EN 13084-1:2007

Free-standing chimneys - Part 1: General requirements

This European Standard deals with the general requirements and the basic performance criteria for the design and construction of all types of free standing chimneys including their liners. A chimney may also be considered as free standing, if it is guyed or laterally supported or if it stands on another structure.
Chimneys attached to buildings should be considered as free-standing chimneys in accordance with this European Standard when at least one of the following criteria is met:
   the distance between the lateral supports is more than 4 m;
   the free-standing height above the uppermost structural attachment is more than 3 m;
   the free-standing height above the uppermost structural attachment for chimneys with rectangular cross section is more than five times the smallest external dimension;
   the horizontal distance between the building and the outer surface of the chimney is more than 1 m.
Chimneys attached to free-standing masts are considered as free-standing chimneys.
The structural design of free-standing chimneys takes into account operational conditions and other actions to verify mechanical resistance and stability and safety in use. Detailed requirements relating to specialized designs are given in the standards for concrete chimneys, steel chimneys and liners.
NOTE   In other parts of the series EN 13084 rules will be given where chimney products in accordance with EN 1443
(and the relating product standards) may be used in free-standing chimneys.

Freistehende Schornsteine - Teil 1: Allgemeine Anforderungen

Die vorliegende Europäische Norm behandelt die allgemeinen Anforderungen und die Grundkriterien für Entwurf, Berechnung und Konstruktion aller Arten von freistehenden Schornsteinen, einschließlich deren Innenrohre. Ein Schornstein kann auch dann als freistehend betrachtet werden, wenn er abgespannt oder seitlich abgestützt ist oder auf einem anderen Bauwerk steht.
An einem Gebäude seitlich abgestützte Schornsteine sind im Sinne dieser Europäischen Norm als freistehende Schornsteine zu betrachten, wenn mindestens eines der folgenden Kriterien erfüllt ist:
-   der Abstand zwischen den seitlichen Abstützungen ist größer als 4 m;
-   die freistehende Höhe über der obersten statisch wirksamen Abstützung ist größer als 3 m;
-   die freistehende Höhe über der obersten statisch wirksamen Abstützung bei Schornsteinen mit einem rechtwinkligen Querschnitt beträgt mehr als das fünffache des kleinsten Außenmaßes;
-   der horizontale Abstand zwischen dem Gebäude und der Außenfläche des Schornsteines ist größer als 1 m.
An freistehenden Masten befestigte Schornsteine werden als freistehende Schornsteine betrachtet.
Die Bemessung von freistehenden Schornsteinen berücksichtigt die Betriebsbedingungen und sonstige Einwir¬kungen, um die mechanische Festigkeit, Standsicherheit und Nutzungssicherheit nachzuweisen. Detaillierte Anforderungen bezüglich der einzelnen Konstruktionsarten werden in den Normen für Beton¬schornsteine, Stahlschornsteine und Innenrohre gegeben.
ANMERKUNG   Regeln für die Verwendung von Schornsteinprodukten nach EN 1443 (und der damit verbundenen Produktnormen) in freistehenden Schornsteinen werden in anderen Teilen von EN 13084 angegeben.

Cheminées autoportantes - Partie 1 : Exigences générales

La présente Norme européenne traite des exigences générales et des critères de performances fondamentaux concernant la conception et la réalisation de tous les types de cheminées autoportantes y compris leur paroi intérieure. Il est permis de considérer une cheminée comme étant autoportante si elle est haubanée ou soutenue ou si elle repose sur une autre structure.
Les cheminées attachées aux bâtiments doivent être considérées comme cheminées autoportantes si au moins un des critères suivants est satisfait :
   la distance entre les supports latéraux est supérieure à 4 m ;
   la hauteur autoportante au-dessus du support constructif est supérieure à 3 m ;
   la hauteur autoportante au-dessus du support constructif des cheminées de section transversale rectangulaire est plus de cinq fois supérieure à la dimension extérieure la plus petite ;
   la distance horizontale entre le bâtiment et la surface extérieure de la cheminée est supérieure à 1 m.
Les cheminées attachées aux poteaux autoportants sont considérées comme cheminées autoportantes.
Le calcul des cheminées autoportantes prend en considération les conditions d’opération et d’autres effets pour vérifier la résistance mécanique, la stabilité et la sécurité d’utilisation. Les exigences détaillées concernant les types de construction particuliers sont données dans les normes pour cheminées en béton, cheminées en acier et parois intérieures.
NOTE   Les règles pour l’utilisation des produits de cheminées selon l’EN 1443 (et les normes de produit respectives) dans les cheminées autoportantes seront données dans les autres parties de la série EN 13084.

