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GS_EP_SAF_341_02_EN.doc

GENERAL SPECIFICATION

SAFETY

GS EP SAF 341

Location and protection of onshore hydrocarbon storage

02 10/05 Addition of EP root to document identification

01 10/03 Change of Group name and logo

00 04/01 Old TotalFina SP SEC 341

Rev. Date Notes


General Specification Date: 10/05

GS EP SAF 341 Rev: 02


GS_EP_SAF_341_02_EN.doc /21

Contents

1. Scope .......................................................................................................................3 1.1 Purpose of the specification...............................................................................................3 1.2 Applicability........................................................................................................................4

2. Reference documents.............................................................................................4

3. Terminology and definitions ..................................................................................6

4. Layout ......................................................................................................................9 4.1 Maximum storage capabilities ...........................................................................................9 4.2 Safety distances ................................................................................................................9

5. Containment ..........................................................................................................14 5.1 Containment control.........................................................................................................14 5.2 Gas detection...................................................................................................................16 5.3 Bunding............................................................................................................................16 5.4 Bund drainage .................................................................................................................17 5.5 Catch pit...........................................................................................................................18

6. Fire prevention and control..................................................................................18 6.1 Protection against static, lightning and stray currents .....................................................18 6.2 Passive fire protection .....................................................................................................18 6.3 Fire-fighting means ..........................................................................................................19 6.4 Fire detection ...................................................................................................................20 6.5 Fire-fighting application rates...........................................................................................20 6.6 Fire-fighting application times ..........................................................................................21






1. Scope

1.1 Purpose of the specification The purpose of this specification is to define the requirements for the location and the protection of onshore hydrocarbon storage atmospheric tanks and pressure vessels. Hydrocarbon storage systems can be sorted out in three categories:

• Tanks for the storage of liquid hydrocarbons

- Fixed roof tanks

- Floating roofs tanks

- Internal floating roof tanks.

• Pressure vessels for storage of liquefied hydrocarbons (LPG storage)

- Above-ground

- Underground or under-embankment.

• Refrigerated vessels at atmospheric pressure for storage of liquefied hydrocarbons (LNG, LPG, ethane, ethylene), not covered by this specification.

Storage tank safety requirements depend on various elements impacted safety and detailed below. It shall be verified at the various project stages that all these inputs have been adequately addressed and that none of their possible consequences on the safety of the tank farm itself, the installation to which it pertains and public beyond the boundaries of the facility have been overlooked.

• Fluid category (or class) of hydrocarbons stored (French classification is used in the development that follows)

• Associated transfer operations

• True vapour pressure at storage temperature

• Type of storage tanks or vessels (above or underground, fixed or floating roofs)

• Capacity of the storage tanks or vessels (individual, in a bund, overall in the installation)

• Impact on inhabited or public places and traffic (roads and railways)

• Vicinity of other storage installations, process facilities, public and fire-fighting facilities.

The present specification is not a design code and must not be used as such; its scope is restricted to safety related issues as follows:

• Layout (refer to chapter 4)

- Maximum capacity of storage

- Safety distances.

• Containment (refer to chapter 5)

- Containment control

- Gas detection

- Bunding.






• Fire control (refer to chapter 6)

- Passive fire protection and active fire-fighting means (in agreement with the fire scenarios mentioned in the SAFETY CONCEPT and GS EP SAF 253)

- Fire-fighting application rates and times.

1.2 Applicability This specification applies to onshore installations only. As a general rule, it shall apply to new installations and to major modifications or extensions of existing installations. Some countries impose retroactive application for LPG storage.

This specification does not cover:

• Storage of liquefied hydrocarbons refrigerated at atmospheric pressure

• Storage of miscellaneous liquid hydrocarbons commonly required for the processing or utilities, such as jet fuel, diesel oil, methanol, glycol, treatment chemicals, etc.

• Storage tank passive fire protection (refer to GS EP SAF 337)

• Under-water storage of hydrocarbons

• Mobile storage facilities

• Transfer operations.

2. Reference documents The reference documents listed below form an integral part of this General Specification. Unless otherwise stipulated, the applicable version of these documents, including relevant appendices and supplements, is the latest revision published at the EFFECTIVE DATE of the CONTRACT.

There is no international regulation covering storage tank safety related matters. Local regulations shall be referred to where existing and as applicable.

In the absence of any local regulation, practice is to follow this general specification GS EP SAF 341. Where local regulations are less stringent than the present specification, this latter shall apply, unless a derogation dossier has been submitted to, and approved, by COMPANY.

