Tank Inspection with magnetic flux leakage Ppt.pptx

Tank Inspection with magnetic flux leakage Ppt.pptx

1. Guidelines and Methods for Inspection of Atmospheric and Low-pressure Storage Tanks 08-March-2023 Sriram Avinash For the benefit of business and people

2. 1 Scope 2 2&3 References& Definitions Types of Storage Tanks Reasons for Inspection & Causes of Deterioration. Inspection Frequency & Scheduling. Methods of Inspection Tank Assessment Tank Repair & Alterations Records Appendix A SU M M A R Y

3. Scope 3 1

4. Scope 4 Title of the presentation - DD/MM/YY 1 This document provides useful information and recommended practices for the maintenance and inspection of atmospheric and low-pressure storage tanks. While some of these guidelines may apply to other types of tanks, these practices are intended primarily for existing tanks that were constructed to API Spec 12A or API Spec 12C, and API Std 620 or API Std 650.

5. Ref e r e nce s & Definitions 5 2&3

6. 2&3 References& Definitions 6 Title of the presentation - DD/MM/YY References: API, ASME, ASNT, ASTM, OSHA Definitions: alteration: Any work on a tank involving cutting, burning, welding, or heating operations that changes the physical dimensions and/or configuration of a tank. Examples of alterations include: The addition of a man way or nozzle exceeding 12 in. NPS (nominal pipe size). An increase or decrease in tank shell height.

7. applicable standard: The original standard of construction, such as API standards unless the original standard of construction has been superseded or withdrawn from publication; in this event, applicable standard means the current edition of the appropriate standard. atmospheric pressure: When referring to (vertical) tanks, the term “atmospheric pressure” usually means tanks designed to API Std 650. API Std 650 & 653 provides for rules to design tanks for “internal pressure” up to 21/2 lbf/in.2. 7 Title of the presentation - DD/MM/YY 2&3 References& Definitions

8. 3.4 authorized inspection agency: It can be one of the following: The inspection organization of an insurance company which is licensed or registered to and does write aboveground storage tank insurance An owner or operator of one or more aboveground storage tank (s) who maintains an inspection organization for activities relating only to his equipment and not for above ground storage tanks intended for sale or resale. An independent organization or individual under contract to and under the direction of an owner or operator and recognized or otherwise not prohibited by the jurisdiction in which the aboveground storage tank is operated. The owner or operator’s inspection program shall provide the controls necessary for use by authorized inspectors contracted to inspect aboveground storage tanks. 8 Title of the presentation - DD/MM/YY 2&3 References& Definitions

9. authorized inspector: An employee of an authorized inspection agency that is certified as an aboveground storage tank inspector per API Std 653, Appendix D. bottom-side: The exterior surface of the tank bottom, usually used when describing corrosion. Other terms with the same meaning are “under-side” or “soil-side.” change-in-service: A change from previous operating conditions involving different properties of the stored product such as specific gravity or corrosivity and/or different service conditions of temperature and/or pressure. 9 Title of the presentation - DD/MM/YY 2&3 References& Definitions

10. 3.8 examiner: A person who assists the API authorized tank inspector by performing specific non-destructive examination (NDE) on the tank but does not evaluate the results of those examinations in accordance with API Std 653 or this recommended practice, unless specifically trained and authorized to do so by the owner or user. The examiner does not need to be certified in accordance with API Std 653 nor needs to be an employee of the owner or user, but shall be trained and competent in the applicable procedures in which the examiner is involved. In some cases, the examiner may be required to hold other certifications as necessary to satisfy owner or user requirements. Examples of other certification that may be required are American Society for Non-Destructive Testing SNT-TC- 1A or CP189, or American Welding Society Welding Inspector Certification. The examiner’s employer shall maintain certification records of the examiners employed, including dates and results of personnel qualifications and shall make them available to the API Authorized Inspector. 10 Title of the presentation - DD/MM/YY 2&3 References& Definitions

11. inspector: An Authorized Inspector and an employee of an Authorized Inspection Agency who is qualified and certified to perform tank inspections under this standard. MFL (magnetic flux leakage): An electromagnetic scanning technology for tank bottoms. Also known as MFE (magnetic flux exclusion). product-side: The interior surface of a tank bottom, usually used when describing corrosion. Other terms with the same meaning are “top-side” or “product-side.” owner/operator: The legal entity having control of and/or responsibility for the operation and maintenance of an existing storage tank. 11 Title of the presentation - DD/MM/YY 2&3 References& Definitions

12. reconstruction: The work necessary to re-assemble a tank that has been dismantled and relocated to a new site. reconstruction organization: The organization having assigned responsibility by the owner/operator to design and/or reconstruct a tank. repair: Any work necessary to maintain or restore a tank to a condition suitable for safe operation. Typical examples of repairs includes: Removal and replacement of material (such as roof, shell, or bottom material, including weld metal) to maintain tank integrity. Re-levelling and/or jacking of a tank shell, bottom, or roof. Addition of reinforcing plates to existing shell penetrations. Repair of flaws, such as tears or gouges, by grinding and/or gouging followed by welding. 12 Title of the presentation - DD/MM/YY 2&3 References& Definitions

13. shell capacity: The capacity that the tank can hold based on the design liquid level (see API Std 650). soil-side: See definition for bottom-side. storage tank engineer: One or more persons or organizations acceptable to the owner or user who are knowledgeable and experienced in the engineering disciplines associated with evaluating mechanical and material characteristics affecting the integrity and reliability of tank components and systems. The tank engineering, by consulting with appropriate specialists, should be regarded as a composite of all entities necessary to properly address technical requirements and engineering evaluations . 13 Title of the presentation - DD/MM/YY 2&3 References& Definitions

14. tank specialist: Someone experienced in the design and construction of tanks per API Std 620 and/or API Std 650, and the inspection and repair of tanks per API Std 653. top-side: See definition for product-side. 14 Title of the presentation - DD/MM/YY 2&3 References& Definitions

15. Types of Storage Tanks 15 4

16. 4 16 Title of the presentation - DD/MM/YY 4.1 GENERAL Important factors such as the volatility of the stored fluid and the desired storage pressure result in tanks being built of various types, sizes, and materials of construction. In this document, only atmospheric and low pressure storage tanks are considered. Guidelines for inspection of tanks operating at pressures greater than 15 lbf/in.2 (103 kPa) gauge are covered in API RP 572. Types of Storage Tanks GENER A L

17. 4 17 Title of the presentation - DD/MM/YY Storage Tanks with Linings and/or Cathodic Protection Tank Bottom Lining (API RP 652) Cathodic protection (API RP 651) Storage Tanks with Leak Detection Systems Design Guidelines for leak detection (API Std 650,Appendix I) GENER A L Types of Storage Tanks

18. 4 18 Title of the presentation - DD/MM/YY 4.1.3 Storage Tanks with Auxiliary Equipment Most storage tanks are provided with some of the following auxiliary equipment such as liquid-level gauges, high-and low-level alarms and other overfill protection systems, pressure- relieving devices, vacuum venting devices, emergency vents, roof drain systems, flame arrestors, fire protection systems and mixing devices. Stairways, ladders, platforms, handrails, piping connections and valves, manholes, electric grounding connections (as required) and cathodic protection systems are considered examples of storage tank auxiliary equipment. GENER A L Types of Storage Tanks

19. 4 19 Title of the presentation - DD/MM/YY ATMOSPHERIC STORAGE TANKS Construction Materials and Design Standards Atmospheric storage tanks are designed to operate with their gas and vapor spaces at internal pressures approximating atmospheric pressure. Such tanks are usually constructed of carbon steel, alloy steel, aluminium or other metals, depending on service. Additionally, some tanks are constructed of non-metallic materials such as reinforced concrete, reinforced thermosetting plastics, and wood. Some wooden tanks constructed to API Spec 12E are still in service. Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

20. 4 20 Title of the presentation - DD/MM/YY 4.2.2 Use of Atmospheric Storage Tanks AST in the petroleum industry are normally used for fluids having a true vapor pressure that is less than atmospheric pressure. Vapor pressure is the pressure on the surface of a confined liquid caused by the vapors of that liquid. Vapor pressure varies with temperature and increases as the temperature rises. Crude oil, heavy oils, gas oils, furnace oils, naphtha, gasoline, and non-volatile chemicals are usually stored in atmospheric storage tanks. Many of these tanks are protected by pressure -vacuum vents that maintain the pressure difference between the tank vapor space and the outside atmosphere to just a few ounces per square inch. Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

21. 4 4.2.3 Types of Atmospheric Storage Tank Roofs The most common type of atmospheric storage tank is the fixed cone roof tank, These roofs are normally supported by internal structural but can be fully self- supporting in smaller diameters (typically, 60 ft [3 m] diameter or less). up to 300 ft (91.5 m) in diameter & 64 ft (19.5 m) in height (larger diameter tanks have been built, mostly outside the U.S.) 21 Title of the presentation - DD/MM/YY Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

22. 4 4.2.3 Types of Atmospheric Storage Tank Roofs The umbrella roof has radially-arched segmental plates with integral framing support members (usually without internal support columns). In the steel dome roof tank, the roof plates are usually formed with curved segments joined to be self-supporting. 22 Title of the presentation - DD/MM/YY Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

