Petroleum, petrochemical and natural gas industries - Calculation of heater-tube thickness in petroleum refineries (ISO 13704:2007)

This International Standard specifies the requirements and gives recommendations for the procedures and design criteria used for calculating the required wall thickness of new tubes and associated component fittings for petroleum-refinery heaters. These procedures are appropriate for designing tubes for service in both corrosive and non-corrosive applications. These procedures have been developed specifically for the design of refinery and related process-fired heater tubes (direct-fired, heat-absorbing tubes within enclosures). These procedures are not intended to be used for the design of external piping. This International Standard does not give recommendations for tube retirement thickness; Annex A describes a technique for estimating the life remaining for a heater tube.

Erdöl- und Erdgasindustrie - Berechnung der Wanddicke von Heizrohren in Erdölraffinerien (ISO 13704:2007)

Industries du pétrole, de la pétrochimie et du gaz naturel - Calcul de l'épaisseur des tubes de fours de raffineries de pétrole (ISO 13704:2007)

L'ISO 13704:2007 spécifie les exigences et donne des recommandations pour des méthodes et des critères de conception utilisés pour calculer l'épaisseur de paroi requise de tubes neufs et de raccords composants associés pour les fours de raffineries de pétrole. Ces méthodes sont appropriées pour concevoir des tubes destinés à un service dans des applications corrosives et non corrosives. Ces méthodes ont été développées spécifiquement pour la conception des raffineries et des tubes de fours à brûleurs de procédé associés (à brûleurs directs, tubes absorbant la chaleur au sein d'enceintes).
L'ISO 13704:2007 ne donne pas de recommandations pour l'épaisseur de retrait de tubes, l'Annexe A décrit une technique pour estimer la durée de vie restante d'un tube de four.
Les méthodes données dans l'ISO 13704:2007 ne sont pas prévues pour être utilisées pour la conception de tuyauterie extérieure.

Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina - Izračun debeline grelne cevi v rafinerijah nafte (ISO 13704:2007)

General Information

Status
Published
Publication Date
10-Mar-2009
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
07-Jan-2009
Due Date
14-Mar-2009
Completion Date
11-Mar-2009

RELATIONS

Buy Standard

Standard
SIST EN ISO 13704:2009
English language
112 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 13704:2009
01-april-2009
3HWURNHPLþQDLQGXVWULMDWHULQGXVWULMD]DSUHGHODYRQDIWHLQ]HPHOMVNHJDSOLQD
,]UDþXQGHEHOLQHJUHOQHFHYLYUDILQHULMDKQDIWH ,62
Petroleum, petrochemical and natural gas industries - Calculation of heater-tube
thickness in petroleum refineries (ISO 13704:2007)
Erdöl- und Erdgasindustrie - Berechnung der Wanddicke von Heizrohren in
Erdölraffinerien (ISO 13704:2007)

Industries du pétrole, de la pétrochimie et du gaz naturel - Calcul de l'épaisseur des

tubes de fours de raffineries de pétrole (ISO 13704:2007)
Ta slovenski standard je istoveten z: EN ISO 13704:2007
ICS:
75.180.20 Predelovalna oprema Processing equipment
SIST EN ISO 13704:2009 en

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

---------------------- Page: 1 ----------------------
SIST EN ISO 13704:2009
---------------------- Page: 2 ----------------------
SIST EN ISO 13704:2009
EUROPEAN STANDARD
EN ISO 13704
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2007
ICS 75.180.20
English Version
Petroleum, petrochemical and natural gas industries -
Calculation of heater-tube thickness in petroleum refineries (ISO
13704:2007)

Industries du pétrole, de la pétrochimie et du gaz naturel - Erdöl- und Erdgasindustrie - Berechnung der Wanddicke

Calcul de l'épaisseur des tubes de fours de raffineries de von Heizrohren in Erdölraffinerien (ISO 13704:2007)

pétrole (ISO 13704:2007)
This European Standard was approved by CEN on 3 November 2007.

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

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

standards may be obtained on application to the CEN Management Centre or to any CEN member.

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

under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the

official versions.

