Design and Application of Electrical Equipment

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DESIGN AND SPECIFICATION OF ELECTRICAL EQUIPMENT FOR USE IN
FLAMMABLE ATMOSPHERE
By Name
Course
Instructor
Institution
Location
Date

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Table of Contents
1.0 Introduction..........................................................................................................................2
2.0 Literature review..................................................................................................................3
2.1 Electric Equipment systems which are intended to be used in Flammable atmospheres.. . .3
2.2 Hazardous area classification for flammable atmospheres..................................................4
2.3 Zoning..................................................................................................................................5
2.4 Selection of equipment.........................................................................................................6
2.5 Ignition sources....................................................................................................................7
2.7 Controlling of ignition sources.............................................................................................9
3.0 Conclusion..........................................................................................................................11
4.0 References..........................................................................................................................12

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1.0 Introduction
Flammable atmospheres are created when highly flammable mist, gases, dust or vapour are
mixed with air and this generates a risk of explosion or fire. The amount of substance that is
needed to create an explosion dependents on the substance in question. The areas which are
faced with risks of explosions are referred to as potentially flammable atmosphere.
Potentially flammable atmospheres can be found in all industries ranging from foods and
pharmaceuticals, wood and power to chemical processing. They can also be referred to as
hazardous locations or hazardous areas. The number of substances/products which are
flammable when mixed with air is very large. This clearly indicates that there are various
industries that can have a potentially flammable atmosphere somewhere in there process.
Some of the industries are not so obvious to have potentially flammable atmosphere in their
process (Bender, 2017, p. 34). For instance, the saw mills by default are considered not to be
a potential explosive atmosphere, but if the saw dust is allowed to accumulate in large
amount the area where the saw mill is located becomes a potential hazardous area.
Flammable atmospheres can be created by flammable fuels, cleaning solvents, paints,
combustible dusts, naturally occurring reactions that may produce methane gas and hydrogen
from battery charging or boiler cleaning. Many injuries and deaths have occurred due to the
explosions and fires which are caused by flammable atmospheres.
The design and specification of electrical equipment to be used in flammable atmospheres
include selection of equipment, requirements of earthing, protection techniques, entity
calculations of Ex i, motor protection of Ex e, requirements of cable rating, power
calculations of maximum dissipate and general principles for designing.
The hazardous agents have the ability to cause harm towards weak targets, which in most
cases are used as substitutable in nature. Moreover, in case of the risk assessment, this act is
distinctly in nature. On other hand, electronic equipment involves controlled conduction

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regarding electrons. This research paper is about specification and design of electrical
equipment which are to be used in flammable areas (Calixto, 2016, p. 56).
2.0 Literature review
2.1 Electric Equipment systems which are intended to be used in Flammable atmospheres.
The objective of Directive 94/4/EC is to permit the free trade of ‘ATEX’ equipment and the
protective systems within the European Union through removing documentation for each
member and need for separate testing.
Suppliers and manufacturers of the electrical equipment must ensure that all the essential
safety and health requirements are met by their products and the products must undergo the
appropriate conformity procedures. The procedures usually involve certification and testing
by a third part which is referred to as a notified Body (Cheyne, 2016, p. 114).
The suppliers and the manufacturers can certify their products which are intended to be used
in less hazardous flammable atmospheres. Once the electrical equipment has been certified, it
is marked with ‘EX’ symbol to illustrate that it has been certified.
The purpose of certification is to ensure that the electrical equipment meets all the safety and
health requirements regarding to it. The certificate also ensures that sufficient information is
supplied together with the equipment to enable the users to use it correctly and safely (Ching,
2016, p. 157).
What is ATEX?
ATEX refers to a term which is commonly given to the two European Directives for the
purpose of controlling flammable atmospheres.

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a) Directive 99/92/EC. This is a European Directive about the requirements for
improving safety and health protection of the workers who are at the risk of
flammable atmospheres.
b) Directive 94/9/EC, this is a European Directive on estimation of the law member
states regarding protective and equipment systems which are intended to be used in
flammable atmospheres (Lees, 2016, p. 72).
2.2 Hazardous zone classification for explosive atmospheres
Hazardous region classification may be conducted directly with the typical installation which
is defined in an established code. The start point for the classification of hazardous zones was
to identify the sources of hazardous agents (Geoffrey Bottrill, 2015, p. 252). These might
have risen from:
 Oil and gas production and processing plants
 Petrol or refuelling stations
 Oil refineries
 Chemical and petrochemical processing plants
 Paper and textile industries
 Printing industries
 Underground coal mines
 Surfaces coating industries
 Hospital operating theatres
 Sewage treatment plants
 Grain storage and handling industries
 Gas distribution, pipeline centres and Light metal working

