Pressure equipment - Part 1: Vocabulary

This European Standard specifies terms and definitions to be used for pressure equipment and assemblies within the scope of European Directives on pressure equipment.
NOTE   It can be applied to other pressure equipment.

Druckgeräte - Teil 1: Vokabular

Diese Europäische Norm legt Begriffe für Druckgeräte und Baugruppen fest, die durch die Europäische Richtlinieüber Druckgeräte („Druckgeräterichtlinie“, DGRL) abgedeckt sind.
ANMERKUNG   Sie kann für andere Druckgeräte auch angewandt werden.

Equipement sous pression - Partie 1: Vocabulaire

La présente Norme européenne spécifie les termes et définitions à utiliser pour les équipements sous pression et les ensembles visés par la Directive européenne relative aux équipements sous pression.
NOTE   Elle peut s’appliquer à d’autres équipements sous pression.

Tlačna oprema - 1. del: Slovar (vključno z dopolnilom A1)

Ta evropski standard določa izraze in definicije, ki se uporabljajo za tlačno opremo in sklope v okviru uporabe evropskih direktiv o tlačni opremi.
OPOMBA: Standard je mogoče uporabiti za drugo tlačno opremo.

General Information

Status
Published
Publication Date
11-Oct-2016
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
07-Oct-2016
Due Date
12-Dec-2016
Completion Date
12-Oct-2016

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Standards Content (sample)

SLOVENSKI STANDARD
SIST EN 764-1:2015+A1:2016
01-november-2016
1DGRPHãþD
SIST EN 764-1:2015
7ODþQDRSUHPDGHO6ORYDU YNOMXþQR]GRSROQLORP$
Pressure equipment - Part 1: Vocabulary
Druckgeräte - Teil 1: Vokabular
Equipement sous pression - Partie 1: Vocabulaire
Ta slovenski standard je istoveten z: EN 764-1:2015+A1:2016
ICS:
01.040.23 7HNRþLQVNLVLVWHPLLQVHVWDYQL Fluid systems and
GHOL]DVSORãQRUDER 6ORYDUML components for general use
(Vocabularies)
23.020.32 7ODþQHSRVRGH Pressure vessels
SIST EN 764-1:2015+A1:2016 en,fr,de

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

---------------------- Page: 1 ----------------------
SIST EN 764-1:2015+A1:2016
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2016
EUROPÄISCHE NORM
ICS 01.040.23; 23.020.30 Supersedes EN 764-1:2015
English Version
Pressure equipment - Part 1: Vocabulary

Equipement sous pression - Partie 1: Vocabulaire Druckgeräte - Teil 1: Vokabular

This European Standard was approved by CEN on 14 February 2015 and includes Amendment 1 approved by CEN on 5 June

2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 764-1:2015+A1:2016 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
Contents Page

European foreword ................................................................................................................................................................ 3

1 Scope ............................................................................................................................................................................. 4

2 Normative references ............................................................................................................................................. 4

3 Terms and definitions ............................................................................................................................................ 4

3.1 General terms ............................................................................................................................................................ 4

3.2 Terms related to design ......................................................................................................................................... 5

3.3 Terms related to manufacturing ..................................................................................................................... 20

3.4 Terms related to testing ..................................................................................................................................... 21

3.5 Terms related to interested parties ............................................................................................................... 23

Annex A (informative) Additional information on notions of maximum allowable pressure (PS)

and maximum / minimum allowable temperatures (TS / TS ) ................................................... 25

max min

Annex B (informative) Multilingual list of terms .................................................................................................... 27

Bibliography .......................................................................................................................................................................... 36

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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
European foreword

This document (EN 764-1:2015+A1:2016) has been prepared by Technical Committee CEN/TC 54 “Unfired

pressure vessels”, the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by February 2017, and conflicting national standards shall be

withdrawn at the latest by February 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 includes Amendment 1 approved by CEN on 2016-06-05.
This document supersedes !EN 764-1:2015".

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

!deleted text"

An informative annex on notions of allowable pressures and temperatures has been added.

