SIST EN ISO 21922:2022

SLOVENSKI STANDARD
01-januar-2022
Nadomešča:
SIST EN 12284:2004
Hladilni sistemi in toplotne črpalke - Ventili - Zahteve, preskušanje in označevanje
(ISO 21922:2021)
Refrigerating systems and heat pumps - Valves - Requirements, testing and marking
(ISO 21922:2021)
Kälteanlagen und Wärmepumpen - Ventile - Anforderungen, Prüfung und
Kennzeichnung (ISO 21922:2021)
Systèmes de réfrigération et pompes à chaleur - Robinetterie - Exigences, essais et
marquage (ISO 21922:2021)
Ta slovenski standard je istoveten z: EN ISO 21922:2021
ICS:
23.060.20 Zapirni ventili (kroglasti in Ball and plug valves
pipe)
27.080 Toplotne črpalke Heat pumps
27.200 Hladilna tehnologija Refrigerating technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 21922
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2021
EUROPÄISCHE NORM
ICS 27.080; 27.200 Supersedes EN 12284:2003
English Version
Refrigerating systems and heat pumps - Valves -
Requirements, testing and marking (ISO 21922:2021)
Systèmes de réfrigération et pompes à chaleur - Kälteanlagen und Wärmepumpen - Ventile -
Robinetterie - Exigences, essais et marquage (ISO Anforderungen, Prüfung und Kennzeichnung (ISO
21922:2021) 21922:2021)
This European Standard was approved by CEN on 23 May 2021.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21922:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Annex ZA (informative) Relationship between this European Standard and the essential
safety requirements of Directive 2014/68/EU . 4

European foreword
This document (EN ISO 21922:2021) has been prepared by Technical Committee ISO/TC 86
"Refrigeration and air-conditioning" in collaboration with Technical Committee CEN/TC 182
“Refrigerating systems, safety and environmental requirements” the secretariat of which is held by DIN.
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 May 2022, and conflicting national standards shall be
withdrawn at the latest by May 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12284:2003.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of EU
Directive(s) / Regulation(s).
For the relationship with EU Directive(s) / Regulation(s), see informative Annex ZA, which is an integral
part of this document.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 21922:2021 has been approved by CEN as EN ISO 21922:2021 without any modification.

Annex ZA
(informative)
Relationship between this European Standard and the essential safety
requirements of Directive 2014/68/EU
This European Standard has been prepared under a Commission’s standardization request “M/071" to
provide one voluntary means of conforming to essential safety requirements of Directive2014/68/EU
on the harmonisation of the laws of the Member States relating to the making available on the market of
pressure equipment.
Once this standard is cited in the Official Journal of the European Union under that Directive
2014/68/EU, compliance with the normative clauses of this standard given in Table ZA.1 confers,
within the limits of the scope of this standard, a presumption of conformity with the corresponding
essential safety requirements of that Directive, and associated EFTA regulations.
Table ZA.1 — Correspondence between this European Standard and Directive 2014/68/EU
Essential Safety Requirements of Clause(s)/subclause(s) of Remarks/Notes
Directive 2014/68/EU this EN
4.3 6.11 Material documentation
3.1.4 6.1.1, 6.4, 6.6, 6.7, D.3.3 Heat treatment
2.2.2 7.3 Design for adequate strength
7.1.2 Annex A.2 Allowable stresses
2.6 7.12 Corrosion
3.1.1 8 Preparation of the component parts
3.2.2, 7.4 9.1 Proof test
3.3 10.2 Marking and labelling
3.4 11 Operating instructions
7.2 Table A.2 Joint coefficients
2.2.3 Annex A, C and D Design for adequate strength by calculation
2.2.4 Annex B, C and D Design for adequate strength by experimental
method
4.1 a) and 7.5 Annex D Requirements to avoid brittle fracture
WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European
Standard is maintained in the list published in the Official Journal of the European Union. Users of this
standard should consult frequently the latest list published in the Official Journal of the European
Union.
WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of
this standard.
INTERNATIONAL ISO
STANDARD 21922
First edition
2021-08
Refrigerating systems and heat
pumps — Valves — Requirements,
testing and marking
Systèmes de réfrigération et pompes à chaleur — Robinetterie —
Exigences, essais et marquage
Reference number
ISO 21922:2021(E)
©
ISO 2021
ISO 21922:2021(E)
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2021 – All rights reserved

ISO 21922:2021(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 List of symbols . 4
5 General requirements . 6
5.1 Installation and operation . 6
5.2 Components under pressure . 6
5.3 Excessive mechanical stress . 7
5.4 Tightness . 7
5.5 Functioning of hand-operated valves . 7
5.6 Functioning of actuator-operated valves. 7
6 Materials . 7
6.1 General . 7
6.1.1 Using metallic materials . 7
6.1.2 Using non-metallic materials . 7
6.2 Requirements for materials to be used for pressure bearing parts . 8
6.3 Compatibility of connections . 8
6.4 Ductility . 8
6.5 Ageing . 8
6.6 Castings . 8
6.7 Forged and welded components . . 8
6.8 Nuts, bolts and screws . 8
6.9 Spindles . 9
6.10 Glass materials . 9
6.11 Requirements for documentation . 9
6.12 Impact energy KV measurement on sub-sized specimens .10
7 Design .10
7.1 General .10
7.2 Maximum allowable pressure .11
7.3 Valve and valve assembly strength design .11
7.4 Bodies and bonnets .12
7.5 Nuts, bolts, screws, fasteners and seals .12
7.6 Seat tightness .12
7.6.1 General.12
7.6.2 Seat tightness: type test .13
7.7 Screwed spindles and shafts .14
7.8 Design of glands .14
7.9 Valve seats .15
7.10 Caps . .15
7.11 Hand operated valves .16
7.12 Corrosion protection .16
8 Appropriate manufacturing procedures .16
9 Production testing .17
9.1 Strength pressure testing .17
9.2 Tightness testing .17
9.3 Seat sealing capacity .18
9.4 Caps . .18
10 Marking and additional information .18
ISO 21922:2021(E)
10.1 General .18
10.2 Marking .19
10.3 Example how to mark the allowable limits of pressure and temperature .19
10.4 Hand-operated regulating valves .19
10.5 Caps . .19
11 Documentation .20
11.1 General .20
11.2 Documentation for valves .20
11.3 Additional documentation for valve assemblies .20
Annex A (normative) Procedure for the design of a valve by calculation .21
Annex B (normative) Experimental design method for valves .24
Annex C (normative) Determination of the allowable pressure at the maximum operating
temperature .28
Annex D (normative) Determination of the allowable pressure at minimum operating
temperature — Requirements to avoid brittle fracture .29
Annex E (informative) Compilation of material characteristics of frequently used materials .40
Annex F (informative) Justification of the individual methods .60
Annex G (normative) Pressure strength verification of valve assemblies .66
Annex H (normative) Determination of category for valves .67
Annex I (informative) DN system .72
Annex J (normative) Additional requirements — Sight glasses and indicators .75
Annex K (normative) Compatibility screening test .78
Annex L (informative) Stress corrosion cracking .82
Annex M (normative) Method for sizing the operating element of hand-operated valves .85
Bibliography .87
iv © ISO 2021 – All rights reserved

ISO 21922:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO TC 86, Refrigeration and air-conditioning,
Subcomittee SC 1, Safety and environmental requirements for refrigerating systems, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 182, Refrigerating
systems, safety and environmental requirements, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This first edition is based on EN 12284:2003.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
ISO 21922:2021(E)
Introduction
This document is intended to describe the safety requirements, safety factors, test methods, test
pressures used, and marking of valves and other components with similar bodies for use in refrigerating
systems.
vi © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 21922:2021(E)
Refrigerating systems and heat pumps — Valves —
Requirements, testing and marking
1 Scope
This document specifies safety requirements, certain functional requirements, and marking of valves
and other components with similar bodies, hereinafter called valves, for use in refrigerating systems
including heat pumps.