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The disastrous failures such as line or vessel rhapsody are not measured by the area
classification study. Hazard study and primary Hazard Analysis (PHA) should consider these
unique events.
In the United Kingdom, the standard which is commonly applied for determining the area
extent and classification is BS EN 600079 part 10 that contains a wide applicability. The
updated version makes it clear the direct relationship between the amount of flammable
vapour or gases which is allowed to be released, the ventilation available at that given site
and the area number (Groh, 2017, p. 393). BS EN 600079 a basic calculation which relates
the zone size to the frequency of release of gases or vapour, but the calculation is not of any
value to the liquid released, where the size hazardous area is controlled by the rate of
evaporation.
2.3 Zoning
The hazardous areas are clearly defined in Dangerous Substances and Explosive
Atmospheres Regulations 2002 (DSEAR) as, ‘any place in which an explosive atmosphere
may occur in quantities such has to require special precautions to protect the safety of
workers’’. In this study a lot of focus is put on the Design and specification of electrical
equipment that can be used in flammable atmospheres, as given in BS EN 600079 part 10.
Area classification refers to a technique classifying and analysing the environment flammable
gas atmosphere that may exist (Jespen, 2016, p. 38). The main objective of area classification
is to enhance the proper selection and installation of equipment which can be safely used in
the environment, by taking consideration of properties of flammable materials that will be
present. The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR)
precisely extends the initial scoop of this study to take into justification of non-electrical
sources of ignition and the portable equipment that poses a danger of ignition.

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The hazardous regions are categorised into zones depending on valuation of regularity of
happening and the extent of flammable atmosphere as follows:
Zone 0: hazardous region in which the flammable gas atmosphere is existing for long period.
Zone 1: hazardous region in which the flammable gas atmosphere is possible to exist in
standard conditions (Jones, 2010, p. 65).
Zone 2: hazardous region in which the flammable gas atmosphere is impossible to happen in
usual conditions, but in the cases where it occurs it exists for a short time.
The zone definition of a location does not take account the effects of release. If this aspect is
considered to be significant, it may be solved by improving the specification equipment of
activities which are permissible within the zone.
2.4 Equipment Selection
DSEAR outlines the relationship amongst the zones and the electrical equipment that can be
used in that given zone, this refers to the case of new connections. The equipment groups are
demarcated by the TEX equipment order which is clearly outlined in the United Kingdom
law as the protective and equipment systems for application in possibly flammable
atmospheres regulation 1996.The principles clearly outlines the various protection ideas with
more groups of the equipment according to the temperature classifications and gas
subdivisions. Over many years many electrical standards have been developed of which
currently are set on international levels.
The DSEAR ACOP explains the requirements regarding the prevailing equipment. There are
protection ideas of designing and specifying the equipment to the different categories.
For the purpose of correct selection of electrical equipment to be used in flammable
atmospheres the following data is required.

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 Arrangement of hazardous area as shown in the table below.
 Ignition temperature and temperature class of the vapour or gas involved as per the
table below.
Temperature classification Maximum surface temperature, o C Ignition Temp o C
T1 450 >450
T2 300 >300
T3 200 >200
T4 135 >135
T5 100 >100
T6 85 >85
In case there are various types of flammable materials which are available within the given
location, the material which presents the highest classification dictates the entire area
classification.
2.5 Ignition sources
Ignition resource refers to the energy source which provides adequate energy to ignite a
explosive atmosphere. The list below shows some of the ignition sources:
 Flames
 Use of matches and cigarettes
 Direct process heating and direct fired spaces
 Friction sparks or heating
 Impact sparks
 Electromagnetic radiations of various wavelengths
 Stray currents from electrical equipment

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 Mechanical machinery
Electrical equipment as ignition sources
 Operating electrical equipment with a combustible engine such as generators and
forklift can be great sources of ignition to the flammable atmosphere due to the
electric sparks which are produced while the engine is running.
 Portable tools such as radios and fans some time they produce electrical sparks which
might ignite the flammable environment to cause fires or explosions. Sometimes the
surfaces of this tools become very hot which can make the flammable atmospheres to
explode.
 There are electrical equipment which produce naked flames and pilot lights which
might be of great threat to the hazardous zones (Kramer, 2011, p. 45).
 The powered circuits and circuit fixed electrical systems with potential electric sparks
have been greatly linked to the explosions which have occurred in the recent past.
This systems includes hot working activities such as grinding and welding are
considered to be the most common ignition sources in the flammable atmosphere.
 The presence of static electricity in most of the electric equipment lead to electrostatic
discharge which is generated by processes such as: low conductivity liquid such as
liquid hydrocarbons, flowing at high speed over the pipes and other related fittings.
2.7 Controlling of ignition sources
The ignition sources of flammable atmospheres should be efficiently organised in all
hazardous zones by arrangement of measures, work and design system such as:

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 By means of electrical instrumentation and equipment categorised for the region in
which it is situated. For the case of new mechanical tools they require to be chosen in
the same manner.
 Earthing of entire equipment to tap the energy from lighting and transfer it to the
ground to avoid flames coming up which may cause the flammable atmosphere to
explode.
 Precise selection of internal ignition engines which have to work in the zoned region
(Zheng, 2017, p. 259).
 Offering lightning protection to the electrical equipment.
 Efficient control over the use of regular vehicles. The regular which are not well
maintained can be a potential ignition source. The fumes which are released from the
exhaust pipes may contain sparks that can be able to ignite the flammable atmosphere.
 Efficient control over activities and process which create intermittent areas for
example tanker loading.
 Correct equipment selection to avoid high intensity electromagnetic radiations
sources.
 Doing away with use of matches, smoking or lighters.
 Control of repair activities which may source hot surfaces, sparks or naked fires.
 Elimination of the surface which is above the auto-ignition temperature of flammable
materials which are being handled.
Lightning protection
The process of protecting the electrical equipment from lightning includes the fitting of a
surge protection appliances amongst all of the non-earth bonded local structure and the core

