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Re: Rubber beading on high voltage cable insulation
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TTman
Jul 20, 2022, 6:02:07 AM7/20/22
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On 20/07/2022 07:53, Mike Mocha wrote:
>
> Hey all,
>
> Just curious what you think about this. The photos at the link are
> showing large gauge wire used on a vintage 600 VDC rail vehicle. We're
> talking 1930's electric streetcar technology. Basically 600 VDC connected
> to a knife switch, then to a rotating manual controller which you
> partially see in the photo. The rotation of it sets up the series and
> parallel stages to the traction motors.
>
> We see this weird rubber beading occurring on the outside of the older
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
>
Bits of melted tar maybe...
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>
> Hey all,
>
> Just curious what you think about this. The photos at the link are
> showing large gauge wire used on a vintage 600 VDC rail vehicle. We're
> talking 1930's electric streetcar technology. Basically 600 VDC connected
> to a knife switch, then to a rotating manual controller which you
> partially see in the photo. The rotation of it sets up the series and
> parallel stages to the traction motors.
>
> We see this weird rubber beading occurring on the outside of the older
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
>
Bits of melted tar maybe...
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Peter W.
Jul 20, 2022, 6:32:46 AM7/20/22
to
> Bits of melted tar maybe...
That was (is) a potting material commonly used 'back in the day' over taped connectors. Now, my electrical experience 'in the field' goes back to 1972, and the electrician I worked for had a metal pot with a screw-lid & brush cap that he used when we ran cables to stubs in a conduit where there might be water involved. The cables would be bugged to the stubs, taped, then tarred, then taped again.
Peter Wieck
Melrose Park, PA
Dan Purgert
Jul 20, 2022, 7:10:38 AM7/20/22
to
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Hash: SHA512
Mike Mocha wrote:
> Hey all,
>
>[...]
I've worked on restoring, the insulation is essentially some kind of
cloth dipped in tar (pitch, whatever).
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--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860
Hash: SHA512
Mike Mocha wrote:
> Hey all,
>
> We see this weird rubber beading occurring on the outside of the older
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
If it's anything like the HV wiring in 1940s/50s era locomotives that
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
I've worked on restoring, the insulation is essentially some kind of
cloth dipped in tar (pitch, whatever).
-----BEGIN PGP SIGNATURE-----
iQIzBAEBCgAdFiEE3asj+xn6fYUcweBnbWVw5UznKGAFAmLX4r8ACgkQbWVw5Uzn
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=V/lA
-----END PGP SIGNATURE-----
--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860
chr...@privacy.net
Jul 20, 2022, 10:40:42 AM7/20/22
to
On 20/07/2022 07:53, Mike Mocha wrote:
>
> Hey all,
>
>
> Hey all,
>
> Just curious what you think about this. The photos at the link are
> showing large gauge wire used on a vintage 600 VDC rail vehicle. We're
> talking 1930's electric streetcar technology. Basically 600 VDC connected
> to a knife switch, then to a rotating manual controller which you
> partially see in the photo. The rotation of it sets up the series and
> parallel stages to the traction motors.
>
> showing large gauge wire used on a vintage 600 VDC rail vehicle. We're
> talking 1930's electric streetcar technology. Basically 600 VDC connected
> to a knife switch, then to a rotating manual controller which you
> partially see in the photo. The rotation of it sets up the series and
> parallel stages to the traction motors.
>
> We see this weird rubber beading occurring on the outside of the older
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
>
Looks like heat damage to me!
> wire insulation. I'm not sure what that insulation is made of or how old
> it is. This only seems to occur on the older wires. The newer NFPA
> compliant wires don't have this symptom.
>
> What is it and what causes it? Any theories? Thanks.
>
> https://imgur.com/a/OqHQV8U
>
Possibly caused by resistance heating in a tarnished/corroded
connection? I would disassemble, clean, grease and remake the
connections.
Replace any damaged cable along the way: If I am right, there will be
some. If I am wrong, there may not be :-)
HTH, Chris
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