HB239

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Handbook

Guidance on the repair and overhaul of

electrical equipment for explosive

atmospheres

H B 239 :201 1

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HB 239:2011

This Joint Australian/New Zealand Handbook was prepared by Joint Technical Committee EL-023, Electrical Equipment in Mines. It was approved on behalf of the Council of Standards Australia on 8 December 2010 and on behalf of the Council of Standards New Zealand on 1 July 2011.

This Handbook was published on 19 July 2011.

The following are represented on Committee EL-023: Australian Chamber of Commerce and Industry Australian Coal Association

Australian Industry Group Consult Australia

Department of Industry and Investment NSW Department of Mines & Petroleum (WA) Department of Mines and Energy (Qld) Electrical Apparatus Service Association

Mining Electrical and Mining Mechanical Engineering Society National Association of Testing Authorities Australia

Queensland Department of Environment and Resource Management Solid Energy New Zealand

The Aviation and Marine Engineers Association University of Newcastle

WorkCover New South Wales

Keeping Standards up-to-date

Standards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments which may have been published since the Standard was purchased.

Detailed information about joint Australian/New Zealand Standards can be found by visiting the Standards Web Shop at www.saiglobal.com.au or Standards New Zealand web site at www.standards.co.nz and looking up the relevant Standard in the on-line catalogue.

For more frequent listings or notification of revisions, amendments and withdrawals, Standards Australia and Standards New Zealand offer a number of update options. For information about these services, users should contact their respective national Standards organization.

We also welcome suggestions for improvement in our Standards, and especially encourage readers to notify us immediately of any apparent inaccuracies or ambiguities. Please address your comments to the Chief Executive of either Standards Australia or Standards New Zealand at the address shown on the back cover.

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Handbook

Guidance on the repair and overhaul of

electrical equipment for explosive

atmospheres

COPYRIGHT

All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher, unless otherwise permitted under the Copyright Act 1968 (Australia) or the Copyright Act 1994 (New Zealand).

Jointly published by SAI Global Limited under licence from Standards Australia Limited, GPO Box 476, Sydney, NSW 2001 and by Standards New Zealand, Private Bag 2439, Wellington 6140.

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PREFACE

This Handbook was prepared by Standards Australia/Standards New Zealand Committee EL-023, Electrical Equipment in Mines.

The objective of this Handbook is to provide practical guidance for the overhaul and repair of electrical equipment for explosive atmospheres. It contains performance-based information on process and procedures that have been part of AS/NZS 3800 that may not transfer to the revised 2011 version IEC 60079.19, the recognised international Standard for the repair and overhaul of explosion-protected electrical equipment. Additionally, information on the key processes for the repair of reeling and trailing cable is included. The Handbook offers additional guidance regarding techniques and special processes necessary to ensure consistent and reliable delivery of repaired and overhauled equipment and cables. Also included are appendices covering quality management systems, measurement and calibration, and history of equipment and service facilities approval schemes.

The Handbook has been written to assist repair facilities, owners and operators of electrical equipment in explosive atmospheres.

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STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND

Handbook

Guidance on the repair and overhaul of electrical equipment for

explosive atmospheres

S E C T I O N 1 G E N E R A L

1.1 SCOPE

This Handbook provides guidance for the repair and overhaul of explosion-protected electrical equipment used in hazardous areas (defined in AS/NZS 60079.0).

The Handbook covers equipment with a Group I designation for coal mining; Group II where flammable gases and vapours may be present; and Group III which includes equipment used in the presence of combustible dusts.

This Handbook details the methods of overhaul, repair, examination and the testing required to ensure safety and compliance with the relevant Standards for the different equipment explosion-protection techniques. It covers the several types of explosion-protection techniques currently in use and provides guidance for repair and overhaul service facilities. The soon to be published revision of AS/NZS 3800 (and IEC 60079-19 Edition 3) offer a performance-based approach to the overhaul of electrical equipment for use in hazardous areas. In many applications it was felt it was necessary to establish guidance to standardise the approach for inspection, repair and overhaul techniques and methods, and to provide a repository where expert knowledge can be accumulated from experience and disseminated for the benefit of stakeholders.

The objective of this Handbook is to provide service facilities, equipment owner and/or operators and relevant regulatory authorities involved in the repair and overhaul of electrical equipment in hazardous areas with guidance to ensure safety and compliance with the relevant existing Standards.

The Handbook also offers additional guidance on techniques and special processes necessary to ensure consistent and reliable delivery of repaired and overhauled equipment and cables.

This document is to be read initially in conjunction with AS/NZS 3800 and IEC 60079-19 Edition 3, the recognized international Standard for repair and overhaul of explosion-protected electrical equipment. In anticipation of the soon-to-be published revised AS/NZS 3800 (and IEC 60079 Edition 3), where possible, reference to these documents has been quoted throughout the text.

1.2 REFERENCED DOCUMENTS AS/NZS

1299 Electrical equipment for coal mines—Flameproof restrained plugs and receptacles

1300 Electrical equipment for coal mines—Bolted flameproof cable coupling devices 1747 Reeling, trailing and feeder cables used for mining—Repair, testing and fitting

of accessories

1802 Electric cables—Reeling and trailing—For underground coal mining 1972 Electric cables—Underground coal mines—Other than reeling and trailing

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AS/NZS

2081 Electrical equipment for coal and shale mines—Electrical protection devices (series)

2290 Electrical equipment for coal mines—Maintenance and inspection (series) 2381 Electrical equipment for explosive atmospheres—Selection, installation and

maintenance

2802 Electric cables-Reeling and trailing-for mining and general use (other than underground coal mining)

3800 Electrical equipment for explosive atmospheres—Repair and overhaul

4761 Competencies for working with electrical equipment for hazardous areas (series)

4871 Electrical equipment for coal mines, for use underground (series) 60079 Explosive atmospheres (series)

61241 Electrical apparatus for use in the presence of combustible dust (series) 62013 Caplights for use in mines susceptible to firedamp (series)

AS/NZS ISO

9001 Quality management systems AS

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S E C T I O N 2 D E F I N I T I O N S

2.1 GENERAL

The Definitions in the standards listed in Referenced Documents apply to this document. 2.2 ADDITIONAL DEFINITIONS

The following definitions also apply. 2.2.1 Verification Dossier

A set of documents showing the compliance of electrical equipment and installations, including certificates, manufacturer instructions, records of previous repairs, overhaul and reclamation.

