SP-1127 Plant Layout and Spacing Specification - Version 3 FINAL
Short Description
Plant Layout Guide...
Description
RESTRICTED Oct-10
Document ID: SP-1127 Filing Key: Business Control
Petroleum Development Oman L.L.C.
Technical Safety Engineering Specification for Facility Siting, Layout and Spacing User Note: The requirements of this document are mandatory. Non-compliance shall only be authorised by the Document Owner or his Delegate through STEP-OUT approval. A controlled copy of the current version of this document is on PDO's EDMS. Before making reference to this document, it is the user's responsibility to ensure that any hard copy, or electronic copy, is current. For assistance, contact the Document Custodian or the Document Controller. Users are encouraged to participate in the ongoing improvement of this document by providing constructive feedback.
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i
Revision: 3.0 Effective: October 2010
Document Authorisation
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ii Revision History The following is a brief summary of the 4 most recent revisions to this document. Details of all revisions prior to these are held on file by the issuing department. Version No. Version 3.0
Date Oct 10
Author Ian Jewitt (MSE4)
Version 2.0 Version 1.0
Jun 04 Jun 99
A.C. Sluijterman (UEP1) A.C. Sluijterman (UEP1)
Scope / Remarks Updated to bring in line with current industry practice i.e. GE GAP.2.5.2, UK HSE CD211, API RP 752 and API RP 753 Revalidation and update references Specification developed from ERD-09-03 “Layout and Spacing of Plant Equipment and Facilities”
iii Related Business Processes Code DEP 30.00.60.13 DEP 31.40.00.10 DEP 31.76.10.10 DEP 34.17.10.30 DEP 34.17.10.33 DEP 34.17.10.35 DEP 80.45.10.10
Business Process (EPBM 4.0) Human factors engineering – valve analysis Pipeline engineering (amendments / supplements to ISO 13623) Heating, ventilation and air conditioning for plant buildings Blast resilient and blast resistant control buildings/field auxiliary rooms Portable blast-resistant modules Siting of onshore occupied portable buildings Design of pressure relief, flare and vent systems
iv Related Corporate Management Frame Work (CMF) Documents The related CMF Documents can be retrieved from the Corporate Business Control Documentation Register TAXI. Code CP-117 SP-1075 SP-1126 SP-1190 SP-1258 PR-1172
Page 4
Business Process (EPBM 4.0) Project Engineering Code of Practice Fire and Explosion Risk Management Drain Systems Specification Design for Sour Service Specification Quantitative Risk Assessment Permit to Work Procedure
Specification for Facility Siting, Layout and Spacing
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TABLE OF CONTENTS i
Document Authorisation ......................................................................................................... 3
ii
Revision History ..................................................................................................................... 4
iii
Related Business Processes ................................................................................................. 4
iv
Related Corporate Management Frame Work (CMF) Documents ........................................ 4
1
Introduction ............................................................................................................................ 6
2
1.1
Introduction ....................................................................................................................... 6
1.2
Purpose ............................................................................................................................ 6
1.3
Scope ............................................................................................................................... 6
1.4
General Definitions ........................................................................................................... 6
1.5
Review and Improvement................................................................................................. 7
Requirements for Facility Siting ............................................................................................. 8 2.1
3
4
General ............................................................................................................................. 8
Facility Layout and Spacing Requirements .......................................................................... 10 3.1
General ........................................................................................................................... 10
3.2
Overall Plant Layout ....................................................................................................... 14
3.3
Process Units ................................................................................................................. 15
3.3.1
Hazard Classification .................................................................................... 15
3.3.2
Intra-Unit Spacing ......................................................................................... 15
3.4
Utilities ............................................................................................................................ 16
3.5
Process Plant Permanent Buildings ............................................................................... 17
3.6
Services .......................................................................................................................... 18
3.7
Process Plant Portable Buildings ................................................................................... 18
3.8
Loading and Unloading................................................................................................... 19
3.9
Flares ............................................................................................................................. 19
3.10
Tank Farms .................................................................................................. 19
3.11
Storage Tanks and Vessels.......................................................................... 20
3.12
Pressurised and Refrigerated Storage Tanks .............................................. 21
3.13
Pig Launcher / Receivers ............................................................................. 21
Appendix A ........................................................................................................................... 22 4.1
Appendix 1, Glossary of Definitions, Terms and Abbreviations ..................................... 22
4.2
Appendix 2, Buildings Intended for Occupancy.............................................................. 24
4.2.1
Buildings Inteded for Occupancy .................................................................. 24
4.2.2
Excluded Buildings ....................................................................................... 24
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1 Introduction 1.1
Introduction Process Safety experience shows that fires or explosions in congested areas of oil and gas facilities can result in harm to people, extensive asset damage and loss of company reputation. Wherever flammable hazards exist, proper facility siting, layout and adequate spacing between hazards are essential to loss prevention and control. Facility siting addresses the siting of on-plot and off-plot facilities and supporting infrastructure such as camps, clinics and roads, Layout relates to the relative position of process units within a given facility. Spacing pertains to minimum distances between equipment within a process unit.
