HG/T 20584-2011 (HG/T 20584-2020 Newer Version) PDF English
HG/T 20584-2011 (HG/T20584-2011, HGT 20584-2011, HGT20584-2011)
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Technical requirements of fabrication for steel chemical vessels
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HG/T 20584-2011: PDF in English (HGT 20584-2011) HG/T 20584-2011
CHEMICAL INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
Record number: J1202-2011
Replacing HG 20584-1998
Technical requirements of fabrication
for steel chemical vessels
ISSUED ON: MAY 18, 2011
IMPLEMENTED ON: JUNE 01, 2011
Issued by: Ministry of Industry and Information Technology of the PRC
Table of Contents
1 Scope ... 6
2 Normative references ... 7
3 Terms and definitions ... 9
4 General ... 10
5 Manufacture used raw materials ... 11
6 Fabrication and forming ... 19
7 Welding and cutting ... 23
8 Post welding stress relief heat treatment ... 31
9 Size tolerances ... 36
10 Bolts and screw holes ... 45
11 Test and examination ... 48
12 Surface treatment, painting, packing and transportation ... 51
Annex A (Informative) Leakage test for pressure vessels by using ammonia
... 54
Annex B (Informative) Leakage test for pressure vessels by using helium . 60
Annex C (Informative) Leakage test for pressure vessels by using halogen . 71
Annex D (Informative) Commonly equipment used anticorrosion painting ... 77
Annex E (Informative) Fundamental standards of bolts, studs and nuts ... 88
Explanation of Provisions ... 90
2 Normative references
The following documents are indispensable for the application of this document.
For the dated references, only the editions with the dates indicated are
applicable to this Standard. For the undated references, the latest edition
(including all the amendments) are applicable to this Standard.
“Steel Pressure Vessels” GB 150
“General Purpose Metric Screw Threads - Basic Dimensions” GB/T 196
“General Purpose Metric Screw Threads - Tolerances” GB/T 197
“Steel Plates for Boilers and Pressure Vessels” GB 713
“Double end studs (clamping type) - Product grade B” GB/T 901
“Designation system for fasteners” GB/T 1237
“Tolerances for fasteners - Bolts, screws, studs and nuts” GB/T 3103.1
“Methods of Radiographic Testing and Classification of Radiographs for Steel
Castings” GB/T 5677
“Fasteners - Surface discontinuities - Bolts, screws and studs for general
requirements” GB/T 5779.1
“Fasteners - Surface discontinuities - Nuts” GB/T 5779.2
“Fasteners - Surface discontinuities - Bolts, screws and studs for special
requirements” GB/T 5779.3
“Rust grades and preparation grades of steel surfaces before application of
paints and related products” GB/T 8923
“General Purpose Metric Screw Threads - Limits of Sizes for the Screw
Threads of Medium Quality and Preferable Plan” GB/T 9145
“Methods of Liquid Penetrant Testing and Classification of Indication for Steel
Castings” GB/T 9443
“The Methods for Magnetic Particle Testing and for Specifying Quality Levels
of Steel Castings” GB/T 9444
“Specification for Welding of Stainless Steel clad Steel Plate” GB/T 13148
“Specification of Design Base for Steel Chemical Vessels” HG/T 20580
3 Terms and definitions
In addition to the terms and definitions given in “Steel Pressure Vessels” GB
150, for the purposes of this Standard, the following terms and definitions apply.
3.0.1 Simulated post welding heat treatment
USE the testing plate or the materials of testing pieces to simulate all post
welding heat treatment processes below the phase transformation point Ac1
and above 480°C experienced by the material during the actual manufacturing
process. It is divided into simulated short-period post welding heat treatment
and simulated long-period post welding heat treatment.
3.0.2 Simulated short-period post welding heat treatment
USE the testing plate or the materials of testing pieces to simulate one post
welding heat treatment period below the phase transformation point Ac1 and
above 480°C experienced by the material during the actual manufacturing
process.
