Design Codes - Plant
This Technical Measures Document covers the design codes for plant.
Reference is made to relevant codes of practice and standards.
The relevant Level 2 Criteria are:
This Technical Measures Document includes the following sections:
Reference is made to relevant codes of practice and standards where
Related Technical Measures Documents are Corrosion
/ Selection of Materials, Design Codes -
Pipework, Explosion Relief, Relief
Systems / Vent Systems, Training, Plant
Modification / Change Procedures, Reaction
/ Product Testing.
Introduction to Plant design
The design of a process plant is a complex activity that will usually
involve many different disciplines over a considerable period of time. The
design may also go through many stages from the original research and
development phases, through conceptual design, detailed process design and
onto detailed engineering design and equipment selection. Many varied and
complex factors including safety, health, the environment, economic and
technical issues may have to be considered before the design is finalised -
See Technical Measures Document - Training.
At each stage it is important that the personnel involved have the
correct combination of technical competencies and experience in order to
ensure that all aspects of the design process are being adequately
addressed. Evidence of the qualifications, experience and training of people
involved in design activities should be presented in the Safety Report to
demonstrate that the complex issues associated with design have been
considered and a rigorous approach has been adopted.
The process design will often be an iterative process with many different
options being investigated and tested before a process is selected. In many
occasions a number of different options 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 any impurities that may be present. In the mechanical
design, the materials of construction chosen need to be compatible with the
process materials at the standard operating conditions and under excursion
conditions. The materials of construction also need to be compatible with
each other in terms of corrosion properties. Impurities which may cause
corrosion, and the possibility of erosion also need to be considered so that
the detailed mechanical design can ensure that sufficient strength is
available and suitable materials of construction are selected for
fabrication - See Technical Measures Document - Corrosion
/ Selection of Materials.
Detailed mechanical, structural, civil and electrical design of equipment
comes after the initial process 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 design processes and identifies the detailed design issues,
codes and applicable standards for the mechanical 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 process design where factors are
often added to allow some flexibility in process operation. For mechanical
and structural design the magnitude of design factors should allow for
uncertainties in material properties, design methods, fabrication and
Plant design should take account of the relevant codes and standards.
Conformity between projects can be achieved if standard designs are used
Codes and Standards
Modern engineering codes and standards cover a wide range of areas
- Materials, properties and compositions;
- Testing procedures; for example for performance, compositions and
- 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 published codes, such as BS5500, with
added extras which cover either technical or contractual matters. In the
safety report the base document for the in house codes should be clearly
stated and the key safety related deviations or enhancements demonstrated so
that the assessor can determine their adequacy.
A Safety Report should demonstrate that consideration has been given to
the appropriate standards and codes of practice developed by legislators,
regulators, professional institutions and trade associations. It should also
demonstrate that for any equipment that is installed, the operating
procedures, testing regimes and maintenance strategies that are in place
meet or exceed these requirements in terms of safety performance.
Inherently Safer design
The principles of inherently safer design are particularly important for
major hazard plants and should be considered during the design stage. The
Safety Report should adequately demonstrate that consideration has been
given to the concepts. Some companies now have design procedures that
require a review of designs and seek to ensure that inherently safer
concepts have been addressed.
Inherently safe design should be considered during the design stage in an
effort to reduce the hazard potential of the plant. Protective equipment
installed onto standard equipment to control accidents and protect people
from their consequences is often complex, expensive and requires regular
testing and maintenance. Attempts should be made to reduce the requirement
for such protective equipment by designing simpler and safer processes in
the first instance. A number of approaches can be considered but basically
an inherently safer plant can be achieved by minimising the inventories of
hazardous substances in storage and in process and hence the risk 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 a level whereby it poses a reduced hazard. This
often means carrying out the reaction or unit operation in a smaller
volume. It can be applied to a wide range of unit operations including
reactors, distillation and heat exchange but it may involve different
mechanisms and approaches having to be employed to the reaction
chemistry and control systems;
- Substitution - this technique involves replacing a hazardous material
(or feature) with a safer one. For example, flammable solvents,
refrigerants and heat transfer media can often be replaced by
non-flammable or less flammable (high boiling) materials. Often
hazardous processes can also be replaced by inherently safer processes
that do not involve the use of hazardous substances or which operate at
lower temperatures and pressures;
- Attenuation - using a hazardous material under less hazardous
conditions. For example, quantities of chlorine, ammonia and LPG can be
stored as refrigerated liquids under atmospheric pressure rather than
under pressure at ambient temperature. Materials likely to 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 by adding on protective equipment. For example,
the selection of some types of gaskets can reduce leak rates from
equipment in the event of a leak hence limiting the hazard. Many runaway
reactions can be prevented, either by changing the order of addition,
reducing the temperature or changing other parameters;
- Simplification - simpler plants are friendlier and safer than complex
plants and therefore less likely to have a major accident caused by
- Knock-on effects - plants should be designed to reduce the likelihood
of incidents producing knock-on effects or domino effects in other
- Avoid incorrect assembly - for critical equipment plants can be
designed so that incorrect assembly is difficult or impossible.
Consideration should be given to installing different types of
connections on inlet/outlet pipework to avoid the possibility of wrong
connections being made.
Further guidance on inherently safer design can be found in `Cheaper,
Safer Plants' - Kletz, T.A., 1984, IChemE, ISBN 0 8529 5167 1.
