Water-tube boilers and auxiliary installations - Part 8: Requirements for firing systems for liquid and gaseous fuels for the boiler

1.1   Firing systems
This document specifies requirements for liquid and gaseous fuel firing systems of steam boilers and hot water generators as defined in EN 12952-1:2015.
These requirements also apply to firing systems of chemical recovery boilers (black liquor boilers) with the additions and amendments specified in Annex A.
These requirements also apply to gas turbines in combination with fired/unfired heat recovery steam generators with the additions and amendments specified in Annex B.
NOTE 1   This document is not applicable to coil type boilers (flash boilers/small boilers) that use burners in accordance with EN 12953-7 for single burner installations.
NOTE 2   This document is not applicable to the storage of liquid fuels and to transfer stations of long-distance gas pipelines.
1.2   Fuels
This document specifies requirements which cover the use of liquid and gaseous fuels as defined in this document. Fuels deviating from standardized commercially available types can require additional or alternative safety measures. For black liquor these safety measures are given in Annex A.

Wasserrohrkessel und Anlagenkomponenten - Teil 8: Anforderungen an Feuerungsanlagen für flüssige und gasförmige Brennstoffe für den Kessel

1.1   Feuerungsanlagen
Dieses Dokument legt Anforderungen an Feuerungsanlagen für flüssige und gasförmige Brennstoffe von Dampf- und Heißwassererzeugungsanlagen nach EN 12952 1:2015 fest.
Diese Anforderungen gelten für Feuerungsanlagen von Laugenrückgewinnungskesseln (Schwarzlaugen-kesseln) mit den in Anhang A aufgeführten Zusätzen und Ergänzungen.
Diese Anforderungen gelten auch für Gasturbinen in Kombination mit befeuerten/unbefeuerten Wärmerückgewinnungsdampferzeugern, mit den in Anhang B festgelegten Zusätzen und Ergänzungen.
ANMERKUNG 1   Dieses Dokument gilt nicht für Spiralrohrkessel (Schnellverdampfer/kleine Kessel), für die Öl- und Gasfeuerungsanlagen nach EN 12953 7 für Anlagen mit Einzelbrenner verwendet werden.
ANMERKUNG 2   Dieses Dokument gilt nicht für die Lagerung flüssiger Brennstoffe und für Übergabestationen für Ferngas.
1.2   Brennstoffe
Die in diesem Dokument festgelegten Anforderungen gelten für flüssige und gasförmige Brennstoffe nach diesem Dokument. Für nicht normgerechte handelsübliche flüssige oder gasförmige Brennstoffe können zusätzliche oder alternative Sicherheitsmaßnahmen notwendig werden. Für Schwarzlauge sind diese Sicherheitsmaßnahmen in Anhang A aufgeführt.

Chaudières à tubes d'eau et installations auxiliaires - Partie 8 : Exigences pour les équipements de chauffe pour combustibles gazeux et liquides de la chaudière

1.1   Équipements de chauffe
Le présent document spécifie les prescriptions relatives aux équipements de chauffe pour combustibles liquides et gazeux pour les chaudières à vapeur et les générateurs d'eau surchauffée définis dans l’EN 12952 1:2015.
Ces exigences s’appliquent aussi aux équipements de chauffe des chaudières de récupération chimique (chaudières à liqueur noire) avec les compléments et les amendements spécifiés dans l’Annexe A.
Ces prescriptions s'appliquent également aux turbines à gaz combinées à des générateurs de vapeur à récupération de chaleur avec ou sans combustion, avec les ajouts et modifications précisés à l'Annexe B.
NOTE 1   Ce document ne s‘applique pas aux chaudières à serpentins (chaudières à vaporisation instantanée/chaudières à faible volume) utilisant des brûleurs conformément à l’EN 12953 7 pour les installations à brûleur unique.
NOTE 2   Ce document ne s‘applique pas au stockage de combustibles liquides et aux postes de livraison équipés de tuyauteries de transport de très grande longueur.
1.2   Combustibles
Le présent document spécifie les exigences qui concernent l’utilisation de combustibles liquides et gazeux tels que définis dans ce document. Les combustibles s'écartant des types normalisés disponibles dans le commerce peuvent nécessiter des mesures de sécurité supplémentaires ou alternatives. Pour la liqueur noire, ces mesures de sécurité sont données en Annexe A.

