m33-Chemical Cleaning of Utility Boiler

LARSEN & TOUBRO LTD.

O&M POWER

238.5MW CAPTIVE POWER PLANT PANIPAT NAPTHA CRAKER PROJECT,

INDIAN OIL CORPORATION LTD. PMC-EIL

DATE: Page 1 of 24

SUBJECT Pre Commissioning Procedure for Chemical Cleaning of Utility Boiler DOC No.: 6556-EPCC4-52-O-M-0M33

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Chemical Cleaning of Utility Boiler

Procedure No. : LNT/POWER/IOCL/M/CC-UB/COMM

LARSEN & TOUBRO LIMITED L&T Energy Centre,

Near Channi Jakatnaka Baroda 390002


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Revision No.

Date Description Author Reviewed By Approved By


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Contents

Sr. No. Title Page No. 1 Cover Page 1 2 Revision Status 2 3 Contents 3 4 Record Of Revision 4 5 Chapter -1: Objective 5 6 Chapter-2 : Reference 6 7 Chapter-3 : Pre-Requisites 7 8 Chapter-4 : Precautions and Notes 8 9 Chapter-5 : Acceptance Criteria 9 10 Chapter-6 : Test Equipment 10 11 Chapter-7 : Pre Commissioning Activity Plan 12 12 List Of Checklists and Annexures 19


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Revision Record Sheet

Chapter No. Section No. Remarks


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1.Objective

The objective of this procedure is to provide guidelines for CHEMICAL CLEANING OF

UTILITY BOILER.

Chemical Cleaning of Utility Boiler includes the following activities :

( a ) Preliminary Flushing

( b ) Hot Alkali Flushing

( c ) Inhibited Inorganic Acid Cleaning

( d ) Neutralisation and Passivation

( e ) Final In-Service Passivation

The Chemical Cleaning activity shall be facilitated by the following external equipments installed temporarily for the cleaning operation.

- Temporary Tanks ( for mixing the chemicals & preparation of the cleaning solution )

- Circulation Pumps ( for transfer of chemicals from the tank to the system piping which are to be cleaned and circulating the cleaning solution)

- External Heat Source (for raising the temperature of the circulating solution during the cleaning process)


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2.References Sr.No Drawing /Documents Diagram No and revision

1 P & ID of BOILER WATER AND STEAM SYSTEM DRUM AND FURNACE

6556 EPCC4 PI P 52 1B - 1101

2 OEMs CHEMICAL CLEANING PRESCRIPTIONS ( ANSALDO )

6556 EPCC 4 52 1B SPM - 3008

3 Applicable Standards and Codes 4 OEMs O&M Manuals 5 MSDS of Chemicals 6 Chemical Cleaning Schemes /

Loops


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3.Pre Requisites

Sl.No Job Description Remarks Records

1 Completion of Civil construction, Availability of Lighting in UTILITY BOILER area.

2 Installation of Equipments, Piping, Valves and Instruments as per P&I diagram.

3 Availability of Electric Power & Emergency DG Power

4

Availability of required manpower with required Tools and Tackles. Chemists required for analysing samples taken during various stages of Cleaning Process.

5

Availability of P&I Diagrams, GA Drawings, List of Chemicals & Reagents and O&M Manuals listed in the Reference.

6 Availability of First Fill of Lubricants required during Start up, Pre-Commissioning & Commissioning

7 Provision for proper approach to equipment.

8 Preparation of Erection Punch List and jointly signing of the same.

9 Availability of Instrument and Service Air

10 Format III / IV Clearance from EIL / IOCL

11 Availability of required DM Water for flushing and rinsing operations

12 Installation and Testing of Temporary Cleaning Circuit including equipments and associated Piping .

13 Neutralisation Pit ready for safe disposal of treated effluents

14 Availability of Chemicals , Nitrogen , Acid, Inhibitors , Diesel and other Reagents


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required for the Chemical Cleaning process.

15 Temporary Laboratory Set up for analysing the samples taken during the course of Chemical Cleaning.

16

Availability of Personnel Protective Equipments Rubber Gloves , Apron , Gum Boots , Safety Goggles , Nose masks etc.


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4.Precaution and Notes

Sr.No Pre-cautions Yes/No

1 Area under commissioning should be completely tagged and barricaded and only authorised persons should be permitted to enter in this area.

2

To protect personnel and the equipment, barriers, danger signs, safety tags, area restrictions, etc. should be displayed. A safety check shall be carried out before pre-commissioning /commissioning activity.

3 The equipment should be stopped if unusual sound or excessive vibration is observed.

4 Proper communication should be established between the UB area and the control room.

5 Prior to the commencement of the Chemical Cleaning of UB , equipment and the operational area should be thoroughly cleaned.