A 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 Safety Report. A number of different features can
be examined and assessed. Examples are given below:
- 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 to be demonstrated that major accident hazards are not
introduced as a result of the assessments that are undertaken. For example
any decisions taken as a result of a value engineering assessment that
result in standby equipment not be installed, or equipment of a lesser
specification being chosen should also demonstrate that the major accident
hazard implications of such decisions have also been considered.
A number of companies have developed detailed procedures for design
studies that incorporate many of these assessments into a formalised
Evidence that Hazard identification and/or HAZOP studies have been
carried out should be provided as evidence that a design has been evaluated
and carefully considered before being installed on the plant. See Technical
Measures Document - Plant Modification /
There are several general topics that are common to the detailed
mechanical design of many types of equipment and these are discussed in
greater detail below:
- Temperature and Pressure;
- Materials of Construction;
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 a major accident.
Temperature and pressure
Temperature and pressure are two basic design parameters. Any equipment
that is to be installed should be designed to withstand the foreseeable
temperature and pressure over the whole life of the plant. The combination
of temperature and pressure should be considered since this affects the
mechanical integrity of any equipment that is installed.
In determining design temperatures a number of factors should be
- the temperature of the fluids to be handled;
- Joule-Thomson effect (The Joule-Thomson effect is the change in
temperature that accompanies expansion of a gas without production of
work or transfer of heat. At ordinary temperatures and pressures, all
real gases except hydrogen and helium cool upon expansion and this
phenomenon is often utilised in liquefying gases);
- ambient temperatures;
- solar radiation; and
- heating and cooling medium temperatures.
Consideration needs to be given to the temperature of the fluids that are
to be handled and any excursions in temperature that could occur as a result
of the failure of temperature control systems. Account should be taken of
foreseeable reactions that may occur that are likely to increase or reduce
the heat input to the system.
The extremes of ambient temperature should be taken into account for
plant situated outside buildings. Solar radiation on the exposed surface
area of large storage tanks can significantly increase surface temperatures
for storage vessels leading to significant thermal expansion of vessel
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 be considered. External facilities
should be designed to accommodate the cycling of temperatures between
extreme weather conditions.
If secondary heating and cooling systems are employed then the maximum
and minimum temperatures that can be achieved by these secondary systems
should be assessed assuming failure of any control systems associated with
these systems. Care should be taken to ensure that the maximum temperature
that can be achieved by heating oil systems or the minimum temperature that
can be achieved by cryogenic cooling systems does not compromise the design
of the equipment. It should not adversely affect the mechanical strength and
hence integrity, or result in additional process hazards as a result of
overheating, decomposition or runaway reactions.
The strength of materials decreases with increasing temperature and
therefore the maximum design 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 in which the equipment is to be utilised have
been assessed and that an appropriate design temperature has been selected.
A vessel should be designed to withstand the maximum pressure to which it
is likely to be subjected in operation.
For vessels under internal pressure the design pressure is usually taken
at that which the relief valve is set. This is normally 5-10% above the
normal working pressure to avoid inadvertent operation during minor process
upsets. Vessels subjected to external pressure should be designed to resist
the maximum differential pressure that is likely to occur. Vessels likely to
be subjected to vacuum should be designed for full negative pressure of 1
bar unless fitted with an effective and reliable vacuum breaker device.
Account should also be taken of foreseeable reactions which may occur
that are likely to increase the heat input to a system, or gas evolution and
hence result in increased or decreased temperatures and pressures. Where
strongly exothermic reactions or runaway reactions are possible it may not
be possible to adequately design the equipment to withstand the maximum
predicted temperature and pressure. Under such circumstances some form of
pressure relief system may be appropriate in order to protect the equipment
and prevent catastrophic failure of the equipment from occurring. See
Technical Measures Document - Reaction /
Pressure vessels should be fitted with some form of pressure relief
device set at the design pressure of the equipment to relieve over-pressure
in a controlled manner - see Technical Measures Documents - Relief
Systems / Vent Systems, and Explosion
Relief. The set pressure of a relief valve should be such that the valve
opens when the pressure rise threatens the integrity of the vessel but not
when normal minor operating pressure deviations occur. It is necessary to
balance a number of factors in the selection of relief valve set pressures
since if the potential cause of pressure rise is runaway reaction then
setting the relief pressure at a high level above the normal operating
pressure may allow the reaction to reach a higher 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 (the overpressure - this is usually taken to be no more than
10% for design purposes) can be expected to increase above the set point for
the relief device. The accumulation in the vessel is the permitted increase
in the system pressure above the design pressure in an emergency
overpressure situation. The maximum allowable accumulated pressure (MAAP) is
specified within the various codes and this should be taken into account
when the relief valve set point is selected. Normally the relief valve set
point is set below or up to the maximum design pressure which allowing for
the overpressure during a relief event ensures that the overall pressure is
below the MAPP. Specific guidance on the recommendations for pressure relief
protective devices is given in Appendix J of BS 5500 :
1997. Other codes permit higher MAAPs in certain circumstances.
Discharge of hazardous substances from relief systems under emergency
conditions should be routed to secondary containment vessels or to safe
locations so that additional hazards to personnel or equipment and the
possible escalation of an incident does not occur. This should be considered
as part of the mechanical design of the equipment if such systems are to be
Evidence should be provided in the safety report that the process
conditions and environment in which the equipment is to be utilised have
been assessed and that an appropriate design pressure has been selected.
