CEN/TC 265 - Site built metallic tanks for the storage of liquids

This document is a specification for vertical, cylindrical tank systems, built on site, above ground and of which either the primary liquid container or the liquid tight barrier is made of steel. The secondary liquid container, if applicable, can be of steel or of concrete or a combination of both. A primary liquid container made of pre-stressed concrete is excluded from the scope of this document.
This document provides general requirements and specifies principles and application rules for the structural design of the tank system during construction, testing, commissioning, operation (accidental included), and decommissioning. This document applies to all tank system components attached to and located within the liquid, vapour, purge gas, membrane or membrane tank outer containers of the tank system. It does not address the requirements for ancillary equipment such as pumps, pumpwells, valves, instrumentation, external staircases and walkways, roof mounted platforms, external pipe supports, etc. The requirements for those components are covered by the relevant European Standards, structurally designed in accordance with Eurocodes where appropriate, and meeting applicable safety regulations.
This document also does not address tank system operating procedures unless specified for determination of the relevant resistance and protection criteria for the tank systems. It specifies minimum performance requirements for the tank system, tank system foundation and protection systems. From a process piping standpoint, the scope of this document is limited to the following boundaries:
a)   the face of the first flange outside of the tank in bolted flanged connection;
b)   the first threaded joint outside of the tank in threaded connection;
c)   the first circumferential pipe welded joint outside of the tank in welding-end pipe connection, which does not have a flange.
This document is applicable to storage tank systems designed to store products, having an atmospheric boiling point below ambient temperature, in a dual phase, i.e. liquid and vapour. The equilibrium between liquid and vapour phases being maintained by cooling down the product to a temperature equal to, or just below, its atmospheric boiling point in combination with a slight overpressure in the storage tank system.
The maximum design pressure of the tank systems covered by this document is limited to 500 mbar. For higher pressures, reference can be made to EN 13445, Parts 1 to 5.
The operating range of the gases to be stored is between 0 °C and −196°C.
The tank systems covered by this document are used to store large volumes of hydrocarbon products, ammonia and other non-hydrocarbon gases with low temperature boiling points, generally called “Refrigerated Liquefied Gases” (RLGs). Typical products stored in the tank systems are: methane, ethane, propane, butane, ethylene, propylene, butadiene (this range includes the Liquefied Natural Gas (LNG’s) and Liquefied Petroleum Gas (LPG’s)), ammonia, nitrogen, oxygen and argon.
NOTE 1   Properties of the gases are given in Annex A.
The requirements of this document cannot cover all details of design and construction because of the variety of sizes and configurations that may be employed. Where complete requirements for a specific design are not provided, the intention is for the designer, subject to approval of the purchaser's authorized representative and of the regulatory body, to provide design and details that are as safe as those laid out in this document.
EN 14620 consists of multiple parts.  This document specifies general requirements for the tank system concept, selection and general design considerations.
In case of a conflict between general requirements of this document and the requirements in other parts of EN 14620 related to a specific liquefied gas, the product-specific requirements set forth in the other parts prevail.

This document specifies the product characteristics and test/assessment methods for workshop fabricated cylindrical, horizontal steel tanks, single (type S) and double skin (type D) intended to be used for the underground storage of water polluting liquids (both flammable and non-flammable), specifically used for storage and/or supply of fuel for building heating/cooling systems, and of hot or cold water not intended for human consumption at normal ambient temperature conditions (−20 °C to +50 °C) within the following limits:
-   from 800 mm up to 3000 mm nominal diameter and;
-   up to a maximum overall length of 6 times the nominal diameter;
-   for liquids with a maximum density of up to 1,1 kg/l and;
-   with an operating pressure (Po) of maximum 50 kPa (0,5 bar(g)) and minimum – 5 kPa (–50 mbar(g)) and;
-   for double skin tanks with a vacuum leak detection system where the kinematic viscosity does not exceed 5 × 10−3 m2/s.
Two tank types are distinguished:
-   Type S: Single skin;
-   Type D: Double skin.
Tanks designed to this document allow for an earth cover of up to 1,5 m. If there are imposed traffic loads or a greater earth cover, calculation is required.
This document is not applicable to tanks installed in industrial processes or in petrol stations, nor to loads and special measures necessary in areas subject to risk of earthquakes and/or to flooding.