23. 4 4.2.3 Types of Atmospheric Storage Tank Roofs The floating-roof tank is designed to minimize filling and breathing losses by eliminating or minimizing the vapor space above the stored liquid. The shell and bottom of this type of tank are similar to those of the fixed roof tanks, but in this case, the roof is designed to float on the surface of the stored liquid. Older styles of floating roofs include single steel deck details without annular pontoons. Such roofs have no reserve buoyancy and are susceptible to sinking in service. Types of Storage Tanks 23 Title of the presentation - DD/MM/YY ATMOSPHERIC STORAGE TANKS

24. 4 4.2.3 Types of Atmospheric Storage Tank Roofs Annular-pontoon and double-deck Some floating-roof tanks have fixed aluminium geodesic dome roofs installed on top of the tank shell to reduce product vapor loss or to eliminate the need to drain rainwater from the roof. These are considered internal floating roofs is a tank with a fixed steel cone roof over a floating roof. Types of Storage Tanks 24 Title of the presentation - DD/MM/YY ATMOSPHERIC STORAGE TANKS

25. 4 25 Title of the presentation - DD/MM/YY Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

26. 4 4.2.3 Types of Atmospheric Storage Tank Roofs Floating-roof sealing systems are used to seal the space between the tank wall and the floating roof, typically with a mechanical seal. This type of seal consists of a shoe which is a plate that is pressed against the tank wall by springs (or by counter-weights in older designs) or other tensioning system, with a flexible vapor membrane attached between the shoe and the floating roof outer rim. 26 Title of the presentation - DD/MM/YY Types of Storage Tanks ATMOSPHERIC STORAGE TANKS

27. 4 27 Title of the presentation - DD/MM/YY 4.3 LOW PRESSURE STORAGE TANKS 3.3.1 Description and Design of Low-pressure Storage Tanks Low-pressure storage tanks are those designed to operate with pressures in their gas or vapor spaces exceeding the 2.5 lbf/in.2 (18 kPa) gauge permissible in API Std 650, but not exceeding the 15 lbf/in.2 (103 kPa) gauge maximum limitation of API Std 620. These tanks are generally constructed of steel or alloy steel and are usually welded, although riveted tanks in low-pressure service are still found. Rules for the design and construction of large, welded, low-pressure storage tanks are included in API Std 620. Types of Storage Tanks LOW PRESSURE STORAGE TANKS

28. 4 28 Title of the presentation - DD/MM/YY 4.3.2 Use of Low Pressure Storage Tanks Low-pressure storage tanks are used for the storage of the more volatile fluids having a true vapor pressure exceeding the pressure limits of API Std 650, but not more than 15 lbf/in.2 (103 kPa) gauge. Light crude oil, some gasoline blending stock, light naphtha, pentane, some volatile chemicals, liquid oxygen and liquid nitrogen are examples of liquids that may be stored in low-pressure storage tanks . Types of Storage Tanks LOW PRESSURE STORAGE TANKS

29. 4 4.3.3 Types of Low Pressure Storage Tank Roofs Tanks that have cylindrical shells and cone or dome roofs are typically used for pressures less than about 5 lbf/in.2 (34.5 kPa) gauge. Tank bottoms may be flat or have a shape similar to the roof. Hold-down anchorage of the shell is generally required. Vapor Dome Roof 29 Title of the presentation - DD/MM/YY Types of Storage Tanks LOW PRESSURE STORAGE TANKS

30. 4 4.3.3 Types of Low Pressure Storage Tank Roofs For pressures above about 5 lbf/in.2 Gauge (34.5 kPa), hemispheroid, spheroid, and noded spheroid tank types are commonly used. Tanks for this application are now typically constructed as spheres. Such tanks are designed to withstand the vapor pressure that may be developed within a tank having no devices or means to change or relieve the internal volume. Plain Hemispheroids 30 Title of the presentation - DD/MM/YY Types of Storage Tanks LOW PRESSURE STORAGE TANKS

31. 4 4.3.3 Types of Low Pressure Storage Tank Roofs Hemispheroid 31 Title of the presentation - DD/MM/YY Plain Spheroid Types of Storage Tanks LOW PRESSURE STORAGE TANKS

32. 32 Reasons for Inspection and Causes of Deterioration 5

33. 5 33 Title of the presentation - DD/MM/YY 5.1 REASONS FOR INSPECTION Reduce the potential for failure and the release of stored products. Maintain safe operating conditions. Make repairs or determine when repair or replacement of a tank may be necessary. Determine whether any deterioration has occurred, and if so, prevent or retard further deterioration. Keep ground water, nearby waterways, and the air free of hydrocarbon and chemical pollution. Regulatory compliance. Risk management through data gathering and prioritization of maintenance and capital expenditures. Reasons for Inspection & Causes of Deterioration REASONS FOR INSPECTION

34. 5 34 Title of the presentation - DD/MM/YY 5.2 DETERIORATION OF TANKS External Corrosion Foundation material used for forming a pad under the bottom may contain materials that can promote corrosion. Poor drainage may allow water to remain in contact with the tank bottom. Accumulation of the fluid under the tank can cause external corrosion of the tank bottom. A n i mproperly sealed ring wall, as sho w n in Figure, may allow moisture to accumulate between the tank and the support, thereby accelerating corrosion. DETERIOR A T I ON OF TANKS Reasons for Inspection & Causes of Deterioration

35. 5 Foundation Seal 35 Title of the presentation - DD/MM/YY Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

36. 5 36 Title of the presentation - DD/MM/YY External Corrosion The lower tank shell can become severely corroded externally at, or just above, or below, the grade line, where soil movement has raised the grade level to cover the lower portion of the shell. External corrosion also occurs when external insulation absorbs ground or surface water by wicking action, or when damaged or improperly sealed openings around nozzles and attachments allow water behind the insulation. A sulfurous, acidic or marine atmosphere can damage protective coatings and increase the rate of corrosion. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

37. 5 37 Title of the presentation - DD/MM/YY External Corrosion The type of tank and the construction details used can affect the location and extent of external corrosion. Inspections should look for areas where tank construction details cause water or sediment to accumulate. Riveted tanks offer many niches where concentration cell corrosion can occur. Leaks at seams of riveted tanks may cause failure of external coatings, allowing external corrosion to develop. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

38. 5 38 Title of the presentation - DD/MM/YY Internal Corrosion/Deterioration Riveted tanks offer many niches where concentration cell corrosion can occur. Leaks at seams of riveted tanks may cause failure of external coatings, allowing external corrosion to develop. Internal corrosion in the vapor space above the liquid of these tanks can be caused by hydrogen sulfide vapor, water vapor, oxygen, or any combination of these. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

39. 5 39 Title of the presentation - DD/MM/YY Internal Corrosion/Deterioration In the areas in contact with the stored liquid, corrosion is commonly caused by acid salts, hydrogen sulfide or other sulfur compounds, or contaminated water that settles out and mixes with solids on the bottom of the tank. This layer is typically referred to as bottom sediment and water (BS&W). Stress corrosion cracking can be concern where the product is known to be reactive with welds and heat-affected zones. Areas of high stress concentration, such as at weld seams and around nozzle necks, are more susceptible to accelerated corrosion due to the effects of product contact. Hydrogen blistering, hydrogen grooving, caustic stress corrosion cracking, electrolytic corrosion and acid erosion. (API 571) Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

40. 5 40 Title of the presentation - DD/MM/YY 5.3 DETERIORATION OF OTHER THAN FLAT BOTTOM AND NON-STEEL TANKS Concrete tanks can be attacked by the tank contents, can crack because of settlement or temperature changes, or can spall because of atmospheric conditions, resulting in exposure of the steel reinforcing bars to further atmospheric corrosion. External stress corrosion cracking of stainless steel tanks may be a concern if chlorides that may be present in insulation get wet or enter the insulation. Aluminium can be affected by impurities such as acids or mercury compounds in process streams or wastewater. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

41. 5 41 Title of the presentation - DD/MM/YY 5.4 LEAKS, CRACKS, AND MECHANICAL DETERIORATION Leaks can occur at improperly welded or riveted joints, at pipe thread or gasket connections or cover plates, or at crack-like flaws (including arc strikes on plates) in welds or in plate material. Three-plate in lap- welded tank bottoms are particularly prone to defects that can lead to leaks. Crack-like flaws can result from a number of causes, including deficiencies in design, fabrication, and maintenance. The most likely points for crack-like flaws to occur are at the bottom-to-shell details, around nozzle connections, at manholes, around rivet holes or around rivet heads, at welded brackets or supports, and at welded seams. The lower-shell-to-sketch-plate or shell-to-bottom weld is especially critical because in relatively large or relatively hot tanks, there is a higher likelihood this detail can develop a crack-like flaw due to high stresses. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

42. 5 42 Title of the presentation - DD/MM/YY 5.5 DETERIORATION AND FAILURE OF AUXILIARY EQUIPMENT Examination of tank venting devices should be included in periodic inspection to ensure that proper operation and protection are maintained. See API RP 576 for information regarding inspection of pressure-relieving devices. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

43. 5 43 Title of the presentation - DD/MM/YY 5.6 SIMILAR SERVICE METHODOLOGY FOR ESTABLISHING TANK CORROSION RATES Similar service uses experience from tanks in similar locations and services to establish corrosion rates. The similar service should be examined independently for both the product-side and the soil-side corrosion since the mechanisms and corrosion rates are entirely independent of one another. Reasons for Inspection & Causes of Deterioration DETERIOR A T I ON OF TANKS