Evidence should be provided in the Safety Report that the relief systems
have been suitably designed and consideration has been given to the
discharge locations. Secondary containment facilities may be appropriate for
discharge of relief streams. Documentation for relief streams should be
available for inspection.
Consideration should be given to the possibility of pressure cycling in
equipment and subsequent failure of the equipment due to metal fatigue
Materials of construction
Another important consideration in mechanical design is the selection of
the material of construction.
In some cases the available materials of construction may constrain the
design temperatures and pressures that can be achieved and limit the design
of the equipment.
The most important characteristics that should be considered when
selecting a material of construction are summarised below:
- Tensile strength;
- 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,
- Availability in standard sizes;
The selection of a suitable material of construction is often carried out
by disciplines such as process engineers. The advice of specialist materials
engineers should be sought in the event of difficult applications being
The Safety report should contain evidence that the materials of
construction that have been selected are compatible with the process fluids
to be handled and the design conditions that have been chosen.
If materials to be used in the process are corrosive then this should be
taken into account in the plant design and layout. Materials of construction
should be carefully selected, protected where possible and regularly
inspected if the presence of corrosive materials or a corrosive environment
The layout of plant and equipment for corrosive materials is discussed in
`Safety and Management - A Guide for the Chemical Industry' - the
Association of British Chemical Manufacturers, 1964. Printed by W.Heffer
This topic is covered fully in the Technical Measures Document - Corrosion
/ Selection of Materials. See also Causes of
General guidance on corrosion allowances for pressure vessels is given in
BS 5500. 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 to
impurities and to fluid velocities, and that where doubt exists corrosion
tests should be carried out.
The life of equipment subjected to corrosive environments can be
increased by proper consideration of design details. Equipment should be
allowed to drain freely and completely and the internal surfaces should be
smooth and free from locations where corrosion products can accumulate.
Fluid velocities should be high enough to prevent deposition but not so high
as to cause erosion.
The corrosion allowance is the additional thickness of metal added to
allow for material lost by corrosion and erosion or scaling. For carbon and
low-alloy steels where severe corrosion is not expected a minimum allowance
of 2 mm is often used, where more severe corrosion is anticipated an
allowance of 4 mm is often used. Most design codes and standards specify a
minimum allowance of 1 mm.
A large proportion of failures in process plant and vessels are due to
corrosion. It is often the prime cause of deterioration and may occur on any
part of a vessel. The severity of the deterioration is strongly influenced
by the concentration, temperature, and nature of the corrosive 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
localised with 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 occurs primarily 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
include pneumatic conveying, wet steam flow, flashing flow and pump
cavitation. If erosion is likely to occur then more resistant materials
should be specified or the material surface protected in some way. For
example plastic inserts can be used to protect erosion-corrosion at the
inlet to heat exchanger tubes.
See also BS 5493: 1977 - Code of Practice for protective coating of iron
and steel structures against corrosion.
Specific equipment -
Design issues, codes and standards applicable to several general
categories of equipment have been identified and are discussed below in
- Pressure Vessels;
- Other Vessels (including Storage Tanks);
- Reactor Design;
- Heat Exchange Equipment;
- Furnaces and Boilers;
- Rotating Equipment.
There are numerous texts available on the details of pressure vessel
design however the basis of the design of pressure vessels is the use of
appropriate formulae for vessel dimensions in conjunction with suitable
values of design strength.
Pressure vessels can be divided into `simple vessels' and those that have
more complex features. The relevant standards and codes provide
comprehensive information about the design and manufacture of vessels and
vessel design and fabrication is an area well covered by standards 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 and international standards with one of the earliest being the
AOTC 1939/48/58 `Rules for the construction, testing and scantlings of metal
arc welded steel boilers and other pressure vessels'. The other principal
standards in the UK were BS 1500 and BS
1515, both of which are now withdrawn and superseded by BS
5500. The other most commonly used design code is ASME VIII. However it
is unusual, though not unknown, for companies and operators to employ their
own design codes.
Generally pressure vessel design codes covers equipment such as reactors,
distillation columns, storage drums, heaters, reboilers, vaporisers,
condensers, heat exchangers, bullets, spheres etc. Basically any equipment
with a "shell" that may experience some internal pressure is
covered. This section does not cover piping systems (see separate Technical
Measures Document on Design Codes Pipework),
atmospheric storage tanks and rotary machines. These are considered in
further detail later.
A simple pressure vessel does not have any complicated supports or
sections and the ends are dished. The main code for simple vessels is BS EN
286-1:1991. `Simple unfired pressure vessels designed to contain air or
nitrogen'. All aspects of designing and manufacturing the vessel are covered
in this code.
Traditionally the two principal codes and standards BS
5500 and ASME VIII, are employed in the design and manufacture of
pressure vessels within the United Kingdom. Importantly both of these demand
adherence to satisfaction in the design and manufacturing process of an
independent inspection authority. This authority is responsible for
adherence during both the design and construction phases in accordance with
the standard or code.
