SIST EN 12953-9:2007

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

Diese Europäische Norm legt die Anforderungen an Begrenzer (oder Begrenzungseinrichtungen) fest, die in Sicherheitssystemen für Großwasserraumkessel nach EN 12953 1 eingebaut sind.
Ein Begrenzer (oder eine Begrenzungseinrichtung) kann entweder
   ein Ausrüstungsteil mit Sicherheitsfunktion sein, wie in der Druckgeräterichtlinie, Artikel 1, 2.1.3, festgelegt, das mit einer Sicherheitskette und einem Stellglied versehen ist, oder
   ein Element eines Sicherheitssystems sein, z. B. ein selbstüberwachender Wasserstandfühler als Teil eines Ausrüstungsteils mit Sicherheitsfunktion nach der Festlegung in der Druckgeräterichtlinie, Artikel 1, 2.1.3. Die Schutzfunktion für den gesamten Kessel wird mit einer zusätzlichen Sicherheitskette (wo angemessen) und einem Stellglied abgedeckt.
Diese Europäische Norm umfasst die Anforderungen an die Ausführung und die Prüfung der Funktions¬sicherheit der Begrenzer.
Der Funktionsumfang des Begrenzers (oder der Begrenzungseinrichtung) ist in Bild A.1 verdeutlicht.

Chaudieres a tubes de fumée - Partie 9: Exigences pour les dispositifs de limitation de la chaudiere et de ses accessoires

Mnogovodni kotli - 9. del: Zahteve za omejilne naprave kotla in opremo

General Information

• Status: Published
• Publication Date: 07-Aug-2007
• ICS: 27.060.30 - Boilers and heat exchangers
• Technical Committee: TLP - Pressure vessels
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 20-Jul-2007
• Due Date: 24-Sep-2007
• Completion Date: 08-Aug-2007
• Directive: 2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Directive: 97/23/EC - Directive 97/23/EC of the European Parliament and of the Council of 29 May 1997 on the approximation of the laws of the Member States concerning pressure equipment
• Mandate: M/071 - Mandate to CEN for standardization in the field of Pressure equipment
• Ref Project: EN 12953-9:2007 - Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessories

Relations

• Revised: oSIST prEN 12953-9:2023 - Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessories
• Effective Date: 01-Jun-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 12953-9:2007
01-september-2007
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
Chaudieres a tubes de fumée - Partie 9: Exigences pour les dispositifs de limitation de la
chaudiere et de ses accessoires
Ta slovenski standard je istoveten z: EN 12953-9:2007
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
SIST EN 12953-9:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 12953-9:2007

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SIST EN 12953-9:2007
EUROPEAN STANDARD
EN 12953-9
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2007
ICS 27.060.30

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 la chaudière et de ses Begrenzungseinrichtungen an Kessel und Zubehör
accessoires
This European Standard was approved by CEN on 26 May 2007.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12953-9:2007: E
worldwide for CEN national Members.

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SIST EN 12953-9:2007
EN 12953-9:2007 (E)
Contents Page
Foreword. 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Requirements for limiter . 9
4.1 General. 9
4.2 Materials and design . 9
4.3 Electrical equipment. 10
4.4 Fault assessment. 10
4.5 Marking . 12
5 Special requirements for water level limiters .14
5.1 Components. 14
5.2 Design . 14
5.3 Floating devices. 15
5.4 Level electrode devices . 15
5.5 Examination of functional capability . 16
5.6 Fault detection . 19
6 Special requirements for pressure limiters .19
6.1 Components. 19
6.2 Additional fault assessment requirements .19
6.3 Design . 19
6.4 Electrical equipment. 20
6.5 Examination of functional capability . 20
6.6 Fault detection . 22
7 Special requirements for temperature limiters. 22
7.1 Components. 22
7.2 Design . 22
7.3 Electrical equipment. 24
7.4 Examination of functional capability . 24
8 Special requirements for flow limiters. 25
8.1 Components. 25
8.2 Design . 25
8.3 Electrical equipment. 25
8.4 Examination of functional capability . 25
Annex A (informative) Limiting device. 26
Annex B (informative) Example of an examination plan . 27
Annex C (informative) Marking of limiters . 29
Annex D (normative) Immunity against electrical and electromagnetic influences —
Requirements and testing. 32
D.1 General. 32
D.2 Immunity against mains voltage variations .32
D.3 Immunity against short-time voltage interruptions and reductions. 32
D.4 Immunity against mains frequency changes. 33
D.5 Immunity against electrostatic discharge (ESD). 33
D.6 Immunity against fast transient disturbance variables (burst). 33
D.7 Immunity against surges . 34
D.8 Immunity against high-frequency electromagnetic fields. 34
D.9 Immunity against conducted disturbances induced by high frequency fields. 35
D.10 Immunity against power frequency magnetic fields. 35
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EN 12953-9:2007 (E)
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 97/23/EC. 36
Bibliography. 37