Prostostoječi dimniki - 1. del: Splošne zahteve

General Information

• Status: Withdrawn
• Publication Date: 27-Feb-2007
• Withdrawal Date: 13-Apr-2025
• ICS: 91.060.40 - Chimneys, shafts, ducts
• Technical Committee: CEN/TC 297 - Free-standing industrial chimneys
• Drafting Committee: CEN/TC 297/WG 1 - General requirements
• Current Stage: 9960 - Withdrawal effective - Withdrawal
• Start Date: 08-Jan-2025
• Completion Date: 14-Apr-2025
• Directive: 305/2011 - Regulation (eu) No 305/2011 of the European Parliament and of the Council of 9 march 2011 laying down harmonised conditions for the marketing of construction products and repealing council directive 89/106/eec
• Directive: 89/106/EEC - Construction products
• Mandate: M/105 - Mandate to CEN/CENELEC concerning the execution of standardization work for harmonized standards on chimneys, flues and specific products
• Ref Project: SIST EN 13084-1:2007 - Free-standing chimneys - Part 1: General requirements

Relations

• Replaces: EN 13084-1:2000 - Free-standing industrial chimneys - Part 1: General requirements
• Effective Date: 22-Dec-2008
• Replaces: EN 13084-1:2000/AC:2005 - Free-standing chimneys - Part 1: General requirements
• Effective Date: 22-Dec-2008
• Replaced By: EN 13084-1:2025 - Free-standing chimneys - Part 1: General requirements
• Effective Date: 18-Jan-2023

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Free-standing chimneys - Part 1: General requirementsCheminées autoportantes - Partie 1 : Exigences généralesFreistehende Schornsteine - Teil 1: Allgemeine AnforderungenTa slovenski standard je istoveten z:EN 13084-1:2007SIST EN 13084-1:2007en91.060.40Dimniki, jaški, kanaliChimneys, shafts, ductsICS:SIST EN 13084-1:2001/AC:2006SIST EN 13084-1:20011DGRPHãþDSLOVENSKI
STANDARDSIST EN 13084-1:200701-maj-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13084-1February 2007ICS 91.060.40Supersedes EN 13084-1:2000
English VersionFree-standing chimneys - Part 1: General requirementsCheminées autoportantes - Partie 1 : Exigences généralesFreistehende Schornsteine - Teil 1: AllgemeineAnforderungenThis European Standard was approved by CEN on 23 December 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial 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 STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13084-1:2007: E

Gas flow calculation.23 A.1 Principal features of the method of calculation.23 A.2 Parameters related to construction type.23 A.2.1 Roughness.23 A.2.2 Thermal resistance.23 A.3 Basic values for the calculation.24

Site activities.37 B.1 Execution.37 B.2 Programming and coordination of works.37 B.3 Site safety.37 B.4 Local conditions.38 Bibliography.39

 EN 13084-2, Free-standing chimneys - Part 2: Concrete chimneys  EN 13084-4, Free-standing chimneys - Part 4: Brick liners – Design and execution  EN 13084-5, Free-standing chimneys - Part 5: Material for brick liners - Product specifications  EN 13084-6, Free-standing chimneys - Part 6: Steel liners - Design and execution  EN 13084-7, Free-standing chimneys – Part 7: Product specifications of cylindrical steel fabrications for use in single wall steel chimneys and steel liners  EN 13084-8, Free-standing chimneys – Part 8: Design and execution of mast construction with satellite components Additionally applies:  EN 1993-3-2, Eurocode 3 - Design of steel structures – Part 3-2: Towers, masts and chimneys – Chimneys 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 United Kingdom.

