SIST EN 50156-1:2015

SLOVENSKI STANDARD
01-september-2015
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SIST EN 50156-1:2006
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Electrical equipment for furnaces and ancillary equipment - Part 1: Requirements for
application design and installation
Elektrische Ausrüstung von Feuerungsanlagen und zugehörige Einrichtungen - Teil 1:
Bestimmungen für die Anwendungsplanung und Errichtung
Equipements électriques d'installation de chaudière - Partie 1: Règles pour la
conception, pour l'application et l'installation
Ta slovenski standard je istoveten z: EN 50156-1:2015
ICS:
27.060.01 Gorilniki in grelniki vode na Burners and boilers in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50156-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2015
ICS 27.060.01 Supersedes EN 50156-1:2004
English Version
Electrical equipment for furnaces and ancillary equipment - Part
1: Requirements for application design and installation
Equipements électriques d'installation de chaudière - Partie Elektrische Ausrüstung von Feuerungsanlagen und
1: Règles pour la conception, pour l'application et zugehörige Einrichtungen - Teil 1: Bestimmungen für die
l'installation Anwendungsplanung und Errichtung
This European Standard was approved by CENELEC on 2015-01-26. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50156-1:2015 E
Contents
European foreword . 6
Introduction . 7
1 Scope . 9
2 Normative references . 10
3 Terms and definitions . 11
4 General requirements . 19
4.1 General considerations . 19
4.2 Environmental requirements . 20
4.2.1 General . 20
4.2.2 Environmental and operating conditions . 20
4.2.3 Electromagnetic compatibility . 20
4.2.4 Ambient temperature . 21
4.2.5 Humidity . 21
4.2.6 Contamination . 22
4.2.7 Vibration and shock. 22
4.2.8 Equipment used in flammable atmospheres . 22
4.3 Power supply . 22
4.3.1 General . 22
4.3.2 Power stations . 22
5 Incoming supply connections and devices for disconnecting and emergency stop . 22
5.1 Incoming supply and equipment connections . 22
5.1.1 Types of connection . 22
5.1.2 Terminations . 23
5.2 Devices for disconnecting power supplies . 24
5.2.1 General . 24
5.2.2 Disconnecting switch . 25
5.2.3 Excluded circuits . 25
5.3 Emergency stop . 26
5.3.1 General . 26
5.3.2 Emergency stop device for furnaces in heating installations . 26
5.3.3 Emergency stop device for other furnaces, e.g. steam boilers . 26
5.3.4 Application as isolating switch . 26
6 Protection against electric shock . 26
6.1 Protection against direct contact . 26
6.2 Protection against indirect contact . 27
7 Environmental protection of the equipment. 27
7.1 Protection against ingress of solid foreign bodies. 27
7.2 Protection against water . 27
8 Equipotential bonding . 27
8.1 General . 27
8.2 Equipotential bonding as a protective measure in case of indirect contact . 27
8.3 Equipotential bonding for the purpose of lightning protection . 28
8.4 Functional equipotential bonding . 28
9 Auxiliary circuits . 29
9.1 Supply to auxiliary circuits . 29
9.1.1 Supply from 3-phase or a.c. systems . 29
9.1.2 Supply from d.c. mains . 29
9.1.3 Auxiliary circuits connected between the line conductors . 30
9.2 Voltage for auxiliary circuits . 30
9.2.1 Operating voltage of auxiliary circuits . 30
9.2.2 Preferred nominal voltages . 30
9.3 Connection to the protective conductor . 30
9.4 Overcurrent protection of auxiliary circuits . 30
9.4.1 Rating of overcurrent protective devices . 30
9.4.2 Overcurrent protection of auxiliary circuits connected to the protective
conductor . 31
9.4.3 Overcurrent protection of auxiliary circuit with the middle conductor
connected to the protective conductor . 31
9.4.4 Overcurrent protection of auxiliary circuits with no electrical connection to
the protective conductor . 31
9.4.5 Overcurrent protection of control system supply transformers . 31
9.4.6 Rating and setting of overcurrent protection . 31
9.5 Measures to prevent danger from short circuits to exposed conductive parts or
earth . 31
9.6 Influence of capacitance and leakage resistance . 32
10 Additional requirements for the application of a safety-related system . 32
10.1 General safety requirements . 32
10.1.1 Safety lifecycle requirements for a safety-related system . 32
10.1.2 Planning . 34
10.2 Concept and scope definition . 37
10.3 Hazard and risk analysis . 38
10.4 Safety requirements allocation . 39
10.5 Design . 40
10.5.1 General requirements. 40
10.5.2 Design of the safety-related system . 41
