Quantifying the Reliability Impact of ISO 10816-7 Vibration Severity Zones in Centrifugal Pumps Using Proportional Hazards Models

Excessive vibrations in rotating machinery accelerate wear and component failures, causing undesired downtime in industrial plants. To assess the severity of these vibration levels, ISO 10816-7 classifies pump condition into four zones. Zone A represents good condition, Zone B is acceptable for long-term operation, Zone C is generally suitable only for limited operation, and Zone D corresponds to vibration levels that may cause machine damage. However, these qualitative classifications do not quantify how vibration severity relates to equipment reliability. This paper addresses that gap for rotodynamic pumps by integrating standardized vibration severity levels within a reliability framework based on Proportional Hazards Models (PHMs). The models were fitted with observational field data from an oil refinery using the Mean Time Between Failures (MTBF) as the reliability outcome. From the resulting survival curves, reliability is summarized by the median predicted life (B50), defined as the time at which the predicted survival probability reaches 0.5. This measure can be estimated within the observed follow-up without extrapolating the censored tail of the survival curve. The model achieved a concordance of 0.870 and was then used to estimate B50 across a range of vibration levels, holding the remaining operating conditions constant. The analysis indicated an association between the vibration levels and the predicted life, consistent with the severity considerations set by the ISO standards. The results showed a 62.5% decrease in mean predicted B50 from Zone A to Zone D. Within the 0–6 mm/s RMS range, which contained 95% of the observed vibration data, prediction uncertainty remained comparatively low, whereas it increased at higher vibration levels as data density decreased. Across speed and power groups, at a given vibration level, higher rotating speeds and higher installed power are associated with higher predicted lives. American Petroleum Institute (API) 610 between-bearings pumps showed higher predicted reliability than horizontal overhung and vertical overhung OH6 configurations. By providing a quantitative mapping from ISO severity levels to predicted equipment life and its practical implications for reliability-oriented maintenance planning, the proposed approach adds numerical resolution to current standards and supports more informed, data-driven maintenance and reliability decisions for centrifugal pumps.