NZQA registered unit standard
26739 version 1
Page 1 of 10
Title
Demonstrate introductory underpinning knowledge of electrical
apparatus in explosive atmospheres
Level
4
Purpose
Credits
5
This unit standard covers the essential underpinning
knowledge for people working with or intending to work with
electrical apparatus in explosive atmospheres.
People credited with this unit standard are able to demonstrate
knowledge of:
 explosive atmospheres and explosion-protection principles;
 the principles of explosion-protection techniques;
 the characteristics and application of the flameproof Ex d
explosion-protection technique;
 the characteristics and application of the increased safety
Ex e explosion-protection technique;
 the characteristics and application of the non-sparking Ex n
explosion-protection technique;
 the characteristics and application of intrinsic safety Ex i and
Ex iD explosion-protection techniques;
 the characteristics and application of pressurisation Ex p and
Ex pD explosion-protection techniques;
 the characteristics and application of the enclosures for
dusts Ex tD explosion-protection technique; and
 the common characteristics of explosion-protection
techniques; and
 ex certification schemes.
Classification
Explosive Atmospheres > Electrical Apparatus in Explosive
Atmospheres - Operations
Available grade
Achieved
Explanatory notes
1
This unit standard has been designed for training and assessment off-job.
2
References
AS/NZS 1768:2007, Lightning protection;
AS/NZS 3000:2007, Electrical installations (known as the Australian/New Zealand
Wiring Rules);
AS/NZS 4761.1:2008, Competencies for working with electrical equipment for
hazardous areas (EEHA) Part 1 – Competency standards;
AS/NZS 4761.2:2008, Competencies for working with electrical equipment for
hazardous areas (EEHA) Part 2 – Guide to assessing competency;
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NZQA registered unit standard
26739 version 1
Page 2 of 10
AS/NZS 60079.0:2008, Explosive atmospheres –Equipment – General requirements;
AS/NZS 60079.10.1:2009, Explosive atmospheres – Classification of areas –
Explosive gas atmospheres;
AS/NZS 60079.14:2009, Explosive atmospheres – Electrical installations design,
selection and erection;
AS/NZS 60079.17:2009, Explosive atmospheres – Electrical installations inspection
and maintenance;
AS/NZS 60079.29.2:2008, Explosive atmospheres – Gas detectors – Selection,
installation, use and maintenance of detectors for flammable gases and oxygen;
AS/NZS 61241.0:2005, Electrical apparatus for use in the presence of combustible
dust – General requirements;
AS/NZS 61241.2.1:2000, Electrical apparatus for use in the presence of combustible
dust – Test methods – Methods for determining the minimum ignition temperature of
dust;
AS/NZS 61241.10:2005, Electrical apparatus for use in the presence of combustible
dust – Classification of areas where combustible dusts are or may be present;
AS/NZS 61241.14:2005, Electrical apparatus for use in the presence of combustible
dust – Selection and installation;
Electricity Act 1992;
Electricity (Safety) Regulations 2010;
Hazardous Substances and New Organisms Act 1996;
Health and Safety in Employment Act 1992, and associated regulations;
and their subsequent amendments and replacements.
3
Definitions
ANZEx – Australian/New Zealand Certification Scheme for explosion-protected
electrical apparatus (ANZEx Scheme).
Apparatus group – Group I is for apparatus for coal mines. Group II is for gases and
vapours in surface industries, and is divided into Groups IIA, IIB and IIC for
substances with increasing ease of ignition. Group III is for dusts in surface
industries, and is similarly divided into Groups IIIA, IIIB and IIIC. These are added as
roman number suffixes to explosion-protection technique markings on apparatus and
on Certificates of Compliance.
ATEX – Appareils destinés à être utilisés en Atmosphères Explosibles, comprises
two European Union directives (Directive 94/9/EC) that describe what apparatus,
protective systems, and work that is permitted in potentially explosive atmospheres.
Explosion-protection techniques – techniques applied to the design of electrical
apparatus, components, and systems to prevent the electrical energy from becoming
an ignition source in the presence of flammable vapours and gases or combustible
dusts in explosive atmospheres. See explosion-protected apparatus.
