Chemical Cleaning

TITLE PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANING ( FOR RAMAGUNDAM 1X500 MW UNITS)

DOC. NO. COS-COMM-R-Commg.PRO/006BHEL DOC. Ref No. PS-DC- 202-500-0002

REV. NO.: 0

DATE OF ISSUE 19 . 12 . 2003

RECORD OF APPROVALS & REVISIONS

REVISION 0 2 3DATE 19.12.2003DETAILS OF REVISIONREVIEWED BY

SIGNATURENAMEDESIGNATION

B. ADHIKARYSr. Mgr (OS)

CHECKED BY



S. K. GUPTA DGM (OS-CHEM)

C.P. MALIKDGM(OS-COMM)

APPROVED BY


K.K. SHARMAAGM (OS)

NATIONAL THERMAL POWER CORPORATIONOPERATION SERVICES DIV.

Engineering Office Complex, Plot no. A-8A, Sector-24, NOIDA-201 301; Ph. 0120-2410333 / 2410116 / 2410140-144

APPROVAL FOR DOCUMENTS

NATIONAL THERMAL POWER CORPORATIONOPERATION SERVICES

ENGINEERING OFFICE COMPLEXA-8A, SEC-24, NOIDA, U.P.:201 301

PH:0120-2410333, 0120-2410133 / 2410116FAX.:020-2410136/937, 2410350/2410357

TRANSMITTAL FOR DOCUMENTS

FROM: DGM (OS-Commg)

REF. : COS-COMM-R-Commg-PRO/006/

DATE: 22.12.2003

TO:1. Sh. K. P. T. MURUGAN, DGM (TSX),

BHEL-PS-SR OFFICE, 474, ANNA SALAI, NANDANAMCHENNAI-600 035

2.AGM (O & M), NTPC-(RAMAGUNDAM)

3. Sr. Mgr. (OS-Commg)

SUB.: PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANING (RAMAGUNDAM St-III: 1X500 MW UNIT)

Please find enclosed following drawing / documents for necessary action at your end as indicated in the

purpose code.

Sl. No.

Document no. Rev. no.

Document Title No. of copies

Purpose Code

Remark

1 COS-COMM-R-Commg-PRO/006BHEL Ref. No. :PS-DC-202-500-0002

0 PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANING (RAMAGUNDAM St-III: 1X500 MW UNIT)

1 1

Transmittal Purpose Code1. For Implementation.2. For your review and comments.3. For your information.4 Others …..(Specify in remarks column).

NOTE: 1. All previous revisions if any may please be destroyed/marked “superseded”, at your end.

(C.P. MALIK)DGM (OS-COMMG)

OS-Q-ISO-P-002/F2-R1 OPERATION SERVICES

Station: NTPC- Ramagundam

BHEL Ref No. PS-DC-202-500-0002 NTPC Ref no COS-COMM-R-Commg-PRO/006

Sheet 4 of 38

Plant area: BOILERPROCEDURE FOR BOILER ALAKALI BOIL OUT AND ACID CLEANING

SLNO

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

LIST OF CONTENTS

PLANT DETAILS

OBJECTIVES

PROPOSALS

SERVICES REQUIRED

SAFETY PRECAUTIONS

EMERGENCY PROCEDURES

STATE OF THE PLANT

METHOD

COMPLETION CRITERIA

APPENDICES

a) DRAWING

b) LOG SHEETS.

STATUS

Signatures

NTPC BHEL



Sheet 5 of 38

Plant area: BOILERPROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANING

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1.0

2.0

2.1

3.0

3.1

3.2

3.3

PLANT DETAIL

The steam Generator is a controlled circulation plus Radiant Reheat (Type CC+RR) boiler. Firing equipment consists of five elevations of remotely controllable high energy arc igniters, five elevations of air cooled, non-retractable steam atomizing oil guns and nine elevations of pulverized coal nozzles. The nine elevations of pulverized coal nozzles are supplied with coal from nine numbers of type XRP 1003 Bowl mills, which form the load carrying fuel for the boiler.

Control equipment provided consists of furnace safeguard supervisory system, scanner air control system and a secondary air control system.

Major auxiliary equipment provided consists of pulverizers, feeders, fans and miscellaneous valves. Three number of boiler circulating pumps are provided to ensure proper circulation of water in the furnace water wall circuits.

OBJECTIVE

The objective of this procedure is to clean the internal surface of the steam generating portion and heating surface (Economizer) using specified chemicals.

PROPOSAL

By carrying out an effective alkali boil-out grease and any other protective coatings applied on the inner surfaces of pressure parts are removed.

Then, it is subjected to acid cleaning for the removal of patchy mill scale and rust.

Finally, the acid pickled surface is passivated for the formation of uniform and coherent magnetite layer.

STATUS

Signatures

NTPC BHELStation: NTPC- Ramagundam


Sheet 6 of 38

Plant area: BOILERPROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANING

SLNO4.0

4.1

4.2

1.

2.

3.

4.

5.

SERVICES REQUIRED.

Prior to the commencement of chemical cleaning, all the de-mineralized water storage tanks should be kept full and the de-mineralizing units are kept in regenerated condition. Approximately, 6000 m3 of de-mineralized water will be consumed for the entire process. At any point of time of acid cleaning, a minimum of two boiler volumes (approx. 1400 m3) of de-mineralized water should be available in ready stock to facilitate rapid flushing of the system in the event of chemistry upset.

All the required quantities of chemicals, as given below, should be made available prior to the commencement of the chemical cleaning process.

