Gas-loaded accumulators for fluid power applications

1.1 This European Standard specifies the requirements for materials, design, manufacture, testing inspection, safety systems and documentation (including instructions for first operation), for commonly-used types of gas-loaded accumulators and gas bottles for fluid power applications (see 1.2). 1.2 This European Standard applies to the following types of components, defined as the pressure-containing envelope of gas-loaded accumulators: - bladder type; - diaphragm type; - piston type; - transfer type; - gas bottles used to provide additional gas capacity. They consist of one or several parts joined together by a variety of mechanical means and by welding. 1.3 This European Standard applies to gas-loaded accumulators which operate with the following conditions: - subject to an internal gauge pressure greater than 0,5 bar; - working temperature of not lower than -50 °C and not higher than +200 °C; - containing Group 2 liquids and gases as defined in the Pressure Equipment Directive 97/23/EC. It does not apply to: - accumulators for use with dangerous fluids (see NOTE 1). NOTE 1 Fluid power applications utilize non-dangerous fluids as categorized in ISO 6743-4 in addition to an inert gas (e.g. nitrogen) which is used as the pre-charging medium. NOTE 2 There are no design limits to the volume of the accumulator.

Hydrospeicher für Hydraulikanwendungen

1.1   Diese Europäische Norm beschreibt die Anforderungen an Werkstoffe, Konstruktion, Herstellung, Prüfung, Sicherheitssysteme und Dokumentation (einschließlich Anleitungen für die erste Inbetriebnahme) für die allgemein gebräuchlichen Bauarten von Gasdruckspeichern und Druckbehältern für hydraulische Anwendungen (siehe 1.2).
1.2   Diese Europäische Norm gilt für folgende Bauteile, die als druckbeaufschlagte Gehäuse von Gasdruck-speichern definiert sind:
-   Blasenspeicher;
-   Membranspeicher;
-   Kolbenspeicher;
-   Transferspeicher;
-   Gasbehälter zur Vergrößerung des Gasvolumens.
-   Diese können aus einem oder mehreren Gehäuseteilen bestehen, die auf unterschiedliche Art und Weise miteinander verbunden sind, einschließlich Schweißverfahren.
1.3   Diese Europäische Norm gilt für Gasdruckspeicher, die unter folgenden Bedingungen arbeiten:
-   der Innendruck ist größer als 0,5 bar;
-   die Betriebstemperatur ist nicht niedriger als −50 °C und nicht höher als +200 °C;
-   sie werden mit Flüssigkeiten und Gasen betrieben, wie sie in der Druckgeräte-Richtlinie 2014/68/EU definiert sind.
ANMERKUNG   Wenn Druckspeicher mit Flüssigkeiten und Gasen der Gruppe 1 betrieben werden, sind Betrachtungen in Bezug auf Risiken, die von denen durch die Druckgeräte-Richtlinie 2014/68/EU abweichen, nicht von der vorliegenden Norm abgedeckt und müssen getrennt bewertet werden.

Accumulateurs hydropneumatiques pour transmissions hydrauliques

1.1   La présente Norme européenne spécifie les exigences relatives aux matériaux, à la conception, à la fabrication, aux contrôles, à la configuration des équipements de sécurité et à la documentation (y compris les instructions pour la première mise en service) applicables aux accumulateurs hydropneumatiques et récipients sous pression de types courants pour transmissions hydrauliques (voir 1.2).
1.2   La présente Norme européenne s’applique aux types de composants suivants, définis comme étant l’enveloppe sous pression des accumulateurs hydropneumatiques :
-   type à vessie ;
-   type à membrane ;
-   type à piston ;
-   type transfert ;
-   récipients sous pression utilisés en tant que capacités additionnelles.
Ils sont constitués d’une ou de plusieurs parties assemblées par différents moyens mécaniques et par soudage.
1.3   La présente Norme européenne s’applique aux accumulateurs hydropneumatiques fonctionnant dans les conditions suivantes :
-   soumis à une pression manométrique interne supérieure à 0,5 bar ;
-   la température de fonctionnement est comprise entre -50 °C et +200 °C ;
-   contenant des liquides et des gaz tels que définis dans la Directive 2014/68/UE relative aux équipements sous pression, voir la Note.
NOTE   Lorsque l’accumulateur contient des liquides ou des gaz du Groupe 1, les considérations relatives aux risques autres que celles requises par la Directive 2014/68/UE relative aux équipements sous pression ne sont pas couvertes par la présente Norme européenne et seront évaluées séparément.