An annex containing translations of terms to several other languages is in the course of preparation.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association.
EN 764, Pressure equipment comprises the following parts:
— Part 1: Vocabulary;
— Part 2: Quantities, symbols and units;
— Part 3: Definition of parties involved;
— Part 4: Establishment of technical delivery conditions for metallic materials;

— Part 5: Inspection documentation of metallic materials and compliance with the material specification;

— Part 6: Structure and content of operating instructions;
— Part 7: Safety systems for unfired pressure equipment.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
1 Scope

This European Standard specifies terms and definitions to be used for pressure equipment and assemblies

within the scope of European Directives on pressure equipment.
NOTE It can be applied to other pressure equipment.
2 Normative references
Not applicable.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

If a term or definition only applies to a special area or is different in different areas, the relevant area is

shown within brackets <….>.
3.1 General terms
3.1.1
ambient temperature

temperature of the surrounding atmosphere in the immediate vicinity of the pressure component

3.1.2
assembly

several pieces of pressure equipment assembled by a manufacturer to constitute an integrated and

functional whole
3.1.3
cryogenic applications
applications at low temperature
Note 1 to entry: Normally involving liquefied gases.
3.1.4
design validation

examination of the design documents to verify that the design conforms to the relevant product standard

3.1.5
fluid
gas, liquid and vapour in its pure phase as well as mixtures thereof
3.1.6
hazard category
category of the pressure equipment taking into account the potential hazards
3.1.7
joint coefficient

reduction coefficient (e.g. for a welded joint) related to the testing group and which is applied to the nominal

design stress
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.1.8
main pressure bearing parts

parts which constitute the envelope under pressure, essential for the integrity of the equipment

3.1.9
maximum allowable temperature
max

maximum temperature for which the pressure equipment is designed as specified by the manufacturer

3.1.10
minimum allowable temperature
min

minimum temperature for which the pressure equipment is designed as specified by the manufacturer

3.1.11
pipelines

piping or piping system designed for the conveyance of any fluid or substance to or from an installation

(onshore or offshore) starting from and including the first isolation device located within the installation and

including all the annexed equipment designed specifically for pipelines
3.1.12
piping

tubing, fittings, expansion joints, hoses or other pressure-bearing components, intended for the transport of

fluid, connected together and integrated into a pressure system
3.1.13
piping class

category in which piping is classified in accordance with the Pressure Equipment Directive 97/23/EC

3.1.14
piping system
pipe or system of pipes for the conveyance of fluids within an industrial site

Note 1 to entry: A piping system can be regarded as one single system, provided it conveys substances having the

same properties and it is a whole designed for the same allowable pressure.

Note 2 to entry: Interruption by different components such as pumps, machines, vessels, etc. does not preclude the

integration to one single piping.
3.1.15
pressure vessel

housing and its direct attachments up to the coupling point connecting it to other equipment, designed and

built to contain fluids under pressure
3.1.16
repair
process of rectifying a defect in either base material or weld
3.2 Terms related to design
3.2.1
action

imposed mechanical, thermal or thermo-mechanical influence which causes stress and/or strain in a

structure, e.g. an imposed pressure, force, displacement or temperature
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.2
action type
classification of action based on statistical properties and duration
3.2.3
analysis thickness
effective thickness available to resist the loading depending on the load case
3.2.4
anchor

rigid device, which may itself be subject to imposed displacement, used to prevent all relative pipe rotation

and displacement at the point of application, under the design conditions of temperature and loading

3.2.5
annular plate

flat end of annular form, connected to one cylindrical shell at its outside diameter and another at its inside

diameter, and subject predominantly to bending and not shear
3.2.6
application rule

generally recognized rule that follows the principles of the relevant product standard and satisfies their

requirements
3.2.7
assembly condition

condition applying when the gasket or joint contact surface is seated during assembly of the joint at ambient

temperature and the only loading comes from the bolts
3.2.8
assumed thickness

thickness assumed by the designer between the minimum required shell thickness and the shell analysis

thickness
3.2.9
bending stress

equivalent linear distributed stress through the wall of the pressure part, proportional to the distance from

the neutral axis
3.2.10
blind flange
blank flange
flat closure connected by bolts
3.2.11
bolted domed end

cover or blind flange consisting of a flange and a dome of constant radius of curvature

3.2.12
calculation pressure

differential pressure used for the purpose of the design calculations for a component

3.2.13
calculation temperature
temperature used for the purpose of the design calculations for a component
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.14
chamber
fluid space within a unit of pressure equipment
3.2.15
chamber volume

internal volume of a chamber, including the volume of nozzles to the first connection (flange, coupling, weld)

and excluding the volume of internal permanent parts (e.g. baffles, agitators)
3.2.16
characteristic function

characteristic function of an action is a representative function (of time) for the action

