After an airplane ball burns up, line workers investigate the cause from an aluminum cart.
Two years ago, Tacoma Power (Tacoma, Washington) celebrated the completion of one of the longest power line spans in the world. Measuring 6,240 feet, the line was considered an engineering marvel when it was first built in 1926. Over time, however, the four original 325-foot-high towers reached the end of their life span.
To ensure safety and power reliability, Tacoma Power replaced the towers with two 450-foot high towers and installed a new mile-long power line as part of the $17 million project. To prevent airplanes from crashing into the span, which is located a mile from a small airport, the project also included the installation of fiberglass marker balls.
The balls, which measured about 3 feet in diameter, come in two halves that are bolted together by eight bolts. Another eight bolts attach them to the line. The interior of the balls is covered in a conductive coating, which is bonded together and to the line.
In April 2009, one of the marker balls burst into flames and burnt completely. After initial investigation from a helicopter and subsequent extensive planning, line workers for Tacoma Power tried to uncover the root of the problem and fix it. While the cause of the fire is still under investigation, line workers spent about two weeks inspecting for damage to the conductor where the incinerated ball was located and checking to see if the rest of the balls were installed properly.
As part of the damage-assessment process, Tacoma Power's field crews disassembled the remaining marker balls and took photos to document their condition. Because of the nature of the job, Tacoma Power spent a lot of this time on safety and job planning, as well as properly and safely moving equipment to where it was needed.
Once the crews determined there was a problem with one of the marker balls, they had to find a way to access the line. While the balls weren't heavy, it was a challenge to simply go out on the line to reach them.
Just getting to the center of the span and back is a challenge for the line workers. The span is a mile long, and it has a steep angle going from the tower as it dips down across the water.
To try to avoid working in the dark, when it was difficult for the crew members to find their way, they tried to work on only a small portion of the line at a time.
To access the line, which crosses over the Tacoma Narrows waterway, the line workers went to the back span where they could reach the conductor using their cranes and hang an aluminum cart needed to perform their task. To pull the cart and the employees up the back span, the line workers relied on an overhead wire puller from Sherman & Reilly Inc. (Chattanooga, Tennessee).
It took anywhere from an hour to two hours of careful rigging to transition their cart around the suspension insulators from one span to the other. To be let out halfway across the Puget Sound, the line workers relied on gravity while attached to the puller. A crew of three line workers rode the cart to each dampener and marker ball to inspect, remove and replace each one.
Toward the bottom of the span, gravity was not enough to propel the line workers, so they had to pull themselves by hand to reach the last two balls.
The aluminum cart has a history of its own. For many years, the line workers used it to maintain the old conductors, which were made of steel. Field crews had to periodically go out in the cart and reapply a black tar-like, greasy protective coating to the wire to keep it from rusting and prevent bucking on such a long span.
The conductor on the original tower was made of plow steel, because at the time it was the only material able to withstand the tension of its own weight at such a distance. When it was installed in 1926, the conductor was laid across the bottom of the Puget Sound, lifted up to the towers and sagged. A protective coating of zofar inhibited corrosion and had to be reapplied periodically.
The new conductors are flat-strand aluminum with a heavy steel core, so the line workers no longer have to worry about rusting and corrosion, but the cart that was used for many years came in handy on the recent Tacoma Narrows Crossing marker ball project.
Working on the Line
Rather than working on the energized line, the line workers instead worked on one circuit at a time and made sure it was dead and grounded before going out on it. They stayed in the clear of the other side that was hot and barricaded access to the energized side of the tower.
To access the marker balls on the de-energized line, the line workers had to take off all the dampeners along the way. There were up to 12 dampeners each time they went out on the job, so they would do half of the span at a time. When the line workers reached a dampener or ball, they would stop, carefully mark its place, number, remove and secure it to the cart or temporarily secure it back to the line until the return trip so it could be permanently reinstalled.
Communicating with the Crew Members
Because the crew was working at such a high distance off the ground, they maintained full radio contact at all times with the line worker on the overhead wire puller. The line workers would tell their coworker to pull them up and tell him to stop once they got close to the dampeners where their work would take place. This worked surprisingly well. In fact, it seemed almost like the lineman on the overhead wire puller was in the cart with the rest of the crew.
Communication was also key when it came to the rescue plan. As part of Tacoma Power's stringent safety practices, the crews had a plan for rescuing their coworkers before they even got on the towers, which are the tallest ones in Tacoma Power's service territory.
The line workers also had a phone number of the Tacoma Police boat in case they had to let a person down in mid-span into the water below. If someone was hurt or needed to be rescued from the tower, they were equipped to handle that as well. They carried a rescue rope and apparatus in case something happened to the cart.
The line crews had to get special equipment, extra long ropes and special devices for descending from the tower in case of an emergency. Once they were on the tower, they were 100% belted in. They were never moving around a place of danger without being safely tied in.
About 16 to 20 line workers worked on the project at one time, but overall, a total of approximately 40 line workers worked on the project collectively.
Everyone who helped with the project had the unique experience of working in extreme conditions — an opportunity that rarely comes around.
Through this project, the line workers learned how multiple crews and personnel can come together and finish a job without being used to working with each other on a daily basis. They also discovered how to work safely at extreme heights and efficiently maintain one of the largest electrical crossings over water in the country.
Kevin Kelley (firstname.lastname@example.org) is a line foreman for Tacoma Power, which serves 168,000 customers in Tacoma, Washington. He has been with the company for about 16 years and a lineman for the last 20 years.
The Electric Utility Operations section is designed to help utility field personnel increase productivity and safety on the job. The section, which goes out to 10,000 Transmission & Distribution World readers each month, carries a monthly theme and includes features and departments such as Life Line and Safety Talk.
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