Boiler force Cooling
Boiler force Cooling :
In case of tube leakage:
After Tripping the boiler ,stop FD fan and keep ID fan running at minimum load and ensure furnace pressure negative inside boiler.
Reduce pressure as per boiler cooling curve Annex-1 by opening startup vent /HP/LP bypass and maintain drum level by feed water supply. (During pressure reduction maintain Drum Top/Bottom DT below 50 Deg C )
After two hour of Boiler tripping start FD fan and reduce pressure as per boiler cooling curve ( Annex-1) . Limit Drum Top/Bottom DT below 50 Deg C. during depressurisation.
Open SH drain at 10 KSC and open SH Vents at 4 Ksc.
Open Drum Vents at 2 KSc.
Drain boiler when boiler water temperature is below 94 Degree C
Keep ID & FD fans running till temperature inside boiler becomes comfortable for maintenance personnel to go inside boiler and attend the tube leakage.
Other Than Tube leakage :
In case of tube leakage:
- Operate Wall Blower and LRSB during Load reduction
- Gradually reduce load and allow pressure drop to accelerate cooling & steam temperature drop as per Turbine manufacturer recommendation
- Trip the Boiler
- After Tripping the boiler ,stop FD fan and keep ID fan running at minimum load and ensure furnace pressure negative inside boiler.
- Reduce pressure as per boiler cooling curve Annex-1 by opening startup vent /HP/LP bypass and maintain drum level by feed water supply. (During pressure reduction maintain Drum Top/Bottom DT below 50 Deg C )
- After two hour of Boiler tripping start FD fan and reduce pressure as per boiler cooling curve ( Annex-1) . Limit Drum Top/Bottom DT below 50 Deg C. during depressurisation.
- Open SH drain at 10 KSC and open SH Vents at 4 Ksc.
- Open Drum Vents at 2 KSc.
- Drain boiler when boiler water temperature is below 94 Degree C
- Keep ID & FD fans running till temperature inside boiler becomes comfortable for maintenance personnel to go inside boiler and attend the tube leakage.
- Feed water filling and draining should not be done for accelerating cooling.
- In case of tube leakage in Pent house area ,exhaust fan to be put into service.
- Water washing in water wall area should be done only after draining of boiler.
- Water washing inside the boiler should be done only after tube metal temperature in the location where water washing intended falls below 94 deg C in that location.
- Water washing in the penthouse should be done only after header metal temperature in the location where water washing is intended ,falls below 94 deg C in that location.
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