Trash rack fouling on the intake of a hydro unit poses a reliability problem as the differential head across the rack increases. Excessive fouling may cause the trash rack to fail, resulting in high repair costs and revenue loss due to downtime and the cost of replacement power. However, even minor amounts of fouling can be costly to a hydro system. Trash rack fouling dissipates energy and reduces the effective hgead across the turbine, resulting in appreciable losses of energy and capacity. Losses in capacity due to fouling increase both the risk and the amount of spill. In addition, the accumulation of trash produces a non-uniform flow distribution, causing the unit to deflect. The resulting changes increase maintenance costs by accelerating the wear on turbine guide bearings and thrust bearings and create an adverse operating condition that increases the likelihood of cavitation.
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