Bsi bs en 15776 2011 + a1 2015

BS EN 15776:2011+A1:2015
Incorporating
corrigendum
November 2015
BS EN
15776:2011

BSI Standards Publication

Unfired pressure vessels —
Requirements for the design
and fabrication of pressure
vessels and pressure parts
constructed from cast iron with
an elongation after fracture
equal or less than 15 %


BS EN 15776:2011+A1:2015

BRITISH STANDARD
National foreword
This British Standard is the UK implementation of
EN 15776:2011+A1:2015. It supersedes BS EN 15776:2011 which is
withdrawn.
The start and finish of text introduced or altered by amendment is
indicated in the text by tags. Tags indicating changes to CEN text carry
the number of the CEN amendment. For example, text altered by CEN
amendment A1 is indicated by .
The UK participation in its preparation was entrusted to Technical
Committee PVE/1, Pressure Vessels.

A list of organizations represented on this committee can be obtained
on request to its secretary.
This publication does not purport to include all the necessary provisions
of a contract. Users are responsible for its correct application.
© The British Standards Institution 2015.
Published by BSI Standards Limited 2015
ISBN 978 0 580 86315 8
ICS 23.020.30

Compliance with a British Standard cannot confer immunity from
legal obligations.
This British Standard was published under the authority of the Standards
Policy and Strategy Committee on 30 April 2011.

Amendments/corrigenda issued since publication
Date

Text affected

30 November 2015Implementation of CEN amendment A1:2015
30 November 2015Implementation of CEN correction notice
28 October 2015: Note 2 to entry added to
subclause 3.1.1


EUROPEAN STANDARD

EN 15776:2011+A1

NORME EUROPÉENNE

EUROPÄISCHE NORM

October 2015

ICS 23.020.30

Supersedes EN 15776:2011

English Version

Unfired pressure vessels - Requirements for the design and
fabrication of pressure vessels and pressure parts constructed
from cast iron with an elongation after fracture equal or less than
15 %
Récipients sous pression non soumis à la flamme Exigences supplémentaires pour la conception et la
fabrication des récipients sous pression et des parties sous
pression moulés en fonte à allongement, après rupture,
inférieur ou égal à 15 %

Unbefeuerte Druckbehälter - Anforderungen an die
Konstruktion und Herstellung von Druckbehältern und
Druckbehälterteilen aus Gusseisen mit einer Bruchdehnung
von 15 % oder weniger

This European Standard was approved by CEN on 1 January 2011 and includes Amendment 1 approved by CEN on 24 August 2015.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same

status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN

All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members.

Ref. No. EN 15776:2011+A1:2015 E


BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

Contents

Page

European foreword....................................................................................................................................................... 4
Introduction .................................................................................................................................................................... 5
1

Scope .................................................................................................................................................................... 6

2

Normative references .................................................................................................................................... 6

3
3.1
3.2
3.3

Terms, definitions, units and symbols..................................................................................................... 7
Terms and definitions ................................................................................................................................... 7
Symbols ............................................................................................................................................................... 9
Inter relation of thicknesses definitions (!EN 13445-6:2014") ......................................... 11

4
4.1
4.2

Materials, limitations and service conditions.................................................................................... 11
Materials and limitations on temperature, maximum allowable pressure and energy
content ............................................................................................................................................................. 11
Cyclic loading ................................................................................................................................................. 13

5

5.1
5.2
5.3
5.3.1
5.3.2
5.3.3
5.3.4
5.4
5.5
5.6
5.7
5.8
5.8.1
5.8.2
5.8.3
5.9
5.9.1
5.9.2
5.9.3
5.10
5.10.1
5.10.2
5.10.3
5.10.4
5.10.5

Design requirements .................................................................................................................................. 14
Design principle............................................................................................................................................ 14
Conceptual design and construction drawings ................................................................................. 14
Static loading ................................................................................................................................................. 14

General ............................................................................................................................................................. 14
Design by formula (DBF) ........................................................................................................................... 14
Design by analysis (DBA)........................................................................................................................... 15
Design by experiment (DBE) .................................................................................................................... 15
Temperature reduction factor ................................................................................................................ 16
Wall thickness reduction factor .............................................................................................................. 16
Design for external pressure ................................................................................................................... 16
Testing conditions ....................................................................................................................................... 17
Design methods ............................................................................................................................................ 17
General ............................................................................................................................................................. 17
Static loading ................................................................................................................................................. 17
Dynamic loading ........................................................................................................................................... 19
Construction details .................................................................................................................................... 24
Reinforcement of openings in cylinders, flat ends, dished ends, etc. ........................................ 24
Fillet radius .................................................................................................................................................... 24
Dished cover .................................................................................................................................................. 24
Technical documentation.......................................................................................................................... 24
General ............................................................................................................................................................. 24
Information to be contained in the technical documentation ..................................................... 24
Test reports .................................................................................................................................................... 26
Technical/manufacturing schedule ...................................................................................................... 26
Design review ................................................................................................................................................ 26

6
6.1
6.1.1
6.1.2
6.2

Founding, material and casting testing ................................................................................................ 27

Founding.......................................................................................................................................................... 27
General ............................................................................................................................................................. 27
Welding ............................................................................................................................................................ 27
Material testing ............................................................................................................................................. 27

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15776:2011+A1:2015 (E)

6.2.1
6.2.2
6.2.3
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.3.7
6.3.8
6.3.9
6.3.10

General ............................................................................................................................................................. 27

