Comparativa En13445-Asme Viii
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Transcript of Comparativa En13445-Asme Viii
1
Comparative Study: EN 13445 –
ASME VIII
Workshop on the Pressure Equipment Directive
Bucharest, February, 2007
Dr. Reinhard Preiss
TÜV Austria
Krugerstrasse 16
A-1015 Vienna, Austria
Tel. +43 1 51407 6136
e-mail: [email protected]
http://www.tuev.at
2
Introduction
Background: A harmonised standard related to a "New
Approach" Directive does give the manufacturer the advantage
of the presumption of conformity to the Essential Safety
Requirements of the Directive itself, but to be accepted and
applied, it must also bring economic and/or technical
advantages.
This study compares the economic and non-economic
implications arising from the application of (a) EN 13445 and, (b)
the ASME Boiler & Pressure Vessel Code plus major related
codes when appropriate (TEMA, WRC Bulletins), for the design,
manufacture, inspection and acceptance testing of 9 benchmark
examples of unfired pressure vessels.
3
Introduction
The consortium which carried out the study, based on a
contract with the EC / DG Enterprise, consists of TUV Austria
and of Consorzio Europeo di Certificazione (CEC) – both are
Notified Bodies according to the PED.
The detailed design of the benchmark examples was
performed by the consortium. To evaluate the economic
factors concerning individual and/or serial production of the
benchmark vessels, pressure equipment manufacturers from
Italy, France, Germany and Austria took part as
subcontractors.
6
Conformity Assessment
For estimation of the costs the following combinations of codes and conformity
assessment routes were considered:
EN 13445 and conformity assessment according to the PED (CE-marking).·
ASME Section VIII (Division 1, Division 2 if applied) and conformity
assessment according to ASME (U-stamp, or U2-stamp).
ASME Section VIII (Division 1, Division 2 if applied) and conformity
assessment according to the PED (CE-marking).
The exercise is based on compliance with the corresponding requirements in a
situation where there are no pre-existing qualifications or supplementary data
which could be used from other similar equipment
7
Conformity Assessment
In the case of application ASME Section VIII (Division 1, Division 2 if applied) and
conformity assessment according to the PED additional requirements were made:
Materials: material properties used in the design must be those affirmed by the
material manufacturer. This may include hot tensile properties (yield strength
according to ASME II Table Y-1), impact properties for carbon steel at MDMT but
not higher than 20°C with a minimum value of 27J.
Hydrostatic test Pressure: The hydraulic test pressure Ptest shall not be smaller
than 1.43 PS, even if this requires an increase in wall thickness when an
“equivalent design pressure Peq” given by Peq = Ptest x S/Sa/1,3 is greater than
PS. The 1.25x.. requirement is not used, but if it would be the governing one, the
NDT level is increased to at least 0.85.
Permanent joining and NDT: welding operating procedures and personnel, NDT
personnel: requirements as given in the PED have to be fulfilled
Fatigue design: ASME unconservative for welded regions?
9
Benchmark Example 1 – CNG storage tank
DBA according to EN 13445 is advantageous in this case
Higher costs for the ASME design are basically caused by higher
material costs, due to larger wall thicknesses, and to some extent
by the post weld heat treatment costs. A vessel according to
ASME VIII Div.2 is considerably cheaper than one according to
ASME VIII Div.1 due to the large differences in resulting wall
thicknesses .
10
Benchmark Example 1 – CNG storage tank
No considerable cost differences due to NDT
Test coupons required for EN design, but not for ASME. Thus,
higher costs for EN for this task.
The additional costs for the ASME vessels if conformity
assessment with the PED is required are rather small (some
marginally increased wall thicknesses for ASME VIII Div.1, higher
testing requirements for the materials) – presuming that the
results of the material tests fulfil the requirements. In the case of
ASME VIII Div. 2, no increase of the wall thicknesses due to
hydraulic test pressure given by the PED is required.
11
Benchmark Example 2 –
Hydrogen Reactor
Diameter 2200 mm, cylindrical length app.
8000 mm, hemispherical ends, max.
allowable pressure 180 bar, max.
allowable temperature 400°C.
Forged courses: 11CrMo9-10 / EN 10222-
2; SA-387 Gr. 22 Cl. 2.
Welded courses: 12CrMo9-10 / EN
10028-2; SA-336 Gr. 22 Cl. 2.
12
Benchmark Example 2 – Hydrogen Reactor
Differences in the design wall thicknesses (e.g. for the main cylindrical
shell / forged courses 190 mm for EN 13445 DBF, 181 mm for ASME VIII
Div.1, and 151 mm for ASME VIII Div. 2; and for the main cylindrical shell
/ welded courses 124 mm for EN 13445 DBF, 181 mm for ASME VIII
Div.1, and 151 mm for ASME VIII Div. 2) are mainly caused by the
different allowable stresses.
13
Benchmark Example 2 – Hydrogen Reactor
The costs are do mainly depend on the wall thicknesses, there
are no considerable cost differences due to NDT, and test
coupons required for both routes.
Again, the additional costs for the ASME vessels if conformity
assessment with the PED is required are rather small (some
marginally increased wall thicknesses for ASME VIII Div.1, higher
testing requirements for the materials) – presuming that the
results of the material tests fulfil the requirements. In the case of
ASME VIII Div. 2, no increase of the wall thicknesses due to
hydraulic test pressure given by the PED is required.
15
Benchmark Example 4 – Stirring Vessel
A fatigue analysis was performed for the fluctuating load components of the stirrer,
considering a requirement of an infinite number of load cycles. A fatigue analysis for the
upper end, leading to the allowable number of (specified) batch cycles, was also
performed.
