Machinery condition monitoring is the systematic and regular measurement of parameters of a machine (vibration, temperature, pressure, wear debris, oil condition, etc.) that reflect the actual physical condition of the machine, while it is operating or during routine down periods, in order to detect the onset and development of deterioration or faults. The measured values are recorded and compared against baseline/reference values and trended over time so that the rate of change and the approach of the machine to a failure limit can be assessed. Its purpose is to plan maintenance on the basis of actual condition (condition-based maintenance) rather than on a fixed calendar or running-hours schedule, so that a component is serviced just before failure occurs, avoiding both unnecessary overhaul and unexpected breakdown. It allows early warning of developing faults, extends machinery life, reduces downtime and maintenance cost, and improves safety.

1. Vibration monitoring: Using portable or permanently installed vibration analysers/ accelerometers. Measurements of overall vibration level and of the vibration spectrum (frequency analysis) are taken at designated measuring points (bearing housings of the engine, turbocharger, pumps, purifiers, generators). Readings are compared with the baseline and with the ISO/classified machinery vibration standards, and trended.
2. Temperature monitoring: Jacket cooling water, exhaust gas, scavenge air, bearing metal and oil temperatures, measured with thermometers, thermocouples or resistance temperature detectors, and compared against alarm/limit settings.
3. Pressure monitoring: Cylinder compression and firing pressures, scavenge air pressure, lubricating oil and cooling water pressures, recorded and trended against load.
4. Oil analysis / tribology: Regular sampling of lubricating oil (engine, purifier, gearbox, stern tube) sent to a shore laboratory or tested on board for wear-metal content (spectrometric analysis), TBN, viscosity, acidity, water, insolubles. Rising wear-metal concentration indicates bearing/piston/liner wear.
5. Wear measurement: Internal micrometer measurements of cylinder liner bores, piston ring/groove clearances, crankshaft deflection readings, bearing clearances (bridge gauge readings), taken at survey intervals and recorded against running hours.
6. Performance/indicator analysis: Draw and analyse indicator diagrams (p-compression, p-max, power) and out-of-phase diagrams; calculate specific fuel consumption to detect combustion deterioration.
7. Visual and ultrasound inspection: Borescope inspection of combustion spaces, listening, and ultrasonic thickness measurement of pipes and shells.

The key is trend analysis. A single reading is of limited use; it is the change with time that indicates condition. By plotting a measured parameter (e.g. bearing temperature or vibration velocity mm/s) against running hours or calendar time, a baseline operating band is established. A slow, steady rise within the band shows gradual, normal deterioration; an accelerating rise forecasts an approaching failure; an abrupt step change indicates a sudden fault. The gradient (rate of change) of the curve is used to predict the remaining useful life until it reaches the alarm or trip limit. By comparing trends across engines and across measuring points, engineers can identify which component is degrading, can schedule the overhaul before failure at the most convenient time (e.g. in port), can optimise spare-part usage, and can evaluate whether an earlier repair was effective (the trend should return to the baseline). Thus monitoring converts routine maintenance into predictive, condition-based maintenance, giving early warning and allowing the machinery to be operated safely until a planned intervention.