Vodocevni kotli in pomožne napeljave - 8. del: Zahteve za gorilnike kotlov na tekoča in plinasta goriva

General Information

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Published
Publication Date
18-Oct-2022
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
19-Oct-2022
Due Date
26-Aug-2021
Completion Date
19-Oct-2022

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SLOVENSKI STANDARD
SIST EN 12952-8:2022
01-december-2022
Nadomešča:
SIST EN 12952-8:2002
Vodocevni kotli in pomožne napeljave - 8. del: Zahteve za gorilnike kotlov na
tekoča in plinasta goriva

Water-tube boilers and auxiliary installations - Part 8: Requirements for firing systems for

liquid and gaseous fuels for the boiler
Wasserrohrkessel und Anlagenkomponenten - Teil 8: Anforderungen an
Feuerungsanlagen für flüssige und gasförmige Brennstoffe für den Kessel

Chaudières à tubes d'eau et installations auxiliaires - Partie 8 : Exigences pour les

équipements de chauffe pour combustibles gazeux et liquides de la chaudière
Ta slovenski standard je istoveten z: EN 12952-8:2022
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
SIST EN 12952-8:2022 en,fr,de

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

---------------------- Page: 1 ----------------------
SIST EN 12952-8:2022
---------------------- Page: 2 ----------------------
SIST EN 12952-8:2022
EN 12952-8
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 27.040 Supersedes EN 12952-8:2002
English Version
Water-tube boilers and auxiliary installations - Part 8:
Requirements for firing systems for liquid and gaseous
fuels for the boiler

Chaudières à tubes d'eau et installations auxiliaires - Wasserrohrkessel und Anlagenkomponenten - Teil 8:

Partie 8 : Exigences pour les équipements de chauffe Anforderungen an Feuerungsanlagen für flüssige und

pour combustibles gazeux et liquides de la chaudière gasförmige Brennstoffe für den Kessel

This European Standard was approved by CEN on 15 August 2022.

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

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

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

member.

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

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

Centre has the same status as the official versions.

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

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12952-8:2022 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
Contents Page

European foreword ............................................................................................................................................ 4

1 Scope .......................................................................................................................................................... 6

1.1 Firing systems ........................................................................................................................................ 6

1.2 Fuels ........................................................................................................................................................... 6

2 Normative references .......................................................................................................................... 6

3 Terms and definitions ......................................................................................................................... 7

4 Fuel supply ............................................................................................................................................ 11

4.1 General.................................................................................................................................................... 11

4.2 Fuel transfer and preparation ........................................................................................................ 11

4.3 Fuel lines ................................................................................................................................................ 12

4.4 Safety shut-off devices (Safety trip valves) ................................................................................ 13

5 General.................................................................................................................................................... 15

5.1 Air supply ............................................................................................................................................... 15

5.2 Air/fuel ratio ........................................................................................................................................ 16

5.3 Flue gas discharge ............................................................................................................................... 16

6 Firing system ........................................................................................................................................ 17

6.1 Burners ................................................................................................................................................... 17

6.2 Flue gas recirculation ........................................................................................................................ 18

6.3 Control and monitoring .................................................................................................................... 18

6.4 Electrical equipment.......................................................................................................................... 19

6.5 Safety precautions .............................................................................................................................. 19

6.6 Common stack for several firing systems .................................................................................. 20

7 Operating manual ............................................................................................................................... 20

8 Particular requirements for firing systems burning gaseous fuels with high relative

density .................................................................................................................................................... 20

8.1 Main firing systems ............................................................................................................................ 20

8.2 Ignition burner systems ................................................................................................................... 21

Annex A (normative) Chemical recovery boiler (black liquor boiler) .......................................... 22

A.1 General.................................................................................................................................................... 22

A.2 Additional requirements for the firing system for black liquor in the chemical

recovery boiler .................................................................................................................................... 22

A.3 Special requirements for oil- or gas firing for chemical recovery boilers ..................... 23

Annex B (normative) Gas turbines in combination with heat recovery steam generators .. 25

B.1 General.................................................................................................................................................... 25

B.2 Additional requirements for gas turbines in combination with heat recovery steam

generators ............................................................................................................................................. 25

Annex C (informative) Operational requirements for permanent supervised firing systems

for liquid and gaseous fuels ............................................................................................................ 27

C.1 General.................................................................................................................................................... 27

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SIST EN 12952-8:2022
EN 12952-8:2022 (E)

C.2 Operation ............................................................................................................................................... 27

C.3 Fuel preparation ................................................................................................................................. 27

C.4 Safety shutoff devices ........................................................................................................................ 27

C.5 Air/fuel ratio ........................................................................................................................................ 27

C.6 Modification of firing, burner or air/fuel ratio setting ......................................................... 27

C.7 Control and monitoring .................................................................................................................... 28

C.8 Emergency operation ........................................................................................................................ 28

C.9 Operating and maintenance instructions .................................................................................. 28

C.10 Firing systems burning gaseous fuels with high relative density ..................................... 28

Annex D (informative) Significant technical changes between this document and the

previous edition .................................................................................................................................. 30

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/68/EU aimed to be covered ........................................... 31

Bibliography ....................................................................................................................................................... 33

---------------------- Page: 5 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
European foreword

This document (EN 12952-8:2022) 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 April 2023, and conflicting national standards shall be

withdrawn at the latest by April 2023.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN 12952-8:2002.

The technical modifications in comparison with the previous edition are listed in Annex D.