44. Inspection Frequency and Scheduling 44 6

45. 6 Inspection Frequency and Scheduling FREQUENCY OF INSPECTION (API 653) CONDITION-BASED INSPECTION SCHEDULING CONDITION-BASED INSPECTION SCHEDULING 45 Title of the presentation - DD/MM/YY

46. 6 46 Title of the presentation - DD/MM/YY In most cases, the new thickness includes some excess thickness. This excess thickness may be the result of any one or all of the following factors: Additional thickness added to the required thickness as a corrosion allowance. Additional thickness resulting from using the closest, but larger, nominal plate thickness, rather than the exact value calculated. Additional thickness from deliberately setting the minimum acceptable thickness of plates for construction purposes. Additional thickness on the upper portions of shell courses not required for product loading at that level. Additional thickness, available due to a change in tank service or a reduced operating fill height. Inspection Frequency and Scheduling CONDITION-BASED INSPECTION SCHEDULING

47. 6 47 Title of the presentation - DD/MM/YY For structural members and parts, such as roof supports and platforms, normal accepted industry practice for structural design (such as methods provided in the Steel Construction Manual issued by the American Institute of Steel Construction) can be used to calculate the allowable loads of members in the new condition. For external piping, nozzles, and valves, the methods provided in API 570 and ASME standards can be used to determine minimum acceptable thickness. Inspection Frequency and Scheduling CONDITION-BASED INSPECTION SCHEDULING

48. API-653 provides an extensive list of factors to be considered in determining appropriate inspection intervals for in- service tanks. Inspections from Outside the Tank: According to the standard, all tanks must receive an external inspection by an authorized inspector at least once every 5 years , or more frequently depending on the rate of tank shell corrosion. 48

49. Internal Inspections: API-653 generally requires that all newly installed tanks receive an internal inspection within 10 years of their entry into service. However, the maximum initial internal inspection interval may extend up to 25 years based on the completion of a risk-based inspection (RBI) assessment and the types of leak prevention, detection or containment safeguards that have been installed. Subsequent internal inspections are based on the rate of corrosion, with the duration extending from 20 to 30 years , depending on the method used to assess the rate of corrosion. Corrosion rate may be estimated from tanks in similar service. If corrosion rate is not known or and similar service assessment data is not available, the actual “t” shall be determined, interval shall not exceed 10year of operation. 49

50. The interval between inspections is most influence by service history , unless special reason indicate early inspection (6.2.2). In the case of insulated tanks remove the insulation to the extent necessary to determine condition of roof & shell (6.3.2.2). Tank grounding system components, shunts, cable connections etc. shall be visually checked (6.3.2.3). 50

51. 6 51 Title of the presentation - DD/MM/YY 6.4 FITNESS-FOR-SERVICE EVALUATION Aboveground storage tanks can be evaluated to determine fitness for continued service. API RP 579 provides fitness-for-service (FFS) evaluation criteria for tanks based on what is known or can be determined about the tank from various inspections. Different levels of assessment are provided, depending on the information available for evaluation and resources (experience and money) available. FFS deals primarily with the evaluation of defects and flaws such as corrosion, pitting, crack-like flaws, laminations, and distortions that can affect remaining service life. Specific criteria for evaluating defects or flaws are provided for in API RP 579 . Inspection Frequency and Scheduling F I TN ESS- F O R -SE R VI C E EVALUATION

52. Methods of Inspection 52 7

53. 7 53 Title of the presentation - DD/MM/YY PREPARATION FOR INSPECTIONS Before entering or re-entering any tank, appropriate safety precautions are necessary. These precautions are discussed in detail in API Std 2015 and API RP 2016. Generally, such precautions include, but are not limited to, the following: Removal of hazardous gases. Removal of gas-generating, pyrophoric, or toxic residues. Isolation from any source of toxic or gas-generating fluids by the use of blinds or by disconnection/isolation. Assurance of an atmosphere that contains sufficient oxygen. Where applicable, OSHA rules for safe entry into confined spaces should be followed (Title 29, Code of Federal Regulations , Part 1910.146). Potential for collapse of either fixed or floating roofs . Methods of Inspection PREPARATION FOR INSPECTIONS

54. EXTERNAL INSPECTION OF AN IN-SERVICE TANK Ladder and Stairway Inspection S hould be examined carefully for corroded or broken parts. Its condition of may be checked by visual inspection and by sounding . Platform and Walkway Inspection Can be inspected in the same manner as ladders and stairways. The thickness of walking surfaces used by personnel can be checked at the edges with calipers and in other areas by tapping with a hammer. Low spots where water can collect should be checked carefully because corrosion may be rapid in such areas. Drain holes can be drilled in the area to prevent future accumulation of water. 54 Title of the presentation - DD/MM/YY EXTERNAL INSPECTION OF AN IN-SERVICE TANK 7 Methods of Inspection

55. 7 7.2.3 Foundation Inspection The foundations of tanks may be made of sand or other fill pads; crushed stone pads or stone-filled grade bands; steel and concrete piers, ring walls, or natural earth pads. Pads should be visually checked for erosion and for uneven settlement. The opening or joint between a tank bottom and the concrete pad or base ring should be sealed to prevent water from flowing under the tank bottom. 55 Title of the presentation - DD/MM/YY Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

56. 7.2.4 Anchor Bolt Inspection The condition of anchor bolts can usually be determined by visual inspection. Visual inspection can be aided by removal of the nuts, one by one, or supplemented by ultrasonic thickness examination. Anchor bolts nuts should be checked for a snug fit to the anchor bolt chair top plate (i.e., there should be no distance between the location of the nut on the bolt and the anchor chair top plate.) 7 Methods of Inspection 56 Title of the presentation - DD/MM/YY EXTERNAL INSPECTION OF AN IN-SERVICE TANK

57. 7.2.5 Grounding Connection Inspection The grounding connections should be visually checked for intact connection and for corrosion at the point where they enter the earth or attach to a grounding rod and at the tank ground clip. If any doubt exists about the condition of the grounding connection, its resistance can be checked. The total resistance from tank to earth should not exceed approximately 25 ohms. 57 Title of the presentation - DD/MM/YY 7 Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

58. 7 58 Title of the presentation - DD/MM/YY 7.2.6 Protective Coating Inspection Rust spots, blisters, peeling, cracking and coating due to lack of adequate bond, are all types of common paint failure. Rust spots and blisters are easily found by visual inspection. Coating bond failure is not easily seen unless a blister has formed or has broken. Care should be taken not to significantly damage protective coatings during inspection. Paint blisters occur most often on the roof and on the side of the tank receiving the most sunlight. Coating bond failure commonly occurs below seam leaks. Other points at which the paint may fail are in crevices or depressions and at tank seams that are welded, riveted, or bolted. The paint on the tank roof is especially susceptible to accelerated failure. The paint on floating roofs should be inspected carefully, especially in areas where there is standing water or product. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

59. 7 59 Title of the presentation - DD/MM/YY 7.2.7 Insulation Inspection Visual examination is normally performed. Detailed inspection should be conducted around nozzles, around the saddles of horizontal tanks, and at caulked joints. Areas of insulation may need to be removed prior to such inspection especially on the shaded side of the tank, on roofs, below protrusions, and at areas of obvious water Intrusion. Insulation support clips, angles, bands, and wires should be spot- checked for tightness and signs of corrosion and breakage. If access is available internally, many of these areas can be checked by UT from the inside. Corrosion under insulation (CUI) is most aggressive in temperature ranges between 120°F (49°C) and 200°F (93°C). Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

60. 7 60 Title of the presentation - DD/MM/YY 7.2.8 Tank Shell Inspection If any foreign material or soil has collected around the bottom of the shell or if the tank has settled below grade, a close inspection should be made at and below the grade line. Tanks with products at elevated temperatures in cold climates may have water present near the shell and under the bottom because of ice or snow build up around the tank. Corrosion products or rust scale can be removed by picking, scraping, wire brushing, or blasting (with sand, grit or water under high pressure) so that the depth and extent of the corrosion may be evaluated. The potential hazards of using such methods should be evaluated beforehand. For example, hammer testing or removal of heavy scale should not be done with the tank under pressure or otherwise in service. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

61. 7 61 Title of the presentation - DD/MM/YY 7.2.8.1 Thickness Measurements (API 653) Sun, shade, prevailing winds, and marine environments may affect the rate of external corrosion significantly. These factors need to be considered when determining the number and location of thickness measurements to be taken. In obtaining shell thickness, special attention should be given to the upper 24 in. (61 cm) of uncoated shells of floating-roof tanks. These portions of the shell plates can corrode at a higher rate than the lower shell plates because of constant exposure to the atmosphere on both sides. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

62. 7 62 Title of the presentation - DD/MM/YY 7.2.8.2 Stiffeners and Wind Girders Can be inspected visually and by hammer testing. Thickness measurements should be made at points where corrosion is evident. Any pockets or crevices between the rings or girders and the shell should receive close attention. If the stiffening members are welded to the shell, the welds should be visually checked for cracks. The areas can be checked by the magnetic particle or liquid penetrant examination method. If the magnetic particle method is used for detecting cracks while the tank is in service, current flow (prod techniques) should not be used because of the danger of sparks. For this type of test, a permanent magnet or electromagnet (magnetic flow) technique should be used. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

