Developments and thoughts on operational reliability assessment of mechanical equipment

Operational reliability assessment of the specified mechanical equipment is an individual problem. The average reliability, obtained by using probability statistics method with large sample data, cannot fulfil requirements of operating reliability evaluation for individual equipment. The emerged problems are summarized when the traditional reliability theory is applied to operational reliability assessment of mechanical equipment, and corresponding improved methods are reviewed. The theoretical basis and technical connotation of operational reliability assessment for individual equipment, which is based on dynamic modelling, fault mechanism analysis, signal processing and fault feature extraction, are expounded. Then, a new concept of operational reliability is given and the degree of operational reliability is defined. An operational reliability assessment approach based on running condition information of mechanical equipment is proposed. Mapping models between running condition and operational reliability is established for mechanical equipment to calculate the degree of operational reliability. Based on ISO3945, absolute vibration values which are used to evaluate running condition of rotating machinery are transformed to reliability degree. The proposed method is applied to a turbogenerator set with bearing bush looseness before/after repair, and rolling bearings which degrade from normal to failure state under continuous running condition. Good results are achieved, which validate the method. The unsolved problems for operational reliability assessment of mechanical equipment are brought up, which may provide reference for the further research.