3.0.3 Simulated long-period post welding heat treatment
USE the testing plate or the materials of testing pieces to simulate all post
welding heat treatment processes below the phase transformation point Ac1
and above 480°C experienced by the material during the actual manufacturing
process, including one or multi-rework post welding heat treatments. At least
one times of post welding heat treatment shall be reserved for the user’s future
applying.
3.0.4 Vessel axis
It refers to a straight line perpendicular to the reference surface center.
5 Manufacture used raw materials
5.0.1 The raw materials used for the pressure parts of pressure vessels shall
meet the following requirements.
1 Requirements of design documents.
2 “Steel Pressure Vessels” GB 150.
3 “Specification of Materials Selection for Steel Chemical Vessels” HG/T
20581.
4 Corresponding requirements of this Standard.
5.0.2 The materials used for the non-pressure parts of pressure vessels shall
meet the following requirements.
1 When the material is welded with a pressure part, its mechanical properties
and chemical composition shall be near to those of the material of the
pressure part.
2 Though it is not welded with a pressure part, when it is necessary to use a
welded joint, it shall be a steel with a good welding performance.
5.0.3 The manufacturing plant shall, according to the requirements of Article
5.0.1 of this Standard, carry out examination and acceptance, if necessary,
reinspection for the incoming materials.
If the performance data of the material required according to Article 5.0.1 of this
Standard are incomplete, the manufacturing plant shall carry out reinspection
or supplementary examinations. Only after the materials are qualified, can they
be put into use.
5.0.4 If the manufacturing organization of materials does not carry out the
nondestructive testing according to Article 5.0.1 of this Standard, the
manufacturing plant shall carry out the testing for supplement. Unless otherwise
stated in the design documents, the nondestructive testing method and its
grading for the steels used for pressure parts shall be carried out according to
the requirements of Table 5.0.4-1. The qualification grade, if the design has no
special requirement, shall comply with the requirements of Table 5.0.4-2 ~ Table
5.0.4-5.
Table 5.0.4-2 -- Qualification grade of ultrasonic testing for steel plates
and tubes
Material variety Ultrasonic
Carbon and low-
alloy steel plates
for pressure
vessels
Standard: 4.1 of JB/T 4730.3
Application scope: 6~250mm (in thickness)
Qualification grade: Commonly-used carbon and low-alloy steel plates,
Grade III
The carbon and low-alloy steel plates with a thickness
greater than or equal to 12m for the following pressure
vessel shells shall not be less than Grade II:
Inner-cylinder steel plates and hardened and tempered
steel plates for single-layer and multi-layer high
pressure vessels with p≥10.0MPa
Pressure vessels used for holding mediums of
extremely and highly destructive toxicity
Pressure vessels used in wet hydrogen sulfide
corrosion environment
Clad steel plates
Standard: 4.4 of JB/T 4730.3
Application scope: Clad steel plates for pressure equipment whose
substrates are greater than or equal to 6mm in
thickness
Qualification grade: Clad plates for tube plates, Grade I
Clad steel plates for hot-pressed heads and pressure
vessels, Grade II
Commonly-used clad plates, Grade III
Carbon and low-
alloy steel
seamless tubes
Standard: 4.5 of JB/T 4730.3
Application scope: Carbon and low-alloy steel seamless tubes whose
outside diameter is 12~660mm, and wall thickness is
greater than or equal to 2mm
Qualification grade: Grade II (p< 10.0MPa)
Grade I (p≥10.0MPa)
Austenitic
stainless steel
seamless tubes
Standard: 4.5 of JB/T 4730.3
Application scope: Austenitic seamless tubes whose outside diameter is
12~400mm, and wall thickness is 2~35mm
Qualification grade: Grade II (p< 10.0MPa)
Grade I (p≥10.0MPa)
Note: The magnetic particle testing for the surface of high pressure seamless steel tubes
shall comply with Grade I in 4.9 of JB 4730.4.