SPECIFICATION AND QUANTITIES OF CHEMICALS

NAME OF CHEMICALS QTY/Each Boiler

Na2

HPO4 ,12 H2O DISODIUM HYDROGEN

PHOSPHATE 800 Kg. 1S 566 – 1991

Na3 PO

4 12 H

2O TRISODIUM PHOSPHATE 1500 Kg.

IS:573:1992

HYDROCHLORIC ACID: 30% MIN 70 Tones. IS:265:1993

RHODINE: 213 SPECIAL 800 Ltrs.(PREFFERED INHIBITOR)(Proprietary item Mfd. by M/s Agromore, Bangalore)

ORIncase Rhodine 213 Special is not available,

CORONIL: 213 SPECIAL 1200 Ltrs.(Proprietary item, Mfd. By M/s Arudra Engineers Pvt. Ltd., Chennai)

CITRIC ACID 800 Kgs. IS:5464:1995

STATUS

Signatures

NTPC BHEL



Sheet 7 of 38

Plant area: BOILER

PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANINGSLNO

6.

7.

8.

9.

10.

11.

12.

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

AMMONIA: 25% 1000 Ltrs. IS: 799-1990

HYDRAZINE HYDRATE: 80% 1000 Ltrs IS:12086 – 1992

NITROGEN CYLINDERS: 6.2 Nm3 each 500 Nos.IS:1747:1991 OR

(NITROGEN FROM CRYOGENIC TANKER)AMMONIUM BIFLUORIDE; 97% 1000 kg.

IS:13119 – 1991

HYDRATED LIME: Grade – A 05 Tonnes.IS:1540:1990 (Part – II)

BLEACHING POWDER: Grade – I 05 Tonnes.IS:1065 – 1989

CAUSTIC SODA LYE (50%) 70 Tonnes.

Availability of following is to be ensured prior to the commencement of the chemical cleaning process.

Temporary polythene ‘U’ tube for drum level indication during acid pickling.

11 KV, 6.6 KV & 415V electrical power supplies.

Control supplies.

Instrument air & Service Air .

Chemist / Express lab .

Auxiliary steam (Approx: 15 TPH at 12 kg/cm2 & 250 deg C.

Boiler fill pumps.

Flood lights / telephones / walkie-talkie sets .

STATUS

Signatures

NTPC BHEL



Sheet 8 of 38

Plant area: BOILER

PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANINGSLNO4.11

4.12

4.13

4.14

4.15

5.0

5.1

Hydrochloric acid and inhibitor should be mixed in the acid tank. Ammonium bi-fluoride shall be prepared in the chemical tank. This will be mixed with the acid solution about a couple of hours prior to the commencement of acid injection.

Two independent sources of purge water are to be made available for boiler circulating water pumps.

Temporary switch board meant for the pumps of chemical cleaning process should be fed from two sources of AC supplies i.e. one from station switch-gear & other from DG sets.

Corrosion Rate (Metal loss in grams / m2 / hr.) test of Inhibitor should be carried out as per NACE standard before start of Acid cleaning activity.

Necessary First Aid facilities, including first aid box (containing dilute ammonium hydroxide, 50% sodium bicarbonate solution, eye lotion, bandages, tincture of iodine, cotton, burnol etc), should be available near the test area

SAFETY PRECAUTIONS :

SAFETY EQUIPMENTS: M/s. BHEL will ensure the availability of following safety equipment (Minimum quantities are projected against each items)

1. GUM BOOTS (Various sizes) 6 Pairs

2. Rubber gloves 6 Pairs

3. Rubber or Polythne aprons 6 Nos.

4. Helmets 12 Nos.

5. Safety goggles plain glasses 6 Nos.

6. Face mask (Transparent , plastic) 4 Nos.

STATUS

Signatures

NTPC BHEL



Sheet 9 of 38

Plant area: BOILER

PROCEDURE FOR BOILER ALAKALI BOIL OUT AND ACID CLEANINGSLNO

5.2

5.2.1

5.2.2

5.2.3

5.2.4

5.2.5

5.2.6

5.2.7

5.3

5.3.1

5.3.1.1

5.3.1.2

EMERGENCY PROVISIONS

Flushing and washing water supplies should be available near test area.

Ample supplies of tepid flushing and washing water supplies should be provided at all possible points of discharge, spillage or escape of chemicals.

Adequate provisions for emergency treatment of the eyes, with eye wash bottles, should be made at all those places where discharge, spillage or escape of chemicals can occur

Safety shower should be available.

A suitable first aid treatment room with outside telephone facilities should be provided within a reasonable distance of the place where chemicals are being used.

A suitable room should be provided for housing the protective clothing and apparatus required for emergency use.

Whenever any inspection is to be made during the cleaning process, the location should be adequately ventilated.

FIRST AID TREATMENT

Chemical splashes on the eye

Immediately flood the eye with water. To be effective the eyelids must be opened. The eyelids should be pushed apart using the thumb and index finger of the left hand. The casualty will probably not be able to open the eye himself because of painful spasms.

If an eye wash bottle is used the jet should not be directed at the front of the eye. It should be directed in from the side, so that flow is over the surface of the eye.

STATUS

Signatures

NTPC BHEL



Sheet 10 of 38

Plant area: BOILER


5.3.1.3

5.3.1.4

5.3.1.5

5.3.2

5.3.2.1

5.4

5.4.1

5.4.2

5.5

Irrigation should be continued for 5 – 10 minutes after which the casualty should be taken to the first aid room.

Irrigation should be continued in the first aid room. Remember vision is saved by thorough irrigation, no other treatment can prevent damage if this is omitted.

