Closed expansion vessels with built in diaphragm for installation in water

This European Standard specifies requirements for the design, manufacture and testing of closed expansion vessels with built in diaphragm, which will hereinafter be called "vessels", and
a)   whose diaphragm serves to separate water on the one hand and air / nitrogen on the other hand in heating/cooling systems or fresh water systems;
b)   which are manufactured singly or in series;
c)   which may consist partly or entirely of (cold) deep-drawn parts;
d)   whose parts may be joined by welding, clenching or flanges;
e)   whose size is not limited;
f)   whose maximum allowable pressure is greater than 0,5 bar, yet not exceeding 30 bar;
g)   whose upper wall thickness is limited to 12 mm for austenitic steels and 15 mm for ferritic steels;
h)   whose minimum operating temperature is not below -10 °C, whose maximum operating temperature is not above 70 °C.
NOTE   The maximum operating temperature of 70 °C is determined by the characteristics of the diaphragm materials. It may be higher, if suitability of diaphragm material is proven.
Whatever the temperature in the heating system, for the vessel operation the decisive factor is the maximum operating temperature of the diaphragm. It is the system designer's responsibility to prescribe measures to protect the diaphragm from unsuitable temperatures (e.g. connection to the coldest part of the system in a heating system, to the warmest in a refrigeration circuit; thermostatic monitoring of connection to vessel or intermediate vessel).
For cases where operating temperatures above 70 °C cannot be avoided the suitability of the diaphragm material is to be proven (see Clause 8).
When reference is made in this European Standard to EN 13445-1, -2, -3, -4 and -5 respectively, all relevant provisions in the concerned clauses of these standards need to apply.

Ausdehnungsgefäße mit eingebauter Membrane für den Einbau in Wassersystemen

Diese Europäische Norm legt Anforderungen an die Konstruktion, Herstellung und Prüfung von geschlos¬senen Ausdehnungsgefäßen mit eingebauter Membrane fest, die im Folgenden Gefäße genannt werden und
a)   deren Membranen zur Trennung von Wasser einerseits und Luft/Stickstoff andererseits in Heizungs /Kühl¬systemen oder Frischwassersystemen dienen;
b)   die in Einzel  oder Serienfertigung hergestellt werden;
c)   die teilweise oder ganz aus (kalt )tiefgezogenen Teilen bestehen;
d)   deren Einzelteile durch Schweißen, Klemmen oder Flansche verbunden werden können;
e)   deren Größe nicht begrenzt ist;
f)   deren maximal zulässiger Druck mehr als 0,5 bar beträgt, jedoch 30 bar nicht überschreitet;
g)   deren Wanddicke auf 12 mm bei austenitischen Stählen und 15 mm bei ferritischen Stählen begrenzt ist;
h)   deren Mindest Betriebstemperatur nicht unter -10 °C und deren maximale Betriebstemperatur nicht über 70 °C liegt.
ANMERKUNG   Die maximale Betriebstemperatur von 70 °C hängt von den Eigenschaften des Membranenwerkstoffes ab. Sie kann höher sein, wenn die Eignung des Membranenwerkstoffes nachgewiesen ist.
Wie hoch die Temperatur des Heizungssystems auch sein mag, der entscheidende Faktor für den Gefäßbetrieb ist die maximale Betriebstemperatur der Membrane. Der Konstrukteur des Systems ist verantwortlich dafür, notwendige Maßnahmen vorzuschreiben, um die Membrane vor ungeeigneten Temperaturen zu schützen (z. B. Anschluss an den kältesten Teil des Systems bei einem Heizungssystem oder an den wärmsten in einem Kühlkreislauf; thermostatische Überwachung des Anschlusses an das Gefäß oder Zwischengefäß).
In Anwendungsfällen, in denen Betriebstemperaturen über 70 °C nicht vermieden werden können, ist die Eignung des Membranenwerkstoffes nachzuweisen (siehe Abschnitt 8).
Bei einem Verweis in dieser Europäischen Norm auf EN 13445 1, EN 13445 2, EN 13445 3, EN 13445 4 bzw.  EN 13445 5 gelten sämtliche zutreffenden Festlegungen in den entsprechenden Abschnitten der Norm.