Standards

Reference Title

BS 5146 Inspection and test of valves

BS 6755 Testing of valves

Professional Documents

Reference Title

API Publ 2510A Fire Protection Considerations for the Design and Operation of LPG Storage Facilities






API RP 2001 Fire Protection in Refineries

API RP 2003 Protection against ignitions arising out of static, lightning and stray currents

API RP 2021 Fighting Fires in and Around Flammable and Combustible Liquid Atmospheric Storage Tanks

API Std 620 Design and construction of Large, Welded, Low-pressure Storage Tanks

API Std 650 Welded Steel Tanks for Oil Storage

API Std 2000 Venting Atmospheric and Low Pressure Storage Tanks

API Std 2510 Design and Construction of LPG Installations

GESIP 91/01 Commentaires sur le projet de règles d'aménagement et d'exploitation des dépôts d'hydrocarbures liquides

GESIP 93/04 Incendie des grandes cuvettes, prévention et stratégies d'intervention

GESIP 93/10 Recommandations pour systèmes de fermeture de canalisation en pied de bac

Regulations

Reference Title

NFPA 11 Low-Expansion Foam

NFPA 11A Medium- and High-Expansion Foam Systems

NFPA 11C Mobile Foam Apparatus

NFPA 15 Fixed Water Spraying Systems

NFPA 16 Installation of Deluge Foam - Water Sprinkler and Foam - Water Spray Systems

NFPA 20 Fire-water Pumps

NFPA 30 Flammable and Combustible Liquids Code

NFPA 31 Oil Burning Equipment

NFPA 58 Standard for the Storage and Handling of LPG

NFPA 59 Standard for the Storage and Handling of LPG at Utility Gas Plants

Arrêté du 4/9/1967 Règles d’aménagement et d’exploitation des usines de traitement de pétrole brut, de ses dérivés et résidus

Arrêtés du 9/11/1972 et du 19/11/75

Règles d’aménagement des dépôts d’hydrocarbures liquides et liquéfiés

Arrêté du 10/5/1993 (fluid category A2)

Stockage de gaz inflammables liquéfiés sous pression






Instructions Ministérielles PRME 89/61.679 C and 680 C du 9/11/1989 and subsequent clarifications by GESIP

Dépôts anciens de liquides inflammables

Dépôts de gaz combustibles liquéfiés.

Codes

Reference Title

IP Code Part 3 Refining Safety Code

IP Code Part 9 Liquefied Petroleum Gas

IP Code P9 Large Pressure Storage and Refrigerated LPG

Other documents

Reference Title

Safety Concept

Statement Of Requirements (SOR)

Total General Specifications

Reference Title

GS EP SAF 021 Layout of installations

GS EP SAF 228 Safety rules for drainage systems

GS EP SAF 253 Impacted, restricted areas and fire zones

GS EP SAF 312 Guidelines for selecting and installing fire and gas detection systems

GS EP SAF 321 Fire pump stations and fire-water mains

GS EP SAF 334 Foam fire extinguishing systems

GS EP SAF 337 Passive fire protection

3. Terminology and definitions Atmospheric storage

Storage of hydrocarbons such as the True Vapour Pressure @ storage temperature is less than 1.6 bara (French regulation).

Atmospheric tank

Storage tank designed to operate at pressures ranging from atmospheric to 3500 Pa g (0.5 psig), measured at the top of the tank (NFPA).

Bund Area that is surrounded by embankments and/or walls, in order to confine the spillage of hydrocarbons from the storage tanks or vessels. "Bund" has the same meaning as the American wording "dike".






Equivalent storage capacity

The equivalent storage capacity is defined as the sum of all the fixed and mobile capacities, multiplied by the following factors:

• Fluids categories B, C1 and D1: 1

• Fluids category C2: 1/3

• Heavy fuel-oils: 1/15

• Fluids category D2: 0

Fluid category As per French regulation, hydrocarbons fluids are sorted as follows:

• Fluid category A: liquefied hydrocarbons with True Vapour Pressure (TVP) > 1 bara. at 15°C

- A1: Liquefied at t < 0°C

- A2: Liquefied in other conditions.

• Fluid category B: liquid hydrocarbons with flash point < 55°C

• Fluid category C: liquid hydrocarbons with: 55°C ≤ flash point < 100°C

- C1: Storage temperature above flash point

- C2: Storage temperature below flash point.

• Fluid category D: liquid hydrocarbons with: 100°C ≤ flash point:

- D1: Storage temperature above flash point

- D2: Storage temperature below flash point.

As per American regulation (NFPA), hydrocarbons fluids are classified as follows:

• Fluid class IA: liquid having a flash point below 22.8°C:

- IA: Atmospheric boiling point below 37.8°C

- IB: Atmospheric boiling point above 37.8°C.

• Fluid class IC: Liquid having a flash point at or above 22.8°C and below 37.8°C.

• Fluid class II: Liquid having a flash point at or above 37.8°C and below 60°C.

• Fluid class IIIA: Liquid having a flash point at or above 60°C and below 93°C.

• Fluid class IIIB: Liquid having a flash point at or above 93°C.

As per British regulation, hydrocarbons fluids are classified as follows:

• Fluid class 0: Liquefied Petroleum Gases (LPG).

• Fluid class I: liquid hydrocarbon with a flash point below 21°C.

• Fluid class II: liquid hydrocarbon with a flash point above 21°C but below 55°C

- II(1): Stored below flash point






- II(2): With storage temperature above flash point.

