Design Codes - PlantThis Technical Measures Document covers the design codes for plant. Reference is made torelevant codes of practice and standards.

The relevant Level 2 Criteria are:

5.2.1.5(35)a,b, c[1][1]

5.2.1.5(37)[2][2]

5.2.1.6(38)e, f, g[3][3]

5.2.1.7[4][4]

5.2.1.8[5][5]

5.2.1.10(55)[6][6]

5.2.1.12[7][7]

5.2.2.1[8][8]

This Technical Measures Document includes the following sections:

Introduction to Plant Design

General PrinciplesInherently Safer DesignDesign Assessments

General Considerations

Temperature and PressureMaterials of ConstructionCorrosion/Erosion

Specific Equipment - Mechanical Design

Pressure VesselsOther Vessels (including Storage Tanks)Reactor DesignHeat Exchange EquipmentFurnaces/BoilersRotating Equipment (including seals, vibration control)

Structural Design Considerations (including lightning)

Special Cases

Chlorine StorageAmmonia StorageLPG StorageHydrocarbons Storage

Construction of PlantCommissioning/Verification of Manufacture and Construction Standards

Reference is made to relevant codes of practice and standards where applicable.

Related Technical Measures Documents are Corrosion / Selection of Materials[9][9], DesignCodes - Pipework[10][10], Explosion Relief[11][11], Relief Systems / Vent Systems[12][12],Training[13][13], Plant Modification / Change Procedures[14][14], Reaction / ProductTesting[15][15].

Introduction to Plant design

General principlesThe design of a process plant is a complex activity that will usually involve many differentdisciplines over a considerable period of time. The design may also go through many stagesfrom the original research and development phases, through conceptual design, detailedprocess design and onto detailed engineering design and equipment selection. Many variedand complex factors including safety, health, the environment, economic and technical issuesmay have to be considered before the design is finalised - See Technical Measures Document -Training[16][16].

At each stage it is important that the personnel involved have the correct combination oftechnical competencies and experience in order to ensure that all aspects of the design processare being adequately addressed. Evidence of the qualifications, experience and training ofpeople involved in design activities should be presented in the Safety Report to demonstratethat the complex issues associated with design have been considered and a rigorous approachhas been adopted.

The process design will often be an iterative process with many different options beinginvestigated and tested before a process is selected. In many occasions a number of differentoptions may be available and final selection may depend upon a range of factors.

The process design should identify the various operational deviations that may occur and anyimpurities that may be present. In the mechanical design, the materials of construction chosenneed to be compatible with the process materials at the standard operating conditions andunder excursion conditions. The materials of construction also need to be compatible with eachother in terms of corrosion properties. Impurities which may cause corrosion, and the possibilityof erosion also need to be considered so that the detailed mechanical design can ensure thatsufficient strength is available and suitable materials of construction are selected for fabrication -See Technical Measures Document - Corrosion / Selection of Materials[17][17].

Detailed mechanical, structural, civil and electrical design of equipment comes after the initialprocess design which covers the steps from the initial selection of the process to be used,through to the issuing of process flow sheets. Such flowsheets will include the selection,specification and chemical engineering design of the equipment. These are then used as the

basis for the further detailed design.

This Technical Measures Document primarily considers the latter stages of the detailed designprocesses and identifies the detailed design issues, codes and applicable standards for themechanical design of equipment.

Design factors are an essential component in order to give a margin of safety in the design.Design factors may be appropriate in either the mechanical engineering design or in the processdesign where factors are often added to allow some flexibility in process operation. Formechanical and structural design the magnitude of design factors should allow for uncertaintiesin material properties, design methods, fabrication and operating loads.

Plant design should take account of the relevant codes and standards. Conformity betweenprojects can be achieved if standard designs are used whenever practicable.

Codes and StandardsModern engineering codes and standards cover a wide range of areas including:

Materials, properties and compositions;Testing procedures; for example for performance, compositions and quality;Preferred sizes; for example for tubes, plates and standard sections;Design methods and inspection and fabrication;Codes of practice for plant operation and safety.

Many companies have their own in-house standards which are primarily based on the publishedcodes, such as BS5500[18][18], with added extras which cover either technical or contractualmatters. In the safety report the base document for the in house codes should be clearly statedand the key safety related deviations or enhancements demonstrated so that the assessor candetermine their adequacy.

A Safety Report should demonstrate that consideration has been given to the appropriatestandards and codes of practice developed by legislators, regulators, professional institutionsand trade associations. It should also demonstrate that for any equipment that is installed, theoperating procedures, testing regimes and maintenance strategies that are in place meet orexceed these requirements in terms of safety performance.

Inherently Safer designThe principles of inherently safer design are particularly important for major hazard plants andshould be considered during the design stage. The Safety Report should adequatelydemonstrate that consideration has been given to the concepts. Some companies now havedesign procedures that require a review of designs and seek to ensure that inherently saferconcepts have been addressed.

Inherently safe design should be considered during the design stage in an effort to reduce thehazard potential of the plant. Protective equipment installed onto standard equipment to controlaccidents and protect people from their consequences is often complex, expensive and requiresregular testing and maintenance. Attempts should be made to reduce the requirement for suchprotective equipment by designing simpler and safer processes in the first instance. A number ofapproaches can be considered but basically an inherently safer plant can be achieved byminimising the inventories of hazardous substances in storage and in process and hence therisk of a major accident can be significantly reduced.

Some of the techniques that can be considered are:

Intensification - this technique involves reducing the inventory of hazardous materials to alevel whereby it poses a reduced hazard. This often means carrying out the reaction orunit operation in a smaller volume. It can be applied to a wide range of unit operationsincluding reactors, distillation and heat exchange but it may involve different mechanismsand approaches having to be employed to the reaction chemistry and control systems;Substitution - this technique involves replacing a hazardous material (or feature) with asafer one. For example, flammable solvents, refrigerants and heat transfer media canoften be replaced by non-flammable or less flammable (high boiling) materials. Oftenhazardous processes can also be replaced by inherently safer processes that do notinvolve the use of hazardous substances or which operate at lower temperatures andpressures;Attenuation - using a hazardous material under less hazardous conditions. For example,quantities of chlorine, ammonia and LPG can be stored as refrigerated liquids underatmospheric pressure rather than under pressure at ambient temperature. Materials likelyto form explosive dusts can be used and stored as slurries to minimise hazards;Limitation - affected by equipment design or changes to reaction conditions rather than byadding on protective equipment. For example, the selection of some types of gaskets canreduce leak rates from equipment in the event of a leak hence limiting the hazard. Manyrunaway reactions can be prevented, either by changing the order of addition, reducingthe temperature or changing other parameters;Simplification - simpler plants are friendlier and safer than complex plants and thereforeless likely to have a major accident caused by operator error;Knock-on effects - plants should be designed to reduce the likelihood of incidentsproducing knock-on effects or domino effects in other areas;Avoid incorrect assembly - for critical equipment plants can be designed so that incorrectassembly is difficult or impossible. Consideration should be given to installing differenttypes of connections on inlet/outlet pipework to avoid the possibility of wrong connectionsbeing made.

Further guidance on inherently safer design can be found in `Cheaper, Safer Plants' - Kletz,T.A., 1984, IChemE, ISBN 0 8529 5167 1.

Design AssessmentsA design should be subject to a number of detailed assessments throughout its development.Evidence that some system of assessment has taken place should be provided in the SafetyReport. A number of different features can be examined and assessed. Examples are givenbelow:

Value engineering assessment;Energy efficiency assessment;Reliability and availability assessment;Hazard identification and assessment;Occupational health assessment;Environmental assessment.

These assessments all have a specific individual focus but in the context of COMAH it needs tobe demonstrated that major accident hazards are not introduced as a result of the assessmentsthat are undertaken. For example any decisions taken as a result of a value engineeringassessment that result in standby equipment not be installed, or equipment of a lesserspecification being chosen should also demonstrate that the major accident hazard implicationsof such decisions have also been considered.

A number of companies have developed detailed procedures for design studies that incorporatemany of these assessments into a formalised structure.

Evidence that Hazard identification and/or HAZOP studies have been carried out should beprovided as evidence that a design has been evaluated and carefully considered before beinginstalled on the plant. See Technical Measures Document - Plant Modification / ChangeProcedures[19][19].

General considerations[20][20]

There are several general topics that are common to the detailed mechanical design of manytypes of equipment and these are discussed in greater detail below:

Temperature and Pressure;Materials of Construction;Corrosion/Erosion.

A number of potential hazards can be introduced if these are not given adequate consideration.Loss of containment may occur due to leaks, equipment failure, fire or explosion and result in amajor accident.