1.2
Purpose The purpose of this specification is to establish minimum requirements for the siting of hydrocarbon facilities and the layout of process units and arrangement of process equipment. This specification shall be used for the development of plans, electronic models, and working drawings for on-plot and off-plot hydrocarbon facilities, based on the results of physical effects modelling. The intent is for this specification to be coordinated with the overall site selection and layout development process.
1.3
Scope This facility siting, layout and spacing specification is for the protection of people and asset loss prevention only, and is intended for modifications to existing and design of new oil and gas facilities. This specification is intended to limit explosion overpressure and fire exposure damage, and to mitigate the consequences of toxic releases on people. The specification does not address shrapnel damage. If these requirements cannot be followed, then additional loss prevention measures, such as fire proofing, blast hardening, active fire protection, or dumping liquid inventories may be necessary. Similarly, if the toxic protection requirements cannot be followed, then additional protection measures, such as shelters may need to be provided. Additional engineering or administrative controls required to reduce risk to ALARP are not described in this specification. Further guidance on facility siting, plant layout and spacing can be found in CCPS Guidelines for Facility Siting and Layout (2003).
1.4
General Definitions The lower-case word shall indicates a requirement. The capitalised term SHALL [PS] indicates a process safety requirement. The word should indicates a recommendation.
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Review and Improvement Any user of this document who encounters a mistake or confusing entry is requested to immediately notify the Document Custodian using the form provided in CP-117 ”Engineering Code of Practice”. This document shall be reviewed as necessary by the Document Custodian, but no less frequently than every four years. Triggers for full or partial review of this Specification are listed in CP-117 “Engineering Code of Practice”.
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2 Requirements for Facility Siting 2.1
General The following items shall be considered when developing overall site plans for process facilities: Emergency response requirements (e.g., fire response, medical response, rescue, multi-casualty triage, command and control centres, temporary and permanent places of safety, etc.) Legal boundaries Security threats Adjacent land usage Nearby public facilities Public roads Public utilities Local regulations (e.g., noise, air emissions, water fate, etc.) Wadis Meteorology Site data (e.g., contaminated soil, seismic, wetlands, flora and fauna, archeological sites, etc.) Topography Future field development (e.g. exploration drilling, development drilling, well servicing, planned shutdowns, facility expansion, new facility development, etc.) Routing and inventory of hazardous fluids in flowlines, bulklines and pipelines The initial,site selection should be based on exposure from uncontrollable factors, such as floods, earthquakes, local population, tidal waves, subsidence, hurricanes, major wadis, and adjacent hazardous facilities. The process hazards from the development SHALL [PS] be assessed to establish the safety zones around the on-plot and off-plot facilities where implications exist for permanent public buildings and sites, emergency planning is required, or where restrictions on developments or Company operations may be required. The extent of the safety zones SHALL [PS] be based on the results of physical effects modelling in a Concept Risk Assessment developed in accordance with SP-1258. In addition, Annex C of DEP 31.40.00.10-Gen. shall be consulted for minimum distances between pipelines and normally occupied buildings. Figure 1 in this specification illustrates the safety zones around a typical process facility that does not contain inventories of highly toxic materials such as Hydrogen Sulphide (H2S). Figure 2 illustrates the basis for safety zones determined in a Concept Risk Assessment.
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Figure 1: Typical Safety Zone Distances Around Sweet Facilities
Figure 2: Summary of the Risk Basis for Safety Zones Around Facilities
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3 Facility Layout and Spacing Requirements 3.1
General The following aspects shall be considered when determining the facility layout and the process unit separation required: High hazard operations Grouped operations Critical operations Number of personnel at risk Potential environmental damage Concentration of property and business interruption values Importance of facility for continuing operations Equipment replacement and installation time Interdependency of facilities Critical customer or supplier relationships Fire and explosion impacts Corrosive or incompatible materials exposures Vapour cloud explosions due to release of large flammable inventories including e.g. overfill of condensate tanks Sources of ignition Maintenance and emergency accessibility Operations and maintenance philsophies, particularly the exposure of teams involved in turnaround maintenance, while adjacent equipment is operating Drainage and grade sloping Prevailing wind conditions Natural hazards and climate Future expansions Construction site requirements including minimising risk to construction workers and from construction activity in live process facilities External exposures including other facilities, pipelines and transportation (e.g. motor vehicle, aircraft, ship, etc.) The process hazards and effects shall be assessed to establish the separation distance required between process units (inter-unit spacing) and equipment (intra-unit spacing). Tables 1, 2 and 3 in this specification should be consulted for minimum spacing guidelines to develop an initial layout that mitigates flammable hazards. The minimum spacing guidelines are for initial layout development prior to a Fire and Explosion Assessment. The final inter-unit spacing SHALL [PS] be based on the results of physical effects modelling in a Fire and Explosion Assessment.
