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Re: Help please - info on big CDE pulse caps?

Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>


Leave 'em be. It sure sounds like they presently contain mineral oil, and (unless the oil is heated to well over 100 degrees C), they should not represent a fire hazard. Shell Diala-X or AX IS fundamentally mineral oil, so there's no benefit in changing out the oil. You may want to top it off a bit though.

Best regards,

-- Bert --

Tesla list wrote:

Original poster: FIFTYGUY@xxxxxxx
Just a follow up - thanks all for the advice so far.
The ".15 MFD" means .15 microFarads.
A few of ya'll voiced your concerns (rightfully so) that these old caps might contain PCB's. I'd like to state here (semi-publicly) that they would appear to NOT be PCB filled.
The gummy accumulation at the base of one insulator was, as Jim Lux guessed, simply gummy old oil. They slosh when shaken, so the oil still inside is quite thin (even at 45 deg F ambient) - not a viscous impregnation, as I understand PCB's used in caps tended to be.
Sample oil has very little aroma, and what faint smell is there resembles fuel oil.
Sample oil floats on water. Even after emphatic attempts at mixing it all stays on top.
Sample oil supports combustion - vigorously! Burns with the typical hydrocarbon blue flame with yellow tops. No green tint at all. Hisses and pops flaming droplets of oil everywhere. Smoke has typical fuel-oil smell, no acridity/bleachy smell at all.
However, this puts a new light on things. Catastrophic failure may constitute a serious fire hazard. Perhaps they should be drained and refilled with modern transformer oil? Would Diala mix with, say, residual fuel oil or mineral oil, or would it cause more problems than it would prevent?
-Phil LaBudde