Re: [TCML] Secondary Coil Form

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

On 9/13/12 7:24 AM, David Rieben wrote:
> I suppose there always is some risk of obtaining PVC with conductive trash in it, since the industry specs don't require pristinely pure materials for the intended application. However, It seems from the collective data from fellow coilers that the actual level of risk of electrical failure is quite small and manageable. I, for one, have never had any issue with the PVC piping material that I have used in all of my TC forms over about 20 years of actual coiling. As a matter of fact, until I "knew better", I never even bothered cleaning off the printed lettering from the surface of the pipe before winding it. I am currently using gray 12" PVC duct pipe (thinner walls than sch. 40) for the sec. form of my Green Monster coil  and it's been performing *pretty much flawlessly for about 8 years now. (I did have one flashover that damaged it and caused me to have to facilitate repairs, but I attributed this more to not wiping down its surface from dust or possible moisture after it sitting
idle for months than to any conductive impurities in the PVC material.) I noticed that Ed Wingate would wipe down the extra coil of his huge maggie before firing her off and I've since employed a "pre-fire" wipe down as normal setup for firing off my coil now. So far, I've had no more secondary failure since doing this.
> David

I would agree with you that it's not a big risk.. a bigger problem is 
the water that might have been absorbed when that big piece of pipe was 
sitting in a puddle.

Even bigger surprise is foam core that looks solid (e.g. ABS DWV..the 
"foam" has such tiny bubbles you can't see them except with magnification).

But even in that case, the voltage stress along the secondary isn't 
huge.  Figure 400kV or so spread over 2 ft.  that's <20kV/inch.

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