This document specifies the product characteristics and test methods for workshop fabricated cylindrical, horizontal steel tanks, single (type S) and double skin (type D) intended to be used for the underground storage of water polluting liquids (both flammable and non-flammable) and installed in industrial processes or in petrol stations at normal ambient temperature conditions (−20 °C to +50 °C) within the following limits:
-   from 800 mm up to 3 000 mm nominal diameter and;
-   up to a maximum overall length of 6 times the nominal diameter;
-   with an operating pressure (Po) of maximum 50 kPa (0,5 bar(g)) and minimum – 5 kPa (–50 mbar(g)) and;
-   for double skin tanks with a vacuum leak detection system where the kinematic viscosity does not exceed 5 × 10−3 m2/s.
Tanks designed to this standard allow for an earth cover of up to 1,5 m. If there are imposed traffic loads or a greater earth cover, calculation is expected to be carried out.
This document is not applicable to tanks used for storage and/or supply of fuel/gas for building heating/cooling systems, and of hot or cold water not intended for human consumption, nor to loads and special measures necessary in areas subject to risk of earthquakes.
Guidance on installation of tanks is presented in Annex A, which does not include special measures that might be necessary in areas subject to flooding.
This document is not applicable for the storage of liquids having dangerous goods classes listed in Table 1 because of the special dangers involved.
(...)
NOTE   The classifications referred to are those adopted by the United Nations Committee of Experts on the Transport of Dangerous Goods (not to be interpreted as tank classes described in 6.2).

This document specifies the requirements for metallic shop fabricated cylindrical, horizontal steel tanks, single and double skin for the aboveground storage of water polluting liquids (both flammable and non-flammable) within the following limits:
-   from 800 mm up to 3 000 mm nominal diameter and,
-   up to a maximum overall length of 6 times the nominal diameter and,
-   for liquids with a maximum density of up to 1,9 kg/l and,
-   with an operating pressure (Po) of maximum 1,5 bar (abs.) and,
-   where double skin tanks with a vacuum leak detection system are used the cinematic viscosity of the stored media shall not exceed 5 ´ 10-3 m2/s.
This document is applicable for normal ambient temperature conditions (- 20 °C to + 50 °C). Where temperatures are outside this range, additional requirements need to be taken into account.
This document is not applicable for the storage of liquids having dangerous good classes listed in Table 1 because of the special dangers involved.
Table 1 - List of dangerous goods the storage of which are not covered by this document
UN-classification   Storage media
Class 1                     Explosives
Class 4.2                  Substances liable to spontaneous combustion
Class 4.3                  Substances which in contact with water emit flammable gases
Class 5.2                  Organic peroxides
Class 6.2                  Infectious substances
Class 7                   Radioactive material, hydrocyanic or hydrocyanic solvent liquids, metalcarbonyls, hydrofluoracid, bromide liquids
NOTE   The classifications referred to are those adopted by the United Nations Committee of Experts on the Transport of Dangerous Goods (not to be interpreted as tank classes described in 3.1.4).
This document does not cover the installation of tanks which might be subject to local regulations involving pollution control.

This European Standard specifies the requirements for testing, drying, purging and cool-down of the refrigerated liquefied gas storage tanks.
This European Standards deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.

This European Standard specifies the requirements for materials, design and installation of the insulation of refrigerated liquefied gas (RLG) storage tanks.
RLG storage tanks store liquefied gas with a low boiling point, i.e. below normal ambient temperature.
The concept of storing such products in liquid form and in non-pressurized tanks therefore depends on the combination of latent heat of vaporization and thermal insulation.
Consequently thermal insulation for RLG storage tanks is not an ancillary part of the containment system (as for most ambient atmospheric hydrocarbon tanks) but it is an essential component and the storage tank cannot operate without a properly designed, installed and maintained insulation system.
The main functions of the insulation in RLG storage tanks are:
¾   to maintain the boil off below the specific limits;
¾   to protect the non low temperature parts/materials of the tank (mainly the outer tank) by maintaining these parts at their required ambient temperature;
¾   to limit the cool-down of the foundations/soil underneath the tank to prevent damage by frost heave;
¾   to prevent/minimize condensation and icing on the outer surfaces of the tank.
A wide range of insulation materials is available. However the material properties differ greatly amongst the various generically different materials and also within the same generic group of materials.
Therefore within the scope of this European Standard, only general guidance on selection of materials is given.
NOTE   For general guidance on selection of materials see Annex A.
This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.

This European Standard specifies general requirements for materials, design and construction of the concrete components of the refrigerated liquefied gas storage tanks.
This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.

This European Standard specifies general requirements for the materials, design, construction and installation of the metallic components of refrigerated liquefied gas storage tanks.
This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.

