SIST EN 50064:2019
(Main)High-voltage switchgear and controlgear - Gas-filled wrought aluminium and aluminium alloy enclosures
High-voltage switchgear and controlgear - Gas-filled wrought aluminium and aluminium alloy enclosures
This document applies to wrought aluminium and aluminium alloy enclosures and their welding. These enclosures are pressurized with dry air, inert gases, for example sulphur hexafluoride or nitrogen or a mixture of such gases, used in indoor and outdoor installations of high-voltage switchgear and controlgear with rated voltages above 1 kV, where the gas is used principally for its dielectric and/or arc-quenching properties with rated voltages.
- above 1 kV and up to and including 52 kV concerning gas-filled compartments with design pressure higher than 300 kPa relative pressure (gauge);
- above 52 kV concerning all gas-filled compartments.
The enclosures comprise parts of electrical equipment not necessarily limited to the following examples:
- circuit-breakers;
- switch-disconnectors;
- disconnectors;
- earthing switches;
- current transformers;
- voltage transformers;
- surge arrestors;
- busbars and connections;
- etc.
The scope also covers enclosures of pressurized components such as the centre chamber of live tank switchgear, gas-insulated current transformers, etc.
Hochspannungs-Schaltgeräte und Schaltanlagen - Gasgefüllte Kapselungen aus Aluminium und Aluminium-Knetlegierungen
Appareillage électrique haute tension - Enveloppes sous pression en aluminium corroyé et en alliage d’aluminium
Le présent document s’applique aux enveloppes en aluminium corroyé et en alliage d'aluminium et leur soudage. Ces enveloppes sont sous pression d'air sec et de gaz inertes, par exemple l'hexafluorure de soufre ou l'azote ou un mélange de tels gaz, utilisées dans les installations intérieures et extérieures d'appareillage à haute tension sous des tensions assignées supérieures à 1 kV. Le gaz est utilisé principalement pour ses propriétés diélectriques et/ou d'extinction de l'arc avec des tensions assignées.
- supérieures à 1 kV et inférieures ou égales à 52 kV, en ce qui concerne les compartiments à remplissage de gaz dont la pression de calcul est supérieure à une pression relative (manométrique) de 300 kPa;
- supérieures à 52 kV en ce qui concerne tous les compartiments à remplissage de gaz.
Exemples de parties d'équipements électriques contenues dans les enveloppes:
- disjoncteurs;
- interrupteurs-sectionneurs;
- sectionneurs;
- sectionneurs de terre;
- transformateurs de courant;
- transformateurs de tension;
- parafoudres;
- jeux de barres et barres de raccordement;
- etc.
Le domaine d'application couvre également les enveloppes de composants sous pression tels que le carter d'appareillage à mécanisme sous tension, les transformateurs de courant à isolation gazeuse, etc.
Visokonapetostne stikalne in krmilne naprave - S plinom polnjena ohišja iz gnetljivega aluminija in aluminijevih zlitin
Ta evropski standard se uporablja za ohišja iz varjenega gnetljivega aluminija in aluminijeve zlitine s suhim zrakom ter inertnimi plini pod tlakom, npr. žveplov heksafluorid ali dušik ali mešanica takih plinov, ki se uporabljajo v notranjih in zunanjih namestitvah visokonapetostnih stikalnih ter krmilnih naprav z nazivnimi napetostmi nad 1kV, pri čemer se plin uporablja predvsem zaradi njegovih dielektričnih lastnosti in/ali lastnosti gašenja obloka z nazivnimi napetostmi:
– nad 1 kV in do vključno 52 kV ter s plinskimi razdelki s predvidenim tlakom, višjim od 300 kPa relativnega tlaka (merilnik);
– in z nazivno napetostjo nad 52 kV.
Ohišja zajemajo dele električne opreme, ki niso nujno omejeni na naslednje primere delov:
– odklopniki,
– stikala/ločilna stikala,
– ločilniki,
– ozemljitvena stikala,
– tokovni transformatorji,
– napetostni transformatorji,
– prenapetostni odvodniki,
– zbiralke in priključki,
– drugi deli.