This document includes requirements for valves with extension pipes.
This document describes the procedure to be followed when designing valve parts subjected to
pressure as well as the criteria to be used in the selection of materials.
This document describes methods by which reduced impact values at low temperatures may be taken
into account in a safe manner.
This document applies to the design of bodies and bonnets for pressure relief devices, including
bursting disc devices, with respect to pressure containment but it does not apply to any other aspects
of the design or application of pressure relief devices.
In addition, this document is applicable to valves with a maximum operating temperature not exceeding
1)
200 °C and a maximum allowable pressure not exceeding 160 bar .
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.
ISO 148-1, Metallic materials. Charpy pendulum impact test — Part 1: Test method
ISO 5149-1, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 1:
Definitions, classification and selection criteria
ISO/TR 15608, Welding — Guidelines for a metallic material grouping system
EN 12516-2, Industrial valves — Shell design strength — Part 2: Calculation method for steel valve shells
EN 13445-3, Unfired pressure vessels — Part 3: Design
EN 14276-2:2020, Pressure equipment for refrigerating systems and heat pumps — Part 2: Piping —
General requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5149-1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
1) 1 bar = 0,1 MPa.
ISO 21922:2021(E)
3.1
valve
device with a pressure enclosure and an intended additional functionality, such as influencing the fluid
flow by opening, closing or partially obstructing the passage of the flow or by diverting or mixing the
fluid flow, indicating moisture content or filtering the fluid flow
Note 1 to entry: A device with a pressure enclosure and an intended additional functionality is designated as
pressure accessory according to the European Pressure Equipment Directive 2014/68/EU.
3.2
extension pipe
piping connected to a valve by the valve manufacturer, which does not influence the pressure strength
of the valve itself
Note 1 to entry: Extension pipes often have different diameters in two ends.
Note 2 to entry: The application of extension pipes is determined by the manufacturer and has the advantage
that the pressure strength verification of the extension pipes becomes independent of the safety factors used for
the verification of the valve.
3.3
valve assembly
combination of a valve and one or more extension pipes
EXAMPLE An example of a valve assembly is given in Clause H.6.
3.4
operating range
combination of temperature and pressure conditions at which the valve can safely be operated
3.5
nominal size
DN
alphanumeric designation of size for components of a pipework system, which is used for reference
purposes comprising the letters DN followed by a dimensionless whole number which is indirectly
related to the physical size, in millimetres, of the bore or outside diameter of the end connections
Note 1 to entry: The number following the letters DN does not represent a measurable value and should not be
used for calculation purposes except where specified in this document.
Note 2 to entry: Where the nominal size is not specified, for the purpose of this document it is assumed to be the
internal diameter of the pipe or component in mm (DN/ID).
Note 3 to entry: Nominal size is not the same as port size which is commonly used for the size of the valve seat
opening.
Note 4 to entry: For additional information regarding the DN system, see Annex I.
[SOURCE: ISO 6708:1995, 2.1, modified — Notes to entry added.]
3.6
nominal pressure
PN
numerical designation which is a convenient rounded number for reference purposes
Note 1 to entry: All equipment of the same nominal size (DN) designated by the same PN number shall have
compatible mating dimensions.
[SOURCE: ISO 7268:1983/Amd.1:1984, modified]
3.7
corrosion
all forms of material waste (e. g. oxidation, erosion, wear and abrasion)
2 © ISO 2021 – All rights reserved

ISO 21922:2021(E)
3.8
maximum operating temperature
highest temperature that can occur during operation or standstill of the refrigerating system or during
testing under test conditions
3.9
minimum operating temperature
lowest temperature that can occur during operation or standstill of the refrigerating system or during
testing under test conditions
3.10
pressure bearing part
part, which is subject to stress due to internal pressure greater than 50 kPa (0,5 bar) gauge
3.11
main pressure bearing part
part, which constitute the envelope under pressure, essential for the integrity of the equipment
Note 1 to entry: Examples are bonnets, housings, end covers and flanges.