63. 7 63 Title of the presentation - DD/MM/YY 7.2.8.3 Caustic Cracking If caustic or amine is stored in a tank, the tank should be checked for evidence of damage from caustic stress corrosion cracking, sometimes referred to as caustic embrittlement. The most probable place for this to occur is around connections for internal heating units or coils. This type of deterioration is manifested by cracks that start on the inside of the tank and progress through to the outside. If this condition exists, the caustic material seeping through the cracks will deposit readily visible salts (usually white). Thorough cleaning and checking with indicating solutions is necessary before welded repairs are conducted on steel that has been affected by caustic stress corrosion cracking. Cracking may occur during welding repairs in such areas. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

64. 7 64 Title of the presentation - DD/MM/YY 7.2.8.4 Hydrogen Blisters (API 571) They are found most easily by visual examination and by touch. Visual examination should be aided by use of hand-held lighting of sufficient candlepower (at least 100 lumens) under low ambient lighting conditions, holding the flashlight against the shell so the light beam shines parallel to the shell surface. Many small blisters can be found by running fingers over the metal surface. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

65. 7 65 Title of the presentation - DD/MM/YY 7.2.8.5 Leaks, Crack-like Flaws, and Distortion Leaks are often marked by a discoloration or the absence of paint in the area below the leaks. The nature of any leaks found should be carefully determined. If there are any indications that a leak is believed to be due to a crack, the tank should be removed from service as soon as possible, and a complete inspection should be made to determine the repairs required. Crack-like flaws can be found at the connection of nozzles to the tank, in welded seams, and in the metal ligament between rivets or bolts, between a rivet or bolt and the edge of the plate, at the connection of brackets or other attachments to the tank, and at the connection of the shell to the bottom of a welded tank. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

66. 7 66 Title of the presentation - DD/MM/YY Deformation can be caused by settlement of the tank, wind, earthquake, internal pressure in the tank due to defective vents or relief valves, an operating or induced vacuum in the tank, severe corrosion of the shell, movement of connected piping, improper welding repair methods, and other mechanical damage. Settlement or frost heave of the soil beneath a tank bottom can cause deformation of the shell at the bottom edge. When a welded tank has significant deformations, weld seams may be highly stressed and can crack. The joints most susceptible to cracking are those at connections, at the bottom to shell joint, at floating-roof deck lap seams, the shell-to-roof joint, and at vertical shell seams. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

67. 7 67 Title of the presentation - DD/MM/YY 7.2.8.6 Rivet Inspection If the tank is of riveted or bolted construction, a number of randomly selected rivets or bolts should be checked for tightness. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

68. 7 68 Title of the presentation - DD/MM/YY 7.2.9 Tank Roof Inspection The roof or top head of a tank can be inspected for significant thinning by ultrasonic thickness examination or even by MFL scanning (if the roof condition is thought sound enough to withstand the weight of the equipment). Hammer testing may dislodge scale from the internal plate surfaces into stored product and is not a recommended method of establishing roof plate integrity for personnel loading. Suitable fall protection should be used when working on roofs. In general, the inspector should always walk on weld seams if they are present, because of the extra thickness available to support body weight. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

69. 7 69 Title of the presentation - DD/MM/YY 7.2.9 Tank Roof Inspection Excessive gaps between the shell and the seal (s) of a floating roof can indicate improper seal installation, altered seal condition due to tank operations or long-term wear and tear or a malfunctioning seal (s) due to external influences (earthquake, high winds, snow and ice). Visual inspection may be adequate to determine seal condition, and corrections may be possible while the tank is in service. If permanent repairs cannot be made, the defective areas and any temporary repairs should be noted in the records so that permanent repairs can be made when the tank is removed from service. Seal damage can occur if the maximum operating level is exceeded when portions of the seal are pushed up above the top angle or plate edge. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

70. 7 70 Title of the presentation - DD/MM/YY 7.2.9 Tank Roof Inspection Drainage systems on floating roofs should be inspected frequently for leakage or blockage. If the drains are blocked, an accumulation of liquid can cause floating roofs to sink or to be severely damaged. Proper operation of check valves in drainage sumps should be verified on a regular schedule, especially for those in fouling or corrosive service. Platforms and guardrails on a roof should be checked carefully in the same manner as described earlier for stairways and ladders. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

71. 7 71 Title of the presentation - DD/MM/YY 7.2.10 Auxiliary Equipment Inspection Tank pipe connections and bolting at each first outside flanged joint should be inspected for external corrosion. Visual inspection combined with scraping and picking can reveal the extent of this condition. The soil around the pipe should be dug away for 6 in. - 12 in. (150 mm - 300 mm) to allow for inspection. Flame arrestors should be opened at appropriate intervals, and the screens or grids should be visually inspected for cleanliness and corrosion. Bees and mud daubers occasionally plug arrestors. Other auxiliary equipment should be inspected to ensure that it is in an operable and safe condition. Methods of Inspection EXTERNAL INSPECTION OF AN IN-SERVICE TANK

72. EXTERNAL INSPECTION OF 72 Title of the presentation - DD/MM/YY OUT-OFSERVICE TANKS EXTERNAL INSPECTION OF OUT-OFSERVICE TANKS External Tank Bottom Inspection Tank bottoms that rest on pads or on soil can be reliably inspected for soil-side corrosion using inspection technology developments such as magnetic flux leakage (MFL) bottom scanners or robotic inspection equipment. With these developments, tunnelling under or completely lifting a tank just for soil-side bottom inspection should normally be avoided. It should be remembered that inspection of a tank by lifting may necessitate a hydrostatic test that would be unnecessary with other methods. As it is difficult to refill a tunnel properly, tunnelling should be applied only to locations near the edge of the tank. Clean sand or washed gravel are the best types of fill material. 7 Methods of Inspection

73. 7 73 Title of the presentation - DD/MM/YY Methods of Inspection EXTERNAL INSPECTION OF OUT-OFSERVICE TANKS External Pipe Connection Inspection same as when the tank is in service (see 7.2.5). External Tank Roof Inspection All roof plates should be checked for thickness, regardless of the external appearance. The inside surface of the roof plates may be susceptible to rapid corrosion because of the presence of corrosive vapors, water vapor, and oxygen. The interiors of the pontoons or double decks on floating roofs should be inspected visually. Metal thickness measurements should also be taken. A bright, portable light (of at least 100 lumens) will be needed for this work. Coupons approximately 12 in. X12 in. (300 mm X 300 mm) in size can also be removed from the roof to check for under-side corrosion and rafter condition. All coupons should be round or have rounded corners; no square-cornered coupons should be cut.

74. 7 74 Title of the presentation - DD/MM/YY Methods of Inspection EXTERNAL INSPECTION OF OUT-OFSERVICE TANKS 7.3.3 External Tank Roof Inspection All seals should be inspected visually for corroded or broken parts and for worn or deteriorated vapor barriers. Any exposed mechanical parts-such as springs, hanger systems and other tensioning devices, and Shoes-are susceptible to mechanical damage, wear, and atmospheric or vapor space corrosion. Most floating-roof tanks are equipped with guides or stabilizers to prevent rotation. These guides are subject to corrosion, wear, and distortion and should be inspected visually. If the guides are distorted or the roof is no longer in alignment with these guides, the roof may have rotated excessively. The shell should then be inspected for deformations or other defects as previously outlined in this section.

75. 7 75 Title of the presentation - DD/MM/YY Methods of Inspection EXTERNAL INSPECTION OF OUT-OFSERVICE TANKS 7.3.4 Valve Inspection All valves on the tank should be inspected when the tank is out of service. If leakage or significant deterioration is noted, consideration should be given to valve replacement while the tank is out of service. Valves can be refurbished if there is sufficient time during the out-of- service period but this option could affect the return to service schedule for the tank. Water draw-off valves should be inspected to determine their condition. Bonnet and flange bolts should be examined to ensure that they have not significantly corroded and that they are tight and have proper engagement length.

