draft ii oisd-std-131

Page No. I

S. No.: OISD/DOC/2019/2019/01

OIL INDUSTRY SAFETY DIRECTORATE

बायलर का नर ण ओ आई एस डी–मानक- 131

INSPECTION OF BOILERS

OISD-STANDARD- 131

Prepared by

FUNCTIONAL COMMITTEE ON


FOR RESTRICTED CIRULATION ONLY

OIL INDUSTRY SAFETY DIRECTORATE

Government of India Ministry of Petroleum & Natural Gas

8th Floor, OIDB Bhavan, Plot No. 2, Sector – 73, Noida – 201301 (U.P.) Website: https://www.oisd.gov.in Tele: 0120-2593833, Fax: 0120-2593802

Inception April 1990 Amended Edition August 1999 Revised Edition 2019

Page No. II

Preamble

Indian petroleum industry is the energy lifeline of the nation and its continuous performance is essential for sovereignty and prosperity of the country. As the industry essentially deals with inherently inflammable substances throughout its value chain – upstream, midstream and downstream – Safety is of paramount importance to this industry as only safe performance at all times can ensure optimum ROI of these national assets and resources including sustainability.

While statutory organizations were in place all along to oversee safety aspects of Indian petroleum industry, Oil Industry Safety Directorate (OISD) was set up in 1986 Ministry of Petroleum and Natural Gas, Government of India as a knowledge centre for formulation of constantly updated world-scale standards for design, layout and operation of various equipment, facility and activities involved in this industry. Moreover, OISD was also given responsibility of monitoring implementation status of these standards through safety audits.

In more than three decades of its existence, OISD has developed a rigorous, multi-layer, iterative and participative process of development of standards – starting with research by in-house experts and iterating through seeking & validating inputs from all stake-holders – operators, designers, national level knowledge authorities and public at large – with a feedback loop of constant updation based on ground level experience obtained through audits, incident analysis and environment scanning.

The participative process followed in standard formulation has resulted in excellent level of compliance by the industry culminating in a safer environment in the industry. OISD – except in the Upstream Petroleum Sector – is still a regulatory (and not a statutory) body but that has not affected implementation of the OISD standards. It also goes to prove the old adage that self-regulation is the best regulation. The quality and relevance of OISD standards had been further endorsed by their adoption in various statutory rules of the land.

Petroleum industry in India is significantly globalized at present in terms of technology content requiring its operation to keep pace with the relevant world scale standards & practices. This matches the OISD philosophy of continuous improvement keeping pace with the global developments in its target environment. To this end, OISD keeps track of changes through participation as member in large number of International and national level Knowledge Organizations – both in the field of standard development and implementation & monitoring in addition to updation of internal knowledge base through continuous research and application surveillance, thereby ensuring that this OISD Standard, along with all other extant ones, remains relevant, updated and effective on a real time basis in the applicable areas.

Together we strive to achieve NIL incidents in the entire Hydrocarbon Value Chain. This, besides other issues, calls for total engagement from all levels of the stake holder organizations, which we, at OISD, fervently look forward to.

Jai Hind!!! Executive Director

Oil Industry Safety Directorate

Page No. III

FOREWORD

The Oil Industry in India is over 100 years old. As such, various practices have been in vogue because of collaboration/ association with different foreign companies and governments. Standardization in design philosophies, operating and maintenance practices remained a grey area. This coupled with feedback from some serious accidents that occurred in the past in India and abroad, emphasized the need for the industry to review the existing state-of-the-art in designing, operating and maintaining of Oil and Gas installations.

With this in view, the Ministry of Petroleum and Natural Gas in 1986 constituted a Safety Council assisted by the Oil Industry Safety Directorate (OISD) staffed from within the industry in formulating and implementing a series of self-regulatory measures aimed at removing obsolescence, standardizing and upgrading the existing standards to ensure safe operations. Accordingly, OISD constituted a number of functional committees of experts nominated from the industry to draw up standards and guidelines on various subjects.

The earlier document “Inspection of Boilers” was prepared in April 1990 and has undergone review due to changes in statutory norms (IBR 1950, Boiler Act 1923) and technological advancement in inspection practices. This document is based on the accumulated knowledge and experience of industry members and the various national and international codes and practices, is meant to be used as a supplement and not as a replacement for existing codes standards and manufacture's recommendations.

The figures and annexures used in the document are representative in nature.

We, at OISD, are confident that the provisions of this standard, when implemented in totality, would go a long way in ensuring safe operation of the target group of locations.

Needless to mention, this standard, as always would be reviewed based on field level experience, incident analysis and environment scanning. Suggestions from all stake holders may be forwarded to OISD.

Page No. IV

NOTE

Oil Industry Safety Directorate (OISD) publications are prepared for use in the Oil and Gas industry under Ministry of Petroleum & Natural Gas. These are the property of Ministry of Petroleum & Natural Gas and shall not be reproduced or copied and loaned or exhibited to others without written consent from OISD.

Though every effort has been made to assure the accuracy and reliability of the data contained in these documents, OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use.

These documents are intended only to supplement and not to replace the prevailing statutory requirements of IBR, PESO, DGMS, Factory Inspectorate or any other Government body which must be followed as applicable.

Where ever Acts/ Rules/ Regulation and National/ International Standards are mentioned in the standard, same relates to in-vogue version of such documents. Note1 in superscript indicates the modification/changes/addition based on the amendments approved in the 17th Safety Council meeting held in July, 1999.

Page No. V

2nd COMMITTEE

ON INSPECTION OF BOILERS

List of Members

Name (Shri) Leader

Organization

S K Bagchi

Indian Oil Corporation Limited- Haldia Refinery

Members

Sathyan V Bharat Petroleum Corporation Limited – Kochi Refinery

Narendra Prasad Nayara Energy Limited (formerly Essar Oil )

Kaushik Boral Indian Oil Corporation Limited- Mathura Refinery

Rajesh Chitara Engineers India Limited

Amitabh Singh Hindustan Petroleum Corporation Limited , Mumbai Refinery

Anand Kumar Reliance Industries Limited

Amlan Sharma Numaligarh Refinery Limited

Naseem Akhtar GAIL (India) Limited, Pata

Vishal Fulchand Yadav Mangalore Refinery and Petrochemicals Limited

Member Co-Ordinator

Vivek Prakash Singh

Oil Industry Safety Directorate Noida

In addition to the above, several other experts from the industry contributed in the preparation, review and finalisation of this Recommended Practices.

Page No. VI

1st COMMITTEE

ON INSPECTION OF BOILERS

List of Members

Name (Shri) Organization

Leader Sh. R.K. Sabharwal Indian Oil Corporation Limited

Members Sh.R.H. Vohra Indian Oil Corporation Limited Sh.D.P. Dhall Bharat Petroleum Corporation Limited – Kochi

Refinery Sh.P. Dasgupta Indian Oil Corporation Limited Sh.I.M. Advani Hindustan Petroleum Corporation Limited Sh.V.K. Moorthy Oil & Natural Gas Corporation Limited

Member Co-Ordinator Sh.R.M.N. Marar Oil Industry Safety Directorate Noida

In addition to the above, several other experts from the industry contributed in the preparation, review and finalisation of this Recommended Practices.

Page No. VII

INSPECTION OF BOILERS CONTENTS

Sl no. Details Page No.

1.0 Introduction 1

2.0 Scope 1

3.0 Definitions and types of Boilers 1

3.1 Definition 1

3.2 Types of Boilers 3

4.0 Inspection Role 4

5.0 Inspection Tools 5

6.0 Inspection of Boiler during Fabrication 5

7.0 Inspection of Boilers prior to Erection and Commissioning 7

7.1 Specific Requirements 7

7.1.1 Stream Drum 7

7.1.2 Economiser, Super Heater and Air Heater 7

7.2 Pre-commissioning Activities 8

8.0 Likely Location of Metal Wastage 9

8.1 Stream Drum 9

8.2 Deaerator 11

8.3 Boiler Combustion Chamber & tubes 11

8.4 Economiser 17

8.5 Super heater 18

8.6 Air-Preheater 20

8.7 Wind box and Air Duct 20

8.8 Blowdown Piping/soot Blower Piping 20

8.9 Fuel Gas Duct & Expansion Bellows 20

8.9.1 Co Boiler Duct 20

8.9.2 Fuel Gas Ducts & Bellows 21

8.10 Boiler Feed Pipe Corrosion 21

8.11 Process Waste Heat Boilers 21

9.0 Frequency of Inspection 22

9.1 On-Stream Inspection 22

9.2 Shutdown Inspection 22

9.3 Remnant Life Assessment 22

10.0 Inspection Procedures 23

10.1 On-Stream (Water Tube Boilers) 23

10.1.1 Flame Condition 23

10.1.2 Excess Air 23

Page No. VIII

Sl no. Details Page No.

10.1.3 Condition of Refractory 23

10.1.4 Leaks 23

10.1.5 Hot Spots 23

10.1.6 Ladders, Stairways and Platforms 24

10.1.7 Boiler Feed 24

10.2 On-Stream (Fire Tube Boilers) 24

10.3 Inspection During Shutdown (Water Tube Boilers) 25

10.3.1 External Inspection (Water Tube Boilers) 25

10.3.2 Internal Inspection 26

10.4 Internal Inspection (Fire Tube Boilers) 35

11.0 Waste Heat Boilers 36

12.0 Co-Boilers 37

13.0 Inspection During Repairs and Replacement 38

13.1 Repair/Replacement of Economiser 38

13.2 Drums 38

13.3 Replacement of Fire Box Tubes/ Superheater Tubes 38

14.0 Record and documentation 38

15.0 References 39

Annexure-I 40 (Pre-commissioning checklist of Boilers)

Annexure-II 42 (On stream Inspection of Boilers)

Annexure-III 43 (Shutdown Inspection of Boilers)

Annexure IV 45 (Weekly routine Boiler Inspection Report)

Annexure-V 46 (Useful tests for the control of water for Boilers)

OISD – STD – 131 Page No. 1 INSPECTION OF BOILERS

“OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from the use of OISD Standards/Guidelines.”


