Inspection of Fired Boilers and Heaters

API RECOMMENDED PRACTICE 573 THIRD EDITION, OCTOBER 2013

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Users of this Recommended Practice should not rely exclusively on the information contained in this document. Sound business, scientific, engineering, and safety judgment should be used in employing the information contained herein.

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Copyright © 2012 American Petroleum Institute

Foreword

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Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standards@api.org.

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions and Acronyms 2

   1. Terms and Definitions 2

   2. Acronyms 8

4. Common Heater and Boiler Designs 9

   1. Types of Heaters 9

   2. Types of Boilers 13

5. Heater and Boiler Mechanical Reliability 18

   1. Reliability Programs 18

   2. Safety 21

   3. Purpose of Inspection 21

   4. Inspection of Fired Boilers 22

   5. Inspection of Fired Heaters 22

   6. Inspector Qualifications 22

6. Deterioration Mechanisms 23

   1. Deterioration of Heater Tubes 23

   2. Deterioration of Boiler Tubes 33

   3. Deterioration Mechanisms of Other Components 37

7. Frequency and Timing of Inspections 39

   1. General 39

   2. Boiler Inspection Frequency 39

   3. Heater Inspection Frequency 40

8. Safety Precautions, Preparatory Work, and Cleaning 40

   1. Safety 40

   2. General Preparatory Work 40

   3. Precautions To Avoid Polythionic Acid Stress Corrosion Cracking In Stainless Steel Tubes 42

   4. Cleaning 42

9. Outage Inspection Programs 45

   1. General 45

   2. Visual Inspection of Heater Coils 45

   3. Wall Thickness Measurements 52

   4. Tube Diameter, Circumference, Sag, and Bow Measurements 55

   5. Pit Depth Measurements 57

   6. Intelligent Pigs and In-line Inspection Devices 57

   7. Radiographic Examination 58

   8. Borescope and Videoprobe 58

   9. Hardness Measurements 59

   10. Dye Penetrant and Magnetic Particle Examination 60

   11. In-situ Metallography and Replication 60

   12. Detailed Examination and Destructive Testing Of Tube Samples 60

   13. Testing of Tubeskin Thermocouples 61

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       Contents

       Page

   14. Magnetic Test For Carburization 61

   15. Hammer Testing 61

   16. Inspection of Reformer Tubes 62

   17. Inspection of Pigtails 64

10. Boiler Outage Inspection 65

    1. General 65

    2. Piping 65

    3. Drums 65

    4. Water Headers 67

    5. Superheater Header 67

    6. Tubes 68

11. On-stream Inspection Programs 69

    1. General 69

    2. Typical Inspection Activities 70

    3. External Tube Cleaning 73

    4. Pre-shutdown Inspection 73

12. Tube Reliability Assessment 73

    1. General 73

    2. Minimum Thickness and Stress Rupture 74

    3. Creep Rupture Life 76

13. Method of Inspection for Foundations, Settings, and Other Appurtenances 76

    1. Foundations 76

    2. Structural Supports 77

    3. Setting, Exterior, and Casing 77

    4. Refractory Linings and Insulation 78

    5. Tube Supports 79

    6. Visual Inspection of Auxiliary Equipment 81

    7. Stacks 86

14. Repairs 88

    1. Heaters 88

    2. Boilers 88

    3. Materials Verification 89

15. Records and Reports 89

Annex A (informative) Sample Inspection Checklists for Heaters and Boilers 90

Annex B (informative) Sample Heater Inspection Records 98

Annex C (informative) Sample Semi-Annual Stack Inspection Record 108

Bibliography 109

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Contents

Figures

Page

1. Typical Heater Types 9

2. Box-type Heater with Horizontal Tube Coil Showing Main Components 11

3. Steam Methane Reforming Heater 12

4. Typical Vertical Oil or Gas-fired Water Tube Boiler 14

5. Another Variation of a Two-drum Bent Tube Boiler 15

6. Typical Carbon Monoxide Boiler 16

7. Tubular and Plate Air Preheaters 18

8. Types of Regenerative Air Preheaters 19

9. ID of Fireside Portion of Tube Showing Severe Corrosion 25

10. Convective Tube Failure from Internal, High-temperature Sulfidic Corrosion 25

11. General Metal Loss and Pitting of Tubes Exposed to Moisture and Corrosive Deposits

    During Idle Periods 26

12. Roof Tubes Sagged as a Result of Failed Tube Hangers 27

13. Changes in Magnetic Permeability Caused by Chromium Depletion 31

15 Boiler Tube Showing Penetration of the Tube Wall by a Localized Oxygen Pit 34

14 Localized Tubing Wall Loss Caused by Caustic Gouging 34