Hidropnevmatski akumulatorji za hidravlične sisteme

1.1 Ta evropski standard določa zahteve za material, zasnovo, izdelavo, pregled preskušanja, varnostne sisteme in dokumentacijo (vključno z navodili za prvo delovanje) za pogosto uporabljene vrste hidropnevmatskih akumulatorjev in plinskih jeklenk za hidravlične sisteme (glej 1.2). 1.2 Ta evropski standard se uporablja za naslednje vrste komponent, opredeljene kot plašči pod tlakom v hidropnevmatskih akumulatorjih: – mehurske; – membranske; – batne; – transportne; – plinske jeklenke, ki zagotavljajo dodatno količino plina. Sestavljene so iz enega ali več delov, ki so med seboj povezani z različnimi mehanskimi sredstvi in z varjenjem. 1.3 Ta evropski standard se uporablja za hidropnevmatske akumulatorje, ki delujejo v naslednjih pogojih: – nanje deluje notranji podtlak, večji od 0,5 bara; – delovna temperatura ne sme biti nižja od –50 °C in višja od +200 °C; – vsebuje tekočine in pline skupine 2, kot določa direktiva 97/23/ES o tlačni opremi. Ne uporablja se za: – akumulatorje za uporabo z nevarnimi tekočinami (glej OPOMBA 1). OPOMBA 1: Hidravlični sistemi uporabljajo nenevarne tekočine, kot so kategorizirane v standardu ISO 6743-4, poleg inertnega plina (npr. dušika), ki se uporablja kot medij za predhodno polnjenje. OPOMBA 2: Ni nobenih konstrukcijskih omejitev glede prostornine akumulatorja.

General Information

Status
Published
Public Enquiry End Date
04-Dec-2014
Publication Date
06-Jun-2017
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
08-Mar-2017
Due Date
13-May-2017
Completion Date
07-Jun-2017

Relations

Buy Standard

Standard
SIST EN 14359:2017
English language
98 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 14359:2017
01-julij-2017
1DGRPHãþD
SIST EN 14359:2007+A1:2011
+LGURSQHYPDWVNLDNXPXODWRUML]DKLGUDYOLþQHVLVWHPH
Gas-loaded accumulators for fluid power applications
Hydrospeicher für Hydraulikanwendungen
Accumulateurs hydropneumatiques pour transmissions hydrauliques
Ta slovenski standard je istoveten z: EN 14359:2017
ICS:
23.100.99 'UXJLVHVWDYQLGHOL Other fluid power system
KLGUDYOLþQLKVLVWHPRY components
SIST EN 14359:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 14359:2017
---------------------- Page: 2 ----------------------
SIST EN 14359:2017
EN 14359
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2017
EUROPÄISCHE NORM
ICS 23.100.99 Supersedes EN 14359:2006+A1:2010
English Version
Gas-loaded accumulators for fluid power applications
Accumulateurs hydropneumatiques pour Hydrospeicher für Hydraulikanwendungen
transmissions hydrauliques
This European Standard was approved by CEN on 2 January 2017.

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, Serbia, 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

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14359:2017 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Contents Page

European foreword ...................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms, definitions, symbols and units .................................................................................................... 6

3.1 Terms and definitions ................................................................................................................................... 6

3.2 Symbols and units ........................................................................................................................................... 7

4 Materials ............................................................................................................................................................ 9

4.1 Requirements for metallic materials....................................................................................................... 9

4.2 Material certificates for components of the pressure containing envelope.............................. 9

5 Basic design and calculation criteria ..................................................................................................... 10

5.1 General.............................................................................................................................................................. 10

5.2 Corrosion ......................................................................................................................................................... 10

5.3 Qualification by similarity ......................................................................................................................... 10

5.4 Design methods ............................................................................................................................................. 10

