oSIST prEN 12953-9:2023
(Main)Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessories
Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessories
This European Standard specifies requirements for limiters (or limiting devices) which are incorporated into safety systems for shell boilers as defined in EN 12953-1. A limiter (or limiting device) can be either: - a safety accessory as defined in the Pressure Equipment Directive, Article 1, clause 2.1.3, and needs to include the safety logic and final actuator, or - one element of a safety system, for example, a self-monitoring water level sensor used as part of a safety accessory as defined in the Pressure Equipment Directive, Article 1, clause 2.1.3. The overall boiler protection function needs to be provided in association with additional safety logic (where appropriate) and a final actuator. The design requirements and examination of functional capability for the limiters are covered in this European Standard. For an explanation of the extent of the limiter (or limiting device) see Figure A.1.
Großwasserraumkessel Teil 9: Anforderungen an Begrenzungseinrichtungen an Kessel und Zubehör
Chaudières à tubes de fumée Partie 9: Exigences pour les dispositifs de limitation de lachaudière et de ses accessoires
Mnogovodni kotli - 9. del: Zahteve za omejilne naprave kotla in opremo
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 12953-9:2023
01-junij-2023
Mnogovodni kotli - 9. del: Zahteve za omejilne naprave kotla in opremo
Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessories
Großwasserraumkessel Teil 9: Anforderungen an Begrenzungseinrichtungen an Kessel
und Zubehör
Chaudières à tubes de fumée Partie 9: Exigences pour les dispositifs de limitation de
lachaudière et de ses accessoires
Ta slovenski standard je istoveten z: prEN 12953-9
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
oSIST prEN 12953-9:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 12953-9:2023
DRAFT
EUROPEAN STANDARD
prEN 12953-9
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2023
ICS 27.060.30 Will supersede EN 12953-9:2007
English Version
Shell boilers - Part 9: Requirements for limiting devices of
the boiler and accessories
Chaudières à tubes de fumée - Partie 9: Exigences pour Großwasserraumkessel - Teil 9: Anforderungen an
les dispositifs de limitation de lachaudière et de ses Begrenzungseinrichtungen an Kessel und Zubehör
accessoires
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 269.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12953-9:2023 E
worldwide for CEN national Members.
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Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 8
4 Requirements for limiter . 10
4.1 General . 10
4.2 Components . 11
4.3 Materials and design . 12
4.4 Electrical equipment . 13
4.5 Fault assessment . 14
4.5.1 General . 14
4.5.2 Fault models and exclusions . 17
4.6 Marking . 19
4.7 Operating instructions . 19
4.8 Type examination of functional capability . 20
4.9 Routine testing for final assessment . 22
5 Special requirements for water level limiters . 23
5.1 Design . 23
5.1.1 General . 23
5.1.2 Internal protection tubes . 23
5.1.3 External chambers . 23
5.2 Floating devices . 24
5.3 Level electrode devices . 24
5.4 Additional requirements for differential pressure sensors . 26
5.5 Type examination of functional capability . 26
6 Special requirements for pressure limiters . 28
6.1 Design . 28
6.2 Fault exclusion of mechanical failure of moving parts . 29
6.3 Type examination of functional capability . 29
7 Special requirements for temperature limiters . 31
7.1 Design . 31
7.2 Type examination of functional capability . 31
8 Special requirements for water conductivity limiters . 31
8.1 Internally mounted transducers . 31
8.2 Externally mounted transducers . 31
8.3 Transducers . 32
8.4 Type examination of functional capability of water conductivity limiter . 32
Annex A (informative) Limiting devices . 33
Annex B (informative) Example of an examination plan . 34
Annex C (informative) Marking of limiters . 36
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Annex D (normative) Immunity against electrical and electromagnetic influences —
Requirements and testing . 39
D.1 General . 39
D.2 Immunity against mains voltage variations . 39
D.3 Immunity against short-time voltage interruptions and reductions . 40
D.4 Immunity against mains frequency changes . 40
D.5 Immunity against electrostatic discharge (ESD) . 40
D.6 Immunity against fast transient disturbance variables (burst) . 41
D.7 Immunity against surges . 41
D.8 Immunity against high-frequency electromagnetic fields . 42
D.9 Immunity against conducted disturbances induced by high frequency fields . 42
D.10 Immunity against power frequency magnetic fields . 43
Annex E (informative) Deterministic or probabilistic procedures for limiter safety cases . 44
E.1 General . 44
E.2 Relationships . 44
E.2.1 Type test . 44
E.2.2 Determination of characteristic data for use in protective circuits with SIL
classification (SIL = safety integrity level). 44
Annex F (normative) Requirements and tests of electrical safety . 45
Annex G (informative) Significant technical changes between this document and the
previous edition . 47
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/68/EU aimed to be covered . 48
Bibliography . 49
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European foreword
This document (prEN 12953-9:2023) has been prepared by Technical Committee CEN/TC 269 “Shell and
water-tube boilers”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12953-9:2007.