Frequency and number of tests ............................................................................................................... 27
Inspection documents ................................................................................................................................. 28
Casting testing................................................................................................................................................ 28
General ............................................................................................................................................................. 28
Surface imperfections ................................................................................................................................. 28
Cracks, laps, cold shot and non-fused chaplets .................................................................................. 28
Ultrasonic testing and/or sectioning..................................................................................................... 29
Liquid penetrant testing ............................................................................................................................ 29
Surface roughness ........................................................................................................................................ 29
Minimum wall thickness ............................................................................................................................ 29
Wall thickness tolerances .......................................................................................................................... 29
Other dimensions ......................................................................................................................................... 29
Qualification of testing personnel .......................................................................................................... 29

7
7.1
7.2

Final assessment ........................................................................................................................................... 30
General ............................................................................................................................................................. 30
Hydraulic test pressure .............................................................................................................................. 30

8

Pressure vessels assembled of a combination of parts in different materials ....................... 30

9
9.1
9.2
9.3

Marking and documentation .................................................................................................................... 30
Marking of castings ...................................................................................................................................... 30
Name plate for the complete pressure vessel .................................................................................... 30
Documentation .............................................................................................................................................. 31

Annex A (normative) Technical data for design calculations .................................................................... 32
Annex B (informative) Recommendations for in-service validation and inspection....................... 35
B.1

Purpose ............................................................................................................................................................ 35

B.2

Tests during operation ............................................................................................................................... 35

Annex C (informative) Examples of fatigue design curves......................................................................... 36
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 97/23/EC ............................................................................................. 39
Bibliography ................................................................................................................................................................. 40

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BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

European foreword
This document (EN 15776:2011+A1:2015) has been prepared by Technical Committee CEN/TC 54
“Unfired pressure vessels”, the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2016, and conflicting national standards shall be
withdrawn at the latest by April 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
This document supersede EN 15776:2011.

This document includes Amendment 1 approved by CEN on 2015-08-24.

The start and finish of text introduced or altered by amendment is indicated in the text by tags !".

This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

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EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

Introduction
!This standard is a stand-alone document and may be used for pressure equipment with certain
restrictions and limitations.

NOTE For the design and fabrication of cast iron pressure equipment standards with higher
elongations and ductility, see EN 13445-6:2014."

Attention is drawn to the references to !EN 13445-6:2014"for design and fabrication according to
specific grades of material standards !EN 1563:2011"and !EN 13835:2012"which are found
in some clauses of this standard, EN 15776. Requirements for the design, material, manufacturing and
testing of pressure vessels and pressure vessel parts made from ferritic or austenitic spheroidal
graphite cast iron grades with an elongation after fracture higher than 15 % are given in !EN 134456:2014".
Cast iron with elongation after fracture equal or less than 15 % may only be used for pressure
equipment when operational and technical advantages are dictating its use instead of the cast iron
grades given in !EN 13445-6:2014"with elongation after fracture higher than 15 %.

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EN 15776:2011+A1:2015

15776:2011+A1:2015 (E)
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EN

1 Scope
This European Standard specifies requirements for the design, material, manufacturing and testing of
pressure vessels and pressure vessel parts made from materials for which details are specified from the
following material standards for specific grades which meet the criterion of an elongation after fracture
less than or equal to 15 %:
— !EN 1561:2011", Founding — Grey cast irons;

— !EN 1563:2011", Founding — Spheroidal graphite cast irons;
— !EN 13835:2012", Founding — Austenitic cast irons.

The allowed content of the vessel or pressure part is a fluid of group 2 only, according to the
Directive 97/23/EC.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

!EN 764-5:2014, Pressure equipment — Part 5: Inspection documentation of metallic materials and
compliance with the material specification"

!EN 1370:2011, Founding — Examination of surface condition"

!EN 1371-1:2011, Founding — Liquid penetrant testing — Part 1: Sand, gravity die and low pressure
die castings"

!EN 1559-1:2011", Founding — Technical conditions of delivery — Part 1: General

!EN 1559-3:2011", Founding — Technical conditions of delivery — Part 3: Additional requirements
for iron castings
!EN 1561:2011", Founding — Grey cast irons

!EN 1563:2011", Founding — Spheroidal graphite cast irons

!EN 12680-3:2011, Founding — Ultrasonic testing — Part 3: Spheroidal graphite cast iron castings"

!EN 13445-3:2014", Unfired pressure vessels — Part 3: Design

!EN 13445-5:2014", Unfired pressure vessels — Part 5: Inspection and testing

!EN 13445-6:2014", Unfired pressure vessels — Part 6: Requirements for the design and fabrication
of pressure vessels and pressure parts constructed from spheroidal graphite cast iron
!EN 13835:2012", Founding — Austenitic cast irons

!EN ISO 8062-3:2007", Geometrical Product Specifications (GPS) — Dimensional and geometrical
tolerances for moulded parts — Part 3: General dimensional and geometrical tolerances and machining
allowances for castings (ISO 8062-3:2007)

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15776:2011+A1:2015 (E)

3 Terms, definitions, units and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

3.1.1
grey cast iron
cast material, mainly iron and carbon based, carbon being present mainly in the form of flake (lamellar)
graphite particles (!EN 1561:2011")
!Note 1 to entry:" Grey cast iron is also known as flake graphite cast iron, and less commonly as lamellar
graphite cast iron.

!Note 2 to entry: Grey cast irons contain 2,0 % - 4,5 % carbon and 1 % - 3 % silicon. The structure consists of
branched and interconnected graphite flakes in a matrix which is pearlite, ferrite or a mixture."