Področje uporabe zajema tudi ohišja s komponentami pod tlakom, kot so sredinska komora stikalne komore pod napetostjo, plinsko izolirani tokovni transformatorji itd.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-2019
1DGRPHãþD
SIST EN 50064:1998
SIST EN 50064:1998/A1:1998
Visokonapetostne stikalne in krmilne naprave - S plinom polnjena ohišja iz
gnetljivega aluminija in aluminijevih zlitin
High-voltage switchgear and controlgear - Gas-filled wrought aluminium and aluminium
alloy enclosures
Hochspannungs-Schaltgeräte und Schaltanlagen - Gasgefüllte Kapselungen aus
Aluminium und Aluminium-Knetlegierungen
Appareillage électrique haute tension - Enveloppes sous pression en aluminium corroyé
et en alliage d’aluminium
Ta slovenski standard je istoveten z: EN 50064:2018
ICS:
29.130.10 Visokonapetostne stikalne in High voltage switchgear and
krmilne naprave controlgear
77.150.10 Aluminijski izdelki Aluminium products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN 50064
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2018
ICS 29.130.10 Supersedes EN 50064:1989
English Version
High-voltage switchgear and controlgear - Gas-filled wrought
aluminium and aluminium alloy enclosures
Appareillage électrique haute tension - Enveloppes sous Hochspannungs-Schaltgeräte und Schaltanlagen -
pression en aluminium corroyé et en alliage d'aluminium Gasgefüllte Kapselungen aus Aluminium und Aluminium-
Knetlegierungen
This European Standard was approved by CENELEC on 2018-08-27. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50064:2018 E
Contents Page
European foreword .4
Introduction .5
1 Scope .6
2 Normative references .6
3 Terms and definitions .7
4 Quality assurance .9
5 Normal and special service conditions .9
6 Materials . 10
6.1 Selection of material. 10
6.2 Chemical analysis. 11
7 Design . 11
7.1 General . 11
7.2 Calculation methods . 12
7.2.1 General . 12
7.2.2 Evaluation of mechanical strength using “Design by Formula” . 12
7.2.3 Evaluation of mechanical strength using “Design by Analysis” . 13
7.2.4 Evaluation of mechanical strength using “Design by Burst test” . 14
7.2.5 Flanges . 15
7.2.6 Bolted connections . 15
7.3 Inspection and access openings . 16
8 Manufacture and workmanship . 16
8.1 Material identification . 16
8.2 Order of completion of weld seams . 16
8.3 Cutting of materials . 16
8.3.1 General . 16
8.3.2 Cold sharing . 16
8.3.3 Thermal cutting . 17
8.3.4 Examination of cut edges . 17
8.4 Forming of shell sections and end plates . 17
8.5 Assembly tolerances . 17
8.6 Welded joints . 17
8.7 Assembly for welding. 17
8.8 General welding requirements . 17
8.9 Preheating . 18
8.10 Surface finish . 18
9 Repair of welding defects . 18
10 Inspection, testing and certification . 19
10.1 Type tests . 19
10.1.1 General . 19
10.1.2 Burst test procedure . 19
10.1.3 Strain measurement test . 19
10.2 Inspection and routine tests . 19
10.2.1 General . 19
10.2.2 Routine pressure tests . 20
10.3 Welding procedure specifications . 20
10.4 Welder performance tests . 20
10.5 Non-destructive testing . 20
10.5.1 Amount of testing of welded joints . 20
10.5.2 Test methods for weld seams . 21
10.5.3 Surface conditions and preparations for testing . 21
10.5.4 Marking of the enclosure welds . 22
10.5.5 Reporting . 22
10.5.6 Minimum acceptance levels . 22
10.5.7 Assessment of imperfections . 22
10.6 Design specification, drawings and data sheets . 24
10.7 Certificate . 24
10.8 Stamping . 24
10.9 Final inspection . 24
11 Pressure relief devices . 25
11.1 General . 25
11.2 Bursting discs . 25
11.3 Self-closing pressure relief valves . 25
11.4 Non-self-closing pressure relief devices . 25
Annex A (informative) A-deviation . 27
Bibliography . 28
European foreword
This document (EN 50064:2018) has been prepared by CLC/TC 17AC, “High-voltage switchgear and
controlgear”.
The following dates are fixed:
• latest date by which this document has (dop) 2019-08-27
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-08-27
standards conflicting with this document
have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 50064:1989.
This European Standard has been revised by CENELEC Technical Committee 17AC High-voltage
switchgear and controlgear. It supplements the relevant product standards on gas-insulated switchgear and
controlgear in that it provides specific requirements for pressurized high-voltage switchgear and controlgear.
