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AUSTRALIAN ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS STANDARDS (GAS)

This is an updated version (Feb 2008) of a paper presented at a IICA seminar 'Power & Control Equipment in Hazardous Locations', Perth, 16-17Sep 1986. It is in my opinion a very useful guideline for working within the standards associated with electrical equipment in hazardous areas. ICEweb acknowledges the assistance and review of the document by Inlec Engineering. 

Introduction

This paper takes a practical approach to Australian Hazardous Area Standards taking the reader through them from conceptual design to maintenance. It does not cover dust hazards.

Australian Standards must be regarded as the PRIME Hazardous Area design guide in Australia. Some engineers are unnecessarily critical of the Standards, but these documents must be respected for what they are, namely information and advice dossiers which have been built up from design and practical experience over the years not only in Australia but from international sources (most Australian Standards have been based on the International Electrotechnical Commission [IEC] and the British Standards Institution [BSI] Standards).

Foreign Standards are not a substitute for Australian Standards. The only circumstances warranting the use of Foreign Standards is where the equipment is not available in an Australian certified form.  It should be noted that the use of foreign standards may require specific approval from an authority relevant to the particular industry.

AS/NZS3000-2007 -Electrical Installations - The Australian and New Zealand Wiring Rules is the most important Australian Standard pertaining to Electrical Installations in Hazardous Areas. Compliance with this Standard is mandatory under certain Federal and State Acts.

The Australian Standards can be of tremendous assistance to anyone involved in a Hazardous Area environment from engineers and technicians to fitters and process personnel. Admittedly they do have some limitations but which document doesn't.

In this paper some limitations of the Standards are detailed to foster awareness, however it is not intended to be derogatory to Standards Australia.

Hazardous dust atmospheres, although not part of the scope of this paper, are mentioned.

Standard Application
Use and Limitations

Design

Primarily the design engineering group must be in possession of the following

a) An adequate Scope of Work and process description

b) Process and Instrumentation diagrams (P & ID's)

c) Plant layouts and elevations

If these documents are not available design should not proceed.

This base documentation is utilised in conjunction with AS/NZS60079.10 CLASSIFICATION OF HAZARDOUS AREAS - Explosive Gas Atmospheres (Replaces AS2430.1) to determine the extent and degree of the hazard. 

The following definitions are important to remember, see Table 1.

NOTE: For the full definitions refer to the above Standard

Classification of Areas

Initial classification of the Hazardous Areas should be carried out by Process or Chemical Engineers as they are more familiar with the source/quantity of release, source or ignition, flashpoint, ignition temperature and plant operation concepts.

Competency for working with electrical equipment for hazardous areas is critical and there are several providers who undertake training and assessment in this area. 
These include: 
Inlec Engineering see:  http://www.inleceng.com/ 
Moxi Skill + Learning, see www.moxi.com.au/products.htm 

Courses and Assessment are based on the following standard:
AS/NZS4761 - Competency for working with electrical equipment for hazardous areas 
Part 1 - Competency Standards - Note updated June 2008 
Part 2 - Guide for Training and Assessment - Note updated June 2008 

MP 87:2004 : Australian/New Zealand Certification Scheme for explosion-protected electrical equipment (ANZEx Scheme) - Contains the basic rules and procedures for the management, administration and operation of the Australian/New Zealand Certification Scheme (ANZEx Scheme) for explosion-protected electrical equipment.

The " base" drawings utilised for the Hazardous Area drawings are usually the "to scale" plant layouts and elevations.

The engineer responsible for classification then classifies the plant area in accordance with the following standards. These Standards are only a guide and under no circumstances cover all plant concepts. They do however cover the most common ones. From these examples it is usually possible to deduce the Hazardous Area for an unusual portion of plant. In these circumstances it is important to document the reasons for determining a particular Hazardous Area.

