41012742 Plant Layout
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Plant Layout This Technical Measures Document refers to Plant Layout. Other relevant Technical Measures Documents are: Design Codes - Plant [1][1] Design Codes - Pipework [2][2] Plant Modification / Change procedures [3][3] Maintenance procedures [4][4] The relevant Level 2 Criteria are 5.2.1.3 (29) b [5][5] , 5.2.1.3 (29) g, h, i [6][6] and 5.2.1.6 (38) d [7][7] . General principles Plant layout is often a compromise between a number of factors such as: The need to keep distances for transfer of materials between plant/storage units to a minimum to reduce costs and risks; The geographical limitations of the site; Interaction with existing or planned facilities on site such as existing roadways, drainage and utilities routings; Interaction with other plants on site; The need for plant operability and maintainability; The need to locate hazardous materials facilities as far as possible from site boundaries and people living in the local neighbourhood; The need to prevent confinement where release of flammable substances may occur; The need to provide access for emergency services; The need to provide emergency escape routes for on-site personnel; The need to provide acceptable working conditions for operators. The most important factors of plant layout as far as safety aspects are concerned are those to: Prevent, limit and/or mitigate escalation of adjacent events (domino); Ensure safety within on-site occupied buildings; Control access of unauthorised personnel; Facilitate access for emergency services. In determining plant layout designers should consider the factors in outlined in the following sections.
Transcript of 41012742 Plant Layout
Plant LayoutThis Technical Measures Document refers to Plant Layout.Other relevant Technical Measures Documents are:
Design Codes - Plant[1][1]
Design Codes - Pipework[2][2]
Plant Modification / Change procedures[3][3]
Maintenance procedures[4][4]
The relevant Level 2 Criteria are 5.2.1.3 (29) b[5][5], 5.2.1.3 (29) g, h, i[6][6] and 5.2.1.6 (38)d[7][7].
General principlesPlant layout is often a compromise between a number of factors such as:
The need to keep distances for transfer of materials between plant/storage units to aminimum to reduce costs and risks;The geographical limitations of the site;Interaction with existing or planned facilities on site such as existing roadways, drainageand utilities routings;Interaction with other plants on site;The need for plant operability and maintainability;The need to locate hazardous materials facilities as far as possible from site boundariesand people living in the local neighbourhood;The need to prevent confinement where release of flammable substances may occur;The need to provide access for emergency services;The need to provide emergency escape routes for on-site personnel;The need to provide acceptable working conditions for operators.
The most important factors of plant layout as far as safety aspects are concerned are those to:
Prevent, limit and/or mitigate escalation of adjacent events (domino);Ensure safety within on-site occupied buildings;Control access of unauthorised personnel;Facilitate access for emergency services.
In determining plant layout designers should consider the factors in outlined in the followingsections.
Inherent safetyThe major principle in Inherent Safety is to remove the hazard altogether. The best method toachieve this is to reduce the inventory of hazardous substances such that a major hazard is nolonger presented. However, this is not often readily achievable and by definition no COMAHfacility will have done so. Other possible methods to achieve an Inherently Safer design are:
Intensification to reduce inventories;Substitution of hazardous substances by less hazardous alternatives;Attenuation to reduce hazardous process conditions i.e. temperature, pressure;Simpler systems/processes to reduce potential loss of containment or possibility of errorscausing a hazardous event;Fail-safe design e.g. valve position on failure.
Plant layout considerations to achieve Inherent Safety are mainly those concerned with dominoeffects (see below).
The Dow / Mond IndicesThese hazard indices are useful for evaluating processes or projects, ranking them againstexisting facilities, and assigning incident classifications. They provides a comparative measureof the overall risk of fire and explosion of a process, and are useful tools in the plant layoutdevelopment stage since they enable objective spacing distances to be taken into account at allstages.
The methodology for undertaking a rapid ranking method that is based on the Dow / Mondindex is detailed in ILO, PIACT, Major Hazard Control: A practical manual, 1988.
Although these are useful rule-of thumb methodologies for first consideration of plant layout,they do not replace risk assessment. The distances derived between plant units using thesesystems are based upon engineering judgement and some degree of experience rather thanany detailed analysis.
Domino effectsHazard assessment of site layout is critical to ensure consequences of loss of containment andchances of escalation are minimised. Domino may be by fire, explosion (pressure wave andmissiles) or toxic gas cloud causing loss of control of operations in another location.
FireA fire can spread in four ways:
Direct burning (including running liquid fires);Convection;Radiation;Conduction.