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;
Pressure vessels are subject to a variety of loads and other conditions
that cause stress and can result in failure and there are a number of design
features associated with pressure vessels that need to be carefully
- Discontinuities such as vessel ends, changes of cross-section and
changes of thickness;
- Joints (bolted and welded);
- Bimetallic joints;
- Holes and openings;
- 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 pressure envelope, but critical to vessel integrity i.e.
any failure which could lead to breach of the pressure boundary e.g. vessel
skirt or support legs. Other factors which require careful consideration
include; a means of in-service periodic examination i.e. a means of
determining the internal condition of the vessel by the provision of access
openings; a means of draining and venting the vessel; and means by which the
vessel can be safely filled and discharged.
Materials of construction
Materials used for the manufacture of pressure vessels should have
appropriate properties for all operating conditions that are reasonably
foreseeable, and for all test conditions. They should be sufficiently
chemically resistant to the fluid contained and not be significantly
affected by ageing. The materials should be selected in order to avoid
corrosion 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 material used, but other equally
important factors such as corrosion/erosion allowance, low temperature
application etc. can determine selection.
Clearly in the choice of material selection it is important that the
material selected not only has properties which are suited to that
particular application, but also that its suitability with regard to
fabrication is also taken into account. Several different methods are
used to construct pressure vessels, most however are constructed using
Where an American, British or European code is used for vessel design
and specific materials are quoted within the code it is important that
the correct materials are used in order that the design is not
Where carbon steel will not resist expected corrosion or erosion or
could cause contamination of the product, vessels may be lined with
other metals or non-metals. A lined 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 plate
material rolled or bonded before fabrication of the vessel, or they may
be separate sheets of 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 be used to
resist corrosion and erosion or to insulate and reduce the temperature
on the walls of a pressure vessel. The most common materials are
reinforced concrete, insulating material, carbon brick, rubber, glass
Many 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 most vacuum vessels have
either internal or external stiffening rings. Heat exchangers have
internal tube bundles with baffle and support plates. These internals
may be made from a wide range of materials but care should be taken that
the materials selected for the internals are compatible with the
materials chosen for fabrication of the main components.
Pressure vessels are subject to a variety of loads and other conditions
that cause stress and in certain cases may cause serious failure. Any design
should take into account the most likely failure modes and causes of
deterioration. Deterioration is possible on all vessel surfaces in contact
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;
- Mechanical and thermal fatigue;
- Mechanical shock;
- Brittle failure;
- 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 of Materials.
Design Codes and Standards
Two principal codes and standards are employed in the design and
manufacture of pressure vessels - the American ASME VIII system and BS
5500 in the UK. Importantly both of these demand adherence to
satisfaction in the design and manufacturing process of an independent
inspection authority. This authority is responsible for adherence during
both the design and construction phases in accordance with the standard
code. The codes and standards cover design, materials of construction,
fabrication (manufacture and workmanship), inspection and testing, and form
the basis of agreement between the manufacturer and customer and the
appointed independent inspection authority. These codes relate to vessels
fabricated in carbon and alloy steels and aluminium.
Computer programmes to aid the design of vessels to BS
5500 and the ASME VIII codes are commercially available.
Non-metallic materials of construction
Although the majority of pressure vessels are constructed from metallic
compounds pressure vessels can also be constructed from materials such as
glass reinforced plastic (GRP), or fibre reinforced plastic (FRP). The main
relevant standard is BS 4994:1987 - Specification for Design and
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
description atmospheric storage is applied to any tank that is designed to
be used within a limited range of atmospheric pressure, either open to the
atmosphere or enclosed.
Vertical storage tanks with flat bases and conical roofs are often used
for the storage of liquids at atmospheric pressure and may vary in size
considerably. The main load to be considered in the 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 any likely snow loading should also be considered.
The design of atmospheric storage tanks in general is governed by API Std
620 Design and construction of large, welded, low-pressure storage tanks and
API Std 650 Welded steel tanks for oil storage.
Tanks should be suitable for their operational duty and all reasonably
expected forces such as tank contents, ground settlement, frost, wind and
snow loadings, earthquake and others as appropriate. The selection of the
type of tank to be used for a particular duty will be influenced by
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 the stored material e.g. flash
point, vapour pressure, electrical conductivity etc.
API Standard 2000 gives guidance on the design of vents to prevent
pressure changes that would 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 a hazard.
Reactors are often the centre of most processes and their design is of
utmost importance when considering the safety hazards of a plant. Reactors
are most often considered as pressure vessels and the mechanical design
should be in accordance with the codes and standards described earlier.
Reactor design should minimise the possibility of a hazardous situation
developing and provide the 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 systems
consideration should be given to the implications of the release of reactor
contents and containment and control systems may be necessary to prevent a
hazardous situation from developing as a result of the discharge of a relief
The design of the reactor may affect the efficiency of the reaction
process and hence the generation of by-products and impurities. The
effectiveness of the reaction step will often determine 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 to consider are given below:
Addition of reactants - the order and rate of addition of the reactants
may affect the rate of reaction and the generation of by-products. The
generation of unstable by-products or excessive reaction rates may increase
the potential for a hazardous situation to develop. The position of addition
of reactants may also be important - sub-surface and directly into an
intimate mixing zone 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 directly influence 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 design of the reaction
system. Methods for detecting the failure of a mixing/agitation system
and/or stopping the flow of reactants into the reactor may be
appropriate especially if there is the possibility of two phases forming
on agitation failure which may react exothermically/vigorously when
agitation is recommenced. See Technical Measures Documents - Reaction
/ Product Testing and Control Systems;
- Heat removal - for exothermic reactions the control of the reaction
system and the heat removal systems should be carefully considered.