6

Line up of equipment /system (interconnected) & settings are checked before any trial run/charging to avoid potential safety /fire hazards/accident to equipment and /or human being arising out of open connections / blanks, leaks, grounding , inadvertent charging etc. Removal of Blanks in the piping to / from the equipment shall be ensured except if specifically required.

7 Applicable MSDS should be displayed nearby the equipment.

8 Based on the site conditions, minor changes to the procedure may be incorporated at site. OEMs Instructions/Guidelines shall be followed.

Commissioning Engineer Site Safety In-Charge


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5.Acceptance Criteria

Sr. No Criteria Format

1. The Chemical Cleaning must be able to achieve : ( a ) Removal of organic products used for preservation ( b ) Absence of mud and foreign matter. ( c ) Removal of oxides and scaling from all wetted surfaces of

the boiler.

( d ) Formation of a compact and adherent magnetite layer.


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6.Test Equipments

Sr. No.

Pre Commissioning / Commissioning tests Test equipments list Remark

1. Chemical Cleaning

Instruments Pressure Gauges , Temperature Gauges and Flow meters installed in the Temporary Cleaning Circuit

2. Testing Kit for analyzing samples PH Meter , Specific Conductivity Analyser , Turbidity meter etc.


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7.Pre Commissioning Activity Plan

Inspection Agent

Sr.No Activity

L&T EIL

Record Remark

1. System Identification , Isolation and Tagging 2. Safety Precautions 3 Chemical Cleaning Operations

3.1 Flushing 3.2 Hot Alkali Flushing 3.3 Acid Cleaning 3.4 Neutralization and Temporary Passivation 3.5 Final In-service Passivation 3.6 Controls 3.7 Cleanliness Evaluation 4 Restoration of System

HP - Hold Point. W- Witness by owner/PMC. RW - Review of contractor documents. S- Surveillance inspection by Owner/PMC. WC - 100% inspection by Contractor


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Sr. No

Steps to be carried out Remarks

1.0 System Identification , Isolation and Tagging

1 Identify each system to be cleaned and clearly define the extent of cleaning.

2 Prepare Schematic diagrams to define the pre boiler system, boiler system and piping to be cleaned.

3 Identify branch lines , bypasses , instrument connections and parallel circuits of various sizes and configurations.

4 Design temporary piping to include all system piping and equipment to be cleaned and flushed.

5 Establish temporary connections in the pre boiler system to create a once through system for flushing.

6 Minimise non flushing area.

7 Block spring supported piping to prevent spring damage during chemical cleaning.

8

Keep dead legs and by pass lengths as short as possible. Wherever possible , Make provisions to drain or blowdown legs. Consideration must be given to branch lines and dead legs to ensure an adequately cleaned system.

9

After installing all temporary piping and circulation equipment , the system should be hydrostatically tested at 1.5 times the expected cleaning pressure to identify any leaks prior to introducing chemicals. Pressurize to identify any leaks prior to introducing chemicals .

10 Include all piping to be used to transport solvent and other chemical agents.

11 Isolations required to be done on the boiler , removal of internals of valves , flow meters etc. shall be as per OEM 's recommendations.

12 All required preparations and provisions must be done as follows :

13 Any permanent flowmeter must be removed from the circuit under cleaning

14 Valves and Instruments must be protected by suitable temporary preparation , isolation or removal , i.e., internals of non return valves to be removed.

15 Instruments in the permanent piping shall be installed after completion of Cleaning process.


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16 Any part of under cleaning circuit and / or piping not compatible with acid solution must be suitably protected , for instance by counter filling with DM water

17

All temporary installation required for Chemical Cleaning must be erected according to good engineering practice , such as sample connections for chemical analysis, temporary levels , flowmeter and temporary valves, vents and drains , tanks ,pumps , heaters, instrumentation and all other necessary equipment

18 All the required laboratory facilities must be operational and available.

2.0 Safety Precautions

1 All personnel involved in the cleaning operation must be informed of all required safety precautions

2 Provide temporary showers and eyewash stations , if required , along with other safety equipment.

3 Schedule the Cleaning Operation in such a way that there will be no power supply cut during the process.

4 Adhere to all safety aspects in handling of chemicals during Chemical cleaning.

5 Corden off the surrounding area and post appropriate warning signs.

6 All required safety procedures must be applied and working areas must be restricted to operating personnel only.

7 Note : Considering that once started , Acid Cleaning phase must continue without interruption until upon the completion of the same.

3.0 Pre Operational Chemical Cleaning

( a )

Boiler Chemical Cleaning is required to remove eventual tube working residuals , oxide formation , due to possible bad material preservation , oil substances used during manufacturing and preservation , weld spatter , rust ,oxide scales in order to have a good active metallic surface to get strong thin and uniform magnetite layer inside boiler pressure parts.

