When two dissimilar materials are placed in contact and then separated in a sliding motion, it results in electron transfer between the two materials. This is referred to as triboelectric charging. Frictional contact between fluid and filter media in a lubrication or hydraulic system results in triboelectric charge generation that, if not dissipated, accumulates and discharges to a lower potential surface. It’s like a lightning bolt in a filter housing. With technology and fluid formulations changing, more challenging operating conditions for fluid systems are created, and triboelectric charging becomes more prevalent. Higher machine speeds, higher operating pressures, more demanding duty cycles, and highly refined, lower conductivity fluids each contribute to triboelectric charge buildup. Nonpolar materials yield higher charging, as do higher fluid velocity, higher fluid viscosity, lower fluid conductivity, lower moisture content, and more contact areas. Filters with large surface areas combined with full flow features of filter elements in particular yield higher charging.