EN 12953-3:2016

SLOVENSKI STANDARD
01-junij-2016
1DGRPHãþD
SIST EN 12953-3:2002
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Shell boilers - Part 3: Design and calculation for pressure parts
Großwasserraumkessel - Teil 3: Konstruktion und Berechnung für drucktragende Teile
Chaudières à tube de fumée - Partie 3: Conception et calcul des parties sous pression
Ta slovenski standard je istoveten z: EN 12953-3:2016
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12953-3
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2016
EUROPÄISCHE NORM
ICS 27.060.30; 27.100 Supersedes EN 12953-3:2002
English Version
Shell boilers - Part 3: Design and calculation for pressure
parts
Chaudières à tubes de fumée - Partie 3: Conception et Großwasserraumkessel - Teil 3: Konstruktion und
calcul des parties sous pression Berechnung für drucktragende Teile
This European Standard was approved by CEN on 23 January 2016.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12953-3:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 8
5 General . 8
5.1 Boilers . 8
5.2 Hot-water boilers . 8
5.3 Main welds . 8
5.4 Weld factor . 9
5.5 Thermal design of furnaces tubes . 9
5.5.1 Design conditions . 9
5.5.2 Furnace dimensions . 11
5.5.3 Heat input . 11
5.5.4 Additional operating conditions . 12
5.6 Dimensions of pressure parts . 12
5.7 Determination of pressures . 12
5.7.1 Maximum allowable pressure . 12
5.7.2 Calculation pressure . 12
5.7.3 Safety valves set pressure . 12
5.7.4 Hydrostatic test pressure . 13
5.8 Allowances . 13
5.8.1 Allowance for material supply tolerances and forming processes . 13
5.8.2 Allowance for metal wastage . 13
5.9 Additional material requirements for plates . 13
5.10 Standardized fittings . 14
5.11 Flanges . 14
5.12 Design by analysis . 14
5.13 Economizer and superheater. 14
6 Calculation temperature and nominal design stress . 14
6.1 Calculation temperature . 14
6.2 Nominal design stress. 15
7 Cylindrical shells . 15
7.1 Shell thickness . 15
7.1.1 Requirements . 15
7.1.2 Required wall thickness including allowances . 16
7.2 Basic calculation subjected to internal pressure . 16
7.3 Boiler supports and lifting lugs . 16
8 Openings and branches in cylindrical shells . 16
8.1 General . 16
8.1.1 Introduction . 16
8.1.2 Requirements for the reinforcement of openings in shells . 16
8.1.3 Effective lengths l for calculation of efficiencies and of compensations. 18
rs
8.1.4 Condition of isolated openings . 22
8.1.5 Requirements for design of branches . 22
8.1.6 Requirements for design of reinforcing pads . 22
8.1.7 General requirements for calculation of cross-sectional and pressure-loaded areas . 23
8.2 Efficiency factor, alternative calculation method, maximum diameter of an un-reinforced
opening . 23
8.2.1 General . 23
8.2.2 Allowable efficiency and maximum diameter of an unreinforced opening . 24
8.2.3 Isolated openings . 24
8.2.4 Adjacent openings . 25
8.3 Design of openings and branches in shells (efficiency and reinforcement) . 25
8.3.1 Symbols and abbreviations . 25
8.3.2 Requirements for application . 26
8.3.3 Design of isolated openings and branch connections . 30
8.3.4 Design of adjacent openings and branch connections . 32
9 Ends . 33
9.1 Unstayed dished heads without openings . 33
9.1.1 Unstayed dished heads under internal pressure . 33
9.1.2 Limiting conditions . 33
9.1.3 Unstayed dished heads under external pressure . 35
9.2 Flat unstayed removable closures . 36
9.3 Unstayed flat plates. 37
10 Supported flat plates, stays and stiffeners . 38
10.1 Breathing space for flat plates . 38
10.2 Stayed flat surfaces . 40
10.2.1 General . 40
10.2.2 Radius of flange . 40
10.2.3 Point of support . 40
10.2.4 Thickness . 41
10.2.5 Values of constant C . 44
10.2.6 Stays for wet back reversal chambers . 54
10.2.7 Stay tubes and bars . 56
10.2.8 Loads on stay tubes and bar stays . 56
10.2.9 Gusset stays. 56
10.2.10 Weld attachments . 58
10.2.11 Additional requirements for set-in end plates . 58
10.2.12 Girder stays supporting the flat section of a reversal chamber . 60
11 Design of isolated openings in boiler flat end plates . 60
11.1 Unreinforced isolated openings . 60
11.2 Branch openings . 60
11.3 Manholes, headholes and handholes . 62
12 Unpierced tubes and tube plates . 63
12.1 Thickness of straight tubes subject to external pressure . 63
12.2 Thickness of straight tubes subject to internal pressure. 64
12.3 Wall thickness and ovality of elbows and tube bends . 64
12.3.1 General . 64
