SIST EN 12952-7:2002

SLOVENSKI STANDARD
SIST EN 12952-7:2002
01-november-2002
Vodocevni kotli in pomožne napeljave - 7. del: Zahteve za opremo kotla
Water-tube boilers and auxiliary installations - Part 7: Requirements for equipment for the
boiler
Wasserrohrkessel und Anlagenkomponenten - Teil 7: Anforderungen an die Ausrüstung
für den Kessel
Chaudieres a tubes d'eau et installations auxiliaires - Partie 7: Exigences pour
l'équipement de la chaudiere
Ta slovenski standard je istoveten z: EN 12952-7:2002
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
SIST EN 12952-7:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 12952-7:2002

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SIST EN 12952-7:2002
EUROPEAN STANDARD
EN 12952-7
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2002
ICS 27.040
English version
Water-tube boilers and auxiliary installations - Part 7:
Requirements for equipment for the boiler
Chaudières à tubes d'eau et installations auxiliaires - Partie Wasserrohrkessel und Anlagenkomponenten - Teil 7:
7: Exigences pour l'équipement de la chaudière Anforderungen an die Ausrüstung für den Kessel
This European Standard was approved by CEN on 25 March 2002.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12952-7:2002 E
worldwide for CEN national Members.

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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
Contents
1 Scope .4
2 Normative references .4
3 Terms and definitions.5
3.1 Types of steam boilers and hot water generators.5
3.6 Classification of pressure generation systems (Hot water generators) .5
4 General requirements for steam boilers and hot water generators .7
4.1 Safeguards against excessive pressure .7
4.2 Heat supply system .7
4.3 Ash removal plants.7
4.4 Flue-gas cleaning plants .7
4.5 Requirements for limiting devices and safety circuits .8
4.6 Cleaning, access and inspection openings .8
4.7 Feed lines and protection against feedwater backflow .12
4.8 Connection of steam boilers or hot water generators .12
5 Special requirements for steam boilers .13
5.1 Requirements for pumps .13
5.2 Isolating and drain devices.14
5.3 Lowest permissible water level (LWL).14
5.4 Water level and flow indicators .15
5.5 Water supply control and protective device against water shortage.16
5.6 Pressure and temperature measuring devices.16
5.7 Marking .16
6 Special requirements for hot water generators.16
6.1 Requirements for hot water generating systems .16
6.2 Requirements for pumps .17
6.3 Shut-off and drain devices.18
6.4 Lowest permissible water level and installation of flow and return line.19
6.5 Water level and flow indicators .19
6.6 Water supply and drain control, protective device against water shortage.20
6.7 Safeguards against minimum pressure .20
6.8 Safety device for temperature control .20
6.9 Pressure and temperature indicating devices.20
6.10 Marking .21
7 Additional requirements for plants without permanent supervision .21
7.1 General.21
7.2 Steam boilers.21
7.3 Hot water generators .22
8 Final assessment of safety devices.24
8.1 Performance of inspection.24
8.2 Equipment on the steam and water side .24
8.3 Firing system equipment .25
8.4 Electrical safety circuit.25
8.5 Operating instructions .25
9 Small plant boilers .25
9.1 Steam boilers.25
9.2 Hot water generators .26
Annex A (normative) Chemical recovery boilers (Black liquor recovery boilers) .28
Annex B (informative) Design examples for hot water generating systems.30
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of the Pressure Equipment Directive.49
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
Foreword
This document (EN 12952-1:2002) 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 November 2002, and conflicting national standards shall be withdrawn at the latest
by November 2002.
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
This Part of this European Standard has been prepared under a mandate given to CEN by the European Commis-
sion and the European Free Trade Association and supports essential safety requirements of the Pressure Equip-
ment Directive (PED) [1]. For relationship with Pressure Equipment Directive see informative Annex ZA, which is an
integral Part of this Standard.
The European Standard EN 12952 concerning 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.
Part 15: Acceptance tests.
Part 16: Requirements for grate and fluidized bed firing systems for solid fuels for the boiler.
CR 12952-17: Guideline for the involvement of an inspection body independent of the manufacturer.
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 standard to be satisfactorily fulfilled.
NOTE Parts 4 and 15 are not applicable during the design, construction and installation stages.
The Annex A is normative. The Annex B of this European Standard are informative.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following coun-
tries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Swe-
den, Switzerland and the United Kingdom.
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
1 Scope
This Part of this European Standard specifies the requirements for equipment for steam boilers and hot water
generators as defined in EN 12952-1, wherein steam or hot water will be generated. Requirements for equipment
for chemical recovery boilers are given in Annex A, and design examples for hot water generating systems are
given in Annex B.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 837-1, Pressure gauges — Part 1: Bourdon tube pressure gauges — Dimensions, metrology, requirements and
testing.
EN 12952-1,
 