5.5 Design and calculation methods common to all accumulator types .......................................... 13

5.6 Specific design criteria for piston accumulators ............................................................................... 23

5.7 Specific design criteria for diaphragm accumulators ...................................................................... 35

5.8 Specific design criteria for oil ports mainly used in bladder type accumulators .................. 43

6 Manufacture .................................................................................................................................................... 45

6.1 General.............................................................................................................................................................. 45

6.2 Special manufacturing processes for welded diaphragm accumulators .................................. 45

6.3 Forming of bladder accumulator shells ................................................................................................ 48

7 Inspection and testing ................................................................................................................................. 50

7.1 General.............................................................................................................................................................. 50

7.2 Design documentation ................................................................................................................................ 51

7.3 Design review and design verification .................................................................................................. 51

7.4 Inspection during manufacture ............................................................................................................... 51

7.5 Hydrostatic pressure test .......................................................................................................................... 52

7.6 Fatigue performance evaluation ............................................................................................................. 52

7.7 Marking and labelling ................................................................................................................................. 67

7.8 Documentation .............................................................................................................................................. 69

8 Safety instructions and equipment for accumulators ..................................................................... 69

8.1 Introduction .................................................................................................................................................... 69

8.2 Safety equipment .......................................................................................................................................... 70

8.3 Tests and examinations before first operation .................................................................................. 72

8.4 Supervision and maintenance .................................................................................................................. 73

Annex A (informative) Examples of safety equipment configuration ....................................................... 74

A.1 Example 1 ........................................................................................................................................................ 74

A.2 Example 2 ........................................................................................................................................................ 75

A.3 Example 3 ........................................................................................................................................................ 76

A.4 Example 4 ........................................................................................................................................................ 77

---------------------- Page: 4 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)

A.5 Example 5 ........................................................................................................................................................ 78

A.6 Example 6 ........................................................................................................................................................ 79

A.7 Example 7 ........................................................................................................................................................ 80

Annex B (informative) Manufacturer's declaration of conformity form ................................................. 81

Annex C (informative) Basics of statistics and probability analysis of fatigue test results .............. 82

C.1 General ............................................................................................................................................................. 82

C.2 Basics ................................................................................................................................................................ 82

Annex D (informative) Example of the application of the fatigue test method ..................................... 86

D.1 General ............................................................................................................................................................. 86

D.2 In-service range of pressure ..................................................................................................................... 86

D.3 Fatigue test conditions................................................................................................................................ 86

D.4 Fatigue test results: ...................................................................................................................................... 87

D.5 Statistical interpretation of data ............................................................................................................. 87

D.6 Estimation of the N-S curve (allowable number of cycles curve) ................................................ 88

D.7 Interpretation of the fatigue data results for qualification ........................................................... 89

D.8 Using the result for the qualification of a similar forged accumulator of 10 litre

capacity ............................................................................................................................................................ 89

Annex E (informative) Example of similarity analysis ................................................................................... 91

Annex F (informative) Preliminary choice of ∆P and extrapolation limits of S-N curve .............. 93

testi

F.1 Preliminary choice of ∆P ...................................................................................................................... 93

testi

F.2 Extrapolation limits of S-N curve ............................................................................................................ 95

Annex ZA (informative) Relationship between this European Standard and the Essential

Requirements of Directive 2014/68/EU aimed to be covered .................................................... 96

Bibliography ................................................................................................................................................................. 97

---------------------- Page: 5 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
European foreword

This document (EN 14359:2017) 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 October 2017 and conflicting national standards shall

be withdrawn at the latest by October 2017.

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 supersedes EN 14359:2006+A1:2010.

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.

In comparison with EN 14359:2006+A1:2010, the following modifications have been made:

— In general, references have been aligned to the new Pressure Equipment Directive 2014/68/EU;

— the Scope has been broadened so as not to specifically exclude accumulators containing Group 1

liquids or gases;

— 'Table 3 - Allowable design stress values for fine grained and heat treated steels' has been added;

— in subclause 7.6, Fatigue performance evaluation, the normative text has been refined;

— more information is provided in the informative Annexes C to F;

— in the Annexes: Conformity assessment modules and activities have been removed from this edition;

— informative Annexes B and ZA have been updated to take into account the new Pressure Equipment

Directive 2014/68/EU.

