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Author Topic: Aluminium cabling  (Read 8356 times)

oddlegs

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Aluminium cabling
« on: March 18, 2012, 07:03:29 PM »

My background is in electrical/electronic engineering and I haven't been directly involved in telecoms wiring for 45 years or more.
I thought I might share my thoughts on aluminium wiring as it has affected me.
I believe aluminium wiring was first used during WW2 when large numbers of services camps were built using pre-fabricated methods. Because of the wartime shortages of copper a decision was made to use aluminium for wiring the camps.
The wiring fittings then (as now), used brass tube connections with brass grub-screws to terminate the wiring.
A series of serious fires caused the abandonment of the experiment.
Aluminium is a reactive substance and the reason it doesn't rapidly disappear is that it rapidly forms an oxide layer on it's surface which protects it from further corrosion. This oxide layer has insulating properties and when it is built up by processes such as anodising it can produce a hard surface that is a very good insulator.
A few years ago insulating washers of anodised aluminium were used between semiconductors and their heatsinks and claims of 1000 volt withstand were made. What chance a ADSL signal ?
Aluminium tends to creep much more than copper from under the pressure of a tight connection.
Aluminium is of course used for heavy power distribution cables but where it terminates to copper or brass connections, special bi-metal crimps are used. These have an aluminium socket to crimp onto the cable which is welded in an high-tech factory process to a copper socket or lug for the copper connection. Stranded aluminium with a steel core for strength is used for the Grid & Supergrid lines carried on lattice towers.
Above ground lightning conductors are normally aluminium nowadays but the connection that goes into the earth to the earth rod is always copper with a bi-metal joint just above the ground.
The smallest cable that can be used in a building according to the regs is 16 mm2 and only then if properly terminated.
During the 1970's the African copper crisis caused a shortage of copper and a few new houses were wired with copper-clad aluminium but this caused all sorts of problems because the grub-screw connections broke through the thin copper coating.
Fittings were produced that used a flat claming plate connection like in the original BT linebox A & B line connections.
Unfortunately electricians continued to use the more common fittings.
Hopefully all this copper-clad will have been replaced by now. If they did cause fires they were probably put out by the leaking stainless steel plumbing systems that were installed at the same time.   ;D
I know the BT scientists maintain that aluminium wiring doesn't present a problem but unless they use gel filled bi-metal crimps (fitted the correct way around) then I think that aluminium is always going to cause problems.
I don't know what the maximum length of BT undergound cables is but it occurs to me that there must be many joints in the average cable run between exchange and consumer. I would think the worst case scenario would be several changes of material in the run.
I hope that BT desist from installing aluminium in future and feed our broadband and POTS along a nice bit of fibre.   ::)
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Black Sheep

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Re: Aluminium cabling
« Reply #1 on: March 18, 2012, 08:24:28 PM »

Is that a 'Cut & Paste' jobby, Oddlegs ??? It's just that the opening line doesn't read right ?? "I haven't been directly involved in Telecomms wiring .......... " ? I haven't been involved in the Russian Space Programme for the last 45 years, but I wouldn't go out of my way to make people aware of this. ;D ;D ;D

I wish I could 'Cut & Paste' information made available to BT/OR folk, relating to info on Ali cable. But, I can't due to company policy. I can tell you that (and I've never said differently) Ali is a worse conductor than Copper, but when it was introduced into our networks (due to pricing factors) in the 1960's, the planners of the time would install a higher gauge Ali cable to compensate for where it would normally be a Copper cable.

Insertion Loss measurements taken from both types of cable, over the same length showed a 2dB difference. Again, I reiterate ......... we all know Ali is worse than Copper, and when we come across faulty lengths, they are replaced by todays choice of cable ..... Copper.