The present EN has been written to get a European specification for the design, construction, testing,
inspection and certification of pressurized enclosures used in high-voltage switchgear and controlgear.
In this respect this European Standard constitutes the exclusion of HV switchgear from the scope of the
Directive 2014/68/EU (superseding 97/23/EC) concerning pressure equipment. Article 1, 2. (l) excludes
“enclosures for high-voltage electrical equipment such as switchgear, controlgear, transformers, and rotating
machines” from the scope of the Directive.
This standard deals with gas-insulated switchgear enclosures of wrought aluminium and aluminium alloy and
their welding. For different enclosure materials, other European Standards are available.
Introduction
This standard covers the requirements for the design, construction, testing, inspection and certification of
gas-filled enclosures for use specifically in high-voltage switchgear and controlgear, or for associated gas-
filled equipment.
Special consideration is given to these enclosures for the following reasons.
(a) The enclosures usually form the containment of electrical equipment, thus their shape is determined by
electrical rather than mechanical requirements.
(b) The enclosures are installed in restricted access areas and the equipment is operated by instructed,
authorized persons only.
(c) As the thorough drying of the inert, non-corrosive gas-filling medium is fundamental to the satisfactory
operation of the electrical equipment, the gas is periodically checked. For this reason, no internal corrosion
allowance is required on the wall thickness of these enclosures.
(d) The enclosures are subjected to only small fluctuations of pressure as the gas-filling density will be
maintained within close limits to ensure satisfactory insulating and arc-quenching properties. Therefore, the
enclosures are not liable to fatigue due to pressure cycling.
(e) The operating pressure is relatively low.
Due to the foregoing reasons and to ensure maximum service continuity as well as to reduce the risk of
moisture and dust entering the enclosures which may endanger safe electrical operation of the switchgear,
no pressure tests should be carried out after installation and before placing in service and no periodic
inspection of the enclosure interiors or pressure tests should be carried out after the equipment is placed in
service.
1 Scope
This document applies to wrought aluminium and aluminium alloy enclosures and their welding. These
enclosures are pressurized with dry air, inert gases, for example sulphur hexafluoride or nitrogen or a
mixture of such gases, used in indoor and outdoor installations of high-voltage switchgear and controlgear
with rated voltages above 1 kV, where the gas is used principally for its dielectric and/or arc-quenching
properties with rated voltages.
— above 1 kV and up to and including 52 kV concerning gas-filled compartments with design pressure
higher than 300 kPa relative pressure (gauge);
— above 52 kV concerning all gas-filled compartments.
The enclosures comprise parts of electrical equipment not necessarily limited to the following examples:
— circuit-breakers;
— switch-disconnectors;
— disconnectors;
— earthing switches;
— current transformers;
— voltage transformers;
— surge arrestors;
— busbars and connections;
— etc.
The scope also covers enclosures of pressurized components such as the centre chamber of live tank
switchgear, gas-insulated current transformers, etc.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 13445-3, Unfired pressure vessels — Part 3: Design
EN 13445-8:2014, Unfired pressure vessels — Part 8: Additional requirements for pressure vessels of
aluminium and aluminium alloys
EN 62271-1:2017, High-voltage switchgear and controlgear — Part 1: Common specifications for alternating
current switchgear and controlgear (IEC 62271-1:2017)
EN ISO 3452 (all parts), Non-destructive testing — Penetrant testing (ISO 3452)
EN ISO 898 (all parts), Mechanical properties of fasteners made of carbon steel and alloy steel (ISO 898)
EN ISO 9606-2, Qualification test of welders — Fusion welding — Part 2: Aluminium and aluminium alloys
(ISO 9606-2)
EN ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel (ISO 9712)
EN ISO 15614-2, Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 2: Arc welding of aluminium and its alloys (ISO 15614-2)
EN ISO 17636 (all parts), Non-destructive testing of welds — Radiographic testing (ISO 17636)
EN ISO 17640, Non-destructive testing of welds — Ultrasonic testing — Techniques, testing levels, and
assessment (ISO 17640)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
enclosure
part of gas-insulated metal-enclosed switchgear retaining the insulating gas under the prescribed conditions
necessary to maintain safely the rated insulation level, protecting the equipment against external influences
and providing a high degree of protection to personnel
3.2
manufacturer
organization that is responsible for the design of the enclosure and the production of the gas-insulated
switchgear
Note 1 to entry: In this standard, this is the switchgear manufacturer.
