Chemical Plant Wireless Sensor System

Root Cause Failure Analysis (RCFA) success at a Chemical Plant using high resolution wireless vibration sensors to inspect equipment with high overall vibration.

A commonly used wireless vibration sensor system was installed on a fan in a chemical plant. The system, part of a wireless instrumentation network, was only measuring overall values and some narrow bands. The system alerted the customer of an existing issue: overall vibration levels were high on a critical machine. As the only available information was the overall value, the customer had no way of knowing exactly how serious the problem was, or the cause of the problem.

SOLUTION

We installed the Wi-care™ vibration system on the machine. Installation and commissioning was completed in less than 15 minutes, and the first measurement results were received. Every 15 minutes, a spectrum was measured with Fmax of 4kHz and 6400 lines of resolution.

RESULTS

This was the trend plot after 4 hours:

trend-plot1

It is obvious that the vibration level is fluctuating a lot. We employed the following methodology to find out why.

From the above plot, we select a measurement point when the machine was vibrating at 10mm/s (12PM), and analyse the spectrum.

spectrum1

The next measurement point we select is at 1:12PM, when the machine's overall vibration is over 20mm/s.

spectrum2

When we compare both spectra, there is one difference - the speed. When the production increases, the speed of the fan increases from 1590RPM to 1665RPM and the vibration levels double.

CONCLUSION

The imbalance value is high in both cases, so cleaning and field balancing are recommended. However, the fact that a small change in speed, has a major influence on the imbalance value, is an indication that the fan is also running close to it's resonance frequency (critical speed).

Thanks to these results, the customer knows the root cause of the problem and can now plan action to solve it.

To obtain this information, Wi-care™ sensors were installed on the machine, and also powered a gateway in the neighbourhood. This installation took less than 15 minutes. Half a day later, this conclusion was produced. This proves once again that the Wi-care™ remote condition monitoring system is a Plug & Play system that provides high resolution data and high accuracy in determination of fault.

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