Annex G provides details of significant technical changes between this European Standard and the
previous edition.
The European Standard series EN 12953 concerning shell boilers consists of the following Parts:
— Part 1: General
— Part 2: Materials for pressure parts of boilers and accessories
— Part 3: Design and calculation for pressure parts
— Part 4: Workmanship and construction of pressure parts of the boiler
— Part 5: Inspection during construction, documentation and marking of pressure parts of the boiler
— Part 6: Requirements for equipment for the boiler
— Part 7: Requirements for firing systems for liquid and gaseous fuels for the boiler
— Part 8: Requirements for safeguards against excessive pressure
— Part 9: Requirements for limiting devices of the boiler and accessories
— Part 10: Requirements for feedwater and boiler water quality
— Part 11: Acceptance tests
— Part 12: Requirements for grate firing systems for solid fuels for the boiler
— Part 13: Operating instructions
Although these Parts may be obtained separately, it should be recognized that the Parts are
interdependent. As such, the design and manufacture of shell boilers requires the application of more
than one part in order for the requirements of the European Standard to be satisfactorily fulfilled.
NOTE A “Boiler Helpdesk” has been established in CEN/TC 269 which can be contacted for any questions
regarding the application of the European Standards series EN 12952 and EN 12953 see the following website:
http://www.boiler-helpdesk.din.de.
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 relationship with EU Directive(s) / Regulation(s), see informative Annex ZA, which is an integral part
of this document.
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Introduction
The types of limiters which are to be fitted to boilers are specified in prEN 12953-6:2023 and the design
of the safety systems are specified in EN 50156-1:2015.
In order to provide the necessary safety function, for example, to cut off the energy supply to the boiler
in the event of a low water fault, the limiter is connected to other elements in the safety system.
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1 Scope
This document specifies requirements for limiters which are incorporated into safety systems for shell
boilers as specified in EN 12953-1:2012.
The design requirements and examination of the limiters are covered in this document.
NOTE See Annex E for determination of the characteristic data for use in protective circuits with a safety
integrity level (SIL) rating. The requirements for limiters with regard to the safety integrity level (SIL), for example,
in accordance with EN 61508 are not regulated in this document.
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 ISO 228-1:2003, Pipe threads where pressure-tight joints are not made on the threads — Part 1:
Dimensions, tolerances and designation (ISO 228-1:2000)
EN 10226-1:2004, Pipe threads where pressure tight joints are made on the threads — Part 1: Taper
external threads and parallel internal threads - Dimensions, tolerances and designation
1
prEN 12953-6:2023, Shell boilers — Part 6: Requirements for equipment for the boiler
EN 12953-10:2003, Shell boilers — Part 10: Requirements for feedwater and boiler water quality
EN 14597:2012, Temperature control devices and temperature limiters for heat generating systems
EN 50156-1:2015, Electrical equipment for furnaces and ancillary equipment — Part 1: Requirements for
application design and installation
EN 50156-2:2015, Electrical equipment for furnaces and ancillary equipment — Part 2: Requirements for
design, development and type approval of safety devices and subsystems
2
EN 60529:1991, Degrees of protection provided by enclosures (IP code) (IEC 60529:1989/Amd1:2000,
Amd2:2013)
EN IEC 60664-1:2020, Insulation coordination for equipment within low-voltage systems — Part 1:
Principles, requirements and tests (IEC 60664-1:2020)
EN 60730-1:2016, Automatic electrical controls — Part 1: General requirements (IEC 60730-1:2016)
3
EN 60730-2-6:2016, Automatic electrical controls - Part 2-6: Particular requirements for automatic
electrical pressure sensing controls including mechanical requirements (IEC 60730-2-6:2015)
1
At draft stage.
2
Document impacted by A1:2000 and A2:2013.
3
Document impacted by A1:2020.