12.3.2 Departure from circularity of the tube bends . 64
12.4 Smoke tubes. 66
12.5 Pitch of tubes . 70
12.6 Thickness of the tube plates within tube nests . 70
13 Furnaces tubes, furnace components and reversal chambers of cylindrical form subject
to external pressure . 71
13.1 Furnaces tubes . 71
13.1.1 Plain furnaces tubes . 71
13.1.2 Corrugated furnaces tubes . 71
13.1.3 Safety factors . 72
13.1.4 Furnace components . 72
13.1.5 Reversal chambers . 72
13.2 Calculation length of composite furnaces tubes . 73
13.3 Tolerances of furnaces tubes. 74
13.4 Stiffeners . 74
13.4.1 General . 74
13.4.2 Stiffener sections made from bar or plate . 75
13.4.3 Stiffeners located within the zone of peak heat flux . 75
13.4.4 Bowling hoops . 75
14 Access and inspection openings . 78
14.1 General requirements . 78
14.2 Types and minimum dimensions of access and inspection openings . 79
14.3 Minimum gasket bearing width and clearance for access and inspection doors . 81
14.4 Access and inspection openings in flat plates . 81
14.5 Requirements for entry area into boilers with a shell outside diameter greater than
1 400 mm . 81
14.6 Accessibility and arrangement of entry and inspection openings . 81
Annex A (informative) Calculation form for “Walker”-type reverse curve sections or
corrugations . 82
Annex B (normative) Furnace calculation temperature . 84
B.1 Calculation of the maximum and the middle furnace wall temperature . 84
Annex C (informative) Calculation of tube plate temperatures . 87
C.1 General . 87
C.2 Symbols . 87
C.3 Calculation method . 88
C.3.1 Radiation coefficients . 88
C.3.2 Convection coefficients . 92
C.3.3 Weighted average gas-side heat transfer coefficient . 95
C.3.4 Tube plate thermal conductance . 97
C.3.5 Water side heat transfer . 98
C.3.6 Tube plate temperatures . 98
C.4 Example of a calculation carried out using the method given in C.3 . 101
C.4.1 Design data assumed . 101
C.4.2 Calculation of radiation coefficient . 102
C.4.3 Calculation of convection coefficients . 102
C.4.4 Calculation of weighted average gas-side heat transfer coefficient . 102
C.4.5 Calculation of tube plate thermal conductance . 102
C.4.6 Calculation of tube plate temperatures . 103
Annex D (normative) Economizer and superheater with water tube design connected to the
shell boiler . 104
D.1 General . 104
D.2 Design of economizer and superheater connected to shell boilers . 104
Annex E (informative) Significant technical changes between this European Standard and the
previous edition . 106
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/68/EU aimed to be covered . 107
Bibliography . 108

European foreword
This document (EN 12953-3:2016) has been prepared by Technical Committee CEN/TC 269 “Shell and wa-
ter-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 2016, and conflicting national standards shall be with-
drawn at the latest by November 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12953-3:2002.
This document has been prepared under a mandate given to CEN by the European Commission and the Eu-
ropean Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document.
The informative Annex E lists the significant technical changes between this European Standard and the pre-
vious edition.
EN 12953, Shell boilers, consists of the following parts:
— Part 1: General
— Part 2: Materials for pressure parts of boilers and accessories
— Part 3: Design and calculation for pressure parts
— Part 4: Workmanship and construction of pressure parts of the boiler
— Part 5: Inspection during construction, documentation and marking of pressure parts of the boiler
— Part 6: Requirements for equipment for the boiler
— Part 7: Requirements for firing systems for liquid and gaseous fuels for the boilers
— Part 8: Requirements for safeguards against excessive pressure
— Part 9: Requirements for limiting devices of the boiler and accessories
— Part 10: Requirements for feedwater and boiler water quality
— Part 11: Acceptance tests
— Part 12: Requirements for grate firing systems for solid fuels for the boiler
— Part 13: Operating instructions
— (CR 12953) Part 14: Guideline for involvement of an inspection body independent of the manufacturer
Although these parts can be obtained separately, it should be recognized that the parts are interdependent.
As such, the design and manufacture of shell boilers requires the application of more than one part in order
for the requirements of the standard to be satisfactorily fulfilled.
