WELCOME
ADANI POWER MAHARASHTRA LTD,TIRODA,
5 X 660 MW
TOPIC- STEAM BLOWING
By- Operation Team
INTRODUCTION
PURPOSE :
Steam
blowing
of
MS
lines,
CRH,HRH,SH,RH,HP & LP bypass pipe lines
of turbine is carried out in order to remove
welding slag, loose foreign materials, iron
pieces, rust etc. from the system, generated
during manufacturing, transportation &
erection.
EFFECT OF BLOWING DEPENDS ON
1)
2)
3)
Thermal shock
Removal force of steam
Cleaning force of steam
REMOVAL FORCE OF STEAM
Blowing Mass Flow ,
Q flow= √1.25 * Qmcr √(Vmcr /Vblow)
 Qmc= mass flow at MCR
 Vmc= velocity at MCR
 Vblow=blowing velocity
CLEANING FORCE OF STEAM
The necessity to create in the system, the steam
velocity greater than that is possible at MCR
condition is obvious. These two velocities are
expressed as a ratio “Cleaning factor” or “
Distribution factor” or “Cleaning Force Ratio”
denoted by “X” or “K”.
CLEANING FORCE REQUIRED (CFR)
OR DISTRIBUTION FACTOR
a)
K=Velocity of steam during blowing / Velocity of steam at MCR
b) K= (Steam flow during blowing)2 *(Sp.vol of steam at blowing
(Steam flow at MCR)² * ( Sp.vol of steam at MCR)
 Steam flow can be measured by the net feed water flow
 CFR & velocities of the steam should be verified to avoid “Over
Blowing”
 The recommended value K > 1.25 ( between 1.25 and 1.4)
PRECONDITIONS FOR STEAM LINE BLOWING
1) Chemical cleaning should be completed
2) SH primary and secondary de-superheater piping
3)
4)
5)
6)
7)
and RH’s emergency de-superheater piping ready
for operation
All permanent piping & temporary piping
insulated and supports/hangers are released with
cold setting
Silencer should be connected at temporary pipe
exit
Soot blowing for APH should be available
Make up for deaerator made ready
Motor Driven BFP with all controls made ready
PRECONDITIONS …
7) Hydraulic test of the following lines
completed:
 Feed Lines
 MS, HRH, CRH Lines
 MS to Aux. PRDS Line
 All other auxiliary lines identified for steam
blowing
8) Sampling system made ready
PRECONDITIONS …
9) Boiler auxiliaries proved serviceable and ready
after pilot operation like:
- Fuel oil system
- Compressors & Atomizing steam system
- Start-up system ( for continuous system)
- Coal Mill system (for continuous system)
- CHP readiness
- Economizer hopper and bottom ash hopper and
its evacuation system (for continuous system)
PRECONDITIONS …
10) All safety valve disc installed after removing
hydro-static plug in drum(sub-critical),
superheaters and reheaters
11) Adequate communication between control room,
boiler and TG area ensured.
12) Flow nozzle, control valves and NRV flaps
wherever applicable should be not erected before
steam blowing and suitable spool pieces are
erected. Strainers in the path should be removed.
13) Required number of Target Plates and holder
made available
CHEMICAL CLEANING PROCESS
 BOILER FRONT SYSTEM ALKALINE FLUSHING
 Mass Flushing
 Hot water Rinsing
 Alkaline Flushing
 Hot DM water Rinsing
 MAIN BOILER SYSTEM ACID CLEANIG
 Super Heater Filling
 Mass Flushing
 Alkaline Flushing
 Hot DM water Rinsing
 Acid Cleaning
 Passivation
CHEMICAL CLEANING …
 ACID CLEANING ( BY CITRIC ACID METHOD )will be done by
circulation method for effectiveness of the cleaning process.
 Acid cleaning will be followed by PASSIVATION, so that the uniform
protective coating of GAMMA FERRIC OXIDE is formed on the metal
surface and corrosion / oxidation damage to metal surface is prevented
and continue during normal operation by dosing oxygen. The gamma
ferric Oxide formed by using the chemical 1-2 % sodium
Nitrite(NaNO2)
BASIC TECHNIQUE USED
1) PUFFING METHOD
2) PURGING METHOD / CONTINEOUS BLOW
METHOD
PUFFING METHOD
 To give a thermal shock to the contour being purged,
to dislodge the scale etc.