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/
Motor Control Centres and Electrical Substations
/
/
Utilities Areas
15
15
/
Inlet / Outlet ESD Valves
30
30
30
Fire Stations
Fire Water Pumps
Unloading and Loading Racks
Flares
Pressure Storage Tanks
Atmospheric Storage Tanks
Process Units High Hazard
Process Units Intermediate Hazard
Process Units Moderate Hazard
Wellheads
Trailers, Portacabins, Containerized Buildings
Control Rooms
Inlet / Outlet ESD Valves
Utilities Areas
Motor Control Centres and Electrical Substations
Service Buildings (Permanent) Service Buildings (Permanent)
Refrigerated Storage Tanks Dome Roof
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/
Control Rooms
/
/
30
30
/
Trailers, Portacabins, Containerized Buildings
6
15
150
150
6
6
Wellheads
95
95
95
95
95
150
95
Process Units Moderate Hazard
30
30
30
30
30
150
95
15
Process Units Intermediate Hazard
60
30
30
30
60
150
95
30
30
Process Units High Hazard
120
60
60
30
90
150
95
60
60
60
Atmospheric Storage Tanks
75
75
75
30
75
150
95
75
90
105
*
Pressure Storage Tanks
105
105
105
30
105
150
105
105
105
105
*
*
Refrigerated Storage Tanks Dome Roof
105
105
105
30
105
150
105
105
105
105
*
*
*
Flares
90
90
90
30
90
150
95
90
90
90
90
120
120
/
Unloading and Loading Racks
60
60
60
30
60
150
95
60
60
90
75
105
105
90
15
Fire Water Pumps
15
15
15
30
15
15
95
60
90
90
105
105
105
90
60
/
Fire Stations
15
15
15
30
15
15
95
60
90
90
105
105
105
90
60
/
/
Table 1: Inter-Unit Spacing Guidelines for Oil and Gas Facilities (adapted from GE GAP.2.5.2, API RP 753 and SP-1127 Version 2) / = no spacing requirements * = spacing given in Table 3 Distances in metres
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Compressors
10
Moderate Hazard Pumps
10
1.5
Intermediate Hazard Pumps
15
1.5
1.5
Overhead Power Lines (OHLs)
30
30
30
15
Columns, Accumulators, Drums
15
5
5
30
5
Rundown Tanks
30
30
30
30
30
30
Fired Heaters, Incinerators
30
15
15
30
15
30
10
Air Cooled Heat Exchanger
10
5
5
30
5
30
15
/
Heat Exchangers
10
5
5
30
5
30
15
5
1.5
Pipe Racks
10
5
5
30
5
30
15
/
5
/
Unit ESD Valves
15
15
15
30
15
30
15
15
15
15
/
Analyser Rooms
15
15
15
30
15
30
15
15
15
15
/
Analyser Rooms
Unit ESD Valves
Heat Exchangers
Air Cooled Heat Exchanger
Fired Heaters, Incinerators, Oxidisers
Rundown Tanks
Columns, Accumulators, Drums
Overhead Power Lines (OHLs)
Intermediate Hazard Pumps
Moderate Hazard Pumps
Compressors
Pipe Racks
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/
Table 2: Intra-Unit Spacing Guidelines for Oil and Gas Facilities (adapted from GE GAP.2.5.2 and SP-1127 Version 2) / = no spacing requirements Distances in metres
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0.5 D
Floating & Cone Roof Tanks > 3000 < 10,000 Barrels
0.5 D
0.5 D
Floating Roof Tanks > 10,000 < 300,000 Barrels
1.0 D
1.0 D
1.0 D
Jumbo Floating Roof Tanks > 300,000 Barrels
1.0 D
1.0 D
1.0 D
1.0 D
Cone Roof Tanks Class II, III Product > 10,000 < 300,000 Barrels
0.5 D
0.5 D
1.0 D
1.0 D
0.5 D
Cone Roof Tanks Inerted Class I Product > 10,000 10,000 10,000 < 300,000 Barrels
Jumbo Floating Roof Tanks > 300,000 Barrels
Floating Roof Tanks > 10,000 < 300,000 Barrels
Floating & Cone Roof Tanks > 3000 < 10,000 Barrels
Floating & Cone Roof Tanks < 3000 Barrels
Floating & Cone Roof Tanks < 3000 Barrels
Pressure Storage Vessels, Spheres and Spheroids
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1.0 D
Pressure Storage Vessels, Spheres and Spheroids
1.5 D 1.5 D 1.5 D 30m min 30m min 30m min
2.0 D
1.5 D 1.5 D 1.0 D 30m min 30m min 15m min
Pressure Storage Vessels Drums and Bullets
1.5 D 1.5 D 1.5 D 30m min 30m min 30m min
2.0 D
1.5 D 1.5 D 1.0 D 30m min 30m min 30m min
Refrigerated Dome Roof Storage Tanks
2.0 D 2.0 D 2.0 D 60m min 60m min 60m min
2.0 D
2.0 D 2.0 D 1.0 D 1.0 D 1.0 D 60m min 60m min 30m min 30m min 30m min
1.0 D
Table 3: Storage Tank Spacing Guidelines for Oil and Gas Facilities (adapted from GE GAP.2.5.2) D = largest tank diameter 1 barrel = 42 gallons = 159 L * For NFPA 30 Class II, III products, 2 m spacing is acceptable ** For NFPA 30 Class II or III operating at temperatures > 93°C
Where flammable vapours could be released and jet fires could occur, potential thermal radiation contours SHALL [PS] be estimated per SP-1258 as part of the Fire and Explosion Assessment. As a guideline, a medium hole size, represented by a 22 mm diameter hole, is typically the worst case scenario for equipment damage when accounting for isolation and depressuring. Critical equipment of adjacent process units 2 SHALL [PS] not be located within the 37.5 kW/m thermal radiation contour, without adequate mitigation. Where large inventory of flammable vapours could be released and a vapour cloud explosion or a Boiling Liquid Expanding Vapour Explosion (BLEVE) could occur, potential vapour cloud explosion overpressure contours SHALL [PS] be estimated per SP-1258 as part of the Fire and Explosion Assessment. The minimum spacing required between process units shall be based upon the following criteria:
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Critical equipment of adjacent process units shall not be located within the 0.21 bar overpressure contour. Equipment or structures of adjacent process units within the 0.07 bar overpressure contour shall be designed to withstand the calculated vapour cloud overpressure.