The spread of fire from its origin to other parts of the premises can be prevented by vertical andhorizontal compartmentation using fire-resisting walls and floors. Further information may befound in BS 5908 : 1990[8][8]. Consideration should also be given to the spread of flammablematerial via drains, ducts and ventilation systems. Delayed ignition following a release mayresult in spread of flames through such systems via dispersed flammable gases and vapours.
Protection against domino effects by convection, conduction and radiation can be achieved by
inherent safety principles i.e. ensuring that the distances between plant items are sufficient toprevent overheating of adjacent plants compromising safety of those plants also. Where this isnot possible due to other restrictions, other methods such as fire walls, active or passive fireprotection may be considered.
ExplosionExplosion propagation may be directly by pressure waves or indirectly by missiles. As for fires,inherently safe methods that should be considered are:
arranging separation distances such that damage to adjacent plants will not occur even inthe worst case;provision of barriers e.g. blast walls, location in strong buildings;protecting plant against damage e.g. provision of thicker walls on vessels;directing explosion relief vents away from vulnerable areas e.g. other plants or buildings,roadways near site boundaries.
However, the latter may not provide practical solutions, particularly against missiles, and riskanalysis may be required to prove adequate safety.
Toxic gas releasesToxic gas releases may cause domino effects by rendering adjacent plants inoperable andinjuring operators. Prevention/mitigation of such effects may be affected by provision ofautomatic control systems using inherently safer principles and a suitable control room (seesection below on Occupied Buildings).
Reduction of consequences of event on and off SiteIn addition to the measures described in the sections above, Plant Layout design techniquesapplicable to the reduction of the risks from release of flammable or toxic materials include:
Locating all high-volume storage of flammable / toxic material well outside process areas;Locating hazardous plant away from main roadways through the site;Fitting remote-actuated isolation valves where high inventories of hazardous materialsmay be released into vulnerable areas;Provision of ditches, dykes, embankments, sloping terrain to contain and control releasesand limit the safety and environmental effects;Siting of plants within buildings as secondary containment;Siting of plants in the open air to ensure rapid dispersion of minor releases of flammablegases and vapours and thus prevent concentrations building up which may lead to flashfires and explosions;Hazardous area classification for flammable gases, vapours and dusts to designate areaswhere ignition sources should be eliminated.
Risk management techniques should be used to identify control measures that can be adoptedto reduce the consequences of on or off site events. See references cited in further readingmaterial.
Positioning of occupied buildingsThe distance between occupied buildings and plant buildings will be governed by the need toreduce the dangers of explosion, fire and toxicity. In particular, evacuation routes should not be
blocked by poor plant layout, and personnel with more general site responsibilities shouldusually be housed in buildings sited in a non-hazard area near the main entrance. Considerationshould be given to siting of occupied buildings outside the main fence. In all cases occupiedbuildings should not be sited downwind of hazardous plant areas. Further guidance is availablein standard references.
Aggregation / trapping of flammable vapoursTo avoid aggregation and trapping of flammable / toxic vapours which could lead to a hazardousevent, buildings should be designed so that all parts of the building are well ventilated by naturalor forced ventilation. Flammable storages should be sited in the open air so that minor leaks orthermal outbreathing can be dissipated by natural ventilation. Maintenance procedures shouldinclude the displacement of vapours from hazardous areas before work begins (see TechnicalMeasures Document on Permit to Work Systems[9][9]).
Segregation of incompatible substances (particularly in warehouses / storage areas)This is detailed in the Technical Measures Document on Segregation of HazardousMaterials[10][10].
Status of guidanceAdditional material providing much insight into analysis of offsite consequences through a riskmanagement program is now available from the United States Environmental ProtectionAgency. This provides guidance on offsite consequence analysis for toxic gases, toxic liquids,and flammable substances.
Codes of Practice relating to Plant Layout
ʻProcess plant hazard and control building design: An approach to categorisation',Chemical Industries Association, 1990.CIA Guidance for the location and design of occupied building on chemical manufacturingsites, CIA/CISHEC, 1998.
BS 5908 : 1990[11][11] Code of practice for fire precautions in the chemical and alliedindustries, British Standards Institution.Section 5, Paragraph 21 provides guidance on the minimum distance that the building canbe placed from the site boundary. For some specific substances, HSE guidance notes orindustry codes of practice are available, giving separation distances such as those fromplant to site boundaries.Section 10, Paragraph 54.3 provides guidance on methods to reduce any flammable gasconcentrations below the lower limit, including the use of fixed water sprays or monitorspositioned in such a way as to aid the dispersion of the gas into the atmosphere.
