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Topic Title: Ex'e' creepage distance requirement
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Created On: 15 May 2013 08:30 AM
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 15 May 2013 08:30 AM
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SherryF

Posts: 1
Joined: 15 May 2013

I have been looking for a clear definition of a cemented joint for a while and I cannot seem to find a simple paragraph explaining what it is in the standards that I have. Would anyone be able to guide me as where to find it? I have been looking at mainly ISA 60079.7, IEC 60950.1 and IEC 60079.0. I was looking at example 5 on page 29 of ISA 60079.7; can someone please explain how the cemented joint relates to an Ex e heater seal joint?
Our company is designing an EX e (increased safety) heater assembly for the USA. We have specified the design to be compliant with ISA 60079.7 so that we can get it certified through ISA or UL. The Ex e standard defines generous min creepage and clearance distances that must be satisfied, e.g. for 320V a min clearance of 6mm is required and a min creepage of 6.3mm for material group I. Our situation is that we have two conductors that are insulated from each-other by an insulator with a number of joints. In ISA 60079.7 if the joint is un-cemented, the clearance and creepage distances are the line of sight along the joint; however there is no clear definition as how to change this joint to a cemented joint (i.e. to make it equivalent to solid insulation).
I have found some definitions that talk about a cemented joint but they refer to a joint which is filled with an insulating compound such as epoxy or silicone .
I am after a clear definition of the requirement of this insulating compound so our design would comply with the standard in order to avoid any design changes later on. Does the joint just need to be filled or is there a requirement for a certain level of bonding.

Thank you very much in advance
Sherry
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