Where large flammable liquid inventories are present, potential thermal radiation effects from liquid pool fires SHALL [PS] be estimated per SP-1258 as part of the Fire and Explosion Assessment. Critical equipment of adjacent process units shall not be located 2 within the 8 kW/m thermal radiation contour, without adequate mitigation.
3.2
Overall Plant Layout Layout and spacing should be arranged to reduce the effect of the following controllable and uncontrollable factors that contribute to losses: Uncontrollable factors include site slope, climate, exposure to natural hazards, wind direction and force. However, locating ignition sources upwind of potential vapour leaks or locating the tank farm downhill of essential units may reduce the loss potential from an explosion or fire. Controllable factors include process design parameters, process equipment design, unloading facilities, maintenance, spare parts supply, control logic and automation, ignition sources, fire protection design, spare production capacity, flammable liquid holdups, spill control and the type of process. Use proper drainage and separation to control spills and fire spread. Refer to SP-1126 and DEP 80.45.10.10. A Fire and Explosion Assessment SHALL [PS] address each facility operation to help establish the layout or orientation of process unit battery limits within the facility. The selected layout should minimise the risk to people, overall property damage and related business interruption should an incident occur. The principles of H2S management and additional requirements for the layout of plant in high risk sour service are detailed in SP-1190. Since each area or unit block would typically have a rectangular shape, the maximum unit size should be limited to 90 m x 180 m for firefighting purposes. Vehicle access routes shall be provided between process units to allow each section of the facility to be accessible from at least two directions. In addition: Dead end vehicle access routes should be avoided by design. Vehicle access route widths and clearances shall be sized to handle large moving equipment and emergency vehicles or to a minimum of 8.5 m, whichever is greater. Sufficient overhead and lateral clearances should be provided for vehicles and cranes to avoid hitting piping racks, pipe ways, tanks or hydrants. Hydrants and monitors shall be located along vehicle access routes to allow easy hook-up of firefighting vehicles at FERM strategy 3 facilities (see SP-1075). A minimum of two entrances to the facility shall be provided for emergency vehicles to prevent the possibility of vehicles being blocked during an incident. The space between battery limits of adjoining units should be kept clear and open. The clear area between units should not be considered as a future area for process expansion.
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Process Units The process hazards should be classified as high, intermediate, or moderate hazard groups as defined in section 3.3.1. Based on the classification, Table 1 should be consulted to determine the initial spacing required between the various process units based upon the relative hazard of each process. The finalised spacing SHALL [PS] be based on a Fire and Explosion Assessment. Equipment or structures common to multiple process units should be located to prevent a single event from impairing the overall operation and causing extensive business interruption. Table 2 should be used for determining the initial minimum spacing within process units. The spacing distances should be interpreted as the clear, horizontal distances between adjacent edges of equipment. The finalised spacing SHALL [PS] be based on a Fire and Explosion Assessment.
3.3.1
Hazard Classification The following hazard classifications should be applied when using Tables 1 and 2: „Process Units Moderate Hazard‟ include units containing equipment processing flammable fluids up to 30 bara. „Process Units Intermediate Hazard‟ include units containing equipment processing flammable fluids between 30 bara and 180 bara. „Process Units High Hazard‟ include units containing equipment processing flammable fluids above 180 bara. „Intermediate Hazard Pumps‟: o Handle flammable or combustible liquids and operate at temperatures above 260°C or above the product autoignition temperature; o Handle flammable or combustible liquids and operate at pressures above 30 bar; or o Handle liquefied flammable gases. „Moderate Hazard Pumps‟: All other pumps handling flammable or combustible liquids.