It is what it is.
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oddlegs

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Re: Aluminium cabling
« Reply #2 on: March 18, 2012, 09:10:44 PM »

Is that a 'Cut & Paste' jobby, Oddlegs ??? It's just that the opening line doesn't read right ?? "I haven't been directly involved in Telecomms wiring .......... " ? I haven't been involved in the Russian Space Programme for the last 45 years, but I wouldn't go out of my way to make people aware of this. ;D ;D ;D

I wish I could 'Cut & Paste' information made available to BT/OR folk, relating to info on Ali cable. But, I can't due to company policy. I can tell you that (and I've never said differently) Ali is a worse conductor than Copper, but when it was introduced into our networks (due to pricing factors) in the 1960's, the planners of the time would install a higher gauge Ali cable to compensate for where it would normally be a Copper cable.

Insertion Loss measurements taken from both types of cable, over the same length showed a 2dB difference. Again, I reiterate ......... we all know Ali is worse than Copper, and when we come across faulty lengths, they are replaced by todays choice of cable ..... Copper.

It is what it is.
No cut and paste involved I'm afraid, all my own thoughts , what I meant to say was that apart from working on a Strowger PBX as a young lad I have no experiance of the telecoms industry.
I'm glad to learn that BT don't use ali cabling any more, from other posts I thought that perhaps it was still being installed.
No Worries  :)
« Last Edit: March 18, 2012, 09:13:43 PM by oddlegs »
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Black Sheep

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Re: Aluminium cabling
« Reply #3 on: March 19, 2012, 02:48:38 PM »

Hi Oddlegs

Yeah, rest assured it's Copper installed for any new/replacement cable. Due to the high price of said Copper, our logistics people have now withdrawn 2-pair Dropwire 10, and only supplying 1-pair Dropwire 10.

If it wasn't for the D-side 'civils' being factored in, it'd be cheaper to FTTP !!  ;) ;D
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renluop

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Re: Aluminium cabling
« Reply #4 on: March 19, 2012, 06:50:26 PM »

..... withdrawn 2-pair Dropwire 10, and only supplying 1-pair Dropwire 10......

Handling two pairs at a time: yes please :D, but seriously this innocent asks what is meant, will it save problems or money long term?
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Black Sheep

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Re: Aluminium cabling
« Reply #5 on: March 19, 2012, 07:34:46 PM »

..... withdrawn 2-pair Dropwire 10, and only supplying 1-pair Dropwire 10......

Handling two pairs at a time: yes please :D, but seriously this innocent asks what is meant, will it save problems or money long term?

Ha ha ...... 'Carry on up the dropwire' eh ?? Ooer missus.

Yeah, that's all it is ...... a cost-cutting excercise. It's 2-way saving (as presented to us) through not only the obvious 'less Copper' aspect, but also some bean-counter has calculated that the less weight on the 2 drums we are expected to carry as van-stock, will return 'x' ammount of saving on fuel costs. Especially when the multiplier is approx 16,000 vans. :)
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Ottersnose

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Re: Aluminium cabling
« Reply #6 on: March 20, 2012, 09:52:35 AM »

Sign of the times I suppose.
 A few years ago that would have been seen as madness as you were more likely to need a second analogue line installing. I still think that its a little shortsighted especially when a simple pair change on the drop must clear a good percentage of line faults.
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Black Sheep

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Re: Aluminium cabling
« Reply #7 on: March 20, 2012, 12:27:36 PM »

Sign of the times I suppose.
 A few years ago that would have been seen as madness as you were more likely to need a second analogue line installing. I still think that its a little shortsighted especially when a simple pair change on the drop must clear a good percentage of line faults.

Yeah, your first observation is correct, but obviously nowadays, single-pair dual-frequency circuits are the norm.

Your second point however is not quite correct. If it is a 2-pair Dropwire and pair 1 goes faulty, then we can not   utilise pair 2 (Unless it's a temporary measure). We can swop a pair if it's Dropwire 14 (4 pair) as this comes under the banner 'Aerial Cable' ..... or multi-core in laymans terms.