1.0 INTRODUCTION Modern steam generators are complex equipment designed with stringent factors of safety. The most reliable method to ensure safety is periodic inspection, monitoring and preventive maintenance carried out to sound engineering standards. The Indian Boiler Regulations, 1950 framed under the Indian Boilers Act 1923 are the comprehensive statutory set of regulations covering the design, fabrication, inspection, testing and certification of Boilers or any Boiler part including feed piping and fittings or vessels attached thereto Boiler components. This standard on “Inspection of Boilers” has been framed keeping in mind salient features of the IBR 1950 and certain best engineering practices prevalent in the Industry. The document in no way supersedes the stipulations prescribed in IBR 1950 which shall be strictly followed for design, fabrication, inspection, testing and certification of Boilers.

2.0 SCOPE This standard covers the minimum inspection requirements for Fired & Unfired Boilers, and Auxiliary Equipment during operation and maintenance. The Standard specifies frequency of Inspection, likely location of metal wastage, areas to be inspected, inspection procedures and inspection during and after repairs. The standard also covers in brief fabrication and precommissioing inspection checks of Boilers. The standard does not cover inspection requirements of Coal Fired Boilers. However, for pressure parts of such Boilers covered under IBR 1950, relevant sections of this standard & IBR 1950 shall be referred.

3.0 DEFINITION AND TYPES OF BOILERS

3.1 DEFINITIONS i) ACT

The Act means Indian Boiler Act, 1923 and as amended from time to time. ii) BOILERS

As per Boiler Act 1923, clause 2 (b), “Boiler” means a pressure vessel in which steam is generated for use external to itself by application of heat which is wholly or partly under pressure when steam is shut off but does not include a pressure vessel, — (i) with capacity less than 25 litres (such capacity being measured from the feed

check valve to the main stream stop valve);

(ii) with less than one kilogram per centimetre square design gauge pressure and working gauge pressure; or



(iii) in which water is heated below one hundred degrees centigrade.

iii) BOILER LAYUP

Any extended period of time during which the Boiler is not expected to operate and suitable protection is made to protect it against corrosion, scaling, pitting etc. on the water and fire side is termed Boiler lay-up.

iv) DESUPERHEATER/ ATTEMPERATOR

The Desuperheater/Attemperator is a type of heat exchanger for controlling the final dry superheated steam temperature.

v) ECONOMISER

“Economiser” means any part of a feed-pipe that is wholly or partly exposed to the action of flue gases for the purpose of recovery of waste heat.

vi) MAXIMUM ALLOWABLE WORKING PRESSURE (MAWP)

The Maximum Allowable working pressure is Maximum the pressure for which the Boiler is designed and constructed.

vii) MAXIMUM WORKING PRESSURE

Maximum Working pressure is the maximum pressure for which Boiler is certified to operate by the Inspecting Authority I.e. Boiler Inspector.

viii) RECUPERATIVE TYPE AIR HEATER

The recuperative type air heater is a tubular type air heater, where hot flue gases are inside the tubes and air on the outside of tubes.

ix) REGENERATIVE TYPE AIR HEATERS

The regenerative type air heater is a rotating heat sponge made up of closely spaced sheets of rotating metal which absorbs heat as it rotates through flue gas compartments and gives up heat as it rotates through air compartments.

x) STEAM CALORIFIERS

Steam calorifiers are tubular type air heaters where turbine bleed steam is inside the tubes and fresh air on the outside of the tubes. It helps in reducing the possibility of cold end condensation.

xi) SUPERHEATERS

“Superheater” means any equipment which is partly or wholly exposed to flue gases for the purpose of raising the temperature of steam beyond the saturation temperature at that pressure and includes a re-heater.



xii) WATER TUBE

A Water Tube is a tube in a Boiler having the water and steam on the inside and heat applied to the outside.

xiii) WIND BOX

A Wind Box is a chamber surrounding a burner, through which air under pressure is supplied for combustion of the fuel.

xiv) WASTE HEAT BOILER (WHB) / HEAT RECOVERY STEAM GENERATOR (HRSG) /

PROCESS STEAM GENERATOR

These Boilers generate steam by transferring heat from high-temperature gaseous products of combustion or products of chemical reaction or other hot process fluids. These Boilers can be of either a fire tube or water tube design. They can also be supplemented by auxiliary firing.

3.2 TYPES OF BOILERS

Boilers can primarily be classified on the basis of the following:

SN Basis of classification Type 1 Mode of Heating a) Fired

b) Unfired 2 Placement of water & heating media a) Fire tube Boiler

b) Water Tube Boiler

i) FIRED BOILERS:

A Boiler in which fuel is burned in a combustion chamber associated with the Boiler. The heat of combustion is absorbed by the Boiler to heat the water and convert it to steam.

ii) UNFIRED BOILERS: A Boiler in which steam is generated by the transfer of heat from gaseous product of combustion, products of chemical reaction or other hot process fluids either inside or outside of the tubes.

iii) FIRE TUBE BOILERS

A Fire Tube Boiler is a Boiler in which steam is generated on the shell side by heat transferred from hot gas/fluid flowing through the tubes. A fire tube Boiler consists of a drum with a tube sheet on each end in which the fire tubes are fastened. Water is contained within the drum surrounding the fire tubes. Fuel is burnt in a combustion chamber associated with the Boiler and arranged in such a manner, that flue gases pass through the inside of the fire tubes to heat the



water surrounding them. These may be either externally fired in which the combustion chamber may be a refractory lined box which is located against one end of the drum or internally fired which may have a steel chamber located within the drum and also surrounded except on one end by the water in the drum.

ii) WATER TUBE BOILER

A Water Tube Boiler is a Boiler having multiple tube circuit within a gas-containing casing, in which steam is generated inside the tubes by heat transferred from a hot gas flowing over the tubes. A Water Tube Boiler consists of one or more (usually from two or four) drums with external banks of tubes connected between the two ends of a single drum or between the drums of multidrum Boilers. In Water Tube Boilers the water is contained within the drums and within the tubes. The fuel is always burnt in an external combustion chamber and flue pass around the outside of the water tubes to heat the water within.

4.0 INSPECTION ROLE

The following are the responsibilities of the inspection division. i) To identify the active and potential damage mechanisms and select proper inspection

techniques for detection of damages, if any & record keeping.

ii) To inspect, measure and record the deterioration of materials and to evaluate the physical condition of the Boiler and its auxiliaries for its soundness to continue in service.

iii) To co-relate the deterioration rate with design life for further run. iv) To determine causes of deterioration and to advise remedial measures. v) To recommend/forecast short term and long term repairs and replacements. vi) To advise regarding components /equipment replacement so that procurement action can

be initiated. vii) To undertake stage-wise inspection of repairs. viii) To maintain upto date maintenance and inspection records and history. ix) To keep the concerned operating and maintenance personnel fully informed as to the

present condition of Boilers.

x) To periodically review the operating parameters impacting corrosion like feed water, blow down water, quality of fuel & flame pattern to enhance the reliability.



In addition to the above, the following shall be maintained by Operation Group:

xi) Constant vigilance on the physical condition and ensuring operating parameters of the Boilers within design limits during operation.

xii) Compliance with IBR statutory norms

5.0 INSPECTION TOOLS

The following inspection tools are generally used for carrying out the inspection of Boiler parts. 1. Ultrasonic Thickness Gauge 2. Ultrasonic Flaw detector 3. Radiography Equipment 4. Infra-red Scanner for Thermography 5. Fiberoscope/ Borescope /Remote visual inspection 6. Dye Penetrant kit 7. Paint Thickness Gauge 8. ID & OD Gauges 9. Inspector’s Hammer 10. Pit Depth Gauge 11. Magnifying Glass 12. Plumb and Bob 13. Magnets 14. Small Mirror 15. Scraper 16. Measuring Tape 17. Safety Torch/Hand Lamp 18. Vacuum-Leak Detector Kit 19. Surveyor’s level 20. Positive Material Identification (PMI) unit 21. Portable Hardness tester 22. Welding gauges 23. Inspection Camera 24. Marker / Crayon 25. Wire brush 26. Magnetic Particle Inspection equipment 27. Advanced NDT techniques like Remote Field Electromagnetic Testing (RFET), Internal Rotary inspection system (IRIS) etc.

6.0 INSPECTION OF BOILER DURING FABRICATION All Boilers are designed and fabricated as per IBR and its other permitted codes like ASME, BS, etc. Inspection of new Boiler at the time of fabrication shall be done as per applicable codes and statutory requirements.

The inspection shall include the following: i) Study of the tender document and all the technical specifications.



ii) Identification and inspection of the material:

Material Test Certificate verification from supplier should be carried out to ensure use of correct materials. Colour coding of different materials should be physically verified before use. 100% PMI check for alloy steel/ Stainless Steel components shall be carried out in three stages (Material at store, during fit-up, before hydro test)

iii) Approval of the welding procedures:

All welding procedures shall be prepared in line with & approved by IBR. Matrix of welding procedures should be prepared for easy reference.

iv) Approval of welder’s performance qualification test: Welding of all pressure parts of Boilers & its auxiliary equipment shall be done by IBR qualified welders only. Detailed guidelines with regard to Qualification Tests for Welders engaged in welding of Boilers and steam-pipes are covered under chapter XIII of IBR 1950.

v) Check for nozzle orientation, joints fit-up and overall dimension as per the approved

drawings. Adequate precautions shall be taken to avoid distortion during welding.

vi) Check to ensure that the welding is carried out as per approved welding sequence and procedures with approved electrodes and qualified welders.

vii) Check for tube expansion data viii) Inspection of refractory material & its application ix) Inspection of the weld joints for proper quality during welding.

x) Approval of the procedure for various types of testing. xi) Checks to ensure proper preheat and post weld heat treatment wherever required. xii) Inspection of weld joints by radiography and other Non-Destructive Testing methods

as specified.

xiii) Inspection of repairs, if any, before giving clearance for hydrostatic testing.

xiv) Hydro test of Boilers after fabrication-: Detailed guidelines with regard to hydraulic test at the fabrication (makers’) works are covered under Regulation 268 of IBR 1950.

xv) Checks to ensure that all the tests are carried out strictly as per approved procedures. xvi) Inspection of painting. xvii) Checks to ensure that the Boiler has been stamped.



xviii) Preparation and certification of the relevant documents.