2.2.2 Metal spray (also known as thermal spray)

A coating deposition technique in which melted droplets of material are sprayed onto a substrate material. The resulting coating is comprised of small pancake-like ‘splats’, often with voids and incomplete bonding. The technique allows deposition of materials dissimilar to the substrate and does not heat the substrate, but requires controlled application to ensure consistency of material and bonding.

2.2.3 Laser welding

A metal joining technique using lasers to generate the melt heat and precisely deposit material at the required location. Laser welding offers control and high power input, reducing the size of the heat affected zones around the welds.

2.2.4 Solder

Solder is metal alloy with a low melting point used to join materials through melting and physical keying onto the surface while cooling. Traditionally, solders were tin-lead alloys. However, environmental concerns with lead have seen restrictions on the use of lead in electrical and electronic equipment. As a consequence many recent solders have been formulated to be lead-free alloys. Many different lead-free formulations exist and these may not be compatible with each other. In addition, over time some lead-free solders have grown metallic (tin) whiskers, which in some instances have affected clearance distances in Ex ‘i’ equipment.

2.2.5 Controlled temperature burn-out

Removal of insulating materials (commonly varnishes, plastics and epoxy in windings) by heating. Temperatures are selected to melt and oxidise the insulating materials without comprising the magnetic properties or interlamination insulation of the iron core.

2.2.6 Final inspection

The last inspection of an item while under the control or responsibility of the inspecting body.

2.2.7 Competent person

Refer to AS/NZS 3800. A person who can demonstrate a combination of knowledge and skills to effectively, efficiently and safely carry out activities in hazardous areas covered by AS/NZS 4761. Competency in some cases may be limited to one or more specific types of protection techniques, e.g. Ex ‘d’, Ex ‘i’, and or activity (e.g. design, selection, installation, maintenance, testing and inspection). A competent person may also be referred to as a responsible person.

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2.2.8 Special processes

Processes that cannot be fully verified by test, therefore requiring adherence to specific procedures to ensure tasks fulfil the processes satisfactorily.

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S E C T I O N 3 T E C H N I C A L P R I N C I P L E S A N D

P R O C E S S E S

3.1 INTRODUCTION

This Section describes aspects of the technical infrastructure of relevance to the repair and overhaul of Ex equipment, and the general processes of overhaul. Particular emphasis is placed on competencies, access to information (covering both documentation and post-repair marking of equipment) and the planning of workflow. Central to the efficient and effective delivery of overhauls and repaired equipment are relationships with significant stakeholders, such as the equipment owner, user and possibly the designer and manufacturer.

3.2 BACKGROUND

Explosion-protected equipment and high integrity reeling and trailing cables are essential risk controls for the safe use of electricity within a hazardous area. Certified and approved explosion-protected equipment have passed rigorous compliance reviews of the original equipment design. The more recent (Type 5) certification schemes also include quality audits of the equipment manufacture. These programs aid to improve the compliance level of hazardous area equipment, while regular inspections and maintenance by the owner or operator assist to maintain the equipment in its ‘as built’ condition.

No item of engineered equipment can last indefinitely and it is generally acknowledged that failure of an explosion-protection technique is not ‘self-revealing’. In order to verify the continued integrity of the equipment, periodic overhaul of electrical equipment situated in hazardous areas is recommended to verify the integrity of the equipment safeguards.

Hazardous areas are defined in AS/NZS 60079.0 as follows: ‘In underground coal mines, hazardous areas are termed hazardous zones and are generally geographically defined in legislation. In operating areas the hazardous zone is considered to be zone 1 while ever ventilation is effective. However, on the loss of ventilation the hazardous zone is often considered to be zone 0. There are hazardous zones in mines that are not accessible to people, but which are considered to be zone 0.’

Because equipment usage affects its explosion-protection properties, the equipment is regularly removed from service and overhauled, as timetabled in AS/NZS 2290.1 for Group I applications. In Group II and III applications there is no published timetable for overhaul, and the equipment may be overhauled either periodically or on an as-needs basis.

3.3 COMPETENCIES

Inspection, repair and the verification of compliance after overhaul of explosion-protected electrical equipment requires specialist knowledge and experience not generally achieved in general industrial equipment overhaul. AS/NZS 4761 details competency requirements for hazardous area equipment work, but these competencies should only be considered a starting point; experience working on the types of equipment overhauled is essential. Incorrect actions and/or conformity evaluation may impair or incorrectly diagnose the subsequent explosion-protected properties of that equipment. Therefore all work and verification activities should be performed by, or under the supervision of, a person who has a recognised competency for the particular explosion-protection technique. This person is often termed a ‘competent person’.

Effective overhauls sometimes require use of specialist processes such as welding, metal spraying and non-destructive testing. It may not be possible for the overhaul workshop to possess the facilities or competencies for all techniques used in any particular overhaul, and

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it is common for these type of services to be subcontracted to specialist providers. Often, these specialist processes are supported by industry-based competence schemes that recognise individuals or approved suppliers. Whether these specialist processes are provided in-house or outsourced, the competent person should be aware of the presence and relevance of such schemes. They should take steps to ensure that operatives, who are engaged in all actions and processes that may affect the Ex properties of the equipment under overhaul, are appropriately skilled in the processes employed. Records supporting these steps should be kept, either as skills matrices for staff performing specialist tasks in-house, or as part of the sub-contractor evaluation process.

3.4 SERVICE FACILITY RELATIONSHIPS WITH THE

EXPLOSION-PROTECTED EQUIPMENT OWNER/OPERATOR

The repair and overhaul of equipment requires effective communication among a number of parties who have interests in the equipment. These can include the owner, the operator and the repair facility. These are explained in further detail below:

(a) The equipment owner is the specifier and provider of instruction information.

(b) The operator typically has day-to-day involvement in using the equipment and may, through that involvement, identify issues demanding attention.

(c) The combination of owner/operator and Service Facility are typically responsible for identifying a suitable scope of work for equipment repair or overhaul and agreeing to any associated variations. Responsibilities between the owner/operator and Service facility are normally established through contractual relationships outside the scope of this document.

Facilities involved in repair and overhaul should consult with all parties to attempt to confirm that dossiers are maintained and reflect the current (rather than as-provided) status of the equipment.

