Tim Webster


In the current economic climate of cut-backs and limited maintenance budgets, all end users are looking to reduce the costs of their maintenance schedules and overhauls as much as possible. This has led to a clash of objectives i.e. to keep the equipment safe and compliant, whilst spending as little money as possible to achieve this. To compound this clash, job losses within the industry have resulted in the loss of a significant amount of expertise and experience in regards to explosion protection which has in turn lead to misunderstanding of the requirements of certain standards and legislation.

This paper provides guidance ExTA on the requirements of AS/NZS2290.1, AS/NZS3800 and the relevant state legislations regarding Overhauls, Repairs, modifications and the roles of Designers, Manufacturers, Importers and Suppliers to ensure that we all understand these and can make sound decisions in regards to overhauls and repairs.


The combination of capital expenditure freezes and reductions to R&M budgets are driving the industry as a whole to seek cheaper products and services. Furthermore, with a contracting industry comes a loss of personnel with a sound knowledge of explosion protected equipment, techniques and associated standards. The combination of these two factors undoubtedly give rise to increased risks of noncompliance.

Often, new or inexperienced employees rely of written procedures or the directions given to them by management without truly understanding the intent of the requirements of the standards nor local legislation. This can lead to a situation where crucial decisions are being made which, whilst complying with a policy or procedure, may not actually be the most appropriate.

The use of Standards within Australia is intended to be a “base-line” in best practice and community expectation, not to be seen as a utopia or maximum requirement. To truly understand the requirements of a standard, it is important to not only be familiar with the clauses, but also to have a good understanding of the structure / format of the standard i.e. the difference between “Shall” and “Should”, the intent of a “note” or why information is included in an introduction or an annex rather than the body of a standard.

AS/NZS 2290.1 is intended to provide guidance on inspection and overhaul frequencies to ensure that equipment in the field is kept in a condition that does not impact of the safety of mine personnel, but is it always being applied appropriately? For example, should this standard be applied to a licensed workshop when equipment is sent to them for overhaul?

AS/NZS3800 if primarily focused on the overhaul of Ex rated equipment and gives information on what inspections should be carried out during an overhaul as well as how to rectify any damage found, but it also goes further. AS/NZS3800 also strays in to the realm of electrical safety and product reliability by looking at the internal components of enclosures. Is it really sufficient to inspect/repair the flamepaths or threaded holes of an Exd enclosure and then claim compliance to the standard?

AS/NZS3800 also details what action should be undertaken if a modification is made to the equipment from an Ex protection perspective, however, making modifications to equipment has far greater ramifications than just Ex compliance. When we modify an electrical circuit do we fully understand the implications, under law, of what we are doing?

Of course, it is possible to successfully maintain equipment during its life cycle under a limited budget and to ensure any modifications made are safe, compliant and legal. The options available to all involved are many and varied, however, underpinning all of these options lies the need to fully comprehend what the expectations of the community are in terms of best practice and legal requirements.


Standards in General

Standards within Australia are, on the whole, not part of legislation. They are a base line guidance on what the broader community expect to be the best practice in a particular field. The form part of the “Body of Knowledge” that you are expected to know, understand and take into account when performing relevant activities. You may not necessarily need to comply with a standard, but you do need to be able to demonstrate you have taken into account the issues and the guidance given in them and acted in an appropriate manner.

Standards have a definite format in terms of structure. This generally means a Preface, Contents, Foreword, Scope, Requirements and Appendices.

The Preface gives a general potted history of the standard and details which Technical Committee is responsible for the ongoing maintenance of the standard.

The Foreword is a general overview of “why” the standard exists and what it is trying to achieve.

The Scope provides detail on “what” the standard covers, it’s boundaries, and most importantly what / who the standard applies to.

The requirements section of a standard, as the name suggests details the minimum requirements which need to be met to demonstrate compliance with the standard. This section generally has three types of information in it.

The first is a “Mandatory” requirement. This is signified by the word “Shall” in the clause and is not optional if you are to demonstrate compliance.

The second is a “recommendation”. These are signified by the would “Should” in the clause. This recommendation does not need to be adopted when complying with the standard, however, you need to be able to justify why you haven’t, and demonstrate suitable control of the issue equivalent to that detailed in the standard, or better.

The third is a statement. These can take the form of a note or in some cases just a line of text. Such a statement would be “Note: High Voltage electricity can be lethal”.