7.0 INSPECTION OF BOILERS PRIOR TO ERECTION AND COMMISSIONING

Erection and pre-commissioning checks should be carried out for Boiler and other auxiliary equipment as per attached checklist (Annexure-I)

7.1 SPECIFIC REQUIREMENTS

In addition to above, some specific requirements for each Boiler part as given under shall be fulfilled before commissioning. 7.1.1 Steam Drum i) That the steam separators are free from deposits. ii) That all the wooden plugs have been removed from tube ends. iii) That the drum is free to expand in all the required directions. iv) That the water level gauge and water level instruments connections have been installed

as per approved drawings. v) That drum pressure gauges have been checked for calibration and functioning. 7.1.2 Economiser, Super Heater & Air Heater i) Inspection of economiser, superheater and air heater for transverse and longitudinal

spacing. Any misalignment shall be corrected. ii) Inspection for proper supports, expansion clearances, vibration in the scrubbers, gas

baffles etc. iii) Inspection for the proper position of for the soot blower nozzles in relation to the tubes for

avoiding scouring of tubes by impingement during operation. iv) Inspection of the thermocouple point for correct location, installation, continuity and

response. v) Inspection to ensure that safety valve vent pipes have been properly laid & supported as

per approved drawing



7.2 PRECOMMISSIONING ACTIVITIES

The following test and activities shall be carried out in addition to the normal start-up activities before Boiler is made ready for operation. a) Air & Gas Tightness Tests The fire box and the ducting system shall be checked for leak tightness before applying insulation, painting or cladding etc. The dampers, access doors, observation ports and other openings shall be secured. Pressurised unit shall be subjected to pressure decay test of the Boiler in addition to tightness test. Decay testing should be carried out at 1.5 times the maximum operating pressure. Air and gas tightness tests can be carried out by running the forced draft fan and maintaining a pressure of 50 mm of water column in the ducting under test. Leaky portion shall be rectified and test shall be repeated to ensure satisfactory leak tightness of the system. b) Chemical cleaning & Passivation Before a new Boiler is put into service, the internal surface of steam generating section shall be chemically cleaned. This process includes boil out to remove grease followed by an acid cleaning to remove mill scales and rust. During the boil out & chemical cleaning period solution samples shall be taken periodically to monitor alkalinity, pH, Fe, silica and oil content. Complete draining of residue chemical shall be ensured after chemical cleaning activities. This operation is intended to remove mill scales, welding slag, debris or other foreign materials left over in the super heater, preheater and steam piping of Boiler & forming a protective layer through passivation. In case there is a gap between Mechanical Completion & Commissioning, preservation of Boiler shall be done as per applicable stipulations for preservation of idle Boilers laid in OISD- STD-171. c) Safety Valve Setting At the end of steam blowing, all the safety valves in the Boiler shall be floated to operate at their respective set pressures. For details OISD- STD-132 on Pressure Relieving Devices shall be referred. d) Testing of Protections and Inter Locks All the interlocks and protections provided for the individual equipments shall be inspected and made functional before putting them into service.



8.0 LIKELY LOCATION OF METAL WASTAGE

8.1 STEAM & MUD DRUM The corrosion of Boiler drums is greatly dependent on the quality of water inside the drums. The most common damage mechanisms prevalent in Boiler drums includes localized corrosion and pitting of the drum internal surface, hydrogen damage, caustic corrosion, mechanical deterioration, corrosion fatigue and external corrosion under insulation. The internal metal loss due to corrosion and oxidation largely depends on the water chemistry used in the Boiler. Improper preservation during Boiler outages may aggravate the internal corrosion. The accumulation of deposit and muck also attribute to internal corrosion. During operation of steam Boiler, undesirable gases like oxygen, hydrogen and carbon dioxide gases may evolve. Carbon dioxide with water in Boiler forms carbonic acid. Thus acidity is increased and pH value decreases. Hydrogen induced corrosion damage can also take place if the Boiler is operated with water having low pH. If pH value of water is raised to 9.4 hydrogen evolution ceases and a protective film is formed over the anodic area. But presence of oxygen retards the above action. Hence, it is important to remove even the traces of oxygen from water so as to maintain Oxygen level within acceptable limits. Due to poor performance of deaerator, dissolved oxygen in feed water causes the pitting internally. Caustic corrosion can take place due to deposition of corrosion products with high caustic concentration leading to localized region of high pH. At high pH levels, the protective oxide layer of metal surface disintegrates leading to rapid corrosion. Deposits are likely to occur at points where the circulation of water is poor, thereby increasing the vulnerability to internal corrosion. Some of the effective mitigation measures for internal corrosion damage are:

By maintaining the Boiler water chemistry within the desired range, By Proper tightening of drum internals, By Minimizing the ingress of deposit forming materials with the feed water and By performing periodic cleaning.

Fig # 1 & 2: Deposit inside Boiler drum indicating poor water chemistry of drum water



Cracks along the longitudinal weld seams may occur if the material is highly stressed. Mechanical deterioration of drums can result from abnormal stresses created by frequent changes in temperature and pressure. Thermal Fatigue can also result due to expansion and contraction caused by temperature fluctuations during operation. If corrosion acts concurrent to fatigue, the fatigue resistance of the metal is reduced and corrosion-fatigue cracks may initiate. Cyclic operation can also lead to drum distortion and can result in concentrated stresses at the major support welds and seam welds. Minor leakages in tube expansion joints of the drum can also result in ligament cracking. External surfaces of drum & small bore tapings are likely to corrode due to wetting of insulation or improper insulation. The summary of major damage mechanisms common to Boiler drums and the prevention methods is given below:

Damage mechanism Major root cause Precautions to avoid failure

Internal corrosion including pitting, localized corrosion, caustic gauging and hydrogen damage

Improper water chemistry

1) Review and monitoring of water chemistry logs

2) pH monitoring, especially during start-ups and shutdowns

Internal tube deposits

1) Strict control of dosing parameters

2) Periodic tube sampling for monitoring of internal deposits

3) Review of chemical cleaning procedures to avoid aggressive of improper chemical cleaning

4) Periodic checking for condenser tube leakages

Idle time corrosion

1) Shutdown and idle time preservation to be as per recommended procedures

Cracking and mechanical deformation

Stresses due to changes in temperature and pressure

1) Review operating procedures to reduce thermal strains

2) Strict adherence to standard start-up and shutdown procedures

External corrosion Corrosion under insulation

1) Maintaining proper insulation to avoid water ingress



8.2 DEAERATORS Deaerators are used to heat feedwater and reduce oxygen and other dissolved gases to acceptable levels. Corrosion fatigue at or near welds is a major problem in deaerators. Most corrosion fatigue cracking has been reported to be the result of mechanical factors, such as manufacturing procedures, poor welds, and lack of stress-relieved welds. Operational problems such as water/steam hammer can also be a factor. Other forms of corrosive attack in deaerators include stress corrosion cracking of Stainless steel tray chamber, inlet spray valve spring cracking, corrosion of vent condensers due to oxygen pitting, and erosion of the impingement baffles near the steam inlet connection. External surface of shell & tapings is typically corroded due to wetting of insulation or improper insulation. Control of dissolved oxygen & pH in feed water, maintenance of stable temperature and pressure levels, regular out of service inspection using NDT are the effective mitigation measures. 8.3 BOILER COMBUSTION CHAMBER & TUBES Bulging in tubes are caused primarily due to overheating due to flame impingement or starvation. If there is hard firing, the flame is likely to touch the furnace wall unevenly. Overheating is generally caused by increased steam and metal temperatures due to inadequate medium flow through the tubes or higher than designed heat transfer which subsequently causes blistering, quench cracking, sagging or bowing of tubes. Boiler tubes exposed to extremely high temperatures for short duration can result in longitudinal thin-lipped fish-mouthed rupture. Such short term overheating is generally caused by low drum levels or by another failure adjacent to the location. Normally, the short-term overheating failures result in considerable bulging, metal elongation, and reduction of wall thickness. Often, the suddenness of the rupture bends the tube. Exposure of tube for longer duration at very high temperatures may result to a thick-lipped failure. A thick lipped rupture can result due to departure from normal nucleate boiling or due to internal deposition in the tubes.

Fig # 3: Thin-lipped rupture due to overheating



Fig # 4: Bowing of ruptured tube

Internal corrosion in the tubes is caused by poor maintenance of water quality and the damage mechanisms are similar to that of drums which include localized corrosion and pitting of the tube internal surface, hydrogen damage and caustic gouging.

Fig # 5: Internal deposits inside bank tube Hydrogen damage is most commonly associated with excessive deposition on ID tube surfaces, coupled with low pH of Boiler water. During upset in water chemistry like in case condenser leaks, acidic (low pH) contaminants can get concentrated in the inner side deposits. Under-deposit corrosion releases atomic hydrogen, which migrates into the tube wall metal, reacts with carbon in the steel forming pockets of Methane gas and causes inter-granular separation. At low temperature, such phenomenon can happen due to formation of H2 (Hydrogen Gas) caused by poor control of process during Boiler chemical cleaning and/or inadequate post-cleaning passivation leaving behind residual acid for a long period of time.



Fig # 6: Failure due to hydrogen damage

Caustic cracking requires high temperature, a high concentration of alkali and tensile stresses. The free caustic accumulates in areas of high heat flux or beneath any existing scale. Caustic concentrates leads to breakdown of Fe3O4 film and accelerated corrosion, which in turn further increases internal skin temperature.