The EN 12952 series “Water-tube boilers and auxiliary installations” 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: In-service boiler life expectancy calculations;
• Part 5: Workmanship and construction of pressure parts of the boiler;

• Part 6: Inspection during construction, documentation and marking of pressure parts of the boiler;

• Part 7: Requirements for equipment for the boiler;

• Part 8: Requirements for firing systems for liquid and gaseous fuels for the boiler;

• Part 9: Requirements for firing systems for pulverized solid fuels for the boiler;

• Part 10: Requirements for safeguards against excessive pressure;
• Part 11: Requirements for limiting devices of the boiler and accessories;
• Part 12: Requirements for boiler feedwater and boiler water quality;
• Part 13: Requirements for flue gas cleaning systems;

• Part 14: Requirements for flue gas DENOX systems using liquefied pressurized ammonia and ammonia

water solution;
• Part 15: Acceptance tests;

• Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler;

• CR 12952 Part 17: Guideline for the involvement of an inspection body independent of the

manufacturer.
---------------------- Page: 6 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
• Part 18: Operating instructions

Although these parts can be obtained separately, it should be recognized that the parts are inter-

dependent. As such, the design and manufacture of water-tube boilers requires the application of more

than one part in order for the requirements of the document to be satisfactorily fulfilled.

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.

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

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

Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,

Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North

Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United

Kingdom.
---------------------- Page: 7 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
1 Scope
1.1 Firing systems

This document specifies requirements for liquid and gaseous fuel firing systems of steam boilers and hot

water generators as defined in EN 12952-1:2015.

These requirements also apply to firing systems of chemical recovery boilers (black liquor boilers) with

the additions and amendments specified in Annex A.

These requirements also apply to gas turbines in combination with fired/unfired heat recovery steam

generators with the additions and amendments specified in Annex B.

NOTE 1 This document is not applicable to coil type boilers (flash boilers/small boilers) that use burners in

accordance with EN 12953-7 for single burner installations.

NOTE 2 This document is not applicable to the storage of liquid fuels and to transfer stations of long-distance

gas pipelines.
1.2 Fuels

This document specifies requirements which cover the use of liquid and gaseous fuels as defined in this

document. Fuels deviating from standardized commercially available types can require additional or

alternative safety measures. For black liquor these safety measures are given in Annex A.

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 161:2011+A3:2013, Automatic shut-off valves for gas burners and gas appliances

EN 751-3:1996, Sealing materials for metallic threaded joints in contact with 1st, 2nd and 3rd family gases

and hot water – Part 3: Unsintered PTFE tapes

EN 12952-18:2012, Water-tube boilers and auxiliary installations - Part 18: Operating instructions

EN 12952-5:2021, Water-tube boilers and auxiliary installations - Part 5: Workmanship and construction

of pressure parts of the boiler
EN 13480-2:2017, Metallic industrial piping - Part 2: Materials

EN 16678:2015, Safety and control devices for gas burners and gas burning appliances - Automatic shut-

off valves for operating pressure of above 500 kPa up to and including 6 300 kPa

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 ISO 9606-1:2017, Qualification testing of welders - Fusion welding - Part 1: Steels (ISO 9606-1:2012

including Cor 1:2012 and Cor 2:2013)
As impacted by EN 751-3:1996/AC:1997.
---------------------- Page: 8 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)

EN ISO 23553-1:2022, Safety and control devices for oil burners and oil-burning appliances - Particular

requirements - Part 1: Automatic and semi-automatic valves (ISO 23553-1:2022)

ISO 7-1:1994, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions,

tolerances and designation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
black liquor
spent liquor from the pulp cook
3.2
black liquor gun

device for the introduction of the black liquor as a spray of droplets into the furnace

Note 1 to entry: The black liquor gun is not a burner.
3.3
high volume low concentration odorous gas

mixtures of air and a low concentration of odorous gases collected from the pulp mill processes, where

the concentration of the combustible odorous gas is always kept below the lower explosion limit

3.4
burner

device (including main or igniter burners) for the introduction of fuel and air into a combustion chamber

of a steam generator at required velocities, turbulence and local fuel concentration to establish and

maintain proper ignition and stable combustion of the fuel
Note 1 to entry: Burners are differentiated by their mode of operation.
3.4.1
chemical recovery boiler start-up burner

oil- or gasfired burner mainly intended for the initiation of the black liquor combustion process

Note 1 to entry: The chemical recovery boiler start-up burners are located in and integrated with a combustion air

register, like the primary or the secondary air register of the furnace. Thus, they have no individual air supply and

no individual combustion air control.
3.4.2
multi-fuel burner

burner in which more than one fuel is burned either simultaneously or alternately

3.4.3
pilot burner

burner which maintains a proper permanent ignition source for one or a group of other non-monitored

burners
---------------------- Page: 9 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
3.5
burner group

burners operated in unison and controlled jointly, one of which can be a master burner

3.6
burner management system

system that performs a predetermined sequence of actions and always operates in conjunction with a

flame monitor that reacts to signals from control and safety devices, gives control commands, controls

the start-up sequence, supervises the burner operation, and manages controlled shutdown and lockout

3.7
firing system

total equipment required for the combustion of fuels including the installations for the storage,

preparation, and supply of fuels, the combustion air supply, the burner(s), the flue gas discharge, and all

related control and monitoring devices

Note 1 to entry: A flue gas recirculation system can be an integral part of the firing system.