Clear communication ensures that—

(i) there is a holistic approach to the safety of the affected hazardous area installation (rather than a focus on individual items of equipment);

(ii) documentation associated with the equipment is available and reflects the compliance status of equipment;

(iii) problems identified within the equipment are addressed; (iv) necessary or desired upgrades are included;

(v) options in the repair process are discussed and agreed on; (vii) the compliance status of returned equipment is clearly agreed; (viii) there is a timely delivery of post-overhaul documentation; and (ix) post-contractual disputes are minimised.

Consultation regarding the equipment verification dossier may highlight issues in the history of the equipment, recurrent or known failure modes, or environmental deficiencies that are relevant to the repair and overhaul of the equipment.

In some cases, clients may ask the repair and overhaul facility not to proceed with some elements of the overhaul activity. In these cases there should be a clearly agreed scope of work. It is acknowledged that clients may employ alternative means of establishing explosion-protection; the omission of operations mandated in AS/NZS 3800 should be clearly justified and identified in post-overhaul documentation. Repair facilities should be careful in the assertion of compliance in such cases.

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3.5 CONSULTATION WITH OTHER PARTIES: MANUFACTURERS AND REGULATORS

Other parties may provide information relevant to equipment overhaul and repair. Manufacturers, certification bodies and regulators may issue post-manufacture information updates or safety alerts.

Facilities involved in the overhaul and repair of Ex equipment should be aware of the possible issue of additional information and ask for relevant information to be provided by the owner or operator. Normally this type of information is included in the relevant verification dossier.

3.6 DOCUMENTATION—VERIFICATION DOSSIER

It is not unusual for a service facility to receive electrical explosion-protected equipment from an owner /operator with little to no information on the history of repair and overhaul, or known deficiencies within the delivered equipment. Therefore, it is important for the service facility to seek the necessary verification dossier and owner/operator’s instructions and guidance before proceeding.

All hazardous area installations are required to have a verification dossier in accordance with AS/NZS 60079.14, which is mandated by AS/NZS 3000. For Group I, hazardous areas are typically predefined and the verification dossiers are established for individual explosion-protected plant items. Information normally available on the supply of equipment forms the basis for a dossier, which is kept up-to-date by the owner/operator so that the dossier reflects the current compliance status and service history of the equipment. (The implementation of this may vary between clients and industries and with the age of the installation.)

Equipment certification regimes may affect the information available. Appendix D offers additional information on a range of equipment approval and certification systems currently in use in Australia. Recent obligations cited in the IEC Ex certification scheme include manufacturer’s information regardless of the Ex equipment Group. Some older equipment may only have been evaluated for compliance with national or international Standards and issued with a Certificate of Conformity attesting to the validity of the explosion-protection characteristics of the equipment. Other older equipment may only have regulatory approval. Approved equipment will generally be compliant with the national Standards at the date of issue, however alternative risk controls that were deemed equivalent were sometimes approved.

In fact, compliance to Standards is a minimum requirement for certification and equipment may be designed and certified using more stringent specifications than those detailed in Standards.

For these reasons a service facility should review the compliance specifications prior to repair or overhaul. In all cases, the preferred approach to overhaul is to refer to certification or approval documentation, including the drawings that identify the explosion-protected features of the equipment.

In the event that the owner/operator cannot provide the verification dossier the workshop may be able to assist in gathering the relevant information.

As previously mentioned, Group I equipment has a strong history of evaluating the suitability and compliance of explosion-protected equipment prior to use in a hazardous area, and has insisted that compliance documentation, including drawings, are maintained and used for the purposes of repair and overhaul to verify that the explosion-protected characteristics of the equipment are maintained as originally evaluated.

Groups II and III do not have the same strong history of evaluation and maintenance of documentation and therefore could use an alternative approach. In circumstances where

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certificate documents are not available, then a service facility should liaise with the owner/operator who may elect to initiate the repair or overhaul of the explosion-protected equipment to achieve compliance with the relevant Standards. However, the more recent certification/approval scheme makes the provision of compliance documentation mandatory with the supply of the equipment (refer to AS/NZS 60079.0 Clause 30, ‘Instructions’). In instances of legacy equipment without compliance documents, steps taken to obtain the certificate documents should be recorded in the repair facility records. Figure 3.1 provides a flowchart as a guide to assist in determining whether a particular piece of explosion-protected electrical equipment can be satisfactorily repaired or needs to be replaced.

Clearly, there are issues for service facilities (workshops) in establishing that they have all relevant documentation when overhauling legacy equipment, but there are also issues when overhauling recently-issued equipment. Recently-issued equipment will be accompanied by a comprehensive verification dossier, however, it is possible mine management practice is to hold multiple copies of the dossier. While the verification dossier is supposed to include details of maintenance and inspections performed over the operating life of the equipment, it is possible that all of this information is not present in the copy of the dossier provided to the service facility. Efforts should be made to confirm that the dossiers provided to the service facility include all relevant information, including shift inspection reports, outcomes from previous pre-overhaul inspections and the reports associated with any previous overhaul.

The data in the verification dossier that’s necessary for the repair or overhaul includes, but is not limited to, the following details:

(a) Technical specification. (b) Drawings.

(c) Type(s) of protection (explosion-protection).;

(d) Operating conditions, such as environment, supply (inverter), lubricants, duty, etc). (e) Dismantling and assembly instructions.

(f) Certificate limitations (specific conditions of use), where specified. (g) Marking (including Ex marking).

(h) Recommended methods of installation, operation, maintenance, repair or overhaul for the equipment.

(i) List of spare parts.

(j) Summary of previous history, including previous overhauls and any pre-overhaul inspections and repairs carried out.

NOTE: Manufacturers have and are likely to make small changes to identical equipment and have these certified to meet specific client requirements. In these instances the change may be in the form of a ‘supplementary certificate/approval’ and the original drawing may well have been used but with a revision.

Therefore, it is strongly recommended that if the repair house decides to make a copy of the documents for its work files, the equipment serial number should be documented to ensure correct reference for future overhauls or, more importantly, that incorrect reference material is not used.

3.7 TRANSITION OF STANDARDS

The evolution of Standards is usually driven by a number of issues that relate to— (a) experience in the use of the Standards and the identification of deficiencies; (b) changes and improvements to materials and process conditions; and

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(c) specific application of equipment.

In fact, the updating of Standards is a regular and consistent process.