( b ) Velocities : Successful Cleaning requires solvent velocities in the range of 0.2 to 1.2 m/sec through boiler sections depending on type of acid used.


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( c )

Conceptual Design : Cleaning Circuit is based on obtaining and maintaining the required velocities , with an acceptable cleaning solvent , to adequately remove oxide scale from the internal surfaces of economiser and furnace waterwall tubes.

( d )

Accomplish the above step by feeding economiser by external pumping station , cleaning furnace walls by nitrogen recirculation at downcomers bottom and by solution return to pumping station.

( e ) Provide Flowmeter and valves on the temporary piping to economiser.

Chemical Cleaning operations

3.1 Flushing

1 Carry out the Flushing operation just before Chemical Cleaning

2 To accomplish an effective Flush , Flow rates should be as high as possible and circulating pumps shall be used.

3

Flushing shall be done using DM water and shall be continued until water going to waste is observed to be clear and after filtration without appreciable suspended solids from any boiler section.

3.2 Alkaline Cleaning ( Hot Alkali Flushing )

1 Carry out the Alkaline Cleaning by injecting an alkaline solution in order to remove oils and rust inhibitors which are applied to internal tube surfaces.

2 Prepare an alkaline solution containing 2000 ppm Tri Sodium Phosphate , 1000 ppm Di Sodium Phosphate and a compatible wetting agent.

3 Heat the circulating water to bring its temperature to about 90 deg.C. Heating shall be done by the heating station placed in the temporary circuit.

4 Continue the circulation at 90 deg.C for atleast 18 to 24 hours after the alkaline chemicals have been injected.

5 Perform periodical Checks

6 When the circulation has been stopped , Displace the alkaline solution by draining and rinsing with DM water.

7 Maintain the system in the same condition until acid cleaning.


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8 Note : If several days will elapse before acid cleaning , it is recommended that ammonia and hydrazine (10 ppm and 200 ppm respectively ) are used in water.

3.3 Inhibited Inorganic Acid Cleaning

1 Carry out the Acid Cleaning to remove oxides , scales , siliceous substances from inside the pressure parts.

2 Acid solution shall be inhibited by suitable and reliable inhibitor in order to keep the corrosion rate lower than allowed value.

3 Establish the rated circulation in the circuit. Control the solution flow to achieve and maintain suggested velocities in every section of pressure parts which are under cleaning.

4 Ensure that the Superheaters backflushing is in operation.

5

During Cleaning of Economiser and Furnace walls , an extra circulation may be installed by injection of Nitrogen at downcomers bottom through installed special nozzles , in addition to the temporary pumping station.

6 Maintain the Temperature at specified value during acid cleaning by very good and uniform warming of all the circuit under cleaning before chemical injection.

7

Note : After Chemical injection , it is forbidden to light up boiler and the only way to heat the circulating solution is by means of an external heat source (could be thermic fluid heat exchanger) at very low heating rate, to compensate heat dispersion.

8 Inject the required quantity of Corrosion Inhibitor ( Rodine 213 or equivalent) into the system.

9 Gradually Add Hydrochloric acid and Initiate Circulation of the solution , Maintain the operating temperature within 60 70 deg.C

10 Initially , Open all the vents in the cleaning circuit to allow escape of Hydrogen generated by the acid reaction.

11 Continue the Circulation for 4 5 hours and Perform periodic sampling.

12 Complete the activity when the acid concentration gets stabilized and Iron content determinations becomes constant.

13 Drain the acid solution under Nitrogen blanketing.

14 Carry out Rinses to wash carefully all sections of the circuit , including temporary piping with all involved equipments.


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15

Pay special attention to wash and clean by draining and / or back filling all dead pipes and connections of the circuit by operating section by section and by checking the resultant outgoing conductivity.