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EN IEC 60730-2-9:2019, Automatic electrical controls — Part 2-9: Particular requirements for
temperature sensing controls (IEC 60730-2-9:2015)
EN IEC 60730-2-15:2019, Automatic electrical controls - Part 2-15: Particular requirements for
automatic electrical air flow, water flow and water level sensing controls (IEC 60730-2-15:2017)
EN 60747-5-2:2001, Discrete semiconductor deviees and integrated circuits — Part 5-2: Optoelectronic
deviees — Essential ratings and characteristics (IEC EN 60747-5-2:1997)
EN 60747-5-5:2011, Semiconductor devices — Discrete devices — Part 5-5: Optoelectronic devices —
Photocouplers (IEC 60747-5-5:2007)
EN 60947-5-1:2017, Low-voltage switchgear and controlgear — Part 5-1: Control circuit devices and
switching elements — Electromechanical control circuit devices (IEC 60947-5-1:2016 + COR1:2016)
EN 61000-4-2:2009, Electromagnetic compatibility (EMC) — Part 4-2: Testing and measurement
techniques — Electrostatic discharge immunity test (IEC 61000-4-2:2009)
EN IEC 61000-4-3:2020, Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement
techniques — Radiated, radio-frequency, electromagnetic field immunity test (IEC 61000-4-3:2020)
EN 61000-4-4:2012, Electromagnetic compatibility (EMC) — Part 4-4: Testing and measurement
techniques — Electrical fast transient/burst immunity test (IEC 61000-4-4:2012)
5
EN 61000-4-5:2014, Electromagnetic compatibility (EMC) — Part 4-5: Testing and measurement
techniques — Surge immunity test (IEC 61000-4-5:2014/Amd1:2017)
EN 61000-4-6:2014, Electromagnetic compatibility (EMC) — Part 4-6: Testing and measurement
techniques — Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000-4-6:2013)
EN 61000-4-8:2010, Electromagnetic compatibility (EMC) — Part 4-8: Testing and measurement
techniques — Power frequency magnetic field immunity test (IEC 61000-4-8:2009)
6
EN IEC 61000-4-11:2020, Electromagnetic compatibility (EMC) — Part 4-11: Testing and measurement
techniques — Voltage dips, short interruptions and voltage variations immunity tests
(IEC 61000-4-11:2020)
EN IEC 61000-6-2:2019, Electromagnetic compatibility (EMC) — Part 6-2: Generic standards – Immunity
standard for industrial environments (IEC 61000-6-2:2016)
EN 61140:2016, Protection against electric shock — Common aspects for installation and equipment
(IEC 61140:2016)
EN IEC 61558-1:2019, Safety of power transformers, power supplies, reactors and similar products — Part
1: General requirements and tests (IEC 61558-1:2019)
4
Document impacted by A1:2019 and A2:2020.
5
Document impacted by A1:2017.
6
Document impacted by AC:2020-06 and AC:2022-10.
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EN 61558-2-6:2009, Safety of transformers, reactors, power supply units and similar products for supply
voltages up to 1100 V — Part 2-6: Particular requirements and tests for safety isolating transformers and
power supply units incorporating safety isolating transformers (IEC 61558-2-6:2009)
7
EN 61558-2-16:2009, Safety of power transformers, power supply units and similar — Part 2-17:
Particular requirements for safety isolating transformers for switch mode power supplies
(IEC 61558-2-16:2009/Amd1:2013)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in prEN 12953-6:2023,
EN 12953-10:2003 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/
3.1
limiter
limiting device
safety accessory which, on reaching a limiting value (water level, pressure, temperature, flow, water
quality), is used to interrupt and lock out the energy supply
Note 1 to entry: A limiter is an element of a safety device and a safety accessory for shell boilers as specified in
the Pressure Equipment Directive 2014/68/EU, Article 2, Clause 4.
Note 2 to entry: A limiting device comprises
— a measuring function and
— optional with a display and
— an activation function for correction, or shut-down, or safety shut-down and fault shut-down, and which
is used to carry out safety related functions as specified in the PED, on its own or as part of a safety (protective)
system (e.g. sensors, limiters). If this is achieved by multichannel systems, then all items or limiters for safety
purposes are included within the safety (protective) system.
3.2
self-monitoring
regular and automatic determination that all chosen components of a safety system are capable of
functioning as required
3.3
redundancy
provision of more than one device or system which, in the event of a fault, will still be provided by the
necessary facilities
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Document impacted by A1:2013.
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3.4
diversity
provision of different means of performing the required function, e.g. other physical principles or other
ways of solving the same problem
3.5
safety shut-down
process which is effected immediately following the detection of a fault within the limiter or caused by
exceeding the threshold of the process value limit resulting in a defined state with deactivated terminals
of the safety output(s)
3.6
fault shut-down
safety shut-down with lock-out
3.7
lock-out
safety shut-down condition of the limiter, such that a restart can only be accomplished by manual
unlocking of the limiter or by manual unlocking of the safety logic on site and by no other means
3.8
sensor
measuring element for mechanical, physical or electrical properties optionally with transmitting and/or
transducing functions (provides an output quantity having a specified relation to the input quantity)
Note 1 to entry In this document, the wording “sensor” can be understood as “transducer” if the requirements
are combined with transmitting and/or transducing funtions.