Some things to be wary of are the words “Consider” and it’s use. In some poorly worded standards, you may see phrases such as “You shall consider”, “You “Should Consider”. Effectively this means “you must think about” or “we recommend you think about”. Demonstrating compliance to such a clause then becomes a game of words. Another thing that can sometimes be seen are the words “Shall” and “Should” in notes. Remember a note is a statement, not a requirement.

Appendices at the end of a standard are often used to present other useful information such as examples of specific test requirements or examples of forms that could be used. Appendices are categorised into two different types, these being “Informative” or “Normative”. An informative Appendix is where the authors of the standard are providing you with useful information only. A Normative Appendix is where the authors have provided additional requirements which need to be met just as if it were in the body of the standard.

AS/NZS 2290.1

This standard “sets out requirements for the inspection and maintenance of electrical equipment designed for use in hazardous areas in and around underground coal mines.” The basic essence of the standard is that an operator / end user should determine their mine specific inspection and overhaul regimes via a risk based approach. To support this approach the standard details a series of inspections which, if adequately implemented, should allow the mine to build up a picture of the degradation over time of their equipment from things such as corrosion and wear / tear.

The standard then goes on to make a series of specific recommendations for inspection and overhauls based on protection concept type.

How this standard often gets misunderstood is around these recommendations. Some people treat these as cast in stone i.e. you must overhaul your continuous miner every 4 years to comply with the standard. Whereas, what the standard actually says is that, based on history, you can extend your overhaul period or even bring it in to suit your mine specific conditions. It details a mandatory (“shall” statement) requirement that an initial inspection be completed when the equipment arrives on site. It then goes on to require a pre-overhaul inspection be completed 12 months prior to your nominated overhaul period to confirm if the overhaul period is appropriate or needs to be adjusted. The pre-overhaul inspection should then be repeated 12 months later and compared to the previous inspections. A risk based approach can then be used to extend the overhaul period out by a further 12 months. At the end of the first period of extension, a further Pre-Overhaul Inspection can be performed allowing a second and final extension.

There are a couple of key exceptions to the extension rules however. These are notably for motors and cable reels. Due to the application of these devices, they are often inaccessible for inspection during a pre-overhaul audit and therefore the standard requires these be overhauled at your nominated overhaul period regardless of the results of the Pre-Overhaul inspections.

They key aspect of this is that the standard does not state that your overhaul period shall be four years. It only recommends this in tables 1 through 4. If you have sufficient supporting data to justify it, you can set your overhaul period to be whatever you deem appropriate, however, the key issue is having that supporting data and ensuring it is strong enough to withstand scrutiny by the Inspectorate.

AS / NZS 3800

“This Standard gives guidance on the practical means of maintaining the electrical safety and performance requirements of repaired, overhauled and reclaimed equipment in compliance with the provisions of the certificate of conformity.” – Preface of AS / NZS 3800. The basic essence of this standard is to detail what inspections should be performed during an AS/NZS 3800 compliant overhaul and to advise on what repairs can be carried out. The standard itself is fairly clear on what needs to be done, however, there is a common misconception in terms of how far to go with the examinations, for example does every cable entry need to be inspected / repaired? Do we just limit our inspection to what is accessible, as per a pre-overhaul inspection to AS / NZS 2290.1?

There are two big differences between a pre-overhaul inspection to AS / NZS 2290.1 and a AS / NZS 3800 overhaul. In an AS / NZS 2290.1 pre-overhaul inspection you are just looking at the accessible parts of a piece of Ex rated equipment to be able to make a determination of the degradation of the Ex protection measures i.e. I have looked at 4 out of 6 cable entries and based on the condition of those 4, I can determine that the remaining 2 are OK. Another aspect of the AS / NZS 2290.1 pre-overhaul inspection is that, unless something is non-compliant, you are just recording it’s condition. When performing an AS/NZS 3800 overhaul you are required to inspect every part of an Ex rated piece of equipment to determine if it is still compliant or not. You are also expected, as part of the overhaul to repair / recover all damage / non-conformances to a sufficient level that allows the equipment to remain in service for the mines specified overhaul period. Effectively, just giving the door and it’s corresponding flame path on the enclosure a skim is not performing a full AS / NZS 3800 overhaul.

