OFFICE OF THE GENERAL MANAGER / O&M

Guide lines for Boiler Operation

1. RAPH steam soot blowers shall be operated once in every shift.

2. During oil firing, RAPH steam soot blowers shall be operated continuously.

3. Coils steam soot blowers shall be operated daily once, when the load is more than 80%, preferably in the I-shift beginning itself along with RAPH steam soot blowers after Water Lance Operation.

4. Water lances shall be operated, when the load is more than 80%, twice in a week (or) more frequently if the total SH Spray Water Flow is more than 110 T/Hr (or) if the furnace exit temperature is steadily rising above 900(C (or) if more slagging is observed on the water walls during any inspection of the furnace.

5. Whenever reserve mill is available, diagonally opposite mills (such as B&D, C&E, A&F) shall be kept in service for better firing condition.

6. As the unit is designed for FULL LOAD with 4 mills, always only 4 mills shall be kept in service for FULL load, unless specifically warranted due to any loading problem in running mills.

7. If the Boiler is stable with 3 Mills, Oil burners need not be started except for Furnace instability.

8. As far as possible all the control loops shall be maintained in AUTO. Even during any emergency, the BIAS facility available in all control loops shall be used judiciously to tide over the situation instead of taking the control into MANUAL. Only in case of AUTO controller failures or absolute necessity they should be changed to manual control with due care.

9. During Unit Run Back Operation, in case of tripping of any one RAPH, ID Fan, FD Fan, operating engineers intervention shall not be there up to the stabilization of Unit load. But all the important parameters, such as Unit load controller, Mills condition, Drum level, Furnace pressure, Fans & RAPHs condition, shall be monitored continuously. After unit stabilization, cause for trip of the equipment shall be analysed, rectified and shall be started again, if possible immediately. In case of non-availability of one series of equipment for longer duration, Unit load shall be stabilized with only 3 MILLS. Oil burners need not be started except in case of furnace instability.

10. During Unit Run Back Operation, in case of tripping of any one Boiler Feed Pump, if the reserve pump comes into service immediately, operating engineers intervention shall not be there up to the stabilization of Unit load. But all the important parameters, such as Unit load controller, Mills condition, Drum level, shall be monitored continuously. If the reserve Feed Pump does not come into service in Auto, this shall be started immediately manually, to tide over the emergency. In case of non availability of reserve Feed Pump, as Run Back Test with one Feed Pump has already failed causing drum level trip, operating engineer shall intervene judiciously depending upon the condition to save the unit from drum level tripping.

11. Mill change over: -

11.1. Planned change over, when 4 mills are in service:

Steps:

SH & RH Steam temperature control set point shall be gradually reduced to 520 0C and the temperature shall be allowed to settle steady.

If sufficient margin is available in the openings of SH/RH spray control valves, to contain the steam temperature rise during the 5th mill starting, Unit load need not be reduced. Otherwise Unit load shall be reduced by 10 MW during mill change over.

5th Mill shall be given START Sequence command.

After Mill feeders starting, 5th Mill shall be loaded gradually simultaneously unloading the Mill to be stopped with BIAS facility.

When the 5th Mill is stable, after ensuring local healthiness of this Mill & its Feeders, STOP Sequence command shall be given to the Mill to be stopped.

When the Unit load condition is stable, SH & RH Steam temperature control set point shall be gradually increased to their original value.

Points to be taken care of:

Load controller shall be kept in CMC mode all the time & load setting need not be further disturbed except in the case of wide variations in load.

GR fan currents should be monitored carefully during mill change over. (Restricted to 250 Amps)

Drum level should be monitored carefully.

11.2. When 4 mills are in service and 1 mill trips with reserve mill availability: -

Steps:

SH & RH Steam temperature control set point shall be reduced to 520 0C.

Reserve mill shall be started. Oil burners need not be cut except for flame instability.

New mill shall be loaded slowly with bias control.

When the mill is stable, the mill load shall be increased to normal value and allowed to settle.

Unit Load shall be increased to original value.

Trip analysis of the mill shall be carried out and corrective action shall be taken immediately.

11.3. Planned change over when 3 mills are in service: -

SH & RH Steam temperature control set point shall be gradually reduced to 520 0C and the temperature shall be allowed to settle steady.

4th Mill shall be given START Sequence command.

After Mill feeders starting, 4th Mill shall be loaded gradually simultaneously unloading the Mill to be stopped with BIAS facility.

When the 4th Mill is stable, after ensuring local healthiness of this Mill & its Feeders, STOP Sequence command shall be given to the Mill to be stopped.

When the Unit load condition is stable, SH & RH Steam temperature control set point shall be gradually increased to their original value.

Points to be taken care of:

Load controller shall be kept in CMC mode all the time & load setting need not to be reduced except in the case of wide variations in load.

GR fan currents should be monitored carefully during mill change over. (Restricted to 250 Amps)

Drum level should be monitored carefully.

12. When the bunker levels are low and reserve mill is available: -

During bunker level low condition, the mill O/L temperatures and bunker levels of all mills shall be selected in one video trend and observed continuously to find out which mill is fastly emptying. Accordingly bunker filling shall be carried out.

When the load controller is in CMC, nothing should be disturbed upto the automatic change over of turbine follow mode due to difference in thermal fuel flow and actual load.

In the turbine follow mode, When the load is < 180MW and if the bunker filling is not yet started, starting command to the reserve mill shall be given after reducing the SH, RH steam temperature control set point to 520(C.

When the reserve mill comes into service, it shall be loaded very gradually monitoring the load continuously.

If in any of the running mill the temperature is raising beyond 220(C, even with hot air & cold flue gas dampers in full open condition, the mill shall be stopped.

During bunker filling, unit load will shoot up fastly if turbine follow mode is in service and unit load shall be controlled with the Boiler Master and the bias control of the mill whose bunker is being filled. Monitoring of mill outlet temperature & its bunker level will give an indication of which mill is getting filled up.

When all the bunkers are filled and after normalization of all running mills, depending upon the mills configuration, one mill shall be stopped, if 5 mills are in service.

After stabilizing the unit load at around 200MW with 4 mills, the load control can be switched over to CMC mode and load shall be set to the initial required value.

When the Unit load condition is stable, SH & RH Steam temperature control set point shall be gradually increased to their original value.

13. When bunker levels are low and reserve mill is not available: -

During bunker level low condition, the mill O/L temperatures and bunker levels of all mills shall be selected in one video trend and observed continuously to find out which mill is fastly emptying. Accordingly bunker filling shall be carried out. When the load controller is in CMC, nothing should be disturbed upto the automatic change over of turbine follow mode due to difference in thermal fuel flow and actual load.

When load