Fig # 7: Caustic gauging inside tube

External corrosion of fire box tubes generally depends on the fuel constituents and the temperatures of the flue gas and the tube. The external corrosion can be either low temperature attack or high temperature corrosion. External corrosion is generally caused by moisture which accumulates on sulphur deposit, and flue gas condensation. This gives rise to external pitting and grooving in the outer wall tubes and mud drum at flue gas passage.



The low temperature external corrosion occurs when flue gas bearing sulphur compounds cool down to dew point temperature. Low temperature corrosion is the result of SO3 and water vapour in the flue gas combining to form sulphuric acid and condenses when temperatures fall below the acid dew point. Vanadium plays a role of catalyst in converting SO2 to SO3. The external corrosion is more predominant if the Boiler is kept out of service for long period.

Fig # 8: External corrosion at header

Fig # 9: External corrosion due to flue gas

The high temperature external corrosion of Boiler tubes can result due to deposition of combustion products of fuel containing vanadium and sodium. In the presence of oxygen, the free sodium in fuel initially combines to form sodium oxide (Na2O) and then sodium sulphate (Na2SO4). At the same time vanadium oxidizes to form vanadium pentoxide (V2O5). Depending on the relative concentration of sodium and vanadium, an entire series of complex eutectic vanadates compounds of generally low melting points form at the elevated temperatures. These complexes are extremely corrosive. The portion of the tubes covered under refractory or insulation are more prone to external corrosion.



When flue gas and refractory are in contact at a moderately high temperature, a fluxing action may occur and produce a slag. The general effect on this slagging action is to decrease the insulating effect of the refractory and so allow high metal temperature on the supporting steel parts. The slagging effects of vanadium and sodium oxides may also cause rapid deterioration of tubes, tube hangers and spacers.

Fig # 10: Corrosion under refractory

Sample testing of Fuel being fired should be done periodically to check for Calorific value, Hydrogen, Vanadium & Sulphur content. The summary of major damage mechanisms common to Boiler bank and water wall tubes and the prevention methods is given below:

Damage mechanism Major root cause Precautions to avoid failure Thin lipped tube rupture due to short term overheating

Fire side abnormalities 1) Preventing flame impingement on tubes by burner adjustment

2) Addressing combustion and fuel issues immediately

Starvation 1) Review of trip logic to eliminate chance of low drum level


3) Effective fire box monitoring to avoid localized high heat flux

4) Elimination of chances of flow disruption

Thick lipped tube rupture due to creep/ long term overheating

Departure from Nucleate Boiling

1) Effective fire box monitoring to avoid localized high heat flux

2) Periodic tube sampling for internal oxide scale measurement

Tube internal deposits 1) Monitoring of Boiler water parameters




Phosphate hide out 1) Optimize Boiler water treatment

Internal corrosion including pitting, localized corrosion, caustic gouging , hydrogen damage and thermal fatigue

Improper water chemistry 1) Review and monitoring of water chemistry logs

2) pH monitoring, especially during start-ups and shutdowns

Internal tube deposits 1) Strict control of dosing parameters


3) Review of chemical cleaning procedures to avoid aggressive of improper chemical cleaning

4) Periodic checking for condenser tube leakages

Caustic gouging 1) Avoiding localized high heat flux due to flame impingement, burner misalignment etc.

2) Strict control of dosing parameters

Hydrogen embrittlement 1) Strict monitoring of pH and water chemistry

2) Review of chemical cleaning and preservation procedures

Idle time corrosion 1) Shutdown and idle time preservation to be as per recommended procedures

External corrosion High temperature external corrosion

1) Proper monitoring of fuel composition

2) Periodic inspection of refractory

Low temperature external corrosion

1) Proper monitoring of temperatures and operating conditions

2) Proper monitoring of fuel composition and characteristics

Erosion 1) Ensure proper maintenance of soot blowers

2) Ensure proper operation of soot blowers. Draining of soot blower headers to be ensured.



8.4 ECONOMISER External corrosion in the low temperature regions of economiser may occur due to flue gases cooling down to the dew point temperature. External erosion may be caused by high velocity steam from Soot blower. External deterioration may occur due to water impingement when adjacent tube fails Internal corrosion is caused due to dissolved oxygen in feed water and thinning may take place at the bends due to erosion. Close control over Boiler water chemistry and monitoring practices are important factors for prevention of oxygen induced corrosion. The summary of major damage mechanisms common to economiser tubes and the prevention methods is given below:

Damage mechanism Major root cause Precautions to avoid failure External corrosion Dew point corrosion 1) Proper monitoring of

temperatures and operating conditions

2) Proper monitoring of fuel composition and characteristics

Erosion 1) Ensure proper maintenance of soot blowers

2) Ensure proper operation of soot blowers. Draining of soot blower headers to be ensured.

Internal corrosion Pitting corrosion 1) Residual hydrazine in Boiler feed water to be strictly monitored

Flow accelerated corrosion 1) Regular health monitoring of headers, stubs, bends and other areas having turbulent flow

2) Proper monitoring of pH, velocity; design review if problem persists



Fig # 11& 12: External corrosion of economiser coils due to deposit

Fig # 13: Internal corrosion due to oxygen

8.5 SUPERHEATER Superheater tubes can rupture if deposits accumulate in them. The cause of accumulation must be investigated and corrected. Excessive height of water maintained in the drum or deposits accumulated on steam separators may cause carry over & deposits on Super Heater Tubes. Further Such Water carry over may also cause hammering of superheater tubes and subsequent superheater tube failures. Warping of superheater elements is an indication of overheating too rapidly or failure to open the drain when raising pressure. Overheating of super heater tubes is likely if steam is interrupted. Oxygen pitting, particularly in the pendant loop area, is another major corrosion problem in superheaters. It is caused when water is exposed to oxygen during downtime. Nitrogen blanket and chemical oxygen scavenger can be used to maintain oxygen free conditions during downtime.



Fig # 14: Rupture of SH tube due to overheating

Fig # 15: Oxidation of SH tube

Fig # 16: Bulged SH tube: internal surface showing thick deposition



8.6 AIR-PREHEATER Due to poor combustion, especially during start up or shut down, oil carry over and deposition occur in the air heaters. These deposits have to be cleaned by soot blowing or by water washing during shutdown: otherwise under conductive conditions, they will catch fire and lead to a major failure of air heater tubes. Low temperature corrosion of the cold end is a common problem with unit operating on fuel with high sulphur content. The life of cold end tubes can be prolonged by maintaining the cold end metal temperature above the acid dew point.

Fig # 17: Perforated APH tubes

8.7 WIND BOX AND AIR DUCT These are subjected to corrosion caused by condensation of moisture during extended down time. External corrosion can take place due to improper insulation. 8.8 BLOWDOWN PIPING/ SOOT BLOWER PIPING These piping are susceptible to erosion at the sharp bends. Intermittent blowdown piping are more prone to corrosion than continuous blowdown piping. Corrosion under insulation can take place due to improper insulation & cyclic service. 8.9 FLUE GAS DUCT & EXPANSION BELLOWS 8.9.1 CO Boiler Duct The corrosion of bellows in CO duct and by pass ducts usually takes place due to deposition of chlorides present in condensate along with refractory. Concentration of chlorides cause stress corrosion cracking in S.S bellow-convolutions. Up gradation of bellow material & design including double ply may be considered.



8.9.2 Flue Gas Ducts & bellows: The corrosion usually take place due to condensation of sulphurous flue gases primarily in downstream section of air pre heater to stack including bellows. The external corrosion can also take place due to wet insulation. 8.10 BOILER FEED PIPE CORROSION In presence of higher oxygen content in feed water, pitting may occur on the inner surface of feed pipe. Corrosion may also occur at the tapping of pressure gauges, drain, sampling points etc. External corrosion can take place due to improper insulation. 8.11 PROCESS WASTE HEAT BOILERS The water chemistry plays an important role in controlling the internal corrosion of drums and tubes of process Waste Heat Boilers (WHBs). Improper burning at combustion chamber can lead to damage of refractory and ferrules leading to high temperature corrosion of tubes. Low temperature corrosion can also occur during idle time if proper preservation procedure is not followed. The CO Boiler tubes are also subject to localized erosion due to catalyst and acidic corrosion due to flue gases.

Fig # 18: Damaged ferrules of WHB leading to overheating



Fig # 19: High temperature sulphur corrosion of tubes

9.0 FREQUENCY OF INSPECTION 9.1 ‘ON STREAM’ INSPECTION

‘On stream’ inspection of Boilers shall be carried out daily by Operation Deptt and once a week by Inspection Deptt to monitor flame pattern and determine conditions of fire box Further, detailed ‘On Stream’ inspection should be carried out once in 06 months preferably. Standard checklist for On Stream Inspection is attached as Annexure-II.

9.2 SHUTDOWN INSPECTION

The period between two consecutive inspections of Boilers shall be as per regulation 376 of Indian Boiler Regulations 1950 & subsequent amendments thereof. Standard checklist for shutdown inspection is attached as Annexure-III.

9.3 REMNANT LIFE ASSESMENT Due to Ageing of Boilers, Remnant Life assessment (RLA) of Boilers shall be done in line with IBR regulation 391A through agencies approved and authorised by IBR. The RLA study involve in general but not limited to:

1) Non-destructive tests like Ultrasonic Testing (UT), Liquid Penetrant Testing (LPT), Magnetic Particle Testing (MPT) of various metallic components of the Boiler such as tubes, drum, headers, weldments, safety valves, hanger supports etc.

2) Internal visual examination of the deposits /scales on a few tubes. About a meter-long sections in the super heater areas to be cut to examine the internal deposits, condition etc. These tubes are replaced as the cut specimen is subjected to destructive tests like tensile, impact test etc.