After thorough irrigation the eye should be covered with a pad; the patient should be referred for medical opinion.

Irritation of the skin

In the event of the splashing of chemicals on the skin, the affected area should be washed thoroughly avoiding the spread of contaminants to the face and eyes. If signs of skin irritation persist, the person should be referred for medical opinion.

Pipe Insulation

All temporary / Permanent pipelines carrying steam / hot water and likely to come in contact with persons should be insulated.

Test area should be cordoned off and entry of unauthorized persons should be prohibited. Suitable signboard should be displayed.

SAFETY OF PLANT:

A) If the Boiler light up can not be done within 3 weeks after completion of Chemical cleaning, the system should be suitably preserved.

B) Temperature limitations specified for various steps should not be exceeded.

STATUS

Signatures

NTPC BHEL



Sheet 11 of 38

Plant area: BOILER


6.0

6.1

6.2

6.3

6.4

EMERGENCY PROCEDURES :

The testing team should be aware of the operating procedures of fire extinguishers to be used for quenching fires.

The testing team should be aware of the procedure to be followed in case of accident involving injury to the person.

In case of failure of running circulating pump the stand by pump should be started immediately.

An operator posted at the pump area, should be instructed to stop the pumps and properly isolate the system in the event of emergency. Emergency operating instructions, in this regard should be prepared at site. All the test team members should be well conversant with the emergency operating instructions.

STATUS

Signatures

NTPC BHEL



Sheet 12 of 38


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7.6

7.7

STATE OF THE PLANT

Readiness of the following is to be ensured.

During the acid cleaning process, all the permanent boiler instruments are isolated except a temporary pressure gauge of 0 to 2.5 kg/ cm2

provided in the drum for monitoring nitrogen pressure in the drum during nitrogen capping.

For alkali boil out, neutralizing and passivation processes, essential control and instruments viz. Protections, interlocks, alarms, measurements, annunciation etc. required for safe light-up of boiler are made available, as per mutually agreed list between site NTPC and BHEL.

Boiler is flushed thoroughly including the temporary pipe lines and system. This should be done prior to the connection of temporary acid cleaning system to the main boiler.

The internals of the non-return valve provided in the economizer re-circulation line is removed in order to facilitate fast filling and draining of the boiler.

All the boiler auxiliaries are made ready and available for boiler light up. This includes Auxiliary steam, chemical dozing pumps, tanks, all boiler circulating pumps, fans, oil pumps etc. A checklist, containing minimum requirements of equipment / systems to be made ready prior to commencement of chemical cleaning is enclosed at 7.20.

Drum vent lines and Nitrogen capping lines are properly tagged and taken to suitable location for easy operation.

Prior to the commencement of alkali boil-out, alkali flushing (detergent flushing) of pre-boiler system is completed.

STATUS

Signatures

NTPC BHEL



Sheet 13 of 38


SLNO

7.8

7.9

7.10

7.11

7.12

7.13

7.14

7.15

7.16

For ABO, only primary separators are erected in upper drum and baffle plates are erected in lower drum. Secondary separators and Dryers not erected in the upper Drum and orifices not erected in the lower drum.

For Acid cleaning, the primary separators erected for ABO are also removed.

After completing acid cleaning, all the internals of upper and lower drum are installed back and both drums are normalized. (Please note that, baffle plates are already in erected condition in the lower drum).

In addition to the metal temperatures of the drum, additional temperature points with peening type temporary thermocouples are provided in the ring header (bottom drum) at minimum 4 locations at equal distances. Provision shall be made for monitoring temperatures in the control room.

O & M instruction manuals for the boiler and other auxiliaries including circulating pumps are available well in advance of the commencement of the cleaning process.

The pressure and temperature gauges and the flow-meter are installed as per the scheme.

All the safety measures discussed in advance are implemented. Suitable instruction / caution tags should be provided at strategic places/ equipment.

Provisions are to be made for adequate neutralisation of various drainings / effluents from different operations of the chemical cleaning process, prior to final disposal.

Boiler tube coupons are to be placed at two ends inside the boiler upper and lower drums of bottom ring header to see the effectiveness of the cleaning. It is to be ensured that the test coupons placed in the boiler upper drum are properly immersed in the solution.

STATUS

Signatures

NTPC BHEL



Sheet 14 of 38


SLNO7.17

7.18

7.19

7.20

Proper neutralization arrangement is available at site to neutralize and dispose off the effluent in line with state pollution control board norms.

Chemical dosing system is ready.

All Boiler circulating water pumps are ready.

MINIMUM REQUIREMENTS

1. Ensure the commissioning of the following including their protections, interlocks, measurements, alarms and annunciation:-a One ID fanb One FD fanc One Sec. Air Pre-Heater along with its

i. Soot blowing systemii. Fire detection and fire fighting system

iii. Rotor stoppage alarmiv. Oil carry over probev. Air motor(proper isolation of the other SAPH , in case it is not available, should be ensured)

d Steam coil air pre-heatere Light Diesel Oil firing system f Elevation of LDO firing equipment. g FSSSh SADCi DDCMIS j MMIPSk Scanner air systeml HP dozing system & LP dozing systemm All the CC pumps (Boiler Circulating Water pumps)n Measurements, alarms & annunciation pertaining to secondary

air system, flue gas system, feed water system, steam & boiler metal temperatures.

o Boiler bottom hoppers with furnace bottom sealing system and proper make up & over flow arrangements.

p Completion of gas tightness test of furnace and completion of its insulation.

q Completion of air tightness test of air and flue gas ducts and completion of their insulation

STATUS

Signatures

NTPC BHEL



Sheet 15 of 38

Plant area: BOILER

PROCEDURE FOR BOILER ALKALI BOIL OUT AND ACID CLEANINGSLNO

2. Ensure free expansion of the furnace and ducts and provision of expansion markers, along with punching of initial positions.

