thickness for thicknesses in excess of 25 mm (1 in.).
Cooling and heating rates shall be by agreement between the purchaser and Manufacturer. As an
alternative, solution annealing in accordance with the material specification is acceptable. Postweld
heat treatment of tube-to-tubesheet and expansion bellows attachment welds is neither required nor
prohibited.
b) Except as permitted in paragraph 6.4.6.4.c, vessels or parts of vessels that have been postweld heat
treated in accordance with the requirements of this paragraph shall again be postweld heat treated after
welded repairs have been made.
c) Weld repairs to the weld metal and heat affected zone in welds joining these materials may be made
after the final PWHT, but prior to the final hydrostatic test, without additional PWHT. The weld repairs
shall meet the requirements shown below.
1) The Manufacturer shall give prior notification of the repair to the user or to his designated agent and
shall not proceed until acceptance has been obtained.
2) The total repair depth shall not exceed 13 mm (1/2 in.) or 30% of the material thickness, whichever
is less. The total depth of a weld repair shall be taken as the sum of the depths for repairs made
from both sides of a weld at a given location.
3) After removal of the defect, the groove shall be examined. The weld repair area must also be
examined using the liquid penetrant method in accordance with Part 7.
4) The vessel shall be hydrostatically tested after making the welded repair.
6.5 Special Requirements For Clad or Weld Overlay Linings, and Lined Parts
6.5.1 Materials
6.5.1.1 Integral or Weld Metal Overlay Clad Base Material or Parts
Integral or weld metal overlay clad base material or parts having applied corrosion resistant linings shall
conform to the requirements of paragraph 3.3.6. For the purposes of this Paragraph, the term corrosion
resistant includes, but is not limited to, cladding, weld overlay, hard facing, etc., where welding is used to
deposit the material.
6.5.1.2 Inserted Strips in Clad Materials
The nominal thickness of inserted strips used to restore cladding at joints shall be equal to the nominal
thickness of cladding specified for the plates, backed if necessary with corrosion resistant weld metal
deposited in the groove to bring the insert flush with the surface of the adjacent cladding. When insert strips
are used, the cladding shall not be considered part of the shell for strength purposes.
2010 SECTION VIII, DIVISION 2
6-22
6.5.1.3 Weld Metal Composition
Welds that are exposed to the corrosive action of the contents of the vessel should have a resistance to
corrosion that is not substantially less than that of the corrosion resistant integral or weld metal overlay
cladding or lining. The use of filler metal that will deposit weld metal with practically the same composition as
the material joined is recommended. By agreement between the user and Manufacturer, a weld metal of
different composition may be used provided it has better mechanical properties and its resistance to corrosion
is satisfactory for the intended service.
6.5.2 Joints In Corrosion Resistant Clad or Weld Metal Overlay Linings
The types of joints and welding procedures used shall be selected to minimize the formation of brittle weld
composition that may result from the mixture of the corrosion resistant alloy and base material.
NOTE: Because of the different thermal coefficients of expansion of dissimilar metals, caution should be
exercised in design and construction under provisions of these paragraphs in order to avoid difficulties in
service under extreme temperature conditions or with unusual restraint of parts such as may occur at points of
stress concentration.
6.5.3 Welding Procedures
Welding procedures for corrosion resistant clad and weld overlay linings shall be prepared and qualified in
accordance with the requirements of Section IX.
6.5.4 Methods to Be Used In Attaching Applied Linings
Applied linings may be attached to the base material and other parts by any method and process of welding
that is not excluded by the rules of this Division.
6.5.5 Postweld Heat Treatment of Clad and Lined Weldments
6.5.5.1 Requirements When Base Metal Must Be Postweld Heat Treated
a) Vessels or parts of vessels constructed of corrosion resistant integral or weld metal overlay clad, or
applied corrosion resistant lining material shall be postweld heat treated when the base material is
required to be postweld heat treated. In applying this requirement, the thickness used to determine the
need for postweld heat treatment shall be the total thickness of the base material.
b) When the thickness of the base material requires postweld heat treatment, it shall be performed after the
application of corrosion resistant weld metal overlay cladding or applied corrosion resistant lining unless
exempted by paragraph 6.4.2.2.
6.5.5.2 Requirements When Base Metal or Lining Is Chromium Alloy Steel
Vessels or parts of vessels constructed of chromium alloy stainless steel clad base material and those lined
with chromium alloy stainless steel applied linings shall be postweld heat treated in all thicknesses, except
that vessels clad or lined with Type 405 or Type 410S and welded with an austenitic electrode or
non-air-hardening nickel-chromium-iron electrode need not be postweld heat treated unless required by
paragraph 6.5.5.1.
6.5.6 Requirements for Base Material With Corrosion Resistant Integral or Weld Metal Overlay
Cladding
6.5.6.1 Procedure Qualification for Groove Welds in Base Material with Corrosion Resistant Integral or
Weld Metal Overlay Cladding
The requirements in Section IX, for procedure qualification shall be followed.
6.5.6.2 When the Integral or Weld Metal Overlay Cladding Thickness is Included in Design Thickness
The welding procedure for groove welds in integral or weld overlay shall be qualified as provided in paragraph
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