Tight fit or room to spare?

[LeighSawczyn]

Does 6mm2 SWA fit into 25mm Blue MDPE Pipe. The idea being to protect the cable from damp soil or water ingress when it is buried, not for mechanical protection. No tight radii to worry about just a 10-15m straight run.

 

[Knobhead]

Think E54 will confirm this, it’s standard practice to confirm the integrity of the outer serving a few days after the back fill has been done no matter what the system voltage is.

Most of our UG supplies relied on the armour as the earth (no CPC then) to have it corrode away could be disastrous. In reality it never would be that bad as the numerous X linked cables maintained integrity.
We used high conductivity armouring where 1 in 5 armours is tinned copper. These cables are special order, you put one at risk by poor installation methods and there would be all hell to pay.

A sheath test would be normal before the ends were connected. I don’t know what voltage E54 uses but I’ve always used 250V DC between the armours and earth.

 

[Marvo]

We don't always sheath test SWA's but if we do we usually common together all the conductors and the sheath and run 1kV through it which is usually what their ins is rated to.

 

[shanky887614]

we were gutted when there was a split in the sheathing 10m from the end on a 100m run of 27pair 1.5 swa. now that was pain in the arse pull.

in a building rather than burried though

 

[Marvo]

Depending on the damage I'd have probably done a heat-shrink repair on it.

 

[Knobhead]

We don't always sheath test SWA's but if we do we usually common together all the conductors and the sheath and run 1kV through it which is usually what their ins is rated to.

The outer serving isn’t an insulator hence the lower voltage. It isn’t a standard IR test.

 

[Knobhead]

Depending on the damage I'd have probably done a heat-shrink repair on it.

Raychen do a heat shrink repair bandage damn good stuff for localised damage.

 

[ian.settle1]

I agree that it's prob best to put it in a duct, due to sharps/stone in the backfill material but put it in a proper cable duct as Ruston says you wouldn't want people thinking it's a water pipe. Plus if you put it in a a proper cable duct it would be easier to replace should some one have to at any point in the future, you would have a hell of job trying to replace a SWA through a bit of 25mm poly pipe lol

If it has been installed correctly before you backfill the excavation the cable should be covered with a layer of sand to stop the cable being damaged by stones or sharps.

 

[davesparks]

The outer serving isn’t an insulator hence the lower voltage. It isn’t a standard IR test.

If it isn't an insulator does that mean it must be a conductor?

(Please don't shout at me Mr Grumpy Git sir)

 

[Leesparkykent]

If it has been installed correctly before you backfill the excavation the cable should be covered with a layer of sand to stop the cable being damaged by stones or sharps.

for sure, but if its been left up to groundworkers on a site for instance....lol

 

[davesparks]

Then if the groundworkers haven't followed the written spec for the work they'll be digging it all up and starting again at their expense.

 

[Leesparkykent]

Then if the groundworkers haven't followed the written spec for the work they'll be digging it all up and starting again at their expense.

how would you know lol

 

[ian.settle1]

how would you know lol

If the work is carried out correctly the CoW should inspect it to make sure that the sand have be used before allowing the groundworkers to backfill

 

[Knobhead]

If it has been installed correctly before you backfill the excavation the cable should be covered with a layer of sand to stop the cable being damaged by stones or sharps.

Do it properly? Too much trouble for many. Get it in quick and hide it before Tony sees it, that’s where the sheath test came in.
Most of my work involving UG cables was in a quarry. You want sand, how many tonnes? Chatter by the wagon load if needed.
At the foundry we used granulated slag as the infill, again, how many tonnes?

 

[ruston]

Do it properly? Too much trouble for many. Get it in quick and hide it before Tony sees it, that’s where the sheath test came in.
Most of my work involving UG cables was in a quarry. You want sand, how many tonnes? Chatter by the wagon load if needed.
At the foundry we used granulated slag as the infill, again, how many tonnes?

Was on the way but got a dam puncture lol

 

[Knobhead]

If it isn't an insulator does that mean it must be a conductor?

(Please don't shout at me Mr Grumpy Git sir)

Smart arse!

Yes it is an insulator but in the terms of electrical isolation in a cable that isn’t its function. Its function is purely to protect the armourings.

Lucian Nunnes of the Electrotechnica Museum mentioned unserved armoured cable. I’ll be honest I didn’t believe him. He posted these, I couldn’t argue then.

This picture shows unserved tape armoured cables. I’ve not worked on tape armoured since I was an apprentice, like everyone else I finish up with shredded finger ends. The stuff is bloody evil. When you cut it you have two barbs waiting to stab your hand and the joy of razor sharp tapes.

 

[davesparks]

Leatherhead theatre has submains run in unserved armoured cables, I'll take some pictures for you next time I'm in there if you like?

 

[ImpededLoop]

Leatherhead theatre has submains run in unserved armoured cables, I'll take some pictures for you next time I'm in there if you like?

How old do you reckon they are Dave?

 

[davesparks]

How old do you reckon they are Dave?

The building opened in 1969 so they would have been installed in the late sixties

 

[ImpededLoop]

The building opened in 1969 so they would have been installed in the late sixties

Thanks Dave. I've maintained buildings much older than that and never seen unserved cables before so it's interesting to hear about them.

Daft question, but would I be right to assume that they are only for dry areas?

 

[Knobhead]

Leatherhead theatre has submains run in unserved armoured cables, I'll take some pictures for you next time I'm in there if you like?

If you could Dave. You know my interest in the history of our trade.