This document specifies the requirements for the materials, design, fabrication, erection, testing and inspection of site built, vertical, cylindrical, flat bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperatures and above, and the technical agreements that need to be reached (see Annex A).
This document does not apply to tanks where the product is refrigerated to maintain it as a liquid at atmospheric pressure (see prEN 14620).
This document is concerned with the structural integrity of the basic tank structure and does not provide requirements for considering process design, operational issues, safety and firefighting facilities, in-service inspection, maintenance or repair. These aspects are covered in detail in other Codes of Practice (see Annex B).
1.2   This document applies to closed-top tanks, with and without internal floating covers (see Annex C) and open-top tanks, with and without floating roofs (see Annexes D and E). It does not apply to 'lift-type' gas holders.
1.3   This document applies to storage tanks with the following characteristics:
a)   design pressure less than 500 mbar ) and design internal negative pressure not lower than 20 mbar (see 5.1 for pressure limitations);
b)   design metal temperature not lower than -40 °C and not higher than +300 °C (see 5.2.2);
c)   maximum design liquid level not higher than the top of the cylindrical shell.
1.4   The limits of application of this document terminate at the following locations.
- face of the first flange in a bolted flange connection;
- first threaded joint on the pipe or coupling outside of the tank shell, roof or bottom;
- first circumferential joint in a pipe not having a flange connection.
1.5 This document is applicable to steel tanks with a maximum design strength £ 260 N/mm2.
1.6   In addition to the definitive requirements, this document also requires the items detailed in Annex A to be documented. For compliance with this document,

This document specifies the requirements for testing, drying, purging, cool-down and decommissioning of refrigerated liquefied gas storage tanks.
This document deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed tank systems for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -196°C.

This document specifies the requirements for materials, design and installation of the insulation of refrigerated liquefied gas (RLG) storage tank systems.
RLG storage tank systems store liquefied gas with a low boiling point, i.e. below normal ambient temperature.
The concept of storing such products in liquid form and in non-pressurized tanks therefore depends on the combination of latent heat of vaporization and thermal insulation.
Consequently, thermal insulation for RLG storage tank systems is not an ancillary part of the containment system (as for most ambient atmospheric hydrocarbon tanks) but it is an essential component and the storage tank system cannot operate without a properly designed, installed and maintained insulation system.
The main functions of the insulation in RLG storage tank systems are:
-   to maintain the boil off due to heat in-leak at or below the specified limits;
-   to limit the thermal loading of the outer tank components, so to prevent both their sudden damage and premature ageing (e.g. due to external condensation and ice formation);
-   to prevent damage by frost heave of the foundation/soil beneath the tank base slab (in combination with the slab heating system for tanks resting at grade);
-   to minimize condensation and icing on the outer surfaces of the tank.
A wide range of insulation materials is available. However, the material properties differ greatly amongst the various generically different materials and also within the same generic group of materials.
Therefore, within the scope of this document, only general guidance on selection of materials is given.
NOTE   For general guidance on selection of materials, see Annex A.
This document deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed tank systems for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and −196 °C.
refrigerated, liquefied gases with operating temperatures between 0 °C and −196 °C.

This document specifies the requirements for metallic shop fabricated cylindrical vertical steel tanks, single and double skin for the aboveground storage of water polluting liquids (both flammable and non-flammable) within the following limits:
—   from Ø 1250 mm up to Ø 4 000 mm inner tank nominal diameter, and
—   up to maximum overall shell length of 6 times the nominal inner tank diameter (or max 14 m shell lenght Lz), and
—   tank possible to be divided from 1 to 5 compartments,
—   for liquids with maximum density of up to 1,9 kg/l, and
—   with an operating pressure (P0) of maximum 50kPa (0,5 bar (g)) and minimum – 5 kPa (- 50 mbar (g)), and
—   where double skin tanks with vacuum leak detection system are used the kinematic viscosity of the stored media shall not exceed 5 × 10−3 m2/s.
This document is applicable for normal ambient temperature conditions (−40 °C to + 50 °C). Where temperatures are outside this range, additional requirements need to be taken into account.
This document is not applicable to tanks used for storage and/or supply of fuel/gas for building heating/cooling systems, and of hot or cold water not intended for human consumption, nor to loads and special measures necessary in areas subject to risk of earthquakes.
This document is not applicable for the storage of liquids having dangerous goods classes listed in Table 1 because of the special dangers involved.
Table 1 - List of dangerous goods which are not covered by this document
UN-classification   Type of dangerous goods
Class 1   Explosives
Class 4.2   Substances liable to spontaneous combustion
Class 4.3   Substances which in contact with water emit flammable gases
Class 5.2   Organic peroxides
Class 6.2   Infectious substances
Class 7   Radioactive substances, hydrocyanic or hydrocyanic solvent liquids, metal carbons, hydrofluoric acid, bromide liquids
NOTE   The classifications referred to are those adopted by the United Nations Committee of Experts on the Transport of Dangerous Goods (not to be interpreted as tank classes described in 6.2).