3. Blow-down system of boiler.4. Proper drainage system of boiler area.5. Readiness of two passes of ESP in all respects including

mechanical system, electrical system, EPMS and insulation.6. Adequate quantity of LDO stock & readiness of LDO handling

and pressurizing systems.9. Completion of pre-boiler system alkali flushing.10. Readiness of N2 capping system.11. Readiness of MD-BFP and feed system.12. Boiler water sampling system along with sample coolers (as per

mutually agreed between NTPC & BHEL site)13. Availability of auxiliary steam system for SCAPHs and Soot

blowing system of SAPHs.14. DC batteries, chargers and DCDBs.15. DG set, DG switch-gear, emergency switch gear and availability of

emergency supplies for Scanner air fan ,Emergency lighting etc.16. UPS17. Fire fighting system of concerned equipment.18. Air conditioning system of UCB, VFD room and ESP control room19. Equipment cooling system viz.

i. DM Cooling Water system along with plate-heat exchangers and alkali dozing system.

ii. Clarified Cooling Water system.20. Availability of adequate quantity of DM water. 21. Adequate capacity of instrument air and service air system22. Emergency operating instructions viz. AC power failure, D.C. power

failure, APH fire etc23. Adequate lighting in the operating areas.24. Public address system at all operating locations, including telephone

& walki-talkies at all affected areas25. Readiness of staircases, handrailings and platforms.26. Personal safety equipment.27. Readiness of drainage system of boiler and turbine zero metre

elevations.28. Easy access and approaches to all the operating equipments.29. Purge water is available to the CC pumps

STATUS

Signatures

NTPC BHEL



Sheet 16 of 38


SLNO8.0

8.1

8.1.1

8.1.2

8.1.3

8.1.4

TEST METHOD :

ALKALI BOIL OUT

The boiler (steam generating surfaces and economiser ) is filled with an alkaline solution containing 500 ppm of di-sodium phosphate dodeca hydrate, and 1000 ppm of Tri sodium phosphate do deca hydrate and then fired to raise the pressure to 40 kg/ cm2, following the specified operational procedures. During the process, rotation of boiler circulating water pumps should be done as per operating instructions.

Procedure Prepare the boil out chemical solution in hot de-mineralized water in the chemical mixing tank. The solution is formulated by dissolving the following proportionate quantities of chemicals, depending on the volume of the system to be cleaned.

1. 0.05% Na2 HPO4 12 H2O

2. 0.1 % Na3 PO4 12 H2O

Hold the solution prepared as above in the tank and homogenise the same by re-circulating the solution by operating temporary Chemical Injection pumps.

Start filling the boiler parallely through water wall, suction header of boiler circulating pumps and economiser with DM water, using temporary DM water pumps. Simultaneously start injecting the alkaline solution already kept prepared in the chemical mixing tank. Light up the boiler as per O & M instructions and gradually raise the

drum pressure to 40 kg/ cm2 . Hold the pressure for four hours. Collect boiler water sample from CBD sampling point for analysis for alkalinity, phosphate content, dissolved silica and oil content. Prescribe blow down after killing the fire. Duration of the blow down shall be for one minute. Ensure that the drum level does not go out of vision in gauge glass. Repeat the operation of raising the drum pressure to 40 kg /

cm2 holding it for 2 (Two hours) and prescribing blow down, of one minute duration, after killing the fire.

STATUS

Signatures

NTPC BHEL



Sheet 17 of 38


SLNO8.1.4.1

8.1.5

8.1.6

8.2

8.2.1

8.2.2

8.2.3

During the process if the phosphate concentration drops to half of the initial value, dose additional chemicals through phosphate dosing system to achieve original concentration.

NOTE: All the testing will be done as per the mutually agreed standard procedures. However, inhibitor efficiency test will be done as per NACE standard.

The boil out is declared complete when the oil content in the analyzed sample is less than 5 ppm or minimum eight blow downs are completed whichever is later.

Allow the boiler to cool as per O & M instructions and drain. Fill the boiler with DM water, heated to 800 C, through temporary DM water pumps. Back flush the super-heaters with DM water containing 200 ppm hydrazine and pH raised to 10.0 with NH

3 till it overflows into the

drum. Drain the boiler to the waste disposal system. Collect samples from the sampling points of Super Heater Header - 1 and low point drains for testing. Continue the process of DM water rinsing till the phosphate content in the samples is less than 2.0 ppm. Inspect the lower and upper drums and manually clean them.

NOTE

To speedup economiser filling and draining operation, the isolating valve in the economiser re-circulation line is to be kept opened and the internals are to be removed from the non-return valve provided in the economiser re-circulation line.

As far as possible, all the boiler circulating pumps should be kept running on rotation during alkali boil out. However, if due to any unforeseen reasons, any of the pumps remains out of service, the non-running pump is to be kept under continuous purging.

Whenever, boiler is to be filled with chemical solution and if the procedure calls for boiler light up, the following guide lines should be followed besides O & M instructions.

STATUS

Signatures

NTPC BHEL



Sheet 18 of 38

Plant area: BOILER


8.3.0

8.4.0

8.4.1

8.4.2

8.4.3

8.4.4

8.4.5

8.4.6

FILLING UP OPERATION:

The chemical solution should be filled up simultaneously through the bottom drum and economiser till the water level is seen at the lower most port of the level gauge.