3) Hardness and thickness measurement of tubes and headers.



4) Measurement of diameters and checking for ovality if any on the headers.

5) Measurement of oxide scale thickness on inside surface of the super heater tubes.

6) Metallographic examination of spots on tubes and headers on parent, weld and HAZ (Heat Affected Zone) area to ascertain current metallographic structure of the material.

7) Internal visual examination of headers.

For more details, Regulation 391A of IBR 1950 shall be referred.

10.0 INSPECTION PROCEDURES 10.1 ON-STREAM (WATER TUBE BOILERS) Inspection of Boilers and Boiler parts shall be done while the Boiler is on stream to increase their safety 10.1.1 Flame Condition The condition of the flame should be checked through the peep holes using colour glasses. The flame should be neutral and shall not impinge on the furnace wall tubes if there is any tendency of the flame to impinge on the furnace tubes and refractory, corrective measures shall be taken at the earliest. 10.1.2 Excess Air The amount of excess air shall be checked. Inadequate excess air can cause insufficient combustion and the unburnt hydrocarbon may explode later. On the other hand, too much of excess air can abet low temperature sulphur corrosion. 10.1.3 Condition of Refractory The furnace shall be inspected for fallen refractory evidence of corrosion of side walls, back wall and flame cutting of burner throats. 10.1.4 Leaks Leaks from Boiler drums, fittings, headers and other pressure parts shall be checked during operation. Soaked insulation is the first indication about presence of leaks. High temperature high pressure super heater steam leaks should be examined carefully as they are not readily visible. A moderate to large leak can be detected by sound of escaping steam. 10.1.5 Hot spots Inspection shall be made for hot spots, blistered paint and corrosion on exterior plates which could be indications of refractory insulation failure. Thermography to detect hot spots in



Boilers and stack shall be done at least once in three months to monitor the internal lining / refractory condition.

10.1.6 Ladders, Stairways and Platforms Ladders, stairways, platforms and walkways shall be inspected visually for corrosion, cracked welding, mechanical damage or any other deterioration which may cause structural weakness. Light hammer testing should be done to locate the weakest locations. Platforms and walkways should be inspected for any skidding surface like oil, grease etc. 10.1.7 Boiler Feed Analysis of Boiler feed water and blow down water shall be carried out periodically in line with the stipulations laid down in chapter XV of the Indian Boiler Regulations 1950. These tests should be carried out weekly. For reference, a sample checklist of Weekly Routine Boiler Inspection Report and Useful tests for the control of water for Boilers are attached as Annexure IV & V 10.2 ON-STREAM (FIRE TUBE BOILERS) (a) While the Boiler is in operation the condition of the flame should be checked through the

view glass provided at the rear and front end to ensure proper tuning of air-fuel ratio. (b) Flue gas exit temperature should be monitored closely. (c) Leaks from Boiler shell, gauge glasses, fittings and mountings should be checked during

operation. (d) Fuel gas lines should be checked for any leakages from flanges, valves and fittings using

gas detectors. (e) The front reversal chamber and the rear inspection window should be inspected for any

hot gas leaks. (f) The back of the Boiler should be checked for any hot spots visually or by using

thermography. (g) The air cooled view glasses at the rear end should be checked to ensure proper cooling. (h) The linkage position of the dampers provided in the flue gas exit duct should be checked

to ensure that the dampers are in open position. (i) The Boiler and the forced draft air blowers should be checked for any abnormal noise and

vibrations. (j) Stair cases, platforms and walk ways should be checked for corrosion and cracks in

welding.

(k) Condition of insulation shall be checked for Corrosion under insulation (CUI) & mitigation methods shall be undertaken.



10.3 INSPECTION DURING SHUTDOWN: (WATER TUBE BOILERS) 10.3.1 External Inspection Visual inspection is carried out to check for corrosion, structural weakness, foundation, strained piping, damaged insulation and refractory. (a) Foundations Foundations settlement may cause equipment failure, refractory failure, steam leaks etc. This settlement can be detected by cracks in the concrete and brick walls and adjacent flooring. Differential settlement of Boiler should be checked. Tools such as level, a straight edge etc. may be helpful in determining the amount and seriousness of settlement or cracking. Tapping with a hammer will reveal deteriorated or unsound condition of the concrete level marks put during erection can be used for checking settlement in foundation. (b) Boiler Supports Supports and structures shall be inspected for excessive deflections, swaying, peeling of paints and chippings of mill scale. These are the indications of over loading Structural members shall be inspected for atmospheric corrosion. Boiler supports from overhead by tension members should be hammer tested lightly to check their condition. Tension members under load will be tight and have a clear ring when hit with a hammer. The ones which are not loaded will be loose and will give dull and ‘tinny’ sound when struck. Condition of fire proofing shall be checked & corrective actions shall be taken, if necessary. (c) Steam Drum Spot examinations of drum external surface should be made during shutdown for evidence of external corrosion and for any leaks etc. For all small bore connections, 100% visual inspection and other suitable NDTs should be done. (d) Combustion Chamber The fire side of combustion chamber walls is generally constructed of castable refractory, refractory bricks ceramic fibres etc. The life of refractory, depends on fuel fired, intensity of firing and condition of operation. Alternate heating and cooling tends to open up joints and induce cracking. Failure of brick wall and arches may cause over heating which is indicated by warpage, discoloration or excessive high surface temperature. Access doors, peepholes, or other castings at openings shall be inspected for cracks and sealed tightly. Hinge pins and latches shall be examined for wear and proper operability. Externally, inspection shall be made for hot spots, blistered paint etc. on the exterior plates or casing. These are indication of refractory or insulation failures. (e) Expansion Bellows The expansion bellows shall be inspected for damage of insulation, corrosion and cracking which may occur under the insulation. Ultrasonic thickness measurement, light hammer testing and DP testing should be done as applicable to locate the weakest and corroded area. Testing of expansion bellows should be done as per manufacturer’s recommendations.



Complete visual inspection of fabric bellows shall be done. Servicing of fabric bellows should be done based on conditions. If the bellows are being subjected to Hydro test then prior to Hydro test, it shall be locked & after Hydro testing, it shall be unlocked. (f) Piping Connections A visual inspection of piping is sufficient to disclose any leak at piping connection. Initial indication of a leak will be water dripping out of insulation. All drain nozzles shall be inspected. Piping, if not drained properly, may be subjected to water hammer. This water hammer imposes severe shock loads on the pipe, pipe connection and pipe supports. Pipe, where condensate can accumulate and cause water hammer shall be carefully examined. Visual inspection of pipe supports and hangers shall be done. Thickness survey and hammer testing of the insulated piping like feed water, steam piping soot blower piping and other blowdown piping shall be done after the removal of insulation. Guidelines given in the OISD Standard-130 (Inspection of piping) shall be followed for inspection of piping. If pipes are embedded in masonry or concrete, there shall be exposed for inspection for evidence of external corrosion. Inspection of blowdown piping shall be done at an interval of 5 years by removing the complete external insulation. 10.3.2 Internal Inspection Internal inspection of Boiler and its auxiliary equipment should be done before and after cleaning. If oil is found in any part of the Boiler, the source for this leakage should be identified for necessary rectification. (a) Economiser The economiser tubes external surface, tube supports, spacers and tube protectors shall be inspected during shutdown after cleaning. All accessible tubes of economiser shall be inspected for: i) Nature of scale deposit and soot deposits. Under the deposit any corrosion, erosion,

pitting or any deterioration shall be noted. ii) External metal loss due to steam and water impingement during any leak or due to

impingement of high pressure steam from soot blowers. iii) Displacement /deterioration of tube space and tube supports. iv) Thickness wherever possible. sample of tube if accessible should be taken from

economiser coils after 10 years and subsequently after 5 years and split into two halves for assessing the extent of internal pitting/ deterioration.

External cleanliness of economiser tubes shall be checked. Economiser hopper shall be inspected for erosion and corrosion.



(b) Drums, Drum connections and its internals: i) All the internal parts like steam scrubber, cyclone, separators etc. shall be removed and

Boiler drum shall be visually inspected before and after cleaning. ii) Nature of scale and type of pitting beneath the scale or any deterioration shall be noted. iii) All the nozzles, like safety valves, emergency blowdown, gauge glass connections and

especially the lower connections shall be inspected for accumulation of sludge or foreign material. Edge thinning or any deterioration of the drum shell to nozzle welding shall be inspected carefully.

iv) All the weld seams and the areas adjacent, shall be inspected for cracks/deterioration.

Corrosion along or immediately adjacent to a seam is more serious than same magnitude of corrosion in the solid plate away from seam. Grooving and cracks along longitudinal seams are likely to occur when material is highly stressed.

v) Severe corrosion is likely to occur at points where the circulation of water is poor. Such points shall be inspected.

vi) Manhole and hand holes cover plates and their seating surface shall be inspected for

cracks, warping or any abnormalities. vii) The upper half portion of drum (in steam space) shall be inspected carefully for sign of oil

or similar deposits and cause shall be investigated. viii) Drum internals, such as internal feed pipes, steam separators, dry pipes, blowdown pipes,

deflector plates, steam scrubber and its clamps shall be inspected for tightness, soundness and structural stability. Vigorous turbulence of steam and water present in drum can vibrate such parts and welds may crack.

ix) The chemical dosing pipe and its distributor piping shall be inspected for scaling, pitting or

chock age of holes with sludge.

x) Remote Visual Inspection should be used while inspecting the internal condition of tube connected to drum for erosion/corrosion and deposits, if any.

xi) Thickness survey of the drum shell and its heads shall be carried out with help of

ultrasonic thickness measurement instrument. Dye Penetrant Test (DPT), Magnetic particle inspection (MPI) & Ultrasonic flaw detection should be done for all the longitudinal and circumferential weld joints.

xii) Any welding inside the drum having visible defects shall be removed by grinding and shall

be carefully inspected for cracks and defects.