3

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SIST EN 12953-9:2007
EN 12953-9:2007 (E)
Foreword
This document (EN 12953-9:2007) has been prepared by Technical Committee CEN/TC 269 “Shell and
water-tube boilers”, 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 January 2008 and conflicting national standards shall be withdrawn at
the latest by January 2008.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document.
The European Standard 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
CR 12953 Part 14: Guideline for the involvement of an inspection body independent of the manufacturer.
Although these Parts may be obtained separately, it should be recognised 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.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and United Kingdom.
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Introduction
The types of limiters which shall be fitted to boilers are specified in EN 12953-6 and the design of the safety
systems are specified in EN 50156-1.
A limiter (or limiting device) is one element of a shell boiler safety system. It comprises a sensor and
monitoring elements to achieve the desired level of reliability.
In order to provide the necessary safety function, for example, to cut off the heat supply to the boiler in the
event of a low water fault, the limiter is connected to other elements in the safety system such as actuators
and safety logic circuits.
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EN 12953-9:2007 (E)
1 Scope
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.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 298:2003, Automatic gas burner control systems for gas burners and gas burning appliances with or
without fans
EN 50156-1:2004, Electrical equipment for furnaces and ancillary equipment — Part 1: Requirements for
application design and installation
EN 60529:1991, Degrees of protection provided by enclosures (IP code) (IEC 60529:1989)
EN 60664-1:2003, Insulation coordination for equipment within low-voltage systems — Part 1: Principles,
requirements and tests (IEC 60664-1:1992 + A1:2000 + A2:2002)
EN 60730-1:2000, Automatic electrical controls for household and similar use — Part 1: General requirements
(IEC 60730-1:1999, modified)
EN 61000-4-2:1995, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques —
Section 2: Electrostatic discharge immunity test — Basic EMC publication (IEC 61000-4-2:1995)
EN 61000-4-3:2006, Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement techniques
— Radiated, radio-frequency, electromagnetic field immunity test (IEC 61000-4-3:2006)
EN 61000-4-4:2004, Electromagnetic compatibility (EMC) — Part 4-4: Testing and measurement techniques
— Electrical fast transient/burst immunity test (IEC 61000-4-4:2004)
EN 61000-4-5:2006, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques —
Section 5: Surge immunity test (IEC 61000-4-5:2005)
EN 61000-4-6:1996, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques —
Section 6: Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000-4-6:1996)
EN 61000-4-8:1993, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques —
Section 8: Power frequency magnetic field immunity test; basic EMC publication (IEC 61000-4-8:1993)
6

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EN 12953-9:2007 (E)
EN 61000-4-11:2004, Electromagnetic compatibility (EMC) — Part 4-11: Testing and measurement
techniques — Voltage dips, short interruptions and voltage variations immunity tests (IEC 61000-4-11:2004)
EN 61000-6-2:2005, Electromagnetic compatibility (EMC) — Part 6-2: Generic standards — Immunity for
industrial environments (IEC 61000-6-2:2005)
EN 61508-3:2001, Functional safety of electrical/electronic/programmable electronic safety-related systems —
Part 3: Software requirements (IEC 61508-3:1998 + Corrigendum 1999)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
limiter
limiting device that, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to
interrupt and lock-out the energy supply
NOTE Limiting device comprises:
 a measuring or detection function and
 an activation function for correction, or shutdown, or shutdown and lockout, and which is used to carry out
safety related functions as defined in the PED, on its own or as part of a safety (protective) system (e.g.
sensors, limiters) (see also Figure 1). If this is achieved by multi channel systems, then all items or limiters
for safety purposes are included within the safety (protective) system

