IOtech products used in this application:

• ZonicBook Vibration Analysis & Monitoring System • eZ-TOMAS Software

Calpine TMG uses IOtech’s ZonicBooks to capture generator and exciter vibration signals on a gas-turbine-powered machine. The wave forms are typical displays of historical data that engineers need to monitor trends over time. Any subtle changes in the data as seen through the eyes of an expert can be enough information to alert the maintenance engineers of possible failures.

Potential Solution
The data acquisition equipment that Calpine used initially is relatively expensive and has some serious operational shortcomings. The system hardware is large, not easily transportable, does not have remote monitoring capability, shows only the RMS amplitude of the signals, and is unable to show an adequate level of waveform detail to help the engineers detect an impending failure. It does not provide signature analyses or FFTs.

IOtech’s Solution
Because of these limitations, Calpine is now supplementing the old equipment with two 8-channel, ZonicBooks and its companion eZ-TOMAS software. Says Greg McAuley, Outage Services Manager, “We primarily bought the ZonicBooks to measure shaft vibrations before and after an outage. Our secondary use is to remotely measure vibration levels and signatures. We can tie into the plant’s DCS via our Calpine server and see what the direct amplitudes are. But without the ZonicBook, we can’t remotely monitor phase angle, one, two, or three-times amplitudes, and more discrete parts of the vibration signal.” McAuly emphasizes that it’s easy to say there’s a problem when the vibration is increasing, but being able to see what part of the vibration signal or amplitude component is changing is the most important aspect for diagnostics. The engineers monitor the signals over a period of time, so they can see what’s developing and how rapidly.

The ZonicBook’s output connects to a laptop computer at the turbine site, which is used as a server on the Calpine network. The engineers can remotely access the server’s output from another location via the network neighborhood to observe the systems vibration activity. The ZonicBook itself, like the original data acquisition system, connects to sensors at the turbine generator site. The engineers connect them to the existing monitor and control panels, access and record the data, and then examine the acquired data.

Alternatively, they return to the office with the ZonicBook and computer, observe and analyze the data, and then decide what must be done. For example, the engineers use the information to calculate the weight and location for applying balance shot. Then they return to the site to install it or make other changes necessary to solve the problem. After installing the balance shot, or otherwise repairing the machine, they restart the machine and record another set of data. If the data are good, they solved the problem.

When a balance problem has been pinpointed in a combustion or steam turbine, the one-time amplitude and phase angles have to be observed and analyzed. The eZ-TOMAS software isn’t used to calculate a shot directly, but it can break down the direct reading into various components, and then that information is used to calculate or plot the location and size of the needed balance weight.

For the present time, all the IOtech equipment is on-site. The engineers are familiar enough with the ZonicBook to set it up and collect the discrete vibration component data needed to be analyzed, but they would like to program the system so the ZonicBook could be remotely located or controlled. “There is sure to be a learning curve because it involves networking and a little higher level IT information,” says McAuley, “but with the very complete instructions that came with the manual, the engineers should be able to figure it out quite easily. They are in the process of doing that right now.”

Conclusion
The IOtech equipment is performing well at each site for Calpine. The major advantage McAuley claims is the ZonicBook’s portability. In addition to the displacement transducers and proximity sensors, Calpine runs a few Aero-Derivative engines that use accelerometers, velocity pickups, or seismic probes, all of which can be analyzed by the ZonicBook, but most of the new generators are outfitted with proximity probes and built-in displacement transducers.

Download the complete Application Note in PDF format.