Patent ID: 7370514
Filing Date: 2008-05-13
Classification: G01N

Abstract:
1. A method of determining remaining useful life of a quantity of oil in use in fluid lubrication of an operating mechanism, the method comprising: repeatedly determining resistivity (ρ) values of the oil at an predetermined oil temperature during operating time intervals of the mechanism; recording a resistivity-time ρ(t) history of the oil such that, as successive resistivity values starting with an initial value are accumulated with elapsed operating time, a continuous ρ(t) linear curve is formulated that includes; (1) a first portion with a slope of dρ/dt>0 up to a first time t comparing, from time to time, the then existing portion of the ρ(t) curve with like predetermined data on a like or functionally comparable oil composition; using the comparison to predict the remaining useful life of the oil; continuing to record a resistivity-time ρ(t) history of the oil so that a continuous ρ(t) linear curve is formulated that further includes; (3) a second portion with a slope of dρ/dt<0 during which values of ρ decrease up to a second time t continuing to compare, from time to time, the then existing portions of the ρ(t) curve with like predetermined data on a like or functionally comparable oil composition and using the comparison to predict the remaining useful life of the oil; continuing to record a resistivity-time ρ(t) history of the oil in the third portion of the ρ(t) curve until time t generating a signal indicating that the useful life of the oil has been depleted.