Revision to the concept of equilibrium concentration of particles in lubrication system of machines

This paper analyzed the numerical characteristics of distribution function of particles concentration in oil cycle system of machines by solving the stochastic differential equation, then revised the concept of equilibrium concentration of particles and put forward a new concept-stationary concentration. It is proven that the particle concentration in a machine tends towards a wide-stationary process from a non-stationary process in the condition that the running parameters are constant and the white noise is introduced as a random component. The statistics histogram of data distribution obtained by on-line ferrograph showed different distributions depending on whether running parameters are varied or constant, and it confirms the theoretical analysis. Eventually, a new oil sampling concept is advanced for oil condition monitoring and ferrography. That is oil sampling should be on-line sampling or of larger volume (> 100 ml) for off-line sampling in order to get the time mean and space mean.