Note 1 to entry: Required for actions for which, in specific design checks, the time-dependence is of importance, e.g.

temperature/pressure transients during start-up or shut-down.
3.2.17
characteristic value

characteristic value of an action is a representative value which takes account of the variation of an action

3.2.18
coefficient of variation
measure of statistical dispersion (standard deviation divided by mean value)
3.2.19
collar
abutment for the flange
cylinder attached to the end tangent
3.2.20
combination factor

factor applied to design values of variable actions with stochastic properties if combined with pressure, or if

two or more of these actions are included in one load case
3.2.21
compliance
inverse of the axial stiffness of the assembly, symbol Y, units mm/N
3.2.22
component

part of pressure equipment which can be considered as an individual item for the calculation

3.2.23
constant hanger
constant support

pipe support with constant characteristic to carry vertical loads whilst permitting vertical displacements,

base mounted or suspended
3.2.24
continuous weld
weld extending along the entire length of a joint
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.25
convolution
corrugation
flexible unit of an expansion bellows
3.2.26
creep range

temperature range in which material characteristics used in design are time dependent

3.2.27
critical area
an area where the total fatigue damage index exceeds a maximum value
3.2.28
critical zone

highly stressed area where a fracture is expected to occur in a burst test or

where surface fatigue cracks are expected to be initiated due to fluctuating pressure loads

3.2.29
cut-off limit
cyclic stress range below which fatigue damage is disregarded
3.2.30
deposited thickness
weld throat thickness
thickness in the weld metal excluding any reinforcement
Note 1 to entry: The preferred term in ISO/TR 25901 is penetration depth.
3.2.31
design check

investigation of a component's safety under the influence of specified combinations of actions with respect

to specified limit states
3.2.32
design model
structural model used in the determination of effects of actions
3.2.33
design pressure
pressure chosen for the derivation of the calculation pressure of each component

Note 1 to entry: The design pressure normally refers to the top of the equipment and does not include pressure

generated by the weight of its content.

Note 2 to entry: If the equipment consists of several compartments, each compartment may have its own design

pressure.
3.2.34
design reference temperature
temperature used for determining the impact energy requirements
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.35
design stress range spectrum

histogram of the number of occurrences of all stress cycles of various ranges anticipated during the design

lifetime
3.2.36
design temperature

temperature chosen for the derivation of the calculation temperature of each component

3.2.37
differential pressure

pressure whose algebraic value is equal to the pressure difference on either side of a separation wall

3.2.38
discontinuity
shape or material change which affects the stress distribution
3.2.39
dished end
end of pressure vessel formed to have its open end cylindrical
Note 1 to entry: Normally manufactured from plate.
Note 2 to entry: Earlier called "dished head".
3.2.40
effect

response (e.g. stress, strain, displacement, resultant force or moment, equivalent stress resultant) of a

component to a specific action, or combination of actions
3.2.41
effective notch stress
stress which governs fatigue behaviour at a notch
3.2.42
effective stress concentration factor

ratio of effective notch stress (total stress), to structural stress at same point

3.2.43
ellipsoidal end
dished end having a truly ellipsoidal form
3.2.44
end tangents
straight unconvoluted portions at the ends of an expansion bellows
3.2.45
endurance limit

cyclic stress range below which, in the absence of any previous loading, no fatigue damage is

assumed to occur under constant amplitude loading
3.2.46
equalizing ring

T-shaped device that is tightly fitted into the root of the convolutions (corrugations) of expansion bellows in

order to equalize the movement of the different convolutions
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.47
equivalent full pressure cycles

number of full pressure cycles that cause the same damage as the applied pressure cycles of range ΔP

3.2.48
equivalent stress

uniaxial stress which produces the same damage as the applied multi-axial stresses

3.2.49
expansion bellows
flexible element consisting of one or more corrugations and the end tangents
3.2.50
external loads

forces and/or moments applied to a component due to actions other than internal or external pressure, or

static head of contained fluid, e.g. weight, wind loading, earthquake loading or loads from attached piping or

equipment
3.2.51
fatigue design curves
curves showing stress amplitude versus number of cycles
3.2.52
fixed tubesheet heat exchanger
heat exchanger with two tubesheets, each attached to the shell and channel
3.2.53
flat end

unstayed flat plate of generally constant thickness, connected to a shell by either welding or bolting, not

supported by stays or stay-tubes, not strengthened by beams, and supported only at its periphery so that it

is subject predominantly to bending
3.2.54
flexibility modulus

inverse of the stiffness modulus of a component, excluding the elastic constants of the material; axial: symbol