Figure 1 — Protective devices and safety accessories according to Directive 97/23/EC (PED)
3.2
actuating element
component which produces changes in other electrical circuits or volume flows (e.g. fuel, air) as a result of the
effect of changes in signal
NOTE For example, a gas shut off valve is not an actuating element.
3.3
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
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3.4
self-monitoring
regular and automatic determination that all chosen components of a safety system are capable of functioning
as required
3.5
redundancy
provision of more than one device or system which, in the event of a fault, will still be provided by the
necessary facilities
3.6
diversity
provision of different means of performing the required function, e.g. other physical principles or other ways of
solving the same problem
3.7
complex electronics
assemblies which use electronic components with more than one functional output
3.8
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)
3.9
lock-out
safety shut-down condition of the limiter, such that a restart can only be accomplished by a manual reset of
the limiter or by a manual reset of the safety logic and by no other means
NOTE This will be achieved by a competent operator taking account of the physical situation
3.10
sensor
transducer which, on reaching a defined limit value, outputs a signal and/or cuts out and only reverses the
output signal in the event of a specific change in the performance quantity (e.g. pressure, temperature, flow,
level)
NOTE Sensors are used for signalling or for triggering control processes
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4 Requirements for limiter
4.1 General
4.1.1 The requirements set out below have been established to ensure uniform assessment of different
devices.
A limiter shall be such that a single fault in any related part shall not lead to a loss of the safety function. This
shall be achieved by fault avoidance techniques such as self-monitoring with redundancy, diversity or a
combination of these methods. Fault assessment for the electrical components shall be in accordance
with 4.4. The fault assessment chart, see Figure 2 shall also be applied for faults in hydraulic, pneumatic and
mechanical components.
NOTE The various elements of limiters are given in Annex A.
4.1.2 Limiters shall function independently of each other and of controls unless their safety function
cannot be affected by other such functions. Manual resetting can be realised as a part of the limiter or as a
part of the safety logic. Instructions shall be delivered together with the limiter including necessary precautions
for a safe installation of it.
4.2 Materials and design
4.2.1 The use of materials with significant differences in their electrochemical potential shall be avoided in
order to prevent corrosion which could affect the function of the limiter.
4.2.2 Care shall be taken that if magnetic materials are chosen, they do not adversely affect the working of
the limiter.
4.2.3 Parts of the limiter shall be designed to comply with the applicable European Standards.
4.2.4 Limiters shall be capable of withstanding the thermal, mechanical, chemical and electrical loads that
can occur during operation.
4.2.5 Limiters shall be designed such that changes in critical circuit component values (such as those
affecting timing) within the component manufacturer's declared worst case tolerances, including the long term
stability, shall result in the system continuing to function in accordance with this standard. Compliance shall be
checked by worst case analysis.
4.2.6 Limiters using complex electronics
For limiters using complex electronics the following requirements apply additionally:
• General
Systematic errors (built into the design) shall be avoided and random faults (component faults) shall be
controlled by techniques such as self-monitoring with redundancy, diversity or a combination of these methods.
• Fault avoidance and fault tolerance
The design of the software and hardware shall be based on the functional analysis of the limiter resulting in a
structured design explicitly incorporating the control flow, data flow and time related functions required by the
application. In the case of custom-chips special attention is required with regard to measures taken to
minimise systematic errors.
Software shall be designed using EN 61508-3 to a SIL level (Safety Integrity Level) as determined by analysis
according to EN 50156-1.
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4.3 Electrical equipment
4.3.1 All wiring and electrical equipment in connection with the limiter shall be adequately protected against
the ingress of moisture and the effect of temperature (see also [2], [3]).
4.3.2 The function of the limiter and the associated electrical circuit responsible for shutting down and
locking out the heat supply system shall not be affected by other electrical circuits in their proximity. Screened
cables shall be used where necessary (see also [2], [3]).
4.3.3 Electrical components within units directly attached to the boiler shall be capable of withstanding a
temperature environment resulting from surrounding temperatures of up to 70 °C. Components within units not
directly attached to the boiler shall be capable of withstanding an ambient temperature of up to 55 °C. Any
equipment that is in contact with parts carrying steam or hot water shall be capable of withstanding the
temperature of those parts.