1 Scope This European Standard deals with the general requirements and the basic performance criteria for the design and construction of all types of free-standing chimneys including their liners. A chimney may also be considered as free-standing, if it is guyed or laterally supported or if it stands on another structure.
Chimneys attached to buildings have to be structurally designed as free-standing chimneys in accordance with this European Standard when at least one of the following criteria is met:
 the distance between the lateral supports is more than 4 m;  the free-standing height above the uppermost structural attachment is more than 3 m;
 the free-standing height above the uppermost structural attachment for chimneys with rectangular cross section is more than five times the smallest external dimension;  the horizontal distance between the building and the outer surface of the chimney is more than 1 m.
Chimneys attached to free-standing masts are considered as free-standing chimneys.
The structural design of free-standing chimneys takes into account operational conditions and other actions to verify mechanical resistance and stability and safety in use. Detailed requirements relating to specialized designs are given in the standards for concrete chimneys, steel chimneys and liners.
NOTE In other parts of the series EN 13084 rules will be given where chimney products in accordance with EN 1443
(and the relating product standards) may be used in free-standing chimneys.
2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 287-1, Qualification test of welders - Fusion welding - Part 1: Steels EN 1418, Welding personnel - Approval testing of welding operators for fusion welding and resistance weld setters for fully mechanized and automatic welding of metallic materials EN 1443, Chimneys - General requirements EN 13084-2, Free-standing chimneys – Part 2: Concrete chimneys EN 13084-4, Free-standing chimneys – Part 4: Brick liners – Design and execution EN 13084-5, Free-standing chimneys – Part 5: Materials for brick liners - Product specifications EN 13084-6, Free-standing chimneys – Part 6: Steel liners - Design and execution EN 13084-7, Free-standing chimneys – Part 7: Product specifications of cylindrical steel fabrications for use in single wall steel chimneys and steel liners

Eurocode – Basis of structural design EN 1991-1-1, Eurocode 1: Actions on structures - Part 1-1: General actions - Densities, self-weight, imposed loads for buildings EN 1991-1-4:2005, Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions EN 1993-3-2, Eurocode 3 - Design of steel structures - Part 3-2: Towers, masts and chimneys - Chimneys EN 1998-6, Eurocode 8: Design of structures for earthquake resistance - Part 6: Towers, masts and chimneys
EN ISO 3834-2, Quality requirements for fusion welding of metallic materials - Part 2: Comprehensive quality requirements (ISO 3834-2:2005) EN ISO 14731, Welding co-ordination - Tasks and responsibilities (ISO 14731:2006) EN ISO 15607, Specification and qualification of welding procedures for metallic materials - General rules (ISO 15607:2003) EN ISO 15609-1, Specification and qualification of welding procedures for metallic materials - Welding procedure specification - Part 1: Arc welding (ISO 15609-1:2004) EN ISO 15610, Specification and qualification of welding procedures for metallic materials - Qualification based on tested welding consumables (ISO 15610:2003) EN ISO 15611, Specification and qualification of welding procedures for metallic materials - Qualification based on previous welding experience (ISO 15611:2003) EN ISO 15612, Specification and qualification of welding procedures for metallic materials - Qualification by adoption of a standard welding procedure (ISO 15612:2004) EN ISO 15613, Specification and qualification of welding procedures for metallic materials - Qualification based on pre-production welding test (ISO 15613:2004) EN ISO 15614-1, Specification and qualification of welding procedures for metallic materials - Welding procedure test - Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys (ISO 15614-1:2004) EN ISO 15614-2, Specification and qualification of welding procedures for metallic materials - Welding procedure test - Part 2: Arc welding of aluminium and its alloys (ISO 15614-2:2005) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 windshield structural shell designed for load bearing purposes and to protect the flue from wind actions
NOTE It may also function as a flue.

