Why STEEL in SWA?

The steel is because steel is considerably stronger than copper and is a lot cheaper. In principle, there is no reason why you could not terminate this like split con, but you will get “howls of derisive laughter Bruce” from some posters! If you want to do this the best method is a suitably sized crimp tag bolted to the metal box and a stuffing gland of course as a mechanical anchorage. However, as many people don't have large crimps and tools available and access may still be a problem, the brass glands are probably just as easy.

Alternatively, you can put the gland on the cable before you thread it into the difficult access position, which is my preferred method, it just needs a bit of planning and a larger drill for the hole.

You would not want to use my big crimpers in the back of a cupboard.

I agree with davezawadi here, I also choose to fit the gland to the cable first, then you only need to add the back-nut to the gland, which is usually easier. 
 

Regards,

Alan. 

AJJewsbury: 
 

..

That might feel like it's going to be more expensive (copper instead of steel), but as most people use and extra core in SWA for c.p.c. in parallel with the armour, it's really just moving that copper to the armour instead - so really it's a saving of the steel with no extra copper required. So perhaps slightly cheaper and slightly smaller o.d. cables.

Any other takers for “CWA" cables?

     - Andy.

i am thinking if you replace the steel with copper having the same CCC then the resultant cable would be similar to braided sheath cable. On the other hand if you replace the steel with copper having the same tensile strength (or rather yield strength) the copper content would mostly be in the sheath and would be horrendously expensive given the price of copper at the moment

132.1.2

Z.

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132.1.2

 

Z.

You mean 132.12? Agreed, sounds a bit of a pain

132.12
Accessibility of electrical equipment
Electrical equipment shall be arranged to provide:
(i) sufficient space for the initial installation and later replacement of individual items of electrical equipment
(ii) accessibility for operation, inspection, testing, fault detection, maintenance and repair.

 Like junction boxes, ‘accessible’  is a bit elastic -  in some quarters anything more than a screw driver is too much,  in other situations an SDS drill and a JCB might be perfectly reasonable access tools for cable replacement.

There is nothing to stop you terminating SWA like split con,  so long as you can do so robustly, though it would be considered a bit rough I think, and the gland does provide cord grip and some environmental sealing, which is nice.

I think SWA is good in tension, for example on catenary, in a way soft copper would not, but I agree in many cases a CWA type of thing would do, and may or may not be easier to terminate. Certainly the traditional gland and banjo seem to be designed to be easy and cheap to manufacture, rather than optimised to make life easy for the user or for blind fit or  limited access. 

As a result there are a lot of badly fitted glands out there in the wild, where the armour is not gripped properly - I have seen a few where it has pulled out totally with a very modest tug.

A wider tolerance of ragged armour end lengths, and a more positive grip  would not involve  difficult mods to the design of the cones and compression nut. You could even add  an extra cross-bar style cord grip, as you do in a plug.

To be sure of a good fitting, I too have been known to put the glands on in advance at low level, even the box on the end as well  in some cases,  before lifting it all into place, especially overhead.

Mike. 

Simple and quick answer to initial question? Cost.

OlympusMons: 
 

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132.1.2

 

Z.

You mean 132.12? Agreed, sounds a bit of a pain

Oh yes, I did mean 132.12. A typo.

Z.

CWA cable? That’s MICC isn’t?