4.3.4 Devices shall have, as a minimum, a protection rating to IP 54 in accordance with EN 60529. When
units are installed inside an enclosure or control box, the IP rating required for the box shall be considered
adequate.
4.3.5 All mechanical output contacts of the device shall be of the snap action type. Semi-conductor
switches shall have similar characteristics.
4.3.6 The limiter shall tolerate electrical and electromagnetical influences as defined in Annex D.
4.4 Fault assessment
4.4.1 General
The limiter, excluding the stored programme section, shall be so constructed that the fault assessment
analysis in accordance with Figure 2 results in termination. Power failure, breaks in connecting cables and
short circuits shall also be considered and included in the fault assessment analysis.
4.4.2 Fault models and exclusions
4.4.2.1 General
With fault assessment in accordance with Figure 2, it shall be assumed that certain faults do not occur. Such
assumptions are justified by describing the failure mechanism as well as by stating the conditions relating to
design, construction, environment etc. for the conductors, components and equipment.
Faults which shall be taken into account are based in EN 298:2003, Annex A with consideration of the
following faults which may be excluded without further justification:
4.4.2.2 Conductor-to-conductor short circuit fault
This fault may be excluded if:
a) cables and conductors as specified in EN 50156-1 are used;
b) components are encapsulated so that they are moisture resistant or, if they are hermetically sealed and
they are capable of withstanding the test specified in EN 50156-1;
c) clearance between live parts shall be designed according to overvoltage category III and pollution
degree 3 and the creepage distance shall be designed according to pollution degree 3 but at least for the
nominal voltage of 63 V as specified in EN 60664-1;
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d) printed conductors (tracks) shall be varnished so that they are resistant to ageing by virtue of the distance
between printed conductors being equivalent to at least the values specified in EN 60664-1:2003, Table 4
for pollution degree 1, and with a minimum nominal voltage of 32 V (minimum creepage distance of
0,14 mm).
4.4.2.3 Short circuit in wound film resistors
This fault may be excluded if the wound film resistors shall be used with a varnished or encapsulated resistive
layer and axial terminations. The possibility of condensation shall be excluded during operation. The limits, e.g.
voltage limit, power, shall not be exceeded even under worst case conditions.
4.4.2.4 Short circuit in wire-wound resistors
This fault may be excluded if the winding is a single layer winding and shall be secured by means of a glaze or
embedded in a sealing compound.
4.4.2.5 Non-opening of contact elements due to permanent welding
This fault may be excluded if contactors, relays or auxiliary switches for example, shall be protected against the
effects of short circuits by the appropriate overcurrent protective or current limiting devices. In rating the
overcurrent protective device, the nominal current of the device as stated by the manufacturer, shall be
multiplied by a safety factor of 0,6. Fault exclusion is also permissible if the prospective short circuit current is
less than the nominal current for the contact element concerned. Where contact elements are connected in
series, the contact element with the lowest overcurrent strength shall be the deciding factor.
Reed contacts shall not be used.
4.4.2.6 Mechanical failure of switching devices
This fault may be excluded if the switching devices are type tested to demonstrate they shall be still be operative
after at least 250 000 switching cycles under conditions similar to operating conditions. Contactors and relays
shall, in addition, be capable of a mechanical endurance of 3 000 000 switching cycles, except for pressure
limiters, see Table 2.
NOTE The term "conditions similar to operating conditions" covers chemical and climatic influences as well as
electrical and mechanical stresses.
4.4.2.7 Faults in components for safe isolation
Faults in components which are provided for safe isolation of electrical circuits (e.g. power circuits and telecom-
munications circuits) in accordance with EN 61140 may be excluded. These include:
a) inter-winding short circuits in transformers (e.g. primary-secondary).
Transformers shall comply with the electrical and mechanical requirements of EN 60742. In deviation
from EN 60742, for transformers with working voltages up to 200 V, insulation between windings and
insulation against the core shall be designed for a test voltage of 2 kV rms. Transformers shall as a
minimum be short-circuit proof. Displacement of windings, turns and connection lines shall be prevented,
e.g. by vacuum impregnation or encapsulation;
b) transient voltage of switching devices like relays, contactors or auxiliary contacts between contacts and
between coil and contacts.
The insulation between contacts or between coil and contact shall be designed for nominal voltages U up
b
to 200 V for a test voltage of 2 kV rms; at nominal voltages 200 V < U < 500 V for a test voltage of
b
3,75 kV rms. By special design features (e.g. caps, ribs, encapsulation, banding) at contacts and coils,
safe isolation shall also be guaranteed against faults such as spring breakage;
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EN 12953-9:2007 (E)
c) short-circuiting of isolating distances in optocouplers.
The clearance and creepage distances of the opt
...