3.8
firing system heat input

heat input into the combustion chamber according to the mass flow of the fuel supplied multiplied by the

net calorific value
3.9
flame monitor

device which detects the presence or absence or break-away of the flame and transmits a signal to the

control device, and generally consists of a sensing device (with amplifier if necessary) and switching

equipment
3.10
flue gas recirculation

return of flue gas from downstream of the flame zone or from the flue gas exit by hydrodynamic pressure

difference or a separate fan into the air register of the burner or directly into the combustion chamber

3.11
implosion

unintentional instantaneous negative pressure build-up caused, for example, by an explosion in a

confined space, by rapid closing of dampers, or by rapid reduction in temperature (flame out)

3.12
limiters

transducer, which, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to

interrupt and lock-out the energy supply, and requires manual unlocking before restart

3.13
lock-out
isolation of energy supply which requires a manual intervention to reinstate
3.14
master fuel trip
extinction of all burners and igniters in the combustion chamber
---------------------- Page: 10 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
3.15
maximum heat input of the firing system

heat input including the reserve required for load control at which the boiler can be safely operated

3.16
maximum firing rate of the burners
firing rate at which the burner may be operated
3.17
monitor

limit transducer which senses the reaching of a fixed limit value and initiates an alarm and/or a cut out

Note 1 to entry: The output signal is only cancelled if the cause of the alarm has been removed and the value has

returned to within its fixed limits.
3.18
multi-fuel firing system

firing system where, in a common combustion chamber, more than one fuel can be burnt simultaneously

or alternately by separate or multi-fuel burners
3.19
purge of burner guns

carried out after shutdown of a burner to ensure the removal of residual fuel by the introduction of steam

or pressurized air into the fuel lines downstream of the shut-off devices
3.20
purging of the flue gas passes

forced flow of air through the combustion chamber, flue gas passes, and associated ducts which

effectively removes any gaseous combustibles and replace them with air
3.21
quick-acting shut-off device

safety trip valve which closes within 1 s according to EN 161:2011+A3:2013, EN 16678:2015 or

EN ISO 23553-1:2022, as appropriate
3.22
relative density

ratio of the density of the gas to the density of dry air under equal conditions of pressure and temperature

3.23
liquid fuel

fuel including light fuel oils, and heavy fuel oils which need preheating for proper atomisation

Note 1 to entry: For improvement of atomisation, emulsions of heavy fuel oil with water may be used with

appropriate precautions
3.24
gaseous fuel
standardized quality differentiated mainly by their relative density
---------------------- Page: 11 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
3.24.1
light gas

with relative density below 1,3 e.g. natural gas, coke-oven gas, blast-furnace gas

Note 1 to entry: Natural gas in accordance with ISO 6976 [4].
3.24.2
heavy gas

with relative density exceeding 1,3 e.g. liquefied petroleum gases, the main components of which are

propane and butane
3.25
restart

operation where fuel supply shut-off is initiated within 1 s at the latest after extinction of the flame during

operation, and a directly following attempt of re-ignition is automatically made in compliance with the

start-up sequence

Note 1 to entry: This operation ends with the operating condition being reached or, if the flame is not ignited after

expiration of the ignition safety time, with the lock-out.
3.26
return-flow atomizer

oil burners where a portion of the quantity of oil supplied to the burner via the flow line does not flow

from a burner gun vortex chamber into the combustion chamber, but flows backwards into the storage

tank or to the suction side of the pump via a separate return line
Note 1 to entry: Output is adjusted by a control device in the return line.
3.27
safety shut-off device
safety trip valve
valve which automatically and totally cuts off the fuel supply
3.28
safety time

time taken from the occurrence of an unsafe operating condition (for example, flame interrupt during

normal operation) to the point at which the actuating element is initiated

Note 1 to entry: The reaction time of the actuating element is to be considered separately.

[SOURCE: EN 50156-1:2015 [9], 3.43]
3.28.1
ignition time

when starting-up the burner, the period of time between the first fuel entering the combustion chamber

and the first indication of the flame by the flame monitor
3.28.2
ignition safety time

when starting-up the burner, the period of time between the first fuel entering the combustion chamber

and the de-energizing of the quick-acting shut-off device if the flame monitor does not indicate a flame

---------------------- Page: 12 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)
3.28.3
main burner safety time

when there is an ignition safety time applicable to an igniter burner only, the period of time between the

first fuel of the main burner entering the combustion chamber and the de energizing of the quick acting

shut-off device of the main burner if the flame monitor does not indicate a flame

3.28.4
extinction safety time

during operation of the burner, the period of time between the extinction of the flame and the de-

energizing of the quick-acting shut-off device
3.29
transfer station

one or more lines each including a pressure control valve and a quick-acting shut-off device for the

protection of the downstream supply lines and the connected appliances against overpressure

Note 1 to entry: The transfer station may comprise heating and filtering equipment for the gas supply, measuring

equipment for flow and calorific value and noise abatement devices.
4 Fuel supply
4.1 General

For multifuel firing systems using separate or combined burners these requirements shall apply to the

oil and/or gas firing part involved.