The adoption of IEC Hazardous Area Standards as Australian and New Zealand Standards (AS/NZS) began in 1999 and the transition, particularly for the equipment Standards, is now complete. This means that the reference numbers for AS/NZS Standards have changed to match the adopted IEC Standard numbers. To further complicate the numbering, the original series numbers for Standards covering ‘combustible dusts’ is undergoing another change in order to bring all Standards into the 60079 series. The following provides assistance in selection of Standards:

TABLE 1

APPLICABLE STANDARDS FOR HAZARDOUS AREAS

Description of explosion protection technique

Applicable Standards and designated symbol

Remarks

Zone 0

Intrinsically safe, Ex ‘ia’ AS 2380.7 (see Note 1) AS/NZS 60079.11 Encapsulated, Ex ‘ma’ AS/NZS 60079.18 Special protection, Ex ‘s’ AS 1826

IEC 60079-33 (see Note 2)

In accordance with the requirements for Zone 0

Zone 1

Intrinsically safe AS 2380.7 (see Note 1) AS/NZS 60079.11 Ex ‘ib’ Special protection, Ex ‘s’ AS 1826

IEC 60079-33 Ex ‘s’ (see Note 2) Flameproof enclosure, Ex ‘d’ AS 2380.2

AS/NZS 60079.1 Encapsulated, Ex ‘m’ AS 2431

AS/NZS 60079.18 Ex ‘mb’

Pressurized rooms or pressurized enclosures AS 2380.4 AS/NZS 60079.2 Ex ‘p’ Increased safety AS 2380.6 AS/NZS 60079.7 Ex ‘e’ Ventilation AS 1482 Ex ‘v’

Powder filling AS/NZS 60079.5 Ex ‘q’ Oil immersion AS/NZS 60079.6 Ex ‘o’

Zone 2

Special protection AS 1826 Ex ‘s’

IEC 60079-33 Ex ‘s’ (see Note 2)

In accordance with the requirements for Zone 2 Non-sparking AS 2380.9 IEC 60079-15

AS/NZS 60079.15 Ex ‘n’

2nd Edition (2001) of IEC 60079-15 is not acceptable

Ventilation AS 1482 Ex ‘v’ In accordance with the

requirements for Zone 2 Pressurized rooms or pressurized

enclosures

AS 2380.4

AS/NZS 60079.2 Ex ‘p’

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Description of explosion protection technique

Applicable Standards and designated symbol

Remarks

Zone 20

Intrinsically safe AS 2380.7 (see Note 1) AS/NZS 60079.11 Ex ‘ia’ AS/NZS 61241.11 Ex ‘iaD’

Encapsulated AS/NZS 60079.18 Ex ‘ma’

Dust enclosure protection AS/NZS 60079.31 Ex ‘ta Special protection AS 1826 Ex ‘s’

IEC 60079-33 Ex ‘s’ (see Note 2)

In accordance with the requirements for Zone 2 Zone 21

Intrinsically safe AS 2380.7 (see Note 1) AS/NZS 60079.11 Ex ‘ib’ AS/NZS 61241.11 Ex ‘ibD’

Encapsulated AS/NZS 61241.18 Ex ‘mD’

Dust enclosure protection AS 2236 ‘DIP’

AS/NZS 61241.1.1 ‘DIP’ A21 AS/NZS 61241.1 Ex ‘tD’ A21 AS/NZS 60079.31 Ex ‘tb’ Pressurized enclosures AS/NZS 61241.4 Ex ‘pD’ Pressurized rooms AS 2380.4

Zone 22

Dust enclosure protection AS/NZS 61241.1.1 ‘DIP’ A22 AS/NZS 61241.1 Ex ‘tD’ A22 AS/NZS 60079.31 Ex ‘tc’ NOTES:

1 Superseded Standard. 2 Under development

3.8 SELECTION OF SERVICE FACILITY

The owner or operator of the equipment requiring repair or overhaul should ensure that the service facility has available (either in-house or through subcontracts) all the equipment and facilities to allow completion of repairs and overhauls it attempts without compromising the quality and effectiveness of the repair or overhaul. Third-party quality and technical surveillance schemes assist the equipment owner/operator to achieve this requirement, with periodic reviews of service facilities against a specific standard, providing a higher level of confidence that inspections, repairs and tests are completed to the highest possible standards.

The recently established ANZEx Service Facility Certification Scheme also ensures technical governance of the individual surveillance bodies and a consistent level of reporting service facility capabilities.

Selecting a repair or service facility without the appropriate requirements increases the likelihood that the equipment may not be compliant with certification/approval documentation.

3.9 SERVICE FACILITY CAPABILITIES

The service facility should possess all the equipment and facilities to do overhauls and repairs, and operate a management system that ensures the quality and effectiveness of

TABLE 1 (continued) TABLE 1 (continued)

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A service facility may subcontract work to an outside facility, provided that the service facility is responsible for the assessment of and compliance with the Standards and certification/approval documents.

A workshop that requires recognition for the overhaul and repair of an Ex component must be able to satisfy the following basic requirements as required in MP 87.2 and they must have the in-house knowledge, skills, equipment and required competency to fully undertake the following:

(a) The initial assessment, inspection and tests to ascertain the incoming Ex condition and functionality.

(b) The ability to restore worn, failed or damaged equipment to its original compliance, and robustly retain this specification in future service.

(c) The final assembly, inspection, tests and reporting to ensure Ex compliance and functionality.

(d) Notwithstanding the capabilities of a subcontracted third party, the repair facility should conduct rechecks on the repair work and include this report documentation with all other job sheets for inclusion with the final report.

3.10 WORK FLOW 3.10.1 Overview

In most cases the management of equipment sent to a service facility for overhaul will follow a common sequence of events. Typically, the equipment will be logged and inspection documentation prepared prior to an initial inspection to identify features demanding attention in the overhaul process. It is normal practice to allow the service facility to strip and quote, and to develop an agreed work scope based on its findings.

The initial inspection by a competent person will result in a comprehensive report that should form the basis for the scope of works associated with the overhaul. This scope of works should be confirmed with the owner/operator prior to the commencement of works. Service facilities are reminded that in cases where significant work is required to restore a piece of equipment to the condition described by certification/approval documents, it may be more cost-effective to consider full replacement of the equipment.

Assuming owner/operator acceptance of the scope of works, overhaul should proceed under the supervision of a competent person. Guidance on possible outcomes of the overhaul is provided in Fig 3.1, while guidance on specific techniques and methods of verification is provided in subsequent sections.

