Pulling electrical cable through conduit by hand used to be a physically difficult, often frustrating task, but the advent of power pulling equipment has changed the game entirely.
Basic components of power pulling equipment include a frame, power source, a capstan that pulls rope and wire, the mechanism that turns the capstan, and pulling rope. Power pulling equipment, along with various accessories that are considered essential for many pulling operations, has evolved to include features that have greatly increased productivity. Current power puller product lines include pullers in various sizes with pulling forces up to 10,000 lbs.
“Bolt-down pullers are all but extinct,” said Tim Bardin, director of product development, Southwire Maxis. “Quick to set up, high-speed power pullers are the pullers of choice today.”
Even so, successful wire pulls still involve many factors.
“No two cable pulls are ever the same,” said Sumeet Pujari, Greenlee product manager. “Different conduit materials, lengths of pulls, the number of bends, even the site environment are challenges in completing successful pulls.”
Greenlee (www.greenlee.com) offers six power cable pullers with maximum pullback force from 2,000 to 10,000 lbs.
Pujari said today’s pullers are more mobile; many set up in less than two minutes and can be used in virtually every pulling situation. This combination of speed and versatility can increase productivity, equaling more pulls in a day.
“Our new two-speed UT10-2S Ultra Tugger cable puller can shift from high-speed/low-load pulling to low-speed/high-load pulling with a simple double tap on the foot pedal control,” Pujari said. “It has a more consistent speed over the range of the pull, delivering the fastest pulling time for all pulling needs over the pulling ranges to 10,000 lbs. It has a built-in circuit breaker to stop the puller motor if it becomes overloaded. With the mobile VersiBOOM II, there is the combination of speed and versatility for most pulling environments.”
Bardin said Maxis (www.maxis-tools.com) markets pullers with 1,000-, 3,000-, 6,000-, and 10,000-lb. pulling forces; cable feeders; pulling grips; reel stands; and rope.
“The Maxis 10K has been enthusiastically received by electrical contractors across North America,” he said. “The 10K has changed the image of the large, bulky cable tugger to a compact, self-contained unit that can pull twice as fast as traditional power pullers.”
No matter what brand or size pulling machine, rope and pulling lubricant are key components for successful pulls.
Bender said composite polyester is the standard for pulling rope that allows for low stretch and high tensile strength. Rope used for pulls should have a breaking strength at least three times greater than the capacity of the puller being used, he said.
Greenlee’s Pujari emphasized that using the wrong type of rope can greatly affect the safety and success of a wire pull.
“It is essential to know tensile strength, how friction affects rope when used on a capstan and how much it will stretch; a rope that stretches is not acceptable,” Pujari said. “A stretched rope has stored energy—like a stretched rubber band—that will be released if the rope snaps. 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.”
Greenlee recommends using rope able to handle four times the pulling capacity of the puller being used, Pujari said.
He noted that polypropylene rope is often used for pulls; however, it has a low melting point from friction, and its stretching ability can cause problems.
“Polypropylene rope,” he said, “can get ‘slipstick’ 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, which increases the chance of the rope overlapping on the capstan and is dangerous because it could subject operators to shock forces.”
Inspect rope thoroughly before using it. Rope with cuts or frays should never be used. Dirt and grease picked up by rope during pulls can work into its strands, weakening its pulling capacity. Like chain, rope is only as strong as its weakest point. Pulling specifications apply only to new, undamaged rope without kinks for splices. If a rope breaks under tension, energy it carries will be suddenly released, and the whipping action can cause considerable damage, serious injury or even death.
Maxis’ Bardin said it is important that the conventional cable be lubricated correctly. However, Bardin said prelube and no-lube cables now are available, calling them some of the greatest contributions to the electrical industry in the past three years.
“More contractors are using wire and cable products that require no lubricants and eliminate the complications and mess of lubrication inherent with traditional cable installation methods,” he said.
Pujari said Greenlee’s suggested guideline for determining the quantity of lubricant needed for a pull is to multiply the length of the cable run in feet by 0.0015 times the diameter of cable in inches, with the resulting number being the gallons of lubricant needed.
The Greenlee UG5 Ultra Glider automatically applies cable lube during cable installations. Pujari said the system applies lubricant more evenly around cable than can be done by hand. It eliminates the need for workers to place their hands near the point where cable enters the conduit and helps them avoid the mess and slippery surfaces associated with manual lubrication.
Most power puller manufacturers offer pulling rope, lubricants and a selection of accessories. Commonly used accessories include cable and rope stands, a variety of types of grips for attaching wire to rope, swivel clevises that connect the rope and grip to prevent cables from twisting inside the conduit, sheaves to support cable and guide it during the pulling process, force gauges to measure tension exertion, remote foot controls, and cable feeders that can be programmed to variable speeds to match that of the cable puller.
Bardin said Maxis Triggers are dual foot pedals for the person operating the puller and the one feeding cable. Both have total control of the puller’s motor with the ability to stop the pull immediately. Both foot pedals must be engaged for the pullers’ motor to operate. Any time either foot pedal is released, the puller’s motor will stop.
Successful, safe cable pulls begin with understanding equipment capabilities and following manufacturers’ operational instructions and safety procedures. When designing a pull, it is best to keep as much rope as possible confined in conduit.
Good communication between the person feeding the cable and the person operating the puller is critical.
Calculating the pulling tension required is an essential first step in preparing to pull cable through conduit. Consult cable manufacturers’ guidelines to calculate proper pulling tensions.
Greenlee has developed a pull force calculator, the Pull Force 8 (PF8) Estimator, that is a quick way to gauge the necessary force for cable pulling jobs in advance. Information provided by the PF8 can be used to help the cable installer determine the needed capacities for the cable puller and pulling rope. Sheaves that support and guide cable during the pulling process are among the most-used pulling accessories.
The PF8 consists of a simple-to-use, Excel-based calculator that can be downloaded for easy access. The user supplies details about a planned cable pull, including pulling length, cable weight/foot, cable jacket type, conduit size and type, and pulling direction (horizontal, up or down). Using the input information, the PF8 calculates an estimate of the required force to install the cable. PF8 is compatible with Windows 7, Vista, XP, and Mac OSX operating systems.
Multiple hazards exist for personnel engaged in wire pulling, and puller and accessory manufacturers’ operational instructions must be followed carefully.
“Attempting to use an underrated puller—a 6,000-lb. model when the pull needs a 7,000-lb. model—is a common problem,” Bardin said. “If an extension cord is needed [to]power the puller, be sure it is rated to handle the power—10-gauge extensions no longer than 100 feet are recommended. If portable power is used, verify the generator has sufficient amp level for the puller.”
Other problems can result from incorrect set up and operation of the puller, positioning of cable supply in the wrong location and incorrect set up of pulleys and sheaves.
The amount of pulling force actually being used should be monitored throughout the installation. Several pulling calculators are available that help determine how much pulling capacity is being used.
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at email@example.com.