Why : To take out certain running Mills out of service as per preference in order to reduce firing and compensate for the furnace conditions prevailing…
When :
- On Turbine trip
- Load rejection >50 %
- Single FD or PA fan running
How : It ensures that extreme burners shall trip
Under 4 mill condition
- if Mill D is not in service then Mill A trips
- If Mill A is not in service then Mill D trips
- If both Mill A and Mill D are in service, Mill A trips if Mill D is the single Mill in the rear OR Mill D trips if
- Mill A is the single Mill in the front
- If Mill A and Mill D both are not in service then Mill B trips
Under 5 mill condition
- Mill A and Mill D trips if they are both in service
- Mill A and Mill B trips if Mill D is not in service
- Mill B and Mill D trips if Mill A is not in service