HS(G)176 The storage of flammable liquids in tanks[12][12], HSE, 1998.Paragraphs 46 to 55 provide guidance on the siting of tanks.HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in totalcapacity)[13][13], HSE, 1990.Superseded by HS(G)176[14][14], Paragraph 12 provides guidance on the siting of tanks.
HS(G)51 Storage of flammable liquids in containers[15][15], HSE, 1990.HS(G)52 The storage of flammable liquids in fixed tanks (exceeding 10000 cu. m in totalcapacity)[16][16], HSE, 1991.Superseded by HS(G)176[17][17].
HS(G)28 Safety advice for bulk chlorine installations[18][18], HSE, 1999.Paragraphs 21-30 provide guidance on siting of bulk chlorine installations.HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical andcylindrical vessels[19][19], HSE,1986.Paragraph 155-160 provide guidance on siting of vessels for receiving tanker deliveries ofanhydrous ammonia.LPGA CoP 1 Bulk LPG storage at fixed installations. Part 1 : Design, installation andoperation of vessels located above ground, LP Gas Association, Revised Edition July1998 (includes Amendment 1, January 1999).Supersedes HS(G)34 Storage of LPG at fixed installations[20][20].Part 1 gives guidance on plant layout.
HS(G)34 Storage of LPG at fixed installations[21][21], HSE, 1987.Superseded by the above.Paragraphs 15 to 36 give guidance on plant layout.
Further reading materialILO, PIACT, 'Major Hazard Control: A practical manual', 1988.
The Environmental Protection Act (EPA), 1991.
The Water Resources Act, 1991.
The Water Industries Act, 1991.
The Town and Country Planning Act, 1990.
Mecklenburgh, J.C., 'Process Plant Layout', George Godwin, 1985.
Kaess, D., Jr., ʻGuide to Trouble-free Plant Layoutʼ, Chemical Engineering, pp 122-134, June 1,1970.
Meissner, R.E. III and Shelton, D.C., ʻPlant Layout: Part 1 Minimizing Problems in Plant Layoutʼ,The Ralph M. Parsons Co., Chemical Engineering, 99, 4, p81, April 1992.
Brandt, D., George, W., Hathaway, C. and McClintock, N., ʻPlant Layout: Part 2 The Impact ofCodes, Standards and Regulationsʼ, Davy-McKee Corp., Chemical Engineering, 99, 4, p89, April1992.
Kirk-Othmer, 'Encyclopaedia of Chemical Technology', Vol. 18: Plant Layout, pp23-43; PlantLocation, pp44-59; Plant Safety, pp60-86, Wiley, New York, 1982.
Kern, R., CE Refresher: Plant Layout, 12 Parts, Chemical Engineering, 23 May 1977 through 14August 1978.
Basusbacher, E. and Hunt, R., ʻProcess Plant Layout and Piping Designʼ, Auerbach Publishers,Boston, 1990.
Burklin, C.R., ʻSafety Standards, Codes and Practices for Plant Designʼ, Chemical Engineering,pp56-63, October 2, 1972.
EPA / CEPP, 'Risk Management Program Guidance for Offsite Consequence Analysis', RMPSeries, United States Environmental Protection Agency / Chemical Emergency Preparednessand Prevention Office, April 1999.
Konz, S., ʻWork Design: Industrial Ergonomicsʼ, New York: John Wiley and Sons, Inc., 1983.
Konz, S., ʻFacility Designʼ, New York: John Wiley and Sons, Inc., 1985.
Sule, D.R., ʻManufacturing Facilities: Location, Planning, and Designʼ, Boston, MA: PWS-KENTPublishing Co., 1988.
Lees, F.P., Loss Prevention in the Process Industries[22][22], Second Edition, 1996.
Section 8 provides guidance on Hazard Identification;
Section 10 provides guidance on Hazard Assessment including Domino Effects;
Section 10 provides guidance on Plant Siting and Layout.