Where appropriate, formulae and techniques are consistent with the requirements of EN 13445-3 but

this European Standard is presumed to satisfy the essential requirements of the Pressure Equipment

Directive 2014/68/EU in its own right.

NOTE If any matter of interpretation or doubt arises as to the meaning or effect of any normative part of this

European Standard, or as to whether anything should be done or has been omitted to be done, in order that this

European Standard should be complied with in full, the matter needs to be referred to the CEN/TC 54 Committee.

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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

the United Kingdom.
---------------------- Page: 6 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
1 Scope

1.1 This European Standard specifies the requirements for materials, design, manufacture, testing

inspection, safety equipment configuration and documentation (including instructions for first

operation), for commonly-used types of gas-loaded accumulators and pressure vessels used to provide

additional gas capacity for fluid power applications (see 1.2).

1.2 This European Standard applies to the following types of components, defined as the pressure-

containing envelope of gas-loaded accumulators:
— bladder type;
— diaphragm type;
— piston type;
— transfer type;
— pressure vessels used to provide additional gas capacity.

They consist of one or several parts joined together by a variety of mechanical means and by welding.

1.3 This European Standard applies to gas-loaded accumulators which operate with the following

conditions:
— subject to an internal gauge pressure greater than 0,5 bar;
— working temperature not lower than –50 °C and not higher than +200 °C;

— containing all liquids and gases as defined in the Pressure Equipment Directive 2014/68/EU,

see Note.

NOTE When the accumulator contains Group 1 liquids or gases, consideration relating to risks other than

those required by Pressure Equipment Directive 2014/68/EU are not covered by this European Standard and will

be assessed separately.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

EN 10204, Metallic products - Types of inspection documents
EN 13018, Non-destructive testing - Visual testing - General principles
EN 13445-2, Unfired pressure vessels - Part 2: Materials
EN 13445-3:2014, Unfired pressure vessels - Part 3: Design
EN 13445-4, Unfired pressure vessels - Part 4: Fabrication

EN ISO 148-1, Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO 148-1)

---------------------- Page: 7 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)

EN ISO 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws

and studs with specified property classes - Coarse thread and fine pitch thread (ISO 898-1)

EN ISO 6506-1, Metallic materials - Brinell hardness test - Part 1: Test method (ISO 6506-1)

EN ISO 6506-2, Metallic materials - Brinell hardness test - Part 2: Verification and calibration of testing

machines (ISO 6506-2)

EN ISO 6506-3, Metallic materials - Brinell hardness test - Part 3: Calibration of reference blocks

(ISO 6506-3)

EN ISO 6892-1, Metallic materials - Tensile testing - Part 1: Method of test at room temperature

(ISO 6892-1)

EN ISO 15614-1, 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)

ISO 262, ISO general purpose metric screw threads - Selected sizes for screws, bolts and nuts

ISO 9110-1, Hydraulic fluid power - Measurement techniques - Part 1: General measurement principles

ISO 9110-2, Hydraulic fluid power - Measurement techniques - Part 2: Measurement of average steady-

state pressure in a closed conduit

ISO 10771-1, Hydraulic fluid power - Fatigue pressure testing of metal pressure-containing envelopes -

Part 1: Test method
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
gas-loaded accumulator

hydraulic accumulator with separator between liquid and gas where the liquid is pressurized using the

compressibility of an inert gas (for example nitrogen)
Note 1 to entry: The separator can be a bladder, a diaphragm or a piston.

Note 2 to entry: Gas-loaded accumulators have shells, which can consist of cylinders, dished ends and flat plates.