The fatigue results differ substantially: the required reinforcement of the mounting
flange to obtain stresses which result in a design for an infinite number of load cycles is
different for the two code routes. Furthermore, the allowable number of batch cycles
according to EN is 13100, but that according to ASME is 2x108.
16
Benchmark Example 4 – Stirring Vessel
Since the material SA-240 Grade 316Ti is not allowed for application of
ASME VIII Div. 2, and the allowable stress of SA 240 Grade 316L is
considerably lower, the application of ASME VIII Div. 2 would generally lead
to larger wall thicknesses for the shells and ends. Thus, application of ASME
VIII Div. 2 is not economic in this case.
Inner body of the vessel: differences in the design wall thicknessess are
mainly caused by different design methods for external pressure (EN design:
11 mm wall thickness, two reinforcing rings 25x125 mm; ASME design:
15 mm wall thickness, two reinforcing rings 30x160 mm). Inner dished end:
differences in the design wall thicknessess also mainly caused by the
different design methods for external pressure (EN design: 15 mm wall
thickness; ASME design: 23 mm wall thickness).
17
Benchmark Example 4 – Stirring Vessel
The higher costs for the ASME designs are basically caused by higher material costs
due to larger wall thicknesses, and thus higher fabrication costs. These are partly
compensated by lower costs for NDT and for test coupons, since the NDT
requirements according to ASME are lower than those according to EN (for the
chosen weld joint efficiency) and due to the fact that no test coupons are required for
the ASME route.
The additional costs for the ASME vessels if PED conformity assessment is required
are rather small and are mainly caused by higher material costs due to the required
increased wall thickness for the lower end and the costs for an additionally required
pad at a nozzle. Due to the moderate service temperature no hot tensile test is
required, and no additional impact testing is considered necessary for the austenitic
steels used. Thus, the additional costs for material testing are negligible.
18
Overall Summary
The project has considered application of the new harmonised
standard EN 13445 and the ASME VIII design procedures to a set
of 9 example cases which covered a wide range of pressure
vessel types, designs, materials and fabrications .
The overall basis for comparison was one of economic cost. A
procedure was used which allowed fair comparison of three
routes: EN 13445, ASME + U-stamp, ASME + PED. While the
consortium performed the design, several EU manufacturers were
involved in the project to assess the costs.
20
Overall Summary
Material costs are frequently greater using the ASME code. In some
cases, savings attributable to lower material costs with EN 13445 are
partly offset by additional costs of weld testing and NDT when compared
with ASME requirements.
For standard refinery heat exchangers no notable costs differences are
reported (if TEMA requirements are considered).
In some cases the reported costs differences for different manufacturers
are larger than the cost differences resulting from the application of the
various code routes.
PWHT costs are frequently higher for ASME design, since the PWHT
requirements depend on the wall thicknesses.
21
Overall Summary
Use of Design-by-Analysis according to EN 13445-3 Annex B can
decrease the material costs considerable in some cases, especially for
more advanced or complex design or in serial production. The
increased design costs are easily compensated by the savings for
materials and – if applicable – by the savings of the post weld heat
treatment costs.
According to the cost estimations of the manufacturers, the extra costs
for ASME designs to meet the PED requirements are in general small
for the approach used in the study.
22
Overall Summary
Fatigue design according to ASME Div. VIII Sec. 2 Appendix 5 for
welded regions is considered to be non-conservative in comparison
with procedures in major European pressure vessel codes (e.g. EN
13445, AD-Merkblatt, PD 5500) and the underlying experimental
results. Thus, ASME fatigue design for these regions is not considered
to meet the requirements of PED Annex I. Taking this into account, the
results of alternative design procedures may be required for fatigue
evaluation, i.e. re-assessment of the fatigue life using a European
approach would be desirable in practice, but was not performed within
this study.
23
Discussion on ASME reply
According to the paper “Design Fatigue Life Comparison of ASME Sec.
VIII and EN 13445 vessels with welded region” by Kalnins et.al. ([1],
PVP 2006-ICPVT-11) fatigue strength reduction factors shall be used,
e.g. the ones given in WRC Bulletin 432. In the opinion of the authors of
the Comparative study, in the ASME code itself this is stated for fillet
weld but no there is no hint to use such factors for full penetration welds.
In a mayor code, it should be stated unambiguous if such factors shall
be used and also the reference where to find such factors shall be
given.
24
Discussion on ASME reply
According to the paper “Comparison of Pressure Vessel Codes ASME
Section VII & EN 13445” by Antalffy et.al. ([2], PVP 2006-ICPVT-11) the
vessel manufacturers providing cost estimates in the study are not based
in countries which produce the majority of pressure vessels in the world
(Japan, Korea, USA).
According to [2], the size and quantity distribution of vessels used in the
Comparative Study is generally not representative of typical chemical,
petrochemical or petroleum process facilities. The greater part of the
total cost of pressure vessels is attributed to only a relatively small
number of the higher end pressure vessels. For these high end vessels
ASME Section VIII Div. 3 can be used, which reduces wall thickness and
cost by up to 15 percent over present Division 2 requirements.
25
Discussion on ASME reply
According to [2] a review of the EN standard has shown several important and
innovative features. The ASME is in the process of rewriting Section VIII, Division
2, which will make a range of Division 2 vessels even more competitive with the
EN standard. This rewrite is an opportunity to incorporate the latest advances in
pressure vessel design, as well as new and innovative features that will enable
the ASME Code to remain the preeminent pressure vessel standard.
The survey presented in [2] concluded that throughout the global industry there
is a strong preference to use the ASME codes for pressure vessel design and
manufacturing. Even though the PD5500 or EN 13445 may have a few specific
areas or cases where there is a small economic advantage, when considering
the overall aspects of the entire organization, plant, or project cost, the ASME
code seems to provide a better overall advantage.