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CONDITION MONITORING FOR FAULT DIAGNOSIS OF COAL MILL GEAR BOX OF A POWER STATION
N.K.P.Reddy*

This thesis deals with application of condition monitoring for fault diagnosis of coal mill gearbox of Rihand Super Thermal Power Project, (2 X 500MW), NTPC. There are total sixteen gearboxes in both the units. In power plants, non-availability of coal mill causes generation loss and unscheduled power cut offs at the consumer end. The gearboxes of these coal mills are very big in size and require lot of time and resources to replace them and hence it is selected for the project study. Condition monitoring is well established to detect faults and will aid to avoid any unscheduled failures of these gearboxes. Vibration analysis and oil analysis have been applied to monitor the condition of these gearboxes.

The past available overall vibration records of all the sixteen gearboxes are collected from the project for initial estimation of the condition of these gearboxes. The data is analysed and trend analysis was carried out. Due to time limitation, four gearboxes 1A, 1E, 2C and 2E were selected among all sixteen for vibration measurement and oil analysis. However, a major emphasis is given for analysis of the gearbox 2C, as it is running with high vibrations for the last two years. Out of these four, 1E is having low vibrations and other three are running with high vibrations. Therefore gearbox 1E is selected for comparison purpose.

Vibration measurements of the four gearboxes were taken for frequency analysis. The result of frequency analysis of these gearboxes and ferrography of mill 2C are discussed, in addition general physical and chemical properties of oil are also monitored to know the lubricant oil condition and the gearbox components. The results are also analysed and discussed. Based on this a methodology is proposed for project implementation.

Keywords:- Vibration monitoring, Oil analysis, Power plant and Coal mill gearbox


* Mr. N.K.P.Reddy is presently working as Supdt. (MTP) in Simhadri Super Thermal Power Project of NTPC. His communication address is - Simhadri Super Thermal Power Project, P.O. NTPC-Simhadri, Distt.-Visakhapatnam (A.P.) -531020.
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