ASME Boiler and Pressure Vessel Code vs. PED and EN-standards
and nuclear safety requirements
Juha Purje
Inspecta Tarkastus Oy
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Pressure Equipment Directive (PED) or
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ASME
The PED shall be applied to all pressure equipment to be used in
European Union except such pressure equipment that are critical to
nuclear safety, they are excluded from PED
Article 1
Scope and definitions
…
3. The following are excluded from the scope of this Directive:
….
3.8. items specifically designed for nuclear use, failure of
which may cause an emission of radioactivity;
Such equipment should be designed and manufactured
in accordance with a specific code like
– ASME Boiler and Pressure Vessel Code Section III
– French RCC-M
– German KTA
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Nuclear island
Many pressure equipment
critical to nuclear safety
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Conventional island
Equipment subject to PED
ASME Boiler & Pressure Vessel Code is an extensive set of rules on the
design, manufacturing and operation of boilers and pressure vessels
I Rules for Construction of Power Boilers
II Materials
Part A — Ferrous Material Specifications
Part B — Nonferrous Material Specifications
Part C — Specifications for Welding Rods, Electrodes, and Filler Metals
Part D — Properties
III Rules for Construction of Nuclear Facility Components ( incl. 10 subsections)
IV Rules for Construction of Heating Boilers
V Nondestructive Examination
VI Recommended Rules for the Care and Operation of Heating Boilers
VII Recommended Guidelines for the Care of Power Boilers
VIII Rules for Construction of Pressure Vessels
Division 1
Division 2 — Alternative Rules
Division 3 — Alternative Rules for Construction of High Pressure Vessels
IX Welding and Brazing Qualifications
X Fiber-Reinforced Plastic Pressure Vessels
XI Rules for Inservice Inspection of Nuclear Power Plant Components
XII Rules for Construction and Continued Service of Transport Tanks
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Differences between European and American legal systems
concerning pressure equipment
Europe
• The PED (Pressure Equipment Directive) is the law for all European Union member
states
• The Essential Safety Requirements of PED are often rather general but some
requirements are very specific and those specific requirements shall be met.
• Pressure Equipment which conform to the harmonized standards is presumed to
conform to the Essential Safety Requirements of PED.
• To follow the harmonized standards is the preferred method to show compliance to the
PED but they are not mandatory. The manufacturer may follow any set of rules or
standards for design and manufacturing on condition that the Essential Safety
Requirements are met.
USA
• The ASME Boiler and Pressure Vessel Code is not a law but construction standard
generally accepted in USA and in many other countries.
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Most important harmonized standards
For products:
EN 13445:2009
Unfired pressure vessels – Parts 1 to 8
(with latest amendments)
EN 13480:2012
Metallic industrial piping - Parts 1 to 8
For welding procedures:
EN ISO 15614-1:2004 Specification and qualification of welding procedures for metallic
(with amendments)
materials - Welding procedure test - Part 1: Arc and gas welding
of steels and arc welding of nickel and nickel alloys
For personnel qualification:
EN 287-1:2011
Qualification test of welders - Fusion welding - Part 1: Steels
EN 473:2008
Non-destructive testing - Qualification and certification of NDT
personnel - General principles
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PED and ASME Boiler and Pressure Vessel Code
There are many fundamental differences between PED and ASME Code.
The PED does not set any specific calculation equations, therefore the design
calculation may also be based on the equations of a ASME Code.
– The allowable stress specified in PED is often different from the allowable stress of
ASME Section II D
ASME Code allows that the manufacturer may perform many activities by himself in
accordance with his quality manual, PED requires the involvement of a recognized
third-party organisation in categories II, III and IV
The major differences between the essential safety requirements of PED and ASME
Code are
– acceptable materials
– material properties and material certification
– approval of welding procedures
– approval of and welders and NDT-personnel
Other differences
– hazard analysis is required in PED
– pressure vessel test pressure
– PED requires that the manufacturer must prepare the operating instructions and
supply them with the pressure equipment to the user
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PED and ASME
ASME Code is mandatory in USA and Canada, a pressure vessel that will be used in
USA or Canada shall be code stamped. This requires the involvement of an Authorized
Inspection Agency and certification by an Authorized Inspector.