X, units 1/mm; rotational: symbol Z, units 1/mm
3.2.55
floating tubesheet heat exchanger

heat exchanger with a stationary tubesheet attached to the shell and channel and a floating tubesheet which

can move axially
3.2.56
full face flange

flange in which the face contact area, either direct or through a gasket or spacer, extends outside the circle

enclosing the bolts
3.2.57
full pressure cycles
pressure cycles of range ΔP =P
max
3.2.58
gasketed tubesheet
tubesheet attached to the shell and/or channel by bolting
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.59
global axial force
force acting along the axis of a shell
3.2.60
global bending moment
moment acting in a plane containing the axis of a shell
3.2.61
global shear force
transverse force acting perpendicular to the axis of a shell
3.2.62
governing weld joint

main full penetration butt joint, the design of which, as a result of membrane stresses, governs the thickness

of the component
3.2.63
gross discontinuity

structural or material discontinuity which affects the stress or strain distribution across the entire wall

thickness over a region of significant area

Note 1 to entry: Examples of gross structural discontinuities are end-to-cylindrical shell or conical shell-to-

cylindrical shell junction, flange-to-cylindrical shell junction, an opening in a shell, the junction of two cylindrical shells

of different diameter, thickness or material, or a stiffener-to-shell junction.
3.2.64
heavy stiffener

circumferential stiffener for external pressure, designated as 'heavy' by the designer

3.2.65
hub

cylindrical or conical projection on a flat end or flange provided so that the end or flange may be butt welded

to a cylindrical shell
3.2.66
integral flange
flange either integral with or welded to the shell
3.2.67
integral tubesheet
tubesheet attached to the shell and/or channel by welding
3.2.68
intermittent weld
series of weld elements made at intervals along a joint
3.2.69
interstiffener collapse

collapse of a section of cylinder between two stiffening rings, or between a stiffening ring and a vessel end

3.2.70
Kloepper type end

torispherical end in which the crown radius is equal to the external diameter and the knuckle radius is 10 %

of the external diameter
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.71
Korbbogen type end

torispherical end in which the crown radius is 80 % of the external diameter and the knuckle radius is 15,4

% of the external diameter
3.2.72
lap joint

flange assembly in which the bolt load is transmitted through a loose backing flange onto a stub

flange
3.2.73
lifetime monitoring

requirements for control and examination as stated in the operating instructions with the minimum

requirement for continuous recording of pressure and temperature and retention of records

3.2.74
ligament check
evaluation of the reinforcement between two adjacent openings
3.2.75
light stiffener

circumferential stiffener for external pressure, designated as ‘light’ by the designer

3.2.76
limit state

structural condition beyond which the design performance requirements of a component are not satisfied

Note 1 to entry: Limit states are classified into ultimate and serviceability limit states.

3.2.77
line stop

device to restrain axial displacement of the piping, defined by the restrained direction of motion

3.2.78
load case
combination of coincident actions

Note 1 to entry: Load cases are classified into normal operating load cases, special load cases and exceptional load

cases.
3.2.79
load change
change of load condition
3.2.80
load condition
set of applied simultaneous loads; designated by an identifier
3.2.81
load ratio

calculated load or moment applied to a component divided by the allowable load or moment

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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.82
local load

direct force, shear force or bending moment applying at a nozzle or attachment and due to a loading other

than the pressure in the vessel
3.2.83
local stress/strain concentration

stress/strain distribution related to very local geometric or material stress/strain raisers or temperature

fields, which affect the stress or strain distribution only through a fraction of the thickness

Note 1 to entry: Local stress/strain distributions are associated solely with localized types of deformation or strain,

have no significant non-local effect. Examples are stress concentrations at small fillet radii, small attachments, welds,

etc.
3.2.84
local discontinuity

discontinuity which only very locally affects the stress or strain distribution, across a fraction of the

thickness of the wall

Note 1 to entry: Stresses resulting from such a discontinuity can only cause highly localized strains and consequently

have no significant influence on the global behaviour of the wall.