(c) Water Headers/Mud Drums The water headers are susceptible to heavy deposits build up. In the event of considerable deposit build up, the flow may be restricted thus causing overheating. Inspection shall be carried out as specified below.



i) Visual inspection of all the water headers shall be done after removing the header caps. ii) All hand holes and their cover seats shall be inspected for erosion, corrosion and cracks.

Steam cutting marks or any other abnormal condition which might permit leakage shall be inspect.

iii) Leaky header caps shall be inspected for trueness and possible deformation. iv) Internal surface of headers shall be inspected for scale deposits, pits or any deterioration.

Whenever practicable Remote Visual Inspection should be used. v) External inspection of the header shall be done after the removal of insulation. Particular

attention should be paid to the points, where tubes enter the header for indications of leakage from the tube roll.

vi) The header surface adjacent to the tube roll and hand holes shall be inspected for cracks. vii) Thickness survey of all the headers shall be done. viii) All the headers should be insulated properly after the hydraulic test to avoid thermal

stresses. In the Boilers, where entry inside the mud drum is possible, the inspection of the same shall be carried out as per procedure given in paragraphs 10.3.2. (b) for the inspection of Boiler drum.

d) Out of Drum Cyclones These shall be inspected for wetting of insulation. Whenever insulation is found wet, it shall be removed and examined for any corrosion or erosion. Ultrasonic thickness measurement of the shell and both heads shall be done after the removal of insulation. Cyclones connected to steam and water pipes shall be inspected and hammer tested for any defect thinning and corrosion. Remote visual inspection may be utilised for assessing the integrity of internals as well as internal pitting of the cyclone shell through the mud cleaning hand holes. e) Combustion Chamber: 1) Refractory Linings i) The refractory lining shall be inspected for cracks, erosion, melting, bulging and fall out. A

thin knife or scraper blade may be used to know the depth of the cracking ii) Inspection of furnace roof refractory shall be done for any leakage and deterioration. iii) Ignitory horns shall be inspected for erosion, cracks or any other deterioration.

2) Burners i) Burner tips and defusers shall be inspected for evidence of cracking and enlargement of

holes. ii) Burner throat refractory shall be inspected for cracks, erosion and fusion.



iii) Condition of the air regulating vanes shall be checked for any deterioration. iv) The burner gun shall be checked for alignment and any other physical abnormalities.

For detailed inspection of burners, guidelines of OEM shall be referred. f) Downcomer Tubes The downcomer tubes shall be inspected for any deterioration once in eight years after exposing them. The downcomer tube adjacent to burner throat of Boiler shall be checked for any damage due to contact with high temperature casing plate of burner throat. In case burner throat refractory and refractory supporting rings are found to be damaged, then the downcomer tube adjacent to burner throat shall be exposed for inspection. Thickness survey and light hammer testing shall be done while the downcomer tubes have been exposed. These shall be inspected for bulging also. A tube sample should be taken from the downcomer tube once in eight years for assessing the extent of internal pitting, scaling or any corrosion. g) Water Wall Tubes: The most common and frequent source of trouble is tube leakage, due to ruptures. Hence tubes shall be inspected as specified below: i) All the fire box tubes shall be visually inspected after external cleaning. ii) All the tubes shall be inspected for sign of overheating, flame impingement, bulging,

bowing, corrosion and erosion. Usually overheating is caused by deposits or excessive scale in the water side of the tube. The water wall tubes and generating tubes at the burner level are particularly susceptible to overheating and shall be closely examined for bulging, blistering, bowing, cracking or other deterioration.

iii) Water wall tubes shall be gauged for determining the bulging. The bulged tube beyond

5% of O.D. should be replaced. Callipers, micrometres, pit gauge and ultrasonic instruments can be used to measure tube diameter, dimensions of bulges and depth of corrosion pits.

iv) The loose bent tubes shall be checked visually under strong illumination. No tube should

touch the adjacent tubes. All the loose tubes should be properly aligned by the help of hanger supports/rectification or replacement of hanger supports.

v) External corrosion, pitting and grooving shall be closely checked. Depth of corrosion pits

should be measured and severely pitted tubes should be replaced partially or fully as required. Measuring the depth of corrosion pits must not be neglected as the tube thickness is generally low and may lead to failure.



vi) Particular attention shall be paid to the tubes at the drum level or tube close to refractory near the drum level for metal wastage, grooving and pitting. Corroded tubes, if needed, should be replaced partially or completely.

vii) If a portion of the tube is embedded in the refractory, there is likelihood of external

corrosion of tubes at such location. Such portion shall be examined at least once in eight years at random after removing the refractory.

viii) The hanger supports shall be inspected for oxidation, breakages and dislocation. ix) Tubes at salient locations like burner levels shall be checked for thickness by means of

ultrasonic thickness measurement instrument to establish corrosion rates. Thorough scanning should be done preferably at burner levels.

x) A few water tubes, selected at random shall be radiographed in the region of bends at

lowest elevation to examine the internal condition of tubes for choking and deposition, if any. To assess the internal condition of the water wall tubes, a sample should be taken once in eight years and split into two halves for evidence of pitting, scaling and grooving etc. The sample can also be utilised for checking the creep effect when the Boiler tube life has reached close to design life.

xi) Remote visual inspection should be done for checking the internal conditions of tubes. In

case of doubt, a few tubes may be removed and pieces cut longitudinally and circumferentially to measure their thickness.

xii) Tube should be replaced when tubes have sagged or hogged more than half the tube bore. Presence of sagged or hogged tube indicates the possibility of cracking between the header and the tubes or stub joints.

xiii) The projected and bell mounted tube ends shall be inspected for corrosion.

xiv) Use of advanced NDT methods like Remote Field Electromagnetic Test (RFET), Internal

Rotary Inspection System (IRIS) for Boiler bank tubes, Electro-Magnetic Acoustic Transducer (EMAT) thickness scanning for water wall tube should be done as & when required.

h) Super Heater Headers Except as indicated hereafter superheater headers shall be inspected in a manner similar to that of water wall headers. However, the following additional points shall be considered. i) Thickness survey of the headers and its connected stubs shall be examined by

radiography /Ultrasonic method for loss of thickness or inside pitting, corrosion etc.

ii) External condition of the headers shall be checked for corrosion and pitting due to wetting of insulation.

iii) Weld joints of tubes to headers shall be inspected for cracks or any other deterioration.



i) Super Heater Coils: Visual inspection of all the stages of super heater coils shall be carried out as mentioned below: i) Nature of external scale deposited, type of pitting, corrosion under the deposit due to high

temperature of flue gas shall be checked. ii) Super heater coil near the roof refractory wall shall be closely inspected for any external

corrosion and pitting. iii) The coil shall be checked for evidence of any external dent or abrasion marks, bowing

and bulging etc. iv) All super heater element hangers and spacer shall be inspected for burning and damage. v) For internal inspection, a sample from the super heater coil should be taken and split into

two halves for assessing the internal condition once in 8 years. vi) Local attack in super heater tube may result from carryover of droplets of Boiler water and

concentration of strong alkalis on the metal surface particularly at bottom, bends. These bends should be inspected by means of radiography, if accessible.

vii) Thickness measurements at the bends and at selected locations may be carried out by

ultrasonic thickness for assessing the present thickness and corrosion rate. If the thickness measurement is not possible, radiography should be done.

viii) Internal inspection of the bend of assessing the internal condition, pitting erosion, thinning

etc. can be done by taking radiographs.

ix) OD measurement & Metallography should be done for assessing the extent of creep damage.

j) Indirect Contact Type Desuperheaters: Thorough inspection of the coils and Desuperheaters shell shall be done after pulling out the tube bundles. i) Tubes bundles external surface shall be inspected for corrosion, pitting or any mark of

steam impingement on tubes. ii) Tube ‘U’ bends shall be inspected for cracks due to thermal fatigue caused by steam and

water. iii) All the tubes weld joints shall be inspected for cracks or any deterioration iv) Shell internal surface of the Desuperheater shall be visually inspected for pitting and

corrosion before and after cleaning.



v) Shell to flange weld joints shall be inspected for cracks or weld corrosion. vi) The weld joints at all the steam inlet and outlet connections with the shell shall be

inspected for cracking. vii) Thickness survey of the shell along with the steam inlet and outlet stub connections shall

be carried out. viii) The weld joints of water inlet and outlet connection with their respective headers should

be inspected by random radiography to check the welding condition. ix) Before inserting the tube bundles, it should be hydraulically tested at 1.5 times the working

pressure.

k) Steam Calorifiers: i) The metallic fins of the calorifier shall be inspected for any deterioration. ii) Steam connection, flange joints with the calorifiers shall be inspected for leakage or any

corrosion. iii) The calorifiers shall be tested with steam to detect any leakage of tube. In case of any

leakage, the leaky tube shall be plugged using plugs of same metallurgy. iv) Calorifier should be replaced if more than 50% tubes have been plugged or earlier

depending upon operational requirements.

l) Air Preheaters Air Preheaters are or two types, recuperative and regenerative type. Air preheaters are subjected to corrosion on flue gas side due to condensation during idle period and also during operation at the region where metal skin temperature falls below dew point. Usually the condition at inlet and outlet ends will give a good indication of the condition in the remaining parts of preheater. 1) Recuperative Type Air Preheater: i) The tube ends and tube sheets shall be inspected for corrosion or tube end thinning. ii) Accumulation of soot or other combustible deposits in the tube surface shall be checked

and choked tubes should be cleaned. iii) Pneumatic testing of air preheater shall be carried out by running the F.D. Fan and

keeping stack dampers in closed position. Leaky tube shall be plugged from both ends or removed. Leakage through expansion joints should be checked, during testing.



