SIST EN 13636:2004

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.FHYRYRGRYKathodischer Korrosionsschutz von unterirdischen metallenen Tankanlagen und zugehörigen RohrleitungenProtection cathodique des réservoirs métalliques enterrés et tuyauteries associéesCathodic protection of buried metallic tanks and related piping77.060Korozija kovinCorrosion of metals23.020.10UH]HUYRDUMLStationary containers and tanksICS:Ta slovenski standard je istoveten z:EN 13636:2004SIST EN 13636:2004en01-november-2004SIST EN 13636:2004SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13636July 2004ICS 23.020.10; 77.060English versionCathodic protection of buried metallic tanks and related pipingProtection cathodique des réservoirs métalliques enterréset conduites associéesKathodischer Korrosionsschutz von unterirdischenmetallenen Tankanlagen und zugehörigen RohrleitungenThis European Standard was approved by CEN on 3 November 2003.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 Central Secretariat 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 Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13636:2004: ESIST EN 13636:2004

Groundbed data.35 B.1 General considerations.35 B.2 Type of groundbed.35 B.2.1 General.35 B.2.2 Remote located groundbed.35 B.2.3 Close located groundbed.35 B.3 Anode type.36 B.3.1 High-silicon cast iron anodes.36 B.3.2 Mixed-metal oxide anodes.37 Annex C (informative)
Extract of pr EN 50162.38 Annex D (informative)
Determination of inspection interval.39 D.1 General.39 D.2 Complexity of the cathodic protection system.39 SIST EN 13636:2004

NOTE The protection of internal surfaces is covered by EN 12499. This document is applicable to buried tanks and associated piping, even if they are earthed by their own local earthing device, which are electrically separated from any general earthing systems and other buried structures. Therefore tanks which are covered by the present document include:
 industrial storage tanks, irrespective of their dimensions and the nature of the stored medium (liquid or gas, flammable or not, toxic or non-toxic, polluting or not);  tanks used at petrol stations and on domestic or commercial premises, which contain flammable liquids or gases or polluting substances. This document is not applicable to:  above-ground storage tank floors in contact with the ground;  reinforced concrete containers;  buried storage tanks that are electrically connected to the whole or a part of an industrial complex;  buried storage tanks electrically connected to any general earthing systems. NOTE Cathodic protection of the last two types of tanks is covered by prEN 14505.
Measurement techniques are described in detail in EN 13509. 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 12954:2001, Cathodic protection of buried or immersed metallic structures — General principles and application for pipelines. prEN 14505:2002, Cathodic protection of complex structures. EN 50014, Electrical apparatus for potentially explosive atmospheres — General requirements. EN 50016, Electrical apparatus for potentially explosive atmospheres — Pressurized apparatus “p”. SIST EN 13636:2004

3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12954, EN 60079-10, EN ISO 8044 and the following apply. 3.1 electrical connection (electrically connected) connection allowing the flow of electrons between two different metallic structures
Figure 1 — Example of bonding permitting flow of current 3.2 electrical separation (electrically separated) separation of two different metallic structures to prevent the flow of electrons between them
Figure 2 — Example of isolation to prevent the flow of currrent
3.3 associated piping all metallic process piping that is electrically connected to a buried tank and is protected by the cathodic protection system of the tank 3.4 local earthing system local earthing system for the structure under consideration which is electrically separated from any other general earthing e.g. welding metallic bond or cableStructure1Structure2Structure1Structure2Structure1Structure2Structure 1 Structure 2Structure 1 Structure 2Isolating material SIST EN 13636:2004

E ≤ Ep where
E is the metal to electrolyte potential For carbon steel in soils with resistivities of ρ < 100 Ωm and in the absence of sulfate reducing bacteria, the protection potential versus a Cu/CuSO4 saturated reference electrode, Ep,, is -0,85 V. Special measures in accordance with EN 12954:2001, Table 1, shall be taken for steel with high yield strengths to avoid hydrogen-induced cracking. NOTE 1 Full details of the principle and criteria of cathodic protection are given in EN 12954:2001, Clause 4. NOTE 2 On well insulated tanks where the potential criterion is difficult to verify, the effectiveness of cathodic protection can be checked by measurement via a coupon (see 7.4.2). 5 Prerequisites for the application of cathodic protection 5.1 General The different tank systems to be cathodically protected should be separate from each other. NOTE 1 The separation distance depends on the diameter, the length and above all the average coating resistance of the tanks. It also depends on the location (close or remote) of the groundbed in relation to the cathodically protected structure. NOTE 2 The design of cathodic protection for tank systems depends on the location and the extent of the structure, the kind of embedding material, the soil resistivity, the coating (type, coating resistance etc.) and also on general safety requirements. For well-coated tanks the separation distance should be a minimum of 0,40 m between tanks. The cathodically protected structure should be sufficiently remote from any other buried structure so that these foreign structures do not act as a shield for the structure to be cathodically protected and do not suffer from interference effects. For well-coated tanks, the distance between cathodically protected and foreign structures should be a minimum of 1,0 m. Where the tanks being cathodically protected are enclosed within steel reinforced concrete retaining walls, special attention shall be given to avoid: a) detrimental effects of the cathodic protection currents upon the steel reinforcement; SIST EN 13636:2004

b) reduce protection current demand;
c) improve current distribution; and
d) reduce interference to other foreign structures. The coating should: a) be compatible with cathodic protection; and b) be resistant to the stored fluid. NOTE In some cases, with structures comprising different metals, it can only be necessary to cover the more cathodic metal (see 7.1, Note a). On structures which are bare or poorly coated, e.g. an existing tank, cathodic protection shall be applied with care to avoid electrical interference. SIST EN 13636:2004