Vases d'expansion fermés avec membrane incorporée pour installation dans des systemes a eau

La présente Norme européenne spécifie les exigences relatives a la conception, a la fabrication et aux essais des vases d'expansion fermés avec membrane incorporée, qui sont désignés ci-apres « vases », et
a)   dont la membrane permet de séparer l'eau, d'une part, et l'air / azote, d'autre part, dans les systemes de chauffage/refroidissement ou de systemes d'eau douce ;
b)   qui sont fabriqués a l’unité ou en série ;
c)   qui peuvent comporter, partiellement ou entierement, des parties formées par emboutissage profond a froid ;
d)   dont les parties peuvent etre assemblées par soudage, par sertissage ou par brides ;
e)   dont la dimension n'est pas limitée ;
f)   dont la pression maximale admissible est supérieure a 0,5 bar, tout en n'excédant toutefois pas 30 bar ;
g)   dont l'épaisseur de la paroi dans la partie supérieure est limitée a 12 mm pour les aciers austénitiques et a 15 mm pour les aciers ferritiques ;
h)   dont la température minimale en service n'est pas inférieure a -10 °C, et dont la température maximale en service n'est pas supérieure a 70 °C.
NOTE   La température maximale en service de 70 °C est déterminée par les caractéristiques du matériau de membrane. Cette température peut etre supérieure, si le caractere approprié du matériau de la membrane est démontré.
Quelle que soit la température du systeme de chauffage, la température maximale en service de la membrane constitue le facteur déterminant pour le fonctionnement du vase. Le concepteur du systeme doit prescrire des mesures visant a protéger la membrane contre des températures inappropriées (par exemple raccordement a la partie la plus froide du systeme dans le cas d'un systeme de chauffage, ou a la partie la plus chaude dans un groupe frigorigene ; contrôle thermostatique du raccordement au vase ou au récipient intermédiaire).

Zaprte ekspanzijske posode z vgrajeno membrano za vodne napeljave

General Information

Status
Published
Publication Date
14-Oct-2007
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
25-Sep-2007
Due Date
30-Nov-2007
Completion Date
15-Oct-2007

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Closed expansion vessels with built in diaphragm for installation in waterZaprte ekspanzijske posode z vgrajeno membrano za vgradnjo v vodne inštalacijeVases d'expansion fermés avec membrane incorporée pour installation dans des systemes a eauAusdehnungsgefäße mit eingebauter Membrane für den Einbau in WassersystemenTa slovenski standard je istoveten z:EN 13831:2007SIST EN 13831:2007en,fr,de91.140.10Sistemi centralnega ogrevanjaCentral heating systemsICS:SLOVENSKI

STANDARDSIST EN 13831:200701-november-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13831August 2007ICS 91.140.10 English VersionClosed expansion vessels with built in diaphragm for installationin waterVases d'expansion fermés avec membrane incorporée pourinstallation dans des systèmes à eauAusdehnungsgefäße mit eingebauter Membrane für denEinbau in WassersystemenThis European Standard was approved by CEN on 26 July 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36