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Shell boilers - Part 9: Requirements for limiting devices of the boiler and accessoriesMnogovodni kotli - 9. del: Zahteve za omejevalne naprave kotla in opremeChaudieres a tubes de fumée - Partie 9: Exigences pour les dispositifs de limitation de la chaudiere et de ses accessoiresGroßwasserraumkessel - Teil 9: Anforderungen an Begrenzungseinrichtungen an Kessel und ZubehörTa slovenski standard je istoveten z:EN 12953-9:2007SIST EN 12953-9:2007en,fr,de27.060.30Grelniki vode in prenosniki toploteBoilers and heat exchangersICS:SLOVENSKI
STANDARDSIST EN 12953-9:200701-september-2007







EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12953-9July 2007ICS 27.060.30 English VersionShell boilers - Part 9: Requirements for limiting devices of theboiler and accessoriesChaudières à tubes de fumée - Partie 9: Exigences pourles dispositifs de limitation de la chaudière et de sesaccessoiresGroßwasserraumkessel - Teil 9: Anforderungen anBegrenzungseinrichtungen an Kessel und ZubehörThis European Standard was approved by CEN on 26 May 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12953-9:2007: E



EN 12953-9:2007 (E) 2 Contents Page Foreword.4 1 Scope.6 2 Normative references.6 3 Terms and definitions.7 4 Requirements for limiter.9 4.1 General.9 4.2 Materials and design.9 4.3 Electrical equipment.10 4.4 Fault assessment.10 4.5 Marking.12 5 Special requirements for water level limiters.14 5.1 Components.14 5.2 Design.14 5.3 Floating devices.15 5.4 Level electrode devices.15 5.5 Examination of functional capability.16 5.6 Fault detection.19 6 Special requirements for pressure limiters.19 6.1 Components.19 6.2 Additional fault assessment requirements.19 6.3 Design.19 6.4 Electrical equipment.20 6.5 Examination of functional capability.20 6.6 Fault detection.22 7 Special requirements for temperature limiters.22 7.1 Components.22 7.2 Design.22 7.3 Electrical equipment.24 7.4 Examination of functional capability.24 8 Special requirements for flow limiters.25 8.1 Components.25 8.2 Design.25 8.3 Electrical equipment.25 8.4 Examination of functional capability.25 Annex A (informative)
Limiting device.26 Annex B (informative)
Example of an examination plan.27 Annex C (informative)
Marking of limiters.29 Annex D (normative)
Immunity against electrical and electromagnetic influences —
Requirements and testing.32 D.1 General.32 D.2 Immunity against mains voltage variations.32 D.3 Immunity against short-time voltage interruptions and reductions.32 D.4 Immunity against mains frequency changes.33 D.5 Immunity against electrostatic discharge (ESD).33 D.6 Immunity against fast transient disturbance variables (burst).33 D.7 Immunity against surges.34 D.8 Immunity against high-frequency electromagnetic fields.34 D.9 Immunity against conducted disturbances induced by high frequency fields.35 D.10 Immunity against power frequency magnetic fields.35



EN 12953-9:2007 (E) 3 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 97/23/EC.36 Bibliography.37



EN 12953-9:2007 (E) 4 Foreword This document (EN 12953-9:2007) has been prepared by Technical Committee CEN/TC 269 “Shell and water-tube boilers”, 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 January 2008 and conflicting national standards shall be withdrawn at the latest by January 2008. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document. The European Standard 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 CR 12953 Part 14: Guideline for the involvement of an inspection body independent of the manufacturer. Although these Parts may be obtained separately, it should be recognised 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. 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.



EN 12953-9:2007 (E) 5 Introduction The types of limiters which shall be fitted to boilers are specified in EN 12953-6 and the design of the safety systems are specified in EN 50156-1. A limiter (or limiting device) is one element of a shell boiler safety system. It comprises a sensor and monitoring elements to achieve the desired level of reliability. In order to provide the necessary safety function, for example, to cut off the heat supply to the boiler in the event of a low water fault, the limiter is connected to other elements in the safety system such as actuators and safety logic circuits.