Temperature and pressureTemperature and pressure are two basic design parameters. Any equipment that is to beinstalled should be designed to withstand the foreseeable temperature and pressure over thewhole life of the plant. The combination of temperature and pressure should be consideredsince this affects the mechanical integrity of any equipment that is installed.

TemperatureIn determining design temperatures a number of factors should be considered including:

the temperature of the fluids to be handled;Joule-Thomson effect (The Joule-Thomson effect is the change in temperature thataccompanies expansion of a gas without production of work or transfer of heat. Atordinary temperatures and pressures, all real gases except hydrogen and helium coolupon expansion and this phenomenon is often utilised in liquefying gases);ambient temperatures;solar radiation; andheating and cooling medium temperatures.

Consideration needs to be given to the temperature of the fluids that are to be handled and anyexcursions in temperature that could occur as a result of the failure of temperature controlsystems. Account should be taken of foreseeable reactions that may occur that are likely toincrease or reduce the heat input to the system.

The extremes of ambient temperature should be taken into account for plant situated outsidebuildings. Solar radiation on the exposed surface area of large storage tanks can significantlyincrease surface temperatures for storage vessels leading to significant thermal expansion ofvessel contents. Likewise the low temperatures that can be achieved under conditions of snow,ice and wind, which can cause solidification of contents in vessels and pipelines, should also beconsidered. External facilities should be designed to accommodate the cycling of temperaturesbetween extreme weather conditions.

If secondary heating and cooling systems are employed then the maximum and minimumtemperatures that can be achieved by these secondary systems should be assessed assumingfailure of any control systems associated with these systems. Care should be taken to ensurethat the maximum temperature that can be achieved by heating oil systems or the minimumtemperature that can be achieved by cryogenic cooling systems does not compromise thedesign of the equipment. It should not adversely affect the mechanical strength and henceintegrity, or result in additional process hazards as a result of overheating, decomposition orrunaway reactions.

The strength of materials decreases with increasing temperature and therefore the maximumdesign temperature should take into account the strength of material used for fabrication.

Evidence should be provided in the safety report that the process conditions and environment inwhich the equipment is to be utilised have been assessed and that an appropriate designtemperature has been selected.

PressureA vessel should be designed to withstand the maximum pressure to which it is likely to besubjected in operation.

For vessels under internal pressure the design pressure is usually taken at that which the reliefvalve is set. This is normally 5-10% above the normal working pressure to avoid inadvertentoperation during minor process upsets. Vessels subjected to external pressure should bedesigned to resist the maximum differential pressure that is likely to occur. Vessels likely to besubjected to vacuum should be designed for full negative pressure of 1 bar unless fitted with aneffective and reliable vacuum breaker device.

Account should also be taken of foreseeable reactions which may occur that are likely toincrease the heat input to a system, or gas evolution and hence result in increased ordecreased temperatures and pressures. Where strongly exothermic reactions or runawayreactions are possible it may not be possible to adequately design the equipment to withstandthe maximum predicted temperature and pressure. Under such circumstances some form ofpressure relief system may be appropriate in order to protect the equipment and preventcatastrophic failure of the equipment from occurring. See Technical Measures Document -Reaction / Product Testing[21][21].

Pressure vessels should be fitted with some form of pressure relief device set at the designpressure of the equipment to relieve over-pressure in a controlled manner - see TechnicalMeasures Documents - Relief Systems / Vent Systems[22][22], and Explosion Relief[23][23].The set pressure of a relief valve should be such that the valve opens when the pressure risethreatens the integrity of the vessel but not when normal minor operating pressure deviationsoccur. It is necessary to balance a number of factors in the selection of relief valve setpressures since if the potential cause of pressure rise is runaway reaction then setting the reliefpressure at a high level above the normal operating pressure may allow the reaction to reach ahigher temperature and to proceed more rapidly before venting starts.

During the operation of the relief valve the pressure at the inlet to the relief valve (theoverpressure - this is usually taken to be no more than 10% for design purposes) can beexpected to increase above the set point for the relief device. The accumulation in the vessel isthe permitted increase in the system pressure above the design pressure in an emergencyoverpressure situation. The maximum allowable accumulated pressure (MAAP) is specifiedwithin the various codes and this should be taken into account when the relief valve set point isselected. Normally the relief valve set point is set below or up to the maximum design pressurewhich allowing for the overpressure during a relief event ensures that the overall pressure isbelow the MAPP. Specific guidance on the recommendations for pressure relief protectivedevices is given in Appendix J of BS 5500 : 1997[24][24]. Other codes permit higher MAAPs in

certain circumstances.

Discharge of hazardous substances from relief systems under emergency conditions should berouted to secondary containment vessels or to safe locations so that additional hazards topersonnel or equipment and the possible escalation of an incident does not occur. This shouldbe considered as part of the mechanical design of the equipment if such systems are to beemployed.

Evidence should be provided in the safety report that the process conditions and environment inwhich the equipment is to be utilised have been assessed and that an appropriate designpressure has been selected.

Evidence should be provided in the Safety Report that the relief systems have been suitablydesigned and consideration has been given to the discharge locations. Secondary containmentfacilities may be appropriate for discharge of relief streams. Documentation for relief streamsshould be available for inspection.

Consideration should be given to the possibility of pressure cycling in equipment andsubsequent failure of the equipment due to metal fatigue

Materials of constructionAnother important consideration in mechanical design is the selection of the material ofconstruction.

In some cases the available materials of construction may constrain the design temperaturesand pressures that can be achieved and limit the design of the equipment.

The most important characteristics that should be considered when selecting a material ofconstruction are summarised below:

Mechanical Properties;

Tensile strength;Stiffness;Toughness;Hardness;Fatigue resistance;Creep resistance;

The effect of low and high temperatures on the mechanical properties;Corrosion resistance;Ease of fabrication;Special properties - electrical resistance, magnetic properties, thermal conductivity;Availability in standard sizes;Cost.

The selection of a suitable material of construction is often carried out by disciplines such asprocess engineers. The advice of specialist materials engineers should be sought in the eventof difficult applications being identified.

The Safety report should contain evidence that the materials of construction that have beenselected are compatible with the process fluids to be handled and the design conditions thathave been chosen.

Corrosion/erosionIf materials to be used in the process are corrosive then this should be taken into account in theplant design and layout. Materials of construction should be carefully selected, protected wherepossible and regularly inspected if the presence of corrosive materials or a corrosiveenvironment is anticipated.

The layout of plant and equipment for corrosive materials is discussed in `Safety andManagement - A Guide for the Chemical Industry' - the Association of British ChemicalManufacturers, 1964. Printed by W.Heffer & Sons.

This topic is covered fully in the Technical Measures Document - Corrosion / Selection ofMaterials[25][25]. See also Causes of Plant Failure[26][26].

General guidance on corrosion allowances for pressure vessels is given in BS 5500[27][27].The standard recommends that all possible forms of corrosion such as chemical attack, rusting,erosion and high temperature oxidation are reviewed, that particular attention be paid toimpurities and to fluid velocities, and that where doubt exists corrosion tests should be carriedout.

The life of equipment subjected to corrosive environments can be increased by properconsideration of design details. Equipment should be allowed to drain freely and completely andthe internal surfaces should be smooth and free from locations where corrosion products canaccumulate. Fluid velocities should be high enough to prevent deposition but not so high as tocause erosion.

The corrosion allowance is the additional thickness of metal added to allow for material lost bycorrosion and erosion or scaling. For carbon and low-alloy steels where severe corrosion is notexpected a minimum allowance of 2 mm is often used, where more severe corrosion isanticipated an allowance of 4 mm is often used. Most design codes and standards specify aminimum allowance of 1 mm.

A large proportion of failures in process plant and vessels are due to corrosion. It is often theprime cause of deterioration and may occur on any part of a vessel. The severity of thedeterioration is strongly influenced by the concentration, temperature, and nature of thecorrosive agents in the fluids and the corrosion resistance of the construction materials.Corrosion may be of a general nature with fairly uniform deterioration, or may be very localisedwith severe local attack. Erosion is often localised especially at areas of high velocity or impact..Occasionally corrosion and erosion combine to increase rates of deterioration.

Erosion is a particular problem for solids handling in pipework, ducts and dryers. It occursprimarily at sites where there is a flow restriction or change in direction including valves, elbows,tees and baffles. Erosion is promoted by the presence of solid particles, by drops in vapours,bubbles in liquids or two-phase flow. Conditions that can cause severe erosion includepneumatic conveying, wet steam flow, flashing flow and pump cavitation. If erosion is likely tooccur then more resistant materials should be specified or the material surface protected insome way. For example plastic inserts can be used to protect erosion-corrosion at the inlet toheat exchanger tubes.