  


  1: General.
EN 12952-6,
 

  


  6: Inspection during construction; documentation
and marking of pressure parts of the boiler.
EN 12952-8,
 

  


  8: Requirements for firing systems for liquid and
gaseous fuels for the boiler.
prEN 12952-9,
 

  


  9: Requirements for firing systems for pul-
verized solid fuels for the boiler.
prEN 12952-10,
 

  


  10: Requirements for safeguards against ex-
cessive pressure.
prEN 12952-11,
 

  


  11: Requirements for limiting devices of the
boiler and accessories.
prEN 12952-12,
 

  


  12: Requirements for feedwater and boiler
water quality.
prEN 12952-13,
 

  


  13: Requirements for flue gas cleaning sys-
tems.
prEN 12952-14,
 

  


  14:Requirements for flue gas DE-
NOX-systems.
prEN 12952-16,
 

  


  16: Requirements for fluidized bed and grate
firing systems for solid fuels for the boiler.
prEN 50156-1, Electrical equipment for furnaces and ancillary equipment — Part 1: Requirements for application
design and installation.
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
3 Terms and definitions
For the purposes of this Part of this European Standard, the following terms and definitions apply in addition to
those given in EN 12952-1, prEN 12952-8 and prEN 12952-9.
3.1
Types of steam boilers and hot water generators
3.1.1
natural circulation steam boilers and hot water generators
steam boilers and hot water generators in which the water to be evaporated/heated circulates due to the differ-
ences in density (see Figure B.3-1)
3.1.2
forced or assisted circulation steam boilers and hot water generators
steam boilers and hot water generators in which the water to be evaporated/heated is circulated by means of
pumps (see Figure B.3-2)
3.1.3
once-through steam boilers and hot water generators
steam boilers, with or without separating vessels, where the water flow is determined by the feed pump, and the
water is evaporated completely or in a major portion during one single passage
Hot water generators, where the water flow is effected by the circulating pump of the heating system and is heated
during one single passage, e.g. once-through hot water generator where there is no contact between hot and cold
water in the drum (two-way drum) see Figure B.3-3 once-through hot water generator with header distributing water
from below, see Figures B.3-4 and B.4-9
3.1.4
waste heat steam boilers and hot water generators
generators utilizing heat recovered from outside sources, e.g. gas turbines, blast furnaces
3.2
limits of steam boilers and hot water generators
boundaries of the steam and water spaces located between the shut-off devices of the steam boilers and hot water
generators in the inlet, outlet, pressure retaining, overflow, and drain lines. The bodies of the shut-off devices are
considered to be within these limits
3.3
steam boilers and hot water generating plant
plant consists of the water-tube boiler and its equipment as defined in EN 12952-1
3.4
heat supply system
assembly of components in which the energy of the fuel (including electrical and waste-heat energy) is supplied to
the steam boilers and hot water generator
3.5
Classification of pressure generation systems (Hot water generators)
3.5.1
internally pressurised systems
systems where the pressure is generated by the saturation pressure corresponding to the flow temperature (see
Figures B.3-1, B.3-2, B.3-3, B.3-4, and Figure B.4-9)
3.5.2
externally pressurised systems
systems where the pressure is generated by such methods as gas cushion or pressure pumps (see Figures B.4-1
to B.4-8, B.4-10 to B.4-13)
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
3.6
expansion system (vessel and tank)
3.6.1
Expansion vessels
pressurized container to compensate temperature-dependent volume changes of the water
3.6.2
Expansion tanks
not pressurized container to compensate temperature-dependent volume changes of the water (see EN 12953-6).
3.7
sinking time
time during which the water level will sink from the lowest permissible water level (LWL) to the highest point of the
heated surface (HHS) (see 4.5.2)
NOTE For hot water generators applicable only in the case of internal pressure generation; see Figures B.3-1, B.3-2,
B.3-3, B.3-4, and B.3-9.
3.8
maximum continuous rating (MCR)
maximum continuous steam output that can be generated during continuous operation taking the specified steam
condition into consideration (see EN 12953-6)
3.9
allowable heat output
maximum heat output (water mass flow times the difference between outlet and inlet enthalpy) that can be gener-
ated during continuous operation and at which hot water generators may be operated
3.10
maximum allowable pressure
maximum pressure for which equipment is designed, as specified by the manufacturer, and at a location specified
by the manufacturer
NOTE This may be the location of connection of protective and/or limiting devices or the top of equipment or, if not appli-
cable, any point specified.
3.11
allowable flow temperature
