Condition monitoring specialists and vibration analysts often document an unusual machine failure or a "save" for various reasons. One is to prove the value of the program over and above the cost. Another is to use them as teaching tools.
When using a condition monitoring technology to diagnose faults in machines or other plant assets, it is important to create case histories of each diagnosis that triggered a repair or work order, whether it was correct or not. If one uses vibration analysis for example, to detect rolling element bearing wear in a machine, and if this data is trended until a decision is made to replace the bearings, a short report should be written that explains the data and the trends and the decision to overhaul. When the bearings are removed from the machine, they should be cut open and inspected to see if they were in fact damaged. Digital photographs should be taken and included in the case history. It's important to test the machine with the new bearings, to verify that they were installed properly and that no problems have been introduced by the maintenance procedures. If everything appears to be in order, the new data can be added to the database and new vibration baselines created.
Of course, the story may not end here. You should always try to determine why the bearing failed. Was it damaged during shipment from the factory, was it installed incorrectly, were the problems with lubrication, was it the wrong bearing for this particular application? If the machine has a history of bearing failures, there must be something that is shortening their useful life and you should be investigating the root cause.
The case history should show both the early data to document when the fault was first detected, trending data showing how the fault was observed to deteriorate, and data from the machine after repair. If possible, financial implications of this decision are important to include, but be sure to put them in terms that plant managers use to make their decisions, such as Overall Operating Efficiency or production output improvement. Many companies will not consider preventing a catastrophic failure as a cost savings.
Good case histories are important because they are a way of documenting knowledge that can be used to train new employees in the future, used as reference when new situations arise and because they help to justify the use of the technology one is using. Don't just write the report and file it away. It should become part of the machine history in your CMMS. It should also be related to the bearing manufacturer and application. Even a binder of case histories in the break room will help your cause and will give other employees the chance to learn about and appreciate your work. Many trade magazines and websites are interested in publishing these case histories as a way to educate others in the field.
Tip Provided by: Bill Slonaker, Marketing Manager
Mobius Institute
