Use case 01 · Recurring trips

A charge pump that keeps tripping on low suction pressure

Each trip was reset within minutes and closed as “no fault found”. Nobody had looked at all six together. Valqor lined them up against the feed tank level, the alarm log and the shift notes.

Illustrative example based on a common failure pattern
Equipment
P-205 centrifugal charge pump, fed from tanks T-20A/B
Symptom
Trips on the low suction pressure interlock, six times in ten weeks
Data used
Historian: 6 tags over 10 weeks · Alarm and event log · 9 work orders · Shift logs
01 · The pattern

What the data shows

Suction pressure tracks the feed tank level closely. Every trip happens at the bottom of a tank draw-down, when the level falls below about 25% before the operators switch tanks.

P-205 suction pressure and feed tank level, 10 weeksSuction pressure (bar)Feed tank level (%)Pump trip
0.50.01.9503.2100Jul 21Aug 4Aug 18Sep 1Sep 15Sep 29Trip setpoint 1.2 bar

Each trip sits at the bottom of a tank draw-down.

02 · The sequence

The sequence around trip 4, Sep 14

Historian readings, alarms, operator notes and work orders, lined up on one timeline.

  1. Operator logShift handover. Tank switch T-20A to T-20B noted as “next round”.
  2. HistorianT-20A level 24% and falling at 0.9% every 10 minutes.
  3. AlarmLI-201 low level alarm on T-20A. Acknowledged.
  4. HistorianP-205 suction pressure 1.5 bar. Flow steady at 48 m³/h.
  5. AlarmPI-205 low suction pressure alarm.
  6. AlarmP-205 tripped on the low suction pressure interlock.
  7. Operator logLined up T-20B and restarted P-205.
  8. Work orderWO-4471 “P-205 trip, reset, no fault found.” Closed.
03 · The causes

Likely causes, tested against the evidence

Each candidate cause is checked against the records, with the evidence for and against it shown side by side.

Low suction head during late tank switching

Supported

Evidence forAll six trips came within 40 minutes of a tank switch, with the level below 25%. Suction pressure follows the level.

Evidence againstNone found in the available records.

Suction strainer plugging

Weak

Evidence forOne work order from May records a strainer clean on P-205.

Evidence againstStrainer differential pressure stayed at 0.1 bar before every trip.

Faulty suction pressure transmitter

Ruled out

Evidence forNone.

Evidence againstThe redundant transmitter PI-205B read the same values within 0.05 bar.

04 · The outcome

Finding and recommended actions

An engineer reviews the finding and the linked records before any action is taken.

P-205 trips when the feed tank is drawn below about 25% before the switch to the standby tank. Four of the six trips happened within an hour of a shift handover, when the switch was left for the next round.

  • Switch tanks at 35% level, and write the switch point into the operating procedure.
  • Add a pre-alarm at 30% tank level so the switch is prompted before suction pressure falls.
  • Confirm the pump’s NPSH margin at low tank level with the vendor curve.
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See the investigation

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