EN 12953-9:2007 (E) 6 1 Scope 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. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 298:2003, Automatic gas burner control systems for gas burners and gas burning appliances with or without fans EN 50156-1:2004, Electrical equipment for furnaces and ancillary equipment — Part 1: Requirements for application design and installation EN 60529:1991, Degrees of protection provided by enclosures (IP code) (IEC 60529:1989) EN 60664-1:2003, Insulation coordination for equipment within low-voltage systems — Part 1: Principles, requirements and tests (IEC 60664-1:1992 + A1:2000 + A2:2002) EN 60730-1:2000, Automatic electrical controls for household and similar use — Part 1: General requirements (IEC 60730-1:1999, modified) EN 61000-4-2:1995, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques — Section 2: Electrostatic discharge immunity test — Basic EMC publication (IEC 61000-4-2:1995) EN 61000-4-3:2006, Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement techniques — Radiated, radio-frequency, electromagnetic field immunity test (IEC 61000-4-3:2006) EN 61000-4-4:2004, Electromagnetic compatibility (EMC) — Part 4-4: Testing and measurement techniques — Electrical fast transient/burst immunity test (IEC 61000-4-4:2004) EN 61000-4-5:2006, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques — Section 5: Surge immunity test (IEC 61000-4-5:2005) EN 61000-4-6:1996, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques — Section 6: Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000-4-6:1996) EN 61000-4-8:1993, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques — Section 8: Power frequency magnetic field immunity test; basic EMC publication (IEC 61000-4-8:1993)



EN 12953-9:2007 (E) 7 EN 61000-4-11:2004, Electromagnetic compatibility (EMC) — Part 4-11: Testing and measurement techniques — Voltage dips, short interruptions and voltage variations immunity tests (IEC 61000-4-11:2004) EN 61000-6-2:2005, Electromagnetic compatibility (EMC) — Part 6-2: Generic standards — Immunity for industrial environments (IEC 61000-6-2:2005) EN 61508-3:2001, Functional safety of electrical/electronic/programmable electronic safety-related systems — Part 3: Software requirements (IEC 61508-3:1998 + Corrigendum 1999) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 limiter limiting device that, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to interrupt and lock-out the energy supply NOTE Limiting device comprises:  a measuring or detection function and  an activation function for correction, or shutdown, or shutdown and lockout, and which is used to carry out safety related functions as defined in the PED, on its own or as part of a safety (protective) system (e.g. sensors, limiters) (see also Figure 1). If this is achieved by multi channel systems, then all items or limiters for safety purposes are included within the safety (protective) system
Figure 1 — Protective devices and safety accessories according to Directive 97/23/EC (PED) 3.2 actuating element component which produces changes in other electrical circuits or volume flows (e.g. fuel, air) as a result of the effect of changes in signal NOTE For example, a gas shut off valve is not an actuating element. 3.3 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



EN 12953-9:2007 (E) 8 3.4 self-monitoring regular and automatic determination that all chosen components of a safety system are capable of functioning as required 3.5 redundancy provision of more than one device or system which, in the event of a fault, will still be provided by the necessary facilities 3.6 diversity provision of different means of performing the required function, e.g. other physical principles or other ways of solving the same problem 3.7 complex electronics assemblies which use electronic components with more than one functional output 3.8 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) 3.9 lock-out safety shut-down condition of the limiter, such that a restart can only be accomplished by a manual reset of the limiter or by a manual reset of the safety logic and by no other means NOTE This will be achieved by a competent operator taking account of the physical situation 3.10 sensor transducer which, on reaching a defined limit value, outputs a signal and/or cuts out and only reverses the output signal in the event of a specific change in the performance quantity (e.g. pressure, temperature, flow, level) NOTE Sensors are used for signalling or for triggering control processes