Classification of Hazardous Areas - Liquids, Gases & Vapours
AS/NZS60079.10- Explosive Gas Atmospheres
AS/NZS2430.3.1- Examples of area classification - General
AS/NZS2430.3.2 - Examples of area classification - Vehicle workshops, vehicle parking, fuel dispensing stations and aircraft hangars
AS/NZS2430.3.3 - Examples of area classification - Flammable liquids Note amended August 2007
AS/NZS2430.3.4 - Examples of area classification - Flammable gases
AS/NZS2430.3.5 - Examples of area classification - Refineries and major processing plants
AS/NZS2430.3.6 - Examples of area classification - Laboratories, including fume cupboards and flammable medical agents
AS/NZS2430.3.7 - Examples of area classification - Landfill gas, sewage treatment and sewage pumping plants
AS/NZS2430.3.8 - Examples of area classification - Surface coatings and adhesives
AS/NZS2430.3.9 - Examples of area classification - Miscellaneous
AS/NZS60079.20 - Data for flammable gases and vapours

Hazardous Area drawings should detail the source of release, gas group and temperature class and show the Hazardous Area in "cross hatching" as shown in AS/NZS60079.10.

On completion of the initial Hazardous Area drawings the responsible Engineer should pass co-ordination prints to the Electrical, Instrumentation, Mechanical and Safety Engineers. These personnel are responsible for reviewing and checking the document in relation to their own discipline.

The final "Issued for Construction" drawing should then again be reviewed and signed by the responsible Engineer of all the pertinent disciplines.

Protection Concepts

On completion the Hazardous Area drawings are utilised by the Electrical/instrumentation Engineers for the system design along with AS/NZS2381.1 Electrical Equipment for Explosive Gas Atmospheres - selection, installation and maintenance.

It cannot be overemphasised that the person responsible for the Standard library within a company must inform the discipline engineers of any update or superseding of Standards. All too often engineers are left in the dark and are working to out of date Standards.

AS/NZS2381.1 "General Requirements" should be read first, this part along with the other parts relevant to the specific technique are applied in new installations, changes to existing installations whether permanent or temporary, and in maintaining equipment.

The Engineer after referencing the Hazardous Area drawings regarding location, zoning, gas groups and surface temperatures should select the equipment design according to the requirements of AS/NZS2381.1 . An important aspect of this is the comprehension of equipment labelling. (see Table 2).

TABLE 2

As an aid to selecting the particular equipment or Australian Standard for a certain zone the easy reference guide Table 3 can be utilised. The relevant Standard pertaining to the selected equipment should then be read.

Table 3

On selection of equipment the vendor should be requested to supply a copy of the relevant Certificate of Conformity PRIOR to orders being placed.
The responsible engineer should read the certificate for the following reasons:-

1. To ensure it is the correct document for the equipment, (all too often vendors supply incorrect certificates).

2. To comply with any "conditions of use" stated on the certificate. 

When the certification has been reviewed it should be filed for entry into the verification dossier. The engineer can then proceed with the circuit\system design in accordance with the equipment certificates and relevant Standards.

Verification Dossiers

It is essential that a verification dossier is prepared for all Hazardous Area installations. Included in this dossier should be:-

a. Hazardous Area drawings

b. Certification schedule

c. Equipment certificates

d The engineering calculations pertaining to Intrinsically Safe loops

e. Cable schedules and Cable routes

g. Special tests to be carried out upon Installation/Commissioning

h. Inspection report on installation

i. Periodic inspection reports.

The dossier must be updated during the life of the plant reflecting any changes which are implemented pertaining to the installation and equipment within the Hazardous Area.

The engineer responsible for the Hazardous Area drawings must be advised of any minor/major piping changes since these could result in changes to the Hazardous Area classification.
A full listing is available in AS2381.1 clause 1.6

Installation and Maintenance

AS/NZS3000 AUSTRALIAN AND NEW ZEALAND WIRING RULES and its associated Standards must be read at length and understood by the construction and maintenance engineers. Technicians and fitters should also be conversant with the requirements of the standard.

On a plant which is old or has been poorly maintained it is very important that the Company institutes an inspection to ensure compliance. In order to achieve this it will be necessary to have up to date Hazardous Area drawings and certification schedules. If these drawings are not available they should be produced.