Unlike many other standards, the appendices of AS / NZS 3800 are mostly normative i.e. requirements. In fact only appendices F, K and L are informative. These Normative appendices go on to detail that inspections are also required on the internals of enclosures etc. to ensure that not only are we maintaining the Ex properties, but also maintaining the electrical safety and long term reliability of the equipment. This is also a key aspect of the AS / NZS 3800 overhaul that often gets misunderstood.

There are some other intricacies that may get misunderstood within AS / NZS 3800. One of these is around certification nameplates. Unless you are the OEM of a particular piece of Ex rated equipment, you should not remove or replace the original certification plate fitted to it without due consultation with the OEM.. A third party overhaul workshop should only replace a certification nameplate if that nameplate is sourced from the OEM and is fully marked with the appropriate certification details, serial numbers and date of manufacture. OEM’s may or may not be willing to supply this without you providing sufficient evidence that the enclosure is still compliant. One other

aspect around certification nameplates is that they always carry the name of the OEM and therefore are a declaration by the OEM. If a third party fits these nameplates, without prior agreement from the OEM, then you are making a false declaration in the name of another organisation. What are the legal ramifications of this and do you fully understand them?

Modifications / alterations are detailed within AS / NZS 3800 in so much that anything outside the original certificate of conformity must be recertified, but how far do we take this and how far would a mines inspector actually apply this? From an OEM perspective, when we certify a piece of Ex rated equipment, we have to provide the certifying bodies with information on the internal layout of the enclosure for volume and pressure piling reasons. We have to provide data on heat dissipation of components, power and voltage ratings etc. This level of information can vary depending on the Ex concept utilised. When modifications or changes are made to Ex equipment, unless you have full access to this data and can demonstrate you have maintained compliance with this information, you need to recertify.


On a broader level, modifications are another potential area of concern. When equipment is overhauled back to its original condition with everything exactly as it was supplied by the OE, the responsibility for the design remains with that OE. Once any change is made to the design, not matter how small, this responsibility shifts. When working to a drawing provided by someone else, you are following someone else’s design, the moment you deviate from that drawing or create / modify a drawing yourself you become the designer.

What is so bad about being a designer?

As a designer, you take on the responsibility for all aspects of the design you change. You are responsible to identify all risk associated with your design and you are responsible for controlling these risks. You are also responsible for providing sufficient documentation to allow the safe operation and maintenance of your design throughout its life cycle. This means you need to risk assess the design, you need to provide adequate drawings, maybe a technical manual and possibly suitable training.

As an example, say you have an Exd enclosure where the certification states a requirement for a 10.9 grade bolt. You don’t have that grade bolt available so you fit a 12.9 grade bolt instead. It’s stronger so where is the risk? Did you consider the strength of the parent material you are screwing the bolt into? Did you consider that now you have used stronger bolts, perhaps the properties of the enclosure which allow the safe dissipation of high pressure gasses during an explosion may now be changed due to the bolts not being as flexible? Did you have the enclosure recertified under your own organisations name? Did you change the parts catalogue for the equipment? Did you review the technical information provided with the equipment to ensure it now accurately reflects the equipment you have provided? Finally, would you rather ask these questions of yourself or finish each answer with “Your Honour”?

All of these relate to such a small and simple change. Just imagine what happens when you make a more complex change such as changing the design of a gear box or making changes to a control system. It isn’t hard to find someone who is willing to “improve” someone else’s design or to find an expert PLC programmer but are they prepared to do their due diligence in regards to the design and the required documentation? Ultimately, as end users, you are responsible for the equipment on your mine site regardless of it coming from the OE, from a licensed workshop or your mate Fred with a shed down the road


You can operate, maintain and overhaul your equipment in a safe and compliant manner on a tight budget, but to do so requires that you understand where costs can be cut, what repairs can be ignored and what repairs are non-negotiable. Having a thorough understanding of AS / NZS 2290.1 and AS / NZS 3800 and your specific state regulations will help. By this I don’t just mean what are the expectations of you as a mine engineer, an equipment operator or a maintenance person, but also in regards to what obligations you incur when you step over that line and become a designer, supplier or even an importer. By working with your chosen licensed workshop you can achieve your goals but I would ask that when choosing an overhaul workshop on cost alone ensure you understand where the cost difference between different workshops is being driven from i.e. are you comparing apples to apples in terms of service provided and compliance to the standards.





AS / NZS 2290.1

AS / NZS 3800

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