PD 6493:1991
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
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Guidance on methods for assessing the acceptability of flaws in fusion welded structures
Hardcopy , PDF
15121999
English
30081991
Committees responsible
Foreword
Section 1. General
0 Introduction
1 Scope
2 References
3 Notation
4 Types of flaw
5 Modes of failure
6 Information required for assessment
Section 2. Assessment for fracture
7 General
8 Data required for assessment
9 Parameters required for different assessment levels
(and methods)
10 Level 1, preliminary assessment
11 Level 2, normal assessment
12 Level 3, advanced assessment
13 Fracture assessment for nonplanar flaws, imperfect
shape and fillet welds
Section 3. Assessment for fatigue
14 Assessment procedures
15 Data required for assessment
16 Probability of survival
17 General procedure for fracture mechanics assessment
of planar flaws
18 Basis of procedure for assessing flaws using quality
categories
19 Assessment of planar flaws using quality categories
20 Assessment of embedded nonplanar flaws using
quality categories
21 Assessment of shape imperfection using quality
categories
22 Estimation of tolerable sizes of flaws
Section 4. Assessment for other modes of failure
23 Yielding due to overloading of remaining cross
section
24 Leakage in pressure, liquid or vacuum containing
equipment
25 Environmental effects
26 Instability (buckling)
27 Creep
Appendices
A Safety factors, number of tests and treatment of
variability in input data for fracture assessment
B Use of Charpy tests to indicate fracture toughness
levels
C Assessment of popin crack extensions
D Stress due to misalignment
E Stress intensity factor solutions for cracks in
welded joints
F Formulae for effective net section stress
G Examples of level 3 assessment diagrams
H Approximate numerical integration methods
J References
Tables
1 Limits for slag inclusions and porosity
2 Stress ranges used in fatigue assessments
3 Details of quality category SN curves
4 Minimum values of delta sigma j for assessing non
planar flaws and shape imperfections
5 Limits for nonplanar flaws in aswelded steel and
aluminium alloy weldments
6 Limits for nonplanar flaws in steel weldments
stress relieved by postweld heat treatment
7 Acceptance levels for misalignment expressed in
terms of stress magnification factor, Km
8 Acceptance levels for weld toe undercut in material
thicknesses from 10 mm to 25 mm
9 Procedure for assessment of known flaws
10 Temperature below which creep is negligible in
200 000 h
11 Equivalent fracture toughness values to the minimum
of three results
12 Definitions of failure consequences
13 Partial safety factors for fracture assessments at
level 2
14 Formulae for calculating the secondary bending
stress due to misalignment in butt joints
15 Formulae for calculating the secondary bending
stress due to misalignment in cruciform joints
16 Values of v and w for axial and bending loading
Figures
1 Schematic representation of stress distributions
across section
2 Alternative procedure for resolving flaws normal to
principal stress
3 Linearization of stress distributions
4 Typical distributions of residual stresses at welds
5 Flaw dimensions
6 Planar flaw interactions
7 Elliptical integral phi as a function of a/c used
for calculation of K1 for surface and embedded flaws
8 Stress intensity magnification factor Mm for
embedded flaws in tension (at point nearest material
surface)
9 Stress intensity magnification factor Mm for surface
flaws in tension
10 Stress intensity magnification factor Mb for
embedded flaws in bending
11 Stress intensity magnification factor Mb for surface
flaws in bending
12 Calculation of rho, the plasticity correction
factor, using above equations and rho1 from graph
13 Failure assessment diagrams
14 Relationship between actual flaw dimensions and the
parameter a for surface flaws
15 Relationship between actual flaw dimensions and the
parameter a for embedded flaws
16 Values of constant C for different loading
condition (level 1)
17 Stress/endurance relationship
18 Assessment of surface flaws in axiallyloaded
material for simplified procedure
19 Assessment of surface flaws in flat material in
bending for simplified procedure
20 Assessment of embedded flaws in axiallyloaded
joints for simplified procedure
21 Assessment of weld toe flaws in axiallyloaded
joints for simplified procedure
22 Assessment of weld toe flaws in joints in bending
for simplified procedure
23 Interaction criteria for slag inclusions
24 Schematic diagrams of typical relationships between
crack velocity and stress intensity factor during
stress corrosion cracking
25 Types of corrosion fatigue crack growth behaviour
26 Determination of the temperature To at which 0.2 %
creep strain is accumulated at a stress level equal
to the 'proof strength'
27 Determination of the time t(T) to achieve an
accumulated creep strain of 0.2 % at a stress level
equal to the 'proof strength'
28 Procedure for obtaining lower bound Klc toughness
estimates from Charpy impact test
29 Load/clip gauge displacement diagram for fracture
tests showing behaviour to be assessed for popin
30 Crack and welded joint geometries
31 Transverse loadcarrying cruciform joint
32 Example of level 3 assessment diagram for carbon
steel having stated stress/strain curves
33 Example of level 3 assessment diagram for quenched
and tempered steel having stated stress/strain
curves
34 Example of level 3 assessment diagram for austenitic
stainless steel having stated stress/strain curves
Simplified treatment of use of fracture mechanics methods to establish acceptance levels based on fitness for purpose. Applies basically to fusion welded joints in ferritic steels, austenitic steels and aluminium alloys.
Committee 
WEE/37

DevelopmentNote 
SUPERSEDES PD 6493:1980.

DocumentType 
Standard

Pages 
122

PublisherName 
British Standards Institution

Status 
Superseded

SupersededBy 
EN 100021 : 2001  METALLIC MATERIALS  TENSILE TESTING  PART 1: METHOD OF TEST AT AMBIENT TEMPERATURE 
BS 39231:1986  Methods for ultrasonic examination of welds Methods for manual examination of fusion welds in ferritic steels 
BS 54006:1980  Steel, concrete and composite bridges Specification for materials and workmanship, steel 
BS 36881:1963  Methods for mechanical testing of metals at elevated temperatures. Tensile testing 
BS 54003:1982  Steel, concrete and composite bridges Code of practice for design of steel bridges 
ISO 75396:2011  Corrosion of metals and alloys Stress corrosion testing Part 6: Preparation and use of precracked specimens for tests under constant load or constant displacement 
BS 39232:1972  Methods for ultrasonic examination of welds Automatic examination of fusion welded butt joints in ferritic steels 
ISO 75391:2012  Corrosion of metals and alloys — Stress corrosion testing — Part 1: General guidance on testing procedures 
BS 540010(1980) : 1980  STEEL CONCRETE AND COMPOSITE BRIDGES  PART 10: CODE OF PRACTICE FOR FATIGUE 
BS 26002:1973  Radiographic examination of fusion welded butt joints in steel Methods for steel over 50 mm up to and including 200 mm thick 
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