3.3
design pressure
pressure, expressed in relative terms (gauge), used to determine the thickness of the enclosure
Note 1 to entry: It is at least equal to the maximum pressure in the enclosure at the highest temperature that the gas
used for insulation can reach under specified maximum service conditions.
3.4
design temperature (of an enclosure)
maximum temperature that the enclosures can reach under specified maximum service conditions
Note 1 to entry: This is generally the upper limit of ambient air temperature increased by the temperature rise due to
the flow of rated normal current.
Note 2 to entry: Solar radiation should be taken into account when it has a significant effect on the temperature of the
gas and on the mechanical properties of materials. Similarly, the effects of low temperatures on the properties of some
materials should be considered.
[SOURCE: EN 62271-203:2012, 3.112, modified – Note 1 to entry and Note 2 to entry have been added]
3.5
design stress
maximum permissible stress on the enclosure imposed by conditions of operation, environment or test that
determine the (material) characteristics of an enclosure
3.6
normal load
load whose occurrence and level can be planned or predicted
3.7
exceptional load
load whose probability of occurrence during the lifetime of product is very small or accidental
3.8
alloy
substance having metallic properties and composed of two or more elements so combined that they cannot
readily be separated by physical means
[SOURCE: EN 12258-1:2012, 2.2.1]
3.9
aluminium alloy
metallic substance in which aluminium predominates by mass and the other elements exceed 1% of the total
content by weight
3.10
weld defect
imperfections in metallic fusion welds
3.10.1
lack of fusion
lack of union between the weld metal and the parent material or between the successive layers of weld metal
[SOURCE: EN ISO 6520-1:2007, Reference No. 401]
3.10.2
overlap
excessive weld metal covering the parent material surface but not fused to it
[SOURCE: EN ISO 6520-1:2007, Reference No. 506]
3.10.3
undercut
irregular groove at a toe of a run in the parent material or in previously deposited weld metal
[SOURCE: EN ISO 6520-1:2007, Reference No. 5011]
3.10.4
hot crack (hot tear)
crack formed in a cast metal or in a welding because of internal stress developed upon cooling at the solidus
temperature or slightly above
[SOURCE: EN 12258-1:2012, 5.2.8]
3.10.5
inclusion
extraneous material accidentally entrapped into the liquid metal during melting or melt treatment or
entrapped into the metal surface during hot or cold working
[SOURCE: EN 12258-1:2012, 5.5.7]
3.10.6
blister
raised spot whose inside is hollow, that forms on the surface of products and is caused by the penetration of
a gas into a subsurface zone typically during thermal treatment
[SOURCE: EN 12258-1:2012, 5.5.10]
Note 1 to entry: A void resulting from blister that has ruptured is often termed “blow hole”.
3.11
thermal treatment
heating, holding at elevated temperature and cooling of the solid metal in such a way as to obtain desired
metallurgical structure or properties
[SOURCE: EN 12258-1:2012, 3.6.1]
Note 1 to entry: The term “heat treatment” is used for the same concept as a synonym.
3.12
ductility
ability of a material to deform plastically before fracturing
[SOURCE: EN 12258-1:2012, 4.3.15]
3.13
fatigue
tendency for a metal to break under conditions of repeated cyclic stressing considerably below the tensile
strength
[SOURCE: EN 12258-1:2012, 4.3.23, modified – Note 1 to entry has been removed]
3.14
tensile strength
ratio of maximum load before rupture in a tensile test to original cross-sectional area
[SOURCE: EN 12258-1:2012, 4.3.3]
3.15
yield strength
stress necessary to produce a defined small plastic deformation in a material under uniaxial tensile or
compressive load
[SOURCE: EN 12258-1:2012, 4.3.4, modified]
3.16
test piece
two or more parts of material welded together in accordance with a specified weld procedure, in order to
make one or more test specimens
3.17
test specimen
portion detached from a test piece, in specified dimensions, finally prepared as required for testing
4 Quality assurance
It is the intention of this standard that the switchgear manufacturer shall be responsible for achieving and
maintaining a consistent and adequate quality of the product.