Where several fuels are burnt simultaneously, improved safety measures can be necessary, especially in

respect to limitation of heat input into the firing system and proper air supply to the individual fuels.

4.2 Fuel transfer and preparation

4.2.1 The fuel supply line shall be equipped with a reliable shut-off device which shall be positioned in

a safe location. It shall reliably cut off the fuel supply to the boiler room or the boiler area and shall be

operable by remote control or by an emergency switch (see 6.4.2).

4.2.2 Some liquid fuels, such as heavy fuel oil, require preheating to achieve the viscosity required for

proper atomisation. Where national oil quality standards are in existence, these shall be observed.

Any heat source other than open flames, that can be cut off immediately if required, and the rating of

which can be automatically controlled, shall be used for oil preheating.

In the unpressurized condition the fuel oil temperature shall not attain the fuel oil flash point.

To attain the temperature for the required atomisation viscosity, pressure type preheaters shall be used.

The maximum temperature shall be at least 5 °C below the boiling temperature of water in the oil at the

connected pressure.

Each fuel oil preheating system shall be automatically temperature controlled. A temperature indicator

shall be fitted downstream of the preheating system. Oil temperatures below the temperature prescribed

upstream of each burner or burner group shall shut off the burner or burner group.

Oil temperatures above the temperature prescribed upstream of the burners shall shut off the heat supply

of the preheater or other suitable measures shall be taken.

For pressurized preheaters, the requirements for pressure vessels shall be applied. Functioning of the

necessary overpressure protection shall be ensured by suitable temperature control. Any escaping oil

shall be safely discharged.
---------------------- Page: 13 ----------------------
SIST EN 12952-8:2022
EN 12952-8:2022 (E)

Where steam heating coils for oil preheating are installed and the condensate is returned to the boiler,

the heating coils shall be safely dimensioned and tested to ensure that no oil can escape into the

condensate. A means of checking the condensate for oil content shall be provided. When steam lines are

connected to fuel oil lines for purging purposes or for steam assisted atomisation, the line shall be

protected against back flow from the higher pressured fluid.

4.2.3 For gaseous fuels, a pressure controller shall be provided in the supply line assuring continuous

flow pressure to each firing system unless this task is performed by the transfer station. The pressure

controller shall reliably prevent the firing system from overpressurization when the control function has

failed.
NOTE Requirements on pressure controller can be found in EN 676:2020 [3].
4.3 Fuel lines

4.3.1 Fuel lines, including gaskets and valves shall be designed and laid out to withstand the

mechanical, chemical and thermal loads to which they are exposed in service. Only fire resistant piping

material shall be permitted.

4.3.2 The fuel lines shall be tight and properly fixed. In systems subjected to vibrations

...

SLOVENSKI STANDARD
oSIST prEN 12952-8:2020
01-marec-2020
Vodocevni kotli in pomožne napeljave - 8. del: Zahteve za gorilnike kotlov na
tekoča in plinasta goriva

Water-tube boilers and auxiliary installations - Part 8: Requirements for firing systems for

liquid and gaseous fuels for the boiler
Wasserrohrkessel und Anlagenkomponenten - Teil 8: Anforderungen an
Feuerungsanlagen für flüssige und gasförmige Brennstoffe für den Kessel

Chaudières à tubes d'eau et installations auxiliaires - Partie 8 : Exigences pour les

équipements de chauffe pour combustibles gazeux et liquides de la chaudière
Ta slovenski standard je istoveten z: prEN 12952-8
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
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oSIST prEN 12952-8:2020 en,fr,de

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

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oSIST prEN 12952-8:2020
DRAFT
EUROPEAN STANDARD
prEN 12952-8
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2020
ICS 27.040 Will supersede EN 12952-8:2002
English Version
Water-tube boilers and auxiliary installations - Part 8:
Requirements for firing systems for liquid and gaseous
fuels for the boiler

Chaudières à tubes d'eau et installations auxiliaires - Wasserrohrkessel und Anlagenkomponenten - Teil 8:

Partie 8 : Exigences pour les équipements de chauffe Anforderungen an Feuerungsanlagen für flüssige und

pour combustibles gazeux et liquides de la chaudière gasförmige Brennstoffe für den Kessel

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, Turkey 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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12952-8:2020 E

worldwide for CEN national Members.
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Contents Page

European foreword ...................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 6

1.1 Firing systems .................................................................................................................................................. 6

1.2 Fuels ..................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 7

4 Fuel supply ...................................................................................................................................................... 11

4.1 General.............................................................................................................................................................. 11

4.2 Fuel transfer and preparation .................................................................................................................. 11

4.3 Fuel lines .......................................................................................................................................................... 12

4.4 Safety shut-off devices (Safety trip valves) .......................................................................................... 13

5 General.............................................................................................................................................................. 15

5.1 Air supply ......................................................................................................................................................... 15

5.2 Air/fuel ratio .................................................................................................................................................. 16