10.5.3 Measures to avoid faults . 46
10.5.4 Consideration of times . 47
10.5.5 Hardware design . 47
10.5.6 Plant specific application software. 52
10.6 Installation and commissioning . 55
10.7 Safety validation . 55
10.7.1 System integration of hardware and software . 55
10.7.2 Fault assessment for the system integration of hardware and software . 56
10.7.3 Type approval . 57
10.7.4 Plant-specific test . 57
10.8 Operation and maintenance . 57
10.9 Modification and retrofit . 58
10.9.1 General . 58
10.9.2 Measures against unauthorised changes or overriding . 58
11 Electrical equipment . 59
11.1 General requirements . 59
11.2 Creepage distances and clearances . 59
11.3 Motors . 59
11.4 Transformers . 59
11.5 Switching devices . 60
11.6 Operator control devices . 60
11.7 Immersion electrodes . 60
11.8 Trace heating systems . 60
12 Cables and cords . 60
12.1 General requirements . 60
12.2 Insulation . 61
12.3 Current-carrying capacity . 61
12.4 Conductors of separate circuits . 61
13 Warning signs and item designation . 62
13.1 Warning signs . 62
13.2 Functional identification . 62
13.3 Item designations . 62
14 Technical documentation . 62
14.1 General . 62
14.2 Documentation describing functions and connections . 63
14.2.1 General . 63
14.2.2 Documentation describing functions . 63
14.2.3 Documentation describing connections . 63
14.2.4 Documentation describing the process . 63
14.2.5 Documentation of the risk assessment . 63
14.3 Documents for type approved components . 64
14.4 Documentation of the application software . 64
Annex A (informative) Configurations of programmable safety devices (PSD) with reference
to EN 61508 . 65
A.1 Configuration 1oo1 . 66
A.2 Configuration 1oo1D . 66
A.3 Configuration 1oo2 . 67
A.4 Configuration 1oo2D . 68
A.5 Configuration 2oo3 . 69
A.6 Configuration 2oo3D . 70
Annex B (informative) Lifecycle of programmable safety device . 72
Annex C (informative) Management of functional safety . 73
Annex D (informative) Examples of determining the safety integrity level SIL using the risk
graph method . 74
D.1 General . 74
D.2 Risk parameter C (Consequences of the hazardous event) . 74
D.3 Risk parameter F (Frequence and duration of the time spent in the hazard area) . 74
D.4 Risk parameter P (Possibility of preventing the hazardous event) . 74
D.5 Risk parameter W (Likelihood of occurrence of the hazardous event) . 74
Bibliography . 76
Figure 1 – Example of the functionality of a furnace with ancillary equipment, heated
systems and relationship to control system and safety related system . 8
Figure 2 – Types of faults to be considered . 14
Figure 3 – Causes of faults to be considered . 14
Figure 4 – Definition and components of a safety-related system . 17
Figure 5 – Software . 18
Figure 6 – Example of power supply, switching, isolating devices and other electrical
components of a furnace . 24
Figure 7 – Supply from two d.c. sources . 29
Figure 8 – Safety lifecycle model for application, design and installation of a safety-related
system (Clause 10) . 33
Figure 9 – Rating of safety integrity levels for furnaces . 39
Figure 10 – Choice of design principals . 41
Figure 11 – Fault assessment for the hard-wired section of a safety-related system . 42
Figure 12 – Proof of safety against failures and malfunctions of the programmable safety
device of the safety-related system . 43
Figure 13 – Proof of safety of software . 44
Figure 14 – Consideration of fault tolerance time and safety time for furnaces . 47
Figure 15 – Examples for wiring of fuel shut down with hardware diversity of the
disconnecting devices . 48
Figure 16 – Example for wiring of fuel shut down with diverse functionality of the
disconnecting devices . 49
Figure A.1 - Explanation of symbols . 65
Figure A.2 . 66
Figure A.3 . 67
Figure A.4 . 68
Figure A.5 . 69
Figure A.6 . 70
Figure A.7 . 71
Figure B.1 . 72
Table 1 – Consideration of different field equipment (sensors and actuating elements)
configurations if subsystems or devices are used based on product standards without
data in accordance with EN 61508 or only based on the fault assessment in accordance
on the Figures 11, 12 or 13 . 45
Table 2 – Allocation of fault exclusions to safety integrity levels . 50
Table A.1 . 66
Table A.2 . 67
Table A.3 . 68
Table A.4 . 69
Table A.5 . 70
Table A.6 . 71

European foreword
This document (EN 50156-1:2015) has been prepared by CLC/BTTF 132-2 “Revision of EN 50156 “Electrical
equipment for furnaces and ancillary equipment” in cooperation with the National Committee DKE/K 232.