Openings are always isolated, located on the axis centre line and positioned at both ends of the accumulator. It is

assumed that such vessels are axis-symmetrical.
3.1.2
bladder accumulator

gas-loaded accumulator consisting of pressure-retaining shell, either spun-forged from seamless tube,

hammer-forged from hollow bar or of welded construction, in which the liquid and gas are separated by

a flexible bag or bladder normally retained at one end of the shell
---------------------- Page: 8 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
3.1.3
diaphragm accumulator

gas-loaded accumulator consisting of pressure-retaining shell assembly, in which the construction can

either be screwed or welded, with integral ports in which the liquid and gas are separated by a flexible

membrane normally retained at its largest diameter to the shell
3.1.4
piston accumulator

gas-loaded accumulator consisting of cylinder body and end cap assemblies in which the liquid and gas

are separated by a rigid sliding piston
3.1.5
transfer type accumulator

gas-loaded accumulator with a port for connecting additional gas capacity from one or more pressure

vessels (e.g. gas bottle)
3.1.6
pressure vessels – providing additional gas capacity

inter-connected pressure vessels consisting of body and, depending upon construction, port assemblies

used to provide additional gas capacity and communicating with the gas chamber of the accumulator by

means of a pipe connection
3.2 Symbols and units
For the purposes of this document, the following symbols and units apply.
Table 1 — Symbols, characteristics and units
Symbol Characteristics Unit
c Corrosion allowance mm
e Required thickness of the component mm
e Analysis thickness of the component mm
e Minimum possible fabrication thickness mm
min
Nominal thickness of the component, as specified on the manufacturing
e mm
detail drawings
Absolute value of the negative tolerance on the nominal thickness taken
δ mm
from the material standard of the component
δ Possible thinning during manufacturing process of the component mm
N Number of pressure cycles
Pre-charging pressure; the gas pressure in the accumulator when the

P hydraulic circuit is not under pressure (initial state) at a temperature of MPa

(20 ± 5) °C
P Minimum working pressure of the hydraulic circuit MPa
P Maximum working pressure of the hydraulic circuit MPa
---------------------- Page: 9 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Symbol Characteristics Unit
P /P Allowable pressure ratio below which the accumulator type can be used
2 0
P Set pressure of the safety accessory for the accumulator, if one is fitted MPa
P Maximum permissible pressure MPa
max
PS Maximum allowable pressure MPa
P Test pressure MPa
test
R Minimum upper yield strength MPa
R Minimum tensile strength MPa
R Minimum tensile strength at design temperature t °C MPa
m/t
R Minimum 0,2 % - proof strength MPa
p0,2
R Minimum 0,2 % - proof strength at design temperature t °C MPa
p0,2/t
R Minimum 1,0 % - proof strength MPa
p1,0
R Minimum 1,0 % - proof strength at design temperature t °C MPa
p1,0/t
Maximum operating temperature of the hydraulic fluid or of the
TS °C
max
environment, whichever is higher or equal
Minimum operating temperature of the hydraulic fluid or of the
TS °C
min
environment, whichever is lower or equal
V Internal volume of the gas chamber litre
V Gas volume at pressure P litre
0 0
Volumes occupied by the gas contained in the accumulator and the

V , V additional chambers, if any, at pressures P and P at their respective litre

1 2 1 2
temperatures
z Weld joint coefficient ─
The relationships between the defined thicknesses are shown in Figure 1.

MPa for calculation purposes only, otherwise the unit should be bar (1 MPa = 10 bar).

See EN 13445-3:2014.
The inter-relation of the various definitions of thickness is shown in Figure 1.
---------------------- Page: 10 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Key
c corrosion allowance
e required thickness
e analysis thickness (e = e -c)
a a min
e minimum possible fabrication thickness
min
en nominal thickness

δe absolute value of the negative tolerance taken from the material standard of the component

δ possible thinning during manufacturing process of the component
Figure 1 — Relationship of thickness definitions
4 Materials
4.1 Requirements for metallic materials

The pressure containing envelope of gas-loaded accumulators shall be constructed of either:

— harmonized materials used for the manufacture of unfired pressure vessels and meeting the

requirements of EN 13445-2;

— materials other than those specified in EN 13445-2 provided that they have been accepted by a

particular material appraisal;

— materials covered by European approval for materials in accordance with Article 15 of Pressure

Equipment Directive 2014/68/EU.
4.2 Material certificates for components of the pressure containing envelope

Components used in the manufacture of the pressure containing envelope of gas-loaded accumulators to

category II, III and IV according to Annex II of the Pressure Equipment Directive 2014/68/EU shall be

accompanied by an inspection document in accordance with EN 10204 type 3.1 (see Annex III of the