Case studies illustrating the importance of Plant Layout
BASF Warehouse Fire (9/10/1995)[23][23]
Flixborough (Nypro UK) Explosion (1/6/1974)[24][24]
Hickson and Welch Ltd Fire (22/9/1992)[25][25]
Mexico City - Pemex LPG Terminal (19/11/1984)[26][26]
Pasadena - Phillips 66 (23/10/1989)[27][27]
Link URLs in this page
1. Design Codes - Planthttp://www.hse.gov.uk/comah/sragtech/techmeasplant.htm
2. Design Codes - Pipeworkhttp://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm
3. Plant Modification / Change procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm
4. Maintenance procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasmaintena.htm
5. 5.2.1.3 (29) bhttp://www.hse.gov.uk/comah/sram/index.htm
6. 5.2.1.3 (29) g, h, ihttp://www.hse.gov.uk/comah/sram/index.htm
7. 5.2.1.6 (38) dhttp://www.hse.gov.uk/comah/sram/index.htm
8. BS 5908 : 1990http://www.hse.gov.uk/comah/sragtech/docsbsi.htm
9. Permit to Work Systemshttp://www.hse.gov.uk/comah/sragtech/techmeaspermit.htm
10. Segregation of Hazardous Materialshttp://www.hse.gov.uk/comah/sragtech/techmeassegregat.htm
11. BS 5908 : 1990http://www.hse.gov.uk/comah/sragtech/docsbsi.htm
12. HS(G)176 The storage of flammable liquids in tankshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
13. HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in totalcapacity)
http://www.hse.gov.uk/comah/sragtech/docspubguid.htm14. HS(G)176
http://www.hse.gov.uk/comah/sragtech/docspubguid.htm15. HS(G)51 Storage of flammable liquids in containers
http://www.hse.gov.uk/comah/sragtech/docspubguid.htm16. HS(G)52 The storage of flammable liquids in fixed tanks (exceeding 10000 cu. m in total
capacity)http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
17. HS(G)176http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
18. HS(G)28 Safety advice for bulk chlorine installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
19. HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical andcylindrical vesselshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
20. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
21. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
22. Loss Prevention in the Process Industrieshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
23. BASF Warehouse Fire (9/10/1995)http://www.hse.gov.uk/comah/sragtech/casebasf95.htm
24. Flixborough (Nypro UK) Explosion (1/6/1974)http://www.hse.gov.uk/comah/sragtech/caseflixboroug74.htm
25. Hickson and Welch Ltd Fire (22/9/1992)http://www.hse.gov.uk/comah/sragtech/casehickwel92.htm
26. Mexico City - Pemex LPG Terminal (19/11/1984)http://www.hse.gov.uk/comah/sragtech/casepemex84.htm
27. Pasadena - Phillips 66 (23/10/1989)http://www.hse.gov.uk/comah/sragtech/casepasadena89.htm
Link URLs in this page
1. Design Codes - Planthttp://www.hse.gov.uk/comah/sragtech/techmeasplant.htm
2. Design Codes - Pipeworkhttp://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm
3. Plant Modification / Change procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm
4. Maintenance procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasmaintena.htm
5. 5.2.1.3 (29) bhttp://www.hse.gov.uk/comah/sram/index.htm
6. 5.2.1.3 (29) g, h, ihttp://www.hse.gov.uk/comah/sram/index.htm
7. 5.2.1.6 (38) dhttp://www.hse.gov.uk/comah/sram/index.htm
8. BS 5908 : 1990http://www.hse.gov.uk/comah/sragtech/docsbsi.htm
9. Permit to Work Systemshttp://www.hse.gov.uk/comah/sragtech/techmeaspermit.htm
10. Segregation of Hazardous Materialshttp://www.hse.gov.uk/comah/sragtech/techmeassegregat.htm
11. BS 5908 : 1990http://www.hse.gov.uk/comah/sragtech/docsbsi.htm
12. HS(G)176 The storage of flammable liquids in tankshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
13. HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in totalcapacity)http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
14. HS(G)176http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
15. HS(G)51 Storage of flammable liquids in containershttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
16. HS(G)52 The storage of flammable liquids in fixed tanks (exceeding 10000 cu. m in totalcapacity)http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
17. HS(G)176http://www.hse.gov.uk/comah/sragtech/docspubguid.htm
18. HS(G)28 Safety advice for bulk chlorine installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
19. HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical andcylindrical vesselshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
20. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
21. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
22. Loss Prevention in the Process Industrieshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm
23. BASF Warehouse Fire (9/10/1995)http://www.hse.gov.uk/comah/sragtech/casebasf95.htm
24. Flixborough (Nypro UK) Explosion (1/6/1974)http://www.hse.gov.uk/comah/sragtech/caseflixboroug74.htm
25. Hickson and Welch Ltd Fire (22/9/1992)http://www.hse.gov.uk/comah/sragtech/casehickwel92.htm
26. Mexico City - Pemex LPG Terminal (19/11/1984)http://www.hse.gov.uk/comah/sragtech/casepemex84.htm
27. Pasadena - Phillips 66 (23/10/1989)http://www.hse.gov.uk/comah/sragtech/casepasadena89.htm