Explosion-protected apparatus – electrical apparatus to which specific measures are
applied to avoid ignition of a surrounding explosive atmosphere. Such apparatus
employs one or more of the following explosion-protection techniques:
For gas and vapour atmospheres
Ex d – flameproof;
Ex e – increased safety;
Ex i – intrinsic safety; with levels of protection Ex ia, Ex ib and Ex ic;
Ex n – non-sparking;
For dusts
Ex iD – intrinsic safety (dusts);
Ex tD – enclosed;
Others, less common
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NZQA registered unit standard
26739 version 1
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Ex p – pressurisation; Ex pD (dust);
Ex m – encapsulation, with levels of protection Ex ma, Ex mb, Ex mc (gases and
vapours), and Ex mD (dusts);
Ex s – special protection; categorised by Zone of application; e.g. ‘Ex s
(Zone 0);
Ex o – oil immersion;
Ex q – sand filled;
Ex v – ventilation.
The term apparatus includes equipment, as mentioned in many relevant Standards.
Explosive atmosphere – an atmosphere comprising volatile substances mixed with
air under atmospheric conditions in the form of gases, vapours, mist, dust or flyings in
which, after ignition has occurred, combustion spreads to the entire unburned
mixture.
Hazardous area – area in which an explosive atmosphere is present or may be
expected to be present in duration and/or frequency such as to require special
precautions for the construction, installation, and use of apparatus.
Hot work permit – permit allowing tools to be taken into, and work to be carried out in,
a hazardous area.
IECEx – International Electrotechnical Commission certification scheme covering
product that meets the requirements of International Standards.
LEL – lower explosive limit. Concentration of flammable gas or vapour in air, below
which, an explosive gas atmosphere will not be formed.
Mixed explosion-protection – apparatus that comprises several components, each
with its own explosion-protection technique, contained within the one enclosure.
Temperature class – classification system of electrical apparatus, based on its
maximum surface temperature, related to the specific explosive atmosphere for
which it is intended to be used.
UEL – upper explosive limit. Concentration of flammable gas or vapour in air, above
which, an explosive gas atmosphere will not be formed.
4
Range
a Assessment is to take account of variations between the industry sectors and
enterprises. For example, apparatus used in underground coal mining will be
different in some respects from that used in a petrochemical plant.
b All activities and evidence presented for all outcomes and evidence requirements
in this unit standard must be in accordance with safe working principles and
practices, legislation, policies, procedures, ethical codes and Standards, safe and
sound practice, and industry practice; and, where appropriate, manufacturers’
instructions, specifications, and data sheets.
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of explosive atmospheres and explosion-protection principles.
Evidence requirements
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1.1
26739 version 1
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Properties of combustible substances and their potential to create an explosive
hazard are explained.
Range
conditions that will lead to an explosion, explosive range of
substances including LEL and UEL, flashpoint.
1.2
The terms combustion, ignition, and propagation are explained.
1.3
Explosive parameters of substances, as given in tables of substance
characteristics, are described in terms of the properties of combustible
materials.
Range
materials include – gases, vapours from liquids, dusts;
properties include – flash points of liquids, LEL and UEL of gases.
1.4
The toxic nature of gases, vapours and dusts, and their potential harmful
consequences are described.
1.5
The nature of hazardous areas is described.
Range
Standards definitions of hazardous areas, explosive atmospheres,
apparatus groups, temperature classes and their relationship to
the substances present;
the concept of zones in terms of likelihood or frequency and
duration of the presence of an explosive atmosphere in that
location;
the need for zone classification by specialists using Standards.
1.6
Methods of achieving explosion-protection are described in terms of energy
limitation, exclusion, containment, dilution, and elimination of ignition source.
1.7
Occupational Safety and Health (OSH) responsibilities related to hazardous
areas are described.
Range
the main features and purpose of a clearance to work system
including hot work permit systems, safety procedures to be
followed before entering a hazardous area.