3.1.2
spheroidal graphite cast iron
cast material, mainly iron and carbon-based, the carbon being present mainly in the form of spheroidal
graphite particles (!EN 1563:2011")
!Note 1 to entry:" Spheroidal graphite cast iron is also known as ductile iron, and less commonly as nodular
iron.

!Note 2 to entry:
The mechanical properties of grey irons can be greatly improved if the graphite shape is
modified if molten iron, having a composition in the range 3,2 % - 4,5 % carbon and 1,8 % - 2,8 % silicon, is
treated with magnesium. This produces castings with graphite in spheroidal form instead of flakes, known as
nodular, spheroidal graphite or ductile iron. Nodular irons are available with pearlite, ferrite or pearlite-ferrite
matrices which offer a combination of greater ductility and higher tensile strength than grey cast irons."

3.1.3

austenitic cast iron
!cast material with an austenitic matrix which is iron and carbon and silicon based and alloyed with
nickel and manganese, copper and/or chromium in order to stabilize the austenitic structure at room
temperature
Note 1 to entry:

The graphite can be present in flake or spheroidal form (EN 13835:2012)."

3.1.4
relevant wall thickness
!wall thickness representative of the casting, defined for the determination of the size of the cast
samples to which the guaranteed mechanical properties apply"
3.1.5
critical zone
highly stressed area where a fracture is expected to occur in a burst test
NOTE 1

It can be caused, for example, by any of the following:

—

sudden change in cross section;

—

sharp radii;

—

sharp edges;

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EN

—

peak stresses;

—

stresses due to other than membrane stress;

—
—

bending stresses;

changes in curvature.

NOTE 2
A critical zone is analysed by any appropriate method, e.g. holographic, interferometric method, strain
gauge methods, burst test, fatigue testing, FEM analysis, etc.

NOTE 3

Additionally, thermal gradients and thermal stresses due to different operating wall temperatures are
to be considered in defining critical zones.

3.1.6
purchaser
individual or organisation that buys pressure equipment, including assemblies or parts, for its own use
or on behalf of the user and/or operator

3.1.7
manufacturer
individual or organisation responsible for the design, fabrication, testing, inspection, installation of
pressure equipment and assemblies where relevant
NOTE 1

The manufacturer may subcontract one or more of the above mentioned tasks under its responsibility.

3.1.8
casting manufacturer
subcontractor that produces the castings used in the manufacture of pressure equipment

3.1.9
temperature factor
reduction factor applied to the 0,2 % proof strength to take account of temperature influence

3.1.10
wall thickness factor
reduction factor applied to the nominal design stress to take account of reduced mechanical properties
3.1.11
stress factor
ratio of peak stress to total stress

3.1.12
total stress
total stress in a design model which includes all stress concentration effects, non-local and local

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15776:2011+A1:2015 (E)

3.2 Symbols
!For the purposes of this document, symbols used in EN 13445-6:2014 are listed in Table 1."
Table 1 — Symbols

Symbol

Quantity

Unit

c

corrosion allowance

mm

analysis thickness

mm

e
ea
eact

emax
emin
f

fe

fm

required thickness
actual thickness

maximum local thickness at the location of a possible fatigue crack
initiation
minimum thickness as specified on drawing
nominal design stress

thickness correction factor

mean stress correction factor

ftest

nominal design stress for testing condition

fs

surface finish correction factor

fT

temperature correction factor

mC

exponent in equation of fatigue design curve

neq

number of equivalent full pressure cycles

A, A5

minimum elongation after fracture

n

T,Tc

calculation temperature

coefficient in equation of fatigue design curve

CT

temperature reduction factor

E
F

Keff

modulus of elasticity

test factor used in experimental fatigue assessment

mc

value from appropriate Tables 10, 11, 13, 14 in the appropriate
number of cycle number range used in fatigue calculations

Nall

mm

MPa

MPa

°C
%

MPa

effective stress concentration factor

theoretical elastic stress concentration factor

N

mm

wall thickness reduction factor

Kt
M

mm

shell shape factor

CC
Ce

mm

mean stress sensitivity factor

MPa

total number of envisaged types of pressure cycles with different
amplitude

allowable number of cycles obtained from the fatigue design curve

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EN 15776:2011+A1:2015
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EN

Symbol

Quantity

Nmin

minimum number of cycles obtained in experimental fatigue
assessment

ni

PC,pc

calculation pressure

MPa a

Pb,act

actual burst test pressure

MPa a

Pmax

maximum permissible pressure b

PT, pt

test pressure b

Pb

PD,pd
PS,ps

burst test pressure
design pressure

maximum allowable pressure b

MPa a
MPa a
MPa a
bar a
MPa

Rm

minimum tensile strength

!deleted text"

MPa

Rp0,2

minimum 0,2 % - proof strength

MPa

surface roughness parameter – peak – to - valley height

µm

Rp0,2/T

minimum 0,2 % - proof strength at temperature T in degrees Celsius

RM

material strength parameter

Rz

MPa
MPa

average strength from 3 tensile test samples

MPa"

V

maximum / minimum allowable temperature

°C

ΔP

pressure range

MPa a

allowable stress range

MPa

cut-off limit

MPa

!RM3
S
TSmax, TSmin

safety factor
volume

ΔPi

pressure cycle amplitude

Δσ*

pseudo elastic stress range

ΔσD

endurance limit

Δσ

ΔσCut
Δσeq,struc

structural stress range

ΔσR

stress range in fatigue design curve

ε

extra thickness due to casting process

δ

γR

η
ν

10

number of cycles with amplitude ΔPi

Unit

casting tolerance

partial safety factor
Stress factor

Poisson’s ratio

L

MPa
MPa
MPa
MPa
mm
mm


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15776:2011+A1:2015 (E)

a

b

Symbol

Quantity

Unit

σe

nominal design stress for external pressure

MPa

MPa for calculation purposes only, otherwise the unit shall be bar (1 MPa = 10 bar).
See also !EN 13445-3:2014", Table 4-1.