• Fluid class III: Liquid hydrocarbon with a flash point above 55°C.

- III(1): Flash point above 55°C but below 100°C and stored below flash point

- III(2): Same as III(1) but stored above flash point.

• Unclassified: liquid hydrocarbon with a flash point above 100°C. Unclassified petroleum liquids should be considered as class III(2) when handled at, or above, their flash point temperature.

Flash point Minimum temperature at which a liquid gives off vapour in sufficient concentration to form an ignitable mixture with air near the surface of the liquid (NFPA).

Impacted area Area that extends beyond the boundaries of the installation but which is nevertheless affected permanently by normal operation of the facility or exceptionally by the consequences of an emergency situation caused by a major failure (COMPANY).

Places - Public places: Places receiving public or with buildings higher than 28 m.

- Inhabited places: All places not meeting the public place criteria. Note that for some countries, the notion of desert place does not exist.

Reid Vapour Pressure (RVP)

Vapour pressure of a liquid determined by laboratory testing in a standard manner in the Reid apparatus at a standard temperature of 37.8°C (100°F) (ASTM and IP Code). Not to be confused with the true vapour pressure.

Restricted area Area within the boundaries of the installation and hence under the control of COMPANY, which is affected permanently by normal operation of the facility or exceptionally by the consequences of an emergency situation caused by a major failure. The restricted area is materialised by a security fence (COMPANY).

Storage tank Vessel having a liquid capacity that exceeds 227 litres is intended to a fixed installation and is not used for processing (NFPA).

Storage, under-embankment

Storage vessel that is above grade, but covered by a layer of sand or soil.

Traffic means - Important traffic means: Road with more then 2000 vehicles per day or passengers transportation by railway.

- Traffic means: External roads with more than 200 vehicles per day or railways devoted to the installation and under control or external railways without passengers transportation.

- Other traffic means: External roads with less than 200 vehicles per day or roads devoted to the installation, and under control.






4. Layout

4.1 Maximum storage capabilities

4.1.1 Tanks for liquid hydrocarbons There is no regulatory limitation in size for liquid hydrocarbon storage. In this document, it is assumed that the equivalent storage capacity exceeds 1000 m3, this covering almost any COMPANY installation. However, less stringent rules (to be defined for each project and in function of local regulation) are acceptable where equivalent storage capacity does not exceed 1000 m3. A derogation dossier shall be established and submitted for COMPANY's approval.

Experience has demonstrated that there is a maximum practicable size for the extinguishing of a pool fire, which is about 7000 m2. Where capacities are larger, it should be assumed that the fire extinguishing might be impossible. For reasons of fire-fighting effectiveness there should not be more than two rows of tanks in the same bund and between two adjacent access roads.

4.1.2 Pressure vessels for liquefied hydrocarbons Storage in which the fluid true vapour pressure at storage temperature is above 1.6 bara shall be considered as pressure storage. Maximum capacity of each storage vessel shall be:

• 500 m3, as a general rule, for above-ground vessels. However, larger vessels up to 1200 m3 can be installed, providing a specific risk assessment study is conducted and approved by COMPANY and it is demonstrated that the risks can be mitigated down to the same level as if the vessel were underground or under-embankment

• 10000 m3 for underground or under-embankment vessels.

For Liquefied Petroleum Gases (LPG) with TVP at 15°C above 20 bara (e.g. propane), the maximum capacity of each above-ground storage vessel is limited at 120 m3 within process units.

4.2 Safety distances Minimum distances shall be governed by three main criteria:

• Definition of the impacted and restricted areas around the installation

• Minimum distances between units in the installation (between storage and other units, between different storage units)

• Minimum distances between different equipment within the same storage unit.

4.2.1 Impacted and restricted area

4.2.1.1 General As far as practicable, COMPANY's practice is to control and/or protect the whole area that can be impacted, i.e. to extend some security coverage to the whole impacted area.

Wherever this cannot be achieved (e.g. densely inhabited areas), mitigating measures, devised jointly with LOCAL AUTHORITIES, shall be enforced: traffic and construction shall be minimised and controlled, uncontrollable activities such as campsites shall be prohibited and a contingency plan shall be defined with the LOCAL AUTHORITIES.

Fence shall be at least 2.5 m high.






4.2.1.2 Tanks for liquid hydrocarbons The risk considered for the determination of impacted and restricted areas around liquid hydrocarbon storage of any type (fixed roof, floating roof or internal floating roof) is the maximum thermal radiation level in case of pool fire. The criteria are set at 3 kW/m2 (≅ 1000 BTU/hr/sqft) and 5 kW/m2 (≅ 1500 BTU/hr/sqft), respectively. Inhabited places and moderate traffic shall be outside the restricted area while public places and important traffic shall be outside the impacted area. Corresponding distances shall be calculated by a software approved by COMPANY or using the following formulas (see also GS EP SAF 253):

Distance (d)

Formula Minimum

Restricted area 2.8 L0.85 (1 - 0.0022 L0.85) 50 m

Impacted area 3.8 L0.85 (1 - 0.003 L0.85) 100 m

d: Minimum distance (m) from edge of the bund or of loading area

L: Bund width as seen from the impacted area (m), it can be a diagonal

Note: It shall be also verified that these distances fulfil maximum explosion overpressure criteria of 50 mbar and 170 mbar for impacted area and restricted areas, respectively, but it is very unlikely that these criteria shall take precedence over the radiation criteria.