See also BS 5493: 1977 - Code of Practice for protective coating of iron and steel structuresagainst corrosion.

Specific equipment - Mechanical design[28][28]

Design issues, codes and standards applicable to several general categories of equipment havebeen identified and are discussed below in further detail:

Pressure Vessels;Other Vessels (including Storage Tanks);Reactor Design;Heat Exchange Equipment;Furnaces and Boilers;Rotating Equipment.

Pressure vessels

IntroductionThere are numerous texts available on the details of pressure vessel design however the basisof the design of pressure vessels is the use of appropriate formulae for vessel dimensions inconjunction with suitable values of design strength.

Pressure vessels can be divided into `simple vessels' and those that have more complexfeatures. The relevant standards and codes provide comprehensive information about thedesign and manufacture of vessels and vessel design and fabrication is an area well covered bystandards and codes. In general terms outright failure of a properly designed, constructed,operated and maintained pressure vessel is rare.

Design and manufacture is normally carried out to meet the requirements of national andinternational standards with one of the earliest being the AOTC 1939/48/58 `Rules for theconstruction, testing and scantlings of metal arc welded steel boilers and other pressurevessels'. The other principal standards in the UK were BS 1500[29][29] and BS 1515[30][30],both of which are now withdrawn and superseded by BS 5500[31][31]. The other mostcommonly used design code is ASME VIII. However it is unusual, though not unknown, forcompanies and operators to employ their own design codes.

Generally pressure vessel design codes covers equipment such as reactors, distillationcolumns, storage drums, heaters, reboilers, vaporisers, condensers, heat exchangers, bullets,spheres etc. Basically any equipment with a "shell" that may experience some internal pressureis covered. This section does not cover piping systems (see separate Technical MeasuresDocument on Design Codes Pipework[32][32]), atmospheric storage tanks and rotary machines.These are considered in further detail later.

Simple vesselsA simple pressure vessel does not have any complicated supports or sections and the ends aredished. The main code for simple vessels is BS EN 286-1:1991. `Simple unfired pressurevessels designed to contain air or nitrogen'. All aspects of designing and manufacturing thevessel are covered in this code.

Complex vessels

Traditionally the two principal codes and standards BS 5500[33][33] and ASME VIII, areemployed in the design and manufacture of pressure vessels within the United Kingdom.Importantly both of these demand adherence to satisfaction in the design and manufacturingprocess of an independent inspection authority. This authority is responsible for adherenceduring both the design and construction phases in accordance with the standard or code.

Design considerations

Factors that should be taken into account in the design process for pressure vessels include:

Internal and external static and dynamic pressures;Ambient and operational temperatures;Weight of vessel and contents;Wind loading;Residual stress, localised stress, thermal stress etc.;Stress concentrations;Reaction forces and moments from attachments, piping etc;Fatigue;Corrosion/erosion;Creep;Buckling.

Pressure vessels are subject to a variety of loads and other conditions that cause stress andcan result in failure and there are a number of design features associated with pressure vesselsthat need to be carefully considered.

Discontinuities such as vessel ends, changes of cross-section and changes of thickness;Joints (bolted and welded);Bimetallic joints;Holes and openings;Flanges;Nozzles and connections;Bolt seating and tightening;Supports and lugs.

Consideration should also be given to other parts of the vessel not directly within the pressureenvelope, but critical to vessel integrity i.e. any failure which could lead to breach of thepressure boundary e.g. vessel skirt or support legs. Other factors which require carefulconsideration include; a means of in-service periodic examination i.e. a means of determiningthe internal condition of the vessel by the provision of access openings; a means of draining andventing the vessel; and means by which the vessel can be safely filled and discharged.

Materials of construction

VesselsMaterials used for the manufacture of pressure vessels should have appropriateproperties for all operating conditions that are reasonably foreseeable, and for all testconditions. They should be sufficiently chemically resistant to the fluid contained and notbe significantly affected by ageing. The materials should be selected in order to avoidcorrosion effects when the various materials are put together.

Steel is the most common material of construction, including mild steel, low alloy steel,and stainless steel. It is often operating process temperature that determines the materialused, but other equally important factors such as corrosion/erosion allowance, lowtemperature application etc. can determine selection.

Clearly in the choice of material selection it is important that the material selected not onlyhas properties which are suited to that particular application, but also that its suitabilitywith regard to fabrication is also taken into account. Several different methods are used to

construct pressure vessels, most however are constructed using welded joints.

Where an American, British or European code is used for vessel design and specificmaterials are quoted within the code it is important that the correct materials are used inorder that the design is not invalidated.LinersWhere carbon steel will not resist expected corrosion or erosion or could causecontamination of the product, vessels may be lined with other metals or non-metals. Alined vessel is usually more economical than one built of solid corrosion resistant material.Metallic liners are installed in various ways. They may be an integral part of the platematerial rolled or bonded before fabrication of the vessel, or they may be separate sheetsof metal fastened by welding. Metallic liners may be made of ferritic alloy, monel alloy,nickel, lead or any other metal resistant to the corrosive agent. Non-metallic liners may beused to resist corrosion and erosion or to insulate and reduce the temperature on thewalls of a pressure vessel. The most common materials are reinforced concrete,insulating material, carbon brick, rubber, glass and plastic.InternalsMany pressure vessels have no internals. Others have internals such as baffles, trays,mesh or strip type packing, grids, bed supports, cyclones, pipe coils, spray nozzles,quench lines, agitators etc. Large vessels may have internal bracing and ties and mostvacuum vessels have either internal or external stiffening rings. Heat exchangers haveinternal tube bundles with baffle and support plates. These internals may be made from awide range of materials but care should be taken that the materials selected for theinternals are compatible with the materials chosen for fabrication of the main components.

Failure modesPressure vessels are subject to a variety of loads and other conditions that cause stress and incertain cases may cause serious failure. Any design should take into account the most likelyfailure modes and causes of deterioration. Deterioration is possible on all vessel surfaces incontact with any range of organic or inorganic compounds, with contaminants, or fresh water,with steam or with the atmosphere. The form of deterioration may be electrochemical, chemical,mechanical or combinations of all.

Mechanical Failure

The most common causes of mechanical failure in process plant are:

Faulty materials;Faulty fabrication and assembly;Excessive stress;External loading including reaction forces;Overpressure;Overheating;Mechanical and thermal fatigue;Mechanical shock;Brittle failure;Creep;Corrosion failure.

Corrosion Failure

The most common corrosion mechanisms are:

General corrosion;Crevice corrosion;Corrosion pitting;External corrosion including corrosion beneath lagging;Stress corrosion cracking;Corrosion fatigue.

For more information see Technical Measures Document - Corrosion / Selection ofMaterials[34][34].

Design Codes and StandardsTwo principal codes and standards are employed in the design and manufacture of pressurevessels - the American ASME VIII system and BS 5500[35][35] in the UK. Importantly both ofthese demand adherence to satisfaction in the design and manufacturing process of anindependent inspection authority. This authority is responsible for adherence during both thedesign and construction phases in accordance with the standard code. The codes andstandards cover design, materials of construction, fabrication (manufacture and workmanship),inspection and testing, and form the basis of agreement between the manufacturer andcustomer and the appointed independent inspection authority. These codes relate to vesselsfabricated in carbon and alloy steels and aluminium.

Computer programmes to aid the design of vessels to BS 5500[36][36] and the ASME VIIIcodes are commercially available.

Non-metallic materials of constructionAlthough the majority of pressure vessels are constructed from metallic compounds pressurevessels can also be constructed from materials such as glass reinforced plastic (GRP), or fibrereinforced plastic (FRP). The main relevant standard is BS 4994:1987 - Specification for Designand Construction of Vessels and Tanks in Reinforced Plastics.

Other Vessels (including storage tanks)Some vessels that are used are not designated as pressure vessels. The descriptionatmospheric storage is applied to any tank that is designed to be used within a limited range ofatmospheric pressure, either open to the atmosphere or enclosed.

Vertical storage tanks with flat bases and conical roofs are often used for the storage of liquidsat atmospheric pressure and may vary in size considerably. The main load to be considered inthe design of such tanks is the hydrostatic pressure of the liquid contained within the tank.However consideration should also be given to other parameters and the wind loading and anylikely snow loading should also be considered.

The design of atmospheric storage tanks in general is governed by API Std 620 Design andconstruction of large, welded, low-pressure storage tanks and API Std 650 Welded steel tanksfor oil storage.

Tanks should be suitable for their operational duty and all reasonably expected forces such astank contents, ground settlement, frost, wind and snow loadings, earthquake and others asappropriate. The selection of the type of tank to be used for a particular duty will be influencedby considerations of safety, technical suitability and economy. The safety considerations are

usually related to fire hazards which in turn are dependent on the physical properties of thestored material e.g. flash point, vapour pressure, electrical conductivity etc.