3.3 Inter relation of thicknesses definitions (!EN 13445-6:2014")

Key
e
ea
emin
eact
c

ε
δ

required thickness
analysis thickness
minimum thickness including corrosion allowance as indicated on drawings
actual thickness
corrosion allowance
extra thickness due to casting process
casting tolerance

Figure 1

4 Materials, limitations and service conditions
4.1 Materials and limitations on temperature, maximum allowable pressure and energy
content
!All material grades subject to internal or external pressure shall comply with EN 1561:2011 for grey
cast iron, EN 1563:2011 for spheroidal graphite cast iron and EN 13835:2012 for austenitic cast iron.
The material grades and corresponding limitations are given in Table 2 and Table 3.

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Table 2 — Allowable material grades and limitations for grey cast iron and austenitic lamellar

graphite cast iron
Material
standard

Material designation

Symbol

EN 1561:2011
EN 13835:2012

Number

EN-GJL-200

5.100

EN-GJL-300

5.1302

EN-GJL-250
EN-GJL-350

EN-GJLA-XNiCuCr15-6-2
EN-GJLA-XNiMn13-7

5.1301
5.1303
5.1500

5.1501

Design
temperature
range

Maximum
allowable
pressure PS

Maximum
energy content
PS × V for a
single casting

bar

bar ⋅ L

25

65 000

TSmin /TSmax
°C

- 10 ≤ T ≤ 200
- 10 ≤ T ≤ 200
- 10 ≤ T ≤ 200

The product PS × V, and the design temperature range of Table 2 for a single casting may be exceeded
only for material grades EN-GJL-300 1) and EN-GJL-3501) up to 300 °C and a product PS × V, as
appropriate, when all the following conditions are met:

— maximum allowable temperature TSmax ≤ 300 °C;

— maximum allowable pressure lowered from 25 bar to PS ≤ 15 bar;

— documented stress factor ≤ 2 throughout the casting;

— stress relief heat treatment is carried out when the maximum cooling rate in the mould exceeds 30
°C/h for the temperature range from 600 °C decreasing to 150 °C.
NOTE
An in-service inspection to Annex B of this standard may be considered to be mentioned in the
operating instructions of the part or vessel.

1) The requirements of particular material grades in this clause may allow the fabrication of paper cylinder and dryer rollers.

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15776:2011+A1:2015 (E)

Table 3 — Allowable material grades and design limits for spheroidal graphite cast iron
Material
standard

Material designation

Symbol

EN-GJS-400-15

EN-GJS-450-10
EN 1563:20
EN-GJS-500-7
11
EN-GJS-600-3
EN-GJS-700-2

EN-GJSA-XNiCr20-2

EN-GJSA-XNiCrNb20-2

EN 13835:2 EN-GJSA-XNiSiCr35-5-2
012
EN-GJSA-XNiCr30-3
EN-GJSA-XNiSiCr30-5-5
EN-GJSA-XNiCr35-3

Number

5.3106
5.3107
5.3200
5.3201

Design
temperature
range

Maximum
allowable
pressure

TSmin /TSmax

PS

°C

100
64

- 10 ≤ TS ≤ 300

5.3300
5.3500
5.3502
5.3505
5.3507
5.3508

bar

- 10 ≤ TS ≤ 540

5.3509

Maximum
energy content
PS × V for a
single casting
bar ⋅ L
100 000
80 000

25

65 000

64

80 000

25

65 000

64

80 000

NOTE
Whatever the used method the grades are based - on the mechanical properties from separately cast samples in a
sand mould or mould of comparable thermal diffusivity.

The applicable requirements for the delivery conditions, given in EN 1559-1:2011 and EN 1559-3:2011
shall also apply."

4.2 Cyclic loading

Lamellar and spheroidal graphite cast iron pressure vessels and vessel parts can be used for cyclic
operation. A fatigue analysis shall be performed if the service conditions require more than the
maximum number of full pressure cycles as given in Table 4, or more than an equivalent number of
cycles neq with smaller amplitude according to Equation (1).
Table 4 — Full pressure cycle number for dynamic loading consideration
Material grade
Grades according to Table 2
Grades according to Table 3

Maximum number of full pressure cycles without mandatory
fatigue analysis according to Equation (1)
(if stress factor η ≤ 3)
8 000

50 000

The calculation of an equivalent number of full pressure cycles neq when the operating pressure is less
than the maximum pressure shall be calculated according to Equation (1):

 ∆P 
=
neq ∑ n j ⋅  i 
j −1
 Pmax 

j−N

mc

(1)

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where

N
ni

∆Pi
Pmax

mC

is the total number of envisaged types of pressure cycles with different amplitude;
is the number of cycles with amplitude
is the pressure cycle amplitude;

∆Pi ;

is the maximum permissible pressure, as defined in !EN 13445-3:2014", 3.16;

is the value from Table 10 (lamellar graphite cast iron grades) or Table 11 (spheroidal graphite
cast iron grades) in the appropriate number of cycle range value for 103 < N < 106 or
106 < N < 108 whichever is the case.