The considerations that proceed are summarised on the sketch below:

5 kW/ m2 3 k W/ m2

Boundary restricted area

Bound ary i mpacted area

M in. 50 m

M in. 100 m

Inhabitedplaces

+moderate

traffic

Publicplaces

+important

traffic

4.2.1.3 Pressure vessels for liquefied hydrocarbons For pressure vessels a criterion of maximum exposure to radiation in case of BLEVE is used. Two thresholds are set for impacted area (hence for public places and important traffic) and for restricted area (inhabited places and moderate traffic. Distances fulfilling these overpressure criteria overpressure can be calculated with a software approved by COMPANY or using the following formulas (see also GS EP SAF 253):

Distance (d)

Above ground Under embankment Fence

Restricted area 3.12 M10.425 9 M2

0.333 50 m

Impacted area 4.71 M10.405 22 M2

0.333 50 m






d: Minimum distance (m) from the limit of an above-ground vessel tank or from the top piping outlet of an under-embankment vessel

M1: Mass of liquid stored in the vessel (kg)

M2: Mass of gas between adjacent isolation valves which can release to atmosphere in case of surface piping upset (kg) as illustrated on the sketch below:

M 2

4.2.2 Distances with other units Storage units shall always be located in a specific fire zone distinct from process, wellhead and accommodation/building fire zones. In case an installation comprises a liquid hydrocarbon and a liquefied hydrocarbon storage, both storages shall be located in two different fire zones. Refer to GS EP SAF 253 for more details about fire zones.

Two cases must be considered: (i) incident (fire or explosion) in the storage fire zone and impact onto other fire zones and (ii) incident in a non-storage fire zone and impact onto the storage fire zone. The distances shall be such that the criteria listed below are met.

Maximum consequence on other fire zones Location of

↓ incident Storage Process Wellhead Accom.

Storage 9.5 kW/m2

200 mbar

9.5 kW/m2

300 mbar

9.5 kW/m2

300 mbar

9.5 kW/m2

170 mbar

Process and Wellhead 9.5 kW/m2

200 mbar GS EP SAF 253 GS EP SAF 253 GS EP SAF 253

Minimum distances between units are not linked to the concept of fire zone. These distances are often referred to as "safety distances" although they are not dictated by safety considerations only; but also (and principally) by constraints of construction, operability, maintenance, etc.

Unlike distances between fire zones (see above) which are calculated to match a set of pre-defined criteria, distances between equipment or units within a fire zone are given by tables established by COMPANY and/or imposed by local regulation (refer to GS EP SAF 021). They contribute to the improvement of the global level of safety through mitigation of the consequences of a hazard and better efficiency of the active protection systems, but they are generally not large enough to ensure that a hazard will not propagate to an adjacent equipment or unit. Unless otherwise specified by local regulation and if the restricted area, impacted area and fire zone criteria are met, then the minimum distance mentioned in the table below shall be adhered to.






Distance (d). See note 1

Unit Fluids A

Fluids B, C1, D1

Fluids C2

Fluids D2

Wellheads 150 m

Flares (all types) 60 m

Process units 100 m 60 m 30 m 15 m

Fired heaters 100 m 60 m 30 m 15 m

Oily water basins 60 m 40 m 20 m

Run-down pumps 60 m 20 m

Transfer and metering stations (Note 2) (Note 2) (Note 2) (Note 2)

Other storage (Note 3) (Note 3) (Note 3) (Note 3)

Main Piperack 15 m 15 m 7.5 m

Power gen. and elec. sub-station 75 m 60 m 15 m

Other utilities 60 m 40 m 20 m 10 m

Fire-Fighting 100 m 75 m 30 m 5 m

Control room 100 m 60 m 30 m 10 m

Workshops, Offices 100 m 75 m 30 m 20 m

Accommodation 150 m 100 m 40 m 20 m

Fence See section 4.2.1 10 m Note 1: d: minimum distance (m) between the edges of the units

Note 2: Refer to section 4.2.4

Note 3: Refer to section 4.2.3.

4.2.3 Distances between storage units There is no statutory minimum distance between two different liquid hydrocarbons storage units belonging to the same fire zone, providing their bunds are different and they meet the requirements of the minimum distances between equipment as defined in section 4.2.4. The minimum distances between storage units apply only to the liquefied gas vessels, either with the liquid hydrocarbons tanks, or between themselves, and can be summarised as follows:

4.2.3.1 Between liquid hydrocarbon tank and liquefied hydrocarbon vessel Although liquid hydrocarbon storage and liquefied hydrocarbon storage shall be located in different fire zones and hence distances between tanks (or edge of the bund) shall be calculated to match the radiation and explosion overpressure criteria exposed in section 4.2.2, it shall be checked that the minimum distances (between tanks/vessels walls) below are always fulfilled:






• Where the total capacity of liquefied hydrocarbons does not exceed 4000 m3, the minimum distances depend only upon whether the storage is above ground or under-embankment. For above ground liquefied hydrocarbon storage, the distance to liquid hydrocarbon storage shall be at least 20 m. For under-embankment liquefied hydrocarbon storage, the distance to liquid hydrocarbon storage shall be at least 10 m.

