AD 2000-Merkblatt

Supersedes May 2007 edition; I = Amendments to previous edition

AD 2000-Merkblätter are protected by copyright. The rights of use, particularly of any translation, reproduction, extract of figures, transmission byphotomechanical means and storage in data retrieval systems, even of extracts, are reserved to the author. Beuth Verlag has taken all reasonablemeasures to ensure the accuracy of this translation but regrets that no responsibility can be accepted for any error, omission or inaccuracy. In cases ofdoubt or dispute, the latest edition of the German text only is valid.

ICS 23.020.30 November 2008 edition

The AD 2000-Merkblätter are prepared by the seven associations listed below who together form the “Arbeitsgemeinschaft Druckbehälter”(AD). The structure and the application of the AD 2000 Code and the procedural guidelines are covered by AD 2000-Merkblatt G 1.

The AD 2000-Merkblätter contain safety requirements to be met under normal operating conditions. If above-normal loadings are to beexpected during the operation of the pressure vessel, this shall be taken into account by meeting special requirements.

If there are any divergences from the requirements of this AD 2000-Merkblatt, it shall be possible to prove that the standard of safety ofthis Code has been maintained by other means, e.g. by materials testing, tests, stress analysis, operating experience.

Fachverband Dampfkessel-, Behälter- und Rohrleitungsbau e.V. (FDBR), Düsseldorf

Deutsche Gesetzliche Unfallversicherung (DGUV), Berlin

Verband der Chemischen Industrie e.V. (VCI), Frankfurt/Main

Verband Deutscher Maschinen- und Anlagenbau e.V. (VDMA), Fachgemeinschaft Verfahrenstechnische Maschinenund Apparate, Frankfurt/Main

Stahlinstitut VDEh, Düsseldorf

VGB PowerTech e.V., Essen

Verband der TÜV e.V. (VdTÜV), Berlin

The above associations continuously update the AD 2000-Merkblätter in line with technical progress. Please address any proposals forthis to the publisher:

Verband der TÜV e.V., Friedrichstraße 136, 10117 Berlin.____________

Design of pressure vessels Design of pressure vessels AD 2000-Merkblatt

B 0

Contents

0 ForewordThe AD 2000 Code can be applied to satisfy the basic safetyrequirements of the Pressure Equipment Directive, princi-pally for the conformity assessment in accordance withmodules “G” and “B + F”.

The AD 2000 Code is structured along the lines of a self-contained concept. If other technical rules are used in ac-cordance with the state of the art to solve related problems,it is assumed that the overall concept has been taken intoaccount.

The AD 2000 Code can be used as appropriate for othermodules of the Pressure Equipment Directive or for differentsectors of the law. Responsibility for testing is as specifiedin the provisions of the relevant sector of the law.

1 Scope1.1 The B and S series of AD 2000-Merkblätter deal withdesign rules for pressure-bearing components of pressurevessels. Their application assumes that the W and HP se-ries of AD 2000-Merkblätter as well as current engineering

practice have been taken into consideration for the selectionof the materials and their processing. See also AD 2000-Merkblatt G 1.

1.2 The B and S 3 series of AD 2000-Merkblätter apply topredominantly static stresses. AD 2000-Merkblätter S 1 andS 2 also apply to alternating stresses.

2 General2.1 This AD 2000-Merkblatt includes the fundamentalrules which are common to the B and S series of AD 2000-Merkblätter. The other B and S series AD 2000-Merkblättercan therefore only be used in conjunction with this AD 2000-Merkblatt.

2.2 Where the AD 2000-Merkblätter do not give designrules for pressure-bearing parts, then, in each individualcase, proof shall be provided by the application of otherrules or design methods, strain measurements, relevant op-erating experience gained etc. that the components are notoverstressed taking into due account material and serviceconditions.

0 Foreword1 Scope2 General3 Symbols and units4 Design pressure5 Design temperature

6 Design strength value7 Safety factor8 Use of the permissible design

stress level in joints9 Allowances

10 Minimum wall thickness

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2.3 The AD-Merkblätter contain safety requirements oblig-atory for normal operating conditions. Whenever excessive-ly high stresses are expected in the operation of pressurevessels, special conditions shall be satisfied to meet theserequirements.

2.4 If there are deviations from the requirements of theAD 2000-Merkblätter, it shall be capable of being proventhat the technical safety standard laid down in this Code isstrictly adhered to in another way, e.g. by materials testing,tests, stress analysis and operating experience.