in the assessment
frame
the assessment
frame
Austenitic
steel
forgings
for
pressure
vessels
Standard: 4.7 of JB/T
4730.3
Requirements: As above
Quality grading: According
to the
provisions of
JB/T 4728
Table 5.0.4-5 -- Qualification grade of nondestructive testing for castings
Material
variety Radiographic Ultrasonic Magnetic particle Penetrant
Carbon
steel
castings
Standard: GB/T 5677
Requirements: The surface of
castings shall
be clean.
According to
the casting
process and
application
conditions, the
critical section
is determined.
Qualification grade: Grade III
Standard: JB/ZQ 6109
Requirements: Heat
treatment
before flaw
detection.
Surface
roughness
Ra≤12.5μm
Qualification grade: Grade
III
Standard: GB/T 9444
Requirements:
Delivery
condition; surface
roughness Ra
≤25μm
Qualification grade:
Same as that of
the penetrant
testing. Spot,
spot-linear, and
linear
discontinuities
shall not be
greater than
Grade III. No
crack is allowed.
Standard: GB/T 9443
Requirements: Delivery
condition;
surface
roughness
Ra≤50μm
Qualification grade:
1) USE a
105mm×148mm
rectangular frame
as the assessment
frame
2) Spot, spot-linear,
and linear
discontinuities
shall not be
greater than Grade
III. No crack is
allowed.
5.0.5 The surface quality of the steel plates for pressure parts shall meet all the
following requirements. The surface quality of steel plates used in a
manufactured vessel shall also meet the following requirements.
1 It is allowed that the surface of a steel plate has partial discontinuities such
as scratches, roll marks, pocks, and coarseness due to mill scale drops
whose depth does not exceed half of the negative thickness tolerance and
shall not be less than the minimum allowable thickness.
2 Discontinuities unsatisfactory to the above mentioned depth requirement
and any tension fracture, bubble, crack, scab, wrinkle, press-in mill scale,
diameters which are at 90° to each other shall not exceed 0.1% of the
design inside diameter of this section.
2 If the thickness of forgings, in some partial areas, is less than the design
thickness, but there is sufficient thickness in the adjacent area around the
areas, and the requirements for opening reinforcement according to “Steel
Pressure Vessels” GB 150 can be met, the forgings are allowed to be used,
without undergoing repair welding.
3 It is allowed that the surface of forgings has surface discontinuities such as
double skins, scabs, cutter marks whose depth does not exceed either 5%
of the nominal thickness or 1.5mm (whichever is smaller) and length does
not exceed 20mm (except for the machined surface of the forging).
However, any discontinuities like cracks which are of sharp cut shall be
removed regardless of their depth, length, and size.
4 The surface discontinuities which do not meet the requirement of the last
item shall be removed through polishing and shall be smoothly transited
with the base metal, with a gradient not larger than 1:3.
5 After removing the discontinuities, the residual thickness shall not be less
than the design thickness. If the residual thickness is not sufficient, it shall
use the method of Item 2 of this Article to carry out reinforcement
calculation. It shall meet the requirements, otherwise repair welding shall
be carried out.
6 The repair welding for forgings shall be carried out according to
corresponding requirements of repair welding process. If the depth of
repair welding exceeds 1/3 of the nominal wall thickness or 10mm, or the
area of repair welding exceeds 10% of the total area of forgings, the
forgings are not allowed to undergo repair welding.
5.0.7 Requirements of surface quality for the pressure parts of castings.
1 The surface quality of castings shall meet the requirements specified in the
drawing.
2 It is allowed that the casting surface has discontinuities (except cracks) of
which the depth does not exceed 20% of the nominal wall thickness and
the thickness of discontinuity-free parts is not less than the wall thickness
required by the strength design. The length of allowable discontinuities
shall meet the requirements of Table 5.0.7.