 Procedure: Raise the boiler pressure to a predetermined value (40-60 kg/cm2), shut off firing and
at the same time open the quick opening valve(EOTV),
thus allowing the steam to escape to atm. with high
velocity carrying with it the loose debris.
PRECAUTION
 The Pressure drop
allowed in drum is
limited to corresponding
saturation temp. change
of 40 OC.
SCHEME
Steam blowing done in stages
 Stage-1(a)- SH, MSL, ESV, temporary lines from ESV
to EOTV, EOTV to CRH line, CRH lines upto boiler end
with temporary exhaust pipe.

Tap off lines from CRH to deaerator, auxiliary
PRDS, HP heater 6a & 6b, gland sealing, etc. shall be
remain closed/isolated.

stage 1a end point will be concluded by observing
the indents on the target plate.
STAGE- 1(a)
STAGE- 1(b)
 SH,MSL, HP bypass inter connection, hand
operated valve mounted in place of HP bypass valve
and CRH lines upto Boiler end with temporary
exhaust piping.
 In this stage 6 to 8 blows will be given through HP
bypass lines to ensure cleanliness of the limb.
 Boiler MS stop valve will be used for stage 1b. EOTV
will be kept closed. Manually Operated Isolation
Valves in HP bypass lines will be kept opened fully.
STAGE- 1(b)
STAGE-2(a)
 1a plus reheater, HRH lines , Interceptor Valve
and temporary pipe.
 CRH line along with attemperator shall be
welded with reheater before start of stage 2a. LP
bypass lines shall be blanked during stage 2a.
Stage 2a end point will be concluded by
observing the indents on target plates
STAGE- 2(a)
STAGE- 2(b)
 2a upto IV + LP bypass lines with temporary
exhaust pipe.

Stage 2b blowing will be parallel blow in the
path 2a & 2b. LP Bypass blanks shall be removed for
stage 2b. 4 blows will be given through L.P. Bypass
line to ensure cleanliness of the limbs
STAGE- 2(b)
STAGE-3
Auxiliary Steam Lines covered in steam blowing
are listed below.
3a) Main steam line to Aux PRDS
3b) CRH to Deaerator
3c) CRH to HPH-6.
All auxiliary steam lines will be steam blown by
continuous blowing method
STAGE-4
 The following Aux steam lines, connected to
deaerator are steam blown using auxiliary
steam from Aux PRDS header.
4a)PRDS to Deaerator.
4b)Extraction 4 to Deaerator.
4c) PRDS to Gland steam header.
CONTINEOUS BLOWING METHOD
 The initial procedure is same as puffing method
except:
- Continuous firing till the completion of steam
blowing. No need to shut of the firing during
blowing.
- Maintain constant pressure during the blow
Recommended blowing parameters
 Dynamic steam pressure
 MS temp
 HRH temp
 Steam flow
 Corresponding Drum pr.
 Furnace load
= 3.5 MPa
= 420(not to exceed)
= 480( not to exceed)
= 845 TPH
= 40 Ksc
≈ 39%
METHOD
- Set the Temporary purging valve, by-pass valve
and drain valve and granulating device behind
the temporary pipes
- Check the tightness, support and expansion of
the temporary system
- Section by section rinse of condensate water
piping, feed water piping and boiler through
the start-up system to CW system
METHOD:
- Circulation begins when Fe+ in the water of
main feed water pipe and separator outlet will
be less than 100 ppm.
- Maintain the circulation flow or start-up flow
at minimum set value
- Start oil firing and raise the temp and press.
according to the cold start-up.
Temp. rise rate of water wall = less than 2OC /
min
Temp. rise rate of main steam = 4 ~ 5 OC / min
METHOD:
- Before MS press reaches 1.0 Mpa , open the
bypass valve of temporary purging valve to
warm the piping with all water drain valves of
the system open.
-The blowing system divided into two parts
A) Preliminary Steam Blowing
B) Final Steam Blowing
METHOD
PRELIMINARY CLEANING
PORPOSEa)Primary cleaning out sundries and bulky grain
deposited in the RH and main steam system
b)To ensure fastness of supports and hangers with
proper expansion
c) Know well about the operation property of oil
burning system, condensate water and feed water
systems
PRELIMINARRY STEAM BLOWING
- Start the oil firing with max. rating of 15%
- Control the gas temperature at furnace outlet
below 500 OC (max.538 OC )
- Raise the SH outlet press to 1.6 – 1.8 Mpa with
steam temperature around 350 OC.
