Trip analysis — why the unit stopped
The fault list tells you what tripped. This tells you what was happening before it did. For every shutdown the panel recorded, Overtrace reads the half hour leading up to it, ranks what moved, and says whether the log points at one part or at the conditions the machine was running in.
Where the trips come from
From the panel's own latched shutdown-cause history — on an Emit log that is the Annunciator Prev Shutdown column. Every assertion is a separate trip, so a cause that fired three times gives three entries with three timestamps rather than one summary row. Entries that record a person rather than a fault — Manual Stop, Power Cycle — are kept in the history and labelled as commanded stops; they are never given a fault verdict.
Reading a mover
- At −30m / At the trip — the channel's average over the first and last five minutes of the window, in its own units.
- Δ — the difference between those two, which is the number worth quoting in a report.
- σ — how many times the channel's own quiet noise it moved. This is what makes a jittery pressure and a still temperature comparable, and it is why a 2 psi move on a steady transducer can outrank a 20 °F wobble on a noisy thermocouple.
- Started — when that channel first left its own band and stayed out, with how many minutes before the trip that was. The order things started in is usually the whole story.
How the verdict is decided
- Mechanical — the furthest mover left its peers behind. One member of a family departing while the others stayed put is not something the process can do to a single cylinder, bearing or throw.
- Process — most of the family moved with it, by a similar amount. Load, ratio, cooling or gas composition, not one part. If a stage pressure moved in the same window, that is said too.
- Warm-up — the unit started inside the window. Every temperature is climbing from ambient, so how far each moved says nothing; the members are compared on where they ENDED UP at the moment of the trip instead. A member sitting well above its peers at that moment is still called mechanical, and the warm-up is disclosed in the wording.
- No cause in the log — nothing left its noise. An instant trip, a device that is not among the logged channels, or a stop somebody commanded. The tool says so rather than nominating the largest wobble it can find.
The verdict always names what it compared and what the peers did, so it can be checked rather than believed. Nothing here needs a unit profile, an Ariel run sheet or an assumed sensor polarity — it works on the first file a mechanic drags in.
- Open the View menu and turn on Trip analysis. Trips are stacked newest first — the one being asked about is nearly always the last.
- Read the strip at the top: how many trips, how many commanded stops, the median time between stops and the longest run in the log.
- Read the verdict, then the mover table underneath it, paying attention to the Started column.
- “Plot the movers and this flag” puts the top movers and the trip's own marker on the Trend chart and moves the range to the event. “Take the chart to this trip” just moves the range.
- “Copy summary” puts the inventory and every trip's verdict and movers on the clipboard as plain text for a service report.
Privacy
All of it is computed in your browser, like every other parse Overtrace does. No log, no shutdown cause and no unit identifier is uploaded to a server.
FAQ
Why did my compressor shut down?
Open View → Trip analysis on the log covering the event. Overtrace reads the 30 minutes before each recorded shutdown, ranks which channels moved against their own noise, shows when each started moving, and says whether one member of a family left its peers (mechanical) or the whole family moved together (process).
How do I tell a bad valve from a process problem in a datalog?
Compare the cylinder against its own peers in the same window. If one discharge temperature climbs while the others hold, the machine is at fault — the process cannot heat one cylinder on its own. If they all climb together, look at load, ratio, cooling or gas. Trip analysis does that comparison for you and shows the numbers behind it.
Why does a trip say “warm-up”?
The unit started inside the 30-minute window, so every temperature was rising from ambient and the amount each moved carries no information. In that case members are compared on the value they reached at the moment of the trip instead, which is what separates a genuinely hot cylinder from a machine that was simply still warming.
Does trip analysis need the Ariel run sheet or a unit profile?
No. Every number comes out of the log itself. The run-sheet-based tools are separate; this one works on the first file you load.
Why is a Manual Stop not analysed?
Because somebody pressed stop. It stays in the history and in the counts, but giving it a mechanical-or-process verdict would teach you to distrust the verdicts that matter. The movers are still listed if you want to see what the unit was doing.