LIGHTING UP

Besides following the O & M instructions the following points are to be taken care of.

Drum air vents are to be opened before lighting up the boiler.

The drum level has to be brought to the top port of the gauge glass. This would provide the necessary water for filling the headers and tubing above the normal water level.

Start one boiler circulating pumps in accordance with the operating instructions of boiler circulating pump.

After commissioning two pumps, take out or add water to establish 100 mm above normal level indicated in the gauge glass.

Initiate boiler light up as per O & M instructions.

Place further boiler circulating water pumps in operation when the drum pressure reaches 5 to 7 kg / cm2 and gradually bring the drum level to normal level as the pressure increases. Pumps should not be started during rapid boiler temperature changes. (More than 100 deg C / per hour).

STATUS

Signatures

NTPC BHEL



Sheet 19 of 38


SLNO

8.5

8.5.1

8.5.2

8.5.3

8.5.4

8.5.5

8.5.6

8.5.6.1

8.5.6.2

SHUTTING DOWN

When ABO is declared completed, box up the boiler keeping the boiler circulating water pumps in operation.

Allow the boiler to under go natural cooling by keeping all the dampers / gates" open" in the flue gas system.

Keep at least one pump running at drum pressures below 2 kg / cm2 and bring the water level to normal.

Open drum vent when the drum temperature is around 900 C to 1000 C.

Bring the water level in the drum to the lower most visible port in the gauge glass and stop the last boiler circulating water pump as per O & M instruction.

Drain the unit after attaining the desired cooling at the down comer and suction manifold.

By following the above procedure, pump vibrations are contained and air ingress is also averted.

Chemical feeding pumps and temporary DM water pumps should be started simultaneously to achieve the controlled feeding of chemicals for uniform concentration of the solution being fed to the boiler. Boiler filling should be done through water walls and economizer simultaneously. Uniform and required concentration can be obtained by throttling respective control valves.

STATUS

Signatures

NTPC BHEL



Sheet 20 of 38


SLNO8.6

8.6.1

8.6.2

8.6.3

ACID CLEANING

Acid cleaning is carried out by adopting soaking technique, using hydrochloric acid of 5% + 1%, 0.2% V/V inhibitor Rodine 213 Special (preferred inhibitor) or 0.3% V/V of inhibitor Coronil 213 Special and 0.25% ammonium bi-fluoride (Inhibitor Coronil is to be used only when Rhodine is not available). Pickling by acid is followed by plain DM water rinse, ammoniated citric (0.2 %) rinse, plain DM water rinse and neutralization of the pickled surfaces with a mild alkaline solution containing a mixture of di and tri sodium phosphates. Finally, the entire cleaned and neutralized surfaces are passivated with ammoniated – hydrazine solution at an elevated temperature and pressure. All the draining operations prior to the neutralization step are to be done under nitrogen capping. The gauge glass used for alkali boil out is to be replaced by a polythene tube.

MOCK TRIAL:

A mock trial should be conducted, prior to the commencement of the pickling operation, to check the healthiness of the temporary system erected and to acquire an idea of operations of various valves, pumps and other connected system, so that actual operation is carried out to the nearest accuracy. The boiler filling in 1 (one) hour (approx.) and draining in 1(one) hour (approx.) are to be achieved. PROCEDURE:

Fill the boiler parallely through water wall and economizer with plain DM water up-to the bottom port of gauge glass. Stop filling though water wall and economizer. Now, back fill the super-heaters with DM water containing a min. of 200 ppm hydrazene with solution pH raised to 10.0 using ammonia. Continue back flushing the super heaters till the drum level comes to normal operating level. Having ensured that the super-heaters are filled, light up the boiler as per the O & M instructions and raise the metal temperature both of the drum and suction manifold to 800

C with boiler circulating pumps in service. Once the temperature is reached, shut down the boiler and drain water from boiler to the waste disposal system. Close all the furnace openings to retain the heat in the boiler.

STATUS

Signatures

NTPC BHEL



Sheet 21 of 38


SLNO8.6.3.1

8.6.3.2

8.6.3.3

8.6.3.4

8.6.3.5

Mix the required quantities of 30 – 32% Hydrochloric acid and inhibitor Rodine 213 Special or Coronil 213 special, and keep it ready in the acid tanks (2 Nos.). Dissolve required quantity of ammonium bi-fluoride in D.M water and keep it ready in the chemical-mixing tank. Transfer the ammonium bi-fluoride solution equally into the two acid tanks. Thoroughly mix the inhibited acid and transferred ammonium bi-fluoride solution by running the chemical injection pump on re-circulation for a minimum of one hour, particularly prior to the commencement of chemical injection into the boiler.

Keep all the boiler blow down valves shut and drum vent valves open to facilitate escape of gases generated during pickling process.

Keep the nitrogen capping system ready prior to the commencement of acid filling.

Choose the centrally located boiler circulating pump for operation to circulate the chemical solution during soaking / pickling time. Keep a continuous supply of purge water to all the boiler circulating pumps.

