Incident report INC-PT104-001

Sample cell: Blue Ridge Lab · PT-104 Pump Skid · PT104_Lab_PLC (sample) · Read-only

This document is a demonstration of the report a pilot incident produces. Every fact below is drawn from the public PT-104 sample fixture; it describes no real plant and no customer evidence.

Question

“Why will Pump 4 not start?”

Finding

LS-104 low-low is blocking the start permissive.

In the read-only sample snapshot observed 2026-08-29 14:12Z, the start request, automatic mode, emergency-stop chain, and PowerFlex-ready state are satisfied while LS_104_LLO is active. The normally closed LS_104_LLO instruction therefore evaluates false, breaking rung continuity before P104_START_PERM. This establishes the blocking condition for that snapshot only; the physical root cause (a true low-low level versus a switch, wiring, or input-channel fault) is not yet established and requires field corroboration.

Status: blocking condition established for the 2026-08-29 14:12Z sample snapshot; physical root cause not yet established by logic alone — a true low-low level, or a switch, wiring, or input-channel fault, is exactly what the field check observes and records.

Bounded hypotheses

#	Hypothesis	Rationale
1	Process low-low interlock is legitimately active	The logic and read-only snapshot agree that LS_104_LLO is active while the rest of the start chain is satisfied.
2	Field switch, wiring, or input-channel fault	The drawing maps the signal to X2-17 and slot 4 channel 7, but no current field evidence confirms the physical state.
3	Unexpected logic or drive fault	The reviewed rung and drive export do not support either condition.

Next approved action · authority: read-only

Verify the field state: Under the approved read-only procedure, compare the LS-104 field indication with terminal X2-17 and the slot 4 channel 7 input LED. Capture a photo in Mobile Field Check. Do not bypass the interlock.

Stop conditions, on screen at every step:

Arc-flash boundary cannot be maintained
Unexpected cabinet condition
Technician lacks cell authorization
Process safety state is unclear

Field task issued to Mobile Field Check

Compare the LS-104 field indication with terminal X2-17 and the slot 4 channel 7 input LED, exactly as found, and capture one field photo and one cabinet photo.

Cited evidence

ID	Source	Version	Observed	State	Supporting fact
EV-R27	Routine P104, rung 27	L5X sample export BRPLC-PT104-V12	—	verified	P104_START_PERM requires START_REQ, AUTO_MODE, NOT ESTOP_ACTIVE, NOT LS_104_LLO, and VFD_READY.
EV-SNAPSHOT	Read-only sample tag export	—	2026-08-29T14:12Z	observed	START_REQ=true AUTO_MODE=true ESTOP_ACTIVE=false LS_104_LLO=true P104_START_PERM=false
EV-VFD	PowerFlex sample fault export	—	2026-08-29T14:12Z	extracted	VFD_READY=true Active fault count=0
EV-E104	Electrical drawing E-104	Drawing E-104 rev C	—	verified	LS-104 terminates at X2-17 and maps to slot 4 channel 7.

Simulated review note

In the pilot workflow a controls engineer reviews this trace and the field observation on a scheduled basis before the incident closes. This sample shows the record shape; the review shown on the public site is simulated, and no engineer reviewed a real plant for this document.