• Where the total capacity of liquefied hydrocarbons exceeds 4000 m3, the minimum distances depend only on the fluid category of liquid hydrocarbons. Minimum distance between a liquefied hydrocarbon storage and a category B liquid hydrocarbon storage shall be at least 40 m. Minimum distance between a liquefied hydrocarbon storage and a category C or D liquid hydrocarbon storage shall be at least 25 m.

4.2.3.2 Between pressure vessels for liquefied hydrocarbons Minimum distance between two liquefied hydrocarbon storage vessels located in different storage units shall be larger than 150 % of the largest vessel diameter plus 5 m. In addition a 2.5 m (or more) wide road or way shall be laid between the two bunds.

D1

D2

> or = 1.5 D1 + 5 m

Road > or = 2.5 m

Two under-embankment or underground storage units are considered as different provided they comply with the distances between equipment as defined in next section 4.2.4.

4.2.4 Between storage equipment

4.2.4.1 Tanks for liquid hydrocarbons

• Skirt to skirt distance between two tanks above-ground within two adjacent bund areas shall be 0.8 D (diameter of the tank) for tanks holding fluids category B, C1 and D1 and 0.2 D for tanks holding fluids category C2 and D2

• Between tank and bund: 1 m

• Skirt to skirt distance between two tanks above ground within a common bund area:

Minimum distances d

Largest tank capacity Fluid category B, C1 and D1

Fluid category C2 and D2 (Notes 1 and 2)

Cap. ≤ 20000 m3 d = D/2 d = D/5

Cap. > 20000 m3 d = D d = D/2

D: Diameter of largest tank in bund

Note 1: Minimum distance shall always be larger than 1.5 m

Note 2: When tanks holding fluids B, C1, C2, D1 and/or D2 are located in the same bund area, the more stringent safety distances shall be used






• Between laboratories for metering and analysing, and above ground storage, transfer pumps or loading posts shall be 15 m

• Between tanks (skirt) and loading areas (edge of truck or freight car):

Fluid category Unloading mobile tanks

Loading mobile tanks

B 5 m 15 m

C 2.5 m 7.5 m

• Horizontal and vertical tanks within the same bund are not permitted.

4.2.4.2 Pressure vessels for liquefied hydrocarbons

• Two above ground spherical vessels: 75 % ∅ biggest sphere

• A spherical vessel and a cylindrical vessel: 75 % largest ∅ biggest sphere

• Two cylindrical vessels

- Capacity ≤ 70 m3: 1 m

- Capacity ≤ 200 m3: 2 m

- Capacity > 200 m3: 100 % largest ∅

• Above ground and under-embankment or underground vessels

- An above-ground vessel and an underground or under-embankment vessel: 2 m

- PSV discharge of an under-embankment vessel and an above ground vessel: capacity ≤ 200 m3: 5 m; capacity > 200 m3: 10 m

• Two underground or under-embankment vessels: 1 m.

5. Containment The containment devices of overhead hydrocarbon storage shall consist in a combination of control devices for the containment in the tank or vessel (normal operations), gas detection and bunding (in case of loss of containment) and bund drainage and catch pit, if any, to dispose the liquids out of the bund.

5.1 Containment control

5.1.1 Tanks for liquid hydrocarbons The containment control of atmospheric tanks for liquid hydrocarbons storage shall consist in the set of the following:

• Design of floating roof: Shall preclude any risk of liquid over-flowing through the annulus between the roof and the skirt of the tank.

• Isolation valves: Each loading/unloading line shall be fitted with a motor operated valve (MOV) or a fail-to-close automatic Shutdown Valve (SDV) when made statutory by local regulation. Both type of valves shall be installed as close as possible to the tank skirt. SDVs that can be exposed to fire, in particular those installed in the bunds, shall be fire






resistant as per codes BS 5146 and BS 6755 or equivalent and capable of withstanding a thermal radiation flux of 5000 BTU/sqft/hr.

• Level control: LI, LAH provides an alarm, LSHH 90 % stops loading and provides an alarm.

• Pressure control - General: Atmospheric tanks shall be protected from over-pressurisation and vacuum

by an adequately-sized vent system, taking into account both thermal breathing and fire case, and as per API Std 2000. A flame arrester shall be included in the vent system to prevent flame migration back to the vessel. A pressure-vacuum relief device (PSV) or a second vent should be installed to protect the tank in case the primary vent control device fouls or otherwise obstructs flow.

- External floating roof tanks: They shall be provided with adequate vents, bleeder valves or other suitable means to evacuate air and/or gas from underneath the roof during initial filling.