NOTE A “Boiler Helpdesk” has been established in CEN/TC 269 which may be contacted for any questions regard-
ing the application of the European Standards series EN 12952 and EN 12953, see the following website:
http://www.boiler-helpdesk.din.de
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portu-
gal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
1 Scope
This Part of this European Standard specifies requirements for the design and calculation of pressure parts
of shell boilers as defined in EN 12953-1.
For other components such as water tube walls reference should be made to EN 12952 series.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indis-
pensable 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 1092-1:2007+A1:2013, Flanges and their joints — Circular flanges for pipes, valves, fittings and accesso-
ries, PN designated — Part 1: Steel flanges
EN 10160, Ultrasonic testing of steel flat product of thickness equal or greater than 6 mm (reflection method)
EN 12952-3:2011, Water-tube boilers and auxiliary installations — Part 3: Design and calculation for pressure
parts of the boiler
EN 12953-1:2012, Shell boilers — Part 1: General
EN 12953-2:2012, Shell boilers — Part 2: Materials for pressure parts of boilers and accessories
EN 12953-4:2002, Shell boilers — Part 4: Workmanship and construction of pressure parts of the boiler
EN 12953-5, Shell boilers — Part 5: Inspection during construction, documentation and marking of pressure
parts of the boiler
EN 12953-6:2011, Shell Boilers — Part 6: Requirements for equipment for the boiler
EN 12953-10:2003, Shell boilers — Part 10: Requirements for feedwater and boiler water quality
EN 13445-3:2014, Unfired pressure vessels — Part 3: Design
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12953-1:2012, EN 12953-6:2011
and the following apply.
3.1
branch
nozzle, stub, stand pipe
3.2
cold start
starting the boiler from ambient pressure at room temperature to normal operating condition
3.3
warm start
starting the boiler from the hot stand-by condition
3.4
seam
generic term for welded joints, welded seams or welds
4 Symbols and abbreviations
For the purposes of this standard, the symbols given in EN 12953-1:2012, Table 1 shall apply. Throughout
this standard, additional terminology and symbols have been included where necessary to meet the re-
quirements of the specific text concerned. It should also be noted that in some clauses the same additional
symbol is used in different formulas to represent different terms. However, in all such cases, the special
meaning of each symbol is indicated for each formula.
5 General
5.1 Boilers
The requirements in this standard shall apply to boilers as defined in EN 12953-1:2012 designed throughout
under the conditions specified herein and which are to be operated under normal operation conditions, with
feedwater and boiler water in accordance with EN 12953-10:2003, and under adequate supervision.
Where there are specified operation conditions such as e.g. severe cyclic service, this shall be taken into ac-
count in the design process.
The feed water entering a steam boiler or the return water entering a hot water boiler shall not impinge di-
rectly on the furnace.
No load cycle calculation shall be carried out if all the following requirements are satisfied:
a) The number of start-ups from zero pressure to the foreseen operating pressure (full pressure cycles)
is ≤ 1000;
b) For material with specified yield strength at room temperature ≤ 295 MPa the number of partial pres-
sure cycles in the range of ΔP = 20 % of PS is ≤ 100 000 or, alternatively, in the range of ΔP = 40 % of PS
is ≤ 10 000;
c) For material with specified yield strength at room temperature > 295 MPa the number of partial pres-
sure cycles in the range of ΔP = 10 % of PS is ≤ 100 000 or, alternatively, in the range of ΔP = 20 % of PS
is ≤ 10 000;
d) The weld for set-in end plates to shell and/or to furnace shall be at least 10 % UT tested during con-
struction.
Otherwise if the load cycle situation is more complicated a load cycle calculation shall be performed.
The requirements for the load cycle calculation are not applicable for the weld factor 0,7 (see 5.4).
5.2 Hot-water boilers
For directly fired hot-water boilers the difference between the outlet temperature and the inlet temperature
should not exceed 50 K. If the difference between these two temperatures is greater than 50 K, either inter-
nal or external mixing devices shall be used to limit the differential temperature within the boiler to 50 K.
The difference between the saturation temperature corresponding to the maximum operating pressure, and
the outlet temperature, should not normally exceed 80 K. If the difference is greater than 80 K, the distances
in accordance with 10.1 shall be increased by 50 %. Furthermore the maximum heat input in accordance
with Figure 1 shall be reduced by 20 %.
5.3 Main welds
The types of weld used in the design of the boiler shall be in accordance with EN 12953-4.