3.2 lining system total system, if any, which separates the flue gases from the windshield. This comprises a liner and its supports, the space between liner and windshield and insulation, where existing 3.3 liner structural membrane of the lining system 3.4 accessible space space between windshield and liner that is designed for entry by personnel 3.5 spoiler device attached to the surface of a chimney with the objective of reducing cross wind response 3.6 protective cap cap at the top of the chimney which covers the space between windshield and liner 3.7 climbing sockets threaded sockets inserted in the concrete windshield to enable climbing dogs to be attached to the surface 3.8 down draught negative pressure on the lee-side of the chimney top, which can cause the flue gases to be drawn down 3.9 guyed chimney chimney, the stability of which is ensured by guy ropes 3.10 intransient heat flow flow of heat, where the temperature of each point does not change with time 3.11 transient heat flow flow of heat, where the temperature changes with time 3.12 positive pressure pressure inside the liner which is greater than the pressure outside the liner 3.13 negative pressure pressure inside the liner which is lower than the pressure outside the liner 3.14 flue gas gaseous products of combustion or other processes, including air, which may comprise of solids or liquids 3.15 concrete chimney chimney, the windshield of which is made of concrete

i) altitude of the site and any special local topographic features (e.g. nearby hills, cliffs); j) maximum, average and minimum outside temperature; k) maximum, average and minimum atmospheric pressure;

Values for thermal conductivity and the heat transfer coefficient may be taken from Table 1 and Table 2 respectively. Values for materials not included in these tables or values differing from these, may be taken if their source is referenced.

Table 1 — Thermal conductivities for building materials Material Description Bulk density kg/m3 TemperatureT °C Thermal conductivity
W/(m⋅K) Concrete
2,1 Lightweight concrete
1000 1200 1400 1600 1800 2000
0,47 0,59 0,72 0,87 0,99 1,20 Brickwork
1800 2000 2200
0,81 0,96 1,00 Acid resistant brickwork
1,2 Brickwork of diatomaceous clay
800 800 800 500 a
500 a
500 a
200 400 600 200 400 600 0,18 0,19 0,21 0,09 0,10 0,11 Cellular glass
130 20 200 300 0,05 0,09 0,12
90 50 100 150 200 250 300 400 500 600 0,038 0,045 0,053 0,064 0,076 0,090 0,122 0,168 0,230 Mineral wool resistant up to 750 °C
50 100 150 200 250 300 400 500 600 0,039 0,046 0,053 0,061 0,070 0,080 0,105 0,140 0,180 Structural steel and weather resistant structural steel
60 Stainless steel X5CrNi18-10 X6CrNiTi18-10 X6CrNiMoTi17-12-2 X2CrNiMo17-12-2 X2CrNiMo18-14-3 X1NiCrMoCu25-20-5 7900 7900 7980 7950 7980 8000
15 15 15 14 15 14 NOTE Where no values for bulk density and temperature are given, the thermal conductivity
may be assumed as independent of these values. a Shall only be used as insulation.

Table 2 — Heat transfer coefficientsa Zone Heat transfer coefficient . W/(m2⋅K) Inner surface of the liner 8+w b In case of accessible space between windshield and liner:  outer surface of the liner  inner surface of the windshield
8 8 In case of non-accessible space between windshield and liner:  outer surface of the liner:  temperature > 80 °C;  temperature ≤ 80 °C  inner surface of the windshield
20 12 8 Outer surface of the windshield 24 c a These values are approximate values which lead to sufficiently accurate results for flue gas carrying tubes with an interior diameter of more than 1 m. b w is the mean flue gas velocity in m/s. A detailed calculation of . is given in Annex A. c For verification of the suitability of the materials as regards temperature a value . = 6 W/(m2⋅K) shall be taken.
4.2.4 Flow calculations Flow calculations shall include calculations of pressure conditions inside the flue gas carrying tube and of flow velocity. They have to take into account the density of the flue gases and of the ambient air as well as energy losses, such as directional losses, losses due to friction and due to the joints.
If flue gas can permeate through the liner, for example in a brickwork liner, no positive pressure is allowed during normal operation conditions.
NOTE The start up pressure is not a normal operating condition in accordance with this European Standard. The calculation should be carried out in accordance with Annex A. In the case of chimneys with a height of less than 20 m, the calculation may be carried out in accordance with EN 13384-1, provided that the conditions given in that standard apply. 4.2.5 Chemical attack Chemical attack of the structural elements in contact with flue gases can occur by condensation of different flue gases to acid, for example sulphuric or hydrochloric acid polluted by chlorides or fluorides. Depending on the nature and period of time of the attack the chemical effect is graded into:
1) low; 2) medium; 3) high; 4) very high.
The chemical attack of flue gases containing SO3 is graded according to Table 3 depending on the period during which the temperature of the liner wall falls below the acid dew point. Periods during which the installation is out of service are to be disregarded when determining the operating hours.

