From measurement collection to remaining useful life estimation: defining a diagnostic-prognostic frame for optimal maintenance scheduling of choke valves undergoing erosion

Condition Based Maintenance (CBM) aims at regulating maintenance scheduling based on data analyses and system condition monitoring. Clear advantages of optimizing maintenance scheduling include relevant cost savings and improved safety and plant availability. A critical aspect is the integration of CBM strategies with condition monitoring technologies for handling a wide range of information sources and eventually making optimal decisions on when and what to repair. In this work, a practical case study concerning maintenance of choke valves in offshore oil platforms has been investigated. Choke valves used in offshore oil platforms undergo erosion caused by the sand grains transported by the oil-water-gas mixture extracted from the well. Erosion is a critical problem which can affect the correct functioning of the valves, result in revenue losses and cause environmental hazards. In this respect, this work proposes a diagnostic-prognostic scheme for assessing the actual health state of a choke valve and eventually estimating its Remaining Useful Life (RUL). In particular, the focus has been on the identification of those parameters which contribute to the actual erosion of the choke valve, the development of a model-based approach for calculating a reliable indicator of the choke valve health state, the actual estimation of the choke RUL based on that indicator using statistical approaches and, finally, the investigation of methods to reduce the uncertainty of the RUL estimation by adding highly meaningful knowledge on the erosion state of the choke valve.