NOTE
A stress factor – defined in 3.1.11 (ratio of peak stress to total stress-defined in 3.1.12) − greater than
3, determined by any of the design methods given in 5.8, can be the result of inappropriate design. By enlarging
radii or other small changes, an acceptable design may be generated. It is recommended to carry out a finite
element analysis to determine areas with possible excessive stress concentrations. !These area's may be also
found in feets, supports, lifting lugs, etc. which may influence stress distribution in the pressure part."

5 Design requirements
5.1 Design principle
The loadings to be accounted for shall be in accordance with !EN 13445-3:2014", Clause 5.

The materials, limitations and service conditions of Clause 4 of this standard shall be considered.

Design methods shall be in accordance with this European Standard and, when indicated in a clause of
this standard, with the relevant clauses of !EN 13445-6:2014".

If the geometry of the component or the loading case does not allow calculation by the formulas given in
!EN 13445-3:2014", design by analysis (DBA) or design by experiment (DBE) shall be applied.

Depending on the complexity of the component, the loading conditions and the level of NDT, the
designer may choose one of the following available design methods mentioned below. Correlation
between safety factor, testing factor and the method to assess dynamic loading is given in Table 5.

5.2 Conceptual design and construction drawings

The manufacturer analysis of hazards identifying those which apply to the pressure vessel on account of
pressure shall be documented and be of sufficient detail.

Details of the conceptual design including the design methods adopted, performance criteria and
construction drawings shall be provided. Guidance about the detailed dimensional information that
shall be provided is given in Annex B of !EN 13445-5:2014". Process diagrams, sub-assemblies or
other data relevant to conceptual design shall also be maintained.

5.3 Static loading
5.3.1 General

In order to design the part for static loading, the following shall be considered by the designer.
5.3.2 Design by formula (DBF)

Equations for the calculation of the various components of the pressure part are given in !EN 134453:2014"and !EN 13445-6:2014", Annex G. This Annex G gives additional equations for non14


BS EN 15776:2011+A1:2015
EN
(E)
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

standard shaped parts often used in casting design. Nominal design stress for component forms other
than bolts shall be calculated in accordance with Table 5. If design by experimental method is used, it
shall be in conformity with 5.3.4 of this standard. In general, the manufacturer shall specify to the
casting manufacturer which zones are critical related to the design and design loads. Other critical
zones may be indicated by the casting manufacturer related to the casting process and shall be taken

into account by the manufacturer.
Table 5 — Safety factor and nominal design stress

Item

Material grades according to
Table 3

Safety factor S

Material grades according to
Table 2

 15 
S=
3, 75 + 0,5 
− 1 
 A


Nominal design stress f

f =

R p 0,2 ⋅ CT ⋅ Ce

Grade
according to

As cast

Stress
relieve
annealed

!EN 1561:
2011"

S=9

S=7

!EN 13835
:2012"

S

S=8*

f =

Rm
S

S=6

where

CT is defined in 5.4;
Ce

Rm

is defined in 5.5;

is the tensile strength value for a given wall thickness according to Table A.1;

Rp0,2 is 0,2 % proof strength value according to Table A.4

where A5 is the elongation after fracture in percent according to !EN 1563:2011"and !EN 13835:2012".

* If a risk of stress corrosion cracking may exist, especially for austenitic grades at higher temperatures, a stress relief heat
treatment is beneficial depending on the service conditions but is left to the agreement between the parties concerned.

5.3.3 Design by analysis (DBA)

a) Decide whether the direct route (limit load, !EN 13445-3:2014", Annex B) or the stress
categorization method (!EN 13445-3:2014", Annex C) will be followed. Decide whether linear
or non-linear approach will be used;
b) base modelling and interpretation of calculation results shall be based on analysis thickness (ea)
and material characteristics at operation temperature;
c) for interpretation of calculation results, follow the evaluation procedures and assessment criteria in
order to evaluate the fitness for purpose of the real structure. These design checks and related
procedures are typical for the failure mode to be dealt with. For the different failure modes, see
!EN 13445-3:2014".
5.3.4 Design by experiment (DBE)

Where design by equations (DBF) according to !EN 13445-3:2014"is not considered appropriate
due to the complex shape of the component, then a hydraulic burst test to determine the analysis
thickness ea and the minimum thickness emin shall be performed according to the procedure in 5.8.2.4.

This test is also a part of the technical documentation.
15


BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

NOTE 1
For vessels for which PS × V < 6 000 bar × L (600 MPa × L) an experimental method may be applied as
an alternative to the design by formulae (DBF) or design by analysis (DBA) methods.

NOTE 2
For vessels for which PS × V ≥ 6 000 bar × L (600 MPa × L) the experimental method may be used in
addition to detailed design.

5.4 Temperature reduction factor

For grey cast iron material grades according to !EN 1561:2011"and austenitic lamellar graphite
cast iron material grades according to !EN 13835:2012"mechanical properties shall be considered
to remain constant for the temperature range - 10 °C up to 200 °C.