API Standard 2000 gives guidance on the design of vents to prevent pressure changes thatwould otherwise occur as a result of temperature changes or the transfer in and out of liquids.Excessive loss of vapours from vent systems may result from outbreathing and may present ahazard.

Reactor designReactors are often the centre of most processes and their design is of utmost importance whenconsidering the safety hazards of a plant. Reactors are most often considered as pressurevessels and the mechanical design should be in accordance with the codes and standardsdescribed earlier.

Reactor design should minimise the possibility of a hazardous situation developing and providethe means for dealing with a hazardous situation should it develop. Arrangements for venting,pressure relief and blowdown need to be adequately addressed in the design. For relief systemsconsideration should be given to the implications of the release of reactor contents andcontainment and control systems may be necessary to prevent a hazardous situation fromdeveloping as a result of the discharge of a relief system.

The design of the reactor may affect the efficiency of the reaction process and hence thegeneration of by-products and impurities. The effectiveness of the reaction step will oftendetermine the requirement for and complexity of downstream separation processes. In addition,low conversions may result in large recycles being required.

Many different types of reactor system are available and some of the important criteria toconsider are given below:

Addition of reactants - the order and rate of addition of the reactants may affect the rate ofreaction and the generation of by-products. The generation of unstable by-products or excessivereaction rates may increase the potential for a hazardous situation to develop. The position ofaddition of reactants may also be important - sub-surface and directly into an intimate mixingzone within the reactor may result in the minimisation of the generation of reaction by-products;

Mixing - the agitation system selected for the reactor (if appropriate) may directlyinfluence the efficiency of the reaction and hence the generation of by-products.Consideration should also be given to the consequences of agitation failure in the designof the reaction system. Methods for detecting the failure of a mixing/agitation systemand/or stopping the flow of reactants into the reactor may be appropriate especially if thereis the possibility of two phases forming on agitation failure which may reactexothermically/vigorously when agitation is recommenced. See Technical MeasuresDocuments - Reaction / Product Testing[37][37] and Control Systems[38][38];Heat removal - for exothermic reactions the control of the reaction system and the heatremoval systems should be carefully considered. Consideration should be given to themodes of failure of the control and cooling systems to ensure that the hazards of arunaway exothermic reaction are minimised;Phase - the reaction may take place in the gas, liquid or sometimes solid phase. The wayin which the reactants are brought into contact may influence the efficiency of the reactionand introduce additional hazards into the reaction system;Catalysts - a reaction may require a catalyst in order to promote the required reaction.However the catalyst may present additional hazards and consideration should be givento the selection of the catalyst system in order to minimise the risks associated. If acatalyst is required then additional separation steps to remove the catalyst maysubsequently be required.

The safety report should describe how the reactor system has been designed with the principlesof safe design in mind and how the selection of the mixing, chemical addition systems and reliefsystems have been selected in order to minimise the potential for a major accident.

Heat exchangers/reboilersThe transfer of heat between two process streams is a common activity and requirement on achemical plant. A number of direct or indirect techniques can be employed. The most commonform of equipment used to transfer heat is a heat exchanger which can be designed in manydifferent shapes, sizes and configurations necessary to obtain the required heat transferbetween one stream and another. A number of different heat transfer operations are possiblewith some involving a change of phase of one or more component. Heating, cooling,evaporation or condensation may all need to be considered and the equipment designedaccordingly to account for the differing requirements.

The basic design is commenced by an approximate sizing of the unit based on assumptionsmade concerning the heat transfer characteristics of the substances involved and theanticipated materials of construction. More detailed calculations are then required to confirm andrefine the original design and to identify an optimum layout. Once the process design has beencompleted the mechanical design of the unit can then be carried out.

The design of heat exchangers is covered in many texts. A common reference for designengineers however is `Process Heat Transfer - D.Q.Kern, International Student Edition, McGrawHill, ISBN 0070341907.

The mechanical design features, fabrication, materials of construction and testing of shell andtube heat exchangers is covered by `BS 3274: 1960- Tubular Heat Exchangers for GeneralPurposes'.

The standards of the American Tubular Heat Exchanger Manufacturers Association (TEMAstandards) are also widely used. Many companies also have their own standards to supplementthese various requirements.

The TEMA standards give the preferred shell and tube dimensions, the design andmanufacturing tolerances, corrosion allowances and the recommended design stresses formaterials of construction.

Design temperatures and pressures for exchangers are usually specified with a margin of safetybeyond the conditions normally anticipated. Typically the design pressure may be 170 kPagreater than the maximum anticipated during operation or at pump shutoff, and the temperatureis commonly 14°C greater than the maximum anticipated service temperature.

Major problems associated with heat exchanger design that may affect safety include fouling,polymerization, solidification, overheating, leakage, tube vibration and tube rupture. The shell ofan exchanger is normally a pressure vessel and should be designed in accordance with therelevant pressure vessel design code - BS 5500[39][39] or ASME VIII (Rules for construction ofpressure vessels, Division 1). More specific guidance is given in API RP 520:1990.

Special consideration needs to be given to the preventing overheating within heat exchangerequipment especially if sensitive materials are involved, for example materials which mayundergo exothermic decomposition.

The safety report should demonstrate that heat exchange equipment has been designed andmaintained in accordance with the relevant codes and standards and that consideration hasbeen given to the various failure modes that could occur and the implications of such events. Itshould be demonstrated that wherever possible measures have been taken to prevent, controlor mitigate the consequences of such events by the appropriate selection of materials of

construction, fabrication methods, instrumentation and control or others.

Furnaces/boilersFurnaces and boilers are items of equipment that are often found as part of process plant andare used for a variety of purposes such as waste heat recovery, steam generation, destructionof off-gases etc.

The design may involve the interaction of many different variables including water/steamcirculation systems, fuel characteristics (liquid, gaseous or solid fuels), ignition control systems,heat input and heat transfer systems.

The design of the furnace or boiler enclosure should be able to withstand the thermal conditionsassociated with the system and specialist designs are often required. Many codes andstandards exist for boiler design.

The elimination of hazards in burner design is a fundamental design requirement. Explosionscan occur during start up if ignition design is not carefully considered. Leaks of fuel can causeexplosive atmospheres when ignition is attempted. For these reasons consideration should begiven to inerting /ventilation systems prior to ignition sequences to ensure explosiveatmospheres are not present.

Isolation systems should be adequately designed to ensure leakage of fuel does not occur.Double block and bleed valves on fuel lines can be considered. Reliance should never beplaced upon single valves for isolation. Careful consideration of the configuration of thepipework should also be considered to ensure that the flow of fuel into the system after theflame has failed or valves have been closed is minimised.

Purging facilities are essential to ensure that the firing space is free from a flammableatmosphere prior to start-up ignition.

A safety report should demonstrate that any furnace/boiler system is designed and maintainedto the relevant codes and standards and that consideration has been given to the major hazardsassociated with the start-up, shutdown and operation of the equipment in terms of the fire andexplosion potential of such systems. It should be demonstrated that the risks of an explosionoccurring have been minimised by the design of the burner control management system and thelayout and design of the fuel supply systems.

Rotating equipmentProcess machines are particularly important items of equipment in process plants and in relationto pressure systems since they are required to provide the motive force necessary to transferprocess fluids (liquids, solids and gases) from one area of operation to another. A machinesystem is any reciprocating or rotating device that is used to transfer or to produce a change inproperties within a process plant. Examples may include items such as pumps, fans,compressors, turbines, centrifuges, agitators etc.

This type of equipment is a potential source of loss of containment. In addition due to therotating/vibrating nature of such equipment pressure and flow fluctuations may be caused andthese can affect the operation of other systems.

The basic requirements to define the application for pumps, fans and compressors are usuallythe suction and delivery pressures, the flow rate required and the pressure loss in transmission.Special requirements for certain industrial sectors may also impose restrictions on the materialsof construction to be used or the type of device that can be considered. Many designs havebecome standardised based on experience and numerous standards (API standards, ASMEstandards, ANSI standards) have become available. These standards often specify design,construction and testing details such as material selection, shop inspection and tests, drawings,

clearances, construction procedures etc

The choice of material of construction is dictated by consideration of corrosion, erosion,personnel safety and containment and contamination.

PumpsMany pumps are of the centrifugal type, although positive displacement types (such asreciprocating and screw types) are also used. Pumps are available throughout a vast range ofsizes and capacities and are also available in a wide range of materials including various metalsand plastics. Sealing of pumps is a very important consideration and is discussed later. Theprimary advantage of a centrifugal pump is its simplicity. Pumps are particularly vulnerable tomal-operation and poor installation practices. Proper installation and high quality maintenance isessential for safe operation.