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

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

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13704:2007: E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 13704:2009
EN ISO 13704:2007 (E)
Contents Page

Foreword..............................................................................................................................................................3

---------------------- Page: 4 ----------------------
SIST EN ISO 13704:2009
EN ISO 13704:2007 (E)
Foreword

This document (EN ISO 13704:2007) has been prepared by Technical Committee ISO/TC 67 "Materials,

equipment and offshore structures for petroleum and natural gas industries" in collaboration with Technical

Committee CEN/TC 12 “Materials, equipment and offshore structures for petroleum, petrochemical and

natural gas industries” the secretariat of which is held by AFNOR.

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 May 2008, and conflicting national standards shall be withdrawn at the

latest by May 2008.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
Endorsement notice

The text of ISO 13704:2007 has been approved by CEN as a EN ISO 13704:2007 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 13704:2009
---------------------- Page: 6 ----------------------
SIST EN ISO 13704:2009
INTERNATIONAL ISO
STANDARD 13704
Second edition
2007-11-15
Petroleum, petrochemical and natural gas
industries — Calculation of heater-tube
thickness in petroleum refineries
Industries du pétrole, de la pétrochimie et du gaz naturel — Calcul de
l'épaisseur des tubes de fours de raffineries de pétrole
Reference number
ISO 13704:2007(E)
ISO 2007
---------------------- Page: 7 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but

shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In

downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat

accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation

parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In

the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

COPYRIGHT PROTECTED DOCUMENT
© ISO 2007

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
Contents Page

Foreword ............................................................................................................................................................iv

1 Scope......................................................................................................................................................1

2 Terms and definitions ...........................................................................................................................1

3 General design information..................................................................................................................3

3.1 Information required .............................................................................................................................3

3.2 Limitations for design procedures ......................................................................................................4

4 Design.....................................................................................................................................................4

4.1 General ...................................................................................................................................................4

4.2 Equation for stress................................................................................................................................7

4.3 Elastic design (lower temperatures)......................................................................................................7

4.4 Rupture design (higher temperatures) ..................................................................................................8

4.5 Intermediate temperature range ..........................................................................................................8

4.6 Minimum allowable thickness..............................................................................................................8

4.7 Minimum and average thicknesses.....................................................................................................8

4.8 Equivalent tube metal temperature .....................................................................................................9

4.9 Component fittings..............................................................................................................................13

5 Allowable stresses ..............................................................................................................................15

5.1 General .................................................................................................................................................15

5.2 Elastic allowable stress ......................................................................................................................16

5.3 Rupture allowable stress....................................................................................................................16

5.4 Rupture exponent................................................................................................................................16

5.5 Yield and tensile strengths.................................................................................................................16

5.6 Larson-Miller parameter curves.........................................................................................................16

5.7 Limiting design metal temperature....................................................................................................17

5.8 Allowable stress curves......................................................................................................................17

6 Sample calculations............................................................................................................................18

6.1 Elastic design ......................................................................................................................................18

6.2 Thermal-stress check (for elastic range only).....................................................................................19

6.3 Rupture design with constant temperature......................................................................................23

6.4 Rupture design with linearly changing temperature .......................................................................25

Annex A (informative) Estimation of remaining tube life..............................................................................28

Annex B (informative) Calculation of maximum radiant section tube skin temperature ..........................33

Annex C (normative) Thermal-stress limitations (elastic range) .................................................................44

Annex D (informative) Calculation sheets......................................................................................................48

Annex E (normative) Stress curves (SI units)................................................................................................50

Annex F (normative) Stress curves (USC units)............................................................................................70

Annex G (normative) Derivation of corrosion fraction and temperature fraction......................................90

Annex H (informative) Data sources ...............................................................................................................98

Bibliography....................................................................................................................................................103

© ISO 2007 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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

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

ISO 13704 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures

for petroleum, petrochemical and natural gas industries, Subcommittee SC 6, Processing equipment and

systems.