Consideration should be given to the modes of failure of the control and
cooling systems to ensure that the hazards of a runaway exothermic
reaction are minimised;
- Phase - the reaction may take place in the gas, liquid or sometimes
solid phase. The way in which the reactants are brought into contact may
influence the efficiency of the reaction and 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 given to the selection of the catalyst
system in order to minimise the risks associated. If a catalyst is
required then additional separation steps to remove the catalyst may
subsequently be required.
The safety report should describe how the reactor system has been
designed with the principles of safe design in mind and how the selection of
the mixing, chemical addition systems and relief systems have been selected
in order to minimise the potential for a major accident.
The transfer of heat between two process streams is a common activity and
requirement on a chemical plant. A number of direct or indirect techniques
can be employed. The most common form of equipment used to transfer heat is
a heat exchanger which can be designed in many different shapes, sizes and
configurations necessary to obtain the required heat transfer between one
stream and another. A number of different heat transfer operations are
possible with 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 designed accordingly to account for the differing
The basic design is commenced by an approximate sizing of the unit based
on assumptions made concerning the heat transfer characteristics of the
substances involved and the anticipated materials of construction. More
detailed calculations are then required to confirm and refine the original
design and to identify an optimum layout. Once the process design has been
completed 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 design engineers however is `Process Heat Transfer - D.Q.Kern,
International Student Edition, McGraw Hill, ISBN 0070341907.
The mechanical design features, fabrication, materials of construction
and testing of shell and tube heat exchangers is covered by `BS 3274: 1960-
Tubular Heat Exchangers for General Purposes'.
The standards of the American Tubular Heat Exchanger Manufacturers
Association (TEMA standards) are also widely used. Many companies also have
their own standards to supplement these various requirements.
The TEMA standards give the preferred shell and tube dimensions, the
design and manufacturing tolerances, corrosion allowances and the
recommended design stresses for materials of construction.
Design temperatures and pressures for exchangers are usually specified
with a margin of safety beyond the conditions normally anticipated.
Typically the design pressure may be 170 kPa greater than the maximum
anticipated during operation or at pump shutoff, and the temperature is
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 of an exchanger is
normally a pressure vessel and should be designed in accordance with the
relevant pressure vessel design code - BS 5500 or
ASME VIII (Rules for construction of pressure 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 exchanger equipment especially if sensitive materials are
involved, for example materials which may undergo exothermic decomposition.
The safety report should demonstrate that heat exchange equipment has
been designed and maintained in accordance with the relevant codes and
standards and that consideration has been given to the various failure modes
that could occur and the implications of such events. It should be
demonstrated that wherever possible measures have been taken to prevent,
control or mitigate the consequences of such events by the appropriate
selection of materials of construction, fabrication methods, instrumentation
and control or others.
Furnaces and boilers are items of equipment that are often found as part
of process plant and are used for a variety of purposes such as waste heat
recovery, steam generation, destruction of off-gases etc.
The design may involve the interaction of many different variables
including water/steam circulation systems, fuel characteristics (liquid,
gaseous or solid fuels), ignition control systems, heat input and heat
The design of the furnace or boiler enclosure should be able to withstand
the thermal conditions associated with the system and specialist designs are
often required. Many codes and standards exist for boiler design.
The elimination of hazards in burner design is a fundamental design
requirement. Explosions can occur during start up if ignition design is not
carefully considered. Leaks of fuel can cause explosive atmospheres when
ignition is attempted. For these reasons consideration should be given to
inerting /ventilation systems prior to ignition sequences to ensure
explosive atmospheres 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 be placed upon single valves for
isolation. Careful consideration of the configuration of the pipework should
also be considered to ensure that the flow of fuel into the system after the
flame has failed or valves have been closed is minimised.
Purging facilities are essential to ensure that the firing space is free
from a flammable atmosphere prior to start-up ignition.
A safety report should demonstrate that any furnace/boiler system is
designed and maintained to the relevant codes and standards and that
consideration has been given to the major hazards associated with the
start-up, shutdown and operation of the equipment in terms of the fire and
explosion potential of such systems. It should be demonstrated that the
risks of an explosion occurring have been minimised by the design of the
burner control management system and the layout and design of the fuel
Process machines are particularly important items of equipment in process
plants and in relation to pressure systems since they are required to
provide the motive force necessary to transfer process fluids (liquids,
solids and gases) from one area of operation to another. A machine system is
any reciprocating or rotating device that is used to transfer or to produce
a change in properties 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 the rotating/vibrating nature of such equipment pressure and
flow fluctuations may be caused and these can affect the operation of other
The basic requirements to define the application for pumps, fans and
compressors are usually the 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 materials of
construction to be used or the type of device that can be considered. Many
designs have become standardised based on experience and numerous standards
(API standards, ASME standards, 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.
Many pumps are of the centrifugal type, although positive displacement
types (such as reciprocating and screw types) are also used. Pumps are
available throughout a vast range of sizes and capacities and are also
available in a wide range of materials including various metals and
plastics. Sealing of pumps is a very important consideration and is
discussed later. The primary advantage of a centrifugal pump is its
simplicity. Pumps are particularly vulnerable to mal-operation and poor
installation practices. Proper installation and high quality maintenance is
essential for safe operation.