Start filling the boiler parallely through water wall, suction header of boiler circulating pumps and economizer with heated DM water, temperature restricted to 650 C – 700 C. Simultaneously start injecting the chemical solution already kept prepared in the acid tanks (mixture of inhibited hydrochloric acid and ammonium bi-fluoride) along with the fill water. Suitably control the opening of the control valves to achieve a uniform acid concentration of 5% + 1% in the water being filled in the boiler. The regulation of uniform acid concentration is done by very frequent sampling, from point 'A’ as shown in the scheme, testing and suitably adjusting the opening of the chemical injection control valves. The temperature of the chemical mixed water should not exceed 650 C to 700 C at any point of time. Stop filling through suction header of Boiler circulating pump, when the level in the drum is at the bottom of the gauges glass. But continue filling through the bottom drum and economizer till the level in the drum touches 100 mm above the center line of the gauge glass.

STATUS

Signatures

NTPC BHEL



Sheet 22 of 38


SLNO

8.6.3.6

8.6.3.7

8.7

8.7.1

This will ensure complete filling of ECO links to the drum and the water wall riser tubes. Do not permit the level to go out of sight in the gauge glass.

Once the filling is completed, start the selected boiler circulating pump and collect samples at every 5 minutes interval from discharge of boiler circulating pump and analyze for acid strength and iron concentration. At the end of 30 minutes period stop the pump and allow the chemical solution to soak. Operate the same boiler circulating pump, that was in service earlier, for 5 minutes at an interval of 30 minutes each. Carry out the sampling at every 10 minutes interval and analyze for iron concentration. Acid pickling / soaking process is to be continued till iron concentration in three consecutive samples show equilibrium status. If the iron concentration values do not level out and attain equilibrium status, regardless of analytical results, the total acid contact time will not be allowed to exceed 6 hours including the time for filling and draining.

Prior to draining operate the same Boiler circulating pump, that remained in service earlier, for 5 minutes. Stop the pump and drain the boiler as fast as possible, under Nitrogen Capping, maintaining the nitrogen pressure in the drum around 0.5 to 1 kg/ cm2 .

DM WATER RINSE

Re-fill the boiler by running the temporary DM water pumps with DM water heated to a temperature of 600 C – 650 C. Carefully operate the drum vent valves to maintain 0.5 kg/ cm2 Nitrogen pressure in the drum. Fill the water up to the centre of the gauge glass. Further raise the level in the drum by 100 mm, by back flushing the super-heaters with treated water.

This will also remove the traces of acid vapors lodged, if any, in the connecting links of the super-heaters. Now run the same boiler circulating water pump, which was operated earlier, till the uniform concentrations of acid and iron are attained in the system as indicated by analysis of the sample taken from the discharge of the boiler circulating pump at sample point ‘A’. Analyse the sample for pH. The pH of the DM rinse should not be allowed to go above 4.0. Drain the boiler under nitrogen capping as practiced earlier.

STATUS

Signatures



Sheet 23 of 38


SLNO8.8

8.8.1

8.8.2

8.8.3

8.8.4

8.9

8.9.1

AMMONIATED CITRIC ACID RINSE

Prepare a solution of ammoniated citric acid with the required quantities of citric acid mono-hydrate and liquor ammonia in the chemical mixing tank, equivalent to get a concentration of 0.2% acid in the water entering into the boiler (as stipulated in clause 8.8.3). Keep the solution under re-circulation to maintain homogeneity.

Start filling the boiler parallely through the Boiler circulating pump suction header, water wall and the economiser with hot DM water restricted to a temperature of 600C to 650C. Simultaneously start injecting ammoniated citric acid solution.

Maintain a uniform strength of 0.2% acid in the water taken into the boiler. Adjust the pH of the final solution entering the boiler at sampling point ‘A’, between 3.5 and 4.0. Continue the filling operation, till the level in the upper drum is close to the bottom of the gauge glass. Now close the valve in boiler circulating pump suction header & further raise the level in the drum up to middle of the gauge glass by filling through the economiser & water wall so as to fill economiser and water wall connecting links.

Start the same boiler water circulating pump that remained in operation earlier, run it for 5 minutes at an interval of every 30 minutes and collect the sample from Boiler circulating pump discharge after stoppage of Boiler circulating pump. Check for acid % and iron concentration.

When iron concentration attains a steady state value for 3 consecutive readings, citric acid rinsing is declared complete. In any case it should not be declared complete in less than 4 hours or more than 5 hours. Drain the boiler under nitrogen capping as practiced earlier

DEMINERALISED WATER RINSE

After draining the citric acid solution, start filling the boiler with DM water heated to 600C – 650C. parallely through the boiler circulating pump suction header, water wall and the economizer. Raise the level in the drum upto + 100 mm mark. Operate the boiler circulating water pump for 5 minutes. Stop the pump and drain the boiler under nitrogen capping as practiced earlier

STATUS

Signatures

NTPC BHEL



Sheet 24 of 38

Plant area: BOILER


8.9.2

8.10

8.10.1

8.10.2

8.10.3

8.10.4

Repeat the filling and the dumping / draining operation under Nitrogen Capping till the iron content in the sample collected at sampling point ‘B’ is less than 25 ppm.

Maintain the nitrogen atmosphere in the system by maintaining a pressure of 0.5 to 1.0 kg / cm2 till the next process of neutralization is started.

NEUTRALISATION

This process is employed to neutralise any acid / acidic pocket remaining in the system and also to mildly passivate the acid pickled surface. This prepares the base for achieving an effective final passivation. For this process, the boiler system and the necessary instrumentation should be made ready to make firing feasible. The polythene tube provided for the acid pickling in the drum shall be replaced by the gauge glass. All the boiler water circulating pumps should be made ready for operation.

Prepare the neutralising solution in the chemical mixing tank with required quantities of di-sodium phosphate do-deca hydrate and tri-sodium phosphate do-deca hydrate to get a concentration of 0.1% and 0.2% respectively in the boiler.

