5.2.2.1 Subject to the conditions
stated in 5.2.4, the wall thickness
of pipes should not be less than:
where:
|
t
o
|
= |
theoretical thickness |
|
t
o
|
= |
PD/(20Ke + P) (mm)
|
with:
|
P
|
= |
design
pressure (bar) referred to in 5.2.3
|
|
D
|
= |
outside
diameter (mm) |
|
K
|
= |
allowable
stress (N/mm2) referred to in 5.2.4
|
|
e
|
= |
efficiency
factor equal to 1.0 for seamless pipes and for longitudinally or spirally
welded pipes, delivered by approved manufacturers of welded pipes,
which are considered equivalent to seamless pipes when non-destructive
testing on welds is carried out in accordance with Recognized Standards.
In other cases an efficiency factor of less than 1.0, in accordance
with recognized standards, may be required depending on the manufacturing
process. |
|
b
|
= |
allowance
for bending (mm). The value of b should be chosen so
that the calculated stress in the bend, due to internal pressure only,
does not exceed the allowable stress. Where such justification is
not given, b should be:
|
|
b
|
= |
 (mm)
|
with:
|
r
|
= |
mean
radius of the bend (mm) |
|
c
|
= |
corrosion
allowance (mm). If corrosion or erosion is expected, the wall thickness
of the piping should be increased over that required by other design
requirements. This allowance should be consistent with the expected
life of the piping. |
|
a
|
= |
negative
manufacturing tolerance for thickness (%) |