For spheroidal graphite cast iron material grades according to !EN 1563:2011":
CT = 1 for T ≤ 20 °C

CT = 1 – 0,001(T - 20) for 20 °C < T ≤ 300 °C 2)

For austenitic spheroidal graphite cast iron material grades according to !EN 13835:2012":

CT = 1 for T ≤ 20 °C

CT = 1 – 0, 000 5 (T - 20) for 20 °C < T ≤ 540 °C

5.5 Wall thickness reduction factor

(2)

(3)

(4)

(5)

For spheroidal graphite cast iron material grades according to !EN 1563:2011"and
!EN 13835:2012":
Ce = 1 for emin ≤ 60 mm

Ce = 0,8 for 60 mm < emin ≤ 200 mm

(6)

(7)

NOTE
The wall thickness reduction factor for lamellar graphite cast iron grades according to
!EN 1561:2011"is already included in Table A.1 in this standard and needs no extra thickness correction
factor.

5.6 Design for external pressure

Design for external pressure shall be carried out according to !EN 13445-3:2014", Clause 8, with
the following modifications:
Replace Equations 8.4.2-1, 8.4.2-2, 8.4.3-1, 8.4.3-2 by:

=
σ e R p 0,2/T ⋅ Ce

The minimum safety factor, which applies throughout this clause, is given by:
— for material grades according to Table 2:

S = (safety factor according to Table 5) + 1

— for material grades according to Table 3:
2) See Bibliography ref. [13].

16

(8)

(9)


BS EN 15776:2011+A1:2015
EN
(E)
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

S = (safety factor according to Table 5) + 0,5

(10)

5.7 Testing conditions

The test pressure may exceed the value given in Equation (15) either intentionally or occasionally.
However, the nominal design stress for testing conditions, ftest shall not exceed the following values.

For material grades according to Table 2:

ftest =

Rm
2

(11)

For material grades according to Table 3:

ftest =

R p 0,2/Ttest ⋅ Ce

(12)

1,33

5.8 Design methods
5.8.1 General

Design methods shall be in accordance with this standard and, when indicated in the clauses of this
standard, with the clauses of !EN 13445-6:2014".
5.8.2 Static loading
5.8.2.1 General
In order to design the part for static loading, the following options can be considered by the designer.
5.8.2.2 Design by formula (DBF)

Formulas for the calculation of the various components of the pressure part are given in !EN 134453:2014".
5.8.2.3 Design by analysis (DBA)

For cast iron pressure vessels the general procedures and corresponding rules are covered by
!EN 13445-6:2014", Annex E "Design by analysis for castings" with the following modifications:

— additional to !EN 13445-6:2014", Annex E.2.1 "Design checks for normal operating load cases"
Material strength parameters (RM) and partial safety factors (γR) shall be as given in Table 6:
Table 6 — RM and γR for normal operating load cases

a)

Material grade

RM

γR

According to Table 2

Rm

S/1,8 a

According to Table 3

S according to Table 5.

Rp0,2/T

S/(1,8 × Ce) a

— additional to !EN 13445-6:2014", Annex E.2.2 "Design checks for testing load cases"
RM and γR shall be as given in Table 7 and Table 8:

17


BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

Table 7 — RM and γR for test load case lamellar cast iron grades
Material grade

RM

γR

According to Table 2

Rm

2,0

Material grade

RM

γR

According to Table 3

Rp0,2/Ttest

1,33/Ce

Table 8 — RM and γR for test load case spheroidal graphite cast iron grades

5.8.2.4 Design by experiment (DBE)

Design by experiment shall be carried out according to !EN 13445-6:2014", 5.2.2.1.5, where:

— for material grades according to Table 2 of this standard, the following formula applies:
1/2

 S ⋅ PS ⋅ Rm(3) 
e=
eact ⋅ 
a
 P ⋅ R 

 b ,act m 

(13)

— for material grades according to Table 3 of this standard, the following formula applies:
1/ n

S ⋅ PS ⋅ Rm(3)


e=
e
⋅


a
act 
P
R
C
C
⋅
⋅
⋅
b
act
p
T
e
,

0,2



(14)

where

n = 1 for curved surfaces (cylinders, spheres) or cones with angles α ≤ 60°, stayed surfaces and
stressed parts when it can be shown that the bending stress is less than 2/3 of the total stress;

n = 2 for all other surfaces except when it can be shown that the bending stress is less than 2/3 of
the total stress.

5.8.2.5 !RM3" Determination and general test requirements

For determining !RM3" three tensile test specimen shall be performed in accordance with
!EN 1561:2011", !EN 1563:2011"or !EN 13835:2012"material standards for each of the
required positions taken from the same cast.
The specimen positions shall be in accordance with the specifications in the technical delivery
conditions of the product form for materials for pressure equipment. In addition to the requirements of
the material, the manufacturer and the purchaser may agree on the properties required at stated
positions in the casting. These properties shall be determined by testing machined test pieces cut from
the casting at these stated positions. The mean value of the three specimens shall be used to determine
the ratio of !RM3"/Rm.

Specimen may be taken before the burst test on an identical part or on the same part after burst test. It
is not allowed to use scaled-down part of the part under investigation. 3)

The position on the casting from where the sample is cut shall be in an area where the casting wall

thickness is close to the relevant wall thickness of the casting. For the purpose of determining the size of
3) When taking values after burst testing these may show lower tensile strength properties for some grades and should only
be used with caution in exceptional cases (single part or very large part, etc.).

18


BS EN 15776:2011+A1:2015
EN
(E)
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

the test pieces to be used, the purchaser shall, by the time of acceptance of the order, indicate to the
manufacturer which are the important sections. In the absence of any direction by the purchaser, the
manufacturer may choose the size of the test piece to be used according the relevant standard.

