About Data Censoring in a Probability Distribution Analysis

Censoring a datapoint means that the datapoint is excluded as a failure but included in the operating time of the Asset. If you select the Censored check box, the data in the selected row is excluded. When you create a Probability Distribution Analysis using a query or dataset as the data source, the GE Digital APM system automatically censors time values from the beginning of the Analysis Period to the first event and the time value from the last event to the end of the analysis. After the calculations for the analysis have been performed, each time that the query or dataset is refreshed, the failure data will be automatically censored.

Regardless of the data source you use, you can censor any failure data. Consider the following:

• For Maximum Likelihood Estimators (MLE), the maximum number of censored datapoints is one (1) less than the total number of datapoints.
• For Least Squares estimation, the maximum number of censored datapoints is two (2) less than the total number of datapoints.

Assume that you want to determine the reasons for a pump failure.

A pump might have failed due to multiple reasons, such as rusted part, motor overheating, insufficient power supply, or power outage. Each of these reasons will have its own specific failure rate and probability density function. To determine the failure rate of "motor overheating," you must censor all other failure modes from the analysis.

Further, motor overheating might be caused due to multiple reasons, such as improper operation, improper application, and improper maintenance. The censoring feature allows you to separate the failure modes, and determine which is the dominant failure mode. Based on this information, you can decide what is needed to improve the motor performance.