Having seen the thread about street rewiring, I wondered how the joints are done from the main supply cable going down the street, to the individual houses. I am thinking they would to it without cutting the main cable - like when you wire a ring circuit looping at each socket to avoid a potential break of the ring at the sockets. Obviously there may be different methods depending on the cable type, but ... Anyone know how it is done ? Simon.
done from the main supply cable going down the street, to the individual houses.
wire a ring circuit looping at each socket to avoid a potential break of the ring at the sockets.
I once spent a weeks work experience with the underground jointing team at the local electricity board.
One such job involved connecting new houses to an existing 3 phase cable that was feeding soome houses both before and after.
first its locate cable using voltage detectors. turn off power and dig hole.
The cable can be thought of as a three core cable with an outer neutral shell.
The cable is carefully cut to expose the neutral outer shell and three inner phase conductors.
The cable was they spread apart so that there was air between all conductors.
You then use a blow torch & solder to attach the branch cable (which looks like armoured cable) the inner wire of the branch cable to one of the now exposed three phases. The skin conductor is then soldered to the neutral of the underground cable.
There is a kit which is basically contains two plastic shells, plasticene and a epoxy resin & hardener.
You apply the two plastic shells around the thick cable so as gto completely cover it. Make a small hole for the new branch cable thats just been attached.
Putty/plasticene is then applied at the cable - shell gaps.
The epoxy resin and hardener is then mixed in a bucket and then poured into the now assembled closed shell which has an opening at the top for the expoy resin & hardener mix to be poured into.
The men then have a cup of tea or lunch.
Once the resin has hardened, the hol eis then back filled and the gang move onto the next house.
cables that have fractured/shorted/open circuited are repaired in a similar way. cut out a couple of metres of cable on both sides of the fault, and use a new length of cable plus two jointing kits to connect up the two ends of the old cable.
Stephen.
The cup of tea is obviously a very important part of this process.
Brian
...
JGH
Seem remarkable similar to what I saw when a student with SSEB in 1961. Only change was that hot pitch was poured into the shell - which was made of lead. The shell as then solder-wiped to the cables.
Why the change from cheap pitch to expensive epoxy?
NT
Pitch leaks out, particularly if the cable runs warm. Also more of a H&S risk handling it. The resin cost is probably insignificant by the time you've added in the callout charge, digging the hole, etc.
Primarily because the cable materials changed - old cables, paper insulated, lead sheathed, steel tape armoured. Paper impregnated with mineral oil, amouring bedded in hessian and pitch coated.
Now it's various man-made types of insulation which don't sit too happily with hot pitch. And as AG mentioned, H&S issues.
It's no coincidence that the joint box filler takes the same time to set as it takes to make and drink a mug of tea. (Insert smiley here)
On Tuesday 19 February 2013 07:50 Broadland Wanderer wrote in uk.d-i-y:
And you'd have to run a pitch boiler - which is not really convenient for a job here and a job there.
Money. The cable was all paper insulated and lead sleeved. The old system used cast iron boxes lots of lead, pitch, soldering, wiping and all the insulation was replaced with tapes that had to be heated also.
It was all highly skilled work, it would take a day to do each joint, with a couple of people. never mind all the searching, digging and reinstating. Most of the work was done live. I send weeks as an apprentice on the job and went on a course years ago. But never did it for a living.
The new plastic sheathed cable came out shortly afterwards so it was all redundant knowledge except for repairs.
The new resin joints, well it takes a few hours instruction. At the end of it a better job too.
No, compound bucket and gas burner. FWIW, A57 compound. Pouring temperature
120-130 C.
You weren't the comedian who thought he could wipe a plumb without a catch cloth were you?
On Tuesday 19 February 2013 13:55 Broadland Wanderer wrote in uk.d-i-y:
Well, what I meant was you'd have to let it cool down before shoving it in the van, and heat it up again at the next job - presumably?..
I was not alluding to it being the same size boiler as roofers use (unless you where joining *really big* cables ;->
BTW - do they still use sold if lead served cables are being repaired? And do they still ladel the solder on (2 ladels)?
Cool a bit, but storage on the vans allow for buckets to be contained properly.
Tinman's solder for copper joints, can't remember what is used for aluminium, plumber's metal for wiped lead joints. Yes, ladle to ladle for soldering, ladle onto catch cloth for a wiped joint on lead.
Cable jointers were always a bit scathing about plumbers, on the grounds that it's very easy to melt away the lead sheath on a cable, so the skill level for cable jointing was always thought to be much greater.
Nice link! I see they still have their yellow compound, too - I remember packing loads of this around a box when we were trying to cut down vibration...
On Tuesday 19 February 2013 15:05 Broadland Wanderer wrote in uk.d-i-y:
Most interesting - thank you :)
h cloth were you?
Heh Heh! We all had "moleskin" cloths. Dunno if they were made from actual moles or not.
ium, plumber's metal for wiped lead joints. Yes, ladle to ladle for solderi ng, ladle onto catch cloth for a wiped joint on lead.
that it's very easy to melt away the lead sheath on a cable, so the skill l evel for cable jointing was always thought to be much greater.
Do you remember that horrid red flux that they used with aluminium cables? I can recall the smell of the fumes now. Found out years later it was carcinogenic.
cloth were you?
Nope! Heavy cotton.
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