No specimen may show a lower value than the minimum value of Rm stated in the respective material
standards of the material grade under investigation, taking into account the corresponding thickness.

The preferred test piece diameter is 14 mm, but, for technical reasons and for test pieces machined
from castings, it is permitted to use a test piece of different diameter or equivalent diameter.
Retesting shall be carried out if a test is not valid. A test is not valid if there is:
—

a faulty mounting of the test piece or defective operation of the test machine;

—

a fracture of the tensile test piece outside the gauge length;

—

—

a defective test piece because of incorrect pouring or incorrect machining;

a casting defect in the test piece, evident after fracture.

In all cases, a new test piece shall be taken from the same sample or a duplicate sample cast at the same
time. The result of the retest shall be used.
5.8.2.6 Determination of the minimum hydraulic burst pressure and maximum allowable
pressure for static loading

For the purposes of this standard the methods given in !EN 13445-6:2014", 5.2.2.1.6 to determine
the minimum hydraulic burst pressure and maximum allowable pressure for static loading apply with
the following modification:
Replace in formulae 5-3 and 5-4 n as follows:

— for material grades given in Table 2, n = 2 applies in all cases of curvature of the pressure part;
— for material grades given in Table 3, see 5.2.2.1.6 of !EN 13445-6:2014".
5.8.3 Dynamic loading
5.8.3.1 General

If the number of full pressure cycles or equivalent full pressure cycles according to Equation (1) exceeds
the number of full pressure cycles for static loading considered in Table 4, a fatigue assessment of the
complete design is required. In order to design the part for dynamic loading, the following options can
be considered by the designer:

— a simplified fatigue assessment (maximum allowable number of equivalent pressure fluctuations);

or
— a detailed fatigue assessment (maximum allowable number of equivalent pressure fluctuations
using detailed stress analysis which is less conservative than the simplified method).
5.8.3.2 Simplified fatigue assessment (SFA)

A simplified fatigue assessment will give a maximum allowable number of equivalent pressure
fluctuations under service conditions.

The assessment shall be performed according to !EN 13445-6:2014", Annex D with equation
modifications as listed in Table 9 and coefficients of Table 10 and Table 11 for mC and CC.
19


BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

Table 9 — Equations for simplified fatigue assessment
Equation and definition in
!EN 13445-6:2014", Annex D
D.6.1.

Pseudo
elastic
stress range

D.6.2, D.6.3

Correction factor
for wall thickness

D.6.4

D.6.4
D.6.5

D.6.8

20

temperature
correction factor
for
ferritic/pearlitic
materials
temperature
correction factor
for
pearlitic
materials only
temperature
correction factor
for
austenitic
materials
Stress
fatigue
curve

range,
design

Symbol

Equation for material
grades according to Table
2 of this standard
Replace

Δσ*

fe

!EN 13445-6:2014",
Annex D Equation 6.1 by

∆P ⋅η ⋅ f
∆σ * =
Pmax

f e = 1 for all

fT

fT

As
!EN 134456:2014", D.6.4

n.a.

fT = 1

for

design

temperature range (°C) - 10
≤ T ≤ 300
for design
temperature range
limited to (°C) - 10 ≤ T
≤ 350

Replace

∆σ R

Same as !EN 134456:2014", D.6.1
As
!EN 134456:2014", D.6.2 and D.6.3

thicknesses

fT

Equation for material
grades according to

Table 3 of this standard

!EN 13445-6:2014",
Annex D.6.8 by

C ⋅R
∆σ R =C 1 m

n.a.
As
!EN 134456:2014", D.6.5
Replace

!EN 13445-6:2014",
D.6.8 by

C
∆σ R =C1

N mC

N mC

D.6.9

Allowable number
of cycles

D.6.10

Allowable
range

stress

Replace
N

!EN 134456:2014", D.6.9 by

C ⋅R 
N =  C *m 
 ∆σ 
∆σ

mc

Replace criterion by

∆σ ≤ ∆σ R

Replace

!EN 134456:2014", D.6.9 by

 C 
N =  C* 
 ∆σ 

mc

As
!EN 134456:2014",
Annex D,
Equation 6.10


BS EN 15776:2011+A1:2015
EN
(E)
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

Table 10 — Coefficients of the fatigue design curves for lamellar graphite cast iron grades
according to Table 2 (NOTE) − Simplified assessment
Material grades
according to Table 2

As cast

Stress relieve annealed

Constants of fatigue design curve
ΔσR – N
103 < N < 106

106 < N < 108

mC

CC

mC

CC

7

1,440

10

0,797

7

1,830

10

1,012

Allowable stress range at N cycles MPa
ΔσD at N = 106

Δσcut at N = 108

0,254 × Rm

0,160 × Rm

0,200 × Rm

0,126 × Rm

NOTE
See Table 2 of this standard for allowed lamellar graphite cast iron grades taken from
!EN 1561:2011"and !EN 13835:2012".

An example of a fatigue design curve for simplified assessment is given in informative Annex C.

