Intelligent vibration monitor

August 2005 Valves, Actuators & Pump Control

IFM Electronic has created an award-winning vibration monitor for analysis and display of rolling element bearings and unbalanced conditions. The Efector Octavis is designed for permanent mounting on a pump, spindle, compressor, or a fan, to monitor failure conditions of bearings or shafts. It is now possible to cost-effectively monitor hundreds of critical machines in a plant and develop a predictive maintenance program without a large upfront investment.

Decentralised machine diagnosis is possible when the Octavis detects acoustic emissions, calculates the frequency spectrum and evaluates the condition of the rolling element bearing. The bearing condition can then be directly read onsite and is signalled by binary switching outputs. The switching signal can be transmitted via unscreened cable, and connection to bus systems is also possible.

Once the device is mounted and parameterised, the conditions of the bearings and shaft are indicated through a 'traffic light' bar graph display. The monitor incorporates a 16-bit A/D converter that transforms the analog signal from the MEMS sensor, a reliable sensor element that monitors the acceleration value via a change in capacitance signal, to a digital signal that can be used for processing.

The digital signal processor (DSP) inside Octavis can process 32 000 calculations per second. The processor is more powerful than a Pentium chip in a PC. The DSP performs mathematical calculations to convert the time domain vibration signal into a frequency domain signal - known as a Fast Fourier Transformation (FFT).

In order to determine which critical frequencies need to be monitored in the vibration spectrum, the Octavis monitor requires inputs for application parameters. These inputs allow Octavis to monitor only critical frequencies and ignore all external noise. A pushbutton is used to 'teach' the monitor the normal operating conditions. An early warning alarm will trigger if there is a large change from the baseline. One Efector Octavis monitor can detect up to five different rolling elements on a machine.

The monitor has two connectors for power and software connection. A standard micro DC connector is used to connect the monitor to a power source or output device. A PC or laptop is connected to the monitor via its RS232 connector and set up cable.

Green LEDs indicate good running conditions, while yellow LEDs give the first indication of rolling element bearing damage, allowing the technician to take preventative action. Progressive damage of rolling element bearings is signalled via the second switching output and is indicated via the unit's red LEDs. The technician should react immediately.

Housed in a compact 40 x 40 mm package, Octavis is able to gather, process and interpret data without human interaction. Its maker says that use of Octavis can reduce maintenance costs by 25-35%, breakdowns by 70-75% and increase production by 20-25%.

For more information contact Hanno du Toit, Shorrock Automation, 012 345 4449, [email protected], www.shorrock.co.za

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Intelligent vibration monitor

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