For other flue gases, the level of chemical attack shall be determined by other methods. The temperature of the acid dew point of flue gases containing water vapour (H2O) and sulphur trioxide (SO3) can be taken from Figure 1.
Figure 1 — Temperature of the acid dew point, TADP, of flue gases containing water vapour (H2O) and sulphur trioxide (SO3) Table 3 — Chemical attack due to flue gases containing 50 mg/m3 of SO3 Operating hours per year a Liner face in contact with flue gas Parts of the chimney protected by the liner Degree of chemical attack TADP > 150 °C TADP ≤ 150 °C TADP > 150 °C TADP ≤ 150 °C Low < 10 < 30 < 50 < 150 Medium 10 to 50 30 to 150 50 to 250 150 to 750 High 50 to 1 000 150 to 3 000 250 to 5 000 750 to 15 000b Very high > 1 000 > 3 000 > 5 000 > 15 000b a
During which the temperature of the attacked component is below the acid dew point of the flue gases which are in contact with that component.
b
Only for interpolation purposes (see 3rd paragraph of 4.2.5), however, in no case more than 8760 h
(1 year).
In the absence of such advice,  the degree of chemical attack may be considered as "low", if the temperature of chimney components in contact with flue gas is below acid dew point for periods of less than 25 h per year and the concentrations of HCl ≤ 30 mg/m3 and HF ≤ 5 mg/m3;  the degree of chemical attack shall be considered as "very high", regardless of temperature and exposure time, if halogen concentrations at 20 °C and 1 bar pressure exceed the following limits:  hydrogen fluoride: 300 mg/m3;  elementary chlorine: 1300 mg/m3;  hydrogen chloride: 1300 mg/m3.
Condensing flue gas conditions occurring longer than 10 h per year downstream of a flue gas desulphurization system shall be classified as causing "very high" chemical attack.
While a chimney may generally be at a temperature above acid dew point, care shall be taken to prevent small areas being subjected to local cooling and therefore being at risk of localised acid corrosion. Local cooling may be due to  air leaks;  fin cooling of flanges, spoilers or other attachments;  support points;  down draught effects at the top of the chimney.
Chemical attack can also occur if, for example, dry flue gases become moist at the chimney top as a result of atmospheric influences and affect the inside or outside of the chimney or if the flue gases passing up towards the top or during start-up of the installation cool down to such an extent that condensation occurs.
4.3 Environmental aspects 4.3.1 Noise The noise produced from the chimney shall not exceed permissible noise levels. Under normal conditions this requirement is met if the velocity of the flue gases at the chimney top is less than 25 m/s. In exceptional cases, for example if the flue gas fan is situated in the chimney, or if the velocity is more than 25 m/s, it has to be proven that the permissible noise level is met.
4.3.2 Temperature The temperature of the outer surfaces of chimney areas that can be contacted by people, due to the temperature of the flue gases and based on ambient temperature values taken from official data, shall meet one of the following conditions: a)
temperature shall not exceed 50 °C, b)
temperature increase shall not exceed 10 K. If this requirement is not met a protective device shall be installed to prevent unintentional contact with the chimney wall. The maximum temperature of adjacent combustible materials shall not exceed 85 °C when related to an ambient temperature of 20 °C. The distance between the outer surface of the chimney and the combustible material shall be chosen accordingly.

