Controlled Fast Cooling Procedure
Controlled Fast Cooling Procedure Normally Rihand-II and III 500 MW units take 8-9 days to stop Barring Using CFCP, it takes roughy 75 Hours after Desynchronisation. It is done in 2 stages. First Stage: Unit Parameters Lowered By Reducing Load and steam Parameters. Second stage: After Desynchronisation, till 350 Deg( HP Casing Temp), it is to be cooled thru Natural Cooling. thereafter by Modulating HPCV and Vacuum( Forced Cooling) maintaining Drop rate 5-6 Deg/Hour. During this : Top/Bottom DT, Differential Expansions, Axial shift, Bearing Temperatures, Bearing & shaft Vibrations need to be Observed and Logged in the sheet and if any Deviation Found, should be rectified.And if these deviations are beyond rectification, then abort force Cooling. Stage I : Parameters Reduction on Load: Ensure all Auto Loops and SLCs in service and MS Temp <480 deg to be bypassed in order to lower Temperature. (Desk, Control Desk, SCE & C&I with Proper logging in Register)...