3.3.2
Intra-Unit Spacing For intra-unit layout, the following principles apply: Pumps and compressors handling flammable products should not be grouped in one single area. Pumps and compressors SHALL [PS] not be located under piperacks, air cooled heat exchangers or vessels. Pump and driver axes shall be oriented perpendicular to piperacks or other equipment to minimise fire exposure in case of a pump seal failure. Compressors SHALL [PS] be located at least 30 m downwind from fired heaters and at least 7.5 m from any other exposing equipment. To avoid unnecessary exposure, lube oil tanks and pumps shall not be located directly under any compressor. Heaters and furnaces should not be incorporated into other associated process units or at least should be located at one corner of the unit.
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Continuous ignition sources should be located upwind (prevailing wind) of the process units. Tanks, accumulators or similar vessels with flammable liquid holdups should be located at grade. Stacking of equipment in process structures should be limited to equipment with no fire potential. Finished site grading and paved areas SHALL [PS] be sloped to avoid the pooling of liquid hydrocarbons below piperacks or potential ignition sources such as fired heaters. The ground surface should be sloped so that liquids drain away from the centre of a process unit. Open drains SHALL [PS] not be located under piperacks. Cable trays should be located in the top tier of the piperacks. Overhead power lines SHALL [PS] be located at least 30 m from process units and pipe racks. Facility inlet / outlet ESD valves SHALL [PS] be located at least 30 m from process units at the battery limit of the facility. Process unit ESD and EDP valves should be located outside the fire hazardous zone or protected to remain operable for at 15 minutes or longer depending on the design of the isolation and depressuring system.
3.3.3
Access and egress Wherever it does not conflict with loss control, accessibility for maintenance and operations shall be considered in determining spacing and layout: Equipment needing frequent overhaul, maintenance or cleaning should be located at process unit boundaries. Large vessels or equipment should be located close to unit boundaries to allow easy access of cranes. Access ways for operations and maintenance shall be a minimum of 3 m wide and unrestricted. Maintenance access shall be provided to allow for dismantling of equipment, e.g. access is required to pulled out reciprocating compressor rods and heat exchanger tube bundles. Means of emergency escape in the event of a fire, gas leak or other dangerous occurrence, SHALL [PS] be provided from all structures and plant areas. Escape routes and exits shall be incorporated into the overall facility layout. Where practical there should be at least two escape routes from every location within the facility, and these routes should be in different directions so that personnel can always retreat from the danger. The length of escape routes should be kept to a minimum, and emergency exits from the facility should lead to safer assembly areas. Dead end should be avoided, i.e. areas with only one exit. The selection between ladders or stairs shall be based on the required tasks and frequency of these tasks. Stairs shall serve as the primary access and egress to main operating levels in structures, buildings, and furnaces. Accessways shall be provided where plant personnel are likely to pass through while carrying out routine duties. Valves shall be located so that the operator is provided with a safe and easy access for operation, inspection, readings and maintenance. Valves shall not be acessed by standing on, or with the aid of, adjacent pipe-work, insulation, pipe-racks, cable
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trays, handrails, or any other equipment or object. See DEP 30.00.60.13-Gen for guidance on valve accessibility.
3.4
Utilities Central services, such as boilers, power stations and electrical substations, should be located away from hazardous areas so they will not be affected by a fire or explosion within the plant nor be a source of ignition for any potential flammable liquid or gas release. Electrical substations and motor control centres should be properly pressurised in accordance with DEP 31.76.10.10 or separated from sources of flammable vapours or gasses. Substations should be located away from hazardous areas to increase the reliability of the power supplies in case or a process fire or explosion. Electrical distribution cables shall be buried to limit their exposure to explosions, fires, storms and vehicles, and to ease firefighting accessibility. The segregation between utilities shall consider the effects of contaminating air intakes with air emissions or hydrocarbon release sources e.g. instrument air intake shall be located away from diesel generator exhausts.
