Pulling 16mm SWA through 150 M of conduit?

[1Justin]

Would you attempt to pull 16mm SWA through 150M of existing underground conduit?

A potential job I have taken a look at. I would need to be very sure I could get it through before shelling out £££ on that much cable! (- I already advised the Customer it would have made much more sense to install a cable before filling the trench!).

Facts:
-Conduit was laid about 1 year ago. It is 50mm dia corrugated plastic type, laid in 3 sections of 50M. - I have no idea of the quality and continuity of the two joints, but the Customer will ask the contractor who laid it in.
-Conduit ~ 600mm deep through a semi-wooded garden, no special precautions such as gravel layer or warning tapes.
-Laid pretty straight for first ~60M, then takes a gentle curve perhaps 20 foot radius and turns total about 60 degrees before the end.
-String is through already to start proceedings, so I would be investing first in lots of cord, and a damn great length of blue rope.
-150M of 16mm will weigh about 150Kg!
- I also am aware it only takes a little bit of mud to make a nice plug!


Questions:
Termination for cable nose and ways to stop it snagging?
Friction being the enemy, - so Lubrication?
Best way to fix cable to rope?
Will I need a tractor ...??? (- AKA how hard can you pull safely?)
I haven't seen any longer than 100M from distributors. - Can longer single lengths be got?

Homework:
Ongoing decision as to whether I can get away with 16mm anyhow, but that's work in progress, and not my question here.

 

[JD6400]

Unless I am missing something ? How do people think that pulling an armoured cable of this size which is properly secured , by "hand" whilst being fed at the same time is going to stretch it !? It is unusual to get a labourer to put any more effort in to a cable pull than would be required to pull the skin of a semi dried turd , let alone stretch that cable in my humble experience . And before the outcry of inexperience is heard On the last job which required some pulling a couple of weeks ago , 5/6 of us managed to pull in 95m/70mm 4c , 110m/70mm 4c , 120m/120mm 4c , 145m/150mm 4c , 155m/150mm 4c , 170m/150mm 4c , 180m/185mm 4c , I will admit we did use our quad and winch set up on the last three as we were feeling fatigued by then , but all these took the grand total of 8 hours to complete . The thing that would worry me the most about the job is as Engineer54 has said about the unknown state of the ducts.

 

[GLENNSPARK]

Corrugated plastic pipe, couldn't of chosen a worse design for such a long pull. The other thing is, how strong is this conduit /duct?? Laid at 600mm, if the wall isn't of a sufficient thickness, then there is a good chance the pipe's wall in places could have already collapsed, or starting to collapse, under the weight of the soil.


You're either going to be lucky and the pulling is going to go like a knife through butter, or as i suspect it's going to be a long pull, with one thing cropping up after another and ending up with a stretched cable at the end for all you're trouble. Use plenty of lubricant, ...you're going to need it methinks!! lol!!

its corrugated....so should have held its shape...

 

[Engineer54]

Let me assure you JD6400, inappropriate or DEAD pulling of any sized SWA cable by inexperienced personnel will result in the cable being stretched, and you can take that to the bank. Use of a suitably sized cable sock and correctly set calibrated cable pulling winch, with cable rollers and a free moving cable drum will in most instances alleviate cable stretching.... Start pulling any cable with any other form of tractor/machine and you'll almost certainly stretch that cable.

How many here, would even know if a cable has been stretched or not?? As i say, cable pulling is an art, especially over long distances, were friction between duct and sheath play an important role!! Anyone can pull any size of cable into a duct with enough brute force, what the condition of that cable will be at the end of the operation is a whole different matter!!

 

[Engineer54]

its corrugated....so should have held its shape...

Still depends on the quality and wall thickness. If it's that thin corrugated stuff that i've see in the past, god help the OP!! lol!!