[SOURCE: EN 13445-1:2014]
3.12
seat tightness class
letter from A to G indicating the internal tightness of the valve across the valve seat(s)
3.13
competent body
third party organisation which has recognized competence in the assessment of quality systems for the
manufacture of materials and in the technology of the materials concerned
Note 1 to entry: National legislation can place additional requirements on the competent body depending on the
market for which the valve is intended.
3.14
type of valve connection
standard and size of the valve connection to other equipment directly fixed to the valves end
Note 1 to entry: Possible types of valve connection are e.g.
a) NPS 2, i.e. a butt-welding connection to ASME/ANSI B 36.10 2 inch steel pipe,
b) NPT ½ , i.e. a screwed connection with ½ inch male end according to ASME/ANSI B 1.20.1,
c) EN 1092-1/11/C/DN 200 x 6,3/PN 40, i.e. a flange type 11 with facing type C (tongue) of nominal size DN 200,
wall thickness 6,3 mm, PN 40.
3.15
pressure sensitive part
part of a valve which will not have a reliable function after exposure to the greater of 1,5 times PS and
1,25 times PS
Note 1 to entry: Examples include bellows, diaphragms or float balls.
3.16
spindle
part of the valve which actuates the intended functionality, e.g. opening or closing for influencing the
fluid flow
Note 1 to entry: A valve does not necessarily need to incorporate a spindle.
ISO 21922:2021(E)
3.17
maximum allowable pressure
PS
maximum pressure for which the valve or valve assembly is designed, as specified by the manufacturer
3.18
maximum allowable pressure at ambient temperature (–10 °C to + 50 °C)
PS
maximum pressure for which the valve or valve assembly is designed, as specified by the manufacturer,
at ambient temperature (–10 °C to + 50 °C)
4 List of symbols
Symbols used in this document are given in Table 1:
Table 1 — List of symbols
A Elongation after fracture where the measured length is equal or greater than 0,4 mm
L
times of diameter of the rod
A Elongation after fracture where the measured length is equal to 5 times of di- %
ameter of the rod
a Lifetime in years for calculating effect of corrosion; typically 20 years —
C Factor to compensate for the quality of a casting —
Q
D Diameter of the hand-wheel mm
δ Negative wall thickness tolerance mm
e
e Actual wall thickness at given measuring points of the valve to be tested mm
act
e Reference thickness is the minimum material thickness needed to give adequate mm
B
strength to pressure bearing parts
e Reduction in wall thickness caused by occurrence of corrosion mm
c
e Component wall thickness as specified in the design drawing mm
con
F Operating manual force to size the manual operating element N
F Maximum manual force to size the manual operating element N
s
KV Impact rupture energy J
KV Threshold value of impact rupture energy, where the impact rupture energy is J
defined as independent of the temperature
t
KV Standard value of impact rupture energy at standard temperature of the material J
KV Impact rupture energy at minimum operating temperature TS J
TS min min
K Rate of flow of water in cubic metres per hour for a differential pressure Δp of m /h
VS
1 bar (0,1 MPa) at the rated full opening
L Leakage in percent of K %
VS
l Length of the lever or radius of the crank circle mm
P Maximum allowable design test pressure bar
F
PS Maximum allowable pressure bar
PS Maximum allowable pressure at ambient temperature (−10 °C to + 50 °C) bar
PS Maximum allowable pressure at maximum operating temperature bar
TS max
PS Maximum allowable pressure at minimum operating temperature bar
TS min
P Minimum burst test pressure (greater than P ) bar
Test F
p Upstream pressure bar
p Downstream pressure bar
Δp Differential pressure bar
NOTE  1 bar = 0,1 MPa.