3.9
make-up water
water which compensates for losses of water and steam from the system
[SOURCE: EN 12953-10:2003, 3.3/prEN 12953-6:2023, 3.20]
3.10
feedwater
mixture of returned condensate and/or make up water supplied to the boiler inlet
[SOURCE: EN12953-10:2003, 3.4/prEN 12953-6:2023, 3.21]
3.11
boiler water
water within a natural or assisted circulation boiler
[SOURCE: EN 12953-10:2003, 3.6]
3.12
water hardness
sum of alkaline earths in water (essentially calcium and magnesium ions) in millimoles per liter (mmol/l)
3.13
set point, limiting value
specific value of a measurand (e.g. conductivity or water hardness) which when reached interrupts the
feedwater supply (e.g. permissible limits for boiler or feedwater in accordance with EN 12953-10)
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3.14
limit value range
range of a measurand (e.g. conductivity or water hardness) within which the limit can be set
3.15
sample line
supply of the water which is to be monitored to the monitoring system
3.16
dead time
time period between exceeding the permissible limit and output of the switching command
3.17
allowable temperature range
maximum/minimum allowable temperature TS of the medium indicated by the manufacturer
Note 1 to entry maximum allowable temperature (TS) is a maximum temperature for which the pressure
equipment is designed.
For examples:
— for hot water boiler, TS means the flow temperature measured at the outlet branch;
— for steam generator, TS means the saturated steam temperature at PS;
— for superheater, TS means the temperature of the hot steam measured at the outlet branch;
— for economizer, TS means the flow temperature measured at the outlet branch.
3.18
ambient temperature
ambient air temperature range in which the device may be operated as specified by the manufacturer
3.19
maximum allowable pressure
maximum allowable pressure PS of the medium indicated by the manufacturer and for which the
pressure equipment is designed
3.20
fail-safe
limiter is fail-safe if it possesses the capability of remaining in a safe condition or transferring
immediately to another safe condition in the event of certain faults occurring
4 Requirements for limiter
4.1 General
4.1.1 The limiters described in this document are elements of a safety device and safety accessories
fixed for shell boilers and on reaching a limiting value (water level, pressure, temperature and
conductivity) interrupt and lock out the energy supply. A limiter contains a sensor, possibly a sensor
control unit and ends at the output contact. The following safety logic and actuating element are not
components of this part of the document.
NOTE 1 For safety logic and actuating elements, see also Figure A.1.
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A limiter shall be such that, as a minimum, single faults in any related part shall not lead to a loss of the
safety function. For additional fault considerations, the requirements specified in 4.5 shall be fulfilled.
NOTE 2 EN 50156-1:2015 is mentioned several times in this document. EN 50156-2:2015, 4.2.2 mentions type
testing to fulfil EN 50156-1:2015. If the type testing according to EN 50156-2:2015 is not following the required
conformity assessment procedure for a safety accessory according to PED, a conformity assessment procedure of
the limiting device or protective system according to PED, indivually or during assembly, can be performed.
NOTE 3 Figure A.1 shows the scope of a limiter and of a protective system. Conformity assessment procedure
according to PED could refer to either the scope of a limiter or of the protective system. The boiler manufacturer
selects the conformity assessment procedure for protective system, if the limiter is not covered by a separate
conformity assessment procedure, the boiler manufacturer is responsible for all requirements of the protective
system including the limiters.
4.1.2 The requirements of Clause 4 have been established to ensure uniform assessment of different
devices.
a) The installation requirements associated with the selected measurement principle shall be taken into
consideration.
b) Simple removal and reinstallation for inspection and cleaning purposes shall be ensured.
c) Limiters shall function independently of each other and of controls. Other functions of the limiter are
accepted if the safety functions of the limiter are not affected.
d) Automatic locking or manual resetting shall be realized as a part of the limiter or as a part of the
safety logic.
e) Instructions shall be available with the limiter including necessary precautions for its safe
installation.
f) The function of fail-safe limiters, if applicable including their interlocking device, shall not be
impaired by other electrical circuits or controls. This applies in particular to devices with indicating
and warning devices and/or contacts for such equipment.
4.2 Components
This limiter shall consist of one or more units needed to provide the necessary safety function.
The limiter shall be comprised of the following elements where applicable: connection lines, spacer,
chamber, co
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