- Fixed roof tanks: For tanks that can be emptied in less than 8 hours, a gas blanketing system shall be installed to exclude air and to compensate for the maximum flow that can be pumped out the tank and the shrinkage for ambient temperature changes (wind gusts, rainfalls, etc.). On fixed roof tanks that cannot be emptied in less than 8 hours, tank natural breathing (in-breathing + out-breathing) shall be calculated as per API Std 2000, for the more demanding expectable conditions, and shall be used to determine whether a gas blanketing system is required or not.

- Internal floating roof: A venting system as per API Std 650, Appendix H, shall be provided. The requirement for a gas (or nitrogen) blanketing system shall be driven by consideration of environment protection (and applicable local regulation). If a gas blanketing system is installed, then venting requirements are those of API Std 2000.

- If the atmospheric vessel is heated, a TSHH sensor shall be provided to shut-off the heat input when temperature becomes excessive.

5.1.2 Pressure vessels for liquefied hydrocarbons The containment control of pressure vessels for liquefied hydrocarbons storage shall consist in the set of the following:

• Isolation valves: Each loading/unloading line shall be fitted with a fail-to-close automatic Shutdown Valve (SDV). In addition, and in order to minimise the mass of gas which can release to atmosphere in case of surface piping upset, an internal fail-to close automatic check-valve (FSV) shall be installed. By derogation, where the fluid category or the design of the vessel makes the sitting of internal safety devices impossible, a fail-to-close SDV shall be fitted as close as possible to the vessel. The SDV or the FSV shall close automatically upon very high flow rate (acting like a slam valve) and also upon external instruction either from the Fire and Gas system or operator's voluntary action or both.

• Level control: LI, LSHH 90 % stops loading and provides an alarm, LSHH 95 % detected by one out of two different systems, with line monitoring; same actions as for LSHH plus automatic closure of the loading isolation valves.






• Pressure control - PI

- n+1 PSVs, n PSV being able to relief excess gas to maintain pressure < 110 % design pressure if n = 1 or < 116 % design pressure if n > 1. PSVs shall be sized for the general protection of pressure vessels and for the fire case; these two functions can be achieved either by one single set of PSVs, or two different sets of PSVs each devoted to one function

- Thermal safety valves (TSVs) shall be provided on liquid lines and equipment that can be blocked between two SDVs, if liquefied petroleum product inventory is larger than 2 tonnes

- Vessels that may be damaged by internal vacuum shall be protected accordingly.

5.2 Gas detection

5.2.1 Tanks for liquid hydrocarbons No gas detection device shall be provided, unless otherwise stipulated in local regulations, or required by a particular project specification.

5.2.2 Pressure vessels for liquefied hydrocarbons A gas detection system shall be provided around the storage vessels. Gas detection shall trigger an alarm at 20 % LFL and initiate shutdown actions at 50 % LFL.

5.3 Bunding

5.3.1 Tanks for liquid hydrocarbons Each fixed storage tank, or set of storage tanks (and each set of mobile storage tanks, too) shall be provided with a liquid retention device, which, in most cases, is a bunded area for a set of tanks. The minimum capacity of the bund shall be, for a set of fixed tanks:

• 100 % biggest tank or 20 % total, whichever the largest, for fluid category D2

• 100 % biggest tank or 50 % total, whichever the largest, for fluid category B, C, D1

• 60 % of the maximum capacity of all the mobile tanks for a set of mobile storage tanks handling liquids hydrocarbons of category B.

Independent bunds shall not have a net area (i.e. internal bund area at maximum liquid level, minus tank area) in excess of 7000 m2, otherwise it should be assumed that the fire extinguishing might be impossible. Where a bund contains a set of independent storage tanks, the bund shall be sub-divided by embankments or walls of at least 70 cm height around each tank.

Bunds shall be liquid-tight. The maximum allowable velocity of liquids through the bunds is 10-8 m/s.

5.3.2 Pressure vessels for liquefied hydrocarbons In the case of several tanks in the same bund, the minimum capacity of the bund shall be at least 20 % of the capacity of the biggest vessel in the bund. However, a specific study shall be conducted for each project to check the suitability of this minimum value; if not suitable then the






bund capacity shall be 20 % of the total storage capacity. Each fixed storage vessel with a capacity exceeding 70 m3 or 50 tonnes shall be provided with a liquid retention device. In most cases, it is a bunded area for a set of tanks. If the total storage capacity does not exceed 70 m3 nor 50 tonnes, it is admissible that they have no liquid retention device, provided the area is gravelled and/or is surrounded by a wall of 10 cm.

The bund area shall slope downwards, with a minimum slope of 2 %, to a basin located away (but still in the bund) from the storage vessels in order to minimise the heat flux to the vessels in case of fire in the bund. The bunds shall be designed to minimise evaporation of liquefied hydrocarbons.