3.5
Process Plant Permanent Buildings Buildings covered by this section are rigid structures intended for permanent use in fixed locations. This section addresses both buildings intended for occupancy and unmanned buildings. Examples of buildings intended for occupancy are listed in Appendix 2. Occupied buildings should be located according to the following principles: locate personnel away from process areas consistent with safe and effective operations; minimise the use of buildings intended for occupancy in close proximity to process areas; manage the occupancy of buildings in close proximity to process areas; design, construct, install, modify, and maintain buildings intended for occupancy to protect occupants against explosion, fire, and toxic material releases; manage the use of buildings intended for occupancy as an integral part of the design, construction, maintenance, and operation of a facility. When siting new buildings intended for occupancy, the building should be located where it could not be exposed by fires, explosions or toxic materials. Process plant permanent buildings SHALL [PS] be considered to be exposed to major process hazards, when: Explosion peak side-on over-pressure > 50 mbar Thermal radiation (long duration) > 8 kW/m
2
Flammable gas concentration (long duration) > 0.4 LFL Hydrogen Sulphide concentration (long duration) > 100 ppm If separation to mitigate explosions is not feasible, blast loads SHALL [PS] be taken into account in selecting the type of building construction in accordance with DEP 34.17.10.30. Design blast loads SHALL [PS] be calculated in accordance with SP-1258 using a consequence-based or risk-based approach. Page 17
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If separation to mitigate fires is not feasible, there are two protection concepts to choose from i.e. “shelter-in-place for fire” or “evacuation for fire”. Designers SHALL [PS] choose at least one of these concepts. The concept for protection of building occupants from fire hazards SHALL [PS] be reflected in the site emergency response plan, building design features, and escape route design. When a “shelter-in-place for fire” concept is chosen for a building intended for occupancy, designers SHALL [PS] determine the fire resistance requirements using either a consequence-based or risk-based approach in accordance with SP-1258. In addition, if the building could be exposed to smoke or an external flammable mixture, the building SHALL [PS] have features to prevent infiltration and formation of smoke or a flammable mixture inside the building, in line with DEP 31.76.10.10. When the “evacuation for fire” concept is chosen, designers SHALL [PS] provide emergency exits and safe evacuation routes to a designated “shelter-in-place” or specified assembly area. If separation to mitigate toxic release is not feasible, there are two protection concepts to choose from i.e. “shelter-in-place for toxic material release” or “evacuation for toxic material release”. Designers SHALL [PS] choose at least one of these concepts. The selected concept for the protection of building occupants from toxic materials SHALL [PS] be reflected in the site emergency response plan, building design features and escape route design. When the “shelter-in-place for toxic materials release” concept is chosen, designers SHALL [PS] design the building in accordance with SP-1190. Buildings designed to provide “shelter-in-place” protection for facility workers and designated as Temporary Safe Refuges shall be located no further than the maximum travel distance for a worker wearing an escape set; taking into account escape routes, the breathing air capacity of the escape set and typical traverse speeds of: o
1 m/s on level walkways
o
0.8 m/s on stairs
o
0.3 m/s on ladders
Control rooms, motor control centres, and other essential facilities should be located to allow operators to safely shut down units under emergency conditions. Where control rooms could be exposed to fires or blast overpressures, the CCR and LECC SHALL [PS] be located in a safe area. Unmanned satellite computer rooms, terminal rooms and i/o rack rooms are considered to be equivalent to motor control centres for the purpose of this specification.
3.6
Services Warehouses, laboratories, shops, fire stations and offices SHALL [PS] be located away from process areas, to minimise “uncontrollable ignition sources” and the number of personnel at risk to process hazards. The segregation of non-process permanent buildings from process areas SHALL [PS] be verified by the Fire and Explosion Assessment. The thermal radiation criteria for non-process permanent buildings shall be 2 5 kW/m (short duration) to allow for escape. Other criteria are the same as for process permanent buildings listed in section 3.5.
3.7
Process Plant Portable Buildings Occupied permanent buildings (e.g. control rooms, operator shelters) located near covered process areas are typically constructed to be blast and fire resistant. In contrast, conventional portable buildings (i.e. portacabins, trailers and containerised buildings) are typically not constructed to be blast and fire resistant. Past explosion accidents have
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Specification for Facility Siting, Layout and Spacing
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Revision: 3.0 Effective: October 2010
demonstrated that occupants of conventional portable buildings are susceptible to injuries from structural failures, building collapse, and building debris and projectiles. The following questions should be addressed when considering placement of a portable building near a covered process area: Do personnel need to be located near a covered process area? Do personnel need to occupy a portable building? Can the portable building be placed further from the covered process area, while allowing the occupants to effectively perform their tasks? Portable buildings SHALL [PS] not be located within bund walls used for product containment. Portable buildings that are intended to be occupied SHALL [PS] be evaluated for siting relative to explosion, fire, and toxic release hazards in accordance with SP-1258. For sites that do not have a validated risk-based assessment; all portable buildings, including without limitation standard construction portable buildings and portable buildings that are steel panelled shipping containers, SHALL [PS] be sited at least 150 m from the boundary of a process unit. Tents, fabric enclosures, and other soft-sided structures are not considered to be process plant portable buildings. There is not a required separation distance between a tent and process units and flares that are shutdown and depressured if administrative controls are in place to prevent occupancy when the equipment is in operation. The location of crane operations is to be considered when siting the location of the tent. The tent shall be located outside the range of any crane‟s boom during normal crane operations. Small open sided tents used as cool down areas for less than ten people within a hydrocarbon facility are not subject to design layout restrictions.
3.8
Loading and Unloading Space loading racks shall be located well away from other areas due to large numbers of vehicles carrying large amounts of flammable or combustible liquids. Loading and offloading operations shall be located at the plant perimeter close to the entry gate.
3.9
Flares Locate flares according to Table 1 or to DEP 80.45.10.10, whichever is greater. Where flares are adjacent to one another, the extent of spacing between flares and other process units shall be reviewed for the combined thermal radiation effects. Spacing between adjacent flares SHALL [PS] evaluate the effects of thermal radiation on the structural integrity of the flare system including stack.
3.10 Tank Farms Table 3 should be consulted for general requirements for spacing aboveground storage tanks. The spacing is given as a distance from tank shell to tank shell and is a function of the largest tank diameter. If there are adverse conditions, such as poor fire protection water supply, difficult firefighting, poor accessibility, poor diking or poor drainage, increase the spacing by at least 50%. Crude oil shall be treated as a flammable liquid in all cases. See Table 1 for minimum spacing between tank farms and other units. Different types of tanks and contents shall not be grouped or located within the same bund.