Sufficient examinations shall be made by the enclosure manufacturer to ensure that the materials,
production and testing comply in all respects with the requirements of this standard.
Inspection by the user`s inspectors shall not absolve the switchgear manufacturer from his responsibility to
exercise such quality assurance procedures as to ensure that the requirements and the intent of this
standard are satisfied.
5 Normal and special service conditions
Clause 2 of EN 62271-1:2017 is applicable.
6 Materials
6.1 Selection of material
Any aluminium or aluminium alloy is permissible. A list of recommended materials is given in Table 1 based
on information from EN 13445-8:2014.
The elongation after fraction of any aluminium or aluminium alloy shall comply with EN 13445-8:2014, 5.2.
NOTE Contact with more noble metals, particularly copper and its alloys, can lead to heavy galvanic corrosion.
Austenitic stainless steel is an exception to this rule because of its protective oxide film and can often be used in contact
with aluminium.
Aluminium enclosures should be protected externally where, for example, they come into contact with mild
steel supports.
Bitumen, thin zinc sheet (which gives sacrificial protection) or a combination of these are useful in this
respect. Alternatively, the mild steel supports can be galvanized or zinc or aluminium sprayed.
It should be noted that contact with certain gasket materials can cause corrosion of aluminium. The gasket
manufacturer should be consulted.
Table 1 — List of recommended aluminium alloys [1]
Group Sub Type of aluminium Designation
and
Group
EN AW number Chemical symbol Temper
aluminium alloys
22 Non heat treatable alloys
22.1 Aluminium-manganese EN AW — 3003 EN AW-Al Mn1Cu O, H111,
alloys H112
EN AW — 3103 EN AW-Al Mn1
O, H111,
EN AW — 3105 EN AW-Al Mn0,5Mg0,5
H112
O, H111
22.2 Aluminium-magnesium EN AW — 5005 EN AW-Al Mg1(B) O, H111,
alloys with Mg ≤ 1,5 % H112
EN AW — 5005A EN AW-Al Mg1(C)
O, H111,
EN AW — 5050 EN AW-Al Mg1,5(C)
H112
O, H111
22.3 Aluminium-magnesium EN AW — 5049 EN AW-Al Mg2Mn0,8 O, H111,
alloys with H112
EN AW — 5052 EN AW-Al Mg2,5
1,5 % < Mg ≤ 3,5 %
O, H111,
EN AW — 5154A EN AW-Al Mg3,5(A)
H112
EN AW — 5251 EN AW-Al Mg2
O, H111,
EN AW — 5454 EN AW-Al Mg3Mn(A)
H112
EN AW — 5754 EN AW-Al Mg3
O, H111,
H112
O, H111,
H112
O, H111,
H112
22.4 Aluminium-magnesium EN AW — 5083 EN AW-Al Mg4,5Mn0,7 O, H111,
alloys with Mg > 3,5 % H112
EN AW — 5086 EN AW-Al Mg4
O, H111
23 Heat treatable alloys
a
23.1 Aluminium-magnesium- EN AW — 6060 EN AW-Al MgSi T4
b c
silicon
EN AW — 6061 EN AW-Al Mg1SiCu T4 , T6
b c
alloys
EN AW — 6082 EN AW-Al Si1MgMn T4 , T6
a
For profiles only.
b
For seamless pipes and flanges only.
c
For flanges only.
These alloys are recommended because of their low content of copper and zinc (lower than 0,5 % each) as
well as their low content of magnesium (lower than 0,7 %).
Alloys listed in this table are similar but not identical regarding chemical composition and mechanical
properties. They are not interchangeable without a re-qualification of the enclosure, i.e. re-calculation or re-
testing.
The properties of the materials should be taken from the applicable standards.
For applications where specified temperatures exceed 100 °C heat treated materials are not permitted due to
the loss of material properties, i.e. the thermal treatment will be nullified.
6.2 Chemical analysis
The chemical composition shall be in accordance with their material specification materials except that all
materials shall have a maximum lead content of 150 pg/g.
It is recommended that the material to be used for welded components be produced from rolling or extrusion
ingots with hydrogen level no greater than 0,2 ml per 100 g aluminium, measured on liquid metal during
casting.
Ingots used shall comply with the requirements of the appropriate material specification and any special
requirement called for on the order; they shall be clean and free from harmful defects.