6 Fabrication and forming
6.0.1 For the materials used for the manufacturing of pressure parts, before
cutting or fabrication, their designation shall be transferred. It shall ensure that
the transferred designation is correct, clear, and durable. Stainless steel
pressure vessels with anticorrosive requirements, on their anticorrosive surface,
it shall not adopt embossed stamp and corrosive writing materials for
designation. The pressure parts of low temperature pressure vessels shall not
adopt embossed stamp designation.
6.0.2 The hot/cold stamping shall be carried out using mould other than local
heating and hammer hitting. For the manufacturing of cylinder’s pressure parts,
the rolling direction shall be identical to that of plate materials.
6.0.3 For those which meet one of the following conditions, they shall undergo
heat treatment after forming, so as to remove fabrication stress and improve
plasticity.
1 Where the deformation rate of cold/warm-formed cylinders (austenite
stainless steel: 15%, carbon and low-alloy steels and other materials: 5%)
or the thickness δs of steel plates meets the following conditions.
1) The thickness of carbon and Q345R steels is not less than 3% of the
cylinder’s inside diameter Di;
2) The thickness of other low-alloy steels is not less than 2.5% of the
cylinder’s inside diameter Di;
3) The thickness of austenitic stainless steels is not less than 15% of the
cylinder’s inside diameter Di.
2 The heads which meet one of the following conditions shall undergo heat
treatment after forming.
1) The carbon and low-alloy steel cold-formed heads shall undergo heat
treatment. When the manufacturing organization guarantees that the
cold-formed material property meets the design and utilization
requirements, and it is approved by the design organization, heat
treatment may be omitted;
2) The deformation rate of cold-formed austenitic stainless steel heads is
greater than 15%.
The deformation rate of fabrication for steel plates shall be calculated
according to the following method:
6.0.5 Heat treatment for materials.
1 Steels used in hot rolling conditions, after their hot-fabrication finished, may
generally be used during fabricating.
2 Steels used in normalized conditions, provided the final temperature of hot-
fabrication can be controlled to be higher than the normalizing temperature
of the steel or the test plate after hot-fabrication is judged as qualified, may
not undergo the subsequent normalizing treatment.
3 For steels used in normalizing+tempering conditions, if the above-
mentioned requirements for normalized steels can be met in the process
of hot-fabrication, after the hot-fabrication, it may only be tempered.
4 Steels used in quenched and tempered conditions, after their hot-
fabrication finished, shall generally undergo quenching and tempering.
5 For austenitic stainless steels, the final temperature of the hot-fabrication
shall be controlled above 850°C. After the fabrication, the steels shall be
rapidly cooled (e.g. blow or water spray cooling). If the materials are
required to undergo intergranular corrosion tendency test, after hot-
fabrication, they shall be reassessed. If the intergranular corrosion test
requirements are not met after hot-fabrication, it shall carry out solution or
stabilizing treatment.
6.0.6 The hot-fabrication for austenitic stainless steels shall meet the following
requirements.
1 Before heating, oil stains and other attachments shall be thoroughly
removed from the surface.
2 In the heating process, it shall not directly contact with the flame or solid
fuel; the heating temperature shall be uniform.
3 The furnace atmosphere shall be controlled to be of neutrality or micro-
oxidizability. Attentions shall be drawn to the sulfur content of furnace
atmosphere, to prevent the corrosion of sulfur on stainless steel.
6.0.7 The surface of stainless steel equipment, during fabricating, shall be
prevented from scratches. The stainless steel surface shall also be prevented
from iron contamination caused by fabrication appliances according to “Detailed
Management Rules for Manufacturing of Austenitic Stainless Steel Pressure
Vessels” HG/T 2806. Tools used for carbon steel pieces, such as abrasion
wheel, shall not be applied to stainless steel equipment.
