Condition Monitoring
Debris Tester Function
Purpose and Function of Debris Testing
The Debris Monitor 4 is used for the routine determination of the rate of wear of oil lubricated parts in Gas Turbine Engines, Gear Boxes and Transmissions.
The Debris Monitor 4 provides an early failure detection system for those components which are subject to the highest stress levels, such as ball and roller
bearings and gears.
Components working at high stress levels exhibit three distinctive wear phases:
Phase 1 is the a running in period in which small surface roughness is worn
or broken away. Particles are therefore small and initially many, but the rate of production diminishes quickly.
Phase 2 is normal operation. In this phase the wear is light, the particles
small and only produced in low quantities.
Phase 3 is the failure period and starts when a localized spot on a stressed component starts to break up. Comparatively large particles now break away leaving pits that further degrade the surface increasing wear on the component.
The Debris Monitor 4 function is to quantify the amount of ferrous particles in
debris removed from oil filters or magnetic plugs from any machinery but particular applications are gas turbine engines, helicopter gearboxes and diesel engines.
Debris testers are generally used where the generation of wear debris is normally very low but failure of the component can mean a safety hazard or a high cost repair.
Readings from debris samples are plotted on a graph against total engine running hours. In normal operation, a steadily rising value of D.T.U.'s ( Debris Tester Units ) coupled with increasing running hours is usual since normal wear is
taking place within the component at points of highstress. If the wear within the component suddenly increases, a sharp increase of the D.T.U. reading is plotted on the graph as a sharp upward gradient. This indicates the possibility that the engine or gearbox is entering 'phase three' of the wear cycle and thus provides an early warning of impending serious or catastrophic failure of the component.