Note 2 to entry: Examples of local structural discontinuities are small radius fillets, weld toes, non penetrated zones

in partial penetration welds.
3.2.85
loose flange
separate flange-ring abutting a stub or collar
3.2.86
main joint
welded joint assembling main pressure bearing parts
3.2.87
maximum allowable pressure

maximum pressure for which the pressure equipment is designed as specified by the manufacturer

3.2.88
maximum permissible pressure
max

maximum pressure obtained from the design by formulae or relevant procedures for a given component in a

given load case, or for the whole pressure equipment the minimum of these maximum permissible pressures

of all components
3.2.89
membrane stress
equivalent average stress through the wall of the pressure equipment
3.2.90
minimum metal temperature

lowest temperature determined for normal operations, start up and shut down procedures, possible process

upsets, such as flashings of fluid, which have an atmospheric boiling point below 0 °C, or during pressure or

leak testing
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.91
minimum possible fabrication thickness
smallest allowable thickness after fabrication
3.2.92
multiple creep load case
case where more than one period occurs in the whole lifetime of the vessel
3.2.93
narrow face flange

flange in which the gasket is entirely inside the circle enclosed by the bolts and there is no contact outside

the bolt circle
3.2.94
nominal design stress

stress value to be used in the formulae for the calculation of pressure components

3.2.95
nominal elastic limit
elastic limit applied for design of pressure equipment under external pressure
3.2.96
nominal stress
stress which would exist in the absence of a discontinuity
3.2.97
nominal thickness
thickness as specified on the drawings
3.2.98
nominal throat thickness

design value of the height of the largest isosceles triangle that can be inscribed in the section of a fillet weld

3.2.99
notch stress

total stress located at the root of a notch, including the non-linear part of the stress distribution

3.2.100
obround opening

opening with a shape given by two semicircles connected by two parallel straight lines

3.2.101
opening

through penetration of the shell which may or may not be fitted with a reinforcing plate, a reinforcing ring or

a nozzle
3.2.102
operating condition

condition when the hydrostatic end force due to the calculation pressure (internal or external)

acts on the flange
3.2.103
outer tube limit
circle which just circumscribes all the tubes
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.104
overall check

evaluation of the reinforcement in the cross-section including the walls on each side of each opening and the

reinforcing length of the adjacent shell
3.2.105
overall collapse
collapse of a section of cylinder which includes a light or heavy stiffener
3.2.106
partial safety factor

factor which is applied to a characteristic value of an action or a material parameter in order to obtain the

corresponding design value
3.2.107
peak stress

part of stress which is additive to the respective primary and secondary stresses, to form the total stress

Note 1 to entry: Peak stresses do not cause any noticeable distortion and are only important to fatigue and brittle

fracture in conjunction with primary and secondary stresses.
3.2.108
period

duration of a load case with constant loading and constant temperature inside the creep range

3.2.109
pipe guide, piping guide

device which permits pipe movement in a pre-determined direction whilst preventing movement in one or

more other directions
3.2.110
plane of substantial support

vessel end or a plane dividing a vessel into two parts, each of which is treated separately for external

pressure design purposes
3.2.111
primary stress

stress which satisfies the laws of equilibrium of applied loads (pressure, forces and moments)

Note 1 to entry: General primary membrane stresses are distributed in the structure such that no essential stress

redistribution occurs as a result of yielding. As plasticity develops, a stage is reached where the structure fails.

Note 2 to entry: Local primary stresses will be redistributed on yielding and will thus cause no immediate failure, but

will cause major (unacceptable) distortion of the structure.
3.2.112
pseudo-elastic stress range
stress range calculated assuming purely linear elastic material behaviour
3.2.113
reference thickness

thickness of a component to be used to relate the design reference temperature of the component with its

required impact test temperature
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SIST EN 764-1:2015+A1:2016
EN 764-1:2015+A1:2016 (E)
3.2.114
reinforced opening

opening where the reinforcement includes a contribution from the shell, a nozzle, a reinforcing plate or a

reinforcing ring
3.2.115
reinforcement

loaded cross-sectional area of metal considered to provide resistance to the pressure at an opening

3.2.116
reinforcing plate

plate which is fillet welded to the shell and contributes to the reinforcement

3.2.117
reinforcing rib

rectangular plate located along the radius of a circular flat end, located perpendicularly to its

plane and welded to it from both sides
3.2.118
reinforcing ring
set-in ring which contributes to the reinforcement

device that is tightly fitted into the root of the convolutions/corrugations in order to

reinforce expansion bellows against internal pressure
3.2.119
relief groove
peripheral groove in a flat end to be butt welded to a cylindrical shell
3.2.120
required
...

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