6.0.8 Subplate and reinforcing plate on shells shall be provided with at least 1
7 Welding and cutting
7.1 Cutting
7.1.1 When using flame cutting for blanking, it shall remove slags and
detrimental impurities, and use abrasion wheels or other tools to fabricate the
grooves to be flat and smooth, until they expose metallic luster. When the
materials to be cut are high strength steels or chrome-molybdenum alloy steels
whose lower limit of tensile strength is larger than or equal to 540MPa as
specified in the standard, it shall use polishing or machining method to remove
the heat affected zone and quenched zone from the surfaces of flame cutting,
and shall carry out magnetic particle or penetrant testing.
The cutting of stainless steels is not allowed to adopt carbon arc air gouging,
shall adopt mechanical method or plasma cutting.
7.1.2 The necessity to preheat for flame cutting shall comply with the preheating
requirements for steels welding.
7.1.3 For the gas cutting of pressure parts, their opening edges and blanking
end of shearing (the opening edge of abutting nozzle or the end of inward
extended nozzle) shall be formed by means of polishing and grinding and shall
expose metallic luster.
7.2 Weld position
7.2.1 The openings on a shell shall avoid welds and their neighboring areas as
much as possible unless one of the following cases is met.
1 Openings which meet the opening reinforcement requirements of “Steel
Pressure Vessels” GB 150 are allowed to be in weld areas.
2 Openings which are allowed to omit separate reinforcement as specified in
“Steel Pressure Vessels” GB 150 are allowed to be in circumferential weld
areas. However, at this time, the welding joints within a circle, which is
centered at the opening center in a radius of 1.5 times of the opening
diameter, shall undergo 100% radiographic or ultrasonic testing and meet
the requirements. Welds which may be removed due to openings may be
free from the influence of nondestructive testing quality.
3 For the openings which are allowed to omit separate reinforcement as
specified in “Steel Pressure Vessels” GB 150, when the shell plate is less
than or equal to 40mm in thickness, the distance between the opening
edge and the main weld edge shall be larger than or equal to 13mm.
However, if the main weld meets relevant requirements after undergoing
7.4 General requirements for welding
7.4.1 Welding generally adopts electric-arc welding. Unless otherwise specified
in the design documents, the welding consumables shall be selected according
to “Specification of Materials Selection for Steel Chemical Vessels” HG/T 20581.
However, the manufacturing plant, under the premise of meeting the
requirements of sections 8.5~8.8 of “Specification of Materials Selection for
Steel Chemical Vessels” HG/T 20581 and the technical requirements specified
in design documents, is allowed to change the welding method and
consumables adopted.
7.4.2 The structure form and size of weld shall comply with “Specification for
Structural Design of Steel Chemical Vessels” HG/T 20583 and the drawing.
However, the manufacturing plant, under the premise of ensuring the welding
quality and not changing the dominant mode of joint, is allowed to properly
revise the size of welding groove. If the major item of joint dominant mode
specified in the drawing needs to be modified, it shall obtain the consent of the
design organization in advance.
7.4.3 The pre-weld preheating temperature of carbon and low-alloy steels may
refer to the corresponding provisions of “Specification of Materials Selection for
Steel Chemical Vessels” HG/T 20581. The preheating temperature specified in
“Specification of Materials Selection for Steel Chemical Vessels” HG/T 20581
is generally applicable to manual electric-arc welding. For submerged-arc
welding and argon-arc welding, it is allowed to adopt a lower preheating
temperature. Where the position is highly-restraint and the construction is taken
place in winter (below 5°C), it shall adopt a higher preheating temperature,
properly expand the preheating area and extend the preheating time.
7.4.4 The preheating scope shall cover a width of 3-fold plate thickness
respectively at both sides of the joint center and shall not be less than 100mm.
7.4.5 Measurement of preheating temperature.
1 At the back of steels’ heating surface, it shall measure the temperature. If
it is impractical, REMOVE the heating source at first; after the temperature
in the thickness direction of steels turns uniform, MEASURE the
temperature. The time for temperature homogenization is calculated
according to the ratio of 2min required per 25mm of base metal thickness.