Re-circulate the solution in the tank to homogenize the mixture. Start filling the boiler with DM water, parallely through the boiler circulating pump suction header, water wall and the economizer with simultaneous injection of phosphate solution, maintaining uniform concentration throughout the filling period, under the nitrogen capping as practiced earlier. Regulate the drum vents to maintain N2 pressure between 0.5 to 1.0 kg / cm2. Once the boiler filling is complete, open the drum vents. Start the boiler water circulating pumps as per the O & M instructions. Fire the boiler and gradually raise the pressure to 10 kg / cm2 .

Follow the precautions as detailed for alkali boil out. Hold the pressure at 10 kg / cm2 for 6 hrs. Utilize this opportunity to blow off all the instrument lines that might have come into contact during acid pickling time, for better neutralization of these lines

STATUS

Signatures

NTPC BHEL



Sheet 25 of 38

Plant area: BOILER


8.11

8.11.1

8.11.2

8.11.3

8.11.4

8.11.5

8.11.6

After 6 hours, kill the fire, the natural cooling of the boiler be done and subsequently drain the boiler as per procedure explained earlier. The boiler is drained with the drum vents open to the atmosphere. While draining, back-flush the super-heaters with DM water conditioned with hydrazine and ammonia. Allow the system to aerate. Prepare the boiler for passivation.

PASSIVATION

The underlined idea is to form a protective magnetite coating on the steam generating and water touched surfaces that were exposed to the pickling process.

Prepare a blended solution of hydrazine and ammonia with calculated quantities in the chemical mixing tank in order to finally achieve a minimum residual amount of 200 ppm hydrazine and a solution pH of 10.0 when filled in the boiler.

Start filling the boiler with DM water, parallely through the boiler circulating pump suction header, water wall and the economizer with simultaneous injection of hydrazine – ammonia mixture as practiced earlier, up-to the operating level in the drum gauge glass.

Prepare the boiler for firing as per O&M instructions, start the boiler water circulating pumps and fire the boiler at a slow rate. Raise the drum pressure to 40 kg / cm2 and hold it for 24 hrs and maintain a residual hydrazine content of 25 ppm & a solution pH 10.0 in the feed water being fed into the boiler during the entire passivation operation.

After 24 hours of operation, shut down the boiler and allow it to cool slowly. Keep the boiler circulating water pumps in service as per the O&M instructions. Shut down the pumps when the metal temperature drops to 950 C.

Drain the boiler under atmospheric pressure and aerate the system

STATUS

Signatures



Sheet 26 of 38


SLNO

8.11.7

8.12

8.12.1

8.12.2

8.12.3

8.12.4

8.12.5

Open the upper and lower drums for inspection. Take out the coupon and inspect it for uniform cleaning and magnetite coating. Manually clean the upper & lower drums. Refit the drum internals, restore the boiler and prepare it for regular operation for steam blowing, safety valve floating etc.

NEUTRALISATION OF EFFLUENTS

Effluents generated during following activities will be neutralised and disposed off in line with State Pollution Control Board norms.

Alkali Boil Out & Neutralisation of pickled surface:

pH of the solution is lowered to less than 9.0 by sufficient dilution with water.

Acid pickling

Effluent is neutralised with Caustic Soda Lye & Lime Powder. pH of disposed effluent is to be maintained between 5.5 to 9.0 and fluoride content less than 2.0 ppm.

Citric Rinse

Effluent is neutralised with Caustic Soda Lye. pH of disposed effluent to be maintained between 5.5 to 9.0.

Passivation

Hydrazine & Ammonia is neutralised with bleaching powder.

The cleaning activity should be done with such a planning that the boiler start up should be possible immediately after completion of cleaning process.

STATUS

Signatures

NTPC BHEL



Sheet 27 of 38

Plant area: BOILER


9.0

9.1

9.2

9.3

9.4

9.4.1(Ref.8.1.5)

9.4.2(Ref.8.1.6)

9.4.3(Ref.8.1.6)

9.4.4(Ref.8.1.3.6)

9.4.5(Ref.8.7.1)

COMPLETION CRITERIA:

The test coupons placed at identified locations shall be taken out in the presence of NTPC and all coupons should have uniform cleaning. Make a joint record.

The drum surface will be visually inspected for uniform smooth coating of magnetite.

The low point headers will be inspected and loose debris if any, will be removed.

Termination Criteria for each step will be as follows:

Alkali Boil out : [ oil ] < 5 ppm or minimum 8 blow downs, which ever is latter

Rinsing (After ABO) : [ PO4 ] < 2 ppm.

Super heater back-flushing : : [ PO4 ] < 2 ppm.

Acid Cleaning : Acid pickling / soaking process is to be continued till iron concentration in three consecutive samples show equilibrium status. If the iron concentration values do not level out and attain equilibrium status, regardless of analytical results, the total acid contact time will not be allowed to exceed 6 hours including the time for filling and draining.

DM Rinse : After circulation, the system is drained under nitrogen blanketing. ( pH shall be up to 4.0 )

STATUS

Signatures

NTPC BHEL



Sheet 28 of 38


SLNO

9.4.6(Ref.8.8.4)

9.4.7(Ref.8.9.1)

9.4.8(Ref.8.10.3/4)

9.4.9(Ref.8.11)

Citric Rinse: Same as acid pickling except that the pickling time should not be less than 4 hours or more than 5 hours

DM Rinse : [ Fe ] < 25 ppm

Neutralization: Hold the Boiler pressure at 10 kg/ cm2

for 6 hours.