EN 12953-9:2007 (E) 9 4 Requirements for limiter 4.1 General 4.1.1 The requirements set out below have been established to ensure uniform assessment of different devices. A limiter shall be such that a single fault in any related part shall not lead to a loss of the safety function. This shall be achieved by fault avoidance techniques such as self-monitoring with redundancy, diversity or a combination of these methods. Fault assessment for the electrical components shall be in accordance with 4.4. The fault assessment chart, see Figure 2 shall also be applied for faults in hydraulic, pneumatic and mechanical components. NOTE The various elements of limiters are given in Annex A. 4.1.2 Limiters shall function independently of each other and of controls unless their safety function cannot be affected by other such functions. Manual resetting can be realised as a part of the limiter or as a part of the safety logic. Instructions shall be delivered together with the limiter including necessary precautions for a safe installation of it. 4.2 Materials and design 4.2.1 The use of materials with significant differences in their electrochemical potential shall be avoided in order to prevent corrosion which could affect the function of the limiter. 4.2.2 Care shall be taken that if magnetic materials are chosen, they do not adversely affect the working of the limiter. 4.2.3 Parts of the limiter shall be designed to comply with the applicable European Standards. 4.2.4 Limiters shall be capable of withstanding the thermal, mechanical, chemical and electrical loads that can occur during operation. 4.2.5 Limiters shall be designed such that changes in critical circuit component values (such as those
affecting timing) within the component manufacturer's declared worst case tolerances, including the long term stability, shall result in the system continuing to function in accordance with this standard. Compliance shall be checked by worst case analysis. 4.2.6 Limiters using complex electronics For limiters using complex electronics the following requirements apply additionally: • General Systematic errors (built into the design) shall be avoided and random faults (component faults) shall be controlled by techniques such as self-monitoring with redundancy, diversity or a combination of these methods. • Fault avoidance and fault tolerance The design of the software and hardware shall be based on the functional analysis of the limiter resulting in a structured design explicitly incorporating the control flow, data flow and time related functions required by the application. In the case of custom-chips special attention is required with regard to measures taken to minimise systematic errors. Software shall be designed using EN 61508-3 to a SIL level (Safety Integrity Level) as determined by analysis according to EN 50156-1.



EN 12953-9:2007 (E) 10 4.3 Electrical equipment 4.3.1 All wiring and electrical equipment in connection with the limiter shall be adequately protected against the ingress of moisture and the effect of temperature (see also [2], [3]). 4.3.2 The function of the limiter and the associated electrical circuit responsible for shutting down and locking out the heat supply system shall not be affected by other electrical circuits in their proximity. Screened cables shall be used where necessary (see also [2], [3]). 4.3.3 Electrical components within units directly attached to the boiler shall be capable of withstanding a
temperature environment resulting from surrounding temperatures of up to 70 °C. Components within units not
directly attached to the boiler shall be capable of withstanding an ambient temperature of up to 55 °C. Any equipment that is in contact with parts carrying steam or hot water shall be capable of withstanding the temperature of those parts. 4.3.4 Devices shall have, as a minimum, a protection rating to IP 54 in accordance with EN 60529. When units are installed inside an enclosure or control box, the IP rating required for the box shall be considered adequate. 4.3.5 All mechanical output contacts of the device shall be of the snap action type. Semi-conductor switches shall have similar characteristics. 4.3.6 The limiter shall tolerate electrical and electromagnetical influences as defined in Annex D. 4.4 Fault assessment 4.4.1 General The limiter, excluding the stored programme section, shall be so constructed that the fault assessment analysis in accordance with Figure 2 results in termination. Power failure, breaks in connecting cables and short circuits shall also be considered and included in the fault assessment analysis. 4.4.2 Fault models and exclusions 4.4.2.1 General With fault assessment in accordance with Figure 2, it shall be assumed that certain faults do not occur. Such assumptions are justified by describing the failure mechanism as well as by stating the conditions relating to design, construction, environment etc. for the conductors, components and equipment. Faults which shall be taken into account are based in EN 298:2003, Annex A with consideration of the following faults which may be excluded without further justification: 4.4.2.2 Conductor-to-conductor short circuit fault This fault may be excluded if: a) cables and conductors as specified in EN 50156-1 are used; b) components are encapsulated so that they are moisture resistant or, if they are hermetically sealed and they are capable of withstanding the test specified in EN 50156-1; c) clearance between live parts shall be designed according to overvoltage category III and pollution degree 3 and the creepage distance shall be designed according to pollution degree 3 but at least for the nominal voltage of 63 V as specified in EN 60664-1;