Providing the chemical analysis of the melt meets the requirements of the appropriate specification, the
founder may use scrap which arises from his own production from approved ingots, which is segregated and
identifiable. It may include heavy fettling scrap, but shall exclude all drosses and small particles such as
sawings and chippings.
NOTE Attention is drawn to a limitation of the range of aluminium-magnesium alloys. Alloys with magnesium
content above 4 % can become susceptible to stress-corrosion cracking after use for long periods at temperatures above
100 °C.
7 Design
7.1 General
The rules for the design of enclosures of gas-insulated switchgear and controlgear prescribed in this clause
take into account that these enclosures are subjected to particular operating conditions (refer to Introduction)
which distinguish them from compressed air receivers and similar storage vessels. Examples of such
enclosures are listed in Clause 1.
As part of the validation process of the enclosure the mechanical strength of an enclosure shall be proven by
a type test according to subclause 10.1.
An enclosure can be designed by two alternative methods:
— Design by Formula (DbF)
— Design by Analysis (DbA)
The geometry of an enclosure is determined by electrical rather than mechanical considerations. Moreover,
constraints in shape can be enforced by the casting process used. These constraints can result in an
enclosure geometry which cannot be calculated by DbF. In such cases, DbA shall be applied.
When designing an enclosure, account shall be taken of the following, if applicable:
a) the evacuation of the enclosure as part of the filling process;
b) the full differential pressure across the enclosure wall or partition;
c) superimposed loads and vibrations by external effects, e.g. as they are caused by thermal or seismic
effects.
The enclosures are filled in service with a non-corrosive thoroughly dried gas. Therefore, no internal
corrosion allowance is necessary.
7.2 Calculation methods
7.2.1 General
This part provides calculation rules, design stresses and boundary conditions for the design of enclosures. In
7.2.5 and 7.2.6 boundary conditions for the design of flanges and bolts are given. For the design of the
wrought aluminium enclosure itself three methods may be used to proof appropriate design stress (Table 2):
the preferred method, Design by Formula is given in 7.2.2. The alternative methods, Design by Analysis or
Design by Burst test are given in 7.2.3 and 7.2.4.
Table 2 — List of design methods
1 Design by Formula preferred 7.2.2
2 Design by Analysis 7.2.3
3 Design by Burst test 7.2.4
7.2.2 Evaluation of mechanical strength using “Design by Formula”
When the wall and flange thicknesses of the enclosure are calculated, the formulas from established
specifications such as the following codes shall be taken, using the design pressure, the design temperature
as defined in 3.4 and 3.5 and the safety factor as defined in this subclause:
EN 13445–3
AD 2000 Regelwerk [2]
ASME Code [3]
CODAP [4]
Raccolta VSR [5]
SVTI [6]
The formulae in the specifications are equivalent to each other; the choice is left to the manufacturer.
The design stress (f ) at the design pressure including the safety factor of the appropriate formulae is given
d
by:
R
e
f ⋅ν
d
1,5
where
Re is minimum yield strength of the material at the design temperature taken from the material standard for
the chosen alloy;
1,5 is safety factor;
ν is welding factor to be taken as 0,75 or 1 depending of the situation.
Selection of the welding factor according to 10.5.1.
=
7.2.3 Evaluation of mechanical strength using “Design by Analysis”
7.2.3.1 Normal loads
f
The design stress ( ) for normal loads is given by:
dn_
R
e
f ⋅ν
dn_
S
n
where
is maximum permissible design stress for normal loads;
f
dn_
R is minimum yield strength of the material at the design temperature taken from the material
e
standard for the chosen alloy;
S is safety factor for normal loads S = 1,05;
n n
ν is welding factor to be taken as 0,75 or 1 depending of the situation.
Selection of the welding factor according to 10.5.1.
Examples for normal loads include:
— gas pressure;
— temperature (ambient, current);
— dead load;
— erection load (transportation and handling on site);
— ice and/or wind;
— tension loads (cable, overhead lines).
Combinations of different loads shall reflect the operating conditions on site. Load combinations do not
change the overall safety factor.
7.2.3.2 Exceptional loads
f ) for exceptional loads is given by:
The design stress (
d _ e
R
m
f ⋅ν
d _ e
S
e
where
is maximum permissible design stress for exceptional loads;
f
d _ e
R is minimum tensile strength of the material at the design temperature taken from the material
m
standard for the chosen alloy;
S is safety factor for exceptional loads S = 1,05;
e e
ν is welding factor to be taken as 1.