1. Short-term Boiler Tube Failure Caused by Waterside Deposits, Subsequent Overheating,

   and Final Bulging of the Tube Wall 35

2. Longer-term Boiler Tube Failure Caused by Poor Circulation and Subsequent Overheating,

   Oxidation, and Final Failure by Stress Rupture 35

3. Dew Point Corrosion from Flue Gas Corrosion on Radiant Section Header Box 38

4. Mechanical Decoking Pig 43

5. Bulged Tube 48

6. Bulged and Split Tube 48

7. Scaled Tube 49

8. Oxidized Tube 49

9. Split Tube 50

10. External Corrosion 50

11. Fitting and Tube that Have Leaked in the Roll 51

12. Corrosion/Erosion of the Annular Space in a Streamlined Fitting 52

13. Corrosion of U-bends 53

14. Spreading and Poor Fit of a Horseshoe Holding Section 53

15. Tube Damage Caused by Mechanical Cleaning Equipment 56

16. Eccentric Corrosion of a Tube 56

17. Intelligent Pig Positioned in Short Radius 1D x 180° Return Bend 58

18. Spot-type and Pit-type Corrosion 59

19. Various Magnetic Measurement Devices 2

20. Laser Profilometry Results 63

21. Interior Surface of a Tube Damaged by Operating a Tube Cleaner Too Long in One Place 69

22. Infrared Thermography Identifying a Local Hot Spot on Tubes 72

23. Infrared Thermography Identifying a Hot Coil 72

24. Sample Locations for Tell-tale Holes on Heater Tubes 73

25. Types of Heater Fittings 75

26. Yielding and Creep of a Tube Support Connection 80

    vii

    Contents

    Page

27. Corrosion Products from Acid Condensation Plug Tubes in Air Preheater 83

28. Improper Burner Tile Installation Leads to Poor Flame Pattern 85

29. Self-supporting Steel Stack 87

Tables

1. Common Heater Tube Metallurgies 13

2. Tube Deterioration Mechanisms Common to Specific Services 20

3. Tube Deterioration Mechanisms Common to Specific Services 23

4. Recommended Inspection and Acceptance Criteria for Deterioration Mechanisms 46

5. Tube Support Materials Specifications Maximum Design Temperatur 80

Examples

1. Fired Heater Internal and External Inspection Checklist 91

2. Water Tube Boiler Inspection Checklist 93

3. Fire Tube Boiler Inspection Checklist 95

A.4a Fired Heater Operator Rounds Checklist (Checklist I)96 A.4b Fired Heater Operator Rounds Checklist (Checklist II)97

1. Sample of Tube Layout Drawing 99

2. Sample of Tube Inspection History 100

3. Sample of Tube Inspection Record (Tubes Calipered) 102

4. Sample of Tube Inspection Record (Instrument Calipered) 103

5. Sample of Tube Renewal Record 105

6. Sample of Field Work and Record Sheet (Tube Rolling) 106

7. Sample Record of Heater Fitting Inspection and Replacement 107

viii

Inspection of Fired Boilers and Heaters

1. Scope

   
   

   This recommended practice (RP) covers the inspection practices for fired boilers and process heaters (furnaces) used in petroleum refineries and petrochemical plants. The practices described in this document are focused to improve equipment reliability and plant safety by describing the operating variables that impact reliability, and to ensure that inspection practices obtain the appropriate data, both on-stream and off-stream, to assess current and future performance of the equipment.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry

API Recommended Practice 572, Inspection Practices for Pressure Vessels

API Recommended Practice 578, Material Verification Program for New and Existing Alloy Piping Systems

API Recommended Practice 579, Fitness-For-Service

API Recommended Practice 580, Risk Based Inspection

API Recommended Practice 939-C, Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil

API Standard 530, Calculation of Heater Tube Thickness in Petroleum Refineries AISC M015L 1, Manual of Steel Construction, Load and Resistance Factor Design AISC M016, Manual of Steel Construction, Allowable Stress Design

ASME B31.1 2, Power Piping

ASME Boiler and Pressure Vessel Code, Section I: Power Boilers

ASME Boiler and Pressure Vessel Code, Section IV: Heating Boilers

ASME Boiler and Pressure Vessel Code, Section VI: Recommended Rules for Care and Operation of Heating Boilers

ASME Boiler and Pressure Vessel Code, Section VII: Recommended Guidelines for Care of Power Boilers

ASME Boiler and Pressure Vessel Code, Section IX: Welding and Brazing Qualification

ASNT CP-189 3, ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel

1. AISC, One East Wacker Drive, Suite 700, Chicago, Illinois 60601-1802, www.asic.org.

2. ASME International, 3 Park Avenue, New York, New York 10016-5990, www.asme.org.

3. ASNT, 1711 Arlingate Lane, Columbus, OH 43228-0518, www.asnt.org.

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