teflon on cl1 div1
- Thread starter pntdxtr
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- Mission Viejo, CA
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- Professional Electrical Engineer
I think so too.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
Teflon tape does not prevent bonding. It basically just fills in the air gaps on the threads. I am not sure this is a violation. I am not sure it isn't a violation either.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
If you aren't sure, why are you commenting on it? I am sure.
- Location
- Illinois
- Occupation
- retired electrician
What is permitted to be used on conduit threads? Are there products other than Crouse's STL, Burndy's Penetrox E, or T&B's Kopr-Shield that can be used?
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I have no idea Don; I do know any treatment of the bonding path better enhance it rather than just not interfere with it in classified locations. That is the emphasis in 501.30(A) which applies to both Division 1 & 2. However, the OP cited sufficient Code in 250.96 alone to justify removing the Teflon.
weressl
Esteemed Member
I think in the case of Cl. I, Div. 1 environment I would be more concerned with the Teflon tape ALTERING the explosion relief capability of the connection than the grounding continuity. (Not that it is not important, but it would be secondary.)
petersonra
Senior Member
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- Northern illinois
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- engineer
I don't see how those paragraphs say anything of the sort. Perhaps you could enlighten me as to what wording prohibits teflon tape.
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petersonra
Senior Member
- Location
- Northern illinois
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- engineer
One would think the explosion relief issue would only come into play with covers of XP boxes, not conduit fittings.
It seems to me you have a choice. I don't see how teflon tape is all that similar to paint in any case.
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- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
If it could even possibly affect the bonding path, it violates 501.30(A). If it coats the thread at all with a nonconductive material (that's how it is similar), it violates 250.96.
weressl
Esteemed Member
Your reasoning for this is....? In an explosionproof installation threads are the pressure relief AND flame arrestor paths, hence the number of threads - 7 - required to be engaged on any threaded fittings, connections.
Anti-seize/never-seize? It's conductive, typically nickel or copper based, and is functionally the same as a thread lubricant.
wallyworld
Senior Member
I always thought it was 5 threads engaged
The rule reads 4.5 for an exception. (05 Nec) 500.8(D) Ex.
Standard is about six to seven.
Teflon tape? Needs to go away.
C1D1 piping is all about limiting flame propagation and expansion, from within, or from outside the pipe, box etc. Threading is based upon allowing the gasses time enough to cool in travelling the distance involved. That is why we use tapered threads, and thread lube (kopr shield) to enhance grounding by reducing corrosion of the base metal (the pipe). Look at the lips of an explosion proof box. There is a reason they are that thick, and can cost thousands of dollars to purchase.
Standard is about six to seven.
Teflon tape? Needs to go away.
C1D1 piping is all about limiting flame propagation and expansion, from within, or from outside the pipe, box etc. Threading is based upon allowing the gasses time enough to cool in travelling the distance involved. That is why we use tapered threads, and thread lube (kopr shield) to enhance grounding by reducing corrosion of the base metal (the pipe). Look at the lips of an explosion proof box. There is a reason they are that thick, and can cost thousands of dollars to purchase.
See the 2008 HB, last paragraph in the commentary.
"The use of Teflon tapes or joint compounds on conduit threads may weaken the seal fitting and interrupt the equipment grounding path. Cracks have developed in fittings during hydrostatic testing in which these materials were used."
My humble opinion. If you received equipment from a skid manufacture that has teflon tape on the conduit threads it means it was fabricated by pipe fitters or plumbers, not qualified electricians. Better make sure your fittings are all conduit fittings and verfiy there are no black iron pipe fittings mixed in.
I have seen it happen.
"The use of Teflon tapes or joint compounds on conduit threads may weaken the seal fitting and interrupt the equipment grounding path. Cracks have developed in fittings during hydrostatic testing in which these materials were used."
My humble opinion. If you received equipment from a skid manufacture that has teflon tape on the conduit threads it means it was fabricated by pipe fitters or plumbers, not qualified electricians. Better make sure your fittings are all conduit fittings and verfiy there are no black iron pipe fittings mixed in.
I have seen it happen.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Kudos to all the responders that pointed out the potential of significantly altered explosion relief characteristics. I have long been aware of the grounding issue, but never gave the relief issue any real thought – although it is obvious once it is considered.
Some Ol’ dogs can still learn a thing or two - thanks
Some Ol’ dogs can still learn a thing or two - thanks
Fulthrotl
~Autocorrect is My Worst Enema.~
- Occupation
- E
there is a product called led-plate, which is similar to kopr-shield, with lead
instead of copper. it's used a lot in the refineries in cl 1 div 1 occupancies.
just a messy anti-sieze that is electrically conductive, and works on a number
of things.... really bad on carpeting if you get some on the bottom of a shoe.
a spoonful will cover a football field, with some to spare. :smile:
Is that the red junk that gets really hard after 40 years? My guys had a heck of a time changing stanchion mount lighting tophats recently that had some sort of red junk on the threads.
I can't remember if it was an OZ-G or Appleton catalog, but it showed at the fittings the threads are considered an explosion exhaust component, allowing the gas to cool and exit without being an ignition source.
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