Setting Baseline References for Vibration Analysis
Vibration analysis is used to monitor the condition of rotating equipment and predict equipment issues based on data trends. The first step to successful vibration analysis is establishing relevant baseline references.
Experienced analysts typically use one of two methods to establish baseline references. The first method is a general or “one size fits all” approach that is based on the International Organization for Standardization (ISO) guidelines. The second method is individually tailored for specific equipment designs and can deliver customized alarms as needed.
Regardless of which method is used, the first step in any vibration program is to gather as much information about the machine, its function, and the environment as possible. Drawings or machine schematics should also be obtained if possible. A good practice is to talk to everyone who interacts with the machine. This includes both management and maintenance personnel, as they can provide important machine insights. These critical clues often help to determine what is going on with the machine and can highlight potential issues. For example, you may learn that the machine has issues every time it rains outside. This information would guide the analyst to focus on issues surrounding moisture or humidity.
Method 1: Using ISO Guidelines
As mentioned, one method for setting baseline references is to use specifications from organizations such as ISO. They publish vibration specifications for certain types of equipment to be used as a guide. The ISO guidelines consider machine classes and how they qualify as a starting point for setting up baseline reference points. In recent years, this method has become the industry standard for setting baselines for vibration analysis.
In addition to these guidelines, some manufacturers have established baseline data for their equipment. This is the case for many pumps, fans and motors. At the component level, bearings also have well-established baseline data. This existing bearing data is very useful when analyzing equipment such as motors, reducers and pumps, each of which usually contain several bearings.
Method 2: Customization with Statistical Calculations
This method takes into consideration that every motor will run slightly different than the next. Even the same model from the same manufacturer might be slightly different. Using the customized method, alarm limits are set based on statistical analysis of vibration data generated for the specific machine being monitored.
Algorithms are designed to detect negative trends based on the customer baseline. If readings are getting gradually worse, an alarm would be triggered. However, sometimes customers are concerned that a piece of equipment is already going bad. The baseline set by ISO guidelines won’t catch this condition. If the vibration trend on the equipment rapidly deteriorates, it likely already had a problem. But, if the data doesn’t change, we can adjust the alarm level to establish a new alarm criteria. This type of customization will allow for specifics of the equipment to be considered whereas generalized guidelines could not.
Once baseline data is established, data trends can be tracked over time to predict equipment issues before they lead to failure.