LP gas companies here are installing dielectric unions between the second stage regulator and the house leaving underground piping and tank isolated from the grounding system by a one eight inch thick piece of rubber.I think this is a disaster waiting to happen.I am thinking of lightning strikes.
LP gas piping
- Thread starter Galt
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petersonra
Senior Member
- Location
- Northern illinois
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- engineer
how would removal of the rubber make it less susceptible to lightning damage?
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- Retired PV System Designer
And if the OP is worried about "sparks igniting the propane in the line" there is the small factor that there is no oxygen in the line (one hopes!).
One very long stretch of hazard is that the regulator itself will typically have a vent for pressure relief when necessary, and that will discharge propane from time to time.
I had to add a length of PVC to the vent on one regulator to move the discharge away from a dryer vent. Not a big deal.
no rubber no arc.
petersonra
Senior Member
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- Northern illinois
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- engineer
how do you figure that? lightening jumps from the sky all the way to the ground. why wouldn't it be able to jump across a 1/8 gap?
ptonsparky
Tom
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- EC - retired
?
If he removes the rubber, there will be no gap to jump.
Is there a serious issue that would requie the isolation of the LP line? Literally thousands of tanks with buried copper lines in the state. No isolation.
- Location
- Illinois
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- retired electrician
I will suggest that the dielectric is required by 250.52(B)(1).
ptonsparky
Tom
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- EC - retired
Who is using it as a GE?
It is bonded via the EG. That does not equate to its use as a GE.
IMO just because lightning has to jump that last 1/8 inch does not mean we have a problem.
It is bonded via the EG. That does not equate to its use as a GE.
IMO just because lightning has to jump that last 1/8 inch does not mean we have a problem.
- Location
- Illinois
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- retired electrician
The rule is the reason that natural gas suppliers used a dielectric connection at the building when they were using metallic underground supply lines. It doesn't really matter if you call it a GEC or an EGC connection to the pipe, electrically it is the same thing.
My experience with lightning damage on dairy farms is that if everything made of metal is tied together electrically there will never be any lightning damage the greatest damage occurs when it jumps from something it strikes to a near by neutral or ground this jumping is what seems to cause the most damage in my experience. I don't know maybe an eighth inch gap is too small to cause damage. This is related to the csst issue I think the pin holes forming in the pipe were very near where it crossed something grounded to neutral.
Ditto-that dielectric fitting was to prevent the galvanic corrosion of those metal pipe systems. FWIW, the NFGC considers interior metal piping,other than csst, effectively bonded through the egc of an appliance.
ptonsparky
Tom
- Occupation
- EC - retired
And those systems were miles and miles, not a few hundred feet even for the larger farms I have been on. Most are way less.
Besides the reason don_resqcapt19 mentioned, iirc it is recommended that the dielectric fitting be in place on many lp systems as a guard against both a too small cathodic system and disimiliar piping materials. The way I understand it the cathodic protection would suffice for the underground steel tank, but without the dielectric fitting and electrical isolation the cathodic protection would have to also protect the associated piping system- the size of the cathodic anode would have to be increased. Supposedly, even if the cathode was big enough, it still may not protect against with corrosion problems when any metal pipe material is different from that of the tank.
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