MNT.13:5 - Archetypal Grounding

APP-MNT-02 is a constructed comparison of 48 pumps. Twenty units have four relevant failures over 20,000 operating hours; 28 units have six over 56,000 hours. The rates are 0.20 and approximately 0.107 events per 1,000 hours. Raw counts favour the first group, while exposure-adjusted rates favour the second.

Neither result establishes a causal policy effect. The engineer recovers duty, component histories, event definitions and the reasons units entered each group. The answer to “Do these counts justify replacing the fleet policy?” is no on this basis. In the retention branch of this constructed case, the policy’s existing failure-and-response basis remains adequate for the stated duties; the counts do not establish that adequacy. Retaining the policy on that existing basis can be the completed decision while the support deficiency below is corrected. If that basis no longer holds, return the unsupported policy choice without waiting for these data to prove a rival policy.

The same current records identify an applicable spare unavailable for a known upcoming task. Correcting that support deficiency can be selected on its own evidence; the engineer does not wait for a new causal fleet study to address it.

If a different question warrants a policy comparison, its achievable design must account for the small event count, available population and operating constraints. It may support only a narrower conclusion. The first return remains valid without commissioning that further inquiry.