Air New Zealand Gas Turbines (ANZGT) specialises in the overhaul and repair of multi-million dollar LM2500, LM5000 and LM6000 gas turbines from General Electric (GE). The GE turbines are high-precision advanced technology, and extremely complex to service – ANZGT is one of only a handful of companies worldwide that can perform this operation.
The challenge for ANZGT was that the two rotab machines were aging. One had already broken down, meaning if the second rotab was in use, measurements had to be done manually which took three to four times longer.
With its high-end gas turbine overhaul business at serious risk, ANZGT started seeking a new solution for their missioncritical measurement system.
“We needed to grow the business, so we simply couldn’t continue relying on manual processes,” says production leader Brian Manning.
“We need incredible accuracy – the ability to measure down to a hundredth of a thousandth of an inch – and the only place to get it was from a German manufacturer, Mahr.
“Once that supply was decided, we went in search of an expert partner who could build the system around it,” he says.
In searching for a possible supplier, Mr Manning came across National Instruments, who referred him to their Alliance Partner for New Zealand, Nightside Test Design.
“After receiving the call from Brian and completing a site visit, I was confident Nightside was up to the challenge,” says managing director of Nightside Peter Brown.
“We set to work immediately identifying the best Mahr probes and amplifiers to use and selecting the National Instruments data acquisition hardware.”
As work began on the development of a new system, the team at ANZGT got down to their last Mitutoyo sensor on the only functioning rotab, and knew that doing all of the rotor builds manually was simply not an option.
Anticipating that a complete production shut down was imminent, they again turned to Nightside whose engineers were able to quickly devise a temporary ‘converter’ system which enabled the new Mahr sensors to be used with the old rotab equipment and keep the operation going until the new rotab was in production.
“We were very close to a full production shut-down, it was an intense time,” says Mr Manning.
“I was impressed with Nightside. On the one hand they were professionally custom-designing a very sophisticated new system, and on the other hand scrambling to quickly devise a patch solution around sensor compatibility on the old one which enabled us to keep going – that’s incredible service.”
Nightside identified how the rotab measuring system operated, then designed and built a replacement in the space of six months.
The new rotab system comprises a National Instruments cRIO platform with custom-designed software connected to the Mahr Linear Variable Differential Transformer (LVDT) probes and Millimar amplifiers.
Part of the specification was to maintain a close resemblance with the old equipment so as to minimise the training requirement for the team of four who would operate it. The first system went into service in March 2012, with the second following as soon as comparison testing had been completed.
The new rotab measuring system was a vast improvement over the manual measurement methods and ANZGT estimate they’ve achieved an additional 30 percent time savings over the old rotab – the system is expected to pay for itself within two years.
Accuracy has also improved, leading to lower vibration levels and improving the service life of the turbine – which means lower maintenance costs for ANZGT’s customers.
“The return on investment is certainly on-target, but in reality we were more interested in the ability to maintain continuous service. Scheduling these turbines in for overhaul is a precise operation and many clients are losing revenue every day that they are not in use. Air New Zealand Gas Turbines faced a very real possibility of shutting down production when the sensor supply ran out – that would have cost us and our customers millions.”
“I can’t speak highly enough of the job Nightside did for us. They satisfied every request, every specification. They guaranteed they could meet project targets and timelines, and they did,” says Mr Manning.
“The quality of the new system was paramount, it has performed brilliantly – and so did they.”
As a result of the work at ANZGT, Mr Manning referred Nightside to the Air New Zealand Christchurch group for their test cell programme for auxiliary power units, a project that Nightside subsequently won and is due to complete in mid-2012.