Allied Industrial Engineering turbine specialist Steve Sands, who previously worked for the General Electric Company in the United Kingdom, says the project for Norske Skog is the most significant he has worked on.

“The manufacture of a brand new turbine rotor has never been done in New Zealand before,” he said.

After generating electricity for more than 20 years, the TA3 steam turbine at the Norske Skog energy centre had begun to show its age.

Mr Sands said chemical processes and age had affected steel in the machinery.

Norske Skog Tasman mechanical engineer Don Pedersen said turbine blades were falling off and cracking had appeared.

“We were facing, at minimum, a two-month shutdown of the turbine if we had to replace all the blades,” he said.

A catastrophic failure of the ageing turbine would lead to a far-worse scenario.

In January 2014, Norske Skog gave AIE the job of fixing the problem.

Mr Sands said it took three months of planning to produce timelines that both Norske Skog and AIE agreed on for the manufacture of the rotor at the AIE workshop.

AIE then started detailed studies of the existing rotor, reverse engineering it so they could manufacture a new one.

The original rotor manufacturer sent a couple of old, spare turbine blades for AIE to study, and a new rotor forging. The unprocessed central axial component was ordered from Germany and the rotor blades from The Netherlands.

Meanwhile, AIE developed a special software program to balance the rotor blades once all the components had arrived and were ready.

Materials testing, machining, balancing and fitting the new components into a new rotor assembly was a highly technical process that was checked and double-checked at every step.

Only the original coupling, the connection that transfers the rotational power, was used from the old turbine rotor.

Installing the new turbine rotor took 13 days. Mr Pedersen said it was discovered the old rotor was badly deteriorated during the replacement shut down.

“We discovered one of the blades was about to fly off. It was a bit of a time bomb.”

On successfully starting up the turbine with the new rotor, everybody breathed a sigh of relief.

The new rotor had been operational since October 10 and was performing flawlessly.

“AIE had recommended opening the rotor up three months after the installation, but it appears there’s no need,” Mr Pedersen said.

Mr Sands said while he could not reveal the dollar figures involved, the Kawerau engineering feat had saved Norske Skog half the cost of buying a new turbine rotor from overseas.

“With the new rotor, the output from TA3 has gone from 8MW to 9.5MW, so the work will pay for itself over time,” he said.

 

Source: Whakatane Beacon