Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/934530
48 | January - February 2018 | www . machinerylubrication.com ments and address other potential issues. However, it isn't the most practical method for equipment in operation, as it requires a shutdown as well as dedicated hours for main- tenance personnel to perform the task. With an increased focus on uptime, you may wish to select a different option when shorter inter- vals are required. Vibration Analysis Vibration analysis can also detect misalignment by analyzing the changes in vibration response, critical speeds and machinery stability when compared to an established baseline. Vibration readings usually are in the 1X range for axial vibration or 2X for radial vibration. An abnormal result doesn't always mean there is an alignment problem. Different samples must be taken from both the drive and driven ends to eliminate other possibil- ities and to determine if misalignment is the issue. Depending on the extent of the misalignment, vibration analysis may not detect it until a larger problem with the bearings occurs. erefore, a proper alignment must always be performed first. Screening tools should only be used for detec- tion purposes. Thermography ermography is another method that can provide early detection of alignment issues. Due to the increased friction that exists with misalignment, a rise in temperature will follow. By taking a heat map of the bearing areas, a technician can identify any abnormal hot spots. When machines are inspected, an increase in temperature is not always alarming. is puts a little more responsibility on the user to compare similar machines and be consistent with spot checks. Oil Analysis Oil analysis may also be useful in detecting misa lignment by providing the overall condition of the machine, oil and contaminants. It can identify active machine wear earlier than vibration analysis if performed correctly, i.e., sampling from the right location, flushing sample lines, using new sampling hardware, etc. However, without knowing the metallurg y of the machine's bearings, it can be diffi- cult to establish a direct correlation to misalignment. Testing for elemental anal- ysis can reveal slight increases in common bearing materials such as iron, aluminum, copper, lead and chromium. This data may serve as the first indication that a problem exists within the machine. Coupling oil analysis with vibra- tion analysis can be an effective combination for detecting issues early and pinpointing their exact causes. e microscopic appearance of particles related to misalignment will show shapes, sizes, textures and colors commonly associated with two-body abrasion, scuffing and surface fatigue. FINAL THOUGHTS When setting up machines and trying to determine the root causes of failure, a proper alignment is often overlooked. Even if your team has the appropriate tools and training, you must have detail-oriented people who will stick with the job until it is done right. I have been on alignment jobs that only took 10 minutes to achieve an accurate alignment. Others have taken the better part of a day or two, depending on whether the motor had to be removed for machining. Employing the right personnel can make all the difference in an acceptable alignment or a great alignment – and there is a difference. It comes down to how much of a variance you will allow. On small, low-cost or redundant machinery, being within a few thousandths of an inch may be all that's necessary. On larger machines that can shut down your plant, your goal might be as close to zero as possible. Focus on proactive alignment and doing it correctly the first time, no matter what it takes. e best maintenance programs also docu- ment their results and have back-up measures to predict when something goes awry. By combining different condition monitoring tools, proper training and the right personnel, you should see a decrease in overall failures due to misalignment. ML About the Author Garrett Bapp is a technical consultant with Noria Corporation, focusing on machinery lubrication and maintenance in support of Noria's Lubrication Program Development (LPD). He is a certified lubrication specialist through the Society of Tribologists and Lubrication Engineers (STLE) and holds Level II Machine Lubrication Technician (MLT) and Level II Machine Lubricant Analyst (MLA) certifications through the International Council for Machinery Lubrication (ICML). Contact Garrett at gbapp@noria.com to learn how Noria can help you implement proactive maintenance practices at your plant. BACK PAGE BASICS