Many other countries have also accepted ASME Code. In these countries the ASME
Code is applied in many different ways, only seldom to the full extent of ASME Code.
– the manufacturer does not have the ASME Certificate of Authorization
– there is no involvement of ASME AIA or AI, therefore no ASME stamp
– only design calculations are made in accordance with the ASME code, and this is
because the designer has suitable software.
There are many manufacturers and also some notified bodies who think that
1. The ASME Code has been widely used for many decades
2. Pressure vessels that have been designed and manufactured in accordance with
ASME Code have been proven to be safe
 As they have been proven to be safe they meet the essential safety requirements
of PED
This is not true. The PED is European Union law that shall be followed to the letter.
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ASME material specifications are not harmonized material standards.
The suitability of such a material shall be assessed as Particular Material Appraisal.
General rule :
Material that has been supplied in accordance with the minimum requirements of ASMEmaterial specification does not meet the essential safety requirements of PED.
– A certificate of specific product control is not a mandatory requirement for many ASME-materials.
– The organization responsible for material certification may also be other than material manufacturer.
– Material traceability is endangered because the ASME material specification may not require the
products to be marked with heat or batch number.
– Many ASME pressure vessel carbon steel specifications do not have any requirements for minimum
impact energy and even if it is specified the required value is less than 27 J.
– The tensile strength properties at elevated properties are not specified in the material specification.
There are even some ASME material specifications that do not specify any minimum tensile strength
properties.
– ASME-material specifications often allow such high amount of C, P and S that at the extreme highquality welding would be difficult and impact strength non-existent.
If the pressure equipment manufacturer specifies an ASME material he shall set supplementary
requirements when purchasing the material like:
– A requirement for the certificate of specific product control (EN 10204:2004 3.1 or 3.2)
– A requirement that only material manufacturer may certify the material
– A requirement of material markings to guarantee traceability with the certificate
– To specify properties that are stricter than the minimum requirements of ASME material specification
like manufacturing methods or limitations for the amount of C, P and S
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ASME vs. EN
Chemical composition of some common carbon steels
Steel
Rp (N/mm²)
SA-105
250
480 -
0,35
0,035
0,040
SA-106 Grade B
240
415 -
0,30
0,035
0,035
SA-234 WPB
240
415 - 585
0,30
0,050
0,058
SA-333 Grade 6
240
415 -
0,30
0,025
0,025
SA-516 Grade 70
260
485 - 620
0,30
0,035
0,035
P280GH EN 10222-2
255
460 - 580
0,20
0,025
0,015
P265GH EN 10216-2
265
410 - 570
0,20
0,025
0,020
S235 EN 10253-1
235
360 - 500
0,16
0,030
0,025
P265NL EN 10216-4
265
410 - 570
0,20
0,025
0,020
P295GH EN 10028-2
290
460 - 580
0,20
0,025
0,010
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Rm (N/mm²) C max(%) P max(%) S max(%)
Design calculation
The theory of stress and strain is similar everywhere but practical applications are
somewhat different depending of the code.
Minimum wall thickness of cylindrical shell is defined in the following equations
ASME Section VIII Div.1
EN 13445-3
t or e = minimum thickness
P = design pressure
R = inside radius of shell
(R = Di / 2)
Di = inside diameter of shell (Di = 2•R)
E or z = weld efficiency factor or joint coefficient
S or f = stress value = maximum allowable membrane stress
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Allowable stress of ferritic steel
ASME Section VIII Division 1
PED and EN-standards
• Allowable stress is specified in ASME
Section II D Table 1A
• The maximum allowable stress value is
the smaller of
– the specified minimum tensile
strength at room temperature divided
by 3.5
– two-thirds of the yield strength at
temperature
• The ASME-material specifications
specify the minimum strength values at
room temperature only.