The bund capacity for one storage vessel in the bund shall be 20 % of the vessel capacity. In the case of several tanks in the same bund, the minimum capacity of the bund shall be at least 20 % of the capacity of the biggest vessel in the bund. However, a specific study shall be conducted for each project to check the suitability of this minimum value; if not suitable then the bund capacity shall be 20 % of the total storage capacity.

R

C = 20% R

Case No. 1 : One storage vessel

R1

Rn-1

Rn

C =

20%

R1

or C =

20%

(R1 +

R2 +

... +

Rn)

Case No. 2 : Several storage vessel

5.4 Bund drainage Bunds shall be equipped with a suitable drainage system to handle rainwater, fire-water and hydrocarbon spillage from bund areas. Liquefied hydrocarbon bunds shall have their own, independent and segregated drainage system.

Water from the bunds shall be considered as continuously or accidentally contaminated. Each bund drain shall be connected with a manual valve, Normally Closed (NC), to the open drain system from hazardous areas. The draining and subsequent treatment processing procedures shall be covered by specific operating procedures.

A simplified drainage and primary treatment scheme for an onshore installation is provided in GS EP SAF 228 (“Liquid drainage”).






5.5 Catch pit In some particular circumstances, experience has proven beneficial to empty a bund on fire to a dedicated catch pit in order to minimise the duration of fire. This, however, can lead to the draw-effect of promoting the spread of fire to external areas. Therefore, as a general rule, a catch pit is not required.

The decision to implement or not a catch pit shall be taken by COMPANY at the design stage, after discussion with the LOCAL AUTHORITIES. It is part of the SAFETY CONCEPT.

Where a catch pit is to be implemented, a particular project specification shall be released to define at least the following issues:

• The loss of containment and fire scenarios

• The minimum distance between the catch pit and other units, public and traffic

• The capacity of the catch pit

• The fluid transfer procedures and means

• The treatment procedures and means.

6. Fire prevention and control

6.1 Protection against static, lightning and stray currents All conducting objects within a tank such as floating covers, gauge floats, cables, mixers, etc. shall be electrically bonded to the tank shell. Special care shall be taken that metal objects are not accidentally insulated by the application of paint or by the formation of deposits, and electrical continuity between roof and skirt for floating roof tanks, both internal and external.

For tanks which may be connected to trucks for loading/unloading operation, adequate earthing connection shall be provided for the trucks (or cars). The protection provided by so-called high conductivity tyres is not satisfactory.

Protection devices shall be in conformance with API RP 2003, IP Code, Part 3 and relevant DGEP technical specifications.

6.2 Passive fire protection

6.2.1 Tanks for liquid hydrocarbons Passive fire protection devices shall not be provided, unless otherwise stipulated (local regulations, particular project specification, etc.).

6.2.2 Pressure vessels for liquefied hydrocarbons The basic passive fire protection of large pressure vessels containing liquefied hydrocarbons shall consist in a layer of 1 metre of sand or soil above the vessel.

Where covering by an embankment is found impracticable, it can be envisaged to cover the above ground vessels with fire protection materials. The corresponding technical requirements depend upon applicable local regulation and asset protection policy set forth by COMPANY for each specific case and is not covered by the present general specification (refer to GS EP SAF 337 (“Passive fire protection”) for further details). However it is COMPANY's policy to






always protect the legs supporting above ground liquefied hydrocarbon spherical vessels with a suitable coating of refractory cement (vermiculite or magnesium oxychloride type).

Passive fire protection shall not be provided for liquefied hydrocarbons pressure vessels with capacities lower than 120 m3 (LPG) or 500 m3 (other pressure vessels), unless otherwise stipulated by local regulations, or required by a particular project specification.

6.3 Fire-fighting means The fire-fighting means consist in a combination of primary means, secondary means and external support where available. They shall achieve two functions: (i) fire extinguishing by foam application and (ii) cooling of adjacent structures exposed to fire heat. Activation of the fire-fighting means shall be automatic upon fire detection (if any) and/or manual from a remote pushbutton.

6.3.1 Primary fire-fighting means The primary fire-fighting means consist in the following:

• A foam solution common ring shall be provided on the tank top for the protection and cooling of the tank skirt.

• Fixed roof storage tanks shall be fitted with fixed foam system discharging directly into the tank under the surface of hydrocarbon liquids, except for tanks holding fluids category D2 where foam injection systems are not required.

• Floating roof storage tanks shall be fitted with a self contained foam generation skid to discharge foam onto the annular ring space between the tank skirt and the roof. Unless otherwise stipulated by local regulations or required in a particular project specification, the single fire case to be considered is the seal fire, and the full surface fire case resulting from a sinking of the floating roof can be disregarded. The foam skid shall consist of a storage of pre-mix solution (water + foam concentrate), a pressurisation system (air or nitrogen), a discharge ring and a linear heat detection type local fire detection system.

Halon 1211 systems or their equivalent using deca-fluoro-butane (C4F10) or other halogenated Halon substitute shall not be used.

• Bunds shall be fitted with fixed foam discharges located so that any point in the bund is at less than 18 metres away from a discharge outlet.