4.3.3 Protection against falling ice If the possibility cannot be excluded, that ice can form at the chimney or at parts of the chimney, provision shall be made that no damage can be caused by falling ice. This can be achieved for example by protective devices or by heating equipment.
4.3.4 Gas tightness Chimneys with positive pressure in normal operating conditions shall be gastight and shall be conform to the specifications on gas tightness given in EN 1443.
4.4 Insulation A valid insulation system has the following purpose:
a) it reduces the thermal gradient and, therefore, the thermal stress in the liner material.
b) it reduces the heat loss of the flue gases as they flow upwards, within the flue gas carrying tube. This has the following advantages:
 it reduces the temperature drop of the flue gases as they progress up the chimney. This is important in the case of flue gases whose entry temperatures are close to acid dew point, where cooling could result in acid deposition or smutting.  it increases the available thermal lift.
c) it reduces the thermal gradient and thermal stress in the windshield.
In selecting the insulation system, the following characteristics shall be taken into account:
i)
its structural stability, long term. It is important that the insulation material does not sag, exposing uninsulated surfaces; ii)
its thermal conductivity;
iii)
its performance and integrity at the temperatures it will be subjected to in service;
iv)
the acid resistance and moisture absorption of the insulating material and its supports. This is important in brickwork liners, as limited quantities of flue gas can permeate through the liner, condensing as they pass to the cool side of the insulation;
v)
its accessibility.
The thermal insulating material shall be incombustible.

 to reduce the partial vapour pressure of the sulphur oxides of any flue gas that may have leaked through the liner, thereby reducing its acid dew point and minimizing deposition of acid on vulnerable surfaces;
 to allow access for maintenance and inspection into an air space large enough for this purpose.
The ventilation shall be operative at all times. Where an accessible space is provided, its efficacy shall be verified by thermal and flow calculations.
A clear path shall be provided for vertical passage of the air through the total or sectional height of the air space. This requires provision of adequately sized openings through corbels or slabs supporting sectional liners or in the windshield respectively.
4.6 Protective coatings Generally, chimneys have to be protected against corrosion or chemical attack by means of protective coatings. A distinction shall be made between attack by the flue gases and attack by environmental conditions.
Attack by the flue gases happens at
 the interior surface of the flue gas carrying tube;  the exterior surface of the chimney and the access facilities such as ladders, platforms and their fixings exposed to the flue gas trail;  all exterior surfaces exposed to the flue gases of adjoining chimneys.
Bearing the intended use in mind, protective coatings shall be chemically and thermally resistant, impermeable to liquids and adequately resistant to diffusion and to ageing.
4.7 Foundation The foundation shall be protected against thermal and chemical effects. If condensation is to be expected, the upper surface of the foundation shall be sloped and provided with a coating which is acid-resistant and impervious to liquids.
It may be useful to provide a space between the liner and the foundation and to design it in such a way that this space can be entered and ventilated.
4.8 Accessories 4.8.1 Access Chimneys of more than 5 m height above a structurally accessible level (for example a roof of an adjacent building) shall be provided with an access system from this level to the top with the purpose of allowing inspection and maintenance of the following particular items:
 aircraft warning lights, if any (see 4.8.3);

The access system, however, shall allow the inspection of other critical items such as:  outside of the windshield: an integrated facility to support a "sky-climber" may be useful - mainly in the upper part of the chimney - where there will be a local heavier chemical attack and where a day-time painting can be required (see 4.8.3);  flue openings;  drainage system, if any;  dynamic vibration absorber;  erection joint.
The access system shall be installed on the outer windshield surface in case of chimneys with non accessible space and - preferably - on the inner windshield surface in case of chimneys with accessible space. It may consist of permanent ladders or climbing sockets to which ladders may be attached.
In the case of tall and important chimneys the access system may be integrated with a lift (usually rack and pinion type).
Permanent access systems inside the flue gas carrying tube are not permissible in case of chemical attack.
4.8.2 Lightning protection Chimneys generally shall be provided with a lightning protection system, and all metallic parts of the structure (ladders, platforms, iron caps etc.) shall be connected to the down conductors. Steel chimneys, however, can be considered as continuous metal structures and thus can be used as their own lightning protection system. In case of steel chimneys without continuous conductivity additional appropriate measures have to be provided.
Lightning earth protection should consist of metal rods or strips or a combination of both.
The point at which the earth tape connects to the chimney should be accessible.
If the chimney passes into a building it may be earthed at this point by bonding it to the building's lightning protection circuit.
Chimneys supported by guy ropes shall have the upper ends of the guy ropes bonded to the chimney and the lower ends earthed.
A stayed chimney shall be bonded to its stays. If there will be horizontal or vertical movement between the stay and the chimney, an expansion loop shall be provided.
In areas where high temperatures are likely to occur in the subsoil, for example in the neighbourhood of brick kilns, the earth rods or earth strips may have to be installed at a distance from the chimney where the ground is not likely to be dried out.
A chimney standing upon bare rock requires special consideration for its lightning protective system and expert advice should be sought. 4.8.3 Aircraft warning system If required by local civil or military aviation authorities, chimneys shall be provided with aircraft warning lights

