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July 10, 2020
Imperial Power’s Time Saving Turnaround Cuts Outage Time by 12 Days
High Capacity Crawler Crane Transforms Switchyard Job
Asubstation outage can be incredibly costly for an electric utility. To avoid an expensive shutdown at a high-voltage switchyard in southern Indiana, Imperial Power Services Inc., Newkirk Electric Associates, and AEP used a new way of moving several 765kV transformers that shortened turnaround time and potentially saved he utility millions of dollars.
At the Sullivan Substation, AEP was expanding its high-voltage yard and had planned for 28 days of work, including 18 days of outage. To make the necessary improvements, several large electrical transformers needed to be removed.
“Whenever they move these big transformers in or out of the switchyards, they typically use a jack-and-slide system,” said Rick Bohne Sr., vice president of Imperial Power Services. This moves the loads laterally into position using a slide method. “It is cheaper to jack and slide, but it is also time consuming,” he added.
Long-time Imperial Power customer Newkirk Electric was the general contractor on the project, performing both the underground and above-ground construction. During the bidding phase, Newkirk approached Imperial to assist with heavy-lift planning and on-site crane and rigging support.
To write the quote, Bohne was told that seven transformers would need to be moved, and each trans-former weighed between 420,000 and 480,000 lbs. The transformers were slated to be removed during two outage periods—four during the first outage and three during the second—and there was a two-week window to complete the job.
“Newkirk said, ‘We’d like a price for jacking and sliding them out and a price for any other way you can think of,’” Bohne said. “I suggested coming in with a big crawler crane and grab-bing the transformers and carrying them out—and that I could do four of them in two days.”
With time being the most crucial factor on the project, AEP and Newkirk Electric welcomed the new plan of action. The Imperial Power crew then put its proposal in motion.
Transformers Make a Move
Bohne worked for about a year to produce a rigging plan and crane configuration for removing the transformers from the switchyard.
“The major challenges on the project were the tight outage schedule and restricted working limits around energized equipment,” said Brandon Herman, project manager/estimator for Newkirk Electric. “We spent a lot of pre-planning time laying out work sequence plans, setting clearance limits for working close to energized equipment, and identifying what we could pre-build to reduce the labor hours required during the outages.”
Imperial brought four cranes to the substation: a 75-ton Tadano GR-750XL rough-terrain crane, a 330-ton Liebherr LTM1300-6.1 all-terrain crane, a 350-ton Grove GMK6300L all-terrain crane, and an 825-ton Liebherr 1750 lattice-boom crawler crane.
The RT and ATs helped with demolition work and tower construction. Herman said those cranes enabled Newkirk to assemble all of the project’s 175-ft. A-frame towers on the ground. “That saved eight total days during the two outages,” he added.
To lift the heavy transformers, the Liebherr 1750 lattice-boom crawler crane, which was rented from Buckner Companies, was rigged with a 138-ft. S-Boom and 20 parts of load line.
“This particular crane was used because it had the capacity to reach out and grab the transformer,” Bohne said.
“Because we had to walk about 650 ft. with the transformer, you want the crane balanced,” Bohne added. “With this crane, I could set the boom at a certain angle, and it was perfectly balanced, meaning as much weight was hanging in the front as was on the back of the track. It provided a very good ground dispersion as we were walking it.”
Before making the lifts, the Imperial Power team ensured the Liebherr 1750 maintained its stability by building a road to travel on as it rolled onto the site. Then came removal of the heavy 765kV transformer.
The load rigging included a 250-ton spreader beam hung from the crane’s load block, two 170-ton spreader beams suspended perpendicularly beneath it, and four 25-ft., 125,000-lb. Twin-Path slings connecting the 170-ton spreaders to lugs on the bottom of the transformer.
“The challenge was picking and carrying that much weight,” Bohne said. “Each transformer was lifted from the bottom instead of the top, so you had to make sure that it was balanced and didn’t roll.”
The difference in cost between using the crane and a jack-and-slide system was about $100,000, Bohne said, but when you do the work in two days instead of two weeks and cut 12 days off the outage, “$100,000 is the best money you’ll spend in your life.”
Herman said that on future projects Newkirk Electric will evaluate the use of a large crawler crane versus the jack-and-slide method. “The large crawler crane is the most efficient and cost-effective method when you have four or more transformers that need to be moved and you are not restricted with an outage schedule,” he said.
“Each project is different, but because of the great working relationship we have with Imperial Power Services, we will consult them on all future projects at the bidding phase to identify our best option,” he said.