Pulling cable through conduit can be a high-anxiety job. Large pulls of four or five cables can weigh up to 4,000 lbs. Even on these large pulls, there are several things contractors can do to make them quicker, safer and easier. This product blueprint outlines several ways the end-user can simplify pulls.
Use quality stands to support reels. Quality stands and spindles work together to help eliminate back strain, save set-up time, and minimize pulling problems from unruly reels. Reels of wire can be extremely heavy and may require two or more workers to lift them onto reel stands. Contractors often build their own reel stands, which require workers to lift the reel onto the stand. These reels can weigh 300 lbs. or more. It makes sense to use stands that allow you, the end-user, to roll the reel into position, and then jack up the reel with the stand so it can turn freely.
Contractors who use conduit as a spindle for home-built jack stands often have problems with the conduit sagging under the weight of the reel, which affects cable pulling. Also, as reels feed out and become lighter, the spindle may jump off the stand during the pull. When the reel comes off the stand, pulling stops. It takes time to get the pull going again when this happens.
Set stands correctly for even feeding. Reels feed best when they are set in line, but often, space constraints make that impossible. In these cases, stagger the reels in a double configuration or minimize the angle in which the cable must feed from the reels to the conduit.
Consider a cable feeder. Feeding cable is hard, heavy work, and exposes workers to the dangers of back injuries or strains.
Besides, it’s a rather non-technical task that usually involves journeymen electricians who could be putting their training and talents to better use on the jobsite. That’s why cable feeding equipment is growing in popularity.
Relatively new to the market, these units help gather and bundle the wire as it feeds into the conduit. Result: you, the end-user, need only two workers on the feeding side.
One worker applies lubricant and the other controls the feeder. The contractor doesn’t need a guy on every cable pulling it off the reel and one worker organizing it as it feeds into the conduit.
Select the right rope. Using the wrong type of rope can greatly affect the safety and success of a wire pull. Rope selection is critical. Know tensile strength, how friction affects it when used on a capstan and how much it will stretch. You don’t want a rope that stretches.
Ropes that stretch have stored energy that will be released if the rope snaps. That stored energy is like a stretched rubber band. If it snaps, the cable can recoil and injure someone.
Double-braided composite rope is the best choice for pulling. It’s like two ropes in one. It’s a high-strength, low-stretch rope that has good characteristics on the capstan and in the conduit.
Polypropylene rope is often used for pulls, but its low melting point from friction and its stretching ability can cause problems.
Polypropylene rope can get slipstick, which happens when the friction on the capstan actually melts the fibers of the rope and it sticks on the capstan. When there is enough tension to pull it free, it slips. It’s dangerous because it could subject your arms to shocks and increases the chance of the rope overlapping on the capstan.
When you select a pulling rope, choose a type that has the capacity to handle four times the capacity of the puller you are using. For example, if you are using a puller with a 6,500 lb. pulling capacity, you should use a rope with a 26,000 lb. capacity.
Watch the rope. During pulls, the worker on the front end of the system will eventually have to contend with a pile of rope that’s already been pulled through the conduit. Always stand behind the pile of rope and never wrap the rope around your wrist, waist, or feet. When operating the capstan, start with only two or three wraps and increase wraps when the rope starts to slip. If you start with too many turns, you don’t have good control.
Match components based on puller capacity, not weight of wire pull. Like a chain, a pulling system is only as strong as its weakest link. But pullers often use components that are not rated to work together.
You often see a lot of mixing and matching of component capacities during installations. The capacity of the puller should drive all other component selections. Sheaves, for example, are often undersized for the forces they must exert. If the end-user is pulling a 2,000 lb. pull 180 degrees over a 2,000 lb. capacity sheave, the actual load is 4,000 lbs. You can eliminate figuring loads by making sure the equipment matches the puller’s capacity.
Similarly, make sure that mounting points for sheaves can withstand the heavy pulling forces. Anchor to the solid structure, not to the tray or the ceiling grid.
Select the right grip. Wire grips are available in a basket type or a clamp type.
Like sheaves, match the grip capacity to the puller capacity. No matter what your pull weight is, components may get much more strain and the components must be able to take it.
Use sheaves to protect cable. This is very important when pulling wire through trays. Any time the wire makes a turn, it should pass around a sheave. You should also use a sheave every 6 ½ feet for cable weighing greater than 2 lbs./ft. and every 10 feet for cable weighing less than 2 lbs./ft.
Sheaves are also important in manhole pulls where the cable exits one conduit and enters another. Use a sheave to help the cable easily enter the conduit on the other side of the manhole.
Puller Selection and Use Tips
It’s suggested the end-user uses the smallest puller capable for completing the job. Smaller units pull faster than large capacity units, which can greatly affect how fast you can get the job finished.
Safety is another key component to puller selection. When looking at new equipment, look for safety features such as a right-angle sheave to get the operator out of the danger zone when pulling. Some models have a capstan that has a rope ramp to prevent rope overlap. It’s also important to have some sort of force-limiting device built into the puller. Consider how these features make a pull more productive and help prevent accidents.
Mount the puller effectively. Mount the puller to accessories that attach directly to the pull conduit whenever possible. If the puller must be mounted a distance from the conduit end to allow enough cable for wiring, use a floor mounting system that’s designed to take full advantage of the lead anchor you are using.
If you bolt only through the puller, the anchor bolts suffer tremendous bending forces. It’s best to use a mounting bracket that allows the anchors to be tightened completely into the concrete, then attach the puller to this bracket. Make sure the anchor is designed to withstand the forces the puller will exert during the operation.
Establish effective communication. Rarely can the puller operator see the workers feeding cable into the conduit. You must have effective communications at each end. Use walkie-talkies or radios to stay in contact.
Plummer is a senior engineer for Greenlee, A Textron Company. He can be reached at (815) 397-7070.