Table 11 — Coefficients of the fatigue design curves for spheroidal graphite cast iron grades
according to !EN 1563:2011"and !EN 13835:2012"and Table 3 − Simplified assessment
Material grade according
to Table 2

Constants of fatigue design curve ΔσR – N
103 < N < 2 × 106

2 × 106 < N < 108

900

555

1 059

653

mC

EN-GJS-400-15
EN-GJS-450-10
EN-GJS-500-7
EN-GJS-600-3

7,5

EN-GJS-700-2

EN-GJSA-XNiSiCr35-5-2
EN-GJSA-XNiCr30-3
EN-GJSA-XNiCr35-3

EN-GJSA-XNiSiCr30-5-5

8,6

5.8.3.3 Detailed fatigue assessment (DFA)

mC

983

CC

606

1 218
1 370

EN-GJSA-XNiCr20-2

EN-GJSA-XNiCrNb20-2

CC

750
10

845

Allowable stress
range at N cycles MPa
ΔσD at
N = 106

Δσcut at
N = 108

142

96

130

88

153

103

198

134

176

119

573

452

106

72

637

504

118

80

A detailed fatigue assessment returns a value of maximum allowable number of equivalent pressure
fluctuations using detailed stress analysis in service conditions.

The assessment shall be performed according to !EN 13445-6:2014", Annex D with modifications

to equations and coefficients of Table 13 and Table 14 for mC and CC as listed in Table 12, Table 13 and
Table 14.

21


BS EN 15776:2011+A1:2015
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)
(E)
EN

Table 12 — Equations for detailed fatigue assessment
Equation in
!EN 134456:2014"Annex
D
D.7.1
D.7.2
D.7.3
D.7.4, D.7.5

7.2.2

D 7.7
D.7.8

Symbol

Pseudo elastic
stress range

Δσ*

As !EN 13445-6:2014", D.7.1

Keff

Theoretical
elastic
stress
concentration
factor

As !EN 13445-6:2014", D.7.2

Kt

As !EN 13445-6:2014", D.7.3

Effective stress
concentration
factor

Correction factor
for
wall
thickness
Correction factor
for temperature
for

ferritic/pearlitic
materials
Correction factor
for temperature
for
pearlitic
materials

22

Surface
finish
correction factor
Correction
for
mean stress

D.7.9

Stress
fatigue
curve

D.7.10

Allowable
number of cycles

D.7.11

Equation for
material grades
according to
Table 3

Item

Correction factor
for temperature
for
austenitic
materials
D.7.6

Equation for material grades
according to Table 2

range,
design

Allowable
structural stress
range

fe

f e = 1 for all thicknesses

ft

n.a<

ft

ft = 1 for design temperature range 10 ≤ TS ≤ 300

ft

ft = 1 for design temperature range 10 ≤ TS ≤ 350

fs
Fs

ΔσR

fs = 1 if N > 106

R 
1 − 0.06 ⋅ log ( RZ ) ⋅ log  m 
Fs :=
 50 

Replace

!EN 13445-6:2014", D.7.9 by

C ⋅R
∆σ R =C 1 m
N mc

C ⋅R 
N =  C *m 
 ∆σ 
Replace

As
!EN 134456:2014", D.6.5
As
!EN 134456:2014", D.7.6
and D.7.7

As
!EN 134456:2014", D.7.8

M = 0,5

N

Δσeq.struc

As
!EN 134456:2014", D.6.4

f s = FS( 0,105 ln N )−0,465

M

As
!EN 134456:2014", D.7.4
and D.7.5

mc

Replace

!EN 134456:2014", D.7.9
by

C
∆σ R =1C
N mc

 C 
N =  C* 
 ∆σ 

!EN 13445-6:2014", D.7.9 by D.7.11

mc


BS EN 15776:2011+A1:2015
EN
(E)
EN 15776:2011+A1:2015
15776:2011+A1:2015 (E)

Table 13 — Coefficients of the fatigue design curves for lamellar graphite cast iron grades
according to !EN 1561:2011"and !EN 13835:2012"and Table 2 – Detailed assessment
Material grades according to

Table 2

Constants of fatigue design curve

Allowable stress range
at

ΔσR – N

N cycles

103 < N < 106

mC
As cast

Stress relieve annealed

7

CC

2,694
3,417

106 < N < 108

mC
10

CC

1,49
1,89

MPa

ΔσD at 106

Δσcut at 108

0,475 × Rm

0,300 × Rm

0,374 × Rm

0,236 × Rm

Table 14 — Coefficients of the fatigue design curves for spheroidal graphite cast iron grades
according to !EN 1563:2011"and !EN 13835:2012"and Table 3 − Detailed assessment
Material grade according
to Table 3

Constants of fatigue design curve ΔσR – N
103 < N < 2 × 106

2 × 106 < N < 108

mC

mC

CC

CC

EN-GJS-400-15

1 041

1 041

EN-GJS-500-7

1 255

1 255

EN-GJS-450-10

1 240

EN-GJS-600-3
EN-GJS-700-2

EN-GJSA-XNiCr20-2

EN-GJSA-XNiCrNb20-2

EN-GJSA-XNiSiCr35-5-2
EN-GJSA-XNiCr30-3
EN-GJSA-XNiCr35-3

EN-GJSA-XNiSiCr30-5-5

1 240

1 323
10

1 421

1 323
10

1 421

Allowable stress range
at N cycles
MPa

ΔσD at
N = 2 × 106

Δσcut at
N = 108

291

197

244
294
310
333

165
199
210
225

850

850

199

135

947

947

222

150

An example of a fatigue design curve for detailed assessment is given in informative Annex C.
5.8.3.4 Assessment rule for total fatigue damage

The assessment shall be carried out to the method described in !EN 13445-6:2014", D.8.
5.8.3.5 Experimental fatigue assessment (EFA)

The method as described in !EN 13445-6:2014", Annex H shall be used if stress analysis is
inadequate or the design analysis shows abnormal low calculated fatigue life values indicating a too
conservative approach by theory.

23