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Goods inward review for ex

equip

Is equip ex? Overhaul as non-ex equipment No Document equip details Yes Enter equip details in job system

Do you have cert documents?

Strip, inspect and measure fill in detailson report Do you have OHaul

document? Create OHaul document from certification documents Yes No Yes

Are there any non-conformance? Are any repairs required? Complete OHaul and document No No Contact customer and request verification dossier Are they available? No Obtain authority from customer and obtain Yes Is equip Group 1? No Advise customer unable to ex-OHaul Yes Remove ex marking Do you have the copy of manufacturing Standard? No Yes No Go to

Carry out final inspection and dispatch with OHaul documents Attached OHaul

label

Place copies of OHaul documents in job file

Close job and archive Quote/report to customer Yes Can they be resolved? Yes No Yes Does customer want

non-ex OHaul? Return as scrap

Yes No

Create OHaul document from

Standards requirements

FIGURE 3.1 SERVICE FACILITY MANAGEMENT OF EXPLOSION PROTECTED EQUIPMENT

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3.10.2 Initial inspection

Equipment submitted for repair or overhaul should be subjected to a preliminary examination to identify work necessary to allow the equipment to be returned to its previously certified condition. This inspection should take into account the outcomes of previous pre-overhaul inspections (if available), owner/operator comments associated with the return, known deleterious conditions associated with the working environment and use, and relevant documentation including safety alerts, certification/approval documentation, asset manuals and history.

The inspection should be conducted in an orderly manner, typically from equipment identification to external and final internal examination. Owner/operator comments may lead the inspector directly to significant non-conformance, however these may describe symptoms rather than identify root causes. Care should be applied to ensure that all areas of non-conformance arising from a failure are identified and documented. This should consider both the sequence of failure and consequential damage that may arise. Inspections should, where possible, be conducted in a sequence that minimises unnecessary work. Where other certified parts are attached to the equipment, the attached parts should be checked for compliance with their relevant certification/approval documentation.

A checklist for initial inspections of equipment is provided for each protection technique in the relevant Sections of this document.

3.10.3 Failure analysis

Failure analysis should be conducted during the initial inspection process and during the review of past history (based on information from the verification dossier, owner/operator comments and safety alerts) on this equipment and against equipment having similar features (design/construction/operating environment). Failures of not-obvious underlying causes should be also investigated, e.g. associated equipment (pump or fan) causing premature failure of primary drive (motor).

3.10.4 Determination of conformity

Following the initial inspection, the repair facility should establish all areas where the equipment under inspection is not in conformance with the specification parameters agreed with the client and the certification/approval documents. In establishing conformity, consideration should be given to the measurement capability of the workshop equipment. 3.10.5 Determination of pass/fail criteria

The competent person should establish and document pass/fail criteria for explosion-protected characteristics of the equipment that is to be repaired or overhauled. Pass/fail criteria will be determined by certification/approval documentation, verification dossier documentation, protection techniques and owner/operator specification. The range and precision of measurement equipment can then be determined to fulfil the inspection, test and verification activities.

3.10.6 Exceptional circumstances 3.10.6.1 General

Occasionally, repairs to explosion-protection characteristics on large equipment can be safely completed in-situ without relocating the equipment to a service facility. Where repairs are required to a removable part that is well defined in certification/approval documentation, the removable part may be transferred to a service facility for repairs. Alternatively, in-situ temporary repair that can be completed safely and that ensures the robust ongoing maintenance of the explosion-protection characteristics may be considered.

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3.10.6.2 Repair and partial acceptance of component parts of explosion-protected equipment

In the event of damage to a component part of explosion-protected equipment, it may be possible to repair a ‘well defined’ part at a service facility and refit the repaired part to the main explosion-protected equipment that remained (isolated) in the hazardous area. This procedure is unlikely to be suitable for component parts that require dynamic testing of the equipment, such as balance and/or load testing of rotating machines, but more likely to be suitable for doors on enclosures, etc.

Although the service facility may receive only a component part, it must endeavour to fulfil all the usual inspections, tests and reporting functions that would be completed if the whole equipment item had been submitted, e.g. hydrostatically testing a large flameproof door after structural repairs, with the door bolted to a mock enclosure.

Similarly, if a piece of defined equipment is delivered to the service facility missing a component, say a potted gland that has been left attached to the cable at the installation site, the service facility may continue the repairs or overhaul on the equipment and then carry out inspection of the gland at reinstallation, or leave that activity to a competent person employed by the owner/operation.

In all of the these situations, the service facility must clearly report what equipment components had been repaired, and the relevant final dimensions, tests and inspections that have been completed to verify the equipment components and the main equipment item when the repaired component has been reinstalled.

3.10.6.3 In-situ temporary repairs of component parts in explosion-protected equipment In-situ repairs may be undertaken with the support of the operator with local site safety provisions. It is preferable that hot work or work with non-explosion protected tools is completed outside the hazardous zone. The operator will need to undertake a specific safety risk assessment for the work completion and any residual risk that a temporary repair may entail. Temporarily repaired equipment must be scheduled for permanent restoration at the earliest possible opportunity.

Should a service facility be contracted to undertake an in-situ temporary repair, although this will need to be completed with the necessary cooperation of the site operator, it is the role of the service facility’s competent person to verify that the temporary repair has sufficient integrity to ensure that the explosion-protected characteristics have not been impaired. The competent person may need to devise alternatative test procedures or increase the detailed (in-situ) inspection frequency to ensure that the temporary repair retains the necessary explosion-protection integrity while in-service. An example of a temporary thread repair for flameproof equipment is detailed in Section 6.

3.10.7 Resolution of Scope of Works 3.10.7.1 General

In establishing a scope of works the following considerations are relevant:

(a) The service facility should consult with the owner/operator in defining the scope of work required in the various categories after ensuring that the equipment is of an appropriate type, and certification/approval documentation is available in sufficient detail to carry out all checks and tests, as required by the appropriate Standard.

(b) Once a repair/overhaul procedure has been established and accepted by the owner/operator, the repair facility should ensure that no variation to the scope of work is conducted without first receiving written acceptance of the proposed change from the owner/operator.

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3.10.7.2 Overhaul—No repair

Compliance with current certification/approval and equipment identification is established by carrying out all checks, measurements and tests as required by the overhaul Standard. The results should be recorded on the overhaul and examination report.

In some cases equipment may be found to be fully compliant with the explosion-protected Standards, however documentation is not complete or adequate. The documentation issues should be addressed as outlined in Clauses 3.10.7.5 and 3.10.7.6.

