WARM START UP
DETAILS:
WARM START UP – HP Shaft Temp > 250 deg C & < 350 deg C
HOT START UP – HP Shaft Temp > 350 deg C
PROCEDURE DETAILS
STATE OF PLANT
All the pre-requisites for boiler cold start-up met.
At least one PA fan and one seal air fan available.
Coal mills and corresponding feeders are available.
Super heater and re heater spray system in lined up condition.
Open S/H Header drains to IBD for about 1 to 2 minutes to allow any condensate
water in S/H Header and limbs to get drained.
If vacuum is not pulled in the condenser, open R/H vents, these are to be closed before
pulling vacuum.
Ensure Economiser recirculation valve (E-23) is in open condition.
Cooling Water System (CW, ACW & DMCW System) is put in service.
BOILER LIGHT-UP & STEAM PARAMETER BUILD UP
All the steps of boiler cold start-up will also be applicable here except the following:
S/H manual air vents & S/H header drains are no more to be closed as they are
already in closed condition because of adequate pressure in drum.
Light-up the Boiler as per the procedure with LDO in one elevation.
Main steam line charging and HP-LP bypass charging has to be done at the
prevailing drum pressure.
Since boiler will be hot, take second elevation oil guns into service.
Line-up one PA fan and one seal air fan. Start the selected PA fan. See that the seal air
fan starts in auto.
Start the first coal mill.
When boiler load and operating conditions are satisfactory, the second, third coal
mill should be made ready for starting. Ensure that all mill starting requirements
have been checked.
When the f i r s t mill is proven in service, the fuel air damper should open
automatically adjust to maintain good combustion.
Check that associated fire ball scanner sense “FLAME”.
Ensuring that HP-LP bypass are in service.
Visually check flame if considered necessary through local peep holes in the furnace.
Note: FSSS “FLAME FAILURE” tripping logic gets armed now and boiler may trip if
actual flame or its sensing by fireball scanners is poor and three out of four oil guns are
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WARM START UP
not proven in the associated oil elevation.
Mill air flow and temperature control can be put on auto to maintain the required
air flow and mill outlet temperature of 80°C. If flame condition is good then only one
corresponding elevation oil guns can be kept in service.
Note: Mill start-up will cause a sharp and sudden increase of steam pressure & temp.
This should be controlled by increasing HP-LP bypass opening.
The firing rate of oil burners and coal mills should be controlled depending on turbine
rolling requirements and at a rate as per the start-up curve.
If required, two consecutive mills can be put into service for faster rise of steam
temperature not exceeding the rate of Boiler temp rise.
SH and RH temperature is to be controlled by operating burner tilt. SH and RH spray
should be used only if burner tilt is not able to control the temperature.
When feed water flow to the boiler reaches the capacity of the 30% line, then 100%
feed line should be taken in service. When feed flow is continuous, drum level
controller can be put in “Auto”.
If boiler steam flow increases beyond 30% of full load, total air flow should be increased
accordingly. Check for flue gas O₂ reading. It should be as per the graph supplied by the
manufacture.
Also when BLI (Boiler Load Index) is >30%, see that SADC aux. air dampers close
adjacent to non-running mills and wind box to furnace differential set point
follows the set curve if on AUTO.
During the process of boiler parameter build-up metal temperatures should be
watched. It should not cross its maximum limit.
After synchronization, more nos. of mills can be taken into service. Additional mill
should be taken into service when running mill reaches 80% of its rated capacity.
Line-up and start second PA fan (after third mill).
Place both PA fans on auto control.
As each mill is placed in service, the required associated ignition energy must be
available when unit firing conditions are stabilized; all warm-up oil guns may be with
drawn from service after four mills are proved at 50% of rated capacity.
When RH steam temperature is close to the normal operating level of 540°C, the
controls should be placed on AUTO.
When super heater steam temperature is close to the normal operating level of 540°C,
the control should be placed on AUTO.
During boiler loading period, maintain a close check on all the boiler operating
conditions. Ensure that design limitations are not exceeded in any case.
CBD opening can be controlled as per the instruction of chemist and drum
pressure to be strictly maintained as per the chemist on the basis of silica.
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WARM START UP
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