The following dates are fixed:
• latest date by which this document has to be (dop) 2016-01-26
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2018-01-26
conflicting with this document have to
be withdrawn
This document supersedes EN 50156-1:2004.
• harmonization of the definitions to the new version of EN 61508;
• check and updating of the normative references;
• elimination of all normative references to the machinery directive 2006/42/EC;
• alignment to the requirements for safety related system to EN 12952 and EN 12953;
• modifications in Clause 10.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.
This standard covers the Principle Elements of the Safety Objectives for Electrical Equipment Designed for
Use within Certain Voltage Limits (LVD - 2006/95/EC).
Requirements of this standard covers the essential safety requirements for limiting devices in the scope of
this standard which are safety accessories in the sense of pressure equipment directive 97/23/EG, which are
classified in the category II and higher.
This standard is the first part of a series of European standards which specify the requirements for
equipment of safety functions for furnaces, especially safety related system to protect personnel, the furnace
with ancillary equipment against hazards related to heat generation, the heated system and to operate
reliably during normal conditions, and abnormal conditions which can be foreseen.
This European Standard has been prepared by the German National Committee with the participation of
experts of other National Committees on the basis of CLC/BT(DE/NOT)140. It is divided into 3 parts under
the generic title “Electrical equipment for furnaces and ancillary equipment”:
• Part 1: Requirements for application design and installation;
• Part 2: Requirements for design, development and type approval of safety-relevant equipment;
• Part 3: Requirements for plant-specific tests of safety-relevant equipment.
This European Standard is based on the EN 61508:2010 “Functional safety of
electrical/electronic/programmable electronic safety-related systems”, Parts 1 to 7 as a basic safety
standard.
Introduction
This part of the European Standard EN 50156 specifies the requirements and recommendations for the
application design and installation of electrical and control equipment for furnaces and ancillary equipment
and for the systems heated by the thermal energy released in the furnace to ensure:
• safety of personnel, property and the environment;
• consistency of proper function.
The operating conditions of the furnace, the hazards of combustion and the safety of heated systems are
considered.
A safety-related system consisting of safety devices for:
• monitoring of flames and other safety conditions of the firing;
• interrupting the flow of fuel to the furnace;
• ventilating the body of the furnace and the flue gas ducts;
• monitoring of the safety condition of the heated systems (e.g. water level limiter in steam boilers);
may be necessary to ensure proper ignition and combustion of fuel and to avoid the development, existence
and/or ignition of an explosive mixture of fuel and air, and also to avoid damage to the heated systems (see
3.25).
The rating of necessary safety integrity levels is based on EN 61508-1.
Figure 1 is provided as an aid to understanding the relationship between the various elements of furnaces
and their ancillary equipment, the heated systems, the control system and the safety-related systems.
Figure 1 – Example of the functionality of a furnace with ancillary equipment, heated systems and
relationship to control system and safety related system
1 Scope
This European Standard applies to the application design and installation of electrical equipment, control
circuits and safety-related systems for furnaces which are operated with solid, liquid or gaseous fuels and
their ancillary equipment. It specifies requirements to meet the operating conditions of furnaces, to reduce
the hazards of combustion and to protect the heated systems from damage e.g. by overheating.