=
=
Examples for exceptional loads include:
— earthquakes;
— extreme wind and/or ice;
— short-circuit tensile loads (overhead lines, cable).
Combinations of different loads shall reflect the operating conditions on site. Load combinations do not
change the overall safety factor.
7.2.4 Evaluation of mechanical strength using “Design by Burst test”
7.2.4.1 General
When the thickness of the pressure parts are not calculated or where doubt exists regarding the accuracy of
the calculations, a proof test shall be carried out with one enclosure of a particular design. One of the
following proof tests is applicable:
a) Burst test
b) Strain measurement test
When proof tests are carried out on enclosures which are subjected to significant static superimposed loads
in service, the effect of these loads shall be simulated during the tests.
The proof test may be used for the purpose of establishing the design pressure of enclosures or enclosure
parts only when the wall thickness is not determined by means of the design rules given in this standard. The
design pressure of all other parts shall be determined by means of the applicable design rules.
7.2.4.2 Burst test procedure
This procedure is to be used for enclosures or enclosure parts under internal pressure. The design pressure
of any part of the enclosure tested by this method shall be established by a pressure test.
The design pressure (p) for which an enclosure meets the requirements of this standard shall be calculated
according to:
p σ
R a
pv ⋅⋅
2,3 σ
t
where
p is design pressure;
pR is burst pressure;
ν is welding factor (refer to 10.5.1);
σa is permissible design stress at design temperature;
σ is permissible design stress at test temperature;
t
2,3 is safety factor against bursting strength.
7.2.4.3 Strain measurement test procedure
Before the test commences or any pressure has been applied to the enclosure, strain gauges of electrical
resistance or other types shall be affixed to both the inside and the outside surfaces of the enclosure. The
type and number of gauges, their positions and their directions shall be chosen so that principle strains and
stresses can be determined at all points of importance to the integrity of the enclosure. The type of gauge
and the cementing technique shall be chosen so that strains up to 1 % can be determined.
=
The pressure shall be applied gradually in steps of approximately 20 % of the expected design pressure and
shall be unloaded after each step. Strain readings shall be taken during the loading and unloading cycle.
An indication of localized permanent set may be disregarded provided there is no evidence of a general
distortion of the enclosure.
A long as the permanent strain does not exceed 0,2 %, the pressure shall be increased up to 1,1 · 1,3 times
the expected design pressure which shall be then be considered as being confirmed.
If the permanent strain exceeds 0,2 % during an earlier step, the pressure may be re-applied at a lower
value not more than five times to determine the pressure (p ) related to a permanent strain of less than
y
0,2 %. In this case the design pressure (p) shall be calculated according to:
1 σ
a
pp ⋅ ⋅
y
1,1 ⋅1,3 σ
t
where
py pressure at which the intersection of the strain curve with the 0,2 % off-set to the
linear portion of the curve occurs;
1,3 routine test pressure factor;
1,1 strain measurement factor.
7.2.5 Flanges
The design of flange connections (refer to Figure 1, flange A or B) shall be based on the following:
— The number of bolts shall be chosen to ensure a plane support surface.
— The distance a between bolt and gasket shall be as small as technically feasible.
— The radius R between the flange and the cylindrical neck shall be as large as technically feasible.
If flange connections successfully passed the bursting test of the enclosure, no calculation of the permissible
design stresses for the flanges is necessary.
7.2.6 Bolted connections
7.2.6.1 General
The mechanical properties of the nuts and bolts are in accordance with the EN ISO 898 series. The material
strength of bolts should not exceed a ratio of
R
e
= 0,8
R
m
where
Rm minimum tensile strength;
R minimum yield strength.
e
Where the design requires the use of bolts with high tensile strength, they shall be appropriately marked.
If bolted connections successfully passed the bursting test of the enclosure, no calculation of the strength of
bolts is necessary.
=
7.2.6.2 Normal loads
f
The maximum permissible design stress ( ) for bolted connections at normal loads should not exceed a
d
ratio of
R
e
f ≤
d
2,5
or
R
m
f ≤
d
7.2.6.3 Exceptional loads
f
The maximum permissible design stress ( ) for bolted connections at exceptional loads, also applicable for
d
loads applied during routine tests, should not exceed a ratio of
R
e
f ≤
d
1,5
or
R
m
f ≤
d
7.3 Inspection and access openings
No access or inspection openings are necessary for inspection of the enclosure.