Non-destructive testing (NDT) shall be in accordance with the requirements of EN 12953-5. The design of
the weld joints shall be such that the required NDT can be carried out.
5.4 Weld factor
The weld factors v used in the calculation of the pressure parts shall be either 1 or 0,85 or 0,7 depending on
the extent of NDT.
The extent of NDT shall be in accordance with EN 12953-5.
A welding efficiency v = 0,7 is only acceptable, if an increased test pressure is used as given by Formula (1):
R
e + c
p0,220
cs 2
p 2,2 p ⋅ (1)
tc
Re
p0,2 tc cs
5.5 Thermal design of furnaces tubes
5.5.1 Design conditions
Burners with a fixed firing rate (also called on/off or single stage burners) shall not be used for heat inputs
exceeding 1 MW per furnace.
Combustion shall be completed in the furnace.
Calculation temperature shall be in accordance with 6.1 e).
In order to ensure safe burner/boiler combinations with a heat input more than 2 MW, the minimum diame-
ter of the furnace di shall not be less than the following values (see Figure 1):
a) No 1 Material grade P265GH/P295GH: Coal firing (grate): d = 400 + 175 * H
i
b) No 2 Material grade P265GH: Oil firing: d = 365 + 117 * H Gas firing: d = 365 + 90,4 * H
i i
c) No 3 Material grade P295GH/P355GH: Oil firing: d = 450 + 75 * H Gas firing: d = 450 + 57,7 * H
i i
where:
d = inner diameter in mm for plain furnaces (with or without stiffeners or bowling hoops) or average diame-
i
ter mm for corrugated furnaces (with or without stiffeners);
H = heat input in MW (product of the fuel flow rate and the lower calorific value; air preheating should be
taken into account if the air temperature is greater than 100 °C).
=
Key
1 coal firing P265GH/P295GH
2 P265GH
3 P295GH / P355GH
d inner diameter for plain furnaces (with or without stiffeners or bowling hoops) or average diameter for
i
corrugated furnaces (with or without stiffeners) [mm]
X1 heat input H / H [MW]
oil coal
X2 heat input H [MW]
gas
temperature monitoring necessary if d > 1800 mm
i
temperature monitoring necessary if H > 14 MW respectively, H > 18,2 MW
oil gas
monitoring of operation conditions if d > 1433 mm
i
Figure 1 — Relation between heat input and inside diameter of the furnace d
i
Key
Y minimum furnace tube length [mm]
X heat input [MW]
Figure 2 — Relation between heat input and length of the furnace L
5.5.2 Furnace dimensions
The minimum furnace length shall be determined either by using the Figure 2 or the Formula (2):
0.5
L [mm] = 150000 * (H [MW] / 10100) (2)
If the furnace diameter is less than the minimum diameter (see Figure 1) or the furnace length is less than
the min req. length (see Figure 2) the following conditions shall be fulfilled:
— Verification of heat flux and calculation temperature of furnace (e.g. according to 6.1 e)). Lower calcula-
tion temperatures than in Formula 12 shall not be used.
— Continuous monitoring of water quality (see EN 12953-6:2011, 4.8.2, 4.8.3 and 4.8.4)
If the furnace diameter is greater than 1800 mm the following conditions shall be fulfilled:
— A separate stress analysis of the furnace (e.g. by a suitable FEA calculation) is necessary to prove the fac-
tor of safety against deformation and rupture
5.5.3 Heat input
If the heat input is more than H = 18,2 MW / H = 14 MW the following conditions shall be fulfilled:
gas oil
— Verification of heat flux and calculation temperature of furnace (e.g. according to 6.1 e).
— The design documentation demonstrates satisfactory integration of the burner with the boiler and the
operating instructions contain the full specification details for the boiler/burner combination.
5.5.4 Additional operating conditions
For H > 18,2 MW/H >14 MW, the boiler manufacturer shall consider additional operating requirements
gas oil
as follows. The risk analysis shall be adapted accordingly:
More stringent operating conditions specified such as improved water quality requirements in addition to
the requirements of EN 12953-10:2003, shorter maintenance and/or inspection intervals.
— Temperature monitoring of the furnace shell or equivalent safety / technical measures, if required ac-
cording to Figure 1.
— More stringent start up conditions, e.g. limitation of the heating rate in the cold start (either automatical-
ly within the control system or in the operating instructions) as determined from the boiler/burner
integration evaluation.
— Twin furnace boiler: requirements for possible single furnace operation, where the operating
requirements necessitate a wide range of heat input.
a) For steam boilers:
— Monitoring of the conductivity of the boiler water shall be in accordance with EN 12953-6:2011.