76. 7.4 INTERNAL INSPECTION 7.4.1 Precautions The tank must be emptied of liquid, freed of gases, and washed or cleaned out as appropriate for the intended inspection. Appropriate certification of the tank for personnel entry and inspection work should be part of the permit process. Many tanks that are cleaned after removal from service are not completely gas-free or product free unless particular attention is paid to areas where hydrocarbon build-up can be overlooked otherwise. Such areas include fixed roof support columns, floating-roof legs, and guide poles all fabricated from pipe or other closed sections without drainage holes and bearing pads or striker pads on the bottom that may have leak paths (exhibited by product weeping). Diffusers and other internal piping extensions inside the tank open to the product can retain product in the piping inverts and should also be completely drained and cleaned, and made otherwise safe prior to inspection work. 76 Title of the presentation - DD/MM/YY INTERNAL INSPECTION 7 Methods of Inspection

77. 7 77 Title of the presentation - DD/MM/YY 7.4.2 Preliminary Visual Inspection Visual inspection is important for safety reasons since the condition of the roof or top head and any internal supports should be established first. The vapor space, the liquid-level line, and the bottom are areas where corrosion will most likely be found. If large areas are severely corroded, it may be best to have them water or abrasive-blasted. From a personnel safety or equipment operability standpoint, it may be necessary to remove light coatings of oil or surface rust. Inspectors should also be alert to accumulation of dry pyrophoric (self-igniting when exposed to ambient conditions) material that may ignite during inspection. These accumulations may occur on the tank bottom, in the seal rim space areas, or on the top of rafters. Such accumulations that cannot be cleaned out prior to inspection should be kept moist to reduce the potential for ignition. Methods of Inspection INTERNAL INSPECTION

78. 7 78 Title of the presentation - DD/MM/YY 7.4.3 Types and Location of Corrosion The vapor space above the stored liquid can be an area of significant corrosion. This is caused by the presence of corrosive vapors, such as hydrogen sulfide, mixed with moisture and air. The vapor-liquid interface is another region that may be subject to accelerated corrosion, especially when fluids heavier than water are stored. When the stored fluid contains acid salts or compounds, they may settle to the bottom of the tank; and if water is present, a weak (corrosive) acid will form. Pitting-type corrosion can occur in the top of tanks directly under holes or openings where water can enter. The weld heat affected zone (HAZ) has been found to corrode at an accelerated rate in relation to the surrounding shell plate material. Methods of Inspection INTERNAL INSPECTION

79. 7 79 Title of the presentation - DD/MM/YY 7.4.3 Types and Location of Corrosion Among other types of deterioration that can occur on the shells of storage tanks are hydrogen blistering, caustic stress corrosion cracking, galvanic corrosion between dissimilar metals in close proximity, and mechanical cracking. These types of deterioration occur less frequently on the roofs and bottoms of tanks. Carbon steel that contains slag inclusions and laminations is more susceptible to hydrogen blistering. Caustic stress corrosion cracking may occur in tanks storing caustic products. Hot, strong caustic can also cause accelerated general corrosion. Areas of residual stresses from welding or areas highly stressed from product loading are most susceptible to caustic corrosion. Such corrosion thrives when the temperature rises above 150ºF (65ºC) and is most likely to occur around heating coil connections at the tank wall or at piping supports on the bottom. Methods of Inspection INTERNAL INSPECTION

80. 7 80 Title of the presentation - DD/MM/YY 7.4.4 Tank Bottoms Good lighting is essential for a quality visual inspection. A minimum 100-watt halogen light is usually adequate, but more light is better. Magnetic flux leakage (MFL) inspection devices can be used to rapidly scan for metal loss in the tank bottom plates. Statistical methods are also available for assessing the probable minimum remaining metal thickness of the tank bottom, and the methods are based on a sampling of thickness scanning data. The number of measurements taken for a statistical sampling will depend on the size of the tank and the degree of soil-side corrosion found. Typically, 0.2% - 10% of the bottom should be scanned randomly. The collection of thickness data is required to assess the remaining bottom thickness. In addition, the outer circumference next to the shell should be included in the statistical sampling. Methods of Inspection INTERNAL INSPECTION

81. 7 81 Title of the presentation - DD/MM/YY 7.4.4 Tank Bottoms Seams of riveted tanks can be checked by running a thin-bladed scraper or knife along the riveted seam. Representative sections or coupons (minimum size 12 in. [300 mm] each way) may be taken to confirm the results of magnetic flux leakage or ultrasonic examinations. The increasing accuracy of magnetic flux leakage, ultrasonic scanning, and other automated methods makes coupon removal less useful, especially considering the time and expense associated with replacing the coupons. Coupons may be advisable in assessing the root cause of soil-side corrosion. If settlement is detected (internally or externally), the magnitude of the settlement should be measured. (API Std 653, Appendix B, provides guidelines for evaluation of tank bottom settlement.) Methods of Inspection INTERNAL INSPECTION

82. 7 82 Title of the presentation - DD/MM/YY 7.4.4 Tank Shell The area of highest stress in flat bottom tanks is commonly at the shell-to-bottom joint detail and this area can be susceptible to corrosion. Close visual inspection for this area should be done for evidence of corrosion or other defects. It should be noted that a riveted shell to bottom joint using a structural angle detail is considered a mechanical joint, not a welded joint, and may not be suitable for certain types of examination. Methods of Inspection INTERNAL INSPECTION

83. 7 83 Title of the presentation - DD/MM/YY 7.4.6 Testing for Leaks The hydrostatic test will be the best method for detecting shell leaks. If a hydrostatic test is not to be made, a penetrating oil (such as diesel or automobile spring oil) can be sprayed or brushed on one side of the shell plate in suspect areas and the other side can then be observed for leakage. The liquid penetrant method used for finding cracks can also be used in much the same manner, with the penetrant applied to one side of the plate and the developer applied to the other side. For either method, approximately 24 hours may be required for leaks to become evident. Tank bottom leak detection methods are described in Section 8. Methods of Inspection INTERNAL INSPECTION

84. 7 84 Title of the presentation - DD/MM/YY 7.4.7 Linings Special inspection methods may be needed when the inside surfaces of a tank are lined with a corrosion resistant material such as steel or alloy steel cladding, rubber or other synthetic fabric, organic or inorganic coatings, glass, or concrete (see API RP 652). To avoid mechanical damage to the linings, considerable care should be taken when working inside tanks lined with rubber, synthetics, glass, or organic or inorganic coatings. Glass-lined tanks are especially susceptible to severe damage that cannot be easily repaired. Concrete linings are difficult to inspect adequately, primarily because the surface is porous. Concrete-lined steel bottoms are impractical to inspect unless the concrete is removed. Methods of Inspection INTERNAL INSPECTION

85. 7 85 Title of the presentation - DD/MM/YY Roof and Structural Members If corrosion is noted on the roof and upper shell, then structural members may also be thinning, possibly at as much as twice the rate of the thinning of the roof or shell, since both sides of the structural members are exposed to the corrosive vapors. ( API Std 653, Appendix C). Internal Equipment Pipe coils, coil supports, swing lines, nozzles, and mixing devices should be visually inspected. Methods of Inspection INTERNAL INSPECTION

86. 7.5 TESTING OF TANKS When storage tanks are built, they are tested in accordance with the standard to which they were constructed. The same methods can be used to inspect for leaks and to check the integrity of the tank after repair work. When major repairs or alterations have been completed, such as the installation of anew tank bottom or the replacement of large sections of shell plate, the test requirements are specified in API Std 653, Section12. Consideration should also be given to the notch toughness of the shell material at the air and water temperatures existing at the time of the test. A discussion of notch toughness and brittle fracture can be found in API RP 571 and in API Std 653, Section 5. 86 Title of the presentation - DD/MM/YY TESTING OF TANKS 7 Methods of Inspection

87. TESTING OF TANKS If water is not available and if the roof of the tank is reasonably air tight or can be made so, a carefully controlled air test using air pressure not exceeding 2 in. (0.50 kPa) of water pressure may be applied. This type of test is of very little use as a strength test and is used only in inspection for leaks. INSPECTION CHECKLISTS API Std 653, Appendix C provides sample checklists of items for consideration when conducting external and internal inspections. 87 Title of the presentation - DD/MM/YY 7 Methods of Inspection TESTING OF TANKS

88. TANK ASSESSMENT 88 8

89. Purpose of assessment: To ensure suitability for continued /change of service. To make decisions - repairs, alterations, dismantling, relocation or reconstruction. Factors to be considered in the assessment: a) Internal corrosion (product/water at the bottom) b) External corrosion. c) Stress levels and allowable stress levels; d) Properties of products: specific gravity, temperature, and corrosivity; e) MDMT. TANK ASSESSMENT OVERVIEW TANK ASSESSMENT 8 89

90. f) Roof - live load, wind, and seismic load. g) Foundation, soil, and settlement. h) Chemical/mechanical properties of tank material. i) Distortions of the existing tank; Operating conditions-rate/frequency of filling / emptying. Tank Roof Evaluation Repair is required when Roof is corroded to an average thickness < 0.09” in any 100 Sq Inch area. There is a through hole in the plates. TANK ASSESSMENT TANK ASSESSMENT 8 90

91. FIXED ROOFS Roof support members (rafters, girders, columns, and bases ) shall be inspected for soundness. Distorted (such as out-of-plumb columns), corroded, and damaged members shall be evaluated/repaired/ replaced if necessary . Particular attention-of severe internal corrosion of pipe columns. Frangible roof: evaluation of roof to shell joint for compliance. ROOF ASSESSMENT TANK ASSESSMENT 8 91

92. FLOATING ROOFS Cracks/punctures/holes in roof plates and pontoons shall be repaired/affected areas replaced. Pitted areas shall be evaluated & the affected areas shall be repaired or replaced . 3. Roof support systems, perimeter seal systems, appurtenances such as a rolling ladder, anti-rotation devices , water drain systems, and venting systems shall be evaluated for needed repairs or replacements . ROOF ASSESSMENT TANK ASSESSMENT 8 92

93. TANK SHELL EVALUATION Flaws , deterioration, or other conditions (e.g. change of service, re-location , corrosion, the original CA) that might adversely affect the performance or structural integrity of the shell must be evaluated and a determination made regarding suitability for intended service . Isolated minor pitting - normally not a concern.. API 653 -provides methods to evaluate general corrosion and pitting. (For other deteriorations- API 579/API 580) SHELL EVALUATION TANK ASSESSMENT 8 93

