Guest post by Brad Loucks, Mechanical Engineer at Pioneer Engineering
In a condition monitoring vibration program, determining the appropriate intervals of data collection is just as important as the data that is being analyzed. Properly scheduled data collection intervals of equipment provides data analyst with a better picture of how equipment is performing over a period of time. Having a history of data is important for in an effective condition monitoring vibration program and this is done by establishing correct data collection intervals.
Data collection intervals should be established and executed with purpose, not done randomly. To establish intervals, it is important to know and understand how equipment works. Determining the appropriate time interval between collections is done by identifying how often the equipment runs, how fast it runs, and the application. The calculations are based on the estimated life cycle of the bearings but also the estimated amount of time it takes to go from a defect to complete failure.
Collection intervals should be a routine function. Many times data collection falls behind because the collection person is too busy to collect the data. One of the most common issues that I have come across is that plants will begin to collect data and then the person collecting the data gets pulled to do other work and the data collection gets missed and becomes more random. This is a slippery slope in that it almost always leads to the data no longer being collected. Then when an emergency comes up such as a bad sounding machine, the analysis has not been collecting a history on the equipment but they have also been out of the analysis for so long that they have a difficult time remembering how to analyze. The history and interval is just as important for a proper analysis as it helps to give the analyst a more accurate analysis by allowing them to see the progression timeline.
Bearings often do not fail in a predictable time span. If this were the case, vibration analysis could be overlooked and time-based maintenance could be used. A bearing can go from a known defect to catastrophic failure over the course of a few years or it can happen within minutes. The collection intervals are calculated so that not only can data be collected and the severe defects be identified, but also to identify when a defect has formed and allow for a history to be built in order to watch the progression of the defect. This can aid in determining whether immediate action should be taken or if the defect is at an early enough stage where proper planning and measures can be taken to avoid an immediate shut down and loss of production.
If the equipment is deemed valuable enough or if unplanned downtime is just out of the question, then calculated collection intervals are a necessity of a proper condition monitoring vibration program. Through proper maintenance, a condition monitoring vibration program can save a plant both time and money in reducing or eliminating unplanned downtime, as well as significantly reduce the possibility of injury or death of plant staff due to catastrophic equipment failure.
Download our Calculations of Bearing Defect Frequencies
by Ana Maria Delgado, CRL
Most equipment failures are not age related. The equipment will provide some sign of impending failure if we have the right tools available to understand the change in condition.
A lot of facilities assign monitoring intervals based upon arbitrary schedules such as 30, 90, 180 or 365 days. Often this is due to a lack of understanding of how equipment fails, misunderstanding how conditional tasks such as vibration analysis work, available labor and lack of importance placed upon Condition Monitoring (CM) efforts. These arbitrary collection intervals can actually lead to failures that go undetected and a loss of value from the effort. The equipment will tell you how often monitoring must be completed. Not understanding this can lead to costly results!
How does your facility determine the correct monitoring intervals for CM efforts? Is it based upon man power, gut feel, P-F Interval or what someone told you to do?
by Trent Phillips
Vibration Route Frequency
How often do you collect vibration data on your equipment? Is it monthly, quarterly or even yearly? Most of the time Management will allow data collection frequencies based upon the importance they assign to vibration analysis or available resources at the time. Management may actually ask that vibration data be collected every month or even more frequently if the machine has failed recently. Different companies and managers use different means to determine how often to collect vibration data or any other CM data for that matter.
Assigning arbitrary data collection frequencies (routes) to your equipment may actually do your reliability efforts a disservice. The best method is to determine the failure intervals of the failure modes (bearing defects, etc) in the equipment. Assign data collection intervals short enough to identify these failures. For example, a bearing may develop a failure on day one and run for ninety days before it causes the machine to fail. If the machine is monitored with vibration analysis every ninety days, then your analyst may never identify the bearing failure condition in the machine. The result is that your machine will most likely fail without anyone being aware of the issue. If the same machine is monitored monthly with vibration analysis, then the bearing failure condition would most likely be identified with your vibration monitoring program. This would alert the maintenance department of the issue and allow appropriate repair efforts to be budgeted and scheduled.
by Trent Phillips