maximum allowable temperature at which the hot water generator may be operated
3.12
controls
devices used for holding the variable to be controlled (e.g. water level, pressure, temperature) at a specified value
(set point)
3.13
limiters
device that, 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 (see EN 12953-6)
3.14
fail-safe
functional unit is fail-safe if it possesses the capability of remaining in a safe condition in the event of certain faults
occurring (e.g. internal faults)
3.15
self-monitoring
regular and automatic determination that all chosen components of a safety device are capable of functioning as
required
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
3.16
redundancy
provision of more than one device or system so that in the event on a fault, the necessary facilities will still be pro-
vided
3.17
independent
ability to function as required without interference from other equipment
3.18
reliability
ability to perform a required function under specified conditions and for a given period of time without failing
3.19
lock-out
isolation of the energy supply which requires a manual intervention to reinstate
3.20
unit test
individual testing of any unit(s) of the safety device
3.21
functional test
testing of the safety device to ensure it performs its intended function (see EN 12953-6)
3.22
permanent supervision
supervision during which the boiler operator stays close to the boiler, boiler room, operating platform or control
room so that he has sufficient time to intervene in any dangerous condition
4 General requirements for steam boilers and hot water generators
4.1 Safeguards against excessive pressure
Each steam boiler and hot water generator shall be equipped with safeguards against excessive pressure in accor-
dance with prEN 12952-10.
4.2 Heat supply system
4.2.1 For the heat supply of steam boilers and hot water generators the following Parts of this European Stan-
dard shall apply:
 EN 12952-8 for firing systems for liquid and gaseous fuels;
 prEN 12952-9 or prEN 12952-16 for solid fuels.
4.2.2 The heat supply shall be adapted to the allowable heat output as well as to the intended mode of operation.
4.3 Ash removal plants
Ash removal plant shall be in accordance with prEN 12952-9 or prEN 12952-16.
4.4 Flue-gas cleaning plants
Flue-gas cleaning plants shall be in accordance with prEN 12952-13 and prEN 12952-14.
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
4.5 Requirements for limiting devices and safety circuits
4.5.1 All limiters and their installation shall be in accordance with prEN 12952-11. The electrical safety circuits
shall correspond to prEN 50156-1 (see safety levels given in Table 4.6.1 and Annex B).
4.5.2 Functional testing of limiters shall be possible at any time for any operating condition, e.g. by simulation
where appropriate. If any part of the functional test involves delaying the cut-off and lock-out of the heat supply,
then the time delay shall not exceed a value specified by the manufacturer. For boilers fitted with water level limiter,
the time delay shall not exceed the time for the water level to fall from the lowest controlled water level to LWL at
MCR:
a) for steam boilers in the case of complete loss of feedwater supply and at maximum steam output, i.e.
V
t =
Q ⋅ v
St St
b) for hot water generators in the case of interrupted feeding and recirculation and at the allowable heat output,
i.e.
V
t =
Q ⋅ v
HW HW
where
Q is the equivalent steam generation calculated according to the allowable heat output, in kg/s;
HW
Q is the maximum continuous rating, in kg/s;
St
t is the sinking time, in s;
3;
V is the water volume between HHS and LWL, in m
3
v is the specific water volume, m /kg;
HW
3
v is the specific water volume at saturated steam temperature, in m /kg.
St
4.5.3 The result of each limiter check shall be clearly recognizable to the boiler operator, e.g. by the lighting of a
signal.
4.6 Cleaning, access and inspection openings
4.6.1 Steam boilers and hot water generators shall be provided with openings to permit cleaning and inspection
of the boiler interior. Sufficient space shall be provided to permit access to the steam and water spaces and the
combustion chamber as well.
4.6.2 Water or steam-containing components with an inside diameter of more than 1 200 mm and components
with a diameter of more than 800 mm and a length of 2 000 mm shall be so designed as to permit internal inspec-
tion. Internals shall be of such a design as not to obstruct inspection of the component walls, or it shall be possible
to remove them.
4.6.3 Headers and similar components shall be provided with adequate access for inspection of their inner sur-
face as follows:
 for inside diameters in excess of 80 mm where mud deposits can accumulate;
 for inside diameters in excess of 150 mm for any other cases.
Inspection access shall be designed as head, hand or inspection holes where manual inspection methods are to be
