EN 13831:2007

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

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

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.

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

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 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.

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.

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 Requirements pertaining to fresh water application Metal parts in contact with the water during normal operation of the vessel shall be of stainless steel, corrosion resistant or adequately protected against corrosion. 6.1.3 Outside finish The vessel and its outside parts shall be so finished as to avoid injury (e.g. from burs and sharp edges).
Vessels made of carbon steel shall be protected against ambient corrosion. 6.1.4 Inspection openings 6.1.4.1 Vessels with fixed diaphragms do not require openings. 6.1.4.2 Vessels with a removable diaphragm shall have an opening of sufficient size to exchange the
diaphragm. This opening serves also for inspection purposes.

V ≤
12 DN 12 (0,375 ")
12 < V ≤
25 DN 15 (0,5 ")
25 < V ≤
600 DN 20 (0,75 ")
600 < V ≤ 1 000 DN 25 (1 ") 1 000 < V ≤ 2 000 DN 32 (1,25 ") 2 000 < V DN 40 (1,5 ")
NOTE For vessels used in freshwater applications larger connections could be required, depending on the flow rate. 6.1.5.2 If the water connection is covered by any kind of sieve, its total free section shall be a least equal to the free section of the connection pipe as specified in 6.1.5.1. 6.1.6 Clenched joints In the case of clenched joints the experimental design method shall be used to determine minimum wall thickness. There is therefore no calculation method for them in the European Standard. Within the framework of a type approval, in deviation from 6.2.2, at least 6 vessels have to be tested according to 6.2.3 or 6.2.4. In the case of different vessel sizes within a family, a minimum of 2 vessels per vessel size have to be tested according to 6.2.3 or 6.2.4 if PS × V ≤ 1 000 bar × L. In the case of different vessel sizes within a family, a minimum of 1 vessel per vessel size has to be tested according to 6.2.3 or 6.2.4 if 1 000 bar × L < PS × V < 6 000 bar × L. Circumferential measurements have to be carried out in the cylindrical part of the vessel above and below the clenched joint. The maximum allowable permanent deformation shall not be higher than 1 % (see 6.2.3 and 6.2.4). NOTE Owing to the wide variety of versions and designs of this type of joint it is impossible to indicate further dimensions or physical properties. 6.1.7 Volume tolerance of vessels The actual volume of the vessel measured without the diaphragm, shall be a minimum of 95 % of the (nominal) volume declared by the manufacturer. 6.1.8 Fatigue Expansion vessels as covered by this European Standard are operated in such a way that no relevant fatigue load occurs.

EN 13445-3:2002. The same applies where the specification for the vessel stipulates conditions which lead to special loadings (e.g. earthquake loadings). 6.2 Experimental design method 6.2.1 General The design for adequate strength may be determined by the use of the experimental design method for vessels with a PS × V < 6 000 bar L. EN 10130, grades Dc01, Dc03 and Dc04 and EN 10111, grades DD11, DD12, DD13 and DD14 may only be used in accordance with 5.2 when the design is verified according to the experimental design method in this subclause. Since these are intended for deep drawing the mechanical values in their respective standards do not lend themselves to the calculation method of 6.3. The minimum wall thickness shall not be less than 0,8 mm at any point. 6.2.2 Preparations The experimental test is performed on that vessel size within a family which will give the least favourable results under pressure (normally the one with the biggest diameter). Vessels to be submitted to the test have to be identical to normal production with the exception that they shall not contain a complete diaphragm. If for production reasons the complete diaphragm has to be built into the vessel, holes shall be made into the diaphragm to ensure that there is water on both sides of the diaphragm, so that leaks will then be visible irrespective of their position relative to the diaphragm. If the vessel selected fails, two more vessels of the same size shall be submitted to the same test. The design is only acceptable if both vessels then pass the test. The water used for testing shall be at room temperature. The permanent deformation (elongation of shell) shall be measured along the shortest circumference of the vessel. A report of the test shall be drawn up giving all necessary information so as to validate the test results including material certificates for the main parts of the vessel. 6.2.3 Vessels with PS × V ≤ 1 000 bar × L
The vessels to be tested shall be completely filled with water, then pressurised up to 2 × PS (– 0 % + 5 %) and held at this pressure for 5 min. No leaks shall occur during this time. The permanent deformation shall not be higher than 1 %. 6.2.4 Vessels with 1 000 bar × L < PS × V < 6 000 bar × L
The vessels to be tested shall be completely filled with water, then pressurised up to 3 × PS (– 0 % + 5 %) and held at this pressure for 5 min. No leaks shall occur during this time. The permanent deformation shall not be higher than 1 %. 6.2.5 Vessel parts and components When the experimental design method is used for vessel parts and components that are pressurized, they shall be subjected to an experimental test of 3 × PS (– 0 % + 5 %) and held at this pressure for 5 min. No leaks shall occur during this time.