94. What is pitting? Pitting is defined as localized regions of metal loss that can be characterized by a pit diameter on the order of the plate thickness or less, and a pit depth that is less than the plate thickness. (Source API 579 Clause 6.1) ---------------------------------------------------------------------- What is general corrosion? May be uniform corrosion.(uniform metal loss) What is Localized corrosion or local metal loss (Local Thin Area-LTA)? Local metal loss on the surface of the component; the length of a region of metal loss is the same order of magnitude as the width. (Source API 579 clause 5.2) SHELL EVALUATION TANK ASSESSMENT 8 94

95. EVALUATION OF GENERAL CORROSION IN SHELL PLATES. Actual Thickness Determination: For each corroded area , determine the minimum thickness (t₂ ) excluding widely scattered pits in the corroded area. Calculate the critical length (L) ( L ≤ 40”) L = 3.7 x √ D t₂ D = diameter of the tank (in feet) t₂ = least thickness, in inches. Measure thickness along the vertical planes (minimum five equally spaced readings per plane) SHELL EVALUATION TANK ASSESSMENT 8 95

96. Determine ‘average value’ of the readings in each plane. 8. The least of averages = t₁ (inches) The criteria for continued operation: t₁ ≥ tmin + CA required until the next inspection. t₂ ≥ 60 % of tmin + CA required until the next inspection. SHELL EVALUATION TANK ASSESSMENT 8 96

97. EVALUATION OF WIDELY SCATTERED PITS Widely scattered pits may be ignored when: The remaining thickness under the pit shall be ≥ one-half the minimum acceptable tank shell thickness The sum of their dimensions along any vertical line is ≤ 2” in an 8” length. SHELL EVALUATION TANK ASSESSMENT 8 97

98. SHELL EVALUATION TANK ASSESSMENT 8 98

99. The minimum shell thickness is calculated as below.(method applicable to dia. ≤ 200’ only). ----------------------------------------------------------------------- a) minimum thickness of an entire shell course: tmin = [2.6 (H-1)DG] / SE -------------------------------------------------------------------------- b) minimum thickness at a locally thinned area or any other location of interest. tmin = [2.6 HDG] / SE -------------------------------------------------------------------------- tmin = minimum acceptable thickness, in inches for each course.(not < 0.1” for any course) D = nominal dia. of tank, in feet. G = highest specific gravity of the contents; SHELL EVALUATION TANK ASSESSMENT 8 99

100. H = height from the bottom of the shell course under consideration to the maximum liquid level when evaluating an entire shell course, in feet. or height from the bottom of the length L (see 4.3.2.1) from the lowest point of the bottom of L of the locally thinned area to the maximum liquid level, in feet. or height from the lowest point within any location of interest to the maximum liquid level, in feet (ft); SHELL EVALUATION TANK ASSESSMENT 8 100

101. S = maximum allowable stress in psi.(Listed in Table 4.1 ) NOTE : for reconstructed tanks, S value is from the current applicable standard; E = the original joint efficiency for the tank. (Table 4.2 if original E is unknown) E = 1.0 when evaluating the retirement thickness in a corroded plate, away from welds or joints by at least the greater of 1 in. or twice the plate thickness. SHELL EVALUATION TANK ASSESSMENT 8 101

102. If the tank will be hydrostatically tested, the hydrostatic test height, Ht, shall be limited by one of the following methods. The tank shall not be filled above the level determined by the lesser value of Ht determined below. After determining the controlling thickness of an entire shell course, Ht calculated as follows: SHELL EVALUATION TANK ASSESSMENT 8 102

103. b) After determining the controlling thickness by 4.3.2.1 for a locally thinned area, or at any other location of interest within a shell course, Ht is calculated as follows: SHELL EVALUATION TANK ASSESSMENT 8 103

104. Ht = the height from the bottom of the shell course under consideration to the hydrostatic test height when evaluating an entire shell course in feet; or the height from the bottom of the length, L, for the most severely thinned area in each shell course to the hydrostatic test height in feet; or is the height from the lowest point within any other location of interest to the hydrostatic test height in feet; St = max. allowable hydrostatic test stress in psi (Table 4.1) SHELL EVALUATION TANK ASSESSMENT 8 104

105. NOTE : For reconstructed tanks, St value is from current applicable standard. Alternatively, the minimum shell thickness of tanks dia. ≤ 200 ft may be calculated using variable design point method. SHELL EVALUATION TANK ASSESSMENT 8 105

106. SHELL EVALUATION TANK ASSESSMENT 8 106

107. DISTORTIONS Shell distortions: 1. Out-of-roundness, 2. Buckled areas, 3. Flat spots, (measured in vertical plane) Causes of shell distortions: 1. Foundation settlement, 2. Over or under pressuring, 3. High wind, 4. Poor shell fabrication, or repair techniques, etc. Shell distortions shall be evaluated on an individual basis. SHELL EVALUATION TANK ASSESSMENT 8 107

108. FLAWS Flaws: Cracks or laminations -thorough examination and evaluation to determine nature and extent and need for repair. If repair needed-develop/implement repair procedure. Scars (arc strikes, gouges, or tears from temporary attachment welds)- evaluation case-by-case basis. 4. Cracks in the shell-to-bottom weld shall be removed. SHELL EVALUATION TANK ASSESSMENT 8 108

109. Wind Girders and Shell Stiffeners Degradation by corrosion renders these elements inadequate for the design conditions. Shell Welds Deteriorated welds due to corrosion or pitting must be evaluated and appropriate repair procedures established or the tank rerated as necessary. ASSESSMENT TANK ASSESSMENT 8 109

110. SHELL PENETRATIONS The condition and details of existing shell penetrations (nozzles, man-ways, cleanout openings, etc.) shall be reviewed when assessing the integrity of an existing tank shell. Existing shell welds that are not modified or affected by repairs and are closer than required by API 650 (7 th or later edition) are acceptable when no defects noted by MPI. Nozzle wall thickness shall be evaluated for pressure and all other loads. SHELL EVALUATION TANK ASSESSMENT 8 110

111. TANK BOTTOM EVALUATION General Tank bottom is assessed 1. To prevent leakage causing environmental damage. 2. Each aspect of corrosion phenomena, and other potential leak or failure mechanism must be examined. 3. Excessive foundation settlements affect the integrity of shells and bottoms. 4. Monitoring the settlement is a recognized practice to assess the integrity. BOTTOM ASSESSMENT TANK ASSESSMENT 8 111

112. CAUSES OF BOTTOM FAILURE: a) Product side/soil side corrosion (thinning, pitting.) b) Corrosion of weld joints (weld/HAZ) c) Weld joint cracking. d) Stresses on the bottom plates due to Roof support loads and shell settlement; e) Inadequate drainage under the tank bottom; f) The lack of an annular plate ring when required; g) Uneven settlement (high localized stresses in The bottom plates) BOTTOM ASSESSMENT TANK ASSESSMENT 8 112

113. h) Roof support columns or other supports welded to the tank bottom where adequate allowance for movement was not made; i) Rock or gravel foundation pads with inadequately filled-in surface voids; j) Non-homogeneous fill under the bottom (a lump of clay in a sand foundation); k) Inadequately supported sumps. BOTTOM ASSESSMENT TANK ASSESSMENT 8 113

114. Tank Bottom Release Prevention Systems (RPSs) Purpose: to maintain tank integrity/protect the environment. These include: Internal inspection of tank bottom; Leak detection systems and leak testing of the tank; Cathodic protection Lining interior Providing a release prevention barrier (RPB) or Combination of these measures, depending on the operating environment and service of the tank. Internal Inspection To assess the bottom integrity and identify conditions that may lead to future loss of integrity. BOTTOM ASSESSMENT TANK ASSESSMENT 8 114

115. Leak Detection Systems and Leak Testing Purpose: to identify, quantify, and/or locate a tank bottom failure not detectable visually. Release Prevention Barriers (RPBs) Includes - steel bottoms, synthetic materials, clay liners, concrete pads, etc placed under a tank, Functions of RPB: prevents the escape of released material, contains or channels the released material for leak detection. BOTTOM ASSESSMENT TANK ASSESSMENT 8 115

116. BOTTOM PLATE THICKNESS MEASUREMENTS Magnetic flux leakage (MFL) and UTG - commonly used. UTG is to confirm and quantify MFL data. The quality of the data depends on 1. personnel, 2. equipment 3. procedures. BOTTOM ASSESSMENT TANK ASSESSMENT 8 116

117. METHOD TO CALCULATE THE MINIMUM ACCEPTABLE THICKNESS OF THE BOTTOM/PORTIONS MRT = min. remaining thickness at the end of interval Or . MRT = (Minimum of RTbc or RTip) – Or (StPr + Upr) Or = in-service interval of operation (years to next internal inspection) RTbc = min. remaining thickness from ‘bottom side corrosion’ after repairs; BOTTOM ASSESSMENT TANK ASSESSMENT 8 117

118. RTip = min.remaining thickness from ‘internal corrosion’ after repairs; StPr = max. rate of corrosion not repaired on the top side. StPr = 0 for coated areas of the bottom. UPr = max. rate of corrosion on the bottom side. UPr = 0 for areas that have effective CP. BOTTOM ASSESSMENT TANK ASSESSMENT 8 118

