Steam blowing is carried out to remove debris from superheaters and reheaters that accumulate during manufacturing and installation. The objective is to prevent damage to turbine blades and valves. Steam blowing is considered complete when target plates show less than 5 indentations in the central zone or meet alternative criteria of indentation sizes. The procedure uses puffing and continuous blowing methods applying thermal shock to dislodge scale, which is removed by expanding steam. Various stages are outlined blowing different sections of piping and components. Completion is determined by observing target plate indentations.

1. TROMBAY
TROMBAY
UNIT 8
Steam Blowing
Viren A. Joshi
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2. TROMBAY
ACTIVITIES BLOWING PURPOSE
•
The objective of steam blowing is to remove
scales, loose material, iron cuttings etc, which are
entrapped in Super Heaters, reheaters during
manufacture, storage, erection at site.
•
Failure to remove the debris may result in damage
to turbine blades, Valves etc.
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STEAM BLOWING COMPLETION CRITEIRA
•
For stages 1, 2a, 3a, 4a & 4b the the blowing
operations is considered to be completed if the
absolute number of pitting on the target plate in
the central zone are less than 5.
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4. TROMBAY
STEAM BLOWING COMPLETION CRITEIRA
•
Alternatively following guide lines may be followed
a) No impact marks greater than 1mm.
•
b) No more than one indentation of 0.5mm in one
square inch area.
•
c) All markings under 0.5 mm shall be ignored.
•
d) There must be a minimum of 10 blows for each path
to be cleaned.
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5. TROMBAY
STEAM BLOWING COMPLETION CRITEIRA
•
In addition to this, for stages 1, 2a, & 3a
Disturbance factor value at selected locations
should be greater than unity.
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6. TROMBAY
ACTIVITIES PROCEDURE ADOPTED
•
Steam blowing is carried out by adopting puffing
method for stages 1a, 2a, 2b,3a & 3b in which,
boiler pressure is raised to 40KG/CM2 and
released through a quick opening valve and steam
blowing done till the Drum pressure drops from
40KG/CM2 to 20 KG/CM2.
•
Steam blowing for stages 1b & 4 are carried out by
continuous method at pr. 40 to 50 % of the rated
pr. for the respective system.
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7. TROMBAY
PROCEDURE ADOPTED
•
Both the above techniques give a thermal shock to
the contours being purged and results in
loosening of the adhered scale, which is
subsequently removed by expanding steam.
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8. TROMBAY
•
•
Stage1a: SH, MSL, ESV, temporary line from
ESV to EOTV (Electrically operated temporary
valve) and EOTV to exhaust.
DRUM
MS Line
PRDS
Stage1b:SH, MSL, Aux PRDS, Atomising
Steam lines & FO heating/tracing lines
continuous blowing.
MS
Strainer
ESV
ESV
EOTV
EOTV
BLANK
TP
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9. TROMBAY
•
•
Stage – 2a : SH, MSL, ESV,
temporary lines from ESV to EOTV,
EOTV to CRH line, CRH lines up to
boiler end.
Stage – 2b : HP bypass inter
connection, HOTV (hand operated
Temporary valve) mounted in place
of HP bypass valve and CRH lines
up to Boiler end.
DRUM
RH
INLET
MS Line
PRDS
TP
HPH 6
CRH Line
ESV
ESV
PRS
HOTV
HPBP
EOTV
EOTV
BLANK
BLANK
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10. TROMBAY
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Stage – 3a : SH, MSL, ESV, temporary lines from ESV to EOTV,
EOTV to CRH line, CRH lines up to reheater, HRH, IPCV and
temporary pipe.
Stage 3a end point will be concluded by observing the indents on
target plates.
•
Stage-3b: SH, MSL, ESV, temporary lines from ESV to EOTV, EOTV
to CRH line, CRH lines up to reheater, HRH plus LP Bypass lines.
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11. RH
OUTLET
DRUM
REHEATER
MS Line
RH
INLET
HRH Line
ESV
PRDS
LPBP
ESV
ESV
ESV
LPBP
EOTV
EOTV
EOTV
EOTV
CRH Line
BLANK
TP
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BLANK

12. TROMBAY
Stage-4 :
4a) APRDS to Gland seal steam
4b) CRH to turbine extraction line (HPH 6).
4c) CRH to Deaerator and FST
4f) CRH steam line to Turbine gland sealing line
4g) CRH to APRDS
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13. TROMBAY
THANK YOU
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