given by the owner or mandatory representative concerning the proposed structure to be protected. 6.2 Neighbouring structures Details of neighbouring buried structures should be obtained. Such information should include as a minimum: a) location (e.g. maps, detailed site layout); b) principle dimensions and characteristics; c) coating details; d) type and location of any earthing system; e) type and location of isolating devices; f) details of foreign cathodic protection systems and/or other possible sources of stray current. NOTE The use of such information can help to prevent adverse effects on the structure and on neighbouring structures. 6.3 Soil environment Environmental conditions can have a major impact on the application of cathodic protection and should therefore be taken into account during the design phase. The environmental conditions can include: a) soil resistivities at suitable depths and locations; b) presence of stray currents; c) probability of sulphate reducing bacteria activity; d) ground water level. 6.4 Tank and piping data 6.4.1 General For the design of the cathodic protection of tanks and associated piping the following information should be available: a) location of the structure; b) structure materials and dimensions including surface area; SIST EN 13636:2004

a) the isolation of electrical equipment from the cathodically protected structure (as shown for example in A.1); NOTE In this case the equipment is not protected by the cathodic protection system of the tank. b) the use of electrical equipment of protection classes II or III as defined in EN 61140 (as shown for example in A.2); c) the installation of a fault current breaker, if necessary in conjunction with a local earthing system (as shown for example in A.3); d) the use of an isolating transformer (safe isolation, see EN 60742) (as shown for example in A.4); e) the installation of d.c. decoupling devices between the electrical equipment and the general earthing system (as shown for example in A.5). SIST EN 13636:2004

If installed in zone 0, the equipment shall conform to EN 50020 and shall be of type ia. In zone 1, explosion-proof electrical equipment or systems shall conform to one of the following documents: a) EN 50016, for pressurized apparatus type “p”; b) EN 50017, for powder filling type “q”; c) EN 50018, for flameproof enclosure type “d”; d) EN 50019, for increased safety type “e”; e) EN 50020, for intrinsic safety type “i”; f) EN 50028, for encapsulation type “m”; g) EN 50039, for intrinsically safe electrical system type “i”. In zone 2, the equipment shall conform to EN 50021 for non sparking type “n”. 7.3.3 Isolating joints Isolating joints between cathodically protected and non-protected parts of the installation should not be placed in hazardous areas. NOTE Attention is drawn to safety national regulations covering hazardous areas. Isolating joints shall not be installed in zone 0, except if the zone 0 is located inside the pipe, in which case an isolating joint may only be installed if it is fitted with additional explosion hazard device (e.g. flame arrestor). If isolating joints are installed in zone 1 and 2, they shall meet the requirement for use in the respective zone. The design shall be such that accidental bonding is avoided. To avoid sparks or flashover at isolating joints in zones 1 and 2, explosion-proof spark gaps should be installed. NOTE Spark gaps are not required across isolating joints located inside petrol pump housings at service stations. SIST EN 13636:2004

Recommendations concerning measuring points should be: 1) at least one measuring point for each tank, 2) at least two measuring points for each tank with a surface area of more than 20 m2 and less than 100 m2; 3) one additional measuring point for every 100 m2 up to 500 m2; 4) one additional measuring point for every 500 m2 thereafter. For measurement purposes, all isolating joints should be easily accessible from both sides. If the isolating joints are not accessible, they shall be provided with a test station. Measuring points and, if necessary test stations, shall be defined along the piping, at least at the ends and near critical points (e.g. sleeve pipe). NOTE The number of test stations to be installed on the pipework depends on the length and geometrical arrangement of the piping. To facilitate fault location, the installation of the structure and the cathodic protection system should be carried out in such a way that each part of the structure (tank, pipes, local earthing devices, etc.) can be electrically separated. Bonds, which are to be temporarily opened for measurement reason shall be placed above ground. SIST EN 13636:2004

Coupons should be connected via a test station. 7.4.3 Mechanical connections including flanges Mechanical connections, other than isolating joints, which can cause an unacceptable increase in the longitudinal resistance of the structure shall be electrically bonded. 7.4.4 Sleeve pipe Sleeve pipes should be avoided where possible, unless required by national regulations, in which case special precautions should be taken in accordance with EN 12954:2001, 7.5. 7.4.5 Wall entries Where entries are made through concrete structures, metallic contact between reinforcing steel and the protected structure shall be avoided in accordance with EN 12954:2001, 7.6. A flawless coating shall be applied to the structure and special care shall be taken to avoid coating defects. 7.4.6 Drainage station In areas where d.c. stray current can be present, the need for installing drainage station should be taken into account (see also EN 50162). 7.4.7 Local earthing systems Where earthing is required for safety reasons, a local earthing system (see 3.5) should be installed.
The local earthing system should be made of a metal with a more negative free corrosion potential than the metal to be protected. For carbon steel tanks, zinc, galvanized steel or magnesium should be used as a local earthing material, but copper, stainless steel, or reinforcing steel in concrete should not be used.
To enable accurate measurements (current, earthing resistance, and potential measurements) to be made, it should be possible to temporarily disconnect this local earth connection. NOTE Attention is drawn to safety regulations regarding earth connections. 7.5 Galvanic anode systems 7.5.1 General Cathodic protection using galvanic anodes can be obtained economically if: a) the current requirement is low; SIST EN 13636:2004
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