Town off the hook as failed gear box likely a manufacturer defect, light department reports

After returning from a trip to Germany to watch the "autopsy" of the failed gear box from the south turbine at the wind farm, Princeton Municipal Light Department General Manager Brian Allen reported that what was found "would suggest it was a manufacturer defect" that caused the equipment to fail last August.

That would be good news for Princeton customers, because the manufacturer, and not the light department, would then have to pay to fix it.

The turbine was shut off in August 2011, after metal shavings were found in the oil of the turbine. The gear box was replaced and the turbine was back in service in July 2012.

 At the Sept. 12 meeting of the board of light commissioners, Allen said engineers found a bearing inside the first stage of the gear box that had separated and dug into other parts of the equipment. "The condition of some of the gears seemed to be in worse shape than this bearing could have caused," said Allen.

The bearing, along with metal shavings, will be sent to a forensic laboratory, he said.

One of the engineers on site looked at the bearing and didn't think it was a torque issue, said Allen. He said it looked more like a heat treatment issue.

"Our conversations were very open," he added. "They wanted us to know they weren't hiding anything. They just want to get to the bottom of this because they don't want to be putting out a product with their name on it that has a problem,'' Allen said.

Jake, the company the manufactures the gearbox, has been in business since 1904, said Allen. Their equipment for manufacturing and mining purposes has not been a problem, he said. But the wind industry equipment has been a problem with other companies as well as Jake, in terms of equipment strong enough to handle the torque of a windmill, he added.

"They were as interested in knowing what happened as we are," said Allen. "I wasn't sure what kind of reception I was going to get, but they let me take photos and were very open."

The gears should all be very shiny and smooth, but Allen said he could see a lot of damage and was concerned about the cracks on the gear teeth as well. "Were the cracks there prior to the break or did the crack cause the break?" was a question being asked, Allen said.

Allen displayed a series of photographs of different parts of the gear box. Some showed parts of broken gear teeth, metal shavings that had found their way into the second stage of the gear box and areas that appeared to be burn marks. Normal wear shouldn't produce shavings, said Allen.

"From my point of view it is clearly a manufacturing problem," said Allen.

Most of the damage was in the first stage of the gearbox, some in the second stage, and none in the third stage. Every third tooth in the first stage (planetary gear) was damaged, said Allen and the question for the lab is could the bearing pieces do this kind of damage, he said.

Jake Manufacturing and Fuhrlaender engineers were all in agreement, questioning whether the bearing was the initial problem or whether it broke off and caused the problems, he said. "You're now talking CSI stuff,'' he said. Jake buys bearings from another company and installs them in their gear box, said Allen.

Resident Jim Whitman wondered if the wind stress was greater on the south turbine than the north turbine.

"I'm 95 percent sure it was a manufacturing problem," said Allen. He expects a report from the lab once all the testing is complete. The Fuhrlaender representative was incredibly technologically experienced, said Allen. An analysis of the lubricants will also be done at the lab, he added.

If it turns out it is a manufacturer's problem the $95,000 PMLD paid up front for the gear box replacement will be returned and Jake would pay for the gearbox, said Allen. Then the company will look at the loss of revenue issue, he said.

"I don't know whether they have ever been forced to go to this detail before or whether they just replaced the equipment," said Allen. "But you could see the crack in the bearing race.''

"That in itself is catastrophic," said commissioner Christopher Conway.

Allen also announced he had just received a letter form Fuhrlaender North America Inc., announcing the company will not be maintaining operations in the United States effective immediately. They only have six units in the United States, said Allen.

In other business, commissioners approved a contract with Bachmann Electronic to monitor the wind turbines on an annual basis at a cost of $16, 350 the first year, then $2,400 per unit thereafter.

"I'd like to commend the general manager for the work he's doing on the gear box problem and the letter to rate payers," said resident David Nichols.