Fault diagnosis with trends: how to compare pressure, flame, load, and valves before a trip

Trends allow us to see what happened seconds before a trip. This is particularly useful for faults that do not easily recur in the presence of a technician.

Which variables we record

Useful variables include gas pressure, air pressure, flame signal, load demand, actual servomotor position, and the status of key valves.

First event

Identify which variable changed first. This is often closest to the root cause.

Time correlation

All trends must share a common time base. A difference of a few seconds can lead to the wrong conclusion.

Recording frequency

Slow sampling may miss an instantaneous trip. For fast faults, an adequate recording frequency is required.

Comparing multiple events

If the same pattern repeats before every trip, the diagnosis becomes much more reliable.

Best practice

Trends must be saved before a reset is performed so that the information needed for analysis is not lost.