On demand from our readers, this week we turn our focus on the subject of Alignment and balancing. An often overlooked aspect in reliability, misalignment and unbalance are the major cause of failures in rotating equipment. From your private cars to your small sized or heavy duty machines that have rotary parts embedded in them, alignment and balancing are a major concern. One should never take the issue of unconventional vibrations or excessive heat emission from rotary parts of a machine for granted as they may be signs that there is either a misalignment, an unbalance or both.
Alignment and balancing are at the heart of quality maintenance in any rotating equipment or industrial facility. Ensuring that proactive measure is taken to properly monitor the conditions of alignment and balance of machines would not only reduce maintenance and repair cost but ensure the longevity of asset life and also minimize power consumption.
Let’s do a little study of what these two terms mean. They do not mean exactly the same thing but are simply two sides of a coin. They coexist and the check of one should always extend to a check on the other.
Alignment in very simple terms has to do with proper positioning or state of adjustment of parts in relation to each other. It means that one part improperly positioned would possibly lead to a misalignment. And guess what? Any misalignment will increase the stress on the shafts of the machine resulting in an early or say premature wear of the component(s) of an asset. Again, it is important to note, that misalignment could be angular, parallel or even a combination of both. There are common causes of misalignments and it would not be out of place to attempt to describe a few.
- Improper Installation of part(s) – This is the most common cause of misalignment. Imagine the tires of your car not properly aligned to its wheels. The tires, no matter how new they are begin to gradually wear or the wheels begin to struggle to properly accommodate the tires and boom! the tires burst or in some cases pull out leading to a breakdown in the vehicle.
- Uneven thermal growth between components – Machines would always experience thermal expansion and reduction. They would always experience thermal growth, but in the event that thermal growth becomes uneven, misalignment could gradually set in.
- Foundation structural integrity issues – when a machine cannot ordinarily hold together its components under a load, including its own weight it could be a structural integrity issue. When this machine begins to break down too soon due to misalignment, there could be a foundation issue possibly from a miscalculation on the part of the manufacturers. This could also be due to human error in the construction of components.
Methods for alignment could be by the usage of the straight edge and feeler gauge, rim and face method, reverse rim dial or better still the laser alignment method which is today the fastest and most accurate.
Unbalance exists when the center axis of a component or part is not its running center axis. There is usually an uneven distribution of the weight of the rotating parts around the center axis. This would cause a strain to the machine and vibrations when rotated at certain speeds. There are also few causes of unbalance.
- Inherent – These causes are mostly inbuilt. They include porosity, eccentricity, assembly design, machine errors and casting flaws.
- Induced – By induced we mean the causes are a function of interference with the initial design which includes loose parts, improper key sizing, deposit buildups, thermal distortion, erosion or even improper maintenance.
Methods for balancing could either be the old fashioned static method or the dynamic approach.
Having explained all these, it is pertinent to provide a way out. How can misalignment and unbalance be avoided or at best brought to its barest minimum? Condition Monitoring is our answer. Condition monitoring puts you in charge of your equipment or facility. Nothing takes you unawares as it helps one to actively prevent breakdowns and optimize maintenance resources.
Condition Monitoring would assess the health of your machine by periodic monitoring and analysis of data obtained during operation trending the results against levels of acceptability alerting operations and maintenance personnel to when there is any tendency for a misalignment or unbalance.
Modern condition monitoring encompasses many technologies, such as: vibration analysis, thermography, Tribology, electron motor testing & laser shaft alignment. Two or more of this technologies could also be combined to achieve better results.