2) Regenerative Type Air Heater: i) The compartments shall be inspected for corrosion and pitting. ii) Circumferential and radial seals shall be inspected for corrosion. Rotors metallic sheets

(Rotor blades/buckets) shall be inspected for any mechanical damage. iii) Dust collectors if provided shall be inspected for leakage, corrosion and erosion.

m) Air Duct and Wind Box: i) The surface of the air duct and wind box whenever accessible shall be visually inspected

for scaling, corrosion and pitting. ii) Ultrasonic thickness survey should be carried out to know the remaining thickness of the

plates. iii) The air duct and wind box shall be examined for any buckling or mechanical damage. iv) External surface shall be checked for corrosion which might have taken place due to

defective insulation.

n) Flue Gas Ducts: The metallic flue gas duct plate shall be inspected for internal scaling and corrosion. The scale, if noticed, should be analysed to know the cause of corrosion. Ultrasonic thickness survey shall be done to determine the thinned portions. Expansion bellows shall be checked for leaks and cracks. External surface shall be inspected for corrosion. o) Stacks: The stacks shall be inspected from inside and outside after every 5 years. Refractory in the stacks shall be inspected for cracks, dislodgment and spalling. In the partially refractory lined stacks, metallic bare surface particularly at top shall be inspected for metal wastage in alternative shutdowns. Areas where hot spots had been observed during on-stream inspection shall be inspected for falling of refractory lining. Structures, ladders etc. shall be inspected for corrosion and damage due to weld cracks. Anchor bolts and guy wires should also be inspected for corrosion and scaling. Lightning protection device, if provided, should be inspected and checked in line with stipulations laid down in OISD-STD-137. p) Soot Blowers: i) Inspection shall be done to ensure that the nozzles of the soot blower are maintained in

proper position relative to the tubes. If they are displaced, serious erosion of tube metal and consequent failure can result.

ii) The condition of the nozzles shall be checked for erosion and corrosion.



iii) Steam and air soot blowers shall be inspected for gland packing leaks and evidence of

warpage would tend to make the unit bend and jam while in use. The jammed steam soot blower with the lance in extended condition may cause severe erosion due to high velocity of steam directly impinging on the tubes. Such situations shall be handled on priority. Evidence for leakage of wall box seal and steam shut off valve shall also be checked.

iv) The blower, supporting hangers and brackets shall be examined visually for soundness and for excessive thinning from oxidation.

q) Pipe Connections and fittings: The pipe connections around the Boiler shall be inspected for distortion, metal wastage, supports, settlement of foundation and pipe roller movements. For details OISD inspection standard-130 on process piping can be referred. r) Hydraulic Testing: After completion of inspection, repair and replacement Boiler shall be subjected to a hydraulic test. Preparation & Procedure of Hydro test shall be as per Regulations 378 & 379 of IBR 1950. Some salient points are mentioned below: i) The test pressure shall be from 1.25 to 1.5 times working pressure as per IBR 379 (g). ii) The Boiler shall satisfactorily withstand such pressure without any leakage or undue

deflection or distortion of its parts for at least ten consecutive minutes. iii) During the hydrostatic test, the Inspector shall inspect carefully the Boiler both from inside

and outside for leaks and steadily maintain the pressure. The pressure drop shall also be carefully watched. In case of excessive pressure drop, the Boiler parts shall be thoroughly checked for leaks. Hydro test shall be carried out as per the approved procedure taking all safety precautions.

iv) The temperature of the water used as medium of pressure testing shall not be less than

20°c and greater than 50°C.

v) The test pressure shall be raised gradually under proper control at all times so that it never exceeds by more than 6% of the required pressure and maintained for 30 minutes whereupon the pressure shall be reduced to maximum allowable working pressure and maintained for sufficient time to permit close visual inspection for leakage of pressure parts.

vi) The Boiler shall satisfactorily withstand such pressure without appreciable leakage or

undue deflection or distortion of Its parts for at least ten consecutive minutes. If any part of the Boiler shows undue deflection or indication of permanent deformation during progress of the test, the pressure shall be released immediately. After the application of the hydraulic test the Inspector shall carefully examine the Boiler inside and outside and satisfy himself that it has satisfactorily withstood the test.



For more details, Regulation 379 of Indian Boiler regulations 1950 shall be referred.

s) Safety Valves: Safety valves are the most important attachments on the Boiler; they shall be inspected with the utmost caution. There should be no accumulations of rust scale, or other foreign substances located in the casings so as to interfere with the free operation of the valves. Under no circumstances should a stop valve be permitted between a Boiler and its safety valve. For detailed procedure on safety valves inspection and testing please refer Regulation 390(q) of IBR. Inspection and testing of safety valves shall be done as per OISD Standard -132 on Pressure Relieving Devices. Online Trevi Test of safety valves can be done in consultation with IBR. Online floatation of safety valve shall be carried out as per the approved procedure after taking all safety precautions. t) Deaerator: i) Visual inspection for the external surface of shell column for pitting, corrosion, and cracks

shall be done. ii) All welding shall be checked for corrosion, pitting, and cracks. iii) Column trays and its supports shall be inspected for any choking or deterioration. iv) Chemical dosing distributor pipes and steam injection pipes shall be inspected for any

deterioration. v) Thickness survey of the shell shall be carried out along with its connecting nozzles.

vi) Deaerators should be checked as per statutory requirements NOTE1.

vii) All deaerators shell welds shall be checked once in 5 years by wet fluorescent magnetic

particle testing to detect cracks. u) Blow Down drums: Blow down drum shall be visually inspected. Particular attentions shall be given to the bottom portion where corrosion and pitting is expected. Weld joints along with HAZ shall be checked carefully. Thickness survey of the drums shall be carried out.



10.4 INTERNAL INSPECTION DURING SHUTDOWN (FIRE TUBE BOILER) a) Inspection shall be done to ensure isolation/blanking of fuel gas lines, water lines and

steam lines. b) After opening the Boiler, a check for carbon deposit of the inner surface of fire tubes and

smoke tubes shall be done. c) The condition of refractories near burners, at front reversion chamber and at rear

inspection window shall be carried out. d) The burner assembly shall be checked for any damages. e) The condition of the tubes and fins in radiation chamber shall be checked for any pin

holes in the tubes or cracks in the plates. f) The outer surface of the fire tubes and smoke tubes shall be checked for any wear and

tear or mechanical damage. g) The cocks, blowdown valves, safety valves and the fittings shall be checked for any wear

and tear or mechanical damage. h) After cleaning, the inside and outside, condition of the fire tube and smoke tubes shall be

checked for pitting and corrosion. i) The inner surface of the shell shall be checked for pitting and corrosion.

All the weld joints of the Boiler shell, back plate and tube to tube sheet weld be inspected. j) Other checks and inspection of the Boiler shell, flue gas duct chimney stack, pipe

connections safety valves and fittings shall be same as for water tube Boilers. k) The shell test pressure shall be from 1.25 to 1.5 times working pressure as per IBR 379

(g). Other checks during hydro test shall be same as clause 10.3.2(r) l) Ultrasonic thickness survey, hammer test etc. of the Boiler shell and the tubes shall be

carried out.

m) Other advance NDT should be carried out as & when required as per clause 10.3.2 (g) xiv & xv.

11.0 WASTE HEAT BOILERS/HRSG The inspection of waste heat Boilers of conventional type shall be carried out similar to steam Boilers, as per procedure described earlier. Waste heat Boilers of shell and tube design shall be inspected as per guidelines given in OISD Standard-134 on Inspection for Heat Exchangers. The inspection of HRSG shall be carried out similar to steam Boilers as described earlier. In addition, the following inspection should also be carried out:



i) Condition of the tubes should be checked externally for scales, deposits, damage of fins, displacement, deterioration of the tube spacer etc.

ii) The external deposits of the economizer and evaporator tubes should be collected and chemical analysis shall be done for sulphur content.

iii) All tubes hanger supports should be inspected for corrosion, erosion and looseness of bolts.

iv) Tubes holding supports should be checked for corrosion, erosion and tightness of the bolts to avoid vibration of the tubes during operation.

v) Condition of the holding bolts and tack welding of nut to bolt for the ceramic wool insulation and/or condition of castable refractory should be checked for deterioration.

vi) Condition of the baffle plates should be checked for any deterioration.

vii) In case of Auxiliary Firing, the burner and nearby refractory should be checked as per OEM practices.

viii) Condition of bypass Dampers should be checked for any deterioration.

12.0 CO BOILERS

The inspection of CO Boilers shall be carried out similar to steam Boilers as described earlier. In addition, the following inspection shall also be carried out: i) The soot blower equipment shall be inspected and tested for correct operation. ii) The condition of castable refractory around CO Boiler nozzle shall be inspected for any

damage from fire box. iii) Internal inspection of CO duct, air duct and flue gas duct shall be done during every

planned shutdown. iv) All spring supports shall be inspected for correct functioning during shutdown and

commissioning. v) Fin tubes shall be inspected for any deterioration. vi) Side wall tubes, D-panel tubes and superheater tubes shall be visually inspected in every

planned shutdown. vii) The bellows shall be examined for initiation of any cracks.



13.0 INSPECTION DURING REPAIRS AND REPLACEMENT

13.1 REPAIR/REPLACEMENT OF ECONOMISER Failed economiser tubes shall be partially replaced with new tubes of same specifications. Joint fit up shall be checked. After welding, the joints shall be radiographed. After satisfactory radiography, the coils shall be hydrostatically tested to detect any leak. 13.2 Drums Pits in the drum, which have a depth of 3mm or more can be filled up with welding. The welding shall be ground smooth. Necessary preheating and post weld heat treatment shall be done before welding. Entire repair shall be done as per IBR requirements. Welding inside the drum having visible defects shall be removed by grinding and shall be carefully inspected for cracks, defects etc. The welding can be repaired. The welding shall be subjected to preheat and post heat treatment as specified originally. Complete repaired welding shall be subjected to radiographic examination followed by Hydro test. 13.3 REPLACEMENT OF FIRE BOX TUBES/SUPERHEATER TUBES i) Before starting the welding of the tube joint, the tube ends shall be cleaned from inside

and outside for removing deposits of oxide scale and salts to avoid gas or slag inclusion in the weld.

ii) Weld fit up shall be checked. iii) After welding, the joints shall be radiographed & stress relieved wherever applicable. iv) After satisfactory radiography the tubes shall be subjected to hydrostatic test.

v) Random checking of Tube end wall thickness, tube end outside diameter & drum hole

inside diameter for percentage expansion calculation.

vi) Tube expansion procedure shall be approved and extent of expansion along the tube shall be checked before expansion so as to ensure the expansions are within limits. Bank tube expanding sequence shall be from centre to outwards to ensure locking of drums. The expanding shall be first carried out in upper drum & then in lower drum.

