2. Steam Blowing(Final)

8/10/2019 2. Steam Blowing(Final)

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OVERVIEW OF BOILER

COMM ISSIONING

By: Dhruv Garg

Engineer/ Boiler/ PS-TS


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B ILER MMI I NINSEQUENCE

Hydraulic Test (drainable and Non-drainable portions ofpressure parts)

Trial Run of Equipments(Fans PA, FD, ID, Scanner, SealAir & Air heaters)

Gates and Damper Commissioning

Air and Gas Tightness Test (Furnace, 2nd pass, ESP andFan Ducts)

Fuel Oil System Readiness(LDO / HFO Pumps, SteamBlowing and Oil Flushing of oil lines)

Control and Isolation Valves (Motorized, Pneumatic) Secondary Air Damper Control (SADC) Commissioning


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BOILER COMMISSIONING SEQUENCE

Preparation for First Boiler Light Up

v FSSS (furnace safeguard supervisory system) commissioningv Checks on oil guns, igniter system, equipments in oil/ airlines, furnace probe and thermocouples

Alkali Flushing and EDTA Cleaning (Pre-operative chemical

cleaning) Steam Blowing (MS, CRH and HRH)

HP & LP Bypass Commissioning

Safety Valve Floating

Steam Dumping

Mills Commissioning

Soot Blowers (Wall blowers, Long retractable soot blower(LRSB),Air heater soot blowers)


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STEAM

BLOW INGOF BOI L ER

P I P I NGS


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q In spite of maintaining higher standards of boiler

erection cleanliness and doing a pre-operationalchemical cleaning of the circulation system. certainquantity of debris in the form of scales, loosematerials, weld spatter, etc. will remain in the boilerand the pipe lines especially in the Superheater,Reheater sections, Main steam line, Cold and HotReheat Lines.

q Subsequent steam blowing completes the task ofproviding a cleaner system for passing steam into theturbine. In other words we attain steam of requiredquality standard by way of chemical cleaning andsteam blowing.

q Failure to remove debris may result in increasedturbine erosion, blade damage and rapiddeterioration of turbine efficiency.

WHY STEAM BLOWING ?


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TYPES OF STEAM BLOWING

Puffing Method:The system (surface) to be clean is first pressurized by steamupto certain pressure and then releasing of this pressuresuddenly caused the cleaning of system internal surfaces due

to high kinetic velocity attained by steam.

Continuous Blowing method:The surface to be clean is continuously blown by

superheated steam for 20-30 min at 12 kg/ cm2

& 300-350Deg C.


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LINE SIZES (FOR 500 MW TYPICAL)

( d x t) mm 1. SH Outlet Pipes : 406 x 42

2. MSL : 564 x 57

3. CRH : 864 x 35

4. CRH to Re-heater inlet : 620 x 20

5. RH to HRH : 750 X 45 6. HRH : 969 X 60

7. HP BP line : 334 X 35

8. LP BP line : 720 X 45


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LPBP VALVES

IV

IV

ESV

ESV

EOTVHOTV

HRH

MSL

BOILER END CRH

LINE

BOILER END CRH LINE

457x14.2

457

457

323.9

1ST STAGE

2ND STAGE

3RD STAGE

STEAM BLOWING SCHEME FOR

250 MW PIPING

HP BYPASS

508

219.1

273

457

323.9

711.2x 25

MSL

HRH

HOTV


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IST STAGE CIRCUIT DESCRIPTION

Stage-1a

Superheater, Main steam Line (includes MS strainerportion), Temporary line from Emergency Stop Valve(ESV) to Electrically Operated Travelling Valve(EOTV)& EOTV to CRH NRV and CRH lines upto boiler endwith temporary exhaust piping.

1a end point will be concluded by seeing target plate.


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FIRST STAGE CIRCUIT DESCRIPTION (

CONTD..)

Stage-1b

Stage 1a plus HP bypass inter connection by openinghand operated valve mounted in place of HP bypassvalve.

