Layered process audit (LPA) is the method of auditing the same production point by different levels of management, at different frequencies and with short checklists.
The aim is to verify that standardized work is actually applied on every shift.
Difference from internal audit
An internal audit is conducted a few times a year and evaluates the system as a whole. LPA works at a daily rhythm, with a narrow scope and on the shop floor.
What does “layered” mean?
The shift supervisor looks at the same points every day, the department manager once a week, the plant manager once a month. This structure produces two benefits: deviations are caught quickly, and management is in regular contact with the shop floor.
Design rule: keep it short
The most common mistake in practice is turning the LPA into a long checklist. The longer the list, the more the audit is either not done at all or done perfunctorily.
Effective LPA questions should be short, targeted and verifiable by observation. The PFMEA and past nonconformities are a good source for question selection.
Recording findings immediately and tying them to corrective action follow-up is what determines the value of the method.
Programme design, the layer and frequency matrix and writing the question list are addressed in the CQI-8 layered process audit training. For the general framework of audit methodology, see the ISO 19011 training.