Asbestos in a cable?

tigerturnings · 3 Dec 2006

Hi all,

I was recently offered a Startrite Mercury Mk II drill and happily collected it. Today I started cleaning it up a bit and part of the process was to fit a new plug. The mains flex is a rubber-sheathed type and I guess it may well be the original factory fitted one.

I got as far as stripping the outer insulation of the mains flex and then noticed some off-white stranded material was included with the cores. It occurred to me that it may have been asbestos, and a quick google says asbestos was used in some cables in the 70s. I wetted the cable end immediately in case it is, and took a photo of the (now damp) strands. Can anyone identify whether it is indeed asbestos? If so, what would be the best way to proceed?

Also - it is a single phase machine yet there are four cores in the flex. The previous owner had paralleled the live and the mdf-coloured one together in the plug. This works fine but does anyone know why the machine has this extra wire?

Cheers

Neil

Adam · 3 Dec 2006

I have to be honest, I always thought it was chalk. You will need to do an internet search to confirm that though.

Adam

DaveL · 3 Dec 2006

It was common practise to put cotton fillers into cable if the final sheaf was going to be round. The cotton was often covered in chalk dust to act as a dry lubricant allowing better flexibility of the finished cable. They use a plastic filler on modern cables.

I have no idea from just looking at your picture what the packing is but one way to test it is to try and set fire to a bit. You need a dry bit, if its cotton it will burn if its asbestos you won't be able to light it.

Nigel · 3 Dec 2006

I would agree with Adam the powder (chalk) is used to lubricate the flexing of the flex and to prevent cores sticking to each other during manufacture

The fourth core could be an indication supply to the NVR switch downstream of the switch ie at the motor to indicate a circuit problem at the motor and trip the NVR
On most add on NVR switches unplugging the machine from the out put while running will not trip the NVR switch as it only monitors the incoming supply
You would need to test out the cores with a multimeter but in my experience the spare core is usually connected to the neutral

Nigel

tigerturnings · 3 Dec 2006

Thanks for the replies and reassurance everyone.

DaveL, thanks for that test. I don't know why I didn't think of it myself. I took a (still damp) sample and held it in pliers in a blowlamp flame; after a while it burnt, albeit slowly - it went black then eventually turned to a grey powdery ash, so it can't be asbestos. I guess that behaviour agrees with the cotton/chalk consensus.

Nigel, that's a possibility I hadn't considered; I'll test it with the multimeter when I next work on the machine.

Cheers

Neil