This second edition cancels and replaces the first edition (ISO 13704:2001), which has been technically

revised.
iv © ISO 2007 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 13704:2009
INTERNATIONAL STANDARD ISO 13704:2007(E)
Petroleum, petrochemical and natural gas industries —
Calculation of heater-tube thickness in petroleum refineries
1 Scope

This International Standard specifies the requirements and gives recommendations for the procedures and

design criteria used for calculating the required wall thickness of new tubes and associated component fittings

for petroleum-refinery heaters. These procedures are appropriate for designing tubes for service in both

corrosive and non-corrosive applications. These procedures have been developed specifically for the design

of refinery and related process-fired heater tubes (direct-fired, heat-absorbing tubes within enclosures). These

procedures are not intended to be used for the design of external piping.

This International Standard does not give recommendations for tube retirement thickness; Annex A describes

a technique for estimating the life remaining for a heater tube.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
actual inside diameter
inside diameter of a new tube

NOTE The actual inside diameter is used to calculate the tube skin temperature in Annex B and the thermal stress in

Annex C.
2.2
component fitting
fitting connected to the fired heater tubes
EXAMPLES Return bends, elbows, reducers.

NOTE 1 There is a distinction between standard component fittings and specially designed component fittings; see 4.9.

NOTE 2 Typical material specifications for standard component fittings are ASTM A 234, ASTM A 403 and

ASTM B 366.
2.3
corrosion allowance

additional material thickness added to allow for material loss during the design life of the component

2.4
design life
operating time used as a basis for tube design

NOTE The design life is not necessarily the same as the retirement or replacement life.

© ISO 2007 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
2.5
design metal temperature
tube-metal or skin temperature used for design

NOTE This is determined by calculating the maximum tube metal temperature (T in Annex B) or the equivalent

max

tube metal temperature (T in 2.8) and adding an appropriate temperature allowance (see 2.16). A procedure for

calculating the maximum tube metal temperature from the heat-flux density is included in Annex B. When the equivalent

tube metal temperature is used, the maximum operating temperature can be greater than the design metal temperature.

When the equivalent tube metal temperature is used to determine the design metal temperature, this design metal

temperature is only applicable to the rupture design. It is necessary to develop a separate design metal temperature

applicable to the elastic design. The design metal temperature applicable to the elastic design is the maximum calculated

tube metal temperature among all operating cases plus the appropriate temperature allowance.

2.6
elastic allowable stress
allowable stress for the elastic range
See 5.2.
2.7
elastic design pressure
maximum pressure that the heater coil can sustain for short periods of time

NOTE This pressure is usually related to relief-valve settings, pump shut-in pressures, etc.

2.8
equivalent tube metal temperature

calculated constant metal temperature that in a specified period of time produces the same creep damage as

does a changing metal temperature

NOTE In 4.8 the equivalent tube metal temperature concept is described in more detail. It provides a procedure to

calculate the equivalent tube metal temperature based on a linear change of tube metal temperature from start-of-run to

end-of-run.
2.9
inside diameter

inside diameter of a tube with the corrosion allowance removed; used in the design calculations

NOTE The inside diameter of an as-cast tube is the inside diameter of the tube with the porosity and corrosion

allowances removed.
2.10
minimum thickness
min

minimum required thickness of a new tube, taking into account all appropriate allowances

NOTE See Equation (5).
2.11
outside diameter
outside diameter of a new tube
2 © ISO 2007 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
2.12
rupture allowable stress
allowable stress for the creep-rupture range
See 4.4.
2.13
rupture design pressure

maximum operating pressure that the coil section can sustain during normal operation

2.14
rupture exponent
parameter used for design in the creep-rupture range
NOTE See figures in Annexes E and F.
2.15
stress thickness

thickness, excluding all thickness allowances, calculated from an equation that uses an allowable stress

2.16
temperature allowance

part of the design metal temperature that is included for process- or flue-gas mal-distribution, operating

unknowns, and design inaccuracies

NOTE The temperature allowance is added to the calculated maximum tube metal temperature or to the equivalent

tube metal temperature to obtain the design metal temperature (see 2.5).
3 General design information
3.1 Information required

The design parameters (design pressures, design fluid temperature, corrosion allowance and tube material)

shall be defined. In addition, the following information shall be furnished:
a) design life of the heater tube;

b) whether the equivalent-temperature concept is to be applied and, if so, the operating conditions at the

start and at the end of the run;
c) temperature allowance (see ISO 13705), if any;
d) corrosion fraction (if different from that shown in Figure 1);
e) whether elastic-range thermal-stress limits are to be applied.