5.3 Flue gas discharge ......................................................................................................................................... 16

6 Firing system .................................................................................................................................................. 16

6.1 Burners ............................................................................................................................................................. 16

6.2 Flue gas recirculation .................................................................................................................................. 17

6.3 Control and monitoring .............................................................................................................................. 18

6.4 Electrical equipment.................................................................................................................................... 19

6.5 Safety precautions ........................................................................................................................................ 19

6.6 Common stack for several firing systems ............................................................................................ 20

7 Operating manual ......................................................................................................................................... 20

8 Particular requirements for firing systems burning gaseous fuels with high relative

density .............................................................................................................................................................. 20

8.1 Main firing systems ...................................................................................................................................... 20

8.1.1 Supply of gases ............................................................................................................................................... 20

8.1.2 Safety shut-off device ................................................................................................................................... 20

8.2 Ignition burner systems ............................................................................................................................. 21

Annex A (normative) Chemical recovery boiler (black liquor boiler) .................................................... 22

A.1 General.............................................................................................................................................................. 22

A.2 Additional requirements for the firing system for black liquor in the chemical

recovery boiler .............................................................................................................................................. 22

A.3 Special requirements for oil- or gas firing for chemical recovery boilers ............................... 23

A.3.1 General.............................................................................................................................................................. 23

A.3.2 Special requirements for start-up burners ......................................................................................... 23

A.3.3 Special requirements for the firing of odorous gases ...................................................................... 24

Annex B (normative) Gas turbines in combination with heat recovery steam generators ............ 25

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B.1 General ............................................................................................................................................................. 25

B.2 Additional requirements for gas turbines in combination with heat recovery steam

generators ....................................................................................................................................................... 25

B.2.1 Safety shut-off devices ................................................................................................................................ 25

B.2.2 Electrical equipment ................................................................................................................................... 25

B.2.3 Bypass operation of the heat recovery boiler .................................................................................... 25

B.2.4 Switching from gas turbine operation to fresh air operation at secondary firing ................ 25

Annex C (informative) Operational requirements for permanent supervised firing systems

for liquid and gaseous fuels ...................................................................................................................... 27

C.1 General ............................................................................................................................................................. 27

C.2 Operation ......................................................................................................................................................... 27

C.3 Fuel preparation ........................................................................................................................................... 27

C.4 Safety shutoff devices .................................................................................................................................. 27

C.5 Air/fuel ratio .................................................................................................................................................. 27

C.6 Modification of firing, burner or air/fuel ratio setting ................................................................... 27

C.7 Control and monitoring .............................................................................................................................. 28

C.8 Emergency operation .................................................................................................................................. 28

C.9 Operating and maintenance instructions ............................................................................................ 28

C.10 Firing systems burning gaseous fuels with high relative density ............................................... 28

Annex D (informative) Significant technical changes between this document and the

previous edition ............................................................................................................................................ 30

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/68/EU aimed to be covered ..................................................... 31

Bibliography ................................................................................................................................................................. 32

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European foreword

This document (prEN 12952-8:2020) 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 12952-8:2002.

EN 12952 series “Water-tube boilers and auxiliary installations” 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: In-service boiler life expectancy calculations;
• Part 5: Workmanship and construction of pressure parts of the boiler;

• Part 6: Inspection during construction, documentation and marking of pressure parts of the boiler;

• Part 7: Requirements for equipment for the boiler;

• Part 8: Requirements for firing systems for liquid and gaseous fuels for the boiler;

• Part 9: Requirements for firing systems for pulverized solid fuels for the boiler;

• Part 10: Requirements for safeguards against excessive pressure;
• Part 11: Requirements for limiting devices of the boiler and accessories;
• Part 12: Requirements for boiler feedwater and boiler water quality;
• Part 13: Requirements for flue gas cleaning systems;

• Part 14: Requirements for flue gas DENOX systems using liquefied pressurized ammonia and ammonia

water solution;
• Part 15: Acceptance tests;

• Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler;

• CR 12952 Part 17: Guideline for the involvement of an inspection body independent of the

manufacturer.

Although these parts may be obtained separately, it should be recognized that the parts are inter-

dependent. As such, the design and manufacture of water-tube boilers requires the application of more

than one part in order for the requirements of the document to be satisfactorily fulfilled.

NOTE Part 4 and Part 15 are not applicable during the design, construction and installation stages.

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This European Standard 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

standard.
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1 Scope
1.1 Firing systems

This document specifies requirements, for liquid and gaseous fuel firing systems of steam boilers and

hot water generators as defined in EN 12952-1:2015.

These requirements also apply to firing systems of chemical recovery boilers (black liquor boilers) with

the additions and amendments specified in Annex A of this document.

These requirements also apply to gas turbines in combination with fired/unfired heat recovery steam

generators with the additions and amendments specified in Annex B of this document.

NOTE 1 This standard is not applicable to coil type boilers (flash boilers/small boilers) that use burners in

accordance with EN 12953-7 apply for single burner installations.

