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Why can’t I just use my Straight Edge?


Submitted by Jonathan Dissinger at VibrAlign

The question of why use laser alignment tools, comes up on a more regular basis than one would think. Many still ask why they should make the investment in laser or dial indicator precision shaft alignment tools. So, let us try to demonstrate what happens when you only use a straightedge. Observe the coupling in fig. #1.

Look closely… is it aligned (vertically) or not? The problem is that it is impossible with the human eye to tell the difference between a coupling with angular misalignment and one that is perfectly aligned. After all, we are aligning to tolerances that are smaller than a human hair. The problem with the straightedge is this… it simply isn’t long enough to accurately show angular misalignment; but let me explain why, before you run to the store to buy a longer one. If you were to remove the coupling, cut open both the motor and the pump and expose both shafts completely then you could “possibly” align to tolerance with a straightedge. In that made-up scenario, you would then be able to visibly see the drop or rise of the tail-ends of the shafts. This rise/drop is what creates the angular misalignment at the coupling.

This misalignment simply isn’t measurable by the human eye at the coupling with a straightedge. Remember, acceptable tolerances for these alignments are thinner than a human hair. The straightedge still has its place however, use your straightedge to get you close in your rough alignment. This will save you time when it comes time to put the lasers on for the “precision shaft alignment”. 


So far this year, the economic predictions for Canada seems to be not so encouraging, if we listen to the analysts. In such cases companies talk about cut backs. Unfortunately training is an area, where, in our experience, people tend to cut back. The question then becomes; can you afford that.?

Shaft alignment and vibration, while just one small part of machinery maintenance, is nevertheless critical to keeping machinery operating. As an example, if you look at the shaft alignment, well trained teams can save you time in doing the alignments, save you money in considerations of things like thermal growth, and of course downtime.  Our Canadian industries cannot afford things like breakdowns. Do you remember the expression, « knowledge is power »? In the shaft alignment world, it is our experience that training, is as shown in Fig.#1.

If you were to evaluate your team, which category would you place most people?

To add to the fact that only 19% are trained by experts in the field, if you combine  that to the figures of fig. #2, which is also statistical data, of the average person, you may find yourself in a situation, where you are losing money because of this lack of knowledge. Increasing reliability, and availability of your equipment, is a key factor in increasing your bottom line profits. 

We still have not spoken of your change in personnel, or how often they do a certain task. If you have a group of people, sharing tasks such as alignment, each person may only get to this task once or twice per year, therefore increasing the need for ongoing training. In most cases, people do not know what they do not know. Training will save you money. Look out for the most important economy, your economy, and make sure you have a team of people that will have the power to save you money.


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