Overhaul of Electrical Equipment for use Underground – Guidance on Compliance

Wednesday, 29 May 2019

Overhaul of Electrical Equipment for use Underground – Guidance on Compliance


Tim Webster


Capital expenditure freezes and reductions to R&M budgets are driving the industry to seek cheaper products and services. Furthermore, with a contracting industry comes a loss of personnel with a sound knowledge of explosion protection techniques. The combination of these two factors leads to an increased risk of noncompliance.


Often, new or inexperienced employees rely on procedures or the directions given to them by management without truly understanding the intent of the standards or regulations. This can lead to a situation where crucial decisions are being made which, whilst complying with a policy or procedure, may not be appropriate.


Standards within Australia are intended to be a “base-line” of best practice not a utopia or maximum requirement. To understand a standard, it is important to have an 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.


Standards within Australia are not necessarily part of the legislation. They form the “body of knowledge” that you are expected to know and understand. You may not 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 accordingly.


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


The Preface details a general history of the standard and which technical committee is responsible for its maintenance.


The Foreword is an 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 what/who the standard applies to.


The requirements section of a standard, details the minimum requirements which need to be met for compliance. This section generally has three types of information: “mandatory” requirements which are signified by the word “shall”; “recommendations” which are signified by the word “should”; And “statements” which take the form of a note or in some cases just a line of text. An example would be “Note: High Voltage electricity can be lethal”. Recommendations do 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.


Be wary of the word “consider”. In poorly worded standards, you may see phrases such as “you shall consider” or “you should consider”. This means “you must think about” or “we recommend you think about”. Demonstrating compliance to such a clause becomes challenging. Also, be wary of the words “shall” and “should” in notes. Remember notes are statements, not requirements.


Appendices are used to present other useful information such as examples of specific test requirements or examples of forms. Appendices are categorised in two different types: “Informative” or “Normative”. An informative appendix is where the standard is providing you with information only. A normative appendix is where additional requirements for compliance are listed.


AS/NZS 2290.1 “sets out requirements for the inspection and maintenance of electrical equipment designed for use in hazardous areas in and around underground coal mines.” The intent is that an operator/end user should determine their own inspection/overhaul regimes via a risk based approach. To support this approach the standard details a series of inspections which allow the mine to build up a picture of the degradation of their equipment from things such as corrosion and wear/tear over time.


This standard is misunderstood through its recommendations. These are being treated as mandatory requirements rather than recommendations. The standard actually requires that – based on history – you can extend your overhaul period or even bring it in to suit your own conditions. It details a mandatory requirement that an initial inspection be completed when the equipment arrives on site. A pre-overhaul inspection is to be completed 12 months prior to your nominated overhaul period to establish a “base-line” condition. The pre-overhaul inspection is to 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 final extension.


However, there are some exceptions to the extension rules, such as motors and cable reels. Due to the application of these devices, they are often inaccessible for inspection and therefore the standard requires these be overhauled at your nominated overhaul period.


AS/NZS 3800 “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”. The intent 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 clearly defines what needs to be done, however, there is often misunderstanding in terms of the extent of the examinations.


There are two differences between a pre-overhaul inspection to AS/NZS 2290.1 and an AS/NZS 3800 overhaul. In a pre-overhaul inspection, you are merely inspecting the accessible parts of the Ex rated equipment. This data is then used to estimate the condition of the uninspected Ex related features. The pre-overhaul inspection only records the condition of the equipment. Unless something is non-compliant, no other actions are performed. 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. As part of this overhaul, you must also repair/recover all damage/non-conformances to a level that allows the equipment to remain in service. Just giving it a skim is not performing an AS/NZS 3800 overhaul.


Unlike other standards, the appendices of AS/NZS 3800 are mostly normative i.e. requirements. Only appendices F, K and L are informative. These normative appendices detail that inspections are also required on components within enclosures to ensure that, not only are we maintaining the Ex properties, but also maintaining electrical safety and long term reliability.


There are other intricacies within AS/NZS 3800, such as certification nameplates. Unless you are the OEM of a piece of Ex rated equipment, you should not remove/replace the original certification plate without due consultation with the OEM. A third party workshop should only replace a certification nameplate if that nameplate is sourced from the OEM and is fully marked with the appropriate details stipulated on the certificate of conformity. OEM’s may or may not be willing to supply this without being provided with evidence of the enclosure remaining compliant. Another issue with certification nameplates is that they are a declaration by the OEM. If fitted by a third party without prior agreement from the OEM, then a false declaration is being made in the name of the OEM. 


Modifications/alterations are detailed within AS/NZS 3800 in so much that anything outside the original certificate of conformity must be recertified. From an OEM perspective, when a piece of Ex rated equipment is certified, the certifying bodies are provided with information on the following:

  • Internal layout of the enclosure for volume and pressure piling reasons.
  • Data on heat dissipation of components, power and voltage ratings etc.

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.


When equipment is overhauled back to its original condition, the responsibility for the design is with the OEM. Once any change is made to the design, this responsibility shifts. When working to a drawing provided by someone else, you are following someone else’s design. If you deviate from that drawing or create/modify a drawing yourself, you become the designer.


As a designer, you take on the responsibility for all aspects of the design you change. You are responsible to identify all risks associated with your design and for controlling these risks. You are responsible for providing sufficient documentation to allow the safe operation and maintenance of your design throughout its life cycle. This includes providing relevant documentation and identifying/controlling all possible risks.


As an example, the certification for an Exd enclosure states a requirement for a 10.9 grade bolt. You don’t have that bolt so you fit a 12.9 grade bolt instead. The bolt grade is greater than required so you are not making the enclosure weaker., However, the strength of the parent material you are putting the bolt into may not be as strong as the bolt. The bolts may not be as flexible and therefore could affect the properties of the enclosure which allow the safe dissipation of gasses during an explosion. The enclosure may require recertification due to these issues. You may also need to update parts books or technical manuals to reflect these changes.


Ultimately, as the end user, you are responsible for the equipment at mine site regardless of who supplied it so you need to ensure these areas are covered.


In conclusion, 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 state regulations will help. It is also important to understand what obligations you incur when you become a designer, supplier or importer. When choosing an overhaul workshop on cost alone, ensure you understand where the cost difference is being driven from in regards to comparing apples to apples in terms of service provided and compliance to standards/regulations.



Note: The views expressed here are solely those of the author in his private capacity and do not necessarily represent the views of Joy Global.

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