This document specifies the requirements for the materials, design, fabrication, erection, testing and inspection of site built, vertical, cylindrical, flat bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperatures and above, and the technical agreements that need to be reached (see Annex A).
This document does not apply to tanks where the product is refrigerated to maintain it as a liquid at atmospheric pressure (see EN 14620 part 1 to 5).
This document is concerned with the structural integrity of the basic tank structure and does not provide requirements for considering process design, operational issues, safety and firefighting facilities, in-service inspection, maintenance or repair. These aspects are covered in detail in other Codes of Practice (see Annex B).
This document applies to closed-top tanks, with and without internal floating roofs (see Annex C) and open-top tanks, with and without floating roofs (see Annexes D and E). It does not apply to 'lift-type' gas holders.
This document applies to storage tanks with the following characteristics:
a)   design pressure less than 60 mbar  and design internal negative pressure not lower than 6,0 mbar (see 5.1 for pressure limitations);
b)   design metal temperature not lower than -40 °C and not higher than +300 °C (see 5.2.2);
c)   maximum design liquid level not higher than the top of the cylindrical shell.
The limits of application of this document terminate at the following locations:
-   face of the first flange in a bolted flange connection;
-   first threaded joint on the pipe or coupling outside of the tank shell, roof or bottom; and
-   first circumferential joint in a pipe not having a flange connection.
This document is applicable to storage tanks where, irrespective of the material strength used, the  maximum allowable stress does not exceed  260 N/mm2.
In addition to the definitive requirements, this document also states that the items detailed in Annex A have to be documented. For compliance with this document, both the definitive requirements and those required in Clause 4 are meant to be satisfied.

This standard specifies the product characteristics and test/assessment methods for workshop fabricated cylindrical, horizontal steel tanks, single (type S) and double skin (type D) intended to be used for the underground storage of water polluting liquids (both flammable and non-flammable) at normal ambient temperature conditions (-20 °C to +50 °C) within the following limits:
   from 800 mm up to 3000 mm nominal diameter and,
   up to a maximum overall length of 6 times the nominal diameter
   for liquids with a maximum density of up to 1,9 kg/l and,
   with an operating pressure (Po) of maximum 1,5 bar (abs.) and,
   for double skin tanks with a vacuum leak detection system where the kinematic viscosity does not exceed 5  10-3 m2/s.
Tanks designed to this standard allow for an earth cover of 1.5m and for the tank to withstand traffic loads from a properly constructed roadway
This standard is not applicable for the storage of liquids having dangerous good classes listed in Table 1 because of the special dangers involved.

An annex giving the requirements for self-supporting aluminium roofs for fixed roof tanks.

This European Standard is a specification for vertical, cylindrical tanks, built on site, above ground and of which the primary liquid container is made of steel. The secondary container, if applicable, may be of steel or of concrete or a combination of both. An inner tank made only of pre-stressed concrete is excluded from the scope of this European Standard.
This European Standard specifies principles and application rules for the structural design of the “containment” during construction, testing, commissioning, operation (accidental included), and decommissioning. It does not address the requirements for ancillary equipment such as pumps, pumpwells, valves, piping, instrumentation, staircases etc. unless they can affect the structural design of the tank.
This European Standard applies to storage tanks designed to store products, having an atmospheric boiling point below ambient temperature, in a dual phase, i.e. liquid and vapour. The equilibrium between liquid and vapour phases being maintained by cooling down the product to a temperature equal to, or just below, its atmospheric boiling point in combination with a slight overpressure in the storage tank.
The maximum design pressure of the tanks covered by this European Standard is limited to 500 mbar. For higher pressures, reference can be made to EN 13445, Parts 1 to 5.
The operating range of the gasses to be stored is between 0 °C and –165 °C. The tanks for the storage of liquefied oxygen, nitrogen and argon are excluded.
The tanks are used to store large volumes of hydrocarbon products and ammonia with low temperature boiling points, generally called “Refrigerated Liquefied Gases” (RLG’s). Typical products stored in the tanks are: methane, ethane, propane, butane, ethylene, propylene, butadiene (this range includes the LNG’s and LPG’s).
NOTE   Properties of the gases are given in Annex A.
The requirements of this European Standard cannot cover all details of design and construction because of the variet

The Standard specifies the requirements for shop fabricated cylindrical, horizontal tanks, single and double skin for underground storage of water polluting liquids (both flammable and non-flammable). The standard is applicable for normal operating conditions (-20°C to +50°C). Where temperatures can fall below this range, additional requirements shall be taken into account. Quittance on liquid material combinations is given in annex B. The standard is not applicable for liquids causing special danger. The standard does not deal with internal coating.