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.

 

[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.

 

[Knobhead]

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?

The cables in Lucians photographs are acording to the information are PILC.

Most old PILC cables are first wrapped tarred paper and then a layer of tarred jute. Over this the first layer of armourings followed by another layer of tarred jute. A second layer of armourings over wrapped with tarred hessian. Just to add to the fun it would then be whitewashed to stop it sticking together on the drum.

Stripping it you set off covered in whitewash, followed by tar. The only way to clean the tar off the armours and lead sheath is with paraffin and a blowlamp. By the end of the day you were a fire hazard and reeked to high heaven.
We nearly burnt the EMEB training centre down with a bit of a cock up with the paraffin rags and blowlamp.

 

[davesparks]

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

I will do my best to remember, I think we've got a show going in there in March. The installation is a bit of a shambles at the moment though. As usual the remaining bits of the original installation are well installed etc, but the more modern abortions are a disgrace.

 

[ImpededLoop]

The cables in Lucians photographs are acording to the information are PILC.

Most old PILC cables are first wrapped tarred paper and then a layer of tarred jute. Over this the first layer of armourings followed by another layer of tarred jute. A second layer of armourings over wrapped with tarred hessian. Just to add to the fun it would then be whitewashed to stop it sticking together on the drum.

Stripping it you set off covered in whitewash, followed by tar. The only way to clean the tar off the armours and lead sheath is with paraffin and a blowlamp. By the end of the day you were a fire hazard and reeked to high heaven.
We nearly burnt the EMEB training centre down with a bit of a cock up with the paraffin rags and blowlamp.

Tony,

Thanks for your reply and explanation, it's interesting and much appreciated. My previous workplace had plenty of PILC with the tarred Hessian wrapping, but I've never seen them without it.

Very interesting to hear about the use of whitewash to stop the cable sticking to itself on the drum. I have to admire those people who installed the stuff.

Thanks again

 

[Engineer54]

Any SWA cable that's been installed into a buckshee trench that hasn't had the sharp stones and other debris removed from the base of the trench and then just backfilled with the excavated earth is almost certain to have it's outer sheath compromised!! There are good reasons behind how a cable trench should be constructed with the correct procedures and materials....

Basically the above is unfortunately a description of what normally applies to domestic buried cables, that are not run in a suitable duct. You would be surprised, even when direct buried SWA cables have been run in professionally, how often a sheath test fails!! And yes it does then need to come out, repaired and reinstalled!!

 

[Knobhead]

And you’re not the most popular person in the world when you tell the cable lads its got to come out.

We would get cable contractors if there were many runs. For the odd runs our quarry production lads were great, they’d done the job many times and really did know what they were doing. Believe me, get them together en-mass and it’s a frightening sight.

They were quite happy with a pull as on Wednesday afternoon as the quarry and crusher shut down for maintenance so the ideal time. A pull was overtime for them plus it was “job and knock”. They got the full afternoon’s overtime and knocked off once the job was done. I dare anyone to tell them the cables got to come out again, your life wouldn’t be worth living.