The recommendations of the inspection report should be discussed with both maintenance, installation, design engineers and plant management.

Electrical staff should be fully conversant with and receive periodical updates in the principles of electrical equipment protection concepts. It is essential that personnel are aware of the certification limitations of test equipment since being portable this equipment is more likely to constitute a hazard in that it can be used in zones for which it is not certified.

Frictional Sparking Risks with Light Metals and their Alloys is very important and often misunderstood. This hazard is due to sparking when light metals and their alloys come into frictional contact with materials which are oxygen carriers, rust being the most common.

NO light metal alloy is permitted in a Zone 0 area. Fixed light metal alloy equipment is permitted in other zones subject to impact protection. Portable equipment of these materials is NOT permitted in Hazardous Areas unless equipment is otherwise protected (i.e. plastic coated or epoxy painted). A frequent breach of regulations can be seen with aluminium foil. aluminium scaffolding, aluminium sunshades, aluminium paint and the "old style" aluminium hard hats.

Inspection of Electrical Equipment prior to/during and periodically after installation is ESSENTIAL. AS2381 reflects the importance that the Standards Australia place on inspection with each of the sections detailing typical "Inspection" schedules. Generally these inspection schedules are combined into an overall schedule for the plant.

Inspection intervals should not exceed four years.

Limitations of Australian Standards

There are several notable areas which are not covered by Australian Standards these are-

(1) ANALYSER HOUSES

Analyser Houses have been in use for many years and to date no Australian Standard has been issued specifically referring to what can be a very hazardous environment. AS2380.4 (Pressurisation) instructs the user to refer to IEC 79-16 for analyser houses which details how to design these enclosures utilising ventilation concepts.

Although not a standard the document "Electrical Installations in Flammable Atmospheres" published by the Royal Society for the Prevention of Accidents has a very useful section on Analyser Houses.

(2) IGNITION FIRED GAS ENGINES

This is another complex subject which certainly merits inclusion in a Standard.

USEFUL REFERENCES

Selection, installation and maintenance guidelines for Ignition Systems used in Class 1, Group D, Division 2 locations on Internal Combustion Engines published by the American Gas Association

(3) GAS FIRED BOILERS IN INDUSTRIAL HAZARDOUS AREAS

There are no firm guidelines for the zoning of the above extremely confusing subject which causes great deal of "heartache" to many engineers. It is often difficult to zone an area where there may be for example, open flames protected by flame arrestors and high exhaust temperatures as a fundamental part of the apparatus.

Any engineer who believes that limitations exist in the Standards pertaining to the area in which he is working should first check with the Australian Standards catalogue of Standards Australia publications www.standards.org , ensuring that Standard on the subject has not been issued.

If no Australian Standard is available then other reference/foreign Standards should be sought. The proposed design should then be discussed and agreed upon by the responsible engineers. Any engineering decisions taken must be fully documented and included in the plant certification dossier.

Other Useful Standards and Handbooks

AS/NZS 2229 Fuel dispensing equipment for explosive atmospheres Note updated 31st August 2006

 AS/NZS 60079.28:  Protection of equipment and transmission systems using optical radiation 

Draft Standard DR 07330 CP Explosive atmospheres - Part 29.1: Gas detectors - Performance requirements

Draft Standard DR 07331 CP Explosive atmospheres - Part 29.2: Gas detectors - Selection, installation, use and maintenance

Electrical Equipment for Hazardous Areas Handbook HB2007 - from Standards Australia, the main objective of this updated handbook is to provide a basis for understanding the principles involved in the identification of a hazardous area, relevant statutory requirements and the selection and installation, maintenance, testing, overhaul and repair of appropriate electrical equipment. This handbook also provides a basic introduction to the relevant Australian, New Zealand, Joint (Australian/New Zealand) and International Standards dealing with hazardous areas.

Foreign Standards

It should not be generally required to refer to foreign Standards in association with new installations except in special circumstances which are detailed in the following Foreign Certification section. However on older installations it is quite likely that foreign, often American equipment, has been installed. It is therefore necessary to understand the labelling of this equipment to ensure its suitability for the zone in which it has been installed.