If any of items a) to e) are not furnished, use the following applicable parameters:

⎯ design life equal to 100 000 h;

⎯ design metal temperature based on the maximum metal temperature (the equivalent-temperature concept

shall not apply);
© ISO 2007 – All rights reserved 3
---------------------- Page: 13 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
⎯ temperature allowance equal to 15 °C (25 °F);
⎯ corrosion fraction given in Figure 1;
⎯ elastic-range thermal-stress limits.
3.2 Limitations for design procedures

3.2.1 The allowable stresses are based on a consideration of yield strength and rupture strength only;

plastic or creep strain has not been considered. Using these allowable stresses can result in small permanent

strains in some applications; however, these small strains do not affect the safety or operability of heater

tubes.

3.2.2 No considerations are included for adverse environmental effects, such as graphitization,

carburization or hydrogen attack. Limitations imposed by hydrogen attack can be developed from the Nelson

[1]
curves in API 941 .

3.2.3 These design procedures have been developed for seamless tubes. They are not applicable to tubes

that have a longitudinal weld. ISO 13705 allows only seamless tubes.

3.2.4 These design procedures have been developed for thin tubes (tubes with a thickness-to-outside-

diameter ratio, δ /D , of less than 0,15). Additional considerations can apply to the design of thicker tubes.

min o

3.2.5 No considerations are included for the effects of cyclic pressure or cyclic thermal loading.

3.2.6 Limits for thermal stresses are provided in Annex C. Limits for stresses developed by mass, supports,

end connections and so forth are not discussed in this International Standard.

3.2.7 Most of the Larson-Miller parameter referenced curves in 5.6 are not Larson-Miller curves in the

traditional sense but are derived from the 100 000 h rupture strength as explained in Clause H.3.

Consequently, the curves might not provide a reliable estimate of the rupture strength for a design life that is

less than 20 000 h or more than 200 000 h.

3.2.8 The procedures in this International Standard have been developed for systems in which the heater

tubes are subject to an internal pressure that exceeds the external pressure. There are some cases in which a

heater tube can be subject to a greater external pressure than the internal pressure. This can occur, for

example, in vacuum heaters or on other types of heaters during shutdown or trip conditions, especially when a

unit is cooling or draining, forming a vacuum inside the heater tubes. Conditions where external pressures

exceed the internal pressures can govern heater-tube wall thickness. Determination of this (i.e. vacuum

design) is not covered in this International Standard. In the absence of any local or national codes that can

apply, it is recommended that a pressure vessel code, such as ASME VIII (Division 1, UG-28) or EN 13445,

be used, as such codes also address external pressure designs.
4 Design
4.1 General

There is a fundamental difference between the behaviour of carbon steel in a hot-oil heater tube operating at

300 °C (575 °F) and that of chromium-molybdenum steel in a catalytic-reformer heater tube operating at

600 °C (1 110 °F). The steel operating at the higher temperature creeps, or deforms permanently, even at

stress levels well below the yield strength. If the tube metal temperature is high enough for the effects of creep

to be significant, the tube eventually fails due to creep rupture, although no corrosion or oxidation mechanism

is active. For the steel operating at the lower temperature, the effects of creep are non-existent or negligible.

Experience indicates that, in this case, the tube lasts indefinitely, unless a corrosion or an oxidation

mechanism is active.
4 © ISO 2007 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)

Since there is a fundamental difference between the behaviour of the materials at these two temperatures,

there are two different design considerations for heater tubes: elastic design and creep-rupture design. Elastic

design is design in the elastic range, at lower temperatures, in which allowable stresses are based on the

yield strength (see 4.3). Creep-rupture design (which is referred to below as rupture design) is the design for

the creep-rupture range, at higher temperatures, in which allowable stresses are based on the rupture

strength (see 4.4).

The temperature that separates the elastic and creep-rupture ranges of a heater tube is not a single value; it is

a range of temperatures that depends on the alloy. For carbon steel, the lower end of this temperature range

is about 425 °C (800 °F); for type 347 stainless steel, the lower end of this temperature range is about 590 °C

(1 100 °F). The considerations that govern the design range also include the elastic design pressure, the

rupture design pressure, the design life and the corrosion allowance.

