The application of on-line wear debris monitoring technology to rotating equipment

Wear debris monitoring is the most effective technique available for detecting impending failure of oil-wetted components. The majority of aircraft, helicopter and industrial "Aero derivative" gas turbines operated today utilise magnetic chip collector (mag plug) inspections to detect the onset of oil-wetted component failures. However, successful chip collector usage depends upon timely inspection and the subsequent disposition / analysis and assay of recovered ferrous debris. Shortcomings in these critical maintenance actions, and / or wear modes which result in loss of function failures between scheduled inspection intervals, compromise the effectiveness of this method of wear debris monitoring. The Westland 30 and EH industries EH101 Helicopters both utilise the on-line monitoring system Tedeco QDM(R) on the Transmissions. The Helicopter, having only a single loadpath to remain airworthy, has a critical need for accurate indication of debris in the lubrication system. Industrial gas turbines operate for long periods at full load and under intense commercial pressure to minimise down time. The Rolls Royce and General Electric Aeroderivative Industrial fleet have benefited from the on-line Tedeco QDM technology for over 10 years. The reliability of the system, complimented by results obtained from the military B2 stealth bomber engine application, led to QDM being the logical selection for General Electric's latest and most advanced large fan Aero-engine. The General Electric GE90 QDM system is the first and only advanced, remote-indicating ferrous debris monitor qualified for commercial flight service continuously monitors the lube oil for the presence of wear debris. The system is capable of counting Individual debris particles and distinguishing their size, relative to a pre-set "target" threshold. These advanced features permit "on-condition" maintenance, and distinguish QDM from simple magnetic plugs and electric chip detectors, which may be subject to costly "nuisance" debris alarm indications. Performance and qualification requirements were developed throughout the mid 1990's in co-operation with General Electric and its French partner, SNECMA. The QDM system was qualified to customer specifications and released as standard equipment on initial GE90 entry into service. Field experience since service release has confirmed the system's ability to reliably and accurately indicate impending oil-wetted component failure well in advance of the loss of functionality. As technology and operators push the gas turbine for hotter, faster, lower cost of ownership and ever-higher reliability goals, the dependence upon on-line monitoring is paramount. The latest generation debris collecting and indicating system, the Tedeco I.Q.(R) system, indicates the accumulation of "Fine Debris", particles of less than 50 microns and above that gradually accumulate and indicate the earliest stages of rolling contact fatigue, (RCF), or cage lapping and bearing skidding failures. The second millenium will see the implementation of this system on the Eurofighter 2000 Typhoon and the FLA transport aircraft with the potential of retrofitting to existing large fan Powerplant and Helicopter Power trains including transmissions.