Fault codes for the inspection of Ex electrical equipment
The Energy Institute (EI) publication Guidelines for managing inspection of Ex electrical equipment ignition risk in support of IEC 60079-17 provides guidance on managing the ignition risks of Ex electrical equipment located in hazardous areas. This is mapped against a safety management system (SMS) framework.
It assists users in the continuing management of ignition risk by assuring continuing integrity of Ex electrical equipment type of protection, as inspection should identify faults such as corrosion, vibration, inadequate equipment selection, etc.
In this publication, recommendations are made for users to have a system in place to analyse where faults have been found and the type of fault identified, in order to be able to take corrective action. It is recommended that this system utilise fault codes, as the recording of faults using free text only is difficult to analyse within a reasonable timescale (as there is no means of grouping or classifying the information recorded).
Numerous examples of fault codes used by companies, as well as the fault codes provided in the EI publication, have been reviewed by the EI Electrical Committee and the Oil and Gas UK (OGUK) Electrical Community of Interest. After this review there was agreement for a matrix to be developed showing existing fault code systems in use by industry and how they relate to each other - to facilitate analysis of common faults recorded using different fault code systems (e.g. Arnlea fault codes).
The intent of this matrix is to assist companies in the sharing of fault data: the more companies that use the common fault code system, the easier it will be to share and learn from fault data between sites. This could assist companies by providing an evidence base to justify e.g. hazardous area inspection frequencies, etc.
The EI would like to invite companies to submit their fault codes, so that they may be inputted into the matrix.
From the fault code systems already analysed, a new set of fault codes have been proposed for use during Ex equipment inspections. These are present in the matrix and identify the following faults:
1 - Ex electrical equipment not appropriate for hazardous area
2 - Circuit identification not appropriate
3 - Enclosure defect
4 - Gasket, sealing defect
5 - Unauthorised modification
6 - Cable gland defect
7 - Ex d flame path defect (this might also cover enclosure, glands, sealing etc.)
8 - Lamp defect
9 - Electrical connection defect
10 - Cable, trunking, conduit
11 - Earthing defect
12 - Cable insulation defect
13 - Equipment insulation defect
14 - Overload, temperature protection device defect
15 - Corrosion, weather, vibration defect
16 - Dust or dirt defect
17 - Ex p pressurisation or pre-start purge defect
18 - Intrinsically safe earthing defect
19 - Intrinsically safe printed circuit board defect
20 - Intrinsically safe circuit defect e.g. invasion of power circuit, point to point screen defect
There is also need to demonstrate that an Ex inspection and maintenance strategy for electrical equipment is fit for purpose and safe. Significant failures of Ex equipment should be identified, to be able to assess whether the level of significant failures is acceptable or not. This acceptability can be defined as the 'acceptance safety level' (ASL), and in the EI publication is defined as the number of fault equipment that is declared as being unacceptable, on average, expressed as a percentage. When recording faults, a way of identifying a significant fault would be to use an 'S' suffix attributed to a particular fault code.