B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13831:2007: E

EN 13831:2007 (E) 2 Contents Page Foreword..............................................................................................................................................................4 Introduction.........................................................................................................................................................5 1 Scope......................................................................................................................................................6 2 Normative references............................................................................................................................6 3 Terms and conditions...........................................................................................................................7 4 Symbols and units.................................................................................................................................9 5 Materials...............................................................................................................................................10 5.1 General..................................................................................................................................................10 5.2 Materials proven by experience and current use.............................................................................10 5.3 Fasteners..............................................................................................................................................11 5.4 Non-pressurised parts........................................................................................................................11 6 Design and calculation........................................................................................................................11 6.1 Design...................................................................................................................................................11 6.1.1 Requirements pertaining to the diaphragm......................................................................................11 6.1.2 Requirements pertaining to fresh water application........................................................................11 6.1.3 Outside finish.......................................................................................................................................11 6.1.4 Inspection openings............................................................................................................................11 6.1.5 Connections.........................................................................................................................................12 6.1.6 Clenched joints....................................................................................................................................12 6.1.7 Volume tolerance of vessels..............................................................................................................12 6.1.8 Fatigue..................................................................................................................................................12 6.1.9 Loadings...............................................................................................................................................13 6.2 Experimental design method..............................................................................................................13 6.2.1 General..................................................................................................................................................13 6.2.2 Preparations.........................................................................................................................................13 6.2.3 Vessels with PS × V ≤ 1 000 bar × L....................................................................................................13 6.2.4 Vessels with 1 000 bar × L < PS × V < 6 000 bar × L...........................................................................13 6.2.5 Vessel parts and components............................................................................................................13 6.3 Calculation method..............................................................................................................................14 6.3.1 General..................................................................................................................................................14 6.3.2 Symbols................................................................................................................................................14 6.3.3 Cylindrical and spherical shells under internal pressure...............................................................15 6.3.4 Dished ends under internal pressure................................................................................................15 6.3.5 Openings in cylindrical shells, spherical shells and dished ends.................................................18 6.3.6 Bolted circular flat ends under internal pressure............................................................................25 6.3.7 Flanges and boltings...........................................................................................................................31 7 Manufacturing and welding................................................................................................................39 7.1 Introduction..........................................................................................................................................39 7.2 General..................................................................................................................................................39 7.3 Manufacturing tolerances...................................................................................................................39 7.3.1 General..................................................................................................................................................39 7.3.2 Middle line and surface alignment.....................................................................................................39 7.3.3 Tolerances for vessels........................................................................................................................40 7.4 Weld details..........................................................................................................................................41 7.4.1 Recommended weld details................................................................................................................41 7.4.2 Vessels made in more courses..........................................................................................................42 7.4.3 Joggle joints.........................................................................................................................................42 7.5 Welding.................................................................................................................................................42 7.5.1 General..................................................................................................................................................42

EN 13831:2007 (E) 3 7.5.2 Welding procedure specification (WPS)...........................................................................................42 7.5.3 Qualification of WPS...........................................................................................................................42 7.5.4 Qualification of welders and welding operators..............................................................................42 7.5.5 Preparation of edges to be welded....................................................................................................43 7.5.6 Execution of welded joints.................................................................................................................43 7.5.7 Attachments, supports and stiffeners...............................................................................................43 7.6 NDE personnel.....................................................................................................................................43 7.7 Manufacture and testing of permanent joints..................................................................................43 7.7.1 Welded joints.......................................................................................................................................43 7.7.2 Clenched joints....................................................................................................................................46 7.8 Forming of parts subject to pressure................................................................................................46 7.8.1 Ratio of deformation...........................................................................................................................46 7.8.2 Forming conditions.............................................................................................................................48 7.8.3 Heat treatment.....................................................................................................................................48 7.8.4 Visual examination and control of dimensions................................................................................49 7.8.5 Test certificate.....................................................................................................................................49 7.9 Repairs..................................................................................................................................................49 7.9.1 Surface defects....................................................................................................................................49 7.9.2 Repairs, elimination of defects..........................................................................................................49 7.10 Finishing operations...........................................................................................................................49 8 Diaphragm............................................................................................................................................50 8.1 General.................................................................................................................................................50 8.2 Materials...............................................................................................................................................50 8.3 Hygienic demands...............................................................................................................................50 8.4 Test concept........................................................................................................................................50 8.5 Testing..................................................................................................................................................50 8.5.1 General.................................................................................................................................................50 8.5.2 Tests on diaphragms..........................................................................................................................50 8.5.3 Cyclic stressing on vessels...............................................................................................................51 8.5.4 Diaphragm permeability test..............................................................................................................53 8.5.5 Repetition of tests...............................................................................................................................53 8.5.6 Test report............................................................................................................................................53 8.6 Tests by the diaphragm manufacturer..............................................................................................54 8.7 Marking of diaphragms.......................................................................................................................54 9 Testing and inspection.......................................................................................................................54 9.1 General.................................................................................................................................................54 9.2 Technical documentation...................................................................................................................54 9.3 Inspections during manufacturing....................................................................................................55 9.4 Pressure test........................................................................................................................................55 9.5 Marking.................................................................................................................................................55 9.6 Documentation....................................................................................................................................56 Annex A (informative)

