Flame Proof Motors

[fredt]

Does anyone have experience with motors seizing due to contact with the inner flame path housing in the event of a bearing failure. I am trying to assess if this is a common problem.

 

[stardelta]

Yep! we see it all the time, flamepath damage of the nature you describe is very common with ExD machines owing to the close tolerances and reduced clearances required. Here in the UK the ExD concept of protection has taken the place of the old BS229 flameproof-motor and the term "Flameproof" is generaly no longer used.
Its very rare for an Ex machine to suffer a catastrophic bearing failure without some collateral mechanical damage to the flamepaths. Some, but not all ExD machines can be safely repaired using carefully controlled reclaimation techniques that will restore the original dimensions and bring it back to its relevent construction standard without compromising its integrity. With smaller machines it becomes a question of economics and it is often cheaper to replace than repair. The ATEX regulations have opened up the European Ex market and prices of new equipment have dropped considerably as a result of the increased competition. Larger or special machines can be cost effective to repair however its a specalised field and can be something of a minefield. Not all repair companies have the knowledge or experience to safely carry out Ex repairs and its best left to competent repair companies with trained personel who follow the EASA/AEMT codes of practise relating to Ex repair procedures.