2 Location of temperature measurement point.
1) When the weldment thickness is less than or equal to 50mm, the
temperature measurement point shall be located at 4-fold thickness of
base metals at both sides of weld and not exceeding 50mm;
3 Requirement of the analysis on chemical composition for the surface layer:
SAMPLE within 2mm downwards from the surfacing thickness as specified
in the drawing for chemical analysis. It shall meet the requirements of the
design documents.
4 Requirement of the analysis on chemical composition for the surfacing
layer: SAMPLE within 2mm downwards from the surfacing thickness as
specified in the drawing for analysis. It shall also meet the requirements of
the design documents.
5 Requirement of penetrant testing: It shall, according to “Nondestructive
Testing of Pressure Equipment” JB/T 4730.5, carry out the penetrant
testing of surfacing surface. It shall meet the following requirements.
1) No crack and flake are allowed;
2) No linear discontinuity is allowed;
3) Round discontinuity: d≤3.0mm, and no more than 2 in the assessment
area;
4) Discontinuity indication less than 0.5mm in size is not accounted for.
6 Requirement of side bending test.
1) TAKE 2 side bending samples parallel to the surfacing direction of
surface layer and 2 samples in the perpendicular direction, or 4
samples perpendicular to the surfacing direction;
2) The width of side bending sample is the thickness of base layer plus
surfacing layer. The maximum width is 40mm. It shall reserve the
thickness of surfacing layer as much as possible. The sample thickness
is 10mm;
3) On the basis of d=4a, CARRY out the 180° bend test. After bending, it
shall be free from cracks greater than 1.5mm. At the fusion line, there
shall be no cracking discontinuities greater than 3mm.
7 If necessary, the heat affected zone HV≤350 of surfacing may be taken as
additional testing requirement.
7.5.4 If the base layer weld undergoes surfacing, after the surfacing, it shall
carry out the radiographic testing. However, when the following conditions are
met, the base layer weld may be subjected to radiographic testing only before
surfacing.
1 The surfacing layer is not reckoned in the thickness of strength calculation.
from the steel surface; then shall be polished to be flat and smooth or be
fabricated into a smooth convex with a gradient not larger than 1:3 and a
height below 1.5mm.
7.6.2 Repair welding for forgings.
1 In case of any of the following items, after repair welding, it shall carry out
post welding stress relief heat treatment.
1) Where any thickness of the forging material is required to undergo post
welding stress relief heat treatment;
2) Where the depth of repair welding exceeds 6mm, or the single repair
welding area exceeds 3750mm2 (excluding Item 6 of Article 8.0.2 in this
Standard).
2 The surface after repair welding shall undergo magnetic particle or
penetrant testing, and radiographic or ultrasonic testing provided one of
the following conditions exists.
1) The depth of repairing welding exceeds 10mm;
2) Where the area of repair welding exceeds 3750mm2, and after the
repair welding, the post welding stress relief heat treatment is required
to be carried out.
7.6.3 Repair welding for castings.
1 After the casting discontinuities have been removed, the surface to be
repair-welded must undergo magnetic particle or penetrant testing, to
verify that the discontinuities have been removed completely.
2 The casting, after repair welding, shall undergo magnetic particle or
penetrant testing. Where the depth of repair welding exceeds either 10mm
or 20% of the cross section’s thickness (whichever is smaller), it shall carry
out the radiographic testing.
3 When the repair welding for castings is carried out after the heat treatment,
after repair welding, it shall carry out the post welding stress relief heat
treatment (excluding Item 6 of Article 8.0.2 in this Standard).