– The yield strength at elevated
temperature is based on statistical
values, those values are not
guaranteed minimum values
The smaller of the values
• 2/3 Re/t , yield limit at design temperature
or
• 5/12 Rm/20 , ultimate strength at + 20 °C
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Strength values at room temperature and
at elevated temperatures are specified in
the applicable harmonized material
standard. Those values are to be
considered as guaranteed values but
tensile testing at elevated temperature is
not mandatory
Allowable stress of similar steels, ASME vs. EN
ASME Section VIII Division 1 steel SA-516 Grade 70
EN 13445-3 steel P295GH EN 10028-2
N/mm²
350
300
250
Rm / 2,4
200
Rp0,2 P295GH
N/mm2
Rm / 3,5
P295GH PED
150
SA-516 Grade70
100
50
0
20
50
100 150 200 250 300 350 400 Degrees C
Rp0,2 P295GH
290 280 264 244 225 206 189 175 160
P295GH PED
191 191 176 163 150 137 126 117 107
SA-516 Grade70 138 138 138 138 138 138 135 129 101
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Yield strength of steel ASME SA-106 B (N/mm²) in accordance with Section II D
Table Y-1 vs. similar European steel specifications or previous approvals
300
250
200
150
100
50
0
20
50
100 150 200 250 300 350 400 450
A106B NGS 141
240 229 215 202 185 164 144 127 115 106
St 45.8 DIN 17175
245
195 175 155 135 130 125
P265GH EN 10216-2 265 235 226 213 192 171 154 141 134 128
241 235 221 214 207 199 188 177 167 158
A106B ASME Y-1
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NOTES TO TABLE Y-1
(b) The tabulated values of yield strength values are those which the Committee believes
are suitable for use in design calculations. At temperatures above room temperature, the
yield strength values correspond to the yield strength trend curve adjusted to the minimum
specified room temperature yield strength. The yield strength values do not correspond
exactly to ”minimum” as this term is applied to a statistical treatment of a homogenous set
of data. Neither the ASME Material Specifications nor the rules of Section I, Section III, or
Section VIII require elevated temperature testing for yield strengths of production material
for use in Code components. It is not intended that results of such tests, if performed, be
compared with these tabulated yield strength values for ASME Code acceptance
/rejection purposes for materials. If some elevated temperature test results on production
material appear lower than the tabulated values by a large amount (more than the typical
variability of material and suggesting the possibility of some error), further investigation by
retest or other means should be considered.
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ASME vs. PED in manufacturing
ASME
PED
Authorized manufacturer
required
not required
Quality Manual
required
in modules D, E, H
manufacturer
in accordance with
ASME Section IX
Third party in categories
II, III and IV in accordance
with EN-standards
Approval of
NDT-personnel
manufacturer or
NDT-subcontractor in
accordance with SNT-TC-1A
Third party in categories
III and IV in accordance
with EN 473
Materials
Listed in ASME Section II
or
"recertification"
Listed in harmonized
standards or
particular material appraisal
Qualification and approval
of welding procedures
and welders
Material certificates
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required for plates
required for all materials
for other types of materials
typically EN 10204 3.1 and
the marking as specified in
material manufacturer shall
material standard is sufficient
operate a quality system
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PED Annex I Essential Safety Requirements
3.1.2. Permanent joining
For pressure equipment, permanent joining of components which contribute to the pressure
resistance of equipment and components which are directly attached to them must be carried out
by suitably qualified personnel according to suitable operating procedures.
For pressure equipment in categories II, III and IV, operating procedures and personnel
must be approved by a competent third party which, at the manufacturer's discretion, may be:
- notified body,
- a third-party organization recognized by a Member State as provided for in Article 13.
To carry out these approvals the third party must perform examinations and tests as set out
in the appropriate harmonized standards or equivalent examinations and tests or must have
them performed.
3.1.3. Non-destructive tests
For pressure equipment, non-destructive tests of permanent joints must be carried out by suitable
qualified personnel. For pressure equipment in categories III and IV, the personnel must be
approved by a third-party organization recognized by a Member State pursuant to Article 13.
A problem for manufacturers outside of European Union :
The notified bodies or third-party organisations are far away !
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Transfer of Welding Procedure Qualification Records
ASME IX:
When a manufacturer or contractor is acquired by a new owner, the PQRs and
WPSs may be used by the new owner without requalification, provided that the
new owner takes responsibility for the WPSs and PQRs and the source of the
PQRs is identified as being from the former manufacturer.
EN 15614-1:
A qualification of a pWPS by a welding procedure test obtained by a manufacturer
is valid for welding in workshops or sites under the same technical and quality
control of the manufacturer.
– Welding is under the same technical and quality control when the manufacturer
who performed the welding procedure test retains complete responsibility
for all welding carried out to it.