Problems associated with centrifugal pumps can include bearing and seal
failure. Cavitation (the collapse of vapour bubbles in a flowing liquid
leading to vibration, noise and erosion) and dead head running (attempting
to run a pump without an outlet for the fluid, for example against a closed
valve) can also result in damage to the pumping equipment. Misalignment
between pump and motor is also a common cause of catastrophic failure.
Seal-less or `canned pumps' are often used where any leakage is
considered unacceptable. In a canned pump the impeller of the pump and the
rotor of the motor are mounted on an integral shaft which is encased so that
the process fluid can circulate in the space which is normally the air gap
of the motor.
Key parameters for pump selection are the liquid to be handled, the total
dynamic head, the suction and discharge heads, temperature, viscosity,
vapour pressure, specific gravity, liquid corrosion characteristics, the
presence of solids which may cause erosion etc.
Both positive displacement and centrifugal compressors are used in the
process industry. They are complex machines and their reliability is
crucial. It is very important that they are maintained to high operational
standards. Centrifugal compressors are by far the most common although
compression is generally lower than that given by reciprocating machines.
They are used in both process gas and refrigeration duties. On centrifugal
compressors some of the principal malfunctions include rotor or shaft
failure, bearing failure, vibration and surge. Reciprocating compressors are
utilised for higher compression requirements. They may be either single or
multi-stage units. Air compressors for dry air require special consideration
and specific codes and standards exist.
The main applications for fans are for high flow, low pressure
applications such as supplying air for drying, conveying material suspended
in a gas stream, removing fumes, or in condensing towers. These units can be
either centrifugal or axial flow type. They are simple machines but proper
installation and maintenance is required to ensure high reliability and safe
One of the main causes of failure of rotating equipment is vibration.
This often causes seal damage or fatigue failure and subsequent leakage and
can result in a major accident. Numerous factors can result in vibration
occurring including cavitation, impeller imbalance, loose bearings and
pulses in the pipe. ASME standards recommend that pumps should be
periodically monitored to detect vibration that should normally fall within
prescribed limits as determined by the manufacturer. This should be
initially confirmed on installation and then periodically checked. If
measured levels exceed prescribed values then preventative maintenance is
required and should be performed. By collection and analysis of vibration
signatures of rotating equipment it is possible to identify which components
of the system are responsible for particular frequencies of the vibration
signal. It is then possible to identify the component that is deteriorating
and responsible for the vibration that is occurring.
Seals are very important and often critical components in large rotating
machinery and in systems which are flanged/jointed such as heat exchangers
or pipework systems. Failure of a sealing 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 many factors
that govern the selection of seals for a particular application including
the product being handled, the environment which the seal is installed in,
the arrangement of the seal, the equipment the seal is to be installed in,
secondary packing requirements, seal face combinations, seal gland plate
arrangements, and main seal body etc. The materials used for seals 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
- 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 normal both lubricating and cooling the packing material. The
chief advantages of this type of sealing arrangement are the simplicity and
the ease of adjustment or replacement. The disadvantages are 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 in applications where a leak tight seal of almost any fluid is
required. Mechanical seals find their best application where fluids should
be contained under substantial pressure. They can range from the simplest
single seal arrangement to complicated sophisticated double seals with
monitoring of the interspace. Some mechanical seals are assemblies of great
complexity and consist of components manufactured to very high tolerances.
They are often fitted as complete cartridge type units. Some sealing
arrangements require constant lubrication often from the process fluid
itself whilst others require external lubrication arrangements.
Maintenance, inspection and monitoring
Plant 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 of
which there are a number of techniques. The aim of such techniques is to
identify deterioration and pre-empt imminent failures and so secure
reliable/available plant, particularly for production and safety critical
items. Some of these techniques are identified below:
- Vibration monitoring;
- Shock pulse monitoring;
- Acoustic emission monitoring;
- Oil analysis.
All machine systems should be assessed according to the hazard presented
if the machine or any associated protective system should fail.
Machine systems that have been assessed to present unacceptable
consequences if the machine or protective system should fail may be
classified as a `Critical Machine System' and given 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.
Structures are required to provide support for plant and should be able
to withstand all foreseeable loadings and operational extremes throughout
the life of the plant. Failure of any structural component could lead to
initiation of a major accident. For full guidance on Design
Codes - Buildings / Structures see relevant Technical Measures Document.
Structural design should take into account natural events such as wind
loadings, snow loadings and seismic activity and also plant excursions
Maps showing the wind speeds to be used in the design of structures at
locations in the UK are given in British Standards Code of Practice BS CP 3:
1972: Basic Data for the Design of Buildings, Chapter V Loading: Part 2 Wind
Loads. Typical values are around 50 m/s (112 miles per hour). The code
of practice also gives methods estimating the dynamic wind pressure on
buildings and structures of various shapes.
Protection against lightning strikes on process plant located outside
buildings is required since lightning is a potential ignition source
especially for fires involving storage tanks. Lightning protection should be
provided and guidance is available in BS 6651 : 1992
Code of Practice for Protection of Structures against Lightning.
See also Technical Measures Document - Earthing.
For the following substances general published codes exist giving full
design details for storage and handling.
The design of systems for chlorine requires special consideration since
chlorine is highly toxic and, if wet, also very corrosive.
Chlorine is usually stored under pressure at atmospheric temperature, but
may also be stored fully refrigerated (-34°C) at atmospheric pressure.