3.4 Neutralization and Temporary Passivation

1 Carry out the Neutralization of eventual iron and / or acid traces that could be still in the boiler tubes.

2 It is performed in two steps as below :

3 Firstly an acid phase to be obtained to neutralise iron ( a correct pH value could be 4.5 )

4 Secondly a basic phase to be obtained by recirculating a basic solution (pH 9.5 10 ) to neutralise acid traces.

3.5 Final In Service Passivation

1 Flush the boiler sections until the effluent conductivity is not more than 20 S / cm.

2 Fill the boiler completely (including Superheater) with DM water added with Hydrazine and Ammonia.

3 Fire the boiler and Raise the pressure to 5 bar in about 3 hours.

4 Starting from the pressure of 2 bar , Perform quick discharges by operating boiler drains.

5 Check at the end of this operation , the Hydrazine content should be about 70 100 ppm.

6 Raise the pressure to 10 bar in about 2 hours , and Perform the discharges as above.

7 Maintain the boiler at this value for 3 hours and Note the Hydrazine content will be about 50 70 ppm.

8 Operate the boiler in this fashion as shown in the Passivation Curve (LNT/POWER/IOCL/M/CC-UB/4)

9 Finally Raise the Pressure to 45 bar in about 3 hours. Note the hydrazine content will be 1 5 ppm.

10 This activity completes the Boiler Chemical Cleaning operation.

11 Release the boiler for further operation.

3.6 Controls

1 Perform the Checks of the control parameters during the various stages of chemical Cleaning and Record the Observations as per


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3.70 Cleanliness Evaluation

1

Carry out the evaluation of the cleanliness degree obtained by chemical cleaning by direct control of atleast three representative samples taken from the boiler after the cleaning operation.

4.0 Restoration of System

Restore the Boiler and Preserve the Boiler for further operation.


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List of Check Lists & Annexures

Sl. No

Description Format

1. Check List for Temporary Chemical

Cleaning of Circuit

LNT/POWER/IOCL/M/CC

-UB/1

2. Format for recording Data of Chemical

Cleaning of Utility Boiler

LNT/POWER/IOCL/M/CC

-UB/2

3. Lay out of Temporary Chemical Cleaning

Circuit

LNT/POWER/IOCL/M/CC

-UB/3

4. Final In service Passivation - Curve LNT/POWER/IOCL/M/CC

-UB/4

DATE:


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Page 20 of 24 Format No. : L&T/POWER/IOCL/M/CC-UB/1

SUBJECT Pre Commissioning Formats for Chemical Cleaning of Utility Boiler DOC No.: 6556-EPCC4-52-O-M-0M33

Tested by Larsen & Toubro Ltd.

Witness By

Witness By

Name: Signature

Name: Signature

Name: Signature

CHECK LIST -1 CHECK LIST FOR TEMPORARY CHEMICAL CLEANING CIRCUIT

Sl No

Description Result Remarks

1. Check for the installation of temporary cleaning equipments wit respect to the cleaning schemes/loops

2. Check for the cleanliness of the equipment and associated piping

3. Check the valves in the system for correct open/close operation.

4. Check for the availability of electrical supply for the temporary circulation pumps

5. Check if the temporary pumps trial run is completed

6. Check if the instruments installed are calibrated and functionally tested

7. Check for the installation of special devices orifices, flowmeters, plugs if any

8. Check for the availability of list of blanks installed , if any

9. Check if the installation is tested for leakage

10. Check for the provision of sampling points in the temporary circuit

11. Check for the provision of proper supports for the temporary piping

12. Check if the drains , vents if any are routed properly to the nearby drains

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Witness By

Witness By

Name: Signature

Name: Signature

Name: Signature

ANNEXURE 1 FORMAT FOR RECORDING DATA OF UB - CHEMICAL CLEANING

Process Parameter Date Time Cleaning Process Item Value

Chemicals Used

Quantity

Flushing

pH

Total Alkalinity

Oil Content

Grease Content

Temperature

Alkaline Cleaning

Drum Level

pH

Total Iron

Trivalent Iron

Acid Conc.

Instantaneous Velocity

Temperature

Corrosion rate

Acid Cleaning

Inhibitor Efficiency

pH

Iron

Neutralisation

Temperature

pH

Rinses

Conductivity

Final Check Pickling grade


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Witness By

Witness By

Name: Signature

Name: Signature

Name: Signature

Eventual mud presence

pH

Residual Hydrazine

Passivation

Filtration

Conservation Nitrogen Pressure

DATE:


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Page 23of 24 Format No. : L&T/POWER/IOCL/M/CC-UB/3



Witness By

Witness By

ANNEXURE 2 LAY OUT OF CHEMICAL CLEANING CIRCUIT

Name: Signature

Name: Signature

Name: Signature

DATE:


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Page 24 of 24 Format No. : L&T/POWER/IOCL/M/CC-UB/4



Witness By

Witness By

ANNEXURE 3

FINAL PASSIVATION CURVE

Name: Signature

Name: Signature

Name: Signature

ContentsRevision Record SheetSection No.

RecordsActivitySr. No

Remarks1.01234567891011121314151617182.012345673.0 ( a ) ( b ) ( c )( d )( e )3.11233.2123456783.31234567891011121314153.412343.512345678910113.613.7014.0Lay out of Temporary Chemical Cleaning CircuitFinal In service Passivation - Curve

m33-Chemical Cleaning of Utility Boiler

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