If we are found to swap a pair within a DW10 during an audit, we get a 10-point defect (Critical Defect) and then the brown stuff really hits the fan.
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Ottersnose

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Re: Aluminium cabling
« Reply #8 on: March 20, 2012, 01:35:07 PM »

Crikey that then suggests that the second pair is useless unless you're providing 2 circuits?  I suppose it makes the single pair dropwire more sensible after all. I must be getting old - just as well it's my last week in telecoms! (hopefully)
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Black Sheep

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Re: Aluminium cabling
« Reply #9 on: March 20, 2012, 03:51:38 PM »

Absolutely right, which brings us back full-circle regarding the majority of EU's only requiring a 1-pair circuit, hence the downsize of DW10.

Wishing my life away here, but I long for the day when I can print your last comment. ;D Enjoy retirement pal. ;D
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c6em

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Re: Aluminium cabling
« Reply #10 on: March 20, 2012, 04:56:53 PM »

I'd agree with the change to single pair.......at least from where I am in the rural parts.
Most of the damage to the dropwires is by squirrels chewing at the cable where it goes through trees....and if they have damaged one pair in the dropwire then the other will be not far behind  - if not already damaged.

What with dedicated fax lines being removed and broadband/voice now able to co-exist on one line indeed most end users do only need 1 pair.
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Black Sheep

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Re: Aluminium cabling
« Reply #11 on: March 20, 2012, 06:00:24 PM »

Yup c6em, spot on bud.

The only saving grace from 2-pair DW10, was the ability to provide temp service should pair one be faulty and pair 2 still tested OK. If for example, safety reasons dictated a new DW couldn't be erected until a later date, then at least the EU would still have service. I guess the 'Steelies' will now play that particular role ?  :hmm:
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asbokid

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Re: Aluminium cabling
« Reply #12 on: March 21, 2012, 01:27:44 AM »

We were taught that the copper crisis was engineered.. insofar as there was no genuine physical supply shortage of copper... Profiteers in the City of London simply manufactured a crisis to ramp the price of copper, which also had a knock-on effect on the price of copper substitutes including aluminium.

The 1970's was a turbulent period in international finance..  The financier-oligarchy was dismantling the fixed exchange rate system, known as the "Bretton Woods Agreement" which had prevailed since F.D.Roosevelt.  The world, instead, was forced to use 'floating' currency exchange rates.

The 1970s was the beginning of the era of derivative-based speculation.   The world production of copper barely changed throughout the 1970s, yet the metal prices swung wildly as profiteers manipulated them for their own gain.

http://minerals.usgs.gov/ds/2005/140/copper.pdf
« Last Edit: March 21, 2012, 02:59:54 AM by asbokid »
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Black Sheep

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Re: Aluminium cabling
« Reply #13 on: March 21, 2012, 10:55:01 AM »

We were taught that the copper crisis was engineered.. insofar as there was no genuine physical supply shortage of copper... Profiteers in the City of London simply manufactured a crisis to ramp the price of copper, which also had a knock-on effect on the price of copper substitutes including aluminium.

The 1970's was a turbulent period in international finance..  The financier-oligarchy was dismantling the fixed exchange rate system, known as the "Bretton Woods Agreement" which had prevailed since F.D.Roosevelt.  The world, instead, was forced to use 'floating' currency exchange rates.

The 1970s was the beginning of the era of derivative-based speculation.   The world production of copper barely changed throughout the 1970s, yet the metal prices swung wildly as profiteers manipulated them for their own gain.

http://minerals.usgs.gov/ds/2005/140/copper.pdf

Whooooooo !! Illuminati - Zeitgeist conspiracy theories eh ??? One world government and all that. Love it.  ;) ;D
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asbokid

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Re: Aluminium cabling
« Reply #14 on: March 21, 2012, 07:30:24 PM »

Whooooooo !! Illuminati - Zeitgeist conspiracy theories eh ??? One world government and all that. Love it.  ;) ;D

i knew you'd see the light! Now come and join the campaign!   http://davidickeforpresident.com

cheers, a
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