NOTE 2 This standard is not applicable to the storage of liquid fuels and to transfer stations of long-distance

gas pipelines.
1.2 Fuels

This document specifies requirements, which cover the use of liquid and gaseous fuels as defined in this

standard. Fuels deviating from standardized commercially available types may require additional or

alternative safety measures. For black liquor these safety measures are given in Annex A.

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 161:2011+A3:2013, Automatic shut-off valves for gas burners and gas appliances

EN 751 (series), Sealing materials for metallic threaded joints in contact with 1st, 2nd and 3rd family

gases and hot water

EN 16678:2015, Safety and control devices for gas burners and gas burning appliances - Automatic shut-

off valves for operating pressure of above 500 kPa up to and including 6 300 kPa

EN ISO 23553-1:2014, Safety and control devices for oil burners and oil-burning appliances - Particular

requirements - Part 1: Automatic and semi-automatic valves (ISO 23553-1:2014)

prEN 12952-5:2020, Water-tube boilers and auxiliary installations — Part 5: Workmanship and

construction of pressure parts of the boiler
EN 13480-2:2017, Metallic industrial piping - Part 2: Materials

EN 50156-1:2015, Electrical equipment for furnaces and ancillary equipment - Part 1: Requirements for

application design and installation

EN ISO 3677:2016, Filler metal for soldering and brazing - Designation (ISO 3677:2016)

EN ISO 9606-1:2017, Qualification testing of welders - Fusion welding - Part 1: Steels (ISO 9606-1:2012

including Cor 1:2012 and Cor 2:2013)
Under preparation
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ISO 7-1:1994, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions,

tolerances and designation

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)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
black liquor
spent liquor from the pulp cook
3.2
black liquor gun

device for the introduction of the black liquor as a spray of droplets into the furnace

Note 1 to entry: The black liquor gun is not a burner.
3.3
high volume low concentration odorous gas

mixtures of air and a low concentration of odorous gases collected from the pulp mill processes, where

the concentration of the combustible odorous gas is always kept below the lower explosion limit

3.4
burners

devices (including main or igniter burners) for the introduction of fuel and air into a combustion

chamber of a steam generator at required velocities, turbulence and local fuel concentration to establish

and maintain proper ignition and stable combustion of the fuel
Note 1 to entry: Burners are differentiated by their mode of operation.
3.4.1
chemical recovery boiler start up burner

oil- or gasfired burner mainly intended for the initiation of the black liquor combustion process

Note 1 to entry: The chemical recovery boiler start up burners are located in and integrated with a combustion air

register, like the primary or the secondary air register of the furnace. Thus they have no individual air supply and

no individual combustion air control.
3.4.2
multi-fuel burners

burners in which more than one fuel is burned either simultaneously or alternately

3.4.3
pilot burner

burner which maintains a proper permanent ignition source for one or a group of other non-monitored

burners
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3.5
burner group

burners operated in unison and controlled jointly. One of the burners can be a master burner

3.6
burner management system

system that performs a predetermined sequence of actions and always operates in conjunction with a

flame monitor that reacts to signals from control and safety devices, gives control commands, controls

the start-up sequence, supervises the burner operation, and manages controlled shutdown and lockout

3.7
firing system

total equipment required for the combustion of fuels including the installations for the storage,

preparation, and supply of fuels, the combustion air supply, the burner(s), the flue gas discharge, and all

related control and monitoring devices

Note 1 to entry: A flue gas recirculation system can be an integral part of the firing system.

3.8
firing system heat input

heat input into the combustion chamber according to the mass flow of the fuel supplied multiplied by

the net calorific value
3.9
flame monitor

device which detects the presence or absence or break-away of the flame and transmits a signal to the

control device, and generally consists of a sensing device (with amplifier if necessary) and switching

equipment
3.10
flue gas recirculation

return of flue gas from downstream of the flame zone or from the flue gas exit by hydrodynamic

pressure difference or a separate fan into the air register of the burner or directly into the combustion

chamber
3.11
implosion

unintentional instantaneous negative pressure build-up caused, for example, by an explosion in a

confined space, by rapid closing of dampers, or by rapid reduction in temperature (flame out)

3.12
limiters

transducer, which, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to

interrupt and lock-out the energy supply, and requires manual unlocking before restart

3.13
lock-out
isolation of energy supply which requires a manual intervention to reinstate
3.14
master fuel trip
extinction of all burners and igniters in the combustion chamber
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3.15
maximum heat input of the firing system

heat input including the reserve required for load control at which the boiler can be safely operated

3.16
maximum firing rate of the burners
firing rate at which the burner may be operated
3.17
monitor

limit transducer, which senses the reaching of a fixed limit value and initiates an alarm and/or a cut out