7.6.4 Repair welding for steel plates.
1 Where the depth of repair welding exceeds 4mm, after the repair welding,
it shall carry out the radiographic testing: For the high strength steels and
chrome-molybdenum alloy steels whose lower limit of tensile strength is
larger than or equal to 540MPa as specified in the standard, their repair
8 Post welding stress relief heat treatment
8.0.1 The post welding stress relief heat treatment for pressure parts shall
comply with the relevant requirements of “Steel Pressure Vessels” GB 150.
8.0.2 The thickness of post welding stress relief heat treatment shall be
determined according to the following requirements.
1 The thickness of base metal at the thinner side of butt joint (excluding the
weld reinforcement).
2 The shell thickness when the shell is welded to the tube plate, flat head,
and other similar parts.
3 The shell thickness when it is welded to the nozzle; but for abutting nozzle,
it refers to the thinner of the thickness of the nozzle or the shell.
4 The nozzle thickness when the nozzle is butted with the flange.
5 The weld thickness when the non-pressure parts are welded to the
pressure parts.
6 Weld depth of repair welding.
Note: 1 The repair welding of low carbon steel, C-Mn steel, Q370R and their welds may
be carried out after the final stress relief heat treatment and before the final
water pressure test. No additional post welding heat treatment is required. But
it shall meet the following requirements and make records:
The medium applied is not extremely or highly detrimental. The design
temperature of vessel exceeds -20°C.
The depth of repair welding does not exceed that specified in “Steel Pressure
Vessels” GB 150.
Before the repair welding, discontinuities shall be removed completely; the
crater shall undergo magnetic particle or penetrant testing.
It shall adopt the low-hydrogen electrode and rigorously enforce the drying
and heat preservation measures.
It shall adopt the welding process which has passed the evaluation. The
repair welding area shall be pre-heated according to Item 4 of Article 7.6.1
in this Standard. The preheating temperature and interlayer temperature are
not less than 100°C.
The width of weld bead for repair welding is not less than 4-fold electrode
diameter.
After the cooling of the surface of repair welding, it shall carry out the
magnetic particle or penetrant testing. Where the depth of repair welding
exceeds 4mm, the radiographic or ultrasonic testing shall be carried out in
addition.
2 The vessel after the pressure-tight test, after repair welding, shall be subjected
to a pressure-tight test again.
For the small-area repair welding of which the depth is not larger than 2mm,
and the surface dose not directly contact to the medium (such as the surface
repairing after the removing of clamping apparatus), the pressure-tight test may
be omitted.
7 The thickness of base layer for the steels with surfacing layers, the
thickness of base layer of austenitic stainless steel lining, or the thickness
of base layer of clad steel plate.
8 The weld thickness when the heat exchange tube is welded to the tube
plate.
9 The throat thickness of fillet weld. The greater one of the throat thickness
of fillet weld or groove depth when the fillet weld and groove weld are
applied simultaneously.
8.0.3 The temperature of post welding stress relief heat treatment shall be
selected according to Table 8.0.3-1 and shall meet the following requirements.
1 “Recommended temperature for post welding stress relief heat treatment”
of Table 8.0.3-1 refers to the temperature range recommended for final
post welding stress relief heat treatment of welding joints in normal
conditions.
2 “Post welding stress relief heat treatment temperature for clad steel plates”
of Table 8.0.3-1 is applicable to the post welding stress relief heat
treatment for those whose base material is the material listed and clad
material is austenitic stainless steel.
3 Welding joints of the steels belong to group No. 1, 2, 3, and 5 of Table
8.0.3-1, when processed according to “Recommended temperature for
post welding stress relief heat treatment”, are allowed to adopt the post
welding stress relief heat treatment system of reduced temperature and
prolonged heat preservation time of Table 8.0.3-2.
Note: The values in brackets are only applicable to the low carbon steel and Q345R of No.
1 in Table 8.0.3-1.
6 When local heating is adopted for the post welding stress relief heat
treatment, it shall meet the following requirements.
1) Longitudinal welds are not allowed to adopt partial heat treatme......
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