1a &1b will be combination blowing and would result ineffective blowing of CRH Line.

However. approx 6 to 8 blows will be given only throughHP bypass to ensure cleanliness of the limb.


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STEAM BLOWING PROCEDURE The boiler is to be lighted up in a normal manner,

following start up procedure from Boiler O&M manual.

Boiler drum pressure raised to 40 50Kg/ sq.cm.

Water level in the drum kept at the lowest port (visiblelimit) before the start of each steam blow off.

Light off the Boiler and at the same time, open theEOTV ( Pressure release takes place) & close thisEOTV at 20-25 Kg/ sq. cm drum pressure.

Limit number of blows per day to 8 with an interval of1-1 hours for cooling in addition to overnightcooling. ( Starting time at 0600 hrs and End time is1000hrs)


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COMPLETION CRITERION FOR STEAMBLOWING

The result of the blowing operations can be judged by the

absolute number of pittings on the target plate in thecentral zone. The piping is considered clean if there arenot more than 5 (five) pittings and shall not have anydeformed edges. Besides this, there shall be no pitting inthe rim zone.

Initial Targets plates used can be of M ild Steel Materialbut finished Stainless Steel T.P must be used for finalcompletion.

Also, If Disturbance Factor(DF) is calculated for thesteam blowing of any circuit, then its value must be

greater than 1.(D.F is the ratio of the steam flow during steam blowingoperation to the Steam flow at MCR.)


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STEAM BLOWING DATA FORVARIOUS PROJECT SITES

S.No Site Stage No. of Blows Remarks

1 Unchahar U # 5, 210MW (NTPC)

1 40 MSL

2 13+8 CRH + HPBP

3 24+6 HRH + LPBP

2 Parichha U # 3, 250

MW (UPRVUNL)

1 18+4 MSL &CRH + HPBP

2 18+4 HRH + LPBP

3 Parichha U# 4, 250MW

1 24+3 MSL & CRH + HPBP

2 24+2 HRH + LPBP

4 Vindhyachal U# 9, 500

MW (NTPC)

1 47 MSL

2 15+9 CRH + HPBP

3 27+9 HRH + LPBP

For NTPC projects- Steam Blowing carried out in 3 stages

For other projects- steam blowing carried out in 2 stages. (stage 1&2 combined)


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ST EAM BL OWI N G FOR

FUEL O I L L I N E S

(CONT I N UOUS BL OWI N G

ME THOD )


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OBJECTIVE

To remove debris, scales and weld splatters and cleanthe internal surface of oil lines in the LDO / HFOsystem including atomizing steam lines and steam

tracing lines.


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PLANT DETAILS:

The Fuel oil plant consists of facilities for Unloading,Storage and Supply of LDO and HFO.

Fuel Oil Pump House is located close to Fuel Storage Yard.

The Pump house houses:

LDO and HFO Pumps for Main Boiler

HFO Heaters

HFO cooler in the return line

Drain Oil Tank & Drain Pump

Electrical & control Panels for FO Pump House auxiliaries


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(CONTD..)

Blowing of LDO lines, Steam tracing lines and condensate

lines is done at 6 Kg/ cm2 for 20-30 minute each.

Drains / vents of FO lines are kept open as required duringsteam blowing and thereafter for draining of condensate.

After sufficient cooling, the piping are dried withcompressed air.

After completion of steam blowing, all spool pieces areremoved and Trip valves, control valves, flow elements,filter elements and NRV internals are restored /

normalized. Pipe connections to LDO / HFO pumps arenormalized and pumps are commissioned.


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COMPLETION CRITERION FORCONTINUOUS STEAM BLOWING

Steam blowing of the section of LDO / HFO lines isdeclared complete after minimum five blows eachhaving a blow duration of 20-30 minutes.

Blowing medium at exit of the pipe should be visuallyclean.


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T H AN KYOU

2. Steam Blowing(Final)

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