Preventative maintenance inspections are the looking half of a preventive programme: a technician examines an asset at an interval, measures what can be measured, and records the condition, without necessarily changing anything. What is a preventive maintenance inspection as against a service is exactly that distinction: the service replaces and adjusts on the interval regardless; the inspection decides. This page explains the difference, what the inspector looks for, how the finding becomes a corrective work order, and why inspection-based maintenance suits assets with a failure mode that develops slowly.
Inspection against service
A service does the task on the interval whether the asset needs it or not: change the oil, replace the filter, tighten the belt. An inspection checks the condition and raises work only if the condition demands it: measure the belt tension, read the bearing temperature, look at the seal. Services suit parts that wear predictably; inspections suit assets where the P-F interval is long enough to catch the failure developing. Most schedules mix the two on the same asset.
What the inspector looks for
Whatever the failure modes for that asset class say will show first: heat, noise, vibration, leaks, wear, looseness, contamination, readings drifting from normal. Each item on the inspection checklist is a symptom with a limit, and the inspector records the reading, not just whether it passed. Readings over time are the P-F curve drawn from the site's own asset, and they are what let the next inspection interval be set with evidence.
What happens to a finding
A finding outside the limit becomes a corrective work order against the asset, with a priority set by how close to failure the reading is, and it is planned rather than done on the spot unless the reading is critical. That is the whole point: the inspection has bought the site time to do the repair as a planned job at 1.1 hours instead of a breakdown at 3.4, in this site's worked example. A finding that is fixed silently on the spot and not recorded costs the site the history that would have set the interval.
Setting the inspection interval
Shorter than the P-F interval for the failure mode, with margin to act. Where the history does not yet say what that is, start from the manufacturer's interval and the technicians' judgement, and shorten it if failures arrive between inspections. Lengthen it if a year of inspections finds nothing, because an inspection that never finds anything is either on the wrong asset or too frequent.
Questions people ask about preventative maintenance inspections
Is a walk-round an inspection?
Yes, the shortest kind: a daily look and listen against a short checklist. It catches the obvious early and costs minutes.
Who should do preventive maintenance inspections?
A technician who knows the asset class, or an operator trained on the checklist for the daily items. The record matters more than the job title.
Do inspections need instruments?
Some do: a thermometer, a vibration pen, a gauge. Most daily and weekly items are a trained eye and hand. Instruments move the P point earlier and are worth it on the assets that matter.