119. UNLESS A STRESS ANALYSIS IS PERFORMED, the minimum bottom plate thickness in the critical zone shall be the smaller of 1. Half the original bottom thickness (excluding CA) 2. 50 % of tmin of the lower shell course, (but not < 0.1”) Isolated pitting will not affect the strength appreciably. The thickness at the toe of the outside bottom-to-shell weld shall be ≥ 0.1” The projection of the bottom beyond the outside toe of the shell-to-bottom weld shell shall be ≥ 3/8”. BOTTOM ASSESSMENT TANK ASSESSMENT 8 119

120. BOTTOM ASSESSMENT TANK ASSESSMENT 8 120

121. MINIMUM THICKNESS FOR ANNULAR PLATE RING The annular ring is required to increase strength The min.thickness of annular ring is usually > 0.1”. Unless a stress analysis is performed, the annular plate thickness shall be in accordance with 4.4.6.2 or 4.4.6.3, as applicable. Case 1: Specific gravity < 1 (refer to clause 4.4.6.2) Case 2: Specific gravity ≥ 1 (refer to clause 4.4.6.3) BOTTOM ASSESSMENT TANK ASSESSMENT 8 121

122. Case 1: 4.4.6.2 - product specific gravity < 1.0, - annular plate is required for other than seismic loading. - the thickness of the annular plates shall be not be < than the thicknesses given in Table 4.5 , plus CA. BOTTOM ASSESSMENT TANK ASSESSMENT 8 122

123. THICKNESS EXCLUDING CORROSION ALLOWANCE BOTTOM ASSESSMENT TANK ASSESSMENT 8 123

124. Case 2: 4.4.6.3 - specific gravity ≥ 1.0. - annular plate is required for other than seismic loading - the thickness of the annular plates shall be in accordance with API 650, Table 5-1, plus CA. BOTTOM ASSESSMENT TANK ASSESSMENT 8 124

125. API 650 TABLE 5-1 a BOTTOM ASSESSMENT TANK ASSESSMENT 8 125

126. API 650 TABLE 5-1 b BOTTOM ASSESSMENT TANK ASSESSMENT 8 126

127. TANK FOUNDATION EVALUATION Principal causes of foundation deterioration Settlement Erosion, Cracking, and Deterioration of concrete initiated by: calcining, attack by underground water, attack by frost, and attack by alkalies and acids. FOUNDATION ASSESSMENT TANK ASSESSMENT 8 127

128. MECHANISMS OF CONCRETE DETERIORATION Calcining (loss of water of hydration) -exposure to sufficiently high temperature for a period of time. -during intermediate cooling, the concrete absorbs moisture, swells, loses its strength, and cracks. b) Deterioration of concrete exposed to underground water can be caused by Chemical attack, Cyclic changes in temperature, and Freezing moisture; FOUNDATION ASSESSMENT TANK ASSESSMENT 8 128

129. Expansion of freezing moisture in porous concrete or concrete with minor settlement causes cracks. Temperature cracks: can result in spalling and/or the development of serious structural cracks; sulfate-type alkalies, and to a lesser extent, chlorides, can act corrosively to destroy the bond of the concrete ; FOUNDATION ASSESSMENT TANK ASSESSMENT 8 129

130. temperature cracks (hairline cracks of uniform width) do not seriously affect the strength of the concrete foundation structure; however, these cracks can be potential access points for moisture or water seepage that could eventually result in corrosion of the reinforcing steel. FOUNDATION ASSESSMENT TANK ASSESSMENT 8 130

131. Failure of a tank due to brittle fracture occurs, either 1. During first hydrostatic test or on the first filling in cold weather, 2. After a change to lower temperature service, or after a repair/ alteration. So once a tank has demonstrated the ability to withstand the combined effects of maximum liquid level (highest stresses) and lowest operating temperature without failing, the risk of failure due to brittle fracture with continued service is minimal. BRITTLE FRACTURE ASSESSMENT TANK ASSESSMENT 8 131

132. Tanks fabricated from steels of unknown material specifications, thicker than 1/2 in. and operating at a shell metal temperature below 60 °F, can be used if the tank meets the requirements of Figure 5.2. The original nominal thickness for thickest tank shell plate shall be used for the assessment. For unheated tanks, the shell metal temperature shall be the design metal temperature. BRITTLE FRACTURE ASSESSMENT TANK ASSESSMENT 8 132

133. BRITTLE FRACTURE ASSESSMENT TANK ASSESSMENT 8 133

134. Tank Repairs & Alterations 134 9 134

135. All repairs must be authorized by AI or storage tank engineer prior to commencement by a repair organization. Authorization for alterations may not be given without prior consultation with, and approval by the engineer The AI - shall designate hold points. - shall specify minimum documentation on completion. - may give prior general authorization for limited or routine repairs not requiring hydrostatic test or an engineering evaluation. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 135

136. All proposed design, work execution, materials, welding procedures, examination, and testing methods must be approved by the AI or by an engineer. The AI or an engineer shall approve all specified repair and alteration work at the designated hold points and after repairs and alterations have been completed in accordance with the requirements of this standard. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 136

137. REMOVAL AND REPLACEMENT OF SHELL PLATE MATERIAL The min. thick of the replacement shell plate shall be calculated in accordance with the as-built standard. The thickness of the replacement shell plate shall not be less than the greatest nominal thickness of any plate in the same course adjoining the replacement plate except where the adjoining plate is a thickened insert plate. The minimum size of a replacement shell plate- - greater of 12” or 12 x thickness of the replacement plate. (rounded corners of Radius) a. 6” for t ≤ 0.5” b. greater of 6”or 6t for t > 0.5” TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 137

138. Prior to welding the new vertical joints, the existing horizontal welds shall be cut for a minimum distance of 12 in. beyond the new vertical joints. The vertical joints shall be welded prior to welding the horizontal joints. Weld the shell-to-bottom weld last. The areas to be welded shall be ultrasonically inspected for defects and remaining thickness. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 138

139. Lapped patch repair plates may be used for the closure of holes caused by the removal of existing shell openings or the removal of severely corroded or eroded areas. to reinforce areas of severely deteriorated shell plates that are not able to resist the service loads. 3. for shell plates that are below the retirement thickness. 4. to repair small shell leaks, or minimize the potential from leaks from severely isolated or widely scattered pitting. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 139

140. The repair plate thickness selection shall be based on a design that conforms to the as-built standard and API 653, using a joint efficiency not exceeding 0.70. The minimum repair plate dimension shall be 4” with a minimum overlap of 1” and a maximum overlap of 8 times the shell thickness (8 t). The repair plate thickness shall not exceed the nominal thickness of the shell plate adjacent to the repair. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 140

141. The repair plate thickness shall be based on a design that conforms to the as-built standard and API 653, using a joint efficiency not > 0.35. The repair plate thickness shall not exceed the shell plate thickness at the perimeter of the repair plate by more than one-third, but no more than 1/8 in. The repair plate thickness not to exceed ½”. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 141

142. The remaining strength of the deteriorated areas under the repair plate shall not be considered in the calculation of service or hydro-test loads. Lapped patch repair plates may be used to repair small shell leaks, or minimize the potential from leaks from severely isolated or widely scattered pitting if the following requirements are satisfied. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 142

143. REPAIR OF DEFECTIVE WELDS Cracks, lack of fusion, and rejectable slag and porosity needing repair shall be removed completely by gouging and/or grinding and the resulting cavity properly prepared for welding. Generally, it is not necessary to remove existing weld reinforcement in excess of that allowed by API 650 when discovered on an existing tank with a satisfactory service history. Existing weld undercut deemed unacceptable shall be repaired by additional weld metal, or grinding, as appropriate. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 143

144. Welded joints that have experienced loss of metal due to corrosion may be repaired by welding. Arc strikes discovered in or adjacent to welded joints shall be repaired by grinding and/or welding. Arc strikes repaired by welding shall be ground flush with the plate. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 144

145. REPAIR OF SHELL PENETRATIONS Repairs to existing shell penetrations shall be in compliance with API 650. Reinforcing plates may be added to existing unreinforced nozzles when deemed appropriate The reinforcing plate shall meet all dimensional and weld spacing requirements of API 650. As an alternative, the reinforcing plates may be added to the inside of the tank provided that sufficient nozzle projection exists. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 145

146. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 146

147. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 147

148. ADDITION OR REPLACEMENT OF SHELL PENETRATIONS New shell penetrations (addition or replacement) shall be in accordance with material, design, and stress relief requirements of API 650. The required reinforcement area shall be calculated as per API 650, except the variable S shall be the allowable design stress from Table 5-2 of API 650 for the existing shell plate. Use 20,000 psi, for unknown materials. A joint efficiency of 1.0 may be used (see 9.8.5). The variable H shall be the height from the centerline of the penetration to the maximum liquid level, in ft. TANK REPAIR & ALTERATION R e pai r s & Alteration 148