- Open the temporary purging valve for 15-20 min
to blow in MS system
- Maintain K around 0.5.
- SH & RH desuperheater water system also
cleaned
FINAL STEAM BLOWING
- Main steam and reheated steam system are purged
-
in series
Start 2-3 coal mills when oil burner hits the rated
firing rate of 15%
Increase the SH outlet press. to 3.5 Mpa.
Maintain the MS temp < 420 OC.
Keep HRH steam temp around 480 OC.
When the steam line blowing parameter reaches ,
open the temporary purging valve gradually and
increase the fuel and feed water volume to sustain
parameter stability.
FINAL ….
- Establish the MS flow around 40% of the MCR
-
(max.- 50%)
Ensure CFR (K) should be 1.25 to 1.3 for MS and 1.05
to 1.1 for reheated steam
Blow under this operating condition for 20 to 30
min
Gradually reduce coal firing and close the purge
valve at 0.5MPa .
Remove the target plate and check it
By estimation, target may satisfy the requirements
after 15 to 20 times in-series purging
- When the steam line temp is above the sat.
temp of MS press, close all drains and Open the
boiler MSSV fully.
- Maintain the press. through controlled firing
- Insert a reference target
- Check the CFR
- Allow to run for 30-60 min
TARGET PLATE

Generally Stainless steel panel
 Target plate set at the first, sixth, ninth, twelfth purging,
thereafter set target for each purging until purging results
qualified .
 Width about 8% of the steam vent tubes inner
diameter(ID) and length equal to ID
 Brinell hardness < 90
 Steam velocity – 258 m/sec
 Target plates to be introduced just before steam blowing
/ light up—to be removed soon after blowing is completed.
ONLINE TARGET PLATE CHANGE ARRANGEMENT
GLAND PACKING ARRANGEMENT
GLAND PACKING ARRANGEMENT
DEBRIS FILTER
AUX BOILER TO AUX STEAM HEADER
TDBFP INLET
BOILER
MS LINE
HPSV
TEMPORARY
PURGING VALVE
HPSV
HPBP
CRH LINE
TDBFP-1 SV
TDBFP-2 SV
TEMPORARY LINE
PERMANENT LINE
HP,CRH,REHEATER & HRH
HPSV1
BOILER
HPBP
HPSV2
CRH LINE
IPSV1
HRH LINE
IPSV2
TEMPORARAY LINE
PERMANENT LINE
HP BYPASS TO CRH NRV
HPSV1
BOILER
HPBP
HPSV2
CRH LINE
IPSV1
HRH LINE
IPSV2
TEMPORARAY LINE
PERMANENT LINE
LP BYPASS VALVE INLET
HPSV1
BOILER
HPBP
HPSV2
CRH LINE
HRH LINE
IPSV1
IPSV2
LPBP
TEMPORARAY LINE
PERMANENT LINE
STEAM BLOWING COMPLETION CRITARIA
 At least 2 continuous target plates should not have
ORIFICE GRANULARITY on the target shall be not
larger than 0.8 mm.
 CFR should be 1.25 to 1.4
 No. of orifice granularity shall not supass 08 nos.
ADVANTAGES
- Required less time for completion of the total process
- Less time required to normalize the system for final light-
up to synchronisation
- This reduces the reactionary forces on the temporary pipes
- Stresses on the boiler system are lower
Comparison between Puffing & Contineous Method
PUFFING METHOD
 More time required for complete
CONTINEOUS METHOD
 Less time required for
steam blowing due to stage wise
blowing(8-10 days)
 More time required for stage wise
temporary pipe erection and
shifting of blowing device
 Less time required as only
 No mill required
 Minimum 02 nos. of mill
 Quality of cleanliness is better
required
 Quality of cleanliness is
slightly less than Puffing.
than continuous process
completion (3-4 days)
valves to be opened for
different systems
Comparison …
PUFFING METHOD
CONTINEOUS METHOD
 Thermal shock is the driving
 Steam velocity or Removal
force of cleaning
 More thermal stress on tube
material and sudden loading
on supports
 Repeated light-up and
shutdown
force is the driving force
 Less thermal stress on tube
material
 There is a time gap between
the blows to make-up DM
water
 System normalization time
after steam blowing is more
 Silencer use is optional
 Light-up only once in the
beginning of the steam
blowing
 DM water make-up to the
system during steam blowing
is a challenge
 System normalization time
after steam blowing is less.
 Silencer use is compulsory.