Explain the maintenance decision with evidence
Return to the shift question and explain both the inspection scope and the first stop among three HIGH machines.
Question for this chapter
Which machine goes first, and what evidence supports that decision?
Return to the original problem
All three alerts were HIGH, and all three machines had a health score of 90. There is no evidence to
release two machines as normal. The solution is to keep every inspection in scope while making the first
action transparent.
Complete the solution
| Initial problem | Applied solution | Evidence left behind | What changed |
|---|---|---|---|
| Three sensor types used unlike units. | Read values with quality_flag. | Three HIGH_* rows | The source of each alert is explicit. |
| Raising sigma seemed likely to remove alerts. | Reran 3.0 and 3.15. | Same three HIGH rows | Statistical and status rules are separate. |
| Three machines were tied. | Split health priority from the z-score tie-break. | Three scores of 90; CNC-03 at 2.83 | Inspection scope and first stop are separate decisions. |
| An alert row lacked field context. | Connected machines, sensors, and events. | CNC-03 maintenance event | The crew can resume from the same incident. |
State the final decision
CNC-03, CNC-05, and CNC-09 all have
HIGHalerts from explicit quality signals, so isolate and inspect all three. For one crew's starting point, the workshop tie-break selects CNC-03's vibration sensor, which has the largest relative deviation, followed by CNC-09 and CNC-05.
Completion check
- Found the three
HIGH_*quality signals among 20 sensor rows. - Can explain the difference between the three-sigma rule and an explicit status signal.
- Confirmed why sigma 3.0 and 3.15 produce the same result.
- Confirmed that all three machine health scores are 90.
- Traced CNC-01's three sensors and CNC-03's maintenance event separately.
- Can separate the inspection set from the first inspection.
Apply next
In real maintenance work, put safety class, asset criticality, production impact, and the maintenance SOP ahead of z-score in the tie-break rule. The important part is to make the rule visible so every crew can reproduce the same decision from the same evidence.