Problems associated with centrifugal pumps can include bearing and seal failure. Cavitation (thecollapse of vapour bubbles in a flowing liquid leading to vibration, noise and erosion) and deadhead running (attempting to run a pump without an outlet for the fluid, for example against aclosed valve) can also result in damage to the pumping equipment. Misalignment between pumpand motor is also a common cause of catastrophic failure.

Seal-less or `canned pumps' are often used where any leakage is considered unacceptable. Ina canned pump the impeller of the pump and the rotor of the motor are mounted on an integralshaft which is encased so that the process fluid can circulate in the space which is normally theair gap of the motor.

Key parameters for pump selection are the liquid to be handled, the total dynamic head, thesuction and discharge heads, temperature, viscosity, vapour pressure, specific gravity, liquidcorrosion characteristics, the presence of solids which may cause erosion etc.

CompressorsBoth positive displacement and centrifugal compressors are used in the process industry. Theyare complex machines and their reliability is crucial. It is very important that they are maintainedto high operational standards. Centrifugal compressors are by far the most common althoughcompression is generally lower than that given by reciprocating machines. They are used inboth process gas and refrigeration duties. On centrifugal compressors some of the principalmalfunctions include rotor or shaft failure, bearing failure, vibration and surge. Reciprocatingcompressors are utilised for higher compression requirements. They may be either single ormulti-stage units. Air compressors for dry air require special consideration and specific codesand standards exist.

FansThe main applications for fans are for high flow, low pressure applications such as supplying airfor drying, conveying material suspended in a gas stream, removing fumes, or in condensingtowers. These units can be either centrifugal or axial flow type. They are simple machines butproper installation and maintenance is required to ensure high reliability and safe operation.

VibrationOne of the main causes of failure of rotating equipment is vibration. This often causes sealdamage or fatigue failure and subsequent leakage and can result in a major accident.Numerous factors can result in vibration occurring including cavitation, impeller imbalance, loosebearings and pulses in the pipe. ASME standards recommend that pumps should be periodicallymonitored to detect vibration that should normally fall within prescribed limits as determined bythe manufacturer. This should be initially confirmed on installation and then periodically

checked. If measured levels exceed prescribed values then preventative maintenance isrequired and should be performed. By collection and analysis of vibration signatures of rotatingequipment it is possible to identify which components of the system are responsible forparticular frequencies of the vibration signal. It is then possible to identify the component that isdeteriorating and responsible for the vibration that is occurring.

SealsSeals are very important and often critical components in large rotating machinery and insystems which are flanged/jointed such as heat exchangers or pipework systems. Failure of asealing arrangement can lead to loss of containment and a potential for a major accident.Numerous different types of sealing arrangement exist for rotating equipment. There are manyfactors that govern the selection of seals for a particular application including the product beinghandled, the environment which the seal is installed in, the arrangement of the seal, theequipment the seal is to be installed in, secondary packing requirements, seal facecombinations, seal gland plate arrangements, and main seal body etc. The materials used forseals should always be compatible with the process fluids being handled.

There are three principal methods of sealing the point at which a rotating shaft enters a pump,compressor, pressure vessel or similar equipment:

Conventional stuffing box with soft packing;Hydrodynamic seal, where rotating vanes keep the shaft free;Mechanical seals.

Stuffing boxes and glands with packing are commonly used. Some product leakage is normalboth lubricating and cooling the packing material. The chief advantages of this type of sealingarrangement are the simplicity and the ease of adjustment or replacement. The disadvantagesare the necessity of frequent attention and the inherent lack of integrity of such a system.

Mechanical seals are the next most commonly employed arrangement. They are used inapplications where a leak tight seal of almost any fluid is required. Mechanical seals find theirbest application where fluids should be contained under substantial pressure. They can rangefrom the simplest single seal arrangement to complicated sophisticated double seals withmonitoring of the interspace. Some mechanical seals are assemblies of great complexity andconsist of components manufactured to very high tolerances. They are often fitted as completecartridge type units. Some sealing arrangements require constant lubrication often from theprocess fluid itself whilst others require external lubrication arrangements.

Maintenance, inspection and monitoringPlant equipment may be monitored during commissioning and throughout its operational life.This monitoring may be carried out on the basis of performance or condition or both.Performance monitoring is not discussed in detail in this Technical Measures Document.However the predominant techniques and parameters employed are flow, pressure,temperature, power etc. The alternative to performance monitoring is condition monitoring ofwhich there are a number of techniques. The aim of such techniques is to identify deteriorationand pre-empt imminent failures and so secure reliable/available plant, particularly for productionand safety critical items. Some of these techniques are identified below:

Vibration monitoring;Shock pulse monitoring;Acoustic emission monitoring;Oil analysis.

Critical machinesAll machine systems should be assessed according to the hazard presented if the machine orany associated protective system should fail.

Machine systems that have been assessed to present unacceptable consequences if themachine or protective system should fail may be classified as a `Critical Machine System' andgiven specific attention during operation including additional maintenance and monitoring.

Assessments should be based on:

Potential consequences of any loss of containment);Potential consequences of the failure of the process;Potential damage caused by mechanical failure.

Structural design considerations[40][40]

Structures are required to provide support for plant and should be able to withstand allforeseeable loadings and operational extremes throughout the life of the plant. Failure of anystructural component could lead to initiation of a major accident. For full guidance on DesignCodes - Buildings / Structures[41][41] see relevant Technical Measures Document. Structuraldesign should take into account natural events such as wind loadings, snow loadings andseismic activity and also plant excursions

Maps showing the wind speeds to be used in the design of structures at locations in the UK aregiven in British Standards Code of Practice BS CP 3: 1972: Basic Data for the Design ofBuildings, Chapter V Loading: Part 2 Wind Loads. Typical values are around 50 m/s (112 milesper hour). The code of practice also gives methods estimating the dynamic wind pressure onbuildings and structures of various shapes.

LightningProtection against lightning strikes on process plant located outside buildings is required sincelightning is a potential ignition source especially for fires involving storage tanks. Lightningprotection should be provided and guidance is available in BS 6651 : 1992[42][42] Code ofPractice for Protection of Structures against Lightning.

See also Technical Measures Document - Earthing[43][43].

Special cases[44][44]

For the following substances general published codes exist giving full design details for storageand handling.

Chlorine storageThe design of systems for chlorine requires special consideration since chlorine is highly toxicand, if wet, also very corrosive.

Chlorine is usually stored under pressure at atmospheric temperature, but may also be storedfully refrigerated (-34°C) at atmospheric pressure.

A number of publications are dedicated to the handling of chlorine and specific guidance isgiven in:

HS(G)28 Safety advice for bulk chlorine installations[45][45], HSE, 1999.This guidance was originally published in 1986 and has been substantially revised.The HS(G)28 document has replaced earlier guidance from the CIA and the ChlorineInstitute which included:

Chlorine Manual, 1986, Pamphlet 1, Chlorine Institute.Non-refrigerated Liquid Chlorine Storage, 1982, Pamphlet 5, Chlorine Institute.Refrigerated Liquid Chlorine Storage, 1984, Pamphlet 78, Chlorine Institute.Code of Practice for Chemicals with Major Hazards: Chlorine, (the Chlorine Code), CIA,1975.Guidelines for Bulk Handling of Chlorine at Customer Installations (the CIA ChlorineStorage Guide), CIA, 1980/9.

Also see:

HS(G)40 Safe handling of chlorine from drums and cylinders[46][46], HSE.

CS16 Chlorine vaporisers[47][47], HSE.

The Euro Chlor organisation is an affiliate of the European Chemical Industry Council (CEFIC)and represents European chlorine producers at 85 plants in 19 countries. Euro Chlor produces anumber of publications. Further details can be obtained via the websitehttp://www.eurochlor.org[48][48].

ST 79/82, `Choice of materials of construction for use in contact with chlorine', Euro Chlor.This is a typical industry sector standard containing specific guidance on the use ofmaterials of construction for chlorine systems.

Ammonia storageAnhydrous ammonia, boiling point -33°C, is normally stored as a liquid either under pressure orat atmospheric pressure in refrigerated facilities.

A number of publications are dedicated to the handling of ammonia and specific guidance isgiven in:

HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical and cylindricalvessels[49][49], HSE, 1986 (Not in current HSE list).

Gives advice for the appropriate materials of construction for ammonia storage vessels.

CIA Refrigerated Ammonia Storage Code

CIA Code of Practice for the storage of anhydrous ammonia under pressure in the UK:Spherical and cylindrical vessels. (The CIA has withdrawn this document).

