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ASME Boiler and Pressure Vessel Code vs. PED and EN-standardsand nuclear safety requirements

Juha PurjeInspecta Tarkastus Oy

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Pressure Equipment Directive (PED) or ASME

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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 1Scope 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 islandMany pressure equipment critical to nuclear safety

Conventional islandEquipment subject to PED

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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 BoilersII Materials

Part A — Ferrous Material SpecificationsPart B — Nonferrous Material SpecificationsPart C — Specifications for Welding Rods, Electrodes, and Filler MetalsPart D — Properties

III Rules for Construction of Nuclear Facility Components ( incl. 10 subsections) IV Rules for Construction of Heating BoilersV Nondestructive ExaminationVI Recommended Rules for the Care and Operation of Heating BoilersVII Recommended Guidelines for the Care of Power BoilersVIII Rules for Construction of Pressure Vessels

Division 1Division 2 — Alternative RulesDivision 3 — Alternative Rules for Construction of High Pressure Vessels

IX Welding and Brazing QualificationsX Fiber-Reinforced Plastic Pressure VesselsXI Rules for Inservice Inspection of Nuclear Power Plant ComponentsXII 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 DASME 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 IVThe 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-personnelOther 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 that1. The ASME Code has been widely used for many decades2. 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 ASME-material 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 high-quality 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. ENChemical composition of some common carbon steels

Steel Rp (N/mm²) Rm (N/mm²) C max(%) P max(%) S max(%)

SA-105 250 480 - 0,35 0,035 0,040SA-106 Grade B 240 415 - 0,30 0,035 0,035

SA-234 WPB 240 415 - 585 0,30 0,050 0,058SA-333 Grade 6 240 415 - 0,30 0,025 0,025SA-516 Grade 70 260 485 - 620 0,30 0,035 0,035

P280GH EN 10222-2 255 460 - 580 0,20 0,025 0,015P265GH EN 10216-2 265 410 - 570 0,20 0,025 0,020

S235 EN 10253-1 235 360 - 500 0,16 0,030 0,025P265NL EN 10216-4 265 410 - 570 0,20 0,025 0,020P295GH EN 10028-2 290 460 - 580 0,20 0,025 0,010

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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• 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

PED and EN-standardsThe smaller of the values • 2/3 Re/t , yield limit at design temperature

or • 5/12 Rm/20 , ultimate strength at + 20 °C

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

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Allowable stress of similar steels, ASME vs. ENASME Section VIII Division 1 steel SA-516 Grade 70EN 13445-3 steel P295GH EN 10028-2

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100

150

200

250

300

350

Degrees C

N/mm2 Rp0,2 P295GHP295GH PEDSA-516 Grade70

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

20 50 100 150 200 250 300 350 400

Rm / 3,5

Rm / 2,4

N/mm²

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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

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150

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250

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A106B NGS 141 240 229 215 202 185 164 144 127 115 106St 45.8 DIN 17175 245 195 175 155 135 130 125P265GH EN 10216-2 265 235 226 213 192 171 154 141 134 128A106B ASME Y-1 241 235 221 214 207 199 188 177 167 158

20 50 100 150 200 250 300 350 400 450

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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

Qualification and approval manufacturer Third party in categoriesof welding procedures in accordance with II, III and IV in accordance and welders ASME Section IX with EN-standards

Approval of manufacturer or Third party in categoriesNDT-personnel NDT-subcontractor in III and IV in accordance

accordance with SNT-TC-1A with EN 473

Materials Listed in ASME Section II Listed in harmonizedor standards or

"recertification" particular material appraisalMaterial certificates required for plates required for all materials

for other types of materials typically EN 10204 3.1 andthe 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 responsibilityfor 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 IXThe 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 287-1The 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. ENNon-destructive testing of welds

The amount of non-destructive tests depends of the welding efficiency factor used in design calculations

E or z ASME Section VIII Div.1 PED EN 13445-51,0 longitudinal transversal NDT and destructive longitudinal transversal

100 % spot tests to confirm 100 % 25 - 100 %that no significant

defects exist0,85 spot spot

longitudinal transversal longitudinal transversalmin. 1 test 10 - 25 % 2 - 10 %per 15 m 0 %

0,7 0 % 0 % 0 %

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Pressure test ASME vs. PED

ASME Section VIII Div.1

1,3 • maximum allowable pressure

– In most cases the specified materials do not influence the test pressure

PED and EN 13445-5

Higher of the values

− 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+ 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 NDE-personnel

+ Cheaper costs of NDE

EN 13445+ 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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