Comparisons of Standards are detailed in Tables 4,5 and 6. Care must be taken with these comparison tables detailed since although generally true some countries have gases/materials in different classes/groupings to others. Classification techniques also vary from country to country.

Table 4

Table 5

Table 6

TABLE 7

Foreign Certification

If available, equipment with Australian/International AUSEx/ANZEx or IECEx certification should be selected and installed in compliance with Australian Standards. To select foreign certified equipment on the basis of lower cost is false economy since documentation costs are likely to exceed any savings.

Sometimes however AUS/ANZ/IECEx certified equipment is not available and alternative equipment must be sought. 

Certification of electrical equipment for use in hazardous areas is mandatory due to legislation that calls up AS/NZS2381.1. 

AS/NZS2381.1-2005, Clauses 2.3 and 2.4.2 require that electrical equipment installed in hazardous areas be protected by a suitable explosion protection technique complying with either:

·        the relevant Australian Standard; or

·        the relevant IEC Standard

as detailed in Table 2.1 of AS/NZS2381.1-2005.

The Standard further states that, “Certified apparatus shall be used as it provides the necessary assurance that apparatus meets the requirements of the appropriate Standard.”   Acceptable certification shall be covered by a certificate of conformity issued in accordance with:

·        the ANZEx scheme

·        the IECEx scheme

·        or another Type 5 scheme complying with ISO/IEC Guide 67, and meeting the requirements contained in AS/NZS2381.1 App. G.

Certificates under the AUSEx scheme are still valid.

Thus it is the certificate of conformity issued in accordance with the ANZEx, AUSEx or IECEx scheme, which determines the acceptability of electrical equipment for installation in hazardous areas. 

‘Other’ Ex Certification/Approval Systems

In circumstances when the user needs to use ATEX, FM, CSA, UL or other Ex equipment not certified to the ANZEx/AUSEx or IECEx schemes, the equipment and its installation must provide an equivalent level of safety to the ANZEx/AUSEx or IECEx schemes, and the user must obtain a Conformity Assessment document (CAD).  The CAD provides evidence that a certificate of conformity to an alternative standard can be demonstrated to provide an equivalent level of safety to AS/NZS or IEC Standards. This normally requires a comparison of the relevant standards and verification that testing has been conducted by a third party. The legal owner must provide justification for the use of the equipment and document the acceptance in the dossier.  In some instances, there may be additional legislated requirements for acceptance of apparatus certified to alternative standards.

Conclusion

The Australian Standards are important reference documents for personnel involved in any way with electrical equipment in Hazardous Areas.

References

[1] Garside: Intrinsically Safe Instrumentation - A Guide", published by Safety Technology Ltd, UK, 1982.
[2] H.G. Bass: "Intrinsic Safety", published by Quatermaine House Ltd, UK, 1984.
[3] SIRA Ltd: "Safety of Electrical Instrumentation in Potentially Explosive Atmospheres", unpublished course notes.
[4] ROSPA: "Electrical Installation in Flammable Atmospheres",published by ROSPA, UK, 1972.
[5] A.P.l. recommended practice RP500A, B and C.
A.G.A. Selection, Installation and Maintenance Guidelines for Ignition Systems Used in Class 1, Group D, Division 2 Locations on Internal Combustion, Spark Ignited Gas Engines. CPR-85-4-1
[6] Explosion Protection Technology website http://www.eptech.com.au 

Other Useful Information

Abridged course notes from Inlec Engineering 

The following information is courtesy of DCA Intrinsically safe products http://www.dcaexpro.com/index.html

Some reference material from the Australian Standards Handbook HB13-2000.
Includes: Labelling and Marking, Minimum Ignition Energy, What are Zone
Classifications?, Temperature (T) Rating, Conformity Assessment.

Where are Australian Standards at today?

List of Current Hazardous Area Australian Standards - From Explosion Protection Technology http://www.eptech.com.au