3.10.7.3 Overhaul—Repair

The competent person should establish the actions necessary to restore the equipment to the agreed condition. This should consider:

(a) Rectification of the explosion-protection characteristics. (b) Replacement of component parts.

(c) Processes to strip, repair and reassemble equipment. 3.10.7.4 Compliance documentation essentials

National Standards for repair and overhaul of explosion-protected equipment highlight the essential requirements to verify adherence to the original certification/approval documentation. Safety components, critical parts and dimensions are defined in the manufacturer’s documentation and certification/approval documents to enable verification of the integrity of the explosion-protected characteristics of the equipment. The owner/operator of the equipment is required by AS/NZS 60079.14 to maintain a verification dossier (refer to Clause 3.6) that retains the necessary reference documentation for the service facility to validate the explosion-protection characteristics of the equipment to be repaired and/or overhauled.

3.10.7.5 Management of documentation inconsistencies

For some equipment, the repair facility may be able to assess the equipment as compliant, while documentation is inconsistent with current expectations, or incomplete. Where inconsistencies in documentation are found that do not affect the explosion-protection status of the equipment, these should be drawn to the attention of the owner/operator for rectification. These inconsistencies should be clearly identified in the concluding reports. 3.10.7.6 Deficiencies in compliance documentation

Should the service facility be confronted with a situation where certification/approval documentation is not available but sufficient information is available to identify the type of protection and Standard to which the equipment was manufactured, the owner/operator of the equipment needs to be consulted to obtain all available information to aid service to validate the integrity of the equipment’s explosion-protection characteristics.

It should be noted that this practice is unacceptable in Group I and some explosion-protection techniques. As stated in AS/NZS 3800, repair and overhaul without compliance documentation is not permitted for the following equipment:

(a) Equipment for Group I applications.

(b) Equipment certified as intrinsically safe Ex ‘i’.

(c) Equipment certified as encapsulated apparatus Ex ‘m’.

Where multi-group (i.e. Group I/II) equipment cannot be validated against the relevant certification/approval documentation and alternate means of validation are used, the equipment label plate and overhaul and examination report need to clearly state that the equipment is not suitable for use in a Group I hazardous area.

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For all other equipment, the recognized service facility needs to make every effort to obtain the certification/approval documentation prior to carrying out any repair. The effort to obtain the information needs to be fully documented, and included in the verification dossier for the equipment.

Where the nameplate, and a copy of the original Standard to which the equipment was manufactured are available to determine the protection technique, the equipment may be repaired by or under the supervision of a competent person working in a recognized service facility.

The owner/operator should recognize that service facilities are not explosion-protected equipment test authorities that test and verify the design compliance to Standards. Rather, they perform a quality service of returning equipment to a functional condition and validating the explosion-protection features typically set out in the equipment’s compliance documentation. The owner/operator may elect for a key item of explosion-protected infrastructure to be repaired or overhauled with limited availability of the equipment’s design characteristics, but must retain the responsibility to ensure ongoing safe use of the equipment.

Typically, a risk assessment is carried out prior to the repaired equipment being installed. The risk assessment may identify that the overall consequence of reinstating this equipment is acceptable when full and detailed compliance documentation is not available for ongoing validation of the explosion-protection characteristics of the equipment. It is typical in contemporary OHS management that alternative proof of compliance must be available and it must demonstrate an equivalent or greater level of safety to AS, NZS or IEC Standards. Should a risk assessment be undertaken, it would be advisable to retain a copy of the report within the verification dossier for the equipment.

The owner/operator may seek the assistance of the service facility’s expertise during the risk assessment. It may also be beneficial that this risk assessment be undertaken, prior to completion of the repair and overhaul, because some outcomes of the risk assessment may be required to be installed within the equipment while it is stripped down, e.g. the installation of additional temperature sensors.

Should copy winding on motors be considered, refer to Section 5.

Additional reporting requirements and special compliance label marking are required for repaired or overhauled explosion-protected equipment that has not been validated against original certification/approval documentation (refer to Clauses 3.10.13 and 3.10.14).

3.10.7.7 Insufficient information

Where insufficient information is available to satisfy the requirements in Clause 3.10.7.6 or for equipment excluded from the alternative means of verification described in Clause 3.10.5, the equipment needs to be brought into line with the current applicable Standard.

If this is the case, proof of compliance with the current Standard needs to be sourced. A certificate of conformity or other means that may be acceptable to the local regulatory authority should be obtained.

Alternative management techniques as outlined in AS/NZS 2381.1 may be considered. This will require consultation with the owner/operator and lies outside the scope of the overhaul repair Standards.

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3.10.8 Changes to equipment

3.10.8.1 Changes to equipment described in certificate documents

Changes to equipment described in certificate documents are defined as alterations. For such changes, the following should apply:

(a) The service facility should obtain the necessary certification/approval documentation. (b) The service facility should sign an undertaking that the equipment still complies with

the original certificate.

3.10.8.2 Changes not described in certificate documents, affecting the explosion-protection characteristics of the equipment

Changes to equipment that affect the explosion-protected properties of the equipment that are not described in certificate documents are defined as modifications. Where such changes are performed, the service facility should attempt the following:

(a) If the original certificate holder is still trading, the certificate holder should be notified prior to any work being undertaken.

(b) The service facility should attempt to obtain the necessary certification/approval documentation. Refer to Section 18 for certification options.

(c) The service facility should inform the owner/operator that the equipment no longer complies with the original certificate and that an application for a new certificate should be made. If the owner/operator does not wish to proceed with re-certification, the service facility may continue to repair or overhaul the equipment but should provide a report and clear statement that it is no longer suitable for use in a hazardous area and also remove the Ex marking from the equipment.

NOTE: Modifications that affect the explosive protection parameters of the equipment are not allowed, by AS/NZS 3800.

3.10.8.3 Changes not described in certificate documents, not affecting the explosion-protection characteristics of the equipment

Some changes to equipment may not affect the explosion-protected properties of the equipment. Such changes can be considered providing that the following is applied:

(a) Any proposed change not covered by the certificate should be assessed by a competent person who has independently verified qualifications and experience (e.g. units of competency 407 and 705 in AS/NZS 4761).

(b) The competent person should provide an assessment statement demonstrating that an equivalent level of safety is achieved according to the applicable Standard.

(c) The assessment may determine that additional testing is required under the applicable Standards.