By derogation of the above, fixed water/foam monitors can be considered as primary means of fire-fighting for fixed roof tanks not exceeding 18 metres in diameter. The adjacent tanks shall be water-cooled as described in section 6.5.

6.3.2 Secondary fire-fighting means In addition to the above, water/foam monitors shall be provided as secondary fire-fighting means. Monitors shall be installed such as it shall be possible to reach any point to be protected (including the tank roof) regardless of weather conditions. In practice, each bund should be equipped with one water/foam monitor on each edge of the bund.

6.3.3 Cooling of exposed tank walls Walls of tanks exposed to radiation from fire of another tank shall be cooled down by (i) their own primary fire-fighting appliances (see section 6.3.1, first exhibit) and (ii) by monitors (see section 6.3.2).






6.3.4 External support Where an external fire-fighting support is available, the means it provides can be taken into account to define the fixed storage capacities of fire-water and foam concentrate. For further details refer to section 6.5, and section 6.6.

However the fire-fighting means defined above as well as the application rates defined below shall be available and operational before the external support shall intervene.

6.4 Fire detection There is no mandatory requirement for an automatic fire detection system, considering that fire detection in that particular case does not constitute a prevention device. Fire detection requirement shall be driven by asset protection consideration only and therefore addressed in the SAFETY CONCEPT and the STATEMENT OF REQUIREMENTS. For specifics about fire detection refer to GS EP SAF 312 (“Guidelines for selecting and installing fire and gas detection systems”).

6.5 Fire-fighting application rates

6.5.1 Tanks for liquid hydrocarbons The fire-water flow rates for cooling effect Q1 (water) and extinguishing effect Q2 (concentrate + water = foam) depend on:

• The type of tanks (fixed roof tanks, floating roof tanks)

• The fluid category of hydrocarbons (B, C1, C2, D1, D2)

• The type of foam (AFFF, FFFP, others, etc.)

• The storage capacity: individual for the tank, total for the installation

• The fire scenario (tank on fire, bund on fire)

• The item to be protected (tank on fire, tanks close to the tank on fire, tanks in the same bund than the tank on fire, the bund on fire and tanks in an other bund, close to the bund on fire)

• The fire-fighting means (fixed water spray, water monitors, fixed foam generators, foam monitors, external mobile support).

The minimum fire fighting requirements are based on GESIP and NFPA 11 recommendations (for more details refer to GS EP SAF 334 (“Foam fire extinguishing systems”) and can be summarised as follows:

• Cooling: 15 l/min/m of skirt circumference of foam solution

• Extinguishing

- Fixed roof or internal floating roof: injection into the tank at a rate of 2.5 l/min/m2 for fluids B, C1 and D1, 2 l/min/m2 for fluids C2, nothing for fluids D2

- External floating roof: application of the rim seal at a rate of 7.5 l/min/m2 for fluids B, C1 and D1, 6 l/min/m2 for fluids C2, nothing for fluids D2

- Bund: FBA being the foam solution flow rate in l/min. to be applied directly onto the bund, is given by the formula FBA = S x q - Ft with:

S = Bund surface (m2) minus horizontal surface of the tank(s) in the bund






q = Foam solution application rate (2.5 l/min/m2 for fluids B, C1 and D1, 2 l/min/m2 for fluids C2

Ft = Foam solution flow rate applied onto the tank skirt (l/min).

6.5.2 Pressure vessels for liquefied hydrocarbons The fire-water flow rates for cooling effect Q1 (water) and extinguishing effect Q2 (concentrate + water = foam) depend on:

• The type of vessel (cylindrical or spherical) and the vessel capacity

• The type of foam (high-expansion, medium-expansion in windy areas, etc.)

• The fire scenario (cylindrical vessel on fire, spherical vessel on fire)

• The item to be protected (vessel on fire, vessels close to the vessel on fire, spherical vessels in the same bund than the vessel on fire)

• The fire-fighting means available (fixed water spray, water monitors, fixed foam generators, foam monitors, external mobile support).

With reference to French regulation, the fire-water flow rates for cooling effect Q1 and extinguishing effect Q2 can be summarised as follows:

• Cooling: 3 l/min/m2 of the total surface of the vessel

• Extinguishing: as per table below.

Overall storage capacity in the installation Q2 (m3/h)

Capacity < 1000 m3 40



Capacity ≥ 2500 m3 120

6.6 Fire-fighting application times The fire-water storage capacity shall allow to supply the largest fire-water flow rate for at least 6 hours (common rule of GS EP SAF 321 shall apply), taking into account the availability of an external support.

As a general rule the storage capacity of foam concentrate shall allow to supply foam for 20 minutes for the scenario tank on fire or 60 minutes for the scenario bund on fire, whichever is larger, and taking into account the availability of external support. In case external support is not available a specific study shall be carried out to determine whether foam application is indeed needed and for how it is needed. This issue shall be properly addressed in the SAFETY CONCEPT.

GS EP SAF 341 - LOCATION AND PROTECTION OF · PDF file• Type of storage tanks or ......

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