steam blowing procedure

1

TROMBAY

TROMBAY

UNIT 8

Steam Blowing

Viren A. Joshi

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.

3

TROMBAY

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.

4

TROMBAY


• 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.

5

TROMBAY


• In addition to this, for stages 1, 2a, & 3a Disturbance factor value at selected locations should be greater than unity.

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.

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.

8

TROMBAY

EOTV

ESV

EOTV

ESV

DRUM• Stage1a: SH, MSL, ESV, temporary line from ESV to EOTV (Electrically operated temporary valve) and EOTV to exhaust.

• Stage1b:SH, MSL, Aux PRDS, Atomising Steam lines & FO heating/tracing lines continuous blowing.

TP

BLANK

PRDS

MS Line

MS Strainer

9

TROMBAY

EOTV

ESV

EOTV

ESV

DRUM

BLANK

PRDS

MS Line

RH INLET

PRS

HPH 6 HPBPHOTV

BLANK

CRH Line

TP

• 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.

10

TROMBAY

• 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.

11

EOTV

ESV

EOTV

ESV

DRUM

BLANK

PRDS

MS Line

RH INLET

CRH Line

EOTV

ESV ESV

RH OUTLET

EOTV

LPBP LPBP

REHEATER

TP

BLANK

HRH Line

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

13

TROMBAY

THANK YOU

steam blowing procedure

Technology