z = 1
NDT on every vessel;
z = 0,85
spot NDT;
z = 0,7
only visual examination. 6.3.2.6 Allowances 6.3.2.6.1 Allowance to compensate for plate thickness and manufacturing tolerances For ferritic steels, the thickness tolerance to be used in the calculation is the negative tolerance in the relevant
dimensional standard for the finished component. Where the manufacturing process entails reduction in thickness the minimum required wall thickness shall be stated on the drawing. 6.3.2.6.2 Corrosion allowance No allowance for corrosion is made in this European Standard. NOTE Water in normal heating systems is not considered corrosive. Vessels in drinking water systems need to have metal parts protected against corrosion (see 6.1.2). 6.3.3 Cylindrical and spherical shells under internal pressure 6.3.3.1 Specific symbols De outside diameter of the shell e required shell thickness 6.3.3.2 Cylindrical shells The required wall thickness e is given by pzfDpe+⋅⋅=2e (4) 6.3.3.3 Spherical shells The required wall thickness e is given by pzf Dpe+⋅⋅=4e (5) 6.3.4 Dished ends under internal pressure 6.3.4.1 General These design rules apply to dished ends of the torispherical, ellipsoidal and hemispherical type, not welded (i.e. made of one piece of sheet metal). 6.3.4.2 Specific symbols
β function of e/R and r/Di for torispherical ends given by Figure 2
e required thickness of the knuckle
De
outside diameter of end
Di inside diameter of end
hi inside height of ellipsoidal end
K = Di / (2 hi), shape factor for an ellipsoidal end
R inside spherical radius of central part of torispherical end
r inner knuckle radius
Figure 1 — Dished end 6.3.4.3 Hemispherical ends The required thickness of a hemispherical end is given by Equation (5). 6.3.4.4 Torispherical ends A torispherical end is made up of a spherical cap, a toroidal knuckle and a cylindrical shell, the three components having tangents where they meet. The following rules are limited to ends for which: a) r ≤ 0,2 Di b) r ≥ 0,06 Di c) r ≥ 2 e d) e ≤ 0,08 De e) e > 0,005 Di (if this condition is not fulfilled, e has to be checked additionally for plastic buckling. See EN 13445–3 f) R ≤ De

Figure 2 — Torispherical end design (factor β) 6.3.4.5 Ellipsoidal ends An ellipsoidal end is made on a truly ellipsoidal former. These rules apply only to ends for which 1,7 < K < 2,2. Ellipsoidal ends shall be designed as nominally equivalent torispherical ends with: r / Di = 0,5 / K – 0,08 and (8) R / Di =
0,44 · K + 0,02 (9) 6.3.4.6 Nozzles intruding into the knuckle region For calculation of nozzles intruding into the knuckle region see EN 13445-3.

stress loaded cross sectional area effective as compensation mm2 Afb Af of nozzle mm2 Afp Af of compensating plate mm2 Afr Af of reinforcing ring mm2 Afs Af of shell wall (main body) mm2 Ap pressure loaded area mm2 Aps Ap of shell (main body) mm2 Apb Ap of nozzle mm2 Apr Ap of reinforcing ring mm2 d diameter (or maximum width) of opening, or inside diameter of a nozzle mm de outside diameter mm deb de of nozzle mm dep de of compensating plate mm der de of reinforcing ring mm di inside diameter mm dib di of nozzle (d of set-in nozzle) mm dip di of compensating plate mm dir di of reinforcing ring mm De external diameter of cylindrical or spherical shell at the centre of an opening mm Di internal diameter of cylindrical or spherical shell at the centre of an opening mm eb required thickness of nozzle (or mean thickness within the length lbo or lbo) mm ea, b analysis thickness of nozzle useful for reinforcement mm ep required thickness of compensating plate mm

inside height of a dished end, excluding cylindrical skirt mm lb length of nozzle extending outside the shell mm lb' effective length of nozzle outside the shell, useful for reinforcement mm lbi length of nozzle extending inside the shell mm lbi' effective length of nozzle inside the shell, useful for reinforcement mm lbo maximum length of nozzle outside the shell, useful for reinforcement mm lbio maximum length of nozzle inside the shell, useful for reinforcement mm ls length of shell, from edge of opening or from external diameter of nozzle, to a shell discontinuity mm l's effective length of shell useful for opening reinforcement mm lp width of compensating plate mm l'p effective width of compensating plate useful for reinforcement mm lr width of reinforcing ring mm l'r effective width of reinforcing ring useful for reinforcement mm l'so maximum length of shell (main body) contributing to opening reinforcement, taken on the mean radius of curvature of the shell wall mm Lb centre-to-centre distance between two openings or nozzles taken on the mean radius of curvature of the shell (main body) wall mm p pressure MPa ris inside radius of curvature of the shell (main body) at the opening centre mm R inside radius of curvature of the spherical part of a torispherical end or inside radius of a hemispherical end mm w distance between edge of opening and shell discontinuity mm wmin minimum allowed value for w
mm
6.3.5.3 Limitations Shell reinforced openings without a nozzle and/or reinforcing plate as well as those reinforced exclusively by a reinforcing plate the ratio d / (2 × ris) shall not exceed 0,5. For openings in cylindrical shells reinforced by nozzles it shall not exceed 1. On dished ends openings, nozzles, co
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