Standards for testing diaphragms............................................................................57 Annex B (informative)

Proven diaphragm materials.....................................................................................58 Annex ZA (informative)

Relationship between this European Standard and the Essential requirements of EU Directive 97/23/EC.............................................................................................59 Bibliography......................................................................................................................................................60

EN 13831:2007 (E) 4 Foreword This document (EN 13831:2007) 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 February 2008, and conflicting national standards shall be withdrawn at the latest by February 2008. 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.

EN 13831:2007 (E) 5

Introduction Closed expansion vessels with built in diaphragm made their commercial début in the early 1950s. They were employed in heating systems, or for fresh water supply systems. When used in heating systems they take up the increase of the water volume due to the heating up. The gas pressure (on the other side of the diaphragm) pushes the water back into the system when due to cooling down the water volume in the heating system is decreasing. Expansions vessels with built in diaphragm are an undisputed standard in European heating engineering. When used in fresh water circuits, vessels with built in diaphragm serve to accommodate the extra volume caused by water heaters warming up,, thus saving valuable drinking water from flowing down the drain. The other main application is to store water under pressure in connection with booster systems allowing an energy efficient pump operation. Though the development of the closed expansion vessel with built in diaphragm constituted a real revolution in the domains of heating and drinking water, industry in general took only limited note of it. Nevertheless this has not prevented the manufacturers from refining the product and the manufacturing technique over the last 40 years, often charting entirely new paths. As a consequence, the production of closed expansion vessels can differ considerably from conventional pressure vessel production. This is especially true in respect to the highly developed deep drawing technology.

EN 13831:2007 (E) 6 1 Scope This European Standard specifies requirements for the design, manufacture and testing of closed expansion vessels with built in diaphragm, which will hereinafter be called "vessels", and

a) whose diaphragm serves to separate water on the one hand and air / nitrogen on the other hand in heating/cooling systems or fresh water systems; b) which are manufactured singly or in series; c) which may consist partly or entirely of (cold) deep-drawn parts; d) whose parts may be joined by welding, clenching or flanges; e) whose size is not limited; f) whose maximum allowable pressure is greater than 0,5 bar, yet not exceeding 30 bar; g) whose upper wall thickness is limited to 12 mm for austenitic steels and 15 mm for ferritic steels; h) whose minimum operating temperature is not below –10 °C and whose maximum operating temperature is not above 70 °C. NOTE The maximum operating temperature of 70 °C is determined by the characteristics of the diaphragm materials. It may be higher, if suitability of diaphragm material is proven. Whatever the temperature in the heating system, for the vessel operation the decisive factor is the maximum operating temperature of the diaphragm. It is the system designer's responsibility to prescribe measures to protect the diaphragm from unsuitable temperatures (e.g. connection to the coldest part of the system in a heating system, to the warmest in a refrigeration circuit; thermostatic monitoring of connection to vessel or intermediate vessel). For cases where operating temperatures above 70 °C cannot be avoided the suitability of the diaphragm material is to be proven (see Clause 8). When reference is made in this European Standard to EN 13445-1, EN 13445-2, EN 13445-3, EN 13445-4 and EN 13445-5 respectively, all relevant provisions in the concerned clauses of these standards need to apply. 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 287-1:2004, Qualification test of welders — Fusion welding — Part 1: Steels EN 473:2000, Non destructive testing — Qualification and certification of NDT personnel — General principles EN 764-1:2004, Pressure equipment — Part 1: Terminology — Pressure, temperature, volume, nominal size EN 764-2:2002, Pressure equipment: terminology — Part 2: Quantities, symbols and units EN 764-3:2002, Pressure equipment — Part 3: Definition of parties involved EN 895:1995, Destructive tests on welds in metallic materials — Transverse tensile test EN 910:1996, Destructive test on welds in metallic materials — Bend tests