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Specification for Facility Siting, Layout and Spacing
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Revision: 3.0 Effective: October 2010
Storage tanks should be located at a lower elevation than other occupancies to prevent liquids or gases from flowing toward equipment or buildings and exposing them. Tanks should be located downwind of other areas. If this is not feasible, diversion dikes and increased separation may be required depending on slope, size of tanks, etc., to divert major flows resulting from tank rupture or boilover away from the process units. Atmospheric storage tanks and pressure vessels should be arranged in rows not more than two deep and adjacent to a road or accessway for adequate firefighting accessibility. Since piping involved in ground fires usually fails within 10 minutes of initial exposure, the amount of piping, valves and flanges located within bunds should be minimised. Pumps, valve manifolds, and transfer piping should be located outside bunds or tertiary containment areas. 3
Where tanks over 80,000 m are present, the minimum spacing distance between tanks shall be at least 305 m. All storage tanks containing volatile fluids have the potential to overfill resulting in a vapour cloud explosion. Examples of such fluids are natural gas liquids (condensates) and crude oils with a Reid Vapour Pressure (RVP) > 2.5 psi. The following separation distance between the bund wall of storage tanks containing volatile fluids and nonprocess permanent buildings SHALL [PS] be applied: Only warehousing without offices, outdoor storage, farm buildings and open parking areas shall be located within 150 m of the bund wall. Workshops or offices with less than 100 occupants and no more than three storeys shall not be located closer than 150 m from the bund wall. Workshops or offices with more than 100 occupants or more than three storeys shall not be located closer than 250 m from the bund wall. Accommodation up to 100 beds shall not be located closer than 250 m from the bund wall. There are no restrictions for buildings located more than 400 m from the bund wall. Tanks SHALL [PS] be spaced so the thermal radiation intensity from an exposing fire is too low to ignite the contents of the adjacent tanks. Typically, this is equivalent to 8 2 kW/m . Tolerances of tanks to thermal radiation can be increased by: Painting vessels a reflective color (generally white or silver). Providing a fixed water spray or tank shell cooling system for cooling adjacent tanks. Refer to SP-1075. Insulating or fireproofing the tank shell. Refer to SP-1075.
3.11 Storage Tanks and Vessels Internal floating roof tanks shall be classified as floating roof tanks when pontoon internal floaters are provided. When plastic, aluminum or a steel pan are used in the construction of the internal floater, the tank shall be classified as a cone roof tank for spacing purposes. Floating roof tanks for crude oil and flammable liquids (NFPA 30 Class I) in excess of 3 47,700 m should be arranged in a single row. If multiple rows are necessary, tanks SHALL [PS] be spaced farther than one diameter apart.
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3.12 Pressurised and Refrigerated Storage Tanks Spheres and spheroids: The spacing between groups of vessels should be at least 30 m or the largest tank diameter. The number of tanks in a group SHALL [PS] be limited to a maximum of six vessels. Drums and bullets: Horizontal pressurised storage vessels SHALL [PS] be limited to not 3 more than six vessels or 1136 m combined capacity in any one group. The spacing between groups of vessels should be at least 30 m or the largest tank diameter. Vessels should be aligned so that their ends are not pointed toward process areas or other storage areas, as these vessels tend to rocket if they fail during a fire. Multiple row configurations should be avoided. Pressurised storage vessels should not be located above each other. See also SP-1075. Refrigerated dome roof tanks: The spacing between groups of vessels should be at least 30 m or the largest tank diameter. The number of tanks in a group SHALL [PS] be limited to a maximum of six vessels.
3.13 Pig Launcher / Receivers Pig laucher / receivers should be aligned so that their ends are not pointed toward process areas or other storage areas, to mitigate the risk of firing a pig at live equipment.