8 Manufacture and workmanship
8.1 Material identification
The manufacturer shall keep on file a documented system of identification for the materials (parent metals
and consumables) used in fabrication.
8.2 Order of completion of weld seams
Where any enclosure is made in two or more courses, the longitudinal seams shall be completed before
commencing the joining of the circumferential seam(s). Where practicable the longitudinal seams of adjacent
courses shall be staggered.
8.3 Cutting of materials
8.3.1 General
All materials shall be cut to size and shape by mechanical or thermal cutting, e.g. cold shearing, plasma-arc
cutting, machining or chipping, etc.
8.3.2 Cold sharing
Plates less than 12 mm thick need not be dressed. For plates greater than 12 mm and less than 25 mm
thick, however, cold shearing may also be used provided that the cut edges are dressed back mechanically
by not less than 1,5 mm to produce a suitable surface for the examination prior of welding.
8.3.3 Thermal cutting
Surfaces which have been thermal cut e.g. plasma-arc cut or laser cut, shall be dressed back by machining
to remove severe notches and scale in order to produce a suitable surface for the examination prior to
welding.
8.3.4 Examination of cut edges
Before carrying out further work cut surfaces and heat affected zones shall be examined for imperfections
including laminations cracks and solid and other inclusions.
Visual methods may be supplemented by dye penetrant examination.
Any material affected in the process of cutting to size and the preparation of welding edges shall be removed
by machining or chipping back to unaffected metal.
8.4 Forming of shell sections and end plates
Prior to forming, a visual examination of all plates shall be carried out and the thickness shall be checked.
Plates shall be formed to the required shape by any process that does not impair the quality of the material.
An effective thermal treatment may be applied following the forming operation to restore the mechanical
properties to their specified values.
As far as practicable all hot and cold forming operation shall be done by machine, uncontrolled local heating
shall not, hammering should not be used.
Lubricant remaining after the forming operation shall be removed by a suitable chemical cleaning process,
that will not impair the quality of the material.
Plates may be butt welded together prior to forming. Any joint in the formed area shall be non-destructively
tested after forming.
If the inside radius of curvatures of a pressure part is less than 10 times the thickness, an appropriate
thermal treatment to reduce the effects of cold work may be applied.
Shell plates shall be formed to the correct contour up to the extreme edges of the plate. Shells shall be
formed from the minimum number of plates which is practicable, and checked for the wall thickness after
forming.
8.5 Assembly tolerances
Tolerancing principles shall be consistent with the standard mentioned in 7.2.2 used for the design.
8.6 Welded joints
Weld joints shall be consistent with the standard mentioned in 7.2.2 used for the design.
8.7 Assembly for welding
Joints shall be fitted, aligned and held so that the correct gap is maintained during welding and the stated
tolerances shall not be exceeded in the finished joint.
The root faces shall be aligned within the tolerances stipulated by the approved welding procedure
specification.
Tack welds may be used and incorporated into the final weld provided they are sound and have been made
according to an approved welding procedure.
8.8 General welding requirements
In general, MIG and TIG-welding techniques shall be used or other specialized processes, e.g. electron
beam welding, laser beam welding as well as plasma-arc welding may also be used.
Friction stir welding according to EN ISO 25239 is also permissible.
AII fusion faces shall be thoroughly cleaned of oxide, oil or other foreign substances to give a clean metal
surface. Such cleaning shall be extended for a distance of at least 6 mm from the edge of each fusion face in
the case of oxide and at least 12 mm in the case of oil or grease.
All the plates are to be degreased before welding and, if left over night, they should be re-scratchbrushed to
remove any oxide film and be degreased again.
Filler materials for TIG welding shall be cleaned immediately before use.
Filler materials for MIG welding and other welding processes shall be protected from contamination during
the use and in particular between shifts.
Each run of weld metal shall be thoroughly cleaned before the next run is deposited. AIl scratchbrushes shall
be of stainless steel and shall be used only on aluminium or aluminium alloy.
The second side of joints welded from both sides shall be cleaned back to sound metal before depositing
any weld metal at the se
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