used or, as inspection nozzles where inspection devices are used e.g. endoscopes.
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
4.6.4 Sizes of openings in water and steam spaces shall be:
a) Manholes shall not be smaller than 320 mm · 420 mm or have an inside diameter of at least 420 mm. The
nozzle or ring height shall not exceed 300 mm, and 350 mm in the case of a tapered design. For structural or
design reasons, the openings of manholes may be reduced to 300 mm · 400 mm clear width or to 400 mm in-
side diameter. In such cases, the nozzle or ring height shall not exceed 150 mm, or 175 mm in the case of a
tapered design. For minimum number of openings see table 4.6-1;
b) Head holes shall not be smaller than 220 mm · 320 mm or have an inside diameter of at least 320 mm. The
nozzle or ring height shall not exceed 100 mm, or 120 mm in the case of a tapered design. For minimum num-
ber of openings see table 4.6-1;
c) Hand holes shall not be smaller than 100 mm · 150 mm or have an inside diameter of at least 120 mm. The
nozzle or ring height shall not exceed 65 mm, or 95 mm in the case of a tapered design. For minimum number
of openings see table 4.6-1;
d) Inspection holes shall have a diameter of 50 mm. However, they shall be provided only where a hand hole is
not possible for design reasons. For minimum number of openings see Table 4.6-1;
e) Inspection nozzles shall have an inside diameter of approximately 50 mm. They may be arranged in axial
and/or radial direction as shown in Figure 4.6-1. Radial inspection nozzles may be omitted, if connecting tubes
can be used in lieu of such nozzles.
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
Table 4.6-1 — Selection for type and minimum number of openings
Inside
length
Type and minimum number of openings required
diameter,
mm
mm
— By agreement as part of the design approval process£ 300
£ 1 200 2 inspection holes at the front faces
1 hand hole in the mid-third of cylindrical length or at one front face£ 1 500
> 300
£ 450
At least 2 hand holes, one each either near header ends or in front faces,
> 1 500 in which case the distance between the hand holes shall not exceed
2 000 mm
1 hand hole in the mid-third of cylindrical length£ 1 500
1 head hole in the mid-third of cylindrical length
> 1 500 2 hand holes, one each either near header ends or in front faces, in
£ 3 000 which case the distance between the hand holes shall not exceed
  > 450 2 000 mm
  £ 800
The number of the inspection holes shall be increased accordingly. In the
cylinder, the greatest distance between head holes shall not exceed
> 3 000 3 000 mm and between hand holes shall not exceed 2 000 mm. One
hand hole each shall be provided near the header ends or in the front
faces.
1 head hole in the mid-third of cylindrical length or
£ 2 000
  > 800
2 hand holes near the header ends or in the front faces
£ 1 200
> 2 000 1 manhole
> 1 200 — 1 manhole
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
Figure 4.6-1 — Examples of arrangements of inspection nozzles
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SIST EN 12952-7:2002
EN 12952-7:2002 (E)
4.6.5 The following shall apply with regard to the size of openings on boiler plant spaces which are to be in-
spected and contain neither water nor steam:
a) Access openings for inspection by personnel using auxiliary or personal protective equipment shall have an
inside diameter of at least 600 mm. For design reasons the minimum size of access openings may be reduced
to an inside diameter of 500 mm in which case the nozzle or ring height shall not exceed 250 mm;
b) Access openings for inspection without use of auxiliary or personal protective equipment shall have a clear
width of at least 320 mm · 420 mm. For design reasons the minimum size of access openings may be reduced
to a clear width of 300 mm · 400 mm in which case the nozzle or ring height shall not exceed 150 mm, and
175 mm in the case of a tapered design;
c) Inspection openings shall have a width of 100 mm · 150 mm or an inside diameter of 120 mm.
4.6.6 Access and inspection doors of the type in which the internal pressure forces the door against a flat gasket
shall have a minimum gasket bearing width of 15 mm for manholes and headholes. For handholes the gasket
bearing width may be reduced to 10 mm. The total clearance between the door frame and the spigot or recess of
such doors shall not exceed 3 mm, i.e. 1,5 mm all round, and the spigot depth shall be sufficient to trap the gasket.
The selection of the gasket material combined with the design of such doors shall be adequate to provide an
effective and safe sealing assembly.
4.7 Feed lines and protection against feedwater backflow
4.7.1 Each feed line leading to the steam boiler or hot water generator shall be equipped with a protection device
against backflow and a shut-off device. If the shut-off device and the protection device against backflow are not
installed in direct connection to each other, pressure relieving shall be possib
...