Go-No-Go gauges should be used for inspection & record for tube expansion.

14.0 RECORD AND DOCUMENTATION

Separate record shall be kept for each Boiler. A history card of each Boiler shall be maintained showing shutdown period of Boiler with reasons thereof. Each component of the Boiler shall have a data card giving specification, design, data etc. Also history card of each component shall be maintained giving all observations, repairs and replacements made.



15.0 REFERENCES

This Standard shall be read in conjunction with the following standards, codes and publication. i) Indian Boiler regulations-1950

ii) Indian Boiler Act-1923

iii) ASME Pressure Vessel Code Section-I (Rules for construction of power Boilers)

iv) ASME Pressure Vessel Code Section-IV (Rules for care and operation of Heating Boiler)

v) ASME Pressure Vessel Code Section-VII (Care of Power Boilers)

vi) API 573- Inspection of Fired Boilers and Heaters- RECOMMENDED PRACTICE

vii) OISD STD 132 “Inspection of Pressure Relieving devices”

viii) OISD STD 134 “Inspection of Heat Exchangers’’

ix) OISD STD 137” Inspection of Electrical Equipment”



ANNEXURE-I CHECK LIST The following shall be the checked prior to commissioning of Boilers & Auxiliary equipment:

SN Actions Responsibility Check YES/NO

Remarks

1. Mechanical Completion certificate of Boiler

2. Check if all as built drawings and design calculations are received for records.

3. Check if all test reports of materials, welding, Radiography, stress relieving etc. are received for records.

4. Check for three stages PMI records for alloy steel/ Stainless steel components

5. Check if tubes, supports and connections are installed in accordance with drawings.

6. Check external surface of tubes for deposits

7. Ensure that tubes are free of foreign matters internally

8. Check proper allowance for thermal expansion of tubes.

9. Inspect all weld joints visually. 10. Carry out thickness survey of Tubes

& Headers for record.

11. Check all tubes are placed full seating on their supports.

12. Check if adequate provision is given in lining for thermal expansion.

13. Check for tube expansion records as per drawing.

14. Check burner alignments. 15. Check operability of air registers

dampers, oil guns, pilot burners etc.

16. Check steam tracing to avoid oil congealing in pressure gauge/switch lead lines etc.

17. Check ease of operation for gun changing

18. Check accessibility of all Boiler’s parts.



19. Check and inspect Air Preheaters 20. Ensure rotary APH rotates freely and

provision for expansion is provided.

21. Check and inspect ducting and ensure adequate provision is given for expansion.

22. Inspect duct lining and insulation 23. Test the Boiler tubes and connected

piping hydrostatically

24. Inspection of unlocking of spring supports & Bellows after installation

25. Check for records for chemical cleaning of Boiler

26. Check and inspect general completion of various sections of Boilers.

27. Ensure that all construction equipment, scaffolding etc. are removed.

28. Check if refractory lining is dried out by approved procedure

29. Ensure provision of gusset supports for small bore piping

30. Inspect refractory lining after drying out operation

31. Check for all records as per IBR requirements

32. Apply a pressure test for Boiler and ducting and check leakage.

33. Check operability of soot blowers. 34. Check steam supply to header

boxes, Boilers, soot blowers and coils.

35. Check that all relief valves are set at the correct pressures.

36. Check and inspect structure and all their load bearing welding.

37. Ensure all railings, gratings and floor plates are safe.

38. Check external painting of all structural.

39. Inspect fire proofing 40. Check for records & field verification

for insulation as per approved drawing

41. Check the general cleanliness inside and outside the Boiler prior to commissioning



ANNEXURE-II

Checklist for In-Service inspection of Boilers Date: Unit: Equipment Name & No. Reason for inspection: Inspected by: Legend: S = Satisfactory, NS= Not Satisfactory, NA= Not applicable, NI= Not inspected

Sl No

Description S NS NA NI Observations

1 Foundation & Supports

a. Condition of concrete supports b. Condition of structural steel such as

I beams, channels etc.

c Condition of Spring support

2 Casing and Ducts

a. Condition of insulation b. Visible indication for casing

distortion/corrosion/ cracks

c. Any obstruction to thermal growth d. Condition of access and lancing doors e. Thermal imaging survey for hot spot

locations

3 Piping associated with Boiler

a. Any signs of visible leaks b. Visible indication of bending/ bowing of

pipelines

c. Any vibrations on piping while Boiler is in use

d. Condition of piping supports e. Condition of insulation on piping

4 Instruments

a. Condition of gauge glass b. Satisfactory operation of illuminators ,

reflectors, mirrors

c. Operating condition of valves and gauge cocks

d. Operating condition of level indications, pressure gauges, flow meters

e. Are connections to instruments leak free f. Condition of tube plug and threads

5 Burner flame condition

a. Condition of flame (uniform, wandering etc.)

6 Miscellaneous

Condition of Painting & Fire proofing

Check for short bolting

Condition of PSVs



ANNEXURE-III

Checklist for Shutdown inspection of Boilers Date: Unit: Equipment Name & No. Reason for inspection: Inspected by: Legend: S = Satisfactory, NS= Not Satisfactory, NA= Not applicable, NI= Not inspected

Sl No

Description S NS NA NI Observations

1 Drum (Steam /Mud)

a. Visual condition of drum for scales, pitting, corrosion etc.

b. Visual condition of drum internals including piping

c. Small bore connections to drum d. UT thickness of drums e. MPI of drum f. UFD of drum g. Gasket seating surface condition h. Condition of Magnetite layer in drums

2 Tubes – water wall, side wall, rear wall, furnace wall

a. External visual condition of tubes – corrosion, scaling, bent, sagging, distortions etc.

b. Tubes depositions when inspected from drum side

c. UT thickness of tubes d. Condition of tube supports e. External signs of Roll leaks from

drum to riser tubes

f. Evidence of corrosion from soot blower locations, after tube cleaning

g. Advance NDT inspection

3 Tubes – Super heater, Economiser, Evaporator

a. External visual condition of tubes – corrosion, pitting, scaling, bent, sagging, distortions etc.

b. UT thickness of tubes c. Condition of tube supports d. Evidence of corrosion from soot

blower locations, after tube cleaning

e. Condition of Fins, if any f. Condition of tubes after external

cleaning of tubes

g. Advance NDT inspection



4 Headers

a. External visual condition of headers b. Thickness survey of headers c. Internal condition of headers, if done

5 Burner assembly

a. Visual indications of corrosion (Scale build up, pits etc.) and cracks.

b. Condition of thermocouples c. Inlet guide shroud d. Burner floor conditions

6 Casing

a. Condition of insulation b. Condition of baffle tile and caulking

7 Condition of Refractory

a. At Burner area b. At floor area c. At Soot blowers d. At Instrument tapping locations e. At man-ways

8 Soot blower

a. External visual condition of lancer tubes (Bowing, distortion, Scaling/ Corrosion)

b. Condition of soot blower supports c. UT thickness of small bore tapping of

Steam line connected to Soot blowers.

9 Air Preheater

a. Visual condition of tubes / baskets. (Scaling/ corrosion etc.)

b. Cleaning of Tubes / Baskets c. Hydro/ Pneumatic test of tubes d. Visual condition of seals for RAPH

10 Hydro test a. System hydro test as part of IBR

inspection

b. Safety valve calibration

c. Safety valve floating post commissioning Boiler



ANNEXURE-IV

WEEKLY ROUTINE BOILER INSPECTION REPORT Ref. No _____________ Date__________________ _________________________________________________________________________ S.No. Parameters Design Period To Remarks limits ________________________ MON TUE WED THU FRI SAT __________________________________________________________________________ 1. Feed Water (Ex Deaerator) 02 content 2. Feed Water pH 3. Deaerator Temperature 4. Economiser Water Temperature Inlet Outlet 5. Water Hardness as CaCO3 6. Total dissolved Solids at Boiler drum 7. Chemical Dosing a) Morpholine b) Sulphite (Na2P03) c) Phosphate (Na3P04) d) Hydrazine (NZNNH2) 8. Flue gas temperature (Ex Air Heater) 9. Flame Condition Boiler No.1 Boiler No.2 Boiler No. 3 and so on 10 Other abnormalities (if any) __________________________________________________________________________ Legends: G-Good, I-Impingement, C-Carbonised flame Flame, O-Oxidized, Y-Yes.



ANNEXURE-V

USEFUL TESTS FOR THE CONTROL OF WATER FOR BOILERS _______________________________________________________________________________ CHEMICAL TEST UTILISED FOR PREVENTION OR CONTROL OF METHOD ______________________________________________________________ CORROSION SCALE EBRITTLE- CARRYOVER MENT _______________________________________________________________________________ RAW WATER A-Acidity or * --- --- --- Alkalinity --- * --- --- B-Hardness, Calcium, Magnesium --- * --- --- SOFTENED WATER A-Acidity or alkalinity * --- --- --- B-Hardness, Calcium Magnesium --- * --- --- FEED WATER A-Acidity or Alkalinity * * --- --- B-Hardness, Calcium magnesium --- * --- --- BOILER WATER A-Acidity or alkalinity * * --- --- C-Hydroxide * * * * D-Phosphate --- * * --- E-Sulphate * --- --- --- F-Nitrate --- --- * ---

draft ii oisd-std-131

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