CIA Guidance for the large scale storage of fully refrigerated anhydrous ammonia in the UK.

CIA Guidance on transfer connections for the safe handling of anhydrous ammonia in the UK.

LPG storagePropane and Butane are referred to as liquefied petroleum gas (LPG) in accordance with BS4250: Specification for commercial butane and propane. Fully refrigerated storage is required atatmospheric pressure and at the boiling points of the substances concerned. LPG can also be

stored under pressure in horizontal cylindrical or spherical pressure vessels.

HS(G)34 Storage of LPG at fixed installations[50][50], HSE, 1987.

HS(G)15 Storage of liquefied petroleum gas at factories[51][51], HSE.

CS5 Storage of LPG at fixed installations[52][52], HSE.

LPGA CoP 1 Bulk LPG storage at fixed installations. Part 1 : Design, installation and operationof vessels located above ground, 2000.

LPGA CoP 1 Bulk LPG storage at fixed installations. Part 2: Small bulk propane installations fordomestic and similar purposes, 2000.

LPGA CoP 1 Bulk LPG storage at fixed installations. Part 3 : Periodic inspection and testing,2000.

LPGA CoP 1 Bulk LPG storage at fixed installations. Part 4 : Buried/mounded LPG storagevessels, 2000.

LPGA CoP 15 Valves and fittings for LPG service, Part 1 Safety valves, 2000.

LPGA CoP 17 Purging LPG vessels and systems, 2000.

EEMUA 147. Recommendations for the design and construction of refrigerated liquefied gasstorage tanks.

Liquefied petroleum gas. IP Model code of safe practice: Part 9.

Hydrocarbons storageA number of standards and codes exist for the storage of petroleum products and flammableliquids generally. A range of different main types of storage tanks and vessels for liquids andliquefied gases can be considered:

Atmospheric storage tanks:Low pressure storage tanks;Pressure or refrigerated pressure storage tanks;Refrigerated storage tanks.

The relevant standards and codes are:

API Std 620 Design and construction of large, welded, low-pressure storage tanks, AmericanPetroleum Institute, 1990.

API Std 650 Welded steel tanks for oil storage, American Petroleum Institute, 1988.

BS 2594 : 1975[53][53] Specification for carbon steel welded horizontal cylindrical storagetanks.

BS 2654 : 1989[54][54] Specification for manufacture of vertical steel welded non-refrigeratedstorage tanks with butt-welded shells for the petroleum industry.

BS 4741: 1971 Specification for vertical cylindrical welded steel storage tanks for lowtemperature service: single-wall tanks for temperatures down to -50°C.

BS 5387: 1976 Specification for vertical cylindrical welded steel storage tanks for lowtemperature service: double-wall tanks for temperatures down to -196°C.

BS 7777 : 1993[55][55] Flat-bottomed, vertical, cylindrical storage tanks for low temperatureservice.

This BS supersedes BS 4741:1971 and BS 5387: 1976 both of which are withdrawn.

BS 799: 1972 Oil Burning Equipment, Part 5 Specification for oil storage tanks.

NFPA 30: 1990 Flammable and Combustible Liquids Code.

IP MSCP Part 3, 1981 Refining Safety Code.

HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in totalcapacity)[56][56], HSE, 1990.

HS(G)51 Storage of flammable liquids in containers[57][57], HSE, 1998.

HS(G)52 The storage of flammable liquids in fixed tanks (exceeding 10000 cu. m in totalcapacity)[58][58], HSE, 1991.

HS(G)140 Safe use and handling of flammable liquids[59][59], HSE, 1996.

HS(G)176 The storage of flammable liquids in tanks[60][60], HSE, 1998.

CS2 The storage of highly flammable liquids[61][61], HSE, 1977.

IGE SR7 Bulk storage and handling of highly flammable liquids used within the gas industry,1989.

IGE SR14 High pressure gas storage: Part 1 - Above ground storage vessels

CS15 The cleaning and gas freeing of tanks containing flammable residues[62][62], HSE, 1997.

RC 20 Recommendations for the storage and use of flammable liquids, LPC, 1997.

EEMUA 147. Recommendations for the design and construction of refrigerated liquefied gasstorage tanks, 1986.

Construction of plant[63][63]

It is critically important that following the detailed design of a plant that the construction phase iscarried out according to the original specification and that no additional hazards are introducedto the plant during the construction phase. Poor construction can result in the integrity of thewhole system being compromised resulting in an increased risk of a major accident.

Building and construction are covered by a series of different building regulation including thefollowing:

Construction (General Provisions) Regulations, 1961;

Construction (Lifting Operations) Regulations, 1961;

Construction (Health and Welfare) Regulations, 1966;

Construction (Working Places) Regulations, 1966.

In addition the Construction (Design and Management) Regulations (CDM) clarify theresponsibilities of the various parties in a construction project. Also available is the ApprovedCode of Practice for the CDM Regs: Managing Construction for Health and Safety. Construction(Design and Management) Regulations 1994, ref L54, HSE Books 1995, ISBN 0 7176 0792 5.

Commissioning/verification of manufacture and construction standards[64][64]

It is important to demonstrate that the correct materials of construction have been used and thatappropriate construction techniques have been employed so as not to introduce constructionfaults and flaws into the plant. Evidence in the form of documentation which shows that checkswere carried out during the construction phase are important to prove that the constructionphase of the project has been adequately supervised.

Documentation should show that the equipment supplied and installed is of the correct materialof construction (and has received the correct heat treatment if appropriate), is the correctitem/part/unit number and is as specified in the design schedule.

Documentation should also show that the workmanship is of the quality specified and thatinspection and acceptance tests were carried out as required under the contract.

Commissioning of equipment should be carried out and records kept of the commissioningexercises.

Evidence of the following should be available:

Certificates of mechanical completion and hand over certificates;Mechanical completion checks - check that installed equipment is ready forcommissioning, is installed correctly and that the component parts operate as specifiedand that any ancillary equipment is installed and working;Certificates of acceptance of plant performance;Witnessing of performance tests;Witnessing of inspection and testing;Performance tests;Cleaning and pressure testing of systems;Visual inspection checks; Check that pipework and equipment is installed in accordancewith engineering drawings. Identify as built discrepancies;Check that mechanical equipment conforms to specified codes and standards, is installedin accordance with the relevant drawings and meets the performance tests specified;Each item of equipment should be checked for compliance with the specification. Thismay mean witnessing aspects such as examination or testing at the manufacturersworks;· Check any internal fittings are installed, are of the correct dimensions and arefirmly secured;Check on the materials of construction;Check rotating equipment for noise and vibration;Check plant against P&IDs and isometrics;Pressure vessel and system tests : inspection, pressure tests, leak tests, protectivedevices tests;Sub-system and system tests - dynamic safe fluid test (water test), dynamic process fluidtest;Test utilities, instruments, etc. Simulate faults for testing purposes.

The following documentation should be available:

Modification records;Equipment examination records - pressure vessels, pressure piping, protective devices;Equipment Test Records - pressure & leak tests, pressure relief valve tests, rotatingmachinery tests, instrument tests, computer system tests;Computer tests;Spares inventories;Safety review records;Environmental review records;Reservation lists.

The management of the commissioning and verification stages should be identified under theSafety Management System. The system should focus on ensuring that the design intent is met,and that deviations are properly assessed and controlled. Systems should be in place to ensurethat corrective action is taken on the identification of discrepancies between installed equipmentand the design intent and to control any deviations from normal operation.

Evidence of a number of pre-commissioning and commissioning checks should be presented toverify that the equipment as installed has been tested and is suitable for operation and meetsthe design intent. These may include:

Pre-commissioning Hazops;Check that information is installed as per the process flow diagrams and engineering linediagrams;Electrical installation checks;Mechanical installation checks - including rotation checks;Civil installation checks - bunds, drains, hardstanding etc;Safety system checks - relief devices installed etc;Instrumentation and control checks - verification of set points, alarm and trip testing etc:Inert material tests using water and air as appropriate;Commissioning tests using process materials.

Codes of Practice and guidanceThe following codes of practice may be useful reading for the assessor when considering theprocess design of plant and equipment. Codes and guidance associated with the design ofspecific items of equipment (as discussed in previous sections) are given below. Not all thecodes or guidance documents identified below are currently available and many have beensuperseded. However equipment designed to these original standards may still be in operation.

Pressure vessel design

ASME Boiler and pressure vessel code : 1998

BS 5500 : 1997[65][65] - Specification for Unfired Fusion Welded pressure Vessels

Other Standards and Codes of Practice relating to Pressure Vessel Design

In the UK pressure systems are covered by the Pressure Systems Safety Regulations 2000(PSSR regs)[66][66].

