Condition Monitoring of an Electro-Mechanical Shear Ram Actuator
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The changeover from electro-hydraulic to all-electric control systems in blowout preventers (BOP) are expected to improve the abilities of condition monitoring and early detection of system faults. This is an interesting topic on both authority and user level, and can be used to improve system reliability and decision support systems for condition-based maintenance. Electrical Subsea \& Drilling has developed an all-electric BOP control system design. The design includes an electro-mechanical shear ram actuator that serves as the driving force for the shear ram block, which is a closing element designed to cut the drill pipe and seal the wellbore, and is normally used as a last resort if well control can not be restored. The actuator consists of electric motors and mechanical transmissions, and has been studied in order to investigate its condition monitoring capabilities. A mathematical model of the shear ram actuator has been developed in Matlab/Simulink by use of the Simscape environment. In total four mechanical faults are implemented in the model, and investigated through analysis of data obtained from simulations of the model. The faults studied regarded planetary gear tooth cracks and wear, bearing damage and increased shear ram friction. The results of this study indicate a potential for detection of all faults considered, by analysis of system parameters such as stator currents and vibrations in the torsional and translational response of mechanical components.