Such furnaces and the electrical equipment may be part by way of example of the following plant:
a) water heating systems;
b) steam boiler installations (steam and hot-water boilers) and heat recovery steam boilers;
NOTE 1 The requirements of this standard apply according to the electrical equipment of electrically heated steam
boilers.
NOTE 2 Seagoing vessels and offshore facilities are governed by International Maritime Law and as such are not
within the scope of this standard. These requirements may be used for such facilities.
c) warm air heaters;
d) hot-gas heaters;
e) heat exchanger systems;
f) combustion chambers of stationary turbines;
g) as long as no other standard is applicable for combined heat and power stations, we recommend the
use of the requirements of this standard;
h) This standard may also be used as reference for electrical equipment requirements for thermo-
processing equipment.
The requirements in this standard are not applicable to electrical equipment for:
i) non-electrically heated appliances and burner control systems for household and similar purposes;
j) furnaces using technologies for the direct conversion of heat into electrical energy;
k) combustion chambers of non-stationary prime movers and turbines;
l) central oil supply systems for individual heating appliances;
m) furnaces using solid fuels for heating purposes for household use with a nominal thermal output up to
1 MW;
n) furnaces which are used to heat process fluids and gasses in chemical plant.
This European Standard may be used as a basis for the requirements placed on electrical equipment for
furnaces, which are excluded from its field of application.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 12952-7:2012, Water-tube boilers and auxiliary installations - Part 7: Requirements for equipment for the
boiler
EN 12952-8:2002, Water-tube boilers and auxiliary installations - Part 8: Requirements for firing systems for
liquid and gaseous fuels for the boiler
EN 12952-9:2002, Water-tube boilers and auxiliary installations - Part 9: Requirements for firing systems for
pulverized solid fuels for the boiler
EN 12952-16:2002, Water-tube boilers and auxiliary installations - Part 16: Requirements for grate and
fluidized-bed firing systems for solid fuels for the boiler
EN 12953-6:2011, Shell Boilers - Part 6: Requirements for equipment for the boiler
EN 12953-7:2002, Shell boilers - Part 7 : Requirements for firing systems for liquid and gaseous fuels for the
boilers
EN 12953-12:2003, Shell boilers - Part 12: Requirements for grate firing systems for solid fuels for the boiler
EN 55011:2009, Industrial, scientific and medical equipment - Radio-frequency disturbance characteristics -
Limits and methods of measurement (CISPR 11:2009, mod.)
EN 55022:2010, Information technology equipment - Radio disturbance characteristics - Limits and methods
of measurement (CISPR 22:2008, mod.)
EN 60034 all parts, Rotating electrical machines (IEC 60034-1, all parts)
EN 60309-1:1999, Plugs, socket-outlets and couplers for industrial purposes - Part 1: General requirements
(IEC 60309-1:1999)
EN 60332-1-1, Tests on electric and optical fibre cables under fire conditions - Part 1-1: Test for vertical
flame propagation for a single insulated wire or cable - Apparatus
EN 60332-2-1, Tests on electric and optical fibre cables under fire conditions - Part 2-1: Test for vertical
flame propagation for a single small insulated wire or cable - Apparatus
EN 60445:2010 , Basic and safety principles for man-machine interface, marking and identification -
Identification of equipment terminals, conductor terminations and conductors (IEC 60445:2010)
EN 60529:1991, Degrees of protection provided by enclosures (IP Code) (IEC 60529:1989)
EN 60654-3:1997, Operating conditions for industrial-process measurement and control equipment - Part 3:
Mechanical influences (IEC 60654-3:1983)
EN 60664-1:2007, Insulation coordination for equipment within low-voltage systems - Part 1: Principles,
requirements and tests (IEC 60664-1:2007)
EN 60947-2:2006, Low-voltage switch gear and control gear – Part 2: Circuit-breakers (IEC 60947-2:2006)
EN 60947-3:2009, Low-voltage switchgear and controlgear - Part 3: Switches, disconnectors, switch-
disconnectors and fuse-combination units (IEC 60947-3:2008)
EN 60947-4-1:2010, Low-voltage switchgear and controlgear - Part 4-1: Contactors and motor-starters -
Electromechanical contactors and motor-starters (IEC 60947-4-1:2009)
EN 60947-5-1:2004, Low-voltage switchgear and controlgear - Part 5-1: Control circuit devices and switching