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Specification for Facility Siting, Layout and Spacing
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Petroleum Development Oman LLC
Revision: 3.0 Effective: October 2010
4 Appendix A 4.1
Appendix 1, Glossary of Definitions, Terms and Abbreviations ALARP BLEVE CCPS CCR CFDH DCAF EDP ESD LECC LFL LPG MCC MCE MTBE NFPA RVP SIMOPs
As Low As Reasonably Practicable Boilding Liquid Expanding Vapour Explosion Center for Chemical Process Safety Central Control Room Corporate Function Discipline Head Discipline Controls & Assurance Framework Emergency Depressuring Emergency Shutdown Local Emergency Control Centre Lower Flammable Limit Liquified Petroleum Gas Motor Control Centre Maximum Credible Event Methyl Tert-Butyl Ether National Fire Protection Association Reid Vapour Pressure Simultaneous Operations
Blast load The load applied to a structure or object from a blast wave, which is described by the combination of overpressure and either impulse or duration. Building A rigid, enclosed structure. Building siting evaluation The procedures described in this document used to evaluate the hazards and establish the design criteria for new buildings and the suitability of existing buildings at their specific location. Confinement A physical surface that inhibits the expansion of a flame front of a burning vapor cloud in at least one direction. Examples include solid decks, walls, or enclosures. Congestion A collection of closely spaced objects in the path of the flame front that has the potential to increase flame speed to an extent that it can generate a damaging blast wave. Consequence The potential effects of an explosion, fire, or toxic material release. Consequence descriptions may be qualitative or quantitative. Consequence-based approach The methodology used for building siting evaluation that is based on consideration of the impact of explosion, fire, and toxic material release which does not consider the frequency of events. Essential personnel Personnel with specific work activities that require them to be located in buildings in or near a process area for logistical and response purposes. The identification of essential personnel will vary with operation and work activities including normal operation, start-up, and planned shutdown. Examples of essential personnel include, but are not limited to, Page 22
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operators and maintenance personnel. Examples of persons who are not essential personnel include, but are not limited to, designers, timekeepers, clerical staff, administrative support, and procurement staff. Hazard An inherent physical or chemical characteristic (e.g. flammability, toxicity, corrosivity, stored chemical energy, or mechanical energy) that has the potential for causing harm to people, property, or the environment. Inter-unit spacing The separation distance between process units. Intra-unit spacing The separation distance between equipment within a process unit. Maximum credible event (MCE) A hypothetical explosion, fire, or toxic material release event that has the potential maximum consequence to the occupants of the building under consideration from among the major scenarios evaluated. The major scenarios are realistic and have a reasonable probability of occurrence considering the chemicals, inventories, equipment and piping design, operating conditions, fuel reactivity, process unit geometry, industry incident history, and other factors. Each building may have its own set of MCEs for potential explosion, fire, or toxic material release impacts. Occupant vulnerability Proportion of building occupants that could potentially suffer a permanent disability or fatality if a potential event were to occur. On-site personnel Employees, contractors, visitors, service providers, and others present at the facility. Process area An area containing equipment (e.g. pipes, pumps, valves, vessels, reactors, and supporting structures) intended to process or store materials with the potential for explosion, fire, or toxic material release. Process unit A process unit has discrete boundaries that consist of the points where process fluid enters from the preceding oil and gas processing activity and where the treated process fluid is discharged to storage or for further processing. For example, a separation train is a process unit because a field gas stream enters the separation train, and separate product gas and natural gas liquids are discharged from the train. In another example, a gas dehydration unit is a process unit that may include a glycol contactor, recirculation pumps, glycol regenerator and associated heater even if it were broken down into three or four different skid-mounted pieces. Quantitative risk assessment The systematic development of numerical estimates of the expected frequency and consequence of potential accidents based on engineering evaluation and mathematical techniques. The numerical estimates can vary from simple values of probability/frequency of an event occurring based on relevant historical industry or other available data; to very detailed frequency modeling techniques. Risk A measure of potential injury, environmental damage, or economic loss in terms of both the incident likelihood and the severity of the loss or injury. Risk-based approach Page 23
Specification for Facility Siting, Layout and Spacing
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A quantitative risk assessment methodology used for building siting evaluation that takes into consideration numerical values for both the consequences and frequencies of explosion, fire, or toxic material release. Spacing tables approach The “spacing tables” approach uses established tables to determine minimum separation distances between equipment and buildings intended for occupancy. Industry groups, insurance associations, regulators, and owner/operator companies have developed experience-based spacing tables for minimum building spacing for fire. Toxic material An airborne agent that could result in acute adverse human health effects.
4.2
Appendix 2, Buildings Intended for Occupancy
4.2.1
Buildings Inteded for Occupancy A building is intended for occupancy if it has personnel assigned or it is used for a recurring group personnel function. Examples of buildings intended for occupancy include, but are not limited to: buildings which may become occupied during emergencies (e.g. buildings/rooms designated as shelter-in-place for fire and/or toxic material release, emergency command centers); change houses; conference rooms; control rooms; field operator buildings (i.e. buildings where operators are routinely located, sometimes referred to as “operator shelters”); guardhouses; laboratories with assigned personnel; lunchrooms; maintenance shops with assigned personnel; offices; orientation rooms; training rooms; warehouse buildings with assigned personnel; “buildings within buildings” (i.e. buildings intended for occupancy located within other buildings); rooms intended for occupancy (e.g. office, shop, control room) within an enclosed process area.
4.2.2
Excluded Buildings Categories and examples of structures and buildings excluded from building siting evaluation are shown as follows. Structures with roofs and no walls whose primary function is to provide limited protection to personnel from weather include, but are not limited to bus stops,
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pavilions, welding covers, truck loading canopies, covered walkways, smoking canopies. Enclosed process areas where only essential personnel are assigned to perform activities similar to those performed at an outdoor process area Buildings which do not have personnel assigned and require at most, only intermittent access. Examples of such buildings include, but are not limited to analyser buildings; field sampling/testing stations; electrical substations and motor control centres (MCCs); remote instrumentation enclosures; equipment enclosure buildings; abandoned buildings (i.e. removed from service, unused for any function, and no longer intended for occupancy); operator shelters with intermittent use; and buildings which primarily house materials.
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