EN 13831:2007 (E) 7 EN 1418:1997, Welding personnel — Approval testing of welding operators for fusion welding and resistance weld setters

for fully mechanized and automatic welding of metallic materials EN 1435:1997, Non-destructive examination of welds — Radiographic examination of welded joints EN 10204:2004, Metallic products — Types of inspection documents EN 10269:1999, Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties EN 13445-1:2002, Unfired pressure vessels — Part 1: General EN 13445-2:2002, Unfired pressure vessels — Part 2: Materials EN 13445-3:2002, Unfired pressure vessels — Part 3: Design EN 13445-4:2002, Unfired pressure vessels — Part 4: Fabrication EN 13445-5:2002, Unfired pressure vessels — Part 5: Inspection and testing EN ISO 898-1:1999, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs (ISO 898-1:1999) EN ISO 15609-1:2004, Specification and qualification of welding procedures for metallic materials — Welding procedure specification — Part 1: Arc welding (ISO 15609-1:2004) EN ISO 15613:2004, Specification and qualification of welding procedures for metallic materials — Qualification based on pre-production welding test (ISO 15613:2004) EN ISO 15614-1:2004, Specification and qualification of welding procedures for metallic materials — Welding procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys (ISO 15614-1:2004) ISO 898-2:1998, Mechanical properties of fasteners — Part 2: Nuts with specified proof load values — Coarse thread 3 Terms and conditions For the purposes of this document, the terms and definitions given in EN 764-1:2004, EN 764-2:2002, EN 764-3:2002 and the following apply. 3.1 automatic welding welding in which all the parameters are automatically controlled, some of these parameters may be adjusted to a limited amount (manually or automatically by mechanical or electronic devices) during welding to maintain the specified welding conditions 3.2 clench joints separate metal ring holding together two vessel parts or a rolled joint holding together two vessel parts in a permanent way. Its design is always done according to the experimental design method 3.3 expansion vessel vessel to take up the volume variations of a liquid due to changes of temperature. The expansion vessel is called "closed", if the liquid contained is not in contact with any gaseous or liquid medium

EN 13831:2007 (E) 8 3.4 deep drawing forming of vessel parts from a flat state into a three dimensional state by means of a press and tools whereby no material is taken off or added 3.5 diaphragm flexible and / or elastic wall which is fastened into the vessel inside in a gas tight way and separates the vessel into a water and a gas space 3.6 experimental test any kind of test used to substitute for the calculation of a vessel part or the whole vessel, within the framework of the experimental design method 3.7 inspection document document according to EN 10204:2004 3.8 family of welded joints welded joints covered by a specific welding procedure approval document 3.9 vessel family vessels belong to one vessel family if they have similar geometrical proportions, same design and fall within the validity of one weld procedure approval 3.10 freshwater water coming from a supply system (mains, well etc.), untreated apart from possible hygienic measures, with natural content of oxygen

EN 13831:2007 (E) 9 4 Symbols and units For the purposes of this document, the symbols and units given in EN 13445-1:2002, EN 13445-2:2002,

EN 13445-3:2002, EN 13445-4:2002 and EN 13445-5:2002, EN 764-1:2004 and EN 764-2:2002 and the following apply. Other symbols used in specific clauses of this European Standard are tabulated there. Symbol Description Unit A Area mm2 A elongation after fracture % d, D

Diameter mm e

Thickness mm f nominal design stress for design conditions MPa or N/mm2 ftest nominal design stress for testing conditions MPa or N/mm2 l Length mm p design pressure bar, MPa or N/mm2 1)

PS maximum allowable pressure bar, MPa or N/mm2 1) PT test pressure bar, MPa or N/mm2 1) r, R Radius mm Re yield strength MPa or N/mm2 ReH upper yield strength MPa or N/mm2

Rm tensile strength MPa or N/mm2 Rm/t tensile strength at temperature t °C MPa or N/mm2 Rp0,2/t 0,2 % proof strength at temperature t °C MPa or N/mm2 Rp1,0/t 1,0 % proof strength at temperature t °C MPa or N/mm2 TS temperature

°C tc calculation temperature °C tt test temperature °C V volume, capacity m3, L, (l) z

weld joint coefficient [ ]

The unit bar is needed to meet the general terminology, and thus to be used on nameplates, certificates, drawings, pressure gauges and instrumentation.

