Environmental Engineering Reference
In-Depth Information
be obtained by using both approaches, as reflected in the schemes of the
elements
B
and
B
1.
Element
C
lists the main criteria for selecting areas of inspection:
• special analysis of the component;
• identification of areas related to:
- critical defects
- acceptable defects
- efficiency of NDT
- frequency of NDT
- certification criteria.
It should be noted that the areas of inspection are selected exercised on
the basis of risk assessment presented in element
D
(Fig. 7.2). It is expected
that in most cases this process will be iterative, especially during the
initial phase of inspection based on risk information. This iterative process
provides feedback to the ISI for optimisation and efficiency confirmed by
the certificatin of inspection.
Element
C
1 (Fig. 7.5) shows the approximate strategy for selecting
areas of ISI together with realistic values of some important criteria. As an
example, the quantitative criteria are proposed for two main type of damage:
fatigue defects and discontinuities. In the case of fatigue defects the zone
Operat-
ing
exper-
ience
Required
regulation
of organ
Fatigue
analysis
Other
damage
Fracture mechanics
analysis
Problem zones:
- all welds
- cast materials
- corner branches
- third part of crack
height (<1/2
t
and >1/4
t
)
- safety margins
Problem
zones:
F
u
< 0.5
F
a
> 1
ISI
Zone/efficiency
Synthesis of different
aspects:
• technical analysis
• radiation protection
• economic aspects
Sensitive
zones:
F
u
< 0.5
F
a
> 1
Sensitive zones:
-
a
max
= 20 mm
-
T
<
T
trans
-
J
< 50 kJ/m
2
; d
J
/d
a
< 20 MPa
-
L
r
> 1
Additional samples
7. 5
Example of the strategy for selecting areas for ISI (element
C
1):
F
u
- fatigue factor;
F
d
- fatigue factor for areas with crack-
like defects;
t
- wall thickness of the element;
a
- the depth of
the surface defect (crack);
T
- temperature;
T
trans
- ductile-brittle
transition temperature;
J
- fracture toughness; d
J
/d
a
- modulus
of ductile fracture resistance;
L
r
- reference stress - applied load/
limited load.
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