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1.8
26739 version 1
Page 5 of 10
The roles and responsibilities of the parties involved in the safety of hazardous
areas are described.
Range
Acts and regulations related to the safety of hazardous areas and
the authorities responsible for their implementation;
where assistance and further information can be obtained to help
persons with hazardous areas responsibilities;
the hazardous areas responsibilities of the owner of premises, and
of the occupier of premises;
enterprises and personnel engaged in classification, installation,
maintenance, design, overhaul and/or modification, assessment,
and inspection of explosion-protection systems and/or
installations;
manufacturers of explosion-protected apparatus;
designated authorities.
Outcome 2
Demonstrate knowledge of the principles of explosion-protection techniques.
Range
Ex d, Ex e, Ex n, Ex nA, Ex nC, Ex nL, Ex nR, Ex i, Ex ia, Ex ib, Ex iD, Ex p, Ex
pD, Ex v, Ex s, Ex o, Ex q, Ex tD, Ex m, Ex ma, Ex mb, Ex mD.
Evidence requirements
2.1
The principles of each explosion-protection technique, the methods used to
achieve the protection, and how each technique works are explained.
2.2
Visible conditions or actions that would void the explosion-protection provided
by each technique are explained.
Outcome 3
Demonstrate knowledge of the characteristics and application of the flameproof Ex d
explosion-protection technique.
Evidence requirements
3.1
The purpose and characteristics of the design features of apparatus and circuits
protected by the flameproof Ex d technique are described.
Range
characteristics of design features include but are not limited to –
flame paths, integrity under pressure, pressure piling, enclosure
entries.
3.2
Situations where the flameproof Ex d technique can be used are identified.
3.3
Actions or conditions that would void the protection provided by the flameproof
Ex d technique are described.
3.4
Use of Standards to determine the requirements with which the installation of
the flameproof Ex d explosion-protected apparatus must comply are explained.
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NZQA registered unit standard
26739 version 1
Page 6 of 10
Outcome 4
Demonstrate knowledge of the characteristics and application of the increased safety Ex e
explosion-protection technique.
Evidence requirements
4.1
The purpose and characteristics of the design features of apparatus and circuits
protected by the increased safety Ex e technique are described.
Range
characteristics of design features include but are not limited to –
temperature rise, maximum power dissipation, protection devices,
certified components, creepage, clearance distances, absence of
sparking contacts, enclosure entries.
4.2
Situations where the increased safety Ex e technique can be used are
identified.
4.3
Actions or conditions that would void the protection provided by the increased
safety Ex e technique are described.
4.4
Use of Standards to determine the requirements to which the installation of the
increased safety Ex e explosion-protected apparatus is to comply are explained.
Outcome 5
Demonstrate knowledge of the characteristics and application of the non-sparking Ex n
explosion-protection technique.
Evidence requirements
5.1
The purpose and characteristics of the design features of apparatus and circuits
protected by the non-sparking Ex n technique are described.
Range
characteristics of design features include but are not limited to –
creepage, clearance distances, restricted breathing.
5.2
Typical situations where the non-sparking Ex n explosion-protection technique
is used are identified.
5.3
Actions or conditions that would void the protection provided by the nonsparking Ex n technique are described.
5.4
Use of Standards to determine the requirements to which the installation of the
non-sparking Ex n explosion-protected apparatus is to comply are explained.
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NZQA registered unit standard
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Page 7 of 10
Outcome 6
Demonstrate knowledge of the characteristics and application of intrinsic safety Ex i and
Ex iD explosion-protection techniques.
Evidence requirements
6.1
The purpose and characteristics of the design features of apparatus and circuits
protected by intrinsic safety Ex i and Ex iD techniques are described.
Range
characteristics of design features include but are not limited to –
field devices, cables, safe area devices, earthing, entity versus
integrated system concept, simple devices and interface devices
and their parameters, segregation, infallible components, current
and voltage limiting, creepage, clearance distances.
6.2
Typical situations where intrinsic safety Ex i and Ex iD techniques are used are
identified.
