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Condition Monitoring Knowledge

YOUR CONDITION MONITORING KNOWLEDGE

Maintenance dollars are saved by “catching” machine faults prior to critical failure, thereby, reducing the cost of critical failure equipment replacement and the man hours needed to complete this task. Component replacement, instead of complete equipment failure replacement, will allow for better management of maintenance budgets, inventory, and personnel.

To do all this, many technologies are available to you. Over the years, one preferred way has been, in depth vibration analysis. Of course that is one very good solution, but some of you may not have the experts at hand to do this, yet your equipment is just as critical. So… keeping this in mind… there are other options.   

Thermography and Ultrasounds, are some known ones. Machinery Diagnostic is now an available technique, that could help you, in keeping track of the condition of your equipment. 

The most important point is to have a chosen method that will help you prevent any type of catastrophic failure.

Machine Diagnositics is a newer method, sometimes raising some skepticism. One could consider Machine Diagnostic as visiting your General Practitioner. The family doctor may not be a specialist in any specific field, however he has enough knowledge to diagnose basic and common symptoms to treat the most common illnesses. With a Machine Diagnostic Tool, think of yourself as the General Practitioner of your industry and keep your equipment healthy!

MEASURING ACTUAL DISPLACEMENT WHEN CORRECTING MISALIGNMENT

In the principles of shaft alignment, it has been over the years, been a common understanding that in order to measure misalignment, we need to take readings in set positions to re-create a circle, a perfect circle. It is un-derstood that the greater the measurement span, up to a maximum of 180 degrees, one will be able to re-create a perfect circle, and therefore get the most accurate readings of the misalignment between two rotating shafts.

The question now goes a little further when discussing the movement required to actually position these shafts in perfect alignment. It has been, over history, a common practice, and understood that to see the actual movement the sensors, be it dials or lasers, needed to be, in either the 12 o’clock or 3 o’clock position. However, with the evolution of systems, it is now possible to move equipment, and track movement without being at those set positions. In some cases, this may be useful.

However, it is very important that, the users understand the repercussions or actual resul-ts of such a maneuver.  The principal of the measurement of displacement, during the correction phase of alignment, is actually quite simple. In misalignment, there are two possible movements; vertical and horizontal. It is easy to understand, and visualize that if you want to track vertical movement, the measuring sensors must be placed at vertical positions, and if you are tracking horizontal movement the sensors should be placed in the horizontal positions.

What happens to the movement if you are not in either of these positions?

If you go back to the math basics, looking at the (fig.1) triangle, movement in the BC trajectory is not 1: 1 equal to the movement in either the AC or AB trajectory.

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What does this mean from a practical point of view, in your shaft alignment practices? If for some reason you are positioning the sensors on the circle, at positions other than the horizontal or vertical positions, you need to know and be aware that what ever movement that you will read from your sensors, this will not be a true vertical or horizontal movement, it will be, in the best case scenario, an extrapolation of results, or an approximation of your actual desired movement, therefore resulting in multiple correc-tions before obtaining the perfect alignment. It is crucial that you are aware of this, and at all times re-measure, after such corrections, because you could be leaving the equipment, to what you thought was a good position, and therefore showing good alignment, when in fact your alignment is still not correct and needs further correc-tions, before being within your chosen tolerances.

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