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of the cable. The ignition which is produced by lightning can’t be dealt with completely
particularly with the existence of the detached roof tanks, where vapour is frequently
available at the rim seal (Starck, 2014, p. 472). In this situation, measures and precautions to
control the consequences of fire should be given.
Flammability Theory
As per Flammability Theory, which was established by Davy in the year 1816 tries to
develop thermal balance regarding flammability limits along with some specific concepts of
the flame temperature, while, according to flammability data has been reported in series. This
theory has been based on empirical rule of Le Chatelier, which first appeared within 1891. As
discussed by Conover (2014), as per these flammability data, auto ignition, burning rate and
flammability limits have been dealing with more than 200 vapours and combustible gases in
air along with other oxidants. These do predict same data regarding thousands of the other
combustible components and elements under varieties of the environmental conditions. With
development of the computer technologies, detailed and complete analysis is applied to
predict flammable behaviour. Moreover, engineering applications has still been relying on
empirical rule of Le Chatelier and modified law of Burgess-Wheeler for estimations.
Electrical equipment need to be designed, installed and specified in such a classified location
that need to be specially designed, tested for ensuring that it do not initiate any sort of
explosion.
The design and specification of the electrical equipment to be used in explosive atmosphere is
carried out by the electricians, engineers and other electrical workers who are usually
engaged in the design and fitting of electrical equipment in hazardous zones. They also do the
classification of the areas (Zheng, 2017, p. 374) .The hazardous agents have to be classified
with certain techniques and procedures which regard to the electrical equipment to be used.
3.0 Conclusion

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In conclusion, Flammable atmospheres can be caused by mist, vapour, combustible dusts and
flammable gases mixed with air. Then an ignition source is required to cause eruption.
Explosions are known to cause serious injuries and loss of life. Preventing the ignition of the
flammable atmospheres there is need to design and specify the usage of electrical equipment
in flammable atmosphere.
Contributions of electrical equipment to the explosions and fires in explosive atmosphere
include: Introduction of the electrical equipment for lighting and signalling has been
accompanied by explosions that are initiated electronically.
The ignition sources can be controlled through:
Earthing of all equipment that is aimed to tap the energy from lighting and transfer it to the
ground to avoid flames coming up which may cause the flammable atmosphere to explode.
Precise selection of internal ignition engines which have to work in the zoned area.
Offering lightning protection to the electrical equipment
Efficient control over the use of regular vehicles. The regular which are not well maintained
can be a potential ignition source. The fumes which are released from the exhaust pipes may
contain sparks which can ignite the flammable atmospheres.
4.0 References
Bender, H. F., 2017. Hazardous Chemicals: Control and Regulation in the European Market.
5th ed. London: John Wiley & Sons.

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Calixto, E., 2016. Gas and Oil Reliability Engineering: Modeling and Analysis. 5th ed.
Sydney: Gulf Professional Publishing.
Cheyne, D., 2016. Explosive Atmospheres, Part 28. 7th ed. Auckland: Standards New
Zealand.
Ching, J., 2016. Product Catalog. Translated English of Chinese Standard (All national
standards. 5th ed. Perth: https://www.chinesestandard.net.
Geoffrey Bottrill, 2015. Practical Electrical Equipment and Installations in Hazardous
Areas. th ed. Paris: Elsevier,.
Groh, H., 2017. Explosion Protection. 3rd ed. Sydney: revised.
Jespen, T., 2016. ATEX—Explosive Atmospheres: Risk Assessment, Control and Compliance.
1st ed. London: Springer.
Jones, P., 2010. Explosion Protection: Practical Understanding of Recent Standards and
New Legislation in Process Safety. 4th ed. Paris: IChemE,.
Kramer, C., 2011. Practical Engineer. 4th ed. London: Technical Publishing Company.
Lees, F., 2016. Lees' Loss Prevention in the Process Industries: Hazard Identification,
Assessment and Control. 2nd ed. Texas: Butterworth-Heinemann.
Starck, A. v., 2014. Handbook of Thermoprocessing Technologies: Fundamentals,
Processes, Components, Safety. 2nd ed. Chicago: Vulkan-Verlag GmbH,.
Zheng, W., 2017. GB 50058-2014: Translated English of Chinese Standard. GB50058-
2014.: Code for design of electrical installations in explosive atmospheres. 4th ed. Berlin:
https://www.chinesestandard.net.
http://www.hse.gov.uk/fireandexplosion/atex.htm#what
http://www.hse.gov.uk/comah/sragtech/techmeasareaclas.htm

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