I was checking through ASK.com for anything on underground PVC sweep bends – didn’t expect to find a darn thing as it is such a specialised subject – but amazingly found heaps of information.
One particular aspect covered in an engineering-based forum was one that concerns us greatly, but that usually (unless you have to do it) nobody else considers.
What are the best cable-pulling techniques?
Here at Rainbow Electrical Bends, as well as a darn good slippery lube, we sell a pile of Blowline and Megarope for cable pulling, but it still has to find its way into the conduit and then has to be used correctly. Cables have to be pulled in many different situations, with a wide variety of sizes and quality and under vastly differing conditions. As the forum had comments from real experts, I trolled through them all and reproduced the best of them here.
Make of them what you will – I have printed them in good faith but take no responsibility for them, other than to say, “I hope they save you some time, some money and some heartache”.
The question that started it all off was simply: “hi guys, have you tried cable pulling some cable wires in PVC pipes? If yes, what techniques/tips did you use?”
The answers, from at least eight different countries worldwide, were graded into “Good” and “Almost Good”, according to the opinions of the readers, with a pile of them not making the grade at all – so I’ll start with the “Good” first. They are . . .
From a Brit expatriate, based in Spain, came these points –
- Don’t try and pull more than 3 bends!! After 3 it starts getting hard.
- Careful if you are pulling cables when there are existing cables in the tube! If you pull too hard, the friction can burn through the insulation of the other cables leading to short circuits!
- Best use quality cables, some cheap cables tend to burn through very easily while the better quality cables have a dry lube coating!
- If the cables become stuck, pull them the other way a bit and then give a sharp tug forward again! Normally cables only get stuck in the bends or at tube joints!
- Before squirting the pulling gel (or soap) in the tube, attach your cables to your draw wire! If you attach them (using tape ) afterwards, the tape will slide right off the cables leaving you to pass the draw wire again!
- Pull and push!
- There are many more, like choosing the right draw wire and fishing from both ends but I’m not going to give all the trade secrets away!
These points came from a guy in Indiana, USA –
- If it’s an empty conduit how do you get the first pull string in there? Wait for it . . . wait for it, yes you use a large vacuum and a cotton ball with a pull twine and suck the first one through. Then attach the rest of the pull wires you will need to pull and a few extra for future use. AND A BIG BOTTLE OR TUB OF SLICKUM. Different names for it around the country but pretty much the same stuff. Just don’t spill it and then step in it or you might beat the wire to the other end.
And from one forum respondent in Sydney came :
- “To connect your draw wire to the cables being pulled in I suggest using Cable Grips like these:
- Also I have never used it myself, but I have heard of talcum powder being used as a lubricant, although I’d recommend wearing dust masks and eye protection as talcum powder can be very irritating if inhaled and or gets in your eyes.”
As a point of interest, those answers rated as “Almost Good” were as follows – sorry, I left out the one suggesting the use of KY-Gel – wasn’t too sure about that!:
From a bloke in Idaho, USA, came –
- the most important step. Pull from high to low elevation, even if it is 2 inches difference.
And finally, from someone, somewhere, with a warped sense of humour who seems to know what he is talking about, even though he claims among other things to be a graduate of Brandenborg University at Lower Lichtenstein, with emphasis on Super High Intensive Training (check those initials and you’ll see what I mean) –
- They make a device called a “tunnel rat” that is a spool of high strength very fine cord that is fired thru the conduit by a nitrogen powered gun. It unspools as it travels down the conduit. Different trade names exist, as well as different manufacturers.
- As for how to pull the wire, it depends on size of wire, size of conduit and length of pull.
- 270 degrees is the maximum turn allowed in most situations.
- I have used a Rigid pipe threader anchored to the floor, with a 2 inch nipple as a capstan drive to pull wire through large conduit, and high powered winches for other situations. Very long runs of large cable require pinch conveyors and rollers to prevent damage to the cable. Cable manufacturers specify a maximum pull on their cable to prevent damage to the exterior as well as gauge change from stretching.
- Lubricant is also standard equipment for cable pulling.
Some comments were useful, but different, such as:
From another Stateside contributor:
- There has been some excellent advice given from other posters. The only thing I can think of adding that a lot take for granted is make sure all your cables are running parallel & not crossing over at any time. When even 1 cable wraps around or crosses over another it creates a lump that will not pull through a bend & will do damage.
And from one who gives his location as sometimes Wales, UK.. sometimes Libya!
- MEASURE YOUR CABLE! The number of times I’ve seen cables pulled in only to find they are short by a FEW inches… Cable pulling can take ages and a lot of manpower and even longer if you have to pull it out again because you’ve cut it too short. Also don’t forgetting the “muppet” factor you now feel, and everyone who pulled the cable is definitely thinking! Measure twice.. cut once!
That’s all for now. We’ll keep our eyes peeled for other interesting topics connected with the industry.
— Don Eade