Cemented and Un-cemented joints ISA60079.0

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SherryF

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Hello,
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?
Also would anyone be aware of the differences between ISA 60079.0 and IEC 60079.0. Would you know which parts are different/ or identical?
Thanks a lot,
Sherry
 
I believe you have more success reviewing IEC 60079.7. Cementing is not usually an Ex e feature.

There are significant differences between NEC and IEC "Zones" and the differences are becoming more complex with each IEC 60079 series and NEC update.
 
Thank you very much for your prompt reply. Apologies, I think that I needed to be more clear with my question:
Our company is designing an EX e (increased safety) heater assembly for 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.
I would appreciate if you or anyone else could shed some light on this. Do you think it would be a good idea to include this question in another section of the forum (insulation standards, etc)?
Thank you very much in advance and kind regards,
Sherry
 
I would suggest contacting Intertek Australia for your initial evaluation. They would then submit their findings to the Cortland, New York, USA office for final approval.

You should know that Zone electrical area classification has not caught on that well in the US. “AEx” products are acceptable in US Division 2, but not generally for Division 1 unless also certified to Zone 0 standards. The “A” means it has been certified to a US Standard. Of course, “Ex e” alone is not suitable for Zone 0.
Note: ISA does not certify anything; they just write the standard.

Technically, “Ex e” or “AEx e” are virtually meaningless in US domestic Division 2 applications. They aren’t necessary.
 
Hi there, thanks again for your prompt reply. We have come across this definition for cementing in clause 8.9.3 of IEC 60601.1 for future reference if anyone needs it:

Cemented Joint: Examples of a cemented joint include such treatment as potting, encapsulation and vacuum impregnation, and components or sub assemblies that are treated with an insulating compound that fills voids. Where distances between conductive parts are filled with insulating compound, including where insulation is reliably cemented together with insulating compound, only the requirements for solid insulation apply. Compliance is checked by inspection, measurement and test of samples. Requirements for CREEPAGE DISTANCES and AIR CLEARANCES do not apply if samples pass the thermal cycling, humidity preconditioning and dielectric strength tests specified in Annex’s B and C. (Refer to specification)Cemented Joint: Examples of a cemented joint include such treatment as potting, encapsulation and vacuum impregnation, and components or sub assemblies that are treated with an insulating compound that fills voids. Where distances between conductive parts are filled with insulating compound, including where insulation is reliably cemented together with insulating compound, only the requirements for solid insulation apply. Compliance is checked by inspection, measurement and test of samples. Requirements for CREEPAGE DISTANCES and AIR CLEARANCES do not apply if samples pass the thermal cycling, humidity preconditioning and dielectric strength tests specified in Annex’s B and C. (Refer to specification)

As for the zoning, you are right but one of our customer requirements is for our product to be "Ex e". We will get in touch with Intertek Australia, thanks a lot for that.

Kind regards,
Sherry
 
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