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Electric Master Chip Detector

Electric Master Chip Detector

A Vickers Electric Master Chip Detector (EMCD) and nine Muirhead Vatric screw−in magnetic chip detectors are installed in the return oil system to allow monitoring of the following:

  • Front Bearing Housing
  • Internal Gearbox (Front)
  • Internal Gearbox (Rear)
  • HP Turbine Bearing Chamber
  • IP Turbine Bearing Chamber
  • LP Turbine Bearing Chamber
  • Intermediate and Lower Bevel

  • External Gearbox
  • Centrifugal Breather
The EMCD is installed in the combined scavenge return line on the forward side of the oil tank. There are nine ports on the bottom of the oil pump which can be used to install additional MCDs.
During normal engine operation, only the Master EMCD is installed. If metallic particles are found on the EMCD during the inspection, diagnostic MCD‘s can then be installed to isolate the source of the debris.
Electric MCD
The Electric MCD is positioned at the inlet to the scavenge filter and collects ferrous metal particles from the engine oil. The head of the EMCD has two electrically isolated magnetic poles. A circuit is made when debris bridges the two poles. The EMU continuously monitors the EMCD during flight and generates an EMCD debris maintenance message 10 secs after landing which is sent to the Aircraft via the EEC.
Screw−in MCD
The screw−in MCD assembly consists of a housing and Magnetic Chip Detector, which has a magnetic end. When the MCD is installed the magnetic end is located in the return (scavenge) oilways. The MCD housing contains a self−closing check valve to prevent oil leakage when the MCD is removed for inspection. If metallic particles are found on the EMCD during the inspection, MCDs can be installed in the ports on the oil pump assembly. This allows the problem to be isolated by checking each scavenges oil line.
EMCD INSPECTION(AMM TASK 79−00−00−200−802)
ATTENTION: Warnings and Cautions: Observe all Warnings and Cautions are given in the AMM
The procedure in the AMM is briefly described below: On the OMT, get access to the Power Distribution Control management pages and open & safety the applicable circuit breakers.
  • Open the right fan cowl door-
  • Remove the master EMCD
  • Put the master EMCD probe into clean kerosene and remove the oil (The kerosene should be in a clean non−metallic container) 
Make sure you do not contaminate the electrical contacts with kerosene.
 Be careful to only remove the oil from the EMCD and not any contamination, which may be present. Examine the master EMCD in good light for contamination using a 05X magnifying glass Refer to the contamination standards in the AMM.
  •  Keep all contamination which does not cause you to immediately reject the engine or gearbox as a record. Take a piece of 25mm (1 inch) wide transparent self-adhesive tape preferably Scotch Magic Tape (OMat 1269) approximately 50mm long and apply the center of the gummed side over the recessed insulated debris gap. It may require several attempts to remove all the debris with the same piece of tape.
1. The contamination record will help you monitor the type of wear in the engine or gearbox.
2. Laboratory analysis is recommended to help with material identification.
3. If the contamination is outside the permitted standards you must refer the contamination to Rolls−Royce for recommended action.

 credit by Chhawinder 

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