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#134455 - 11/11/02 09:59 PM Steel Conduit and Mineral Insulated Cables
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Just wondering?, are steel conduits still used in your country?.
We are still removing them from buildings, over here.
Also, are Mineral Insulated, Metal Sheathed
(Pyrotenax), used in your country, for high temperature applications?.
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#134456 - 11/11/02 10:24 PM Re: Steel Conduit and Mineral Insulated Cables
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Ungrounded semi-rigid steel conduit was the norm 50 years ago. It's still in place today. (You are allowed to replace the wires without grounding it, as rewiring is not considered a major change to the installation) It went out of use entirely when plastic conduit (rigid) and plastic boxes were introduced.

However, rigid steel conduit is still common in extremly exposed environments such as walls of city buildings and subways.

(Plastic conduit is rarely used on walls. If you need to put a cable outdoors, the best choice is to use metal shielded cable.)

There is a vast range of special cables available. I have never encountered mineral insulated cables, but this is likely to come from my limited experience. The code lists it for 105°C, so I suppose it is to be found somewhere. (Hmmm... Makes me wonder what sauna cable is made of? Saunas are rather common, and there is a special cable for them)

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#134457 - 11/12/02 02:31 PM Re: Steel Conduit and Mineral Insulated Cables
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Heavy-gauge steel conduit is still readily available in Britain. Some homes dating from the 1930s era still have it, although today it's way too expensive and labor-intensive for residential applications, except in limited amounts for outdoor runs etc.

Mineral-insulated cable is also still available (generally called m.i.c.c. here - Mineral Insulated, Copper Clad). I seldom see it as I don't get involved with anything above light commercial, but I did pull some old m.i.c.c. out of a house a few months ago. Probably accounted for by the fact that the building had been used as a school in the past and it was above the old boiler room area.

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#134458 - 11/12/02 05:03 PM Re: Steel Conduit and Mineral Insulated Cables
David UK Offline
Member

Registered: 10/03/02
Posts: 134
Loc: Inverness, Scotland
Yes both are still used, but dying out.
Steel conduit is increasingly being replaced by plastic conduit, mainly due to cost & speed of installation.
M.I.C.S., commonly known as "Pyro" here, used to be the only cable suitable for fire alarm sounders. Now various fire performance cables such as; Pirelli FP range, AEI Firetec & Draka Firetuf have superceded Pyro in this area. Once again cost & installation speed are the main factors influencing the choice.

I am currently wiring a new workshop / bronze casting foundry.
The installation in the workshop areas is galvanized steel trunking run on the walls at 2.2M, with heavy gauge PVC conduit drops to sockets, switches etc.
This worked out the most cost effective solution, providing adequate mechanical protection & allowing future additions to be made with minimal disruption.
Fire alarms will be wired in Pirelli FP cable.

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#134459 - 11/13/02 08:20 PM Re: Steel Conduit and Mineral Insulated Cables
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
David,
I have seen that Pirelli FP cable advertised in my Radio Spares Catalouge, what is it like to work with?
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#134460 - 11/18/02 05:41 AM Re: Steel Conduit and Mineral Insulated Cables
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
In Austria I've never seen anything but steel clad cardboard conduit. The cardboard was asphalted, always ungrounded. Was in use from (probably) early 1900s to 1950ies. Then it was superceded first by rigid plastic ("EVILON") and in the early 1960s PVC flex as it is still used today. Evilon is the most common conduit type for damp area surface mount work.
Still lots of the old conduit around (rewires hardly ever bother to rip out the old conduit if it is still usable), however, it's hard to work with that type of conduit. Exterior diameter is usually 16 mm, so due to the thick wall it's pretty tight, plus the tar paper surface is pretty rough. Good to have some soap handy when pulling wires!

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#134461 - 11/27/02 10:26 PM Re: Steel Conduit and Mineral Insulated Cables
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Texas,
I'd hate to see one of them ashpalted cardboard cables blow, if it faulted.
What sort of voltage do you pump through these?.
Mind you, coming from a country that uses
Nitrogen gas-fed and oil-fed, paper insulated cables, I think I should be the last person to ask about wierd cables.
Your thoughts please-
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#134462 - 11/28/02 03:30 AM Re: Steel Conduit and Mineral Insulated Cables
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Some very large telephone cables are fed with low-pressure nitrogen gas to keep moisture out as well.

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#134463 - 11/28/02 03:56 AM Re: Steel Conduit and Mineral Insulated Cables
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
That asphalt stuff isn't quite inflammable, it stands pretty high temperatures under fault conditions. That stuff was definitely used for residential/commercial 220/380V lines well into the 1950ies. Our main appartment feeders in the house are pulled in such conduit, at least partially. Some of that stuff has been replaced with PVC flex and new color coded wires. However the electrician told us we'd have to upgrade them in the near futuure due to new requirements (60A 3ph service for 9 appartments, still beter than the old 20ies 25 A DC service)

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#134464 - 11/28/02 10:00 PM Re: Steel Conduit and Mineral Insulated Cables
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Our DC Link cable between the Islands, here in New Zealand(500kV DC) uses Nitrogen gas to keep them cool, not sure what they do with the gas, once it comes out in Wellington,but it must be pretty hot, with all that power we are sending up there, to run all their Cappucino machines and Luxury apartments.

[This message has been edited by Trumpy (edited 12-28-2002).]
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