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Do I need to use a feeler gauge on an Ex d flanged flamepath in a Group II (Surface Gas and Vapour) installations?

Sometimes, but first we need to clarify the distinct difference with Group I (Underground Coal) and Group II (Surface Gas and Vapour). Group I and Group II installations in Australian are governed by separate legislation and in some case differing standards. This results in differing requirements for the verification of flanged flamepaths. In Group I it is industry best practice to use a 0.2mm feeler gauge during the daily visual inspections to verify the gap of the flame path is below the maximum allowable value.

But this is not the case in group II, group II inspection requirements in Australia are governed by AS/NZS 60079.14 for initial detailed inspections and AS/NZS 60079.17 for periodic inspections, although it must be noted the initial detailed inspection requirements listed in AS/NZS 60079.14 are sourced from AS/NZS 60079.17 so the later standard should be referred for further detail on inspection requirements.

So what does AS/NZS 60079.17 say is required? Table 1 of this standard sets out the requirements for inspections of Ex d equipment. Check A16 which is only required to be checked during a detailed inspection requires the inspector check that dimensions of flanged joint gaps are:

1: within the limits in accordance with manufacturer’s documentation, or
2: within maximum values permitted by relevant construction standard at time of installation.

It is important to note that AS/NZS 60079.17 does not require this check to be carried out during every detailed inspection. Inspection check A16 of Table 1 should be applied when a visual examination of flanged joint surfaces suggests that dimensions may be exceeded.


“This following information represents and opinion only of a general nature, the specifics of each individual situation must be taken into account with reference to the relevant Legislation, Codes of practice and Australian standards. Professional advice should be sort if there is any doubt.”

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