6.3
Actions or conditions that would void the protection provided by intrinsic safety
Ex i and Ex iD techniques are described.
6.4
Use of Standards to determine the requirements to which the installation of
intrinsic safety Ex i and Ex iD techniques explosion-protected apparatus is to
comply are explained.
Outcome 7
Demonstrate knowledge of the characteristics and application of pressurisation Ex p and
Ex pD explosion-protection techniques.
Evidence requirements
7.1
The purpose and characteristics of the design features of apparatus and circuits
protected by pressurisation Ex p and Ex pD techniques are described.
Range
characteristics of design features include but are not limited to –
exclusion and dilution, purge periods, controlled shut down,
monitoring, sources of internal release.
7.2
Typical situations where pressurisation Ex p and Ex pD techniques are used are
identified.
7.3
Actions or conditions that would void the protection provided by pressurisation
Ex p and Ex pD techniques are described.
7.4
Use of Standards to determine the requirements to which the installation of
pressurisation Ex p and Ex pD techniques explosion-protected apparatus is to
comply are explained.
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26739 version 1
Page 8 of 10
Outcome 8
Demonstrate knowledge of the characteristics and application of the enclosures for dusts
Ex tD explosion-protection technique.
Evidence requirements
8.1
The purpose and characteristics of the design features of apparatus and circuits
protected by the technique for dusts, Ex tD, are described.
Range
characteristics of design features include but are not limited to –
enclosures, pressurisation, encapsulation, intrinsic safety.
8.2
Typical situations where the dust explosion-protection technique, Ex tD, is used
are identified.
8.3
Actions or conditions that would void the protection provided by dust explosionprotection technique, Ex tD, are described.
8.4
Use of Standards to determine the requirements to which the installation of
dust, Ex tD, explosion-protected apparatus is to comply are explained.
Outcome 9
Demonstrate knowledge of the common characteristics of explosion-protection techniques.
Evidence requirements
9.1
The purposes of temperature classification, apparatus grouping, cloud and layer
temperature, and ingress protection are identified and described.
9.2
Limitations of non-metallic or specific alloy enclosures are described.
9.3
Environmental conditions that may impact on explosion-protection techniques
are identified and described.
9.4
The principles and applications of other and mixed explosion-protection
techniques are explained.
Range
9.5
Ex m, Ex o, Ex q, Ex v, Ex s.
Features and purpose of conduit seals and cable termination devices are
identified and described.
Range
conduit seals and barrier and compression glands for cables with
or without armouring, screening and/or drain wires.
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26739 version 1
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Outcome 10
Demonstrate knowledge of Ex certification schemes.
Evidence requirements
10.1
Purpose and scope of certification schemes are explained.
10.2
The schemes accepted in Australia and New Zealand are identified.
10.3
Schemes commonly used in countries other than Australia and New Zealand
are identified.
10.4
Processes for having apparatus certified under the accepted Australia and New
Zealand Ex schemes are described.
Range
10.5
scheme procedures, quality management requirements,
conformance testing and assessment, on-going certification
requirements.
The purpose and use of conformity and certification for apparatus used in
explosive atmospheres are described.
Range
ATEX, ANZEx, IECEx.
Planned review date
31 December 2016
Status information and last date for assessment for superseded versions
Process
Version Date
Last Date for Assessment
Registration
1
20 May 2011
N/A
Consent and Moderation Requirements (CMR) reference
0003
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA,
before they can report credits from assessment against unit standards or deliver courses
of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by
NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and
which are assessing against unit standards must engage with the moderation system that
applies to those standards.
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NZQA registered unit standard
26739 version 1
Page 10 of 10
Requirements for consent to assess and an outline of the moderation system that applies
to this standard are outlined in the Consent and Moderation Requirements (CMRs). The
CMR also includes useful information about special requirements for organisations wishing
to develop education and training programmes, such as minimum qualifications for tutors
and assessors, and special resource requirements.
Comments on this unit standard
Please contact the ElectroTechnology Industry Training Organisation (ETITO)
reviewcomments@etito.co.nz if you wish to suggest changes to the content of this unit
standard.
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