Steam blowing is carried out to remove welding slag, debris, and other foreign materials from turbine system piping generated during manufacturing and construction. It uses high velocity steam to purge lines through either puffing method, which uses thermal shocks, or continuous blowing method. The process is done in stages, with target plates used to evaluate cleanliness. The lines blown include steam, reheat, bypass, and other auxiliary lines. Blowing is completed when target plates show acceptable levels of debris indentation.

1. STEAM BLOWING

2. OBJECTIVE
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.
PRINCIPLE OF STEAM BLOWING
To ensure that sufficient cleaning forces are applied to the piping, the
steam momentum during the steam blow must be equal to or greater than
the steam momentum at normal maximum load condition. The Cleaning
Force Ratio (CFR) is typically used to evaluate if satisfactory blow
conditions are obtained.

3. PRECONDITIONS FOR STEAM LINE BLOWING
1) Chemical cleaning should be completed
2) SH primary and secondary de-superheater piping and
RH’s emergency de-superheater piping ready for
operation
3) All permanent piping & temporary piping insulated
and supports/hangers are released with cold setting
4) Silencer should be connected at temporary pipe exit
5) Soot blowing for APH should be available
6) Make up for deaerator made ready
7) Motor Driven BFP with all controls made ready

4. 8) 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
9) Sampling system made ready
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.

5. 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

6. BASIC TECHNIQUE USED
1) PUFFING METHOD
2) PURGING METHOD / CONTINEOUS BLOW
METHOD

7. PUFFING METHOD

 To give a thermal shock to the contour being purged, to
dislodge the scale etc.
 Procedure: Raise the boiler pressure to a pre-determined 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.

8. CONTINEOUS BLOWING METHOD

The initial procedure is same as puffing
method except shutting off the firing during
blowing.
Continuous firing till the completion of steam
blowing.
Maintain constant pressure during the blow

9. STAGES
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.
• stage 1a end point will be concluded by
observing the indents on the target plate.

10. STAGE- 1(a)

11. 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.
 EOTV will be kept closed. Manually Operated
Isolation Valves in HP bypass lines will be kept
opened fully.

12. STAGE- 1(b)

13. 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

14. STAGE- 2(a)

15. 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

16. STAGE- 2(b)

17. 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.

18. STEAM BLOWING COMPLETION CRITERIA
• At least 2 continuous target plates should not have
ORIFICE GRANULARITY on the target shall be not larger
than 0.8 mm
• No impacts with a diameter larger than 1 mm.
• Not more than 4 impacts with a diameter larger than 0.5
mm.
• Not more than 10 impacts with a diameter of 0.2 to 0.5 mm
.

23. Martyr V/v
Martyr V/v
CRH Line
Final SH Final SH
ESV
ESV
HP Bypass
MS Line
CRH NRV CRH Drain
Pot
RH O/L Hdr
HRH Line
MSV
MSV
LP Bypass
IP SV
Open Close Martyr Valve
Steam Blow Line
Temporary Line
Pre Step # 1 : MS Line Steam Blowing
LPBP V/ v

24. Final SH Final SH
Martyr V/v
ESV
Martyr V/v
ESV
HP Bypass
MS Line
CRH NRV CRH Drain
CRH Line
Pot
RH O/L Hdr
HRH Line
MSV
MSV
LP Bypass
IP SV
Open Close Martyr Valve
Steam Blow Line
Temporary Line
Pre Step # 2 : HPBP / CRH Line Steam Blowing

25. Final SH Final SH
Martyr V/v
ESV
Martyr V/v
ESV
HP Bypass
MS Line
CRH NRV CRH Drain
CRH Line
Pot
RH O/L Hdr
HRH Line
MSV
MSV
LP Bypass
IP SV
Open Close Martyr Valve
Steam Blow Line
Temporary Line
Main Step # 1 : HRH Line Steam Blowing

26. Final SH Final SH
Martyr V/v
ESV
Martyr V/v
ESV
HP Bypass
MS Line
CRH NRV CRH Drain
CRH Line
Pot
RH O/L Hdr
HRH Line
MSV
MSV
LP Bypass
IP SV
Open Close Martyr Valve
Steam Blow Line
Temporary Line
Main Step # 2 :LPBP Line Steam Blowing