4 © ISO 2021 – All rights reserved

ISO 21922:2021(E)
Table 1 (continued)
p' Testing pressure of each valve after production bar
Q Mass flow rate kg/h
M
Q Downstream volume flow rate m /h
V
R Yield strength, 1,0% offset MPa, N/mm
e 1,0
R Yield strength, 1,0% offset at maximum operating temperature MPa, N/mm
e 1,0 TS max
R Yield strength, 0,2% offset at ambient temperature MPa, N/mm
e 0,2
R Proof strength, 0,2% offset at ambient temperature MPa, N/mm
p 0,2
R Proof strength, 0,2% offset at minimum operating temperature MPa, N/mm
p 0,2 TS min
R Proof strength, 0,2% offset at temperature t MPa, N/mm
p 0,2/t
R Proof strength, 0,2% offset at maximum operating temperature MPa, N/mm
p 0,2 TS max
R Proof strength, 1,0% offset at ambient temperature MPa, N/mm
p 1,0
R Upper yield strength MPa, N/mm
eH
R Upper yield strength at maximum operating temperature MPa, N/mm
eH TS max
R Tensile strength MPa, N/mm
m
R Tensile strength at maximum operating temperature MPa, N/mm
m TS max
R Actual tensile strength of the material of the valve to be tested MPa, N/mm
m act
R Tensile strength used for the design MPa, N/mm
m con
ρ Density of the actual fluid kg/m
ρ Density of water at 15,5 °C kg/m
ρ Upstream density kg/m
ρ Downstream density kg/m
S Factor to compensate effects of corrosion —
C
S Factor for the calculation of the burst test pressure taking into account the tensile —
con
strength according to Table A.1
S Factor to allow for forming —
F
S Factor taking into consideration the impact rupture energy reduction due to —
TS min
minimum operating temperature
S Factor to allow for the reduction in strength due to the maximum operating —
TS max
temperature
S Factor to allow for the test pressure —
σ
σ Initial design stress MPa, N/mm
con
σ Allowable stress values derived from σ MPa, N/mm
corr con
t Lowest temperature at which pressure bearing parts can be used, if their load °C
min 25
amounts to 25 % of the allowable design stress at 20 °C, taking the safety factors
according to Table A.1 into account
t Lowest temperature at which pressure bearing parts can be used, if their load °C
min 75
amounts to 75 % of the allowable design stress at 20 °C, taking the safety factors
according to Table A.1 into account
t Lowest temperature at which pressure bearing parts can be used, if their load °C
min 100
amounts to 100 % of the allowable design stress at 20 °C, taking the safety factors
according to Table A.1 into account
T Design reference temperature is the minimum operating temperature TS ad-
R min
justed. Used when determining TS based on reference thickness e
min B
T Temperature adjustment of the design reference temperature T
S R
T Impact test temperature
KV
TS Operating temperature °C
TS Lowest operating temperature °C
min
NOTE  1 bar = 0,1 MPa.
ISO 21922:2021(E)
Table 1 (continued)
TS Maximum operating temperature °C
max
τ Torque, under specified conditions, to operate the valve Nm
τ Maximum torque, under specified conditions, to seat or unseat the obturator or Nm
s
to overcome temporary intermediate dynamic conditions
V Inner volume of a valve l
X Correction of the actual wall thickness relative to the wall thickness of the design —
Δp
assigns the value
K —
P
Y Correction on the basis of current strength values of the test sample relative to —
the strength parameters for the design of valves
Z Factor to allow for the quality of a joint (e.g. welded joint) —
∂ Wall thickness reduction per year mm
NOTE  1 bar = 0,1 MPa.
5 General requirements
5.1 Installation and operation
Valves and valve assemblies shall be designed for the operational loads and conditions as specified in
the relevant refrigerating system safety standard.
Relevant refrigerating system safety standards include:
a) ISO 5149-1, ISO 5149-2 and ISO 5149-4,
b) IEC 60335-2-40,
c) ANSI/ASHRAE Standard 15,
d) EN 378-1, EN 378-2 and EN 378-4.
