Transcript Title of presentation

The advantages of the new calculation
methods provided in the harmonized
Pressure Vessel Standard EN 13445
Part 3. Comparison with the national
standards used up to now.
Fernando Lidonnici
Convenor of WG’C’/CEN TC54
Sant’Ambrogio Servizi Industriali SRL - Milano
Determination of the Nominal Design Stress
for Steels in Service Conditions
From the point of view of the nominal design stresses:
EN 13445.3 permits higher stresses for:
• Carbon and Low Alloy Steels
• Austenitic Stainless Steels
Nominal Design Stress for CS Plates with Rm=410 MPa
Nominal Design Stress for CS Plates with Rm=510 MPa
Nominal Design Stress for SS Plates type 304
Fine Grained Steels
For Fine Grained Steels the present issue
of EN 13445.3 still provides a safety factor
of 2,4 on the room temperature tensile
strength: the problem will be solved
shortly with an amendment already
approved.
Nominal Design Stress for Fine Grained Steels with Rp0,2 = 460 MPa
2,5 Cr- 1 Mo Steels
For Cr-Mo steels of large thickness
subject to heat treatment the values of the
ASME code are higher than the values in
the corresponding EN standards: these
values however are not guaranteed and
therefore they are not reliable.
Nominal Design Stress for 2,5Cr-1Mo Steels
Domed Ends
There is an advantage in using EN 13445.3
for domed ends, particularly at higher
pressures. At low pressure the formulae of
the ASME Code may be less conservative.
Minimum Thickness of Korbbogen End with PS=5 bar
Minimum Thickness of Korbbogen End with PS=10 bar
Minimum Thickness of Korbbogen End with PS=50 bar
Minimum Thickness of Korbbogen End with PS=100 bar
Cylinders under External Pressure
Either under vacuum or at higher external
pressures EN 13445.3 permits lower
thicknesses than ASME for a given
unsupported shell length.
Minimum Thickness of Stainless Steel Shell under Vacuum at 150°C
Minimum Thickness of Stainless Steel Shell under 10 bar
Ext. Pressure at 150°C
Conical Reducers of constant thickness
EN 13445.3 permits lower thicknesses
particularly at higher pressures. It also
permits greater angles without transition
knuckle.
Conical Reducers PS=5 bar
Conical Reducers PS=10 bar
Conical Reducers PS=50 bar
Flanges:
The alternative method of Annex G is a
definite progress in respect of the old Taylor
Forge and DIN methods. Although further
gasket parameters are needed, the savings in
thickness and weight may be substantial.
9 Examples of Welding Neck Flanges designed with different
methods – Input Data for the Design
Minimum required Bolting Size / Flange Weight according to
different Methods for the 9 Examples
Heat Exchanger Tubesheets:
The alternative method of Annex J is a definite
progress in respect of the old Gardner’s
theory. The savings in thickness and weight
may be substantial, particularly for fixed
tubesheet heat exchangers.
8 Examples of H.E. Tubesheets designed with different
methods – Input Data for the Design
8 Examples of H.E. Tubesheets designed with different methods
Resulting Tubesheet Thicknesses
DESIGN BY ANALYSIS:
The “Direct Route” of Annex B permits to
ignore secondary stresses in all cases where
there is no need to consider them (constant
loading conditions).This is a substantial
advantage in the design of structures where
the classic DBA (based on elastic analysis)
caused an unnecessary increase in thickness.
SECONDARY STRESSES AT THE CONNECTION BETWEEN A CYLINDRICAL SHELL
AND A CIRCULAR FLAT END
(Note: In DBA based on elastic analysis and stress categorization the Flat end
thickness must be increased in order to limit secondary stresses on the shell)
CONCLUSIONS
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EN 13445.3 is the most advanced Pressure Vessel
standard in the world.
It permits substantial economies in Pressure Vessel
Construction.
Using a single European Pressure Vessel standard
means a greater competitiveness for the European
industry: the most important Users and Notified Bodies
must be convinced that it is now time to replace the old
Pressure Vessel standards with EN 13445.
All the resources of the interested industry must be put
on the further development of EN 13445: the further
development of the old national Pressure Vessel codes is
a waste of resources that goes against the interests of
Europe.