elements - Electromechanical control circuit devices (IEC 60947-5-1:2003)
EN 61000-4, all parts, Electromagnetic compatibility (EMC) (IEC 61000-4, all parts)
FprEN 61000-6-7:2014, Electromagnetic compatibility (EMC) - Part 6-7: Generic standards - Immunity
requirements for equipment intended to perform functions in a safety-related system (functional safety) in
industrial locations (IEC 61000-4-7:201X)
EN 61082-1:2006, Preparation of documents used in electrotechnology - Part 1: Rules (IEC 61082-1:2006)
EN 61508-1:2010, Functional safety of electrical/electronic/programmable electronic safety-related systems -
Part 1: General requirements (IEC 61508-1:2010)
EN 61508-2:2010, Functional safety of electrical/electronic/programmable electronic safety-related systems -
Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems (IEC 61508-
2:2010)
EN 61508-6:2010, Functional safety of electrical/electronic/programmable electronic safety-related systems -
Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3 (IEC 61508-6:2010)
EN 61558-1:2005, Safety of power transformers, power supplies, reactors and similar products - Part 1:
General requirements and tests (IEC 61558-1:2005)
EN 61810-1:2008, Electromechanical elementary relays - Part 1: General requirements (IEC 61810-1:2008)
HD 60364-4 (all parts), Low-voltage electrical installations – Part 4: Protection for safety (IEC 60364-4, all
parts)
HD 60364-4-41:2007, Low-voltage electrical installations – Part 4-41: Protection for safety – Protection
against electric shock (IEC 60364-4-41:2005, modified)
EN 81346-1, Industrial systems, installations and equipment and industrial products - Structuring principles
and reference designations - Part 1: Basic rules (IEC 81346-1)
IEC 60417, Graphical symbols for use on equipment (IEC 60417 all parts)
IEC 60536-2:1992, Classification of electrical and electronic equipment with regard to protection against
electric shock – Part 2: Guide to requirements for protection against electric shock
IEC 60617, Graphical symbols for diagrams
ISO 3864, Safety colours and safety signs
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
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 1 to entry: Examples are valves, switches and motors including their common auxiliaries, also for example solenoid
valve with magnetic actuation and final control element for direct process control
3.2
auxiliary circuit
electrical circuit for ancillary functions, e.g. control circuits (command initiation, interlocking operation),
signalling and measuring circuits
3.3
certificate of conformity
declarations that the equipment is in accordance with the relevant standard (see 10.7.3)
Note 1 to entry: In some legislation these declarations are only accepted from independent assessors depending on
the required safety integrity level.
3.4
component
constituent part of electrical devices or subsystems, usually specified by function, but used in various
applications. These are elements or components in the sense of EN 61508-4. Examples include resistors,
capacitors, transistors, integrated circuits, printed-circuit boards
Note 1 to entry: A component is the smallest element a circuit can be subdivided into. If a component has to be broken
down it loses its physical characteristics and/or does not conform to specifications.
Note 2 to entry: An element may comprise hardware and/or software.
3.5
proven in use
demonstration, based on an analysis of operational experience for specific configuration, an element that
likelihood of dangerous systematic faults is low enough so that every safety function that uses the element
achieves its required safety integrity level
3.6
continuous operation
operation can be maintained for longer than 24 h without interruption
3.7
control circuit
electrical circuit used for the operational control and the protection of the furnace and of the power circuits
3.8
control device
device connected into the control circuit and used for controlling the operation of the furnace. For example, a
manually operated switch, a limit transducer, or a valve
3.9
current limiting
limiting of electric current to a predetermined maximum value for the defined operation by means of a
suitable arrangement of components in the circuit
3.10
Diagnostic Coverage
DC
proportion of all hardware faults which are detected by the online diagnostics embedded in the safety-related
system
Note 1 to entry: To determine the DC a fault model should be used which is sufficient for the concerned technology.