 

[iamelectric]

thanks jd6400 a bit of sense at last , how on earth do these other people get work done i dont know , its a 16mm swa!!!! p.s i have pulled in more swas than most people on here have had hot dinners

 

[JD6400]

As much as I respect near on every point you raise on this forum ! I am afraid no matter how you put it , a couple of blokes "hand pulling" a suitably secured and fed cable of this size , can not stretch it. I have assume that they are just average Joes and not part of the worlds strongest man competition that is of course .

 

[1Justin]

Oh yes the conduit is it's that "thin stuff" Engineer 54!

One other thing I didn't mention. Customer slung MDPE water pipe in the same trench!

What would 528.3 conclude about that? - Since the cable will be down there in 100% humidity anyhow, maybe not a practical problem, but that type of argument could apply to any situation where you'd apply 528.3 so is probably unsound..

 

[HappyHippyDad]

When are you doing this Justin? My tension levels are rising, Its like reading a novel but the last page is missing! I have to know who the murderer is!!!

 

[1Justin]

Ha Ha! I visited yesterday and told the Customer at the time that since I was very concerned about getting the cable in in the first place I would have to "Investigate and consider the options". - No dates and no commitment.

There is plenty of other more accessible "normal" work required on the property which would be a shame to loose out on by being too negative about the "big one". Maybe I quote time and materials with a estimated percentage likelihood for my success. Honesty is the way forward, and no one would be hiding anything here. - That way there is at least a get-out for plan B if it went to worms.

 

[Engineer54]

As much as I respect near on every point you raise on this forum ! I am afraid no matter how you put it , a couple of blokes "hand pulling" a suitably secured and fed cable of this size , can not stretch it. I have assume that they are just average Joes and not part of the worlds strongest man competition that is of course .

Sorry, but your statement above, now comes into question ''(let alone stretch that cable in my humble experience)''!! Just how strong do you think 16mm SWA cable is against a couple of labourers that would be jerking and god knows what else to pull that cable in over a 150 meters, what with the cable itself weighing in at around 150/160Kgs.... Believe me 16mm SWA can be stretched quite easily, as well as physically damaged by any form of unsupervised dead weight pulling!! This cable could possibly fly in with no problems at all, and i hope it does. The difficulty comes when there is a problem, and what is done to overcome that or those problems...


As for iamelectric's statement, You have probably not come anywhere close to being involved in pulling more SWA cables than most of the older guy's on this forum. For a start, this project alone, has several Kilometres (if not miles) of ducted and direct buried cables. That would be for both MV and LV SWA cable as well as god knows how many signaling. As i say any fool and his dog can pull cables through a ducted system, given enough brute force, but at what cost to the cable, is another matter?? The bottom line is ''you need to know what you're doing and know the limitations of the cable you're pulling!!

 

[1Justin]

But there is a lot of quite hard steel in that cable, In my book that's damn strong stuff and hard to stretch, but I appreciate your answer. So (..just say) the cable stretched by a fraction of a percent, - given the margins of safety, (for example 120% for current handling built into the most common interpretations of BS7671), would that be a problem?

 

[Engineer54]

Oh yes the conduit is it's that "thin stuff" Engineer 54!

One other thing I didn't mention. Customer slung MDPE water pipe in the same trench!

What would 528.3 conclude about that? - Since the cable will be down there in 100% humidity anyhow, maybe not a practical problem, but that type of argument could apply to any situation where you'd apply 528.3 so is probably unsound..

Not exactly an ideal situation, but shouldn't be of that much concern if this a smallish water pipe and isn't under too much pressure. Here the main concern is physical damage to the cable, caused by pressure movement of the water pipe after a rupture/burst at say a coupling, or a thrust block failure etc,etc.

 

[GLENNSPARK]

When are you doing this Justin? My tension levels are rising, Its like reading a novel but the last page is missing! I have to know who the murderer is!!!

who killed the cable?
it was Mr. green....
in the woods...
with the lead pipe...

 

[Octopus]

I'm in Surrey too, on the basis that you try and pull the SWA through can I come and watch?

 

[1Justin]

Yes please do. - Provided you bring your running spikes and leather gloves.