— Improvement in the circulation during start-up.
b) For hot water boilers:
— Monitoring of the make-up water shall be in accordance with EN 12953-6:2011 as well as the moni-
toring of the returns for contamination.
— Reliable monitoring of returns for sudden changes in flow rate or temperature.
Where refractory is attached to the furnace shell, the length shall not be longer than one third of the inside
diameter of the furnace. The length is defined as starting from the end of the burner. Further refractory or
other internals in the furnace for the purpose of storing or retaining heat are not permitted except where
they are in accordance with the specification of the burner manufacturer.
5.6 Dimensions of pressure parts
The wall thickness and other dimensions of pressure parts shall be sufficient to withstand the calculation
pressure at calculation temperature and shall be determined in accordance with this Part of the European
Standard.
5.7 Determination of pressures
5.7.1 Maximum allowable pressure
The maximum allowable pressure PS is the maximum pressure for which the boiler is designed and shall be
measured at the highest point of the boiler.
5.7.2 Calculation pressure
The calculation pressure p shall be not less than the sum of the maximum allowable pressure and the hy-
c
drostatic head. If the latter is less than 3 % of the maximum allowable pressure, the effect of hydrostatic
head may be ignored.
NOTE Calculation pressure p is also referred to as design pressure p . The term calculation pressure p is used
c d c
throughout this European Standard.
5.7.3 Safety valves set pressure
The safety valve(s) set pressure shall not exceed the maximum allowable pressure (see also
EN 12953-8:2001).
5.7.4 Hydrostatic test pressure
The standard hydrostatic test pressure shall be not less than that given by Formula (3):
R
p0,220
pp= 1,25 (3)
t c
R
p0,2 tc
or
pp= 1,43 (4)
tc
whichever is the higher;
where
R is the specified value of the yield point at 20 °C;
p0,2 20
R see EN 12953-1:2012, Table 1.
p0,2 tc
The highest ratio of R /R shall be taken for the boiler shell and front tube plate (or front plate
p0,2 20 p0,2 tc
depending on the configuration) and rear plate (or rear tube plate depending on the configuration) at their
calculation temperatures.
In all cases:
a) The stress in all pressure parts of the boiler and/or the boiler assembly shall not exceed 95 % of their
specified yield strength at test temperature;
b) p shall not exceed the calculation pressure for the furnace under test conditions (see 13.1). The value of
t
modulus of elasticity (E) at room temperature shall be used.
c) For boilers with smoke tubes that are expanded only, the value of p = 1,43 p shall be used.
t c
5.8 Allowances
5.8.1 Allowance for material supply tolerances and forming processes
The minus tolerance on the ordered nominal wall thickness c is to compensate for minus tolerances
resulting from the supply condition of the material.
For subsequent forming processes, the minimum thickness that shall be achieved by the supplier or manu-
facturer shall be at least the minimum thickness specified in the relevant documents (i.e. drawings, calcula-
tion sheets, etc.).
5.8.2 Allowance for metal wastage
For the purpose of design, allowance for metal wastage c shall include corrosion and also erosion and abra-
sion if these effects are expected to occur.
For components working under normal conditions:
a) wall thickness ≤ 30 mm a minimum wastage allowance of 0,75 mm shall be taken;
b) wall thickness > 30 mm and for all flat components, a wastage allowance of 0 mm may be used.
In the case of severe wastage conditions an increased c value shall be selected accordingly.
5.9 Additional material requirements for plates
UT tests according to EN 10160 shall be performed for plates ≥ 30 mm.
5.10 Standardized fittings
If standardized fittings (e.g. elbows, tubes bends, etc.) according to EN 10253-2 are used, additional calcula-
tion according to EN 12953-3 is not required.
NOTE Alternative standards may be used and should comply with requirements of the specific EN standards.
5.11 Flanges
If flanges according to EN 1092-1:2007+A1:2013 are used, pressure/temperature ratings (p/t) given in
EN 1092-1:2007+A1:2013, Annex G shall be used.
NOTE Alternative standards may be used and should comply with requirements of the specific EN standards.
5.12 Design by analysis
It shall be permissible to design by analysis provided the safety and functional requirements of the compo-
nents are not impaired. The results of any stress calculations carried out for loadings not explicitly covered
by equations in this part of this standard shall be determined by using the criteria given in EN 13445-3:2014.
5.13 Economizer and superheater
For economizer and superheater with water tube design, which are connected to the shell boiler, see An-
nex D.
6 Calculation temperature and nominal design stress
6.1 Calculation temperature
The calculation tempe
...