Passivation : Coupons inspection to be carried out after passivation

STATUS

Signatures

NTPC BHEL



Sheet 29 of 38


SLNO

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

NOTE (Refer Drg.No. 4:PS:TSX:137:00Drains to be provided at lowest points of temporary piping.

Sampling point to be provided at least 5 metres away from the acid mixing point.

Second sampling point at the tail (farthest end from acid mixing point of the circuit.

Temporary lines connecting main boiler up to first isolating valve should withstand 40 Kg/ Sq.Cm. Accordingly, the pipe selection to be made.

Rubber lined valves should be provided in the entire chemical injection system up to the final injection point in the main feeding line. The regulating valves should be of bottom diaphragm type.

Pressure gauges in the chemical injection system should be of diaphragm type.

Rubber lining provided in the various valves and pipe lines should be resistant to heat, acid and alkali.

15 Cu.M. tank to be epoxy coated internally and leak test to be done before insulating the tank.

All temporary connections to Boiler should be of radiographic quality.

40 Cu.M. tank to be leak tested before insulation.

2 Nos. of Acid Storage Tank to be spark tested (By the vendor).

Small drains not connected to neutralising pit to be neutralised locally with lime powder and let into storm water canal as per state pollution control norms.

Service water supply should be available near the pump operating areas.

Additional checklists / modifications in the lay-out, if found necessary, to be made at site in consultation with site commissioning in-charge.

STATUS

Signatures

NTPC BHELSHEET 31 of 38

10.f ALKALI BOIL OUT

LOG SHEET NO. 1

DATE:

PROJECT :UNIT :

I. ADDITION OF CHEMICALS:

DATE TIME (HRS) NAME OF CHEMICAL QUANTITYADDED.

II. ANALYTICAL DATA:

Sl. No. DateTime (HRS)

Total Alkalinity as CaCO3 (PPM)

Total Phosphate (PPM)

Silica (PPM)

Oil(PPM)

Signatures

BHEL NTPCSHEET 32 of 38

10.f BOILER CHEMICAL CLEANING

LOG SHEET NO. 2

DATE:

PROJECT:UNIT :

ACTIVITY : SUPER HEATER BACK FLUSHING & FILLING

ANALYTICAL DATA:

Sl. No.

DATE TIME (HRS)

PO4

(PPM)PH HYDRAZINE

PPMREMARKS

Signatures

BHEL NTPC

SHEET 33 of 38


LOG SHEET NO. 3

DATE:

PROJECT:UNIT :

ACTIVITY : ACID PICKLING.



III. ANALYTICAL DATA:

Sl. No. DATETIME (HRS)

ACID STRENGTH %

TOTAL IRON (PPM)

REMARKS

Signatures



LOG SHEET NO. 4

DATE:

PROJECT:UNIT :

ACTIVITY: DM WATER RINSE

ANALYTICAL DATA:

SL. NO DATETIME (HRS)

ACID %IRON (PPM)

REMARKS

Signatures



LOG SHEET NO. 5

DATE:

PROJECT:UNIT :

ACTIVITY : CITRIC ACID RINSE



II. ANALYTICAL DATA :


PHCITRIC ACID %

IRON PPM

Signatures

BHEL NTPC

SHEET 36 of 38 10.f BOILER CHEMICAL CLEANING

LOG SHEET NO. 6

DATE:

PROJECT:UNIT :

ACTIVITY : DM WATER RINSE.

ANALYTICAL DATA:


PHIRON (PPM)

REMARKS

Signatures

BHEL NTPC

SHEET 37 of 38


LOG SHEET NO. 7

DATE:

PROJECT:UNIT :

ACTIVITY : NEUTRALISATION:



II. ANALYTICAL DATA :


PHTOTAL ALKALINITY AS CaCO3

REMARKS

Signatures

BHEL NTPC

SHEET 38 of 3810.f BOILER CHEMICAL CLEANING

LOG SHEET NO. 8

DATE:

PROJECT:UNIT :

ACTIVITY : PASSIVATION.



II. ANALYTICAL DATA:


PHHYDRAZINE (PPM)

REMARKS

Signatures

BHEL NTPC

BOILER ALKALI BOIL OUT AND ACID CLEANING

PS:TSX:160:00:03

PROJECT : RAMAGUNDAM 500MW

TECHNICAL SERVICES DEPARTMENT

BHARAT HEAVY ELECTRICALS LIMITED(A Government of India Undertaking)

Power Sector – Southern Region474, Anna Salai, Nandanam, Chennai – 600 035.

PROJECT RAMAGUNDAM 500MW

PROCEDURE BOILER ALKALI BOIL OUT AND ACID CLEANING

PURPOSE OF DOCUMENT

FOR EXECUTION / INFORMATION

DOCUMENT NO. PS:TSX:160 :00:03

COPY NO:

ISSUED TO:

00 KJ MJH RVS 14.05.2003

Rev. No. Prepared by Reviewed by Approved by Date

TECHNICAL SERVICES DEPARTMENT

BHARAT HEAVY ELECTRICALS LIMITED(A Government of India Undertaking)

Power Sector – Southern Region474, Anna Salai, Nandanam, Chennai – 600 035.

ACID CLEANING OF BOILER RAMAGUNDAM 500 MWDRG. NO: 4 PS. TSX. 0137 :00DRAWN CHECKED APPROVED DATEKJ MJH RVS 14.05.03

ACID CLEANING SCHEME FOR RAMAGUNDAM 500 MW (TYPICAL)

Documents

Chemical Cleaning