Pressure Equipment Directive 2014/68/EU). Such components shall include, but not be limited to, those

determined by the application of the calculation formulae within this standard.
---------------------- Page: 11 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
5 Basic design and calculation criteria
5.1 General

The requirements of Clause 5 shall apply when the materials and welds are not subject to localised

corrosion in the presence of either products which the gas-loaded accumulator is to contain, or the

environment in which it is located.
5.2 Corrosion

Where there is a risk of corrosion, a protection method and/or corrosion allowance shall be applied to

the affected surfaces of the accumulator.

Consideration must be given to the potential for corrosion due, both to the internal fluid and external

environment. This should be countered by methods including, but not limited to, choice of corrosion-

resistant materials or the use of linings or coatings.

Only completely impervious, sufficiently thick and chemically stable layers with an average life, not less

than that of the pressure vessel, shall be considered to be reliable protection against corrosion. When in

doubt, corrosion tests shall be undertaken.

If there is no contact between the corrosive agent and the vessel base material, then it is not necessary to

provide a corrosion allowance for wastage of the base material.
5.3 Qualification by similarity

Accumulators are often serially produced and it is possible to qualify a range of accumulators based

upon the design, calculation and testing of one model within the range provided that other accumulators

are similar. Two accumulators are similar provided that:
— they are made of the same material of the same form and origin;
— they are identical with the exception of length;

— the internal length of the cylindrical portion is not less than three times its external diameter.

If the length of the cylindrical portion is less than three times its external diameter, then a detailed stress

analysis shall be undertaken.
5.4 Design methods
5.4.1 General

This European Standard specifies methods for the design by formulae of accumulators or accumulator

components. Satisfactory application of such formulae alone shall be sufficient to demonstrate

conformity to this European Standard provided the accumulator will be subjected to less than 500

pressure cycles between P and P during its lifetime.
2 1

Where the accumulator will be subjected to more than 500 pressure cycles between P and P , the

2 1

manufacturer shall make an assessment for the effects of fatigue, either by analysis or test. This

assessment shall form part of the Technical File.

Clauses 17 and 18 of EN 13445-3:2014 shall be used as the basis for a fatigue analysis and 7.6 of this

European Standard shall be used as the method for conducting a fatigue cycling test.

Figure 2 shows the design process to be adopted.
---------------------- Page: 12 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Figure 2 — Design process
5.4.2 Basic symbols, units and description

Table 2 lists basic symbols and units. Further and modified notation is provided in the individual

sections.
---------------------- Page: 13 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Table 2 — Basic symbols and units
Symbol Characteristics Units
D Outside diameter of the shell mm
D Inside diameter of the shell mm
Required thickness of end to limit membrane stress in
e mm
central part of shell
Required thickness of knuckle to avoid axis-symmetric
e mm
yielding
f Nominal design stress at design temperature MPa
fa Nominal design stress at test temperature MPa
f a
Nominal design shear stress at design temperature MPa
shear
f Nominal design stress for testing conditions MPa
test
D Mean diameter of shell mm
Internal height of dished end measured from cylindrical
h mm
part
r Inside radius of curvature of a knuckle mm
R Inside spherical radius of central part of torispherical end mm

MPa for calculation purposes only, otherwise the unit should be bar (1 MPa = 10 bar).

5.4.3 Maximum allowable values for the nominal design stress for pressure bearing parts

This sub-clause specifies maximum allowable values for the nominal design stress for pressure parts

other than bolts and physical properties of steels.

Maximum values for the nominal design stress at operating temperatures are given in Table 3.

---------------------- Page: 14 ----------------------
SIST EN 14359:2017
EN 14359:2017 (E)
Table 3 — Maximum allowable values of the nominal design stress for
pressure parts other than bolts
Normal Under test conditions
Austenitic
R R
steels with
p1,0/t
p1,0/t
test
f =
f =
test
30 % < A ≤
1,05
1,5
35 %
Austenitic
RR p1,0/t m/t
   R 
pt1,0/ pt1,0/
mt/ test test
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.