3.11
diverse programs (software)
programs or program sections which represent different solutions to an identical task which were either
written (independently) by various persons or take different approaches to problems from the outset to
achieve the same result (design diversity)
3.12
electrical equipment
equipment for furnaces includes all electrical equipment for the fields of application mentioned in Clause 1
3.13
emergency stop device
manually operated switch which can be used to shut down the furnace and its associated equipment in the
event of danger. The emergency stop device shall prevent fuel flow and electrical preheating
Note 1 to entry: In EN 12952–8 and EN 12952–9 the emergency stop is defined as master fuel trip (MFT).
3.14
external diagnostic
ED
measures to detect failures, particularly passive failures, where additional devices, which do not form part of
the programmable controller or one of its channels, are used to test the function of particular sections or the
entire programmable controller. The external diagnostic may be performed by another channel in the case of
a multi-channel configuration
3.15
external influences
influences from the environment which could bring about a failure or malfunction of the function
Note 1 to entry: The following are examples of external influences on electrical systems:
a) Power failure and return of power, over-voltage and under-voltage, short-power interruptions (<0,5 s).
b) Electromagnetic and electrical disturbances, such as inductive or capacitive interference or leakage currents
through resistive connections.
c) For microelectronic components, ionising radiation.
3.16
Failure
F
termination of the ability of an item to perform required function
Note 1 to entry: After failure, the item has a fault.
Note 2 to entry: „Failure“ is an event, as distinguished from „fault“ which is a state.
Note 3 to entry: This concept as defined does not apply to items consisting of software only.
[SOURCE: IEC 60050-191:1990, definition 191-04-01]
3.17
failure mechanism
physical or chemical process which causes an assembly to fail. It may also define how the assembly fails,
e.g. fail to safety. In doing so it may be possible to detect a failure tendency direction
3.18
fault
state of an item characterised by inability to perform a required function, excluding the inability during
preventative maintenance or other planned actions, or due to lack of external resources e.g. loss of power
supplied (see Figures 2 and 3)
Note 1 to entry: A fault is often the result of a failure of the item itself, but may exist without prior failure (191–05–01 of
IEC 60050–191:1990).
fault
hardware fault software fault
(system. or random) (allways systematic)
Other software fault software fault, which causes
shut down or malfunction
Figure 2 – Types of faults to be considered

fault
systematic fault random fault
fault caused by
environment
syst. HW syst. SW EMC climatic other HW sporadic HW
fault fault influences failure, faults
(e.g. permanent (malfunction)
mechan.,
chem.)
Figure 3 – Causes of faults to be considered
3.19
fault exclusion
exclusion of a theoretically possible fault whose occurrence, in the light of practical experience, or under the
given physical conditions is so unlikely, that it needs not to be taken into account
3.20
fault tolerance time
time between the occurrence of an unsafe condition (caused by the process itself or due to equipment
failure) and the point when the process changes into critical operation, which would result in an hazardous
event in the absence of any safety-related systems
3.21
flame monitoring device or unit
safety device which is triggered by the presence or absence of flame and gives an appropriate signal to the
protective equipment
3.22
function test
complete test of an individual safety-related function. This includes testing as to whether the safety-related
system (sensors, protective equipment and actuating elements) is acting correctly when a process parameter
is changed to ensure correct operation of the safety-related function
Note 1 to entry: Function tests of the complete safety-related functions may be carried out by overlapping partial tests.
3.23
furnace
structure within which heat is generated to a controlled temperature by combustion of fuel
Note 1 to entry: The English term „furnace“ includes structures within which heat is generated by electricity and other
forms of energy. This standard also applies to the electrical equipment of electrically heated or heat recovery steam
boilers.
3.24
furnace and ancillary equipment
this includes all the equipment for the burning of fuels, for example, equipment for the storage, preparation
)
and transport of fuels, combustion air supply , cleaning and removal of flue gas and exhausts and relevant
closed-loop and open-loop control and monitoring equipment
3.25
heated system
equipment which absorbs the heat generated in the furnaces, e.g. economiser, evaporator, and superheater
of a steam boiler, heat exchanger, gas turbine
3.26
immersion electrode
limit transducer for fluid level monitoring
3.27
logic unit
safety-related control and switching equipment which receives signals from sensors, limiters and other
monitoring devices. Its purpose is to control actuating elements according to the specified safety function
Note 1 to entry: Protective equipment
...