(d) The assessment should, where possible, include consultation with the certificate holder.

(e) The assessment on internal equipment changes should demonstrate the following: (i) Adequate internal relief area to eliminate potential for pressure piling.

(ii) Adequate techniques used for all arc fault limitation, electrical circuit protection and surface temperature limitation under normal and expected overload conditions.

(f) All documentation pertaining to the change, resultant tests and engineering assessments should be recorded and retained by the service facility.

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(g) The equipment owner/operator and certification/approval holder should be advised of the alteration.

Changes not affecting explosion-protected properties may include the following:

(i) An alteration to the equipment such as the addition, removal or relocation of hinge supports, mounts and glands.

(ii) Replacement of internal electrical equipment by a component of similar physical size and identical or better rating, such as power contactors, overloads, control and monitoring apparatus.

(iii) To minimise the possibility of pressure piling occurring, the internal volume should not be increased by more than 10% in total from the original free volume when replacing internal components.

(iv) Alterations to the layout form or function of the internal electrical arrangement under the following provisions:

(A) The enclosure is of simple geometry, i.e. only square, rectangular or cylindrical with a taper not exceeding 10% and no overall internal dimension exceeding any other bymore than 4:1.

(B) The internal equipment is arranged so that at least 20% of each plane area cross-section is free to permit unimpeded gas flow to eliminate the potential for pressure piling. (Separate relief areas may be aggregated provided that each area has a minimum dimension of 12.5 mm in any direction.)

3.10.9 Repair

Repair and reclamation activities must not degrade the explosion-protection technique. It is typical to use Ex-specific repair and reclamation processes and these are documented in the specific Ex technique Sections of this Handbook.

When undertaking a repair or reclamation, the process would normally involve initial assessment of the equipment against compliance documents and drawings to determine the extent of repair or reclamation required. Depending on the extent of work, the competent person can determine a viable method of repair that will achieve not only immediate compliance, but also maintain compliance after the equipment is returned to service.

3.10.10 Verification of repair

When selecting a repair process there are generally two paths to ensuring compliance. The first path is to complete the repair and then test the viability of the repair. The alternative path, for those processes that cannot be readily tested, is to follow a precise application method that ensures a consistent viable repair. For example, structural welding on a flameproof enclosure would require a hydrostatic pressure test to verify the integrity of the enclosure, however where actual testing is not applicable such as replacement of coatings, compounds or varnishing (e.g. the application of conformal coatings after component replace on intrinsically safe printed circuit board, Ex ‘m’ compound replacement, vacuum impregnation of Ex ‘e’ winding or the assemble of compression glands) the repair and assembly must consistently follow a manufacturer’s or workshop’s method of work to ensure the in-service viability of the repair when the equipment is installed in a hazardous area.

After repair or reclamation, irrespective of the verification path, a thorough inspection must be completed to ensure the integrity of the repair and that compliance with certification/approval is retained. Verification should be against documented criteria. The results of the verification process and inspections must be recorded, including actual measurements that can be verified against the original measurements.

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3.10.11 Justification for the omission of verification tests

If the competent person considers that a test or verification process detailed in Standards cannot be fulfilled, or is inappropriate for an item of explosion-protected equipment, then it is appropriate for the competent person to document that information in the compliance report and ensure the owner/operator is fully cognisant of the approach prior to returning the equipment to service. The reasons, justifications and considerations should be thoroughly documented in the job file. In these circumstances, alternative means to verify compliance as required by Standards and certification/approval should be undertaken. 3.10.12 Final inspection

The final inspection is to be undertaken by the competent person to confirm that the specifications have been achieved and the equipment has been verified and tested for compliance. A detailed report identifying the scope of work undertaken, reclamation work completed, and measurements and tests undertaken is to be completed and forwarded to the owner/operator and a copy retained by the service facility.

3.10.13 Equipment compliance reporting

As the work, tests and inspections on the equipment are being finalized, a report must be completed by the service facility and must include supporting documentation that will be provided to the equipment owner/operator for inclusion in the equipment’s verification dossier.

Reporting requirements are specified in Appendix A.

It is important that the owner/operator has an opportunity to review the completed work and verification report from the service facility prior to the installation of the equipment.

A typical repair and overhaul must define the exact item of equipment, initial inspection finding, parts replaced, repairs completed, method of repair, statement of compliance and disclosure of final critical dimensions or observation that describe the explosion-protection characteristics.

In all instances it is highly recommended that the work-scope and acceptance criteria are agreed prior to the work proceeding.

At the completion of the repair and overhaul, the owner/operator should ensure a detailed report is received from the repair house identifying:

(a) Original condition of product, complete with dimensional and clearance data. (b) Scope of work identified and agreed on.

(c) New dimensional data where repairs to these areas have been undertaken. (d) Tests results.

This document should be filed in the verification dossier and supplied to the repair house for reference at the next repair or overhaul.

NOTE: Refer to Appendix C for sample report forms.

A more comprehensive disclosure will be required if the equipment is repaired without validation to certification/approval documents. This report documentation should include all of the following:

(i) A repair and overhaul report.

(ii) A statement that the repair and overhaul has been carried out in accordance with the relevant manufacturing Standard.

(iii) A statement that conformance of the equipment with the certificate of conformity cannot be guaranteed.

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(iv) A statement that any special conditions of use have not been identified or considered in the repair or overhaul.

3.10.14 Equipment compliance labelling

Repaired and overhauled equipment should be marked with the appropriate marking as detailed in national or international repair and overhaul Standards on the main equipment in a visible place. This marking should be legible and durable, taking into account all relevant environmental conditions. The marking should include the following:

(a) The relevant symbol (see below).

(b) The repair and overhaul Standard number used for compliance verification.

(c) The name of the repairer or their, registered trademark and workshop certification No.,

(d) The repairer’s reference number relating to the job. (e) The date of the overhaul/repair.

The marking may be on a plate permanently attached to the repaired equipment.

In the event of subsequent repairs, the earlier repair or overhaul plate should be removed, and a record made of all the markings on it.

If an earlier plate has been removed and it had an inverted triangular symbol (as shown below), then the symbol on subsequent plates should also be an inverted triangular unless the repairer restores the whole equipment to full conformity with the certification/approval documents.

Equipment that after repair or overhaul conforms neither to the certification/approval documents nor to the explosion-protected requirements in Standard should have all its marking details relating to the explosion-protected characteristics removed with the agreement of the owner/operator.