A number of publications are dedicated to the handling of chlorine and
specific guidance is given in:
- Chlorine Manual, 1986, Pamphlet 1, Chlorine Institute.
- Non-refrigerated Liquid Chlorine Storage, 1982, Pamphlet 5, Chlorine
- Refrigerated Liquid Chlorine Storage, 1984, Pamphlet 78, Chlorine
- 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 Chlorine Storage Guide), CIA, 1980/9.
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 a number of publications.
Further details can be obtained via the website http://www.eurochlor.org.
- 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 of materials of construction for chlorine systems.
Anhydrous ammonia, boiling point -33°C, is normally stored as a liquid
either under pressure or at atmospheric pressure in refrigerated facilities.
A number of publications are dedicated to the handling of ammonia and
specific guidance is given in:
HS(G)30 Storage of anhydrous ammonia under
pressure in the UK : spherical and cylindrical vessels, HSE, 1986 (Not
in current HSE list).
Gives advice for the appropriate materials of construction for ammonia
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
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.
Propane and Butane are referred to as liquefied petroleum gas (LPG) in
accordance with BS 4250: Specification for commercial butane and propane.
Fully refrigerated storage is required at atmospheric 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,
HS(G)15 Storage of liquefied petroleum gas at
CS5 Storage of LPG at fixed installations,
LPGA COP 1 Bulk LPG storage at fixed installations. Part 1 : Design,
installation and operation of vessels located above ground, 2000.
LPGA COP 1 Bulk LPG storage at fixed installations. Part 2: Small bulk
propane installations for domestic 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 storage vessels, 2000.
LPGA COP 15 Valves and fittings for LPG service, Part 1 Safety valves,
LPGA COP 17 Purging LPG vessels and systems, 2000.
EEMUA 147. Recommendations for the design and construction of
refrigerated liquefied gas storage tanks.
Liquefied petroleum gas. IP Model code of safe practice: Part 9.
A number of standards and codes exist for the storage of petroleum
products and flammable liquids generally. A range of different main types of
storage tanks and vessels for liquids and liquefied 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, American Petroleum Institute, 1990.
- API Std 650 Welded steel tanks for oil storage, American Petroleum
- BS 2594 : 1975 Specification for carbon steel
welded horizontal cylindrical storage tanks.
- BS 2654 : 1989 Specification for manufacture of
vertical steel welded non-refrigerated storage tanks with butt-welded shells
for the petroleum industry.
- BS 4741: 1971 Specification for vertical cylindrical welded steel storage
tanks for low temperature service: single-wall tanks for temperatures down
- BS 5387: 1976 Specification for vertical cylindrical welded steel storage
tanks for low temperature service: double-wall tanks for temperatures down
- BS 7777 : 1993 Flat-bottomed, vertical,
cylindrical storage tanks for low temperature service.
- This BS supersedes BS 4741:1971 and BS 5387: 1976 both of which are
- BS 799: 1972 Oil Burning Equipment, Part 5 Specification for oil storage
- 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 total capacity), HSE, 1990.
- HS(G)51 Storage of flammable liquids in containers, HSE, 1998.
- HS(G)52 The storage of flammable liquids in
fixed tanks (exceeding 10000 cu. m in total capacity), HSE, 1991.
- HS(G)140 Safe use and handling of flammable
liquids, HSE, 1996.
- HS(G)176 The storage of flammable liquids in
tanks, HSE, 1998.
- CS2 The storage of highly flammable liquids,
- 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, HSE, 1997.
- RC 20 Recommendations for the storage and use of flammable liquids, LPC,
- EEMUA 147. Recommendations for the design and construction of
refrigerated liquefied gas storage tanks, 1986.
Construction of plant
It is critically important that following the detailed design of a plant
that the construction phase is carried out according to the original
specification and that no additional hazards are introduced to the plant
during the construction phase. Poor construction can result in the integrity
of the whole system being compromised resulting in an increased risk of a
Building and construction are covered by a series of different building
regulation including the following:
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 the responsibilities of the various parties in a construction
project. Also available is the Approved Code 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.
of manufacture and construction standards
It is important to demonstrate that the correct materials of construction
have been used and that appropriate construction techniques have been
employed so as not to introduce construction faults and flaws into the
plant. Evidence in the form of documentation which shows that checks were
carried out during the construction phase are important to prove that the
construction phase of the project has been adequately supervised.
Documentation should show that the equipment supplied and installed is of
the correct material of construction (and has received the correct heat
treatment if appropriate), is the correct item/part/unit number and is as
specified in the design schedule.
Documentation should also show that the workmanship is of the quality
specified and that inspection and acceptance tests were carried out as
required under the contract.
Commissioning of equipment should be carried out and records kept of the
Evidence of the following should be available:
- Certificates of mechanical completion and hand over certificates;
- Mechanical completion checks - check that installed equipment is ready
for commissioning, is installed correctly and that the component parts
operate as specified and that any ancillary equipment is installed and
- 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 accordance with engineering drawings. Identify as built
- Check that mechanical equipment conforms to specified codes and
standards, is installed in accordance with the relevant drawings and
meets the performance tests specified;
- Each item of equipment should be checked for compliance with the
specification. This may mean witnessing aspects such as examination or
testing at the manufacturers works;· Check any internal fittings are
installed, are of the correct dimensions and are firmly 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, protective devices tests;
- Sub-system and system tests - dynamic safe fluid test (water test),
dynamic process fluid test;
- Test utilities, instruments, etc. Simulate faults for testing
The following documentation should be available:
- Modification records;
- Equipment examination records - pressure vessels, pressure piping,
- Equipment Test Records - pressure & leak tests, pressure relief
valve tests, rotating machinery tests, instrument tests, computer system
- Computer tests;
- Spares inventories;
- Safety review records;
- Environmental review records;
- Reservation lists.
