Visualising Chi Data

Posted on: 29 /03 /2022

Sensoteq Chi is a vibration sensor designed to get information into your hands quickly, allowing the user to make fast decisions. This is particularly evident when a user needs to analyse a rotary-oscillating machine such as a vibrating screen. 

The energy a screen generates can be classified as either desirable or undesirable.

Desirable energy is the motion the screen generates in the same plane as the side plate.  This motion is used to bounce the material in a certain manner across the top of media (screening surface).  The energy within this plain is significant but occurs at a specific frequency (the screen running speed).

Undesirable energy will occur in all three axes on the machine and are a result of poor maintenance, machines operating beyond expected parameters, and faults that naturally happen over time.  This energy can damage the machine in other ways, such as putting extra strain on the bearings or loading beams, and causing cracks.  Being able to continuously monitor this energy is of critical importance to ensure the continued smooth running of your machinery.

There are several key parameters that are important when analysing a screen:

·         Stroke Length

·         Stroke Angle

·         RPM

·         Displacement (Z Axis)

These parameters are all available as a “Quick Measurement” in the Chi app, but can looked at in more detail when stored to the Analytix Cloud Platform.

Stroke Length, Angle and RPM are good indicators that the desirable energy is consistent across the entire machine, and within the parameters that you expect – this ensures that you are maximising the output from your machine and not wasting material.

Stroke length and angle can be visualised both as an average, and as raw data to give good insights into the performance of the machine.  Averaging the data (left image) gives a clear view of the angle and the type of motion (elliptical, circular, or linear) that is expected, but mainly provides useful values that can be trended over time or compared from one inspection to the next.  The raw data (right image) shows the real motion of the machine and can help diagnose more specific faults.

Displacement (Z axis only) is a fantastic indicator of undesirable energy.  Also called transverse motion, this parameter measures the side-to-side motion of a vibrating screen, which should be kept to an absolute minimum. Any excess energy in this axis is wasted energy that is likely damaging another part of your machine, as the structure and bearings will be “absorbing” this energy.  Energy in this direction can occur at any frequency, and by measuring the frequency it can be possible to ascertain the cause of the problem. With Chi, we can visualise the “Z vs Y” or “Z vs X” motion to understand what pattern exists.  Looking at the velocity spectrum can show us the frequencies that are present in this axis, in the example below, we can see a large peak (9.5mm/s) at the running speed, indicating some mounting looseness in this machine.

Chi allows the user to quickly perform checks when physically present at the machine, but also dive deeper into the data when sitting at their desk.

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