Other useful documents include:

ACOP: Safety of Pressure Systems. Pressure Systems Safety Regulations 2000[67][67]. RefL122. ISBN 0 7176 1767 X. Published by HSE Books 2000.

HS(G)93 The assessment of pressure vessels operating at low temperature[68][68], HSE, 1993.

BS 1500: 1958[69][69] - Fusion Welded Pressure Vessels for General Purposes.BS 5500[70][70] replaced this conventional code in the UK in 1976.

BS 1515: 1965[71][71] - Fusion Welded Pressure Vessels for Use in the Chemical, Petroleumand Allied Industries.BS 5500[72][72] replaced this advanced code in 1976.

BS EN 286-1:1991. Simple unfired pressure vessels designed to contain air or nitrogen.

API 510 Pressure vessel inspection code: Maintenance inspection, rating, repair, and alteration

API RP 572 Inspection of pressure vessels

API Standard 653 Tank inspection, repair, alteration and reconstruction.

API RP 520 Sizing, selection, and installation of pressure relieving devices in refineries

ASME B16.9 Factory made wrought steel butt welding fittings : 1978

ASME B16.11 Forged steel fittings socket-welded and threaded : 1980

BS 1501: 1970 - Steels for Pressure Purposes:Part 1 (1990) - Specification for carbon and carbon manganese steelsPart 2 (1988) - Specification for alloy steelsPart 3 (1990) - Specification for corrosion and heat resisting steels

BS 1502: 1990 - Specification for steels for fired and unfired pressure vessels: sections andbars

BS 1503: 1989 - Specification for steel forgings for pressure purposes

BS 1504: 1984 - Specification for steel castings for pressure purposes

BS 1506: 1990 - Specification for carbon, low alloy and stainless bars and billets for boltingmaterial to be used in pressure retaining applications.

BS 2594: 1975 - Specification for carbon steel welded horizontal cylindrical storage tanks.

BS 2654: 1989 - Specification for vertical steel welded non-refrigerated storage tanks with butt-welded shells for the petroleum industry

BS 2790: 1992 - Specification for design and manufacture of shell boilers of welded construction

BS 5276: 1977 - Pressure Vessel details (dimensions)

BS 5387: 1976 - Specification for vertical cylindrical welded steel storage tanks for lowtemperature service: double wall tanks for temperatures down to -196°C.

ISO R831: Recommendations for Stationary Boilers which is applicable to pressure vessels.

Pressure Vessels : Non-metallic materials of construction

BS 4994: 1987 - Specification for Design and Construction of Vessels and Tanks in ReinforcedPlastics.

BS 6374: 1984 - Lining of equipment with polymeric materials for the process industries.

ASME Boiler and Pressure Code Part X, Fiberglass Reinforced Plastic Pressure Vessels(1992).

ASTM D 4021-86 Standard Specification for Contact Moulded Glass-fiber-reinforcedThermosetting Resin Underground Petroleum Storage Tanks.

ASTM D 4097-88 Standard Specification for Contact Moulded Glass-fiber-reinforcedThermosetting Resin Chemical Resistant Tanks.

Pressure vessel systems examination. IP Model code of safe practice: Part 13

Other Vessels (including Storage Tanks)

API Std 620 Design and construction of large, welded, low-pressure storage tanks, AmericanPetroleum Institute, 1990.

API Std 650 Welded steel tanks for oil storage, American Petroleum Institute, 1988.

API Std 653 Tank inspection, repair, alteration, and reconstruction, American PetroleumInstitute, 1991.

API 12B - Bolted Production Tanks.

API 12D - Large Welded Production Tanks.

API 12F - Small Welded Production Tanks.

API Std 2000 Venting atmospheric and low pressure storage tanks: Nonrefrigerated andrefrigerated, American Petroleum Institute, 1998.

Heat Exchangers

BS 3274: 1960- Tubular Heat Exchangers for General Purposes.

American Tubular Heat Exchanger Manufacturers Association (TEMA standards).

The TEMA standards cover three classes of heat exchanger:

Class R - generally severe duties in the petroleum and related industries;Class C - moderate duties in commercial and general process applications;Class B - exchangers for use in the chemical process industries.

API Standard 660: 1987 - `Shell and Tube heat Exchangers for General Refinery Services'supplements both the TEMA standards and the ASME code.

API Standard 661: 1992 - Air Cooled Heat Exchangers for General Refinery Services.

Furnaces/boilersBS 1113: 1992 - Specification for design and manufacture of water-tube steam generating plant(including superheaters, reheaters and steel tube economisers).

BS: 799: 1981 - Oil Burning Equipment

BS 5410: 1976 - Code of Practice for Oil Firing

British Gas Code of Practice for Large Gas and Dual Fuel Burners (the BG Burner Code)

API Standard 560 - Fired heaters for general refinery services, 1986.

Rotating equipmentBS 7322: 1990 Specification for the Design and Construction of Reciprocating TypeCompressors for the Process Industry

API Standard 610: 1989 Centrifugal Pumps for General Refinery Services.

API Standard 611: 1988 General Purpose Steam Turbines for Refinery Services.

API Standard 612: 1987 Special Purpose Steam Turbines for Refinery Services.

API Standard 613: 1988 Special Purpose Gear Units for Refinery Services.

API Standard 614: 1992 Lubrication, shaft-sealing, and Control Oil systems for special purposeapplications.

API Standard 616: 1992 Gas Turbines for Refinery Services.

API Standard 617: 1988 Centrifugal Compressors for General Refinery Services.

API Standard 618: 1986 Reciprocating Compressors for General Refinery Services.

API Standard 619: 1985 Rotary Type Positive Displacement Compressors for General RefineryServices.

API Standard 674: 1987 Positive Displacement Pumps - Reciprocating.

API Standard 676: 1987 Positive Displacement Pumps - Rotary.

ASME 19.1 - 1990 Air Compressor Systems.

ASME 19.3 - 1991 Safety Standards for Compressors for the Process Industries.

ASME B73.1M - 1991 Specifications for Horizontal End Suction Centrifugal Pumps for ChemicalIndustries.

ASME B73.2M - 1991 Specifications for Vertical In-line Centrifugal Pumps for ChemicalIndustries.

BS 767: 1987 - Specification for centrifuges of the basket and bowl type for use in industrial andcommercial applications.

BS 4082: 1969 - Specification for external dimensions for vertical in-line centrifugal pumps.

BS 5257: 1975 - Specification for horizontal end suction centrifugal pumps (16 bar).

BS 7322: 1990 - Specification for the design and construction of reciprocating type compressorsfor the process Industry.

BS 4675: 1976 - Mechanical vibration in rotating machinery

Further reading material

Lees, F.P., Loss Prevention in the Process Industries[73][73]: Hazard Identification, Assessmentand Control', Volumes 1-3, Second Edition, 1996. Butterworth Heinemann. ISBN 0750615478.

Mecklenburgh, J.C., `Process Plant Layout', George Godwin/IChemE, London, 1985.ISBN 0711457549.

Perry, Robert H., Green Don W., `Perry's Chemical Engineer's Handbook', Seventh Edition,1997, McGraw-Hill. ISBN 0070498415.

Kern, D.Q., `Process Heat Transfer', International Student Edition, McGraw Hill,ISBN 0070341907.

Coulson J.M. and Richardson J.F., `Chemical Engineering Volumes 1-6'. Third Edition,Pergamon Press.

Case studies illustrating the Importance of Design Codes - Plant

Abbeystead Explosion (23/5/1984)[74][74]

Beek (7/11/1975)[75][75]

Bhopal - Union Carbide (3/12/1984)[76][76]

BP Oil West Glamorgan (17/1/1981)[77][77]

Explosion Caused by Explosion Suppression System[78][78]

Feyzin (4/1/1966)[79][79]

Polymerisation Runaway Reaction (May 1992)[80][80]

Seveso - Icmesa Chemical Company (9/7/1976)[81][81]

Link URLs in this page

1. 5.2.1.5(35)a,b, chttp://www.hse.gov.uk/comah/sram/index.htm

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9. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm10. Design Codes - Pipework

http://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm11. Explosion Relief

http://www.hse.gov.uk/comah/sragtech/techmeasexplosio.htm12. Relief Systems / Vent Systems

http://www.hse.gov.uk/comah/sragtech/techmeasventsyst.htm13. Training

http://www.hse.gov.uk/comah/sragtech/techmeastraining.htm14. Plant Modification / Change Procedures

http://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm15. Reaction / Product Testing

http://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm16. Training

http://www.hse.gov.uk/comah/sragtech/techmeastraining.htm17. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm18. BS5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm19. Plant Modification / Change Procedures

http://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm20. General considerations21. Reaction / Product Testing

http://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm22. Relief Systems / Vent Systems

http://www.hse.gov.uk/comah/sragtech/techmeasventsyst.htm23. Explosion Relief

http://www.hse.gov.uk/comah/sragtech/techmeasexplosio.htm24. BS 5500 : 1997

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm25. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm26. Causes of Plant Failure