In the case of chimneys with non accessible space, warning lights should be connected to the railing of circumferential platforms; if platforms are not fitted the lights should be attached to the windshield. For chimneys with accessible space the warning lights should be located on the outside of the windshield through openings accessible from the internal platforms.
4.8.4 Additional accessories It may be necessary to provide other items such as:
 telephone system;  chemical washing system;  cranes and hoists to lift maintenance parts and equipment;  drainage system for rain as well as for draining possible condensate from liner(s) from the relevant levels to the waste systems at the base;  access and inspection openings;  dynamic vibration absorber.
5 Performance requirements: Structural design 5.1 Basic design principles The following basic design principles are in accordance with EN 1990. They shall also be applied analogously to materials not covered by the respective European Standards.
Chimneys are to be designed for stability and serviceability at their final state as well during construction phases. This includes verification of resistance and of overall stability against overturning.
Unless otherwise stated in the following clauses, reference shall be made to the relevant basic standards for structural analysis, particularly to the respective Eurocodes.
Limit state theory shall be applied.
The limit states are classified into
 ultimate limit states;  serviceability limit states.
At ultimate limit state the design value of the effect of actions such as internal force, moment, stress or strain, Ed, shall not exceed the corresponding design value of the resistance, Rd.
Ed ≤ Rd
At serviceability limit state it shall be verified, that
Ed ≤ Cd
where:
Cd is a nominal value of certain structural design properties related to the design effects of actions considered. The design values for actions are derived from the characteristic values of the actions specified in 5.2, multiplied by the partial safety factor F.
The design values of the resistances, Rd, may be derived from the characteristic values of the relevant structural properties, as material properties or geometrical data, taking into account a partial safety factor M.
Second order effects shall be taken into account if the increase of the relevant moments or internal forces due to deformations calculated from first order theory exceeds 10 %.
5.2 Actions 5.2.1 General The following actions shall be taken into account in the design of chimneys:
 permanent actions;
 variable actions: i) imposed loads; ii) wind actions; iii) internal pressure; iv) thermal effects;
 accidental actions: v) seismic actions; vi) explosions and implosions; vii) impact.
5.2.2 Permanent actions The permanent actions shall include the estimated weight of all permanent structures and elements, such as fittings, insulation, dust loads, clinging ash, present and future coatings and other loads. Selfweight shall be determined according to EN 1991-1-1.
A maximum and a minimum permanent action shall be determined for the calculation of stresses taking into consideration different construction phases.
5.2.3 Variable actions 5.2.3.1 Imposed loads The characteristic value of imposed loads for the design of platforms shall be taken as 2 kN/m2, unless prevailing conditions are likely to give rise to greater loads.

Other wind actions, for example due to uneven wind pressure distribution (ovalling) or interference effects have to be taken into consideration if they are relevant.
The wind actions mentioned above are essentially dynamic. The wind actions on slender and flexible structures such as chimneys can only be determined by dynamic calculation or by application of static equivalent loads. Methods for the determination of these dynamic wind actions are given in EN 1991-1-4.
5.2.3.2.2 Wind loads in the direction of wind Wind loads in the wind direction shall be determined in accordance with EN 1991-1-4 based on the basic wind velocity, vb, of the respective site for a statistical return period of 50 years and on the factors cDIR and cSEASON both to be assumed equal to 1,0.
Orographic influences on the wind velocity, for example for chimneys at exposed locations, such as hills or near escarpments in otherwise relatively flat terrain, shall be taken into account.
The influence of the terrain roughness on the wind velocity shall be taken into account.
NOTE It is recommended to use only categories 0, I and II of EN 1991-1-4:2005, Table 4.1.
Force coefficients cF for chimneys with cross-sections o
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