7.4 Layered Process Audits (LPA)

Inspection checks the product;product; AuditsLPAs check the process. A perfect product made by a rogue process is a ticking time bomb. Layered Process Audits (LPA) are the immune system of the factory floor. They are high-frequency, short-duration verificationschecks performed by multiple levelslayers of management to verifyenforce process disciplinestandardization and preventdetect standardization"process drift.drift" before it becomes a defect. If the Plant Manager never walks the line, the line assumes quality is optional.

The Physics of "Drift"

Processes naturally degrade. Tools wear, attention wanders, and "tribal knowledge" replaces the SOP. LPAs provide the activation energy required to maintain the steady state.

The Tiered StructureLogic:

• Tier 1 (Daily / Shift): Performed by LineTeam Leads or Supervisors.Leads.

  • Focus:Mission: "Immediate containment.
  • Action: Check the inputs. Is the torque driver calibrated? Is the operator followingwearing thea Standardheel Work?strap? Is the ESDrevision wrist strap connected? Ison the correctscreen revision of the drawing displayed?"correct?

• Tier 2 (Weekly): Performed by Quality Engineers or Quality/Manufacturing Engineers.

  • Focus:Mission: "IsSystem verification.
  • Action: Deep dive. Are the documentation"Red current?Rabbits" (master failures) working? Is the testchemical fixturelog calibrated?up Areto non-conforming parts properly red-tagged?"date?

• Tier 3 (Monthly): Performed by Plant Leadership (Plant Manager,Mgr, Ops Director)Dir).

  • Focus:Mission: "AreCultural enforcement.
  • Action: Verify the Tierverifiers. 1 andAre Tier 1/2 audits actually happening?happening, Areor systemicis issuessomeone being"pencil fixed? Iswhipping" the culture of quality visible?"data?

The "Yes/No"Binary Question Rule 

LPA questions must be binary and objective. Ambiguity is the enemy of auditing.compliance. Never ask an essay question on a checklist.

Question Design Logic:

• Bad Question:Bad: "Is the stationworkstation clean?organized?" (Subjective)Subjective opinion).
• Good Question:Good: "Are there any loose components or debrisunlabelled bins on the workbenchactive surface?" (Objective)Binary Yes/No).
• Bad: "Does the operator know the process?"
• Good: "Can the operator demonstrate the 'Stop Call Wait' protocol for a failed unit?"

Pro-Tip: If an audit question takes more than 10 seconds to answer, delete it. LPAs should take 10 minutes total. If they are burdensome, they will be faked.

Immediate Correction (The "Fix It Now" Rule)

An LPA is not a data-gathering exercise; it is a correction exercise.

Reaction Logic:

• If a non-conformance is found (e.g., loose torque seal) → Then fix it immediately. Do not just tick "Fail" and walk away.
• If the issue cannot be fixed instantly (e.g., broken fixture) → Then stop the line and tag the equipment.
• If the same failure repeats 3 times in a month → Then the Process is broken, not the Operator. Launch a CAPA.

Final Checklist

AuditControl TypePoint	FrequencyCritical Requirement	Auditor	FocusRisk Avoided
LPA Tier 1 Frequency	Daily (Every Shift)Shift, every line.	LineImmediate Lead	OperatorProcess Discipline / SafetyDrift
LPA Tier 23 Participation	WeeklyPlant Manager must conduct ≥ 1 audit/month.	Engineer	Process"Quality Inputsis /just Documentationfor Quality Dept" mindset
LPAQuestion TierStyle	Binary 3(Yes/No) only. No subjective rating scales.	Interpretation Bias
Duration	MonthlyMax 10-15 minutes per audit.	Manager/Director	SystemAudit HealthFatigue / LPAFalsified IntegrityRecords
Reaction Plan	Correction on the spotImmediate for minor issues.	Auditor	FixNormalization "No"of findings immediatelyDeviance