Note 1 to entry: The output signal is only cancelled if the cause of the alarm has been removed and the value has

returned to within its fixed limits.
3.18
multi-fuel firing system

firing system where, in a common combustion chamber, more than one fuel can be burnt

simultaneously or alternately by separate or multi-fuel burners
3.19
purge of burner guns

carried out after shutdown of a burner to ensure the removal of residual fuel by the introduction of

steam or pressurized air into the fuel lines downstream of the shut-off devices
3.20
purging of the flue gas passes

forced flow of air through the combustion chamber, flue gas passes, and associated ducts which

effectively removes any gaseous combustibles and replace them with air
3.21
quick-acting shut-off device

safety trip valve which closes within 1 s according to EN 161:2011+A3:2013 or EN 264

3.22
relative density

ratio of the density of the gas to the density of dry air under equal conditions of pressure and

temperature
3.23
liquid fuels

fuels include light fuel oils, and heavy fuel oils which need preheating for proper atomisation. For

improvement of atomisation, emulsions of heavy fuel oil with water may be used with appropriate

precautions
3.24
gaseous fuels
standardized quality differentiated mainly by their relative density
3.24.1
light gases

with relative density below 1,3 e.g. natural gas, coke-oven gas, blast-furnace gas

Note 1 to entry: Natural gas in accordance with ISO 6976.
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3.24.2
heavy gases

with relative densities exceeding 1,3 e.g. liquefied petroleum gases, the main components of which are

propane and butane
3.25
restart

operation where fuel supply shut-off is initiated within 1 s at the latest after extinction of the flame

during operation, and a directly following attempt of re-ignition is automatically made in compliance

with the start-up sequence

Note 1 to entry: This operation ends with the operating condition being reached or, if the flame is not ignited after

expiration of the ignition safety time, with the lock-out.
3.26
return-flow atomizer

oil burners, where a portion of the quantity of oil supplied to the burner via the flow line does not flow

from a burner gun vortex chamber into the combustion chamber, but flows backwards into the storage

tank or to the suction side of the pump via a separate return line
Note 1 to entry: Output is adjusted by a control device in the return line.
3.27
safety shut-off device
safety trip valve
valve which automatically and totally cuts off the fuel supply
3.28
safety time

time taken from the occurrence of an unsafe operating condition (for example, flame interrupt during

normal operation) to the point at which the actuating element is initiated

Note 1 to entry: The reaction time of the actuating element is to be considered separately.

[SOURCE: EN 50156-1:2015, 3.43]
3.28.1
ignition time

when starting-up the burner, the period of time between the first fuel entering the combustion chamber

and the first indication of the flame by the flame monitor
3.28.2
ignition safety time

when starting-up the burner, the period of time between the first fuel entering the combustion chamber

and the de-energizing of the quick-acting shut-off device if the flame monitor does not indicate a flame

3.28.3
main burner safety time

when there is an ignition safety time applicable to an igniter burner only the period of time between the

first fuel of the main burner entering the combustion chamber and the de energizing of the quick acting

shut-off device of the main burner if the flame monitor does not indicate a flame

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3.28.4
extinction safety time

during operation of the burner the period of time between the extinction of the flame and the de-

energizing of the quick-acting shut-off device
3.29
transfer station

one or more lines each including a pressure control valve and a quick-acting shut-off device for the

protection of the downstream supply lines and the connected appliances against overpressure

Note 1 to entry: The transfer station may comprise of heating and filtering equipment for the gas supply,

measuring equipment for flow and calorific value and noise abatement devices.
4 Fuel supply
4.1 General

For multifuel firing systems using separate or combined burners these requirements shall apply to the

oil and/or gas firing part involved.

Where several fuels are burnt simultaneously, improved safety measures can be necessary, especially in

respect to limitation of heat input into the firing system and proper air supply to the individual fuels.

4.2 Fuel transfer and preparation

4.2.1 The fuel supply line shall be equipped with a reliable quick-acting safety shut-off device which

shall be positioned in a safe location. It shall reliably cut off the fuel supply to the boiler room or the

boiler area and shall be operable by remote control or by an emergency switch (see 6.4.2).

4.2.2 Some liquid fuels, such as heavy fuel oil, require preheating to achieve the viscosity required for

proper atomisation. Where national oil quality standards are in existence, these shall be observed.

Any heat source other than open flames, that can be cut off immediately if required, and the rating of

which can be automatically controlled, shall be used for oil preheating.

In the unpressurized condition the fuel oil temperature shall not attain the fuel oil flash point.

To attain the temperature for the required atomisation viscosity, pressure type preheaters shall be

used. The maximum temperature shall be at least 5 °C below the boiling temperature of water in the oil

at the connected pressure.

Each fuel oil preheating system shall be automatically temperature controlled. A temperature indicator

shall be fitted downstream of the preheating system. Oil temperatures below the temperature

prescribed upstream of each burner or burner group shall shut off the burner or burner group.

Oil temperatures above the temperature prescribed upstream of the burners shall shut off the heat

supply of the preheater or other suitable measures shall be taken.

For pressurized preheaters, the requirements for pressure vessels shall be applied. Functioning of the

necessary overpressure protection shall be ensured by suitable temperature control. Any escaping oil

shall be safely discharged.

Where steam heating coils for oil preheating are installed and the condensate is returned to the boiler,

the heating coils shall be safely dimensioned and tested to ensure tha
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