Pitch-covered LOPTxs

[Station X]

In all my years working for "Post Office Telephones", later BT I never ever saw an underground joint filled with pitch. In fact they weren't filled at all, as the joints were designed to be reopenable for maintenance. Can you imagine trying to dig hundreds of wires out of solidified pitch? Some terminal blocks such as those used on poles were filled with wax.

Joints were originally made using lead, as that's what the cable sheaf was made of. Joints were said to be plumbed. Later polythene sheaf was used with the joint being sealed with expanding rubber plugs. These weren't very good and I think that epoxy resins are used today. This used to be called "Putty Plumbing". Small joints are taped with self-amalgamating tape.

Graham.

[af024]

Again thanks for your input guys.

With the difficulty that I've got in sourcing some of this stuff, I am leaning towards the stuff in the tins (assuming it won't damage anything) - well, either that or perhaps dip it in a pint pot of resin (the sort of stuff that you can get from the car garages for fibre-glass etc) - then paint the thing black once set.

Of course I could leave the thing well along altogether and run it with the exposed windings.

What do other people do? Does anyone bother?

Cheers,


Andy

[af024]

In the end I decided to take the bull by the horns, (or was that the LOPTx by it's windings?) and applied some Bitumen Paint (from a company called Palace - bought from my local DIY store). Out of the tin it is in liquid form at room temperature. All I did was apply it directly and waited 24 hours. The finish certainly looked the part and depite a bit of a smell for the first few hours of operation, everything seems to be ok. The paint complies with BS3416:1991 which is the Specification for Bitumen-Based coatings for cold application, suitable for use in contact with potable water.

Before I braved it, I mega-tested a dried-up test dolup of the stuff. It was way above 20 Megohm (right off the scale), so all was well electrically.

There no adverse affects (at least not yet). If anything transpires I'll let you all have an update.

Now where did I put that photo ....

Cheers all,


Andy

[Heatercathodeshort]

When I was a kid in the early 60's I used to rewind lopt's. The firm used to get the pitch free from a company called BERRY WIGGINS from up north somewhere. They used to supply us with what today would be called I suppose 10 litre can sized blocks for us to 'evaluate'. I can still remember the tar covered Foden lorry turning up in the road and the friendly driver rolling a few drums off the back. He was covered in the black stuff ! They supplied a short 'questionaire' to fill in, melting temperature, insulation properties etc.
I used to wind a new overwind, tie it off and then fix the former over a short length of dowel. This was then placed across an old style OXO tin with two slots cut in the sides to the correct depth of the 'tyre' The pitch filled tin was heated over a gas ring and when soft enough the dowel complete with former was 'rolled' in the slot, repeating until the tyre was thick enough. I wonder what they would say about that today and I was only 13 ! Happy days. Regards JOHN.

[af024]

Good grief John, sounds like one of my experiments in the garage! I can smell the tar from here!

I wonder if anyone has proved (or indeed disproved) insulation degradation from pitch? It's just that I have two sick Bush TV125 LOPTxs which are both pitch-covered. I don't suppose you'd like to re-live those happy re-wind days do you? Only joking - it looks like a real nightmare. I think I'll persist with the trippler idea on the 125s.

Best regards,


Andy