The standardized symbols for marking cover two categories depending on the method of validating compliance of the explosion-protected equipment.

Where the repair or reclamation is in accordance with Standards and the repairer has sufficient evidence of full compliance with the certification/approval documents and the manufacturer’s specification, either one of the following marks is to be used.

Where the repair or overhaul is validated in accordance with Standards but not the certification/approval documents, the following mark is to be used, provided that—

(i) the equipment altered during repair or reclamation has been judged by the repairer to still comply with the restrictions imposed by the overhaul Standard and the explosion-protection technique Standards to which it was manufactured. but the repairer has insufficient evidence of full compliance with the certification/approval documents; or

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(ii) the Standards to which the previously certified equipment was manufactured are not known, but the requirements of the overhaul Standard and the current edition of the relevant explosion-protect ion technique Standards have been applied, but the repairer has insufficient evidence to assert full compliance with the certification/approval documents, then an assessment, by a competent person who has the appropriate units of competency (typically UTE NES 407 in accordance with AS/NZS 4761) has been conducted to verify compliance with the relevant level of safety prior to release of the equipment by the repairer.

In these situations the certification/approval labels should not be removed.

NOTE: The markings are required for the benefit of subsequent repairers and the only difference between the markings is the method of compliance.

Equipment that after repair or reclamation does not conform with the above should have its original manufacturer’s certification/approval label removed or altered to give a clear indication that the equipment is not certified, until a supplementary certificate is obtained to cover the repair or overhaul.

If the equipment is returned to its owner before the supplementary certification is obtained the record described in the repair report should indicate that the equipment is not in serviceable condition and is not to be used in an explosive atmosphere area. It is advisable that this report does not look similar to a compliance report.

Where changes mean the equipment no longer complies with the original certification/approval, the marking relating to the certificate of conformity or approval should be struck out on the compliance plate so that the equipment is not accidentally returned to service in a hazardous area.

3.10.15 Pre-delivery inspection

It is advisable that the pre-delivery inspection be undertaken by a competent person that is not directly associated with the repair or overhaul so that a ‘fresh set of eyes’ are used to confirm that the specifications have been achieved, documentation has been completed and the equipment has been verified and tested for compliance.

This operation is normally undertaken prior to despatch of equipment. The equipment can then be packed for safe dispatch.

The owner/operator should be advised that the equipment may be returned with conditions to be fulfilled prior to energising (the removal and blanking of ports, addition of lubrication fluids) to ensure maintenance of explosion-protected characteristics.

3.11 COMMENTARY ON MATERIALS 3.11.1 Introduction

It is important to verify that materials used in repair and overhaul are as per original design specifications, or where permitted, compatible with original materials, in order not to introduce an inferior repair. For example, brazing on flamepaths is considered inappropriate due to likely dislodgement after thermal cycling.

Replacement parts and reclamation materials must be suitable for their intended use and operating environment (e.g. the use of aluminium, lead-free solders, UV-sensitive materials, heat resistance and FRAS rating are some of the important issues to be considered).

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The following items are typical examples of materials requiring special consideration when undertaking repair and overhaul of explosion-protected equipment.

3.11.2 Aluminium and light alloys

AS/NZS 60079.0 gives guidance on the chemical composition of aluminium components permitted in hazardous areas. The use of aluminium or light metal alloys in Group I applications should be avoided where practical. The use of light metal alloys or aluminium is only permitted if it complies with AS 3584 or AS 4871.1.

3.11.3 Cast irons

Cast irons are commonly used engineering materials with higher carbon contents than steels. Their use is widespread on account of their low cost, ease of casting and ease of machining. Grades of cast iron are distinguished by their microstructure, which is determined by chemical composition and heat treatment. Different heat treatments after casting can yield different grades of cast iron from a common composition, although small additions of alloying elements are included to promote the formation of preferred structures in commercial foundries. Metallographic analysis is required to distinguish between grades of cast iron. The various grades of cast iron are described in AS 1830, AS 1831, AS 1832, AS 1833 and AS 2027.

Grey cast irons (flake graphite cast irons) belong to a specific grade of cast iron requiring special attention, because they have very different properties to spheroid graphite or SG irons. Grey cast irons have microstructures containing flakes of graphite. The presence of graphite flakes causes the fracture surface to be grey in colour and can cause the metal to be very brittle. The incidence of brittle failure is promoted by in-service damage or pre-existing manufacturing stresses and may be initiated by an apparently minor stress. The use of grey cast irons demands higher care in high-integrity applications such as explosion-protected enclosures.

Some explosion-protected enclosures include components of grey cast iron and consequently, service facilities must be aware of the materials of construction. Components contributing to the explosion-protected properties of an enclosure that are suspected of being grey cast iron may be confirmed by one of the following means:

(a) Reviewing materials of construction listed in the manufacturer’s drawings. (b) Contacting the manufacturer to confirm the materials of construction.

(c) Undertaking metallurgical microstructural analysis. This may involve cutting a sample, or in-situ polishing and replication, or visual examination using a metallurgical microscope.

Where components contributing to the explosion-protected properties of an enclosure are suspected (or have been confirmed by one of the means above) of being grey cast iron, the service facility must perform additional verification work.

All such enclosures should be over-pressure tested, or magnetic particle tested, irrespective of the category of work performed at time of repair or overhaul.

3.11.4 Corrosion inhibitors (‘grease’) and their application

Where required, only suitable lubricants or corrosion inhibitors should be used on flanges, spindles, push-button operators and the like (refer to AS/NZS 60079.1).

Some lubricants have extremely low flashpoints and under conditions of a temperature increase, spark or internal explosion could enhance flame propagation or aid flame transmission through a flamepath. It is standard industry practice to obtain the material safety data sheet (MSDS) from the manufacturer or supplier with all chemicals and compounds used in commercial and industry environments. The MSDS will define the

HB239

Handbook

Guidance on the repair and overhaul of

electrical equipment for explosive

atmospheres

Handbook

Guidance on the repair and overhaul of

electrical equipment for explosive

atmospheres

PREFACE

CONTENTS

STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND

Handbook

Guidance on the repair and overhaul of electrical equipment for

explosive atmospheres

S E C T I O N 1 G E N E R A L

S E C T I O N 2 D E F I N I T I O N S

S E C T I O N 3 T E C H N I C A L P R I N C I P L E S A N D

P R O C E S S E S