3 Symbols and unitsa lever arm mm

b width mm

c1 allowance for minus thickness tolerance mm

c2 wear allowance mm

d diameter of an opening, flange, screw etc. mm

da outside diameter of a tube, nozzle, flange mm

di inside diameter of a tube, nozzle, flange mm

dt pitch diameter mm

dD average gasket diameter mm

e wide side of rectangular or elliptical plate mm

f narrow side of rectangular or elliptical plate mm

g weld thickness mm

h height mm

k0 setting characteristic of gasket mm

k1 service characteristic of gasket mm

l length mm

n number –

p design pressure bar

PS maximum allowable pressure bar

PT test pressure bar

r generally radius, e.g. transition radius mm

s required wall thickness including allowances mm

se actual wall thickness mm

v factor indicative of the use of the allowabledesign stress in joints or factor allowingfor weakening –

x decay-length zone mm

A area mm2

C, b design factors –

D shell diameter mm

Da outside diameter e.g. of a cylindrical shell mm

Di inside diameter e.g. of a cylindrical shell mm

E modulus of elasticity at designtemperature N/mm2

F force N

I planar moment of inertia mm4

K design strength value atdesign temperature N/mm2

KD dimensional stability of sealant atroom temperature N/mm2

K20 design strength value at 20 °C N/mm2

M moment N mm

R radius of curvature mm

S safety factor at design pressure –

S´ safety factor at test pressure –

SD leak safety factor –

SK safety factor against elastic cupping atdesign pressure –

S'K safety factor against elastic cupping attest pressure –

SL safety factor on the permissible numberof load cycles –

W section modulus mm3

Z auxiliary value –

v Poisson’s ratio –

s stress N/mm2

u, T temperature °C

4 Design pressure

4.1 Generally, the design is based on the maximum allow-able pressure (PS) and the test pressure (PT). The designpressure p used in the following AD 2000-Merkblätter shallbe ≥ the maximum allowable pressure (PS). The static pres-sures caused by the contents of the vessel during serviceand testing need not be taken into account as long as theydo not increase the stress to the wall by more than 5%.1)

4.2 If a pressure-bearing wall is subject to pressure onboth sides at the same time, the design shall generally notbe based on the pressure difference. The design shall con-sider both pressures separately. Exceptions are permissibleas long as proof has been provided that a higher stress can-not occur in the wall than that due to the pressure difference.

4.3 If a pressure-bearing wall is subject to pressure andvacuum at the same time, the design pressure is equal tothe pressure difference. This applies also to the determina-tion of the test pressure. If there is no reliable limitation ofthe vacuum, the design pressure shall be the actual pres-sure increased by 1 bar.

4.4 At the test pressure, the allowable stresses formedfrom the design strength value at test temperature and thesafety factor S´ in Tables 2 and 3 shall not be exceeded.

4.5 Additional static loads shall be given in the drawing ifthese increase the stress in the vessel wall by more than5 % (e.g. due to supports, wind, snow and brick linings2)).

A structural analysis shall be carried out if the additionalstatic loads influence the design of the pressure vessel sig-nificantly. It has been found that increases in stress due toadditional loads can be expected if the criteria in the S 3 se-ries of AD 2000-Merkblätter apply.

1) Example: maximum allowable pressure = 2 barheight of vessel = 5 mcontents: waterp = 2 + 0,5 – 0,05 · 2 = 2,4 bar

2) See DIN 28060

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5 Design temperature5.1 The selection of the material and the determination ofthe design strength value depend on the maximum wall tem-perature that can be expected at the maximum allowablepressure (PS) in each case. This is derived from the allow-able working temperature (corresponding to the maximumallowable temperature (TS) in accordance with the PED)plus an allowance for the particular type of heating and is re-ferred to as the design temperature. For unheated walls, themaximum working temperature may be used for this. Forheated walls, it can generally be determined from Table 1;otherwise e.g. in the case of brick linings, it shall be deter-mined by calculation or measurement.

The requirements of Table 1 in 4.2 of AD 2000-Merkblatt S 6shall be noted in the water steam, steam and superheatedsteam range.

5.2 AD 2000-Merkblatt S 6 shall be applied if, as a resultof the design temperature, the creep range limit temperatureis attained or exceeded for the particular material. The limittemperatures shall be taken from the relevant materialstandards or material specifications.

5.3 If the maximum expected wall temperature duringservice is below +20 °C, the design temperature is +20 °C.For working temperatures below –10 °C, see also AD 2000-Merkblatt W 10. When determining the wall temperature,the ambient temperature and the working temperature shallbe taken into account (operating instructions/risk analysis).

Table 1. Design temperatures

6 Design strength value6.1 The design strength values K shall be selected for thedesign temperature requirements in the W series of theAD 2000-Merkblätter.

6.2 Requirements for time-dependent design strength val-ues are contained in 4.3 of AD 2000-Merkblatt S 6.

6.3 For materials with no guaranteed yield point or proofstress, the guaranteed minimum tensile strength at the de-sign temperature shall be used as the design strength value.In this case, the safety factors of Table 3 shall be used.

6.4 Where joints are made by dissimilar types of welds,the design strength values of the weld metal shall be thebasis for the design if they are lower than those of the basematerial.

6.5 Higher design strength values due to work-hardeningshall be used in the design only if they have been provedand are present in the finished component.

7 Safety factorThe safety factors shall be taken from Tables 2 and 3 unlessdiffering or additional data are given in the individualAD 2000-Merkblätter.

