Boiler purge is the basic process of resetting boiler before lightup. This presentation explains the logic, schematics & working of purge procedure. For enhanced knowledge of this topic, I can be reached at tahoorkhn03@gmail.com.

1. BOILER PURGE & ITS
SIGNIFICANCE

2. Why Boiler PURGE is
required?
 ‘PURGE’ as the name implies, is nothing
but the cleaning of system before taking it
into operation.
 PURGING can be understood as
SCAVANGING of any system.
 With PURGING, we clear off any residual
unburt fuel (coal, oil etc.) so as to avoid
furnace explosion due to sudden burning of
large amount of fuel at the time of Lightup.

3. SIGNIFICANCE OF
PURGING
 PURGING is the main PERMISSIVE
for Boiler Lightup.
 Boiler PURGING time is 5mins, which
ensures proper removal of any
unburnt fuel particles to be transported
outside boiler furnace.

4. BOILER
FURNACE
FD AIR
(Clean air from
atm)
IN
OUT
ID FAN
(Air + Unburnt Fuel)Air + Unburnt
Fuel
BOILER PURGE

5. BOILER PURGE
PERMISSIVES
 NO Boiler Trip Condition Persisting
 NO Fuel Supply Equipment should be
running.
 NO Flame sensed by Flame
Scanners.
 Air Flow should be >30% and <40%.

6. There should not persist any of the
following conditions:
 ALL ID FANS OFF
 ALL FD FANS OFF
 DRUM LEVEL VERY HIGHVOR VERY
LOW
 AIR FLOW <30%.
 FURNACE PR VERY HIGH OR VERY
LOW
BOILER PURGE PERMISSIVES contd…
1. NO Boiler Trip (MFT) Condition Persisting
(NOTE: For more details kindly refer to another tutorial on MFT)

7.  ALL HOTV & HONV CLOSE
 ALL LOTV & LONV CLOSE.
 ALL PA Fans OFF.
 ALL Coal Feeders OFF.
 ALL Mill Hot Air Gates CLOSE.
BOILER PURGE PERMISSIVES contd…
2. NO Fuel Supply Equipment Running
HOTV: Heavy Oil Trip Valve (Single Valve in HFO main supply Line.)
HONV: Heavy Oil Nozzle Valve (Valve provided at every corner before oil
guns.)
LOTV: Light Oil Trip Valve (Single Valve in LDO main supply Line.)
LONV: Light Oil Nozzle Valve (Valve provided at every corner before oil
guns.)

8. BOILER PURGE PERMISSIVES contd…
3. No Flame Sensed by Flame Scanner
1
2
4
3
AB
1
2
4
3
BC
1
2
4
3
CD
1
2
4
3
DE
1
2
4
3
EF
Flame
Scanners
at every
Elevation

9. This permissive ensures adequate air
flow inside boiler furnace that is
required to transfer unburnt fuel to
stack.
BOILER PURGE PERMISSIVES contd…
4. Total Air Flow >30% and <40%

10. LOGIC OF BOILER PURGE
No boiler trip
HOTV close
LOTV close
ALL HONV close
Air <30% &
>40%
ALL Scanners show no
flame
ALL HAG Close
ALL LONV close
ALL Feeders
OFF
ALL PA Fans
OFF
ALL Aux Damper
Modulating
PURGE
START

11. BEFORE PURGING
MFT TRUE
AFTER PURGING
MFT RESET
 Boiler cannot be lighted up.
 No Boiler Protection in service.
 Boiler can be lighted up.
 ALL Boiler Protections in service.

12. THANK YOU
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