The application of extension pipes is determined by the manufacturer.
NOTE 1 When extension pipes are applied, the finished device is a valve assembly (see. 3.3) consisting of a
valve (see 3.1) and extension pipes (see 3.2).
NOTE 2 The application of extension pipes has the advantage that the pressure strength verification of the
pipes becomes independent of the safety factors used in the verification of the valve body.
The lowest operating temperature (TS ), maximum operating temperature (TS ), and the maximum
min max
allowable pressure (PS) shall be the same for extension pipes and valve assemblies as for the valve
incorporated in the valve assembly.
The manufacturer shall classify the category of the valve, extension pipe, and valve assembly according
to Annex H as appropriate.
5.2 Components under pressure
All parts of the valve or valve assembly shall be designed and manufactured to remain leak proof and to
withstand the pressures which may occur during operation, standstill and transportation, taking into
account the thermal, physical and chemical stresses to be expected.
6 © ISO 2021 – All rights reserved

ISO 21922:2021(E)
5.3 Excessive mechanical stress
After installation, valves and valve assemblies, especially valves for hot gas defrosting, shall not be
under excessive mechanical stress from fitting of the pipe or from temperature variations during
operation.
NOTE Hot gas defrosting can produce hydraulic shocks resulting in transient pressures in excess of PS.
5.4 Tightness
The valve or valve assembly shall not leak to the outside when tested as described in 9.2. Valve seats
shall seal to a degree specified in 9.3.
5.5 Functioning of hand-operated valves
Proper functioning of hand-operated valves shall be ensured for the entire operating range up to the
allowable pressure PS and the associated allowable temperature TS.
5.6 Functioning of actuator-operated valves
Proper functioning of actuator-operated valves operated by the fluid or by energy from an external
source, shall be ensured for the entire operating range, which is to be specified by the manufacturer.
6 Materials
6.1 General
6.1.1 Using metallic materials
Metallic materials, included welding filler metals, solders, brazing metals and sealants, shall allow
for the thermal, chemical and mechanical stresses arising in system operation. Materials shall be
resistant to the refrigerants, solvents (in absorption systems) and refrigerant-oil mixtures used in each
particular case.
NOTE A list of suitable materials is found in Annex E of this document. Steel information can also be found in
EN 13445-2 or ASME B 31.5, along with other useful information.
If material properties are changed during the method of manufacture (e.g. through welding or deep
drawing) to such an extent that the strength and/or Charpy notch energies, according to ISO 148-1, are
reduced, these reduced values shall be taken into consideration by corrections or shall be subject to
suitable compensatory material treatment (e.g. heat treatment).
Residual stress can e.g. decrease impact strength and increase stress corrosion (see Annex L). Where
relevant, it shall be verified that the residual stress does not impose adverse implications.
Materials with a deformation higher than 2 % shall be heat treated with the respective material
specifications. Alternatively, the proof against inner pressure shall be verified by test, if no heat
treatment is used.
6.1.2 Using non-metallic materials
It is permitted to use non-metallic materials, e.g. for gaskets, coatings, insulating materials, and
sightglasses, provided that they are compatible with other materials, refrigerants and lubricants.
The compatibility of rubber and thermoplastic sealing materials and flat gaskets shall be evaluated
according to Annex K.
ISO 21922:2021(E)
6.2 Requirements for materials to be used for pressure bearing parts
Materials listed in this document (see Annex E) have been identified for use in valves.
Lamellar cast iron shall not be used but nodular cast iron can be used down to temperatures at which it
can be proved to achieve overall levels of safety equivalent to alternative materials.
NOTE EN 1563 contains information on nodular cast iron.
Free-cutting steel generally does not have the impact strength, KV , required for pressure bearing
parts. It may be used for pressure bearing parts where pressure is not a significant design factor.
Where new materials are proposed, the design shall be carried out using Annexes A to D provided the
yield strength or proo
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