8 Use of the permissible design stress level in joints

8.1 The use of the permissible design stress in the weld istaken into account in the design by factor v. This results fromdividing the values for the use of the permissible designstress level given in summary Table 1 in AD 2000-MerkblattHP 0 by 100. If no other values are specified for the un-named materials in the agreement required according to 1.2of AD 2000-Merkblatt HP 0, v = 1,0 shall be used.

8.2 For brazed joints, v = 0,8 may be applied provided alower value has not been specified in the welding proceduretest.

8.3 Soldered longitudinal joints are not permissible.Lapped soldered circumferential joints between copperparts are acceptable provided the lapping is at least 10 se upto a wall thickness of 6 mm and up to Da · p ≤ 2500 mm bar.In this case, v = 0,8 shall be used for the circumferentialseam.

8.4 For soldered joints between copper plates with a con-tinuous strap of width ≥ 12 se on both sides of the joint, wallthickness se ≤ 4 mm and an allowable working pressure≤ 2 bar, v = 0,8 can be used.

9 Allowances

9.1 Allowances to compensate for minus wallthickness tolerances

9.1.1 For ferritic steels, the minus tolerance permitted inthe relevant dimensional standards shall be used as the al-lowance c1 in the design where this can occur on the fin-ished component.

9.1.2 In the case of austenitic steels and non-ferrous met-als, minus tolerances are not taken into account only whenthere is static loading due to internal pressure. For austeniticsheets in conjunction with DIN EN 10029 as the dimensionalstandard, this only applies to minus tolerances up to the val-ues of the allowance below nominal size for class A, i.e.when using sheets with greater minus tolerances, only thedifference from class A shall be taken into account.

9.1.3 Where the manufacturing process involves reduc-tions in wall thickness (e.g. in the case of cast or deep-drawn components), the required wall thickness calculatedwith c1 = 0 shall be stated and clearly marked on the draw-ing.

9.2 Wear allowance

9.2.1 For ferritic steels, the wear allowance c2 = 1 mm. Itmay be omitted for se ≥ 30 mm or if the steel is adequatelyprotected against the contents e.g. by means of lining withlead, cladding, rubber or plastics coatings, but not by elec-troplating. In the case of lining with plastics, the suitability ofthe plastics shall always be verified.

Type of heating Design temperature

by gases, steam or liquids

the maximum temperature of the heating medium

by fire, exhaust gas or electrical equipment3)

in the case of protected walls, the maximum working temperature plus 20 K

in the case of directly heated walls, the maximum working temperature plus 50 K

3) Not applicable for indirect electrical heating (e.g. by means of oilbath)

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Table 2. Yield point, proof stress or creep rupture strengt safety factors

Table 3. Tensile strength safety factors

9.2.2 As a deviation from 9.2.1, a greater allowance c2shall be agreed upon between manufacturer and user if thecontents of the vessel are severely corrosive or if the insideof the vessel cannot be examined during subsequent ser-vice. In these cases, the allowance c2 shall be stated in thedrawing.

With certain corrosive effects, it may be necessary, in addi-tion to using suitable materials and adequate design, to re-duce the stress in the walls under tensile stress that are incontact with the vessel contents, in order to avoid destruc-tion of protective coatings or stress corrosion cracking, forexample.

9.2.3 For austenitic steels and non-ferrous metals, thewear allowance is generally c2 = 0, provided no higher wearallowance has been agreed between manufacturer and userwhich then shall be stated in the drawing.

10 Minimum wall thickness10.1 The minimum wall thicknesses specified in the B se-ries of AD 2000-Merkblätter are nominal wall thicknesseswhich the finished component shall have as a nominal di-mension.

10.2 As a deviation from 10.1, the minimum wall thick-nesses may be smaller provided that:

a) this is required by the process or the operating condi-tions,

b) the dimensional stability of the pressure vessel is notadversely affected and

c) the manufacturing conditions are suitable for this.

Material and type

Safety factor S for materialat design

temperature

Safety factor S´at test pressure

1. Rolled and forged steels 1,5 1,05

2. Cast steel 2,0 1,4

3. Spheroidal graphite cast iron to DIN EN 1563

3.1 EN-GJS-700-2/2UEN-GJS-600-3/3U

5,0 2,5

3.2 EN-GJS-500-7/7U 4,0 2,0

3.3 EN-GJS-400-15/15U 3,5 1,7

3.4 EN-GJS-400-18/18U-LTEN-GJS-350-22/22U-LT

2,4 1,2

4. Aluminium and aluminium alloys – wrought materials

1,5 1,05

Material and type

Safety factor S for materialat design

temperature

Safety factor S´at test pressure

1. Grey cast iron toDIN EN 1561

3,5

1.1 non-annealed 9,0

1.2 annealed or enameled 7,0

2. Copper and copper alloys including rolled and cast bronze

2,5

2.1 for seamless and welded vessels

3,5

2.2 for soldered vessels 4,0

Publisher: Source of supply:

Beuth Verlag GmbH10772 BerlinTel. 030/26 01-22 60Fax 030/26 01-12 60info@beuth.dewww.beuth.de

Verband der TÜV e.V.

E-Mail: berlin@vdtuev.dehttp://www.vdtuev.de

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