1) MPA or N/mm2 for calculation purpose only.

EN 13831:2007 (E) 10 5 Materials 5.1 General The grouping according to Table 5.1-1 is based on materials corresponding to steel groups 1; 1.1; 8.1 as

defined in EN 13445-2:2002. Table 1 — Definitions of steel groups (CEN ISO/TR 15608:2005) Group/ Subgroup Type of steel 1 Steels with a minimum yield strength ReH ≤ 460 N/mm2 a

and with analysis in % (ladle analysis):
C ≤ 0,25 Cu ≤ 0,40 b
Si ≤ 0,60 Ni ≤ 0,5 b
Mn ≤ 1,70 Cr ≤ 0,3 (0,4 for castings) b
Mo ≤ 0,70 Nb ≤ 0,05
S ≤ 0,045 V ≤ 0,12 b

P ≤ 0,045 Ti ≤ 0,05 1.1 Steels with a minimum yield strength ReH ≤ 275 N/mm2 and composition as indicated under 1 8.1 Austenitic stainless steels with Cr ≤ 19 % (content used in steel designation) a In accordance with the specification of the steel product standards, ReH may be replaced by Rp0,2 or Rt 0,5. b A higher value is accepted provided that Cr + Mo + Ni + Cu + V ≤ 0,75 %.

For a complete overview of steel grades falling into the above mentioned groups reference is made to

EN 13445-2:2002. 5.2 Materials proven by experience and current use The following materials do not fulfil all the requirements of groups 1, 1.1 and 8.1, but may be used for this type of product under the condition that there is sufficient ductility of the material after forming as it will be used is proven:  EN 10025-22)

grades S 235 J2, S 235 JR;  EN 101303)
grades Dc01, Dc03, Dc04;  EN 101113)
grades DD11, DD12, DD13, DD14.
2) See 6.3.2.5. 3) Restricted use, see 6.2.

EN 13831:2007 (E) 11 5.3 Fasteners Fasteners (bolts, nuts, studs) shall not be made from free cutting steel. Used steels shall have an elongation after fracture, A, of at least 14 %. Bolts and screws in accordance with EN ISO 898-1:1999 property classes 5.6 or 8.8 and nuts to

ISO 898-2:1998 property classes 5 or 8 but with an elongation of at least 12 %, shall be considered suitable. EN 10269:1999 shall be taken into account. 5.4 Non-pressurised parts For non-pressure parts welded to pressure vessels, materials shall be used which are supplied to material specifications covering at least the requirements for the chemical composition and the tensile properties. These materials shall not limit the operating conditions of the material to which they are attached. 6 Design and calculation 6.1 Design 6.1.1 Requirements pertaining to the diaphragm Sharp edges and corners (grooves, welding beads etc.) are not permitted in those areas of the inside surface which will come into contact with the diaphragm. Parts projecting into the vessel in such a way, that damage of the diaphragm can occur are not permitted. Local concavities on the inner surface are only permitted if the maximum possible linear stretching of the

diaphragm being pressed into the concavity is not above 10 % of the elongation at rupture of the diaphragm material. Openings in the vessel wall shall be designed in such a way that the diaphragm cannot be damaged through impingement. The gaps of joggled welds shall nowhere be bigger than twice the diaphragm wall-thickness. The dimensions of the vessel and the diaphragm shall match so as to ensure that irrespective of charge pressure the diaphragm cannot be stretched to the point where it is damaged. 6.1.2 Requir

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