Indirect fault detection is based on the effect of faults on certain operational parameters.

Example

• Leakage from a container may affect the pressure in that container, resulting in deviation from the range of probable measurements.
• Malfunction of an engine may result in unacceptable delay in starting it
• Instable unit operation may result in deviations from thresholds defining the envelop of stable operation, or from the state machine ... describing normal operation.

Implementation

Rule controllers

Rule definition

• Use statistical process control (SPC) for detecting faults during normal operation, as illustrated in the following figure ...
• User trend analysis to detect faults during process initialization, as illustrated in the following figure ...

Limitations

When detecting deviations from the operational rules using the indirect fault detection, we still do not know the source for the deviation. Extra manipulation is required to identify the source.

Related topic

Updated on 20 Jul 2016.