When Rosendin Electric workers tried out a new cable-feeding machine that requires half the manpower of traditional cable pulls, it was almost like cheating. Now this San-Jose-Calif.-based electrical contractor, one of the largest in the United States, is pulling cable at the San Francisco International Airport expansion. The $2.4 billion expansion is one of the largest and most complex U.S. construction projects underway; by 2003 the size of the airport will double.
Rosendin is responsible for the electrical contracting of Boarding Area A, one of the airport's two new international concourses. The $10 million (estimated) contract involves rough and finish overhead electrical installation. Rosendin workers are pulling power cable from utility service in the main terminal to transformers in two substations 1300 ft away. The transformers stepped the 12,000V down to 480V then to 120V.
When the job is complete, Rosendin workers will have laid 100 miles of cable for power and lights in Boarding Area A. The company's longest single pull so far stretched for 870 ft; the largest diameter cable was 500 MCM.
Rosendin General Foreman John Bloxsom and his crews have been using a prototype Greenlee Cable Feeder to speed the cable pulling process.
"What everyone installing cable knows is that the better you feed it the easier it is to pull," said Bloxsom. "The old 'grunt' way requires a man, sometimes two, on each reel trying to keep pace with the tugger on the other end. This has never been an efficient or particularly effective use of skilled manpower, but there was no other way."
As many as six people are required to do a typical pull the traditional way: one man operating a cable puller; one man each on four heavy 500 MCM copper conductors coming off Wemco (steel) or wood reels; and another man soaping and guiding the bundle into the conduit. Bloxsom said that with a cable feeder a pull requires just three people; one operating the cable puller, one operating the cable feeder, and one soaping the cable. So, workers don't have to leave other important jobs when it's time to do a pull. \
"With pulls of hundreds of feet, and going pretty much nonstop for hours, this is a physically demanding job that takes its toll after awhile," said Bloxsom. "Pullers can deliver up to 8000 lb of pulling force; enough power to pull thousands of pounds of cable through hundreds of feet of conduit. But if the feed isn't keeping pace with or matching the speed of the Tugger, tension can build."
Cable feeders allow users to match the speed of cable coming off the reels with that of the pull. Here's how it works. The feeder is first positioned between the reels and the conduit. This is easy because the feeder is compact, comes with wheels, and can be wheeled into place by one person. Then, as many as eight 250 MCM cables, or up to five 750 MCM cables, are fed between the feeder's two traction wheels, which grip the cable top and bottom and provide the feeding power. Once operation starts, only two people are needed at the feed end of the pull: one to control the cable feeder and another to soap the "form" as it goes into conduit.
The cable feeder has a variable speed control capability allowing an operator to adjust to any pulling speed; from 4 ft to 36 ft per min. Conceivably, one person could be used to both operate the feeder and soap the cable because start/stop control can be done with an optional remote foot switch.
Another feature Rosendin's people like is the unit's ability to keep the feed "organized." According to Resident Foreman Cary Lea, cable can often become tangled when it's fed manually. This causes frequent stops and the tiring process of untangling the cable.
"But the cable feeder has a 'comb' that keeps the cable separated and prevents them from tangling," said Lea. "The bundle is better organized, so it can go into the conduit easier and faster in one straight exact 'form.' Otherwise, the overall profile can be raised, making it impossible to feed it in."