149. The following erection requirements shall be met: if an integral reinforcement design is used, the insert plate at its periphery shall have a 1:4 reduction taper to match the shell plate thickness when the insert plate exceeds the shell plate thickness by more than 1/8 in. b) spacing of welds - in accordance with Figure 9.1 the new insert plate shall be joined to existing shell plate with full penetration and full fusion butt welds. Examinations shall be per Section 12. (and penetrations located on a shell joint shall receive additional radiography. (RT for a length = 3 x diameter of the opening, (API 650,Section 5.7.3.) TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 149

150. Penetrations larger than 2 NPS shall be installed with the use of an insert plate if the shell plate thickness is greater than 1/2 in. and the shell plate material does not meet the current design metal temperature criteria. In addition, the following requirement shall be met: the minimum diameter of the insert plate shall be at least twice the diameter of the penetration or the diameter plus 12 in., whichever is greater; b) when reinforcing plates are used, the minimum diameter of the insert plate shall equal the diameter of the reinforcing plate plus 12 in. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 150

151. ALTERATION OF EXISTING SHELL PENETRATIONS Alteration shall comply with API 650. Installation of a new tank bottom above the existing bottom, may require alteration of existing penetrations in the bottom course. The existing reinforcing plate may be trimmed to increase the spacing between the welds provided that the altered detail complies with the requirements of API 650. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 151

152. The existing re-pad may be removed and a new one added.(re-pad is not permitted on existing stress relieved assemblies.) When not known that the assembly was stressed relieved, then the alteration shall meet the requirements of API 650,(Section 5.7.4.-thermal relief) When the upper half of the existing re-pad meets all requirements of API 650, it can be left in place with approval of the purchaser. Only the lower half of the existing re-pad need be removed and replaced with the new one. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 152

153. The new re-pad is provided with a new telltale hole if needed. The shell plate thickness under the telltale hole shall be checked after drilling and the thickness shall not be less than 1/2 tmin plus any required CA. The welds to be replaced around the perimeter of the reinforcing plate and between the reinforcing plate and neck of the penetration shall be completely removed by gouging and grinding. The new reinforcing plate shall be in accordance with Figure 9.3. If required to maintain weld spacing, a tombstone shaped reinforcing plate may be used (see Figure 9.4). TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 153

154. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 154

155. 155 TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 155

156. The existing penetration may be moved by cutting the section of the shell containing the fitting and reinforcing plate, and raising the entire assembly to the correct elevation (see Figure 9.5). TANK REPAIR & ALTERATION R e pai r s & Alteration 156

157. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 157

158. REPAIR OF TANK BOTTOMS Welded-on patch plates permitted within certain limitations. (Fig 9.9 - acceptable details) The min. dimension of the plate that overlaps a bottom seam or existing patch is 12 in. May be of any shape with rounded corners (minimum radius of 2 inch) A smaller welded-on patch diameter ≥ 6 inch is permitted 1. if it does not overlap a bottom seam; 2. it is not placed fully or partially over an existing patch; and 3. it extends beyond the corroded bottom area, if any, by at least 2 in. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 158

159. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 159

160. REPAIRS WITHIN THE CRITICAL ZONE a) Max. plate thickness is ¼” and must meet toughness requirements of API 650. b) When a welded-on patch plate is within 6 in. of the shell, the welded-on patch plate shall be tombstone shaped. c) Welds- min two-pass and examination of each pass –visual and PT or MT. d) Installation of a welded-on patch plate by butt-welding to an adjacent existing patch is not permitted. e) Patch plates over existing patches are not allowed in the critical zone. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 160

161. Patch plates -NOT permitted in the critical zone when the operating temperature exceeds 200 °F for CS or 100 °F for SS. If more extensive repairs are required within the critical zone the bottom plate welded to the shell shall be replaced. The shell-to-bottom weld shall be removed and replaced for a minimum distance of 12 in. on each side of the new bottom plate. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 161

162. Welded-on patch plates not meeting the requirements are permitted if the repair method has been reviewed and approved by an engineer. The review shall consider brittle fracture, stress due to settlement, stress due to shell bottom discontinuity, metal temperature, fracture mechanics, and the extent and quality of NDE. Unacceptable indications such as cracks, gouges, tears, and corroded areas in bottom plates, located outside the critical zone, may be repaired by deposition of weld metal. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 162

163. The repair of corroded plates in the critical zone is limited to pit welding or overlay welding under the following conditions. The sum of the pit dimensions along an arc parallel to the shell-to-bottom joint does not exceed 2 in. in an 8-in. length. b) There must be sufficient thickness (at least 0.1”) for completion of a sound weld and to avoid burn through. A lesser thickness is permitted only if reviewed and approved by an engineer . c) All weld repairs shall be ground flush and be examined.(root/final pass by PT or MT. Additionally annular butt final pass by UT.) TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 163

164. REPLACEMENT OF TANK BOTTOM PLATES Suitable noncorrosive material cushion such as sand, gravel, or concrete shall be used between the old bottom and the new bottom. The shell shall be slotted with a uniform cut made parallel to the tank bottom. The new bottom plate shall extend outside the shell as required by API 650. All rules for weld spacing shall be followed. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 164

165. E xisting shell penetrations shall be raised or their re-pads modified if the elevation of the new bottom results in inadequate nozzle reinforcement/ weld space requirements ( as given in API 650.) For floating roof tanks, the support legs can either remain the same or be shortened. New bearing plates for roof support legs and for fixed roof support columns shall be installed. For internal floating roofs with aluminum supports, new austenitic stainless steel or acceptable non-metallic (e.g. Teflon® 6) spacers shall be added to isolate supports from the carbon steel bottom. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 165

166. When removing an existing tank bottom, the tank shell shall be separated from tank bottom either by: cutting the shell parallel to the tank bottom a minimum of 1/2 in. above the bottom-to-shell weld (cut line B-B as shown in Figure 10.1), or b) removing the entire shell-to-bottom attachment weld , including any penetration and HAZ by arc gouging and/or grinding etc. All arc-gouged areas of the tank shell-to-bottom weld shall be magnetic particle examined, and defective areas repaired and re-examined. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 166

167. For tanks with shell plate of unknown toughness , new weld joints in the bottom or annular ring shall be spaced at least the greater of 3 in. or 5t from existing vertical weld joints in the bottom shell course, where t is the thickness of the bottom shell course, in inches. Replacement of portions of an existing tank bottom (entire rectangular plates or large segments of plates) not within the critical zone are permitted under the same rules per API 650. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 167

168. For tank materials having 50,000 psi yield strength or less, existing shell penetrations need not be raised if the following conditions are met. a) For reinforced penetrations, including low-types, a minimum of 4” shall be maintained between the shell-to bottom weld toe and the nearest penetration attachment weld toe (reinforcing plate periphery weld, or nozzle neck weld to low type reinforcing plate and shell welds). b) For self-reinforced penetrations, the greater of 3” or 21/2 t shall be maintained between the shell-to-bottom weld toe and the nearest penetration attachment weld toe. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 168

169. c) The shell-to-bottom weld is to be welded with low hydrogen electrodes and with welding procedures limiting distortion and residual stress. d) The toes of the welds shall be blend-ground to minimize stress concentrations as follows. For circular reinforcing plates, blend-grind the periphery attachment weld from the “four o'clock” position to the “eight o'clock” position. Blend-grind the inside and outside of the shell-to-bottom weld a minimum of one penetration diameter length on either side of the penetration centerline. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 169

170. ii) For diamond-shaped reinforcing plates, blend-grind the lower horizontal length of the diamond shaped attachment weld. Blend-grind the inside and outside of the shell-to-bottom weld a minimum of one penetration diameter length on either side of the penetration centerline. iii) For low-type penetrations, blend-grind the nozzle attachment weld (shell and reinforcing plate) from the “four o'clock” position to the “eight o'clock” position. Blend-grind the inside and outside of the shell-to-bottom weld a minimum of one penetration diameter length on either side of the penetration centerline. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 170

171. e) The blend-ground lengths of welds listed above shall be magnetic particle examined before and after hydrostatic test. Additional Welded-on Plates If other welded-on plates such as wear, isolation, striker, and bearing plates, are to be added to tank bottoms, they shall be installed in accordance with 9.10.1, and examined in accordance with 12.1.7. For these additional welded-on plates, if the lap weld spacing requirements not met, magnetic particle (MT) or Liquid Penetrant (PT) examination is required for the exposed welds or portions of welds failing to meet minimum spacing criteria. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 171

172. Repair of Fixed Roofs Roof repairs shall meet the requirements of API 650 External Floating Roofs Repair method shall restore the roof to a condition enabling it to perform as required. Internal Floating Roofs Repairs as per original construction drawings. If the drawings are not available, the roof to be repaired to App H of 650. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 172

173. Primary Seals Rim-mounted primary shoe seals and toroidal seal systems can be removed, repaired, or replaced. To minimize evaporation losses and reduce potential hazard to the workers, no more than one-fourth of the roof seal system should be removed an in-service tank at one time. Installation of Primary and Secondary Seals. If the roof rim thickness is less than 0.1” thick, it shall be replaced. The new roof rim shall be 3/16-in. thickness, minimum. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 173

174. HOT TAPS (RADIAL HOT TAPS) NOT permitted on shell requiring thermal stress relief. For tank shell plates of recognized toughness, the connection size and shell thickness limitations are shown in Table 9.1. For shell plates of unknown toughness, the following limitations apply. Nozzle dia ≤ NPS 4 The shell plate temperature shall be at or