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Welder Qualification
The principles of welder qualification in ASME Section IX and EN 287-1 are
the same.
Each welder or welding operator shall be qualified for each welding process
and material to be used in production welding.
There are some variations in the test pieces and in the range of
qualification.
EN 287-1 is a general welder qualification standard. It may be applied in
any industry, not only for welding pressure equipment.
The PED sets the additional requirement that the welder’s test shall be
witnessed and approved by a notified body or by a recognized third-party
organization.
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EN 287-1 Annex C (informative)
Job knowledge
The test of job knowledge is recommended, but it is not mandatory.
However, some countries can require that the welder undergoes a test of job
knowledge. If the job knowledge test is carried out, it should be recorded on the
welder’s qualification test certificate.
This annex outlines the job knowledge that a welder should have to ensure that
procedures are followed and common practices are complied with. The job knowledge
indicated in this annex is only pitched at the most basic level.
Owing to different training programmes in various countries, it is only proposed to
standardize general objectives or categories of job knowledge. The actual question used
should be drawn up by the individual country, but should include questions on areas
covered in C.2, relevant to the qualification test of welders.
The actual tests of a welder’s job knowledge can be given by any of the following
methods or combinations of these methods:
a) written objective tests (multiple choice);
b) oral questioning following a set of written questions;
c) computer testing;
d) demonstration/observation testing following a written set of criteria.
The test of job knowledge is limited to the matters related to the welding process used in
the test.
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Expiration of Welder Qualification
ASME IX
The qualification of a welder is valid without time limit on condition that
– he has welded on that process during a period of 6 months
– there is no reason to question his ability to weld
EN 287-1
The welder's qualification test certificate is valid for a period of two years
on condition that the employer can confirm every six months that the
welder has been welding within the range of qualification with satisfactory
results.
Welder's qualification test certificates can be prolonged every two years
by the examiner or examining body.
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ASME vs. EN
Non-destructive testing of welds
The amount of non-destructive tests depends of the welding efficiency factor
used in design calculations
E or z
1,0
0,85
ASME Section VIII Div.1
PED
longitudinal transversal NDT and destructive longitudinal transversal
spot
tests to confirm
100 %
25 - 100 %
100 %
that no significant
defects exist
spot
spot
longitudinal transversal
min. 1 test
per 15 m
0,7
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EN 13445-5
longitudinal transversal
10 - 25 %
2 - 10 %
0%
0%
0%
0%
Pressure test ASME vs. PED
ASME Section VIII Div.1
PED and EN 13445-5
1,3 • maximum allowable pressure
Higher of the values
– In most cases the specified
materials do not influence the
test pressure
− 1,43 • maximum allowable pressure
− 1,25 • maximum allowable pressure •
fa is the nominal design stress of the
material at the test temperature;
fTd is the nominal design stress of the
material at design temperature
Typical test pressure for a pressure vessel
that is designed to operate at elevated
temperature is 1,5 – 2,0 • maximum
allowable pressure
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ASME Section VIII Div. 1 vs. EN 13445 / PED
ASME Section VIII Div. 1
EN 13445
+ Cheaper materials
+ Extensive selection of materials, short
delivery times
+ Plenty of calculation programs
+ Proven and familiar code, simple
determination of test pressure
+ The manufacturer qualifies his welding
procedures, welders and NDEpersonnel
+ Cheaper costs of NDE
+ Meets the PED requirements
+ In most cases less material is required
+ No quality manual is required in module G.
The manufacturing may begin if the
welding procedures and personnel are
qualified.
+ Many notified bodies
+ The manufacturer may inspect and certify
the products by himself in modules A, A1,
C1, D, D1, E, E1 and H without direct
involvement of the third party
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ASME Boiler & Pressure Vessel Code vs.
Pressure Equipment Directive (PED)
• If a boiler or pressure vessel is to be delivered to European Union it
shall be manufactured in accordance with PED and CE-marked.
• If a boiler or pressure vessel is to be delivered to USA or Canada it shall
be manufactured in accordance with ASME Boiler & Pressure Vessel
Code and ASME-stamped.
• Both rules are in practice mandatory in their own area, there is no
possibility for a compromise. The manufacturer shall accept the
customer’s requirements.
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