Single-number statistical parameters in the assessment of the technical condition of machines operating under variable load

Diagnosing machines operating under variable load requires the use of special signal analysis methods. In literature there are many methods based on synchronic analysis where vibration signal is synchronized with shaft rotation of the diagnosed machine. Varying load, however, also affects the amplitude of diagnostic parameters values. The paper deals with the problem of diagnosing machines operating under variable load. The impact of load on the diagnostics parameters values has been tested on a laboratory station. Due to varying rotational speed, the diagnostic parameters were amplitudes of orders determined by means of order analysis synchronized with the shaft rotation in the diagnosed drive unit. Examined was the impact of varying load on the diagnostics effectiveness of damage, such as incorrect motor mount (soft foot) and misalignment of shafts. Single-number statistical parameters were proposed to determine the technical condition of machines operating under variable load.