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm27. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm28. Specific equipment - Mechanical design29. BS 1500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm30. BS 1515

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm31. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm32. Design Codes Pipework

http://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm33. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm34. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm

35. BS 5500http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

36. BS 5500http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

37. Reaction / Product Testinghttp://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm

38. Control Systemshttp://www.hse.gov.uk/comah/sragtech/techmeascontsyst.htm

39. BS 5500http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

40. Structural design considerations41. Design Codes - Buildings / Structures

http://www.hse.gov.uk/comah/sragtech/techmeasbuilding.htm42. BS 6651 : 1992

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm43. Earthing

http://www.hse.gov.uk/comah/sragtech/techmeasearthing.htm44. Special cases45. HS(G)28 Safety advice for bulk chlorine installations

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm46. HS(G)40 Safe handling of chlorine from drums and cylinders

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm47. CS16 Chlorine vaporisers

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm48. http://www.eurochlor.org

http://www.eurochlor.org/49. HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical and

cylindrical vesselshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

50. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

51. HS(G)15 Storage of liquefied petroleum gas at factorieshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

52. CS5 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

53. BS 2594 : 1975http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

54. BS 2654 : 1989http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

55. BS 7777 : 1993http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

56. 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

57. HS(G)51 Storage of flammable liquids in containershttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

58. 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

59. HS(G)140 Safe use and handling of flammable liquidshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

60. HS(G)176 The storage of flammable liquids in tankshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

61. CS2 The storage of highly flammable liquidshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

62. CS15 The cleaning and gas freeing of tanks containing flammable residueshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

63. Construction of plant64. Commissioning/verification of manufacture and construction standards65. BS 5500 : 1997

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm66. Pressure Systems Safety Regulations 2000 (PSSR regs)

http://www.opsi.gov.uk/si/si2000/20000128.htm67. ACOP: Safety of Pressure Systems. Pressure Systems Safety Regulations 2000

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm68. HS(G)93 The assessment of pressure vessels operating at low temperature

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm69. BS 1500: 1958

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm70. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm71. BS 1515: 1965

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm72. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm73. Loss Prevention in the Process Industries

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm74. Abbeystead Explosion (23/5/1984)

http://www.hse.gov.uk/comah/sragtech/caseabbeystead84.htm75. Beek (7/11/1975)

http://www.hse.gov.uk/comah/sragtech/casebeek75.htm76. Bhopal - Union Carbide (3/12/1984)

http://www.hse.gov.uk/comah/sragtech/caseuncarbide84.htm77. BP Oil West Glamorgan (17/1/1981)

http://www.hse.gov.uk/comah/sragtech/casebpglamorg81.htm78. Explosion Caused by Explosion Suppression System

http://www.hse.gov.uk/comah/sragtech/caseexplosion.htm79. Feyzin (4/1/1966)

http://www.hse.gov.uk/comah/sragtech/casefeyzin66.htm80. Polymerisation Runaway Reaction (May 1992)

http://www.hse.gov.uk/comah/sragtech/casepolymerisa92.htm81. Seveso - Icmesa Chemical Company (9/7/1976)

http://www.hse.gov.uk/comah/sragtech/caseseveso76.htm

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1. 5.2.1.5(35)a,b, chttp://www.hse.gov.uk/comah/sram/index.htm

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3. 5.2.1.6(38)e, f, ghttp://www.hse.gov.uk/comah/sram/index.htm

4. 5.2.1.7http://www.hse.gov.uk/comah/sram/index.htm

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8. 5.2.2.1http://www.hse.gov.uk/comah/sram/index.htm

9. Corrosion / Selection of Materialshttp://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm

10. Design Codes - Pipeworkhttp://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm

11. Explosion Reliefhttp://www.hse.gov.uk/comah/sragtech/techmeasexplosio.htm

12. Relief Systems / Vent Systemshttp://www.hse.gov.uk/comah/sragtech/techmeasventsyst.htm

13. Traininghttp://www.hse.gov.uk/comah/sragtech/techmeastraining.htm

14. Plant Modification / Change Procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm

15. Reaction / Product Testinghttp://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm

16. Traininghttp://www.hse.gov.uk/comah/sragtech/techmeastraining.htm

17. Corrosion / Selection of Materialshttp://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm

18. BS5500http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

19. Plant Modification / Change Procedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm

20. General considerations21. Reaction / Product Testing

http://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm22. Relief Systems / Vent Systems

http://www.hse.gov.uk/comah/sragtech/techmeasventsyst.htm23. Explosion Relief

http://www.hse.gov.uk/comah/sragtech/techmeasexplosio.htm24. BS 5500 : 1997

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm25. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm26. Causes of Plant Failure

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm

27. BS 5500http://www.hse.gov.uk/comah/sragtech/docsbsi.htm

28. Specific equipment - Mechanical design29. BS 1500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm30. BS 1515

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm31. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm32. Design Codes Pipework

http://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm33. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm34. Corrosion / Selection of Materials

http://www.hse.gov.uk/comah/sragtech/techmeasmaterial.htm35. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm36. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm37. Reaction / Product Testing

http://www.hse.gov.uk/comah/sragtech/techmeasreaction.htm38. Control Systems

http://www.hse.gov.uk/comah/sragtech/techmeascontsyst.htm39. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm40. Structural design considerations41. Design Codes - Buildings / Structures

http://www.hse.gov.uk/comah/sragtech/techmeasbuilding.htm42. BS 6651 : 1992

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm43. Earthing

http://www.hse.gov.uk/comah/sragtech/techmeasearthing.htm44. Special cases45. HS(G)28 Safety advice for bulk chlorine installations

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm46. HS(G)40 Safe handling of chlorine from drums and cylinders

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm47. CS16 Chlorine vaporisers

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm48. http://www.eurochlor.org

http://www.eurochlor.org/49. HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical and

cylindrical vesselshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

50. HS(G)34 Storage of LPG at fixed installationshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

51. HS(G)15 Storage of liquefied petroleum gas at factorieshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

52. CS5 Storage of LPG at fixed installations

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm53. BS 2594 : 1975

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm54. BS 2654 : 1989

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm55. BS 7777 : 1993

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm56. HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in total

capacity)http://www.hse.gov.uk/comah/sragtech/docspubguid.htm

57. HS(G)51 Storage of flammable liquids in containershttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

58. 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

59. HS(G)140 Safe use and handling of flammable liquidshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

60. HS(G)176 The storage of flammable liquids in tankshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

61. CS2 The storage of highly flammable liquidshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

62. CS15 The cleaning and gas freeing of tanks containing flammable residueshttp://www.hse.gov.uk/comah/sragtech/docspubguid.htm

63. Construction of plant64. Commissioning/verification of manufacture and construction standards65. BS 5500 : 1997

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm66. Pressure Systems Safety Regulations 2000 (PSSR regs)

http://www.opsi.gov.uk/si/si2000/20000128.htm67. ACOP: Safety of Pressure Systems. Pressure Systems Safety Regulations 2000

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm68. HS(G)93 The assessment of pressure vessels operating at low temperature

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm69. BS 1500: 1958

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm70. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm71. BS 1515: 1965

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm72. BS 5500

http://www.hse.gov.uk/comah/sragtech/docsbsi.htm73. Loss Prevention in the Process Industries

http://www.hse.gov.uk/comah/sragtech/docspubguid.htm74. Abbeystead Explosion (23/5/1984)

http://www.hse.gov.uk/comah/sragtech/caseabbeystead84.htm75. Beek (7/11/1975)

http://www.hse.gov.uk/comah/sragtech/casebeek75.htm76. Bhopal - Union Carbide (3/12/1984)

http://www.hse.gov.uk/comah/sragtech/caseuncarbide84.htm

77. BP Oil West Glamorgan (17/1/1981)http://www.hse.gov.uk/comah/sragtech/casebpglamorg81.htm

78. Explosion Caused by Explosion Suppression Systemhttp://www.hse.gov.uk/comah/sragtech/caseexplosion.htm

79. Feyzin (4/1/1966)http://www.hse.gov.uk/comah/sragtech/casefeyzin66.htm

80. Polymerisation Runaway Reaction (May 1992)http://www.hse.gov.uk/comah/sragtech/casepolymerisa92.htm

81. Seveso - Icmesa Chemical Company (9/7/1976)http://www.hse.gov.uk/comah/sragtech/caseseveso76.htm