The rupture design pressure is never more than the elastic design pressure. The characteristic that

differentiates these two pressures is the relative length of time over which they are sustained. The rupture

design pressure is a long-term loading condition that remains relatively uniform over a period of years. The

elastic design pressure is usually a short-term loading condition that typically lasts only hours or days. The

rupture design pressure is used in the rupture design equation, since creep damage accumulates as a result

of the action of the operating, or long-term, stress. The elastic design pressure is used in the elastic design

equation to prevent excessive stresses in the tube during periods of operation at the maximum pressure.

The tube shall be designed to withstand the rupture design pressure for long periods of operation. If the

normal operating pressure increases during an operating run, the highest pressure shall be taken as the

rupture design pressure.

In the temperature range near or above the point where the elastic and rupture allowable stress curves cross,

both elastic and rupture design equations are to be used. The larger value of δ should govern the design

min

(see 4.5). A sample calculation that uses these methods is included in Clause 6. Calculation sheets (see

Annex D) are available for summarizing the calculations of minimum thickness and equivalent tube metal

temperature.
The allowable minimum thickness of a new tube is given in Table 1.
All of the design equations described in Clause 4 are summarized in Table 2.
© ISO 2007 – All rights reserved 5
---------------------- Page: 15 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
Key
δ =
2σ + p
δ is the corrosion allowance
D is the outside diameter
σ is the rupture allowable stress
p is the rupture design pressure
B = δ /δ
CA σ
Note change of scale at X = 1.
Figure 1 — Corrosion fraction
6 © ISO 2007 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
4.2 Equation for stress

In both the elastic range and the creep-rupture range, the design equation is based on the mean-diameter

equation for stress in a tube. In the elastic range, the elastic design pressure, p , and the elastic allowable

stress, σ , are used. In the creep-rupture range, the rupture design pressure, p , and the rupture allowable

el r
stress ,σ , are used.

The mean-diameter equation gives a good estimate of the pressure that produces yielding through the entire

tube wall in thin tubes (see 3.2.4 for a definition of thin tubes). The mean-diameter equation also provides a

good correlation between the creep rupture of a pressurized tube and a uniaxial test specimen. It is, therefore,

[16], [17], [18], [19]

a good equation to use in both the elastic range and the creep-rupture range . The mean-

diameter equation for stress is as given in Equation (1):
ppʈD ʈD
o i
s = -=11+ (1)
Á˜ Á˜
˯ ˯
22dd
where
σ is the stress, expressed in megapascals [pounds per square inch ];
p is the pressure, expressed in megapascals (pounds per square inch);
D is the outside diameter, expressed in millimetres (inches);

D is the inside diameter, expressed in millimetres (inches), including the corrosion allowance;

δ is the thickness, expressed in millimetres (inches).

The equations for the stress thickness, δ , in 4.3 and 4.4 are derived from Equation (1).

4.3 Elastic design (lower temperatures)

The elastic design is based on preventing failure by bursting when the pressure is at its maximum (that is,

when a pressure excursion has reached p near the end of the design life after the corrosion allowance has

been used up. With the elastic design, δ and δ (see 4.6) are calculated as given in Equations (2) and (3):

σ min
pD p D
el o el i
δ= orδ= (2)
σ σ
22σσ+−pp
el el el el
δ = δ + δ (3)
min σ CA
where

D is the inside diameter, expressed in millimetres (inches), with corrosion allowance removed;

σ is the elastic allowable stress, expressed in megapascals (pounds per square inch), at the design

metal temperature.

1) The unit “pounds per square inch (psi)” is referred to as “pound-force per square inch (lbf/in )” in ISO/IEC 80000.

© ISO 2007 – All rights reserved 7
---------------------- Page: 17 ----------------------
SIST EN ISO 13704:2009
ISO 13704:2007(E)
4.4 Rupture design (higher temperatures)

The rupture design is based on preventing failure by creep rupture during the design life. With the rupture

design, δ and δ (see 4.6) are calculated from Equations (4) and (5):
σ min
pD pD
ro ri
δ= orδ= (4)
σ σ
22σσ+−pp
rr r r
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.