EN 12953-9:2007 (E) 11 d) printed conductors (tracks) shall be varnished so that they are resistant to ageing by virtue of the distance between printed conductors being equivalent to at least the values specified in EN 60664-1:2003, Table 4 for pollution degree 1, and with a minimum nominal voltage of 32 V (minimum creepage distance of 0,14 mm). 4.4.2.3 Short circuit in wound film resistors This fault may be excluded if the wound film resistors shall be used with a varnished or encapsulated resistive layer and axial terminations. The possibility of condensation shall be excluded during operation. The limits, e.g. voltage limit, power, shall not be exceeded even under worst case conditions. 4.4.2.4 Short circuit in wire-wound resistors This fault may be excluded if the winding is a single layer winding and shall be secured by means of a glaze or embedded in a sealing compound. 4.4.2.5 Non-opening of contact elements due to permanent welding This fault may be excluded if contactors, relays or auxiliary switches for example, shall be protected against the effects of short circuits by the appropriate overcurrent protective or current limiting devices. In rating the overcurrent protective device, the nominal current of the device as stated by the manufacturer, shall be multiplied by a safety factor of 0,6. Fault exclusion is also permissible if the prospective short circuit current is less than the nominal current for the contact element concerned. Where contact elements are connected in series, the contact element with the lowest overcurrent strength shall be the deciding factor. Reed contacts shall not be used. 4.4.2.6 Mechanical failure of switching devices This fault may be excluded if the switching devices are type tested to demonstrate they shall be still be operative after at least 250 000 switching cycles under conditions similar to operating conditions. Contactors and relays shall, in addition, be capable of a mechanical endurance of 3 000 000 switching cycles, except for pressure limiters, see Table 2. NOTE The term "conditions similar to operating conditions" covers chemical and climatic influences as well as electrical and mechanical stresses. 4.4.2.7 Faults in components for safe isolation Faults in components which are provided for safe isolation of electrical circuits (e.g. power circuits and telecom-munications circuits) in accordance with EN 61140 may be excluded. These include: a) inter-winding short circuits in transformers (e.g. primary-secondary). Transformers shall comply with the electrical and mechanical requirements of EN 60742. In deviation from EN 60742, for transformers with working voltages up to 200 V, insulation between windings and insulation against the core shall be designed for a test voltage of 2 kV rms. Transformers shall as a minimum be short-circuit proof. Displacement of windings, turns and connection lines shall be prevented, e.g. by vacuum impregnation or encapsulation; b) transient voltage of switching devices like relays, contactors or auxiliary contacts between contacts and
between coil and contacts. The insulation between contacts or between coil and contact shall be designed for nominal voltages Ub up to 200 V for a test voltage of 2 kV rms; at nominal voltages 200 V < Ub < 500 V for a test voltage of 3,75 kV rms. By special design features (e.g. caps, ribs, encapsulation, banding) at contacts and coils, safe isolation shall also be guaranteed against faults such as spring breakage;



EN 12953-9:2007 (E) 12 c) short-circuiting of isolating distances in optocouplers. The clearance and creepage distances of the optocoupler in its installed position shall fulfil the relevant conditions of EN 60664-1:2003, 3.1 and 3.2. 4.5 Marking The limiters shall be marked with the following:  manufacturer´s name and/or trademark;  year of manufacture;  maximum/minimum allowable design limits;  unique type reference. NOTE Other markings may be added by the limiter manufacturer or placed in the operating instructions, see
Annex C.



EN 12953-9:2007 (E) 13
Key 1 reassessment Figure 2 — Fault assessment chart for limiters excluding the stored programme section



EN 12953-9:2007 (E) 14 5 Special requirements for water level limiters 5.1 Components This limiter shall consist of one or more units needed to provide the necessary safety function. The limiter shall comprise of the following elements where applicable: sensor, protection tube or external chamber (see NOTE), timing element, testing devices and other associated equipment up to the terminals of the switching output contacts as shown in Annex A. NOTE Protection tubes and external chambers may be considered to be part of the boiler and in these cases it will be necessary for the limiter manufacturer and the boiler manufacturer to agree on the design and manufacturing requirements to ensure that the limiter system performs as intended. Examples of water level sensor are: float level switch, electrode probe, conductivity sensor. 5.2 Design 5.2.1 General Chambers, connecting pipes and protection
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