The management of the commissioning and verification stages should be
identified under the Safety 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 ensure that
corrective action is taken on the identification of discrepancies between
installed equipment and the design intent and to control any deviations from
Evidence of a number of pre-commissioning and commissioning checks should
be presented to verify that the equipment as installed has been tested and
is suitable for operation and meets the design intent. These may include:
- Pre-commissioning Hazops;
- Check that information is installed as per the process flow diagrams
and engineering line diagrams;
- 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 guidance
The following codes of practice may be useful reading for the assessor
when considering the process design of plant and equipment. Codes and
guidance associated with the design of specific items of equipment (as
discussed in previous sections) are given below. Not all the codes or
guidance documents identified below are currently available and many have
been superseded. 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 - 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).
Other useful documents include:
ACOP: Safety of Pressure Systems. Pressure
Systems Safety Regulations 2000. Ref L122. ISBN 0 7176 1767 X. Published
by HSE Books 2000.
HS(G)93 The assessment of pressure vessels
operating at low temperature, HSE, 1993.
BS 1500: 1958 - Fusion Welded Pressure Vessels
for General Purposes.
BS 5500 replaced this conventional code in the UK in 1976.
BS 1515: 1965 - Fusion Welded Pressure Vessels
for Use in the Chemical, Petroleum and Allied Industries.
BS 5500 replaced this advanced code in 1976.
BS EN 286-1:1991. Simple unfired pressure vessels designed to contain air
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 steels
Part 2 (1988) - Specification for alloy steels
Part 3 (1990) - Specification for corrosion and heat resisting steels
BS 1502: 1990 - Specification for steels for fired and unfired pressure
vessels: sections and bars
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 bolting material to be used in pressure retaining
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 low temperature service: double wall tanks for
temperatures down to -196°C.
ISO R831: Recommendations for Stationary Boilers which is applicable to
Pressure Vessels : Non-metallic materials of construction
BS 4994: 1987 - Specification for Design and Construction of Vessels and
Tanks in Reinforced Plastics.
BS 6374: 1984 - Lining of equipment with polymeric materials for the
ASME Boiler and Pressure Code Part X, Fiberglass Reinforced Plastic
Pressure Vessels (1992).
ASTM D 4021-86 Standard Specification for Contact Moulded
Glass-fiber-reinforced Thermosetting Resin Underground Petroleum Storage
ASTM D 4097-88 Standard Specification for Contact Moulded
Glass-fiber-reinforced Thermosetting Resin Chemical Resistant Tanks.
Pressure vessel systems examination. IP Model code of safe practice: Part
Other Vessels (including Storage Tanks)
API Std 620 Design and construction of large, welded, low-pressure
storage tanks, American Petroleum Institute, 1990.
API Std 650 Welded steel tanks for oil storage, American Petroleum
API Std 653 Tank inspection, repair, alteration, and reconstruction,
American Petroleum Institute, 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 and refrigerated, American Petroleum Institute, 1998.
BS 3274: 1960- Tubular Heat Exchangers for General Purposes.
American Tubular Heat Exchanger Manufacturers Association (TEMA
The TEMA standards cover three classes of heat exchanger:
- Class R - generally severe duties in the petroleum and related
- Class C - moderate duties in commercial and general process
- 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
BS 1113: 1992 - Specification for design and manufacture of water-tube
steam generating plant (including superheaters, reheaters and steel tube
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
API Standard 560 - Fired heaters for general refinery services, 1986.
BS 7322: 1990 Specification for the Design and Construction of
Reciprocating Type Compressors for the Process Industry
API Standard 610: 1989 Centrifugal Pumps for General Refinery Services.
API Standard 611: 1988 General Purpose Steam Turbines for Refinery
API Standard 612: 1987 Special Purpose Steam Turbines for Refinery
API Standard 613: 1988 Special Purpose Gear Units for Refinery Services.
API Standard 614: 1992 Lubrication, shaft-sealing, and Control Oil
systems for special purpose applications.
API Standard 616: 1992 Gas Turbines for Refinery Services.
API Standard 617: 1988 Centrifugal Compressors for General Refinery
API Standard 618: 1986 Reciprocating Compressors for General Refinery
API Standard 619: 1985 Rotary Type Positive Displacement Compressors for
General Refinery Services.
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
ASME B73.1M - 1991 Specifications for Horizontal End Suction Centrifugal
Pumps for Chemical Industries.
ASME B73.2M - 1991 Specifications for Vertical In-line Centrifugal Pumps
for Chemical Industries.
BS 767: 1987 - Specification for centrifuges of the basket and bowl type
for use in industrial and commercial 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 compressors for the process Industry.
BS 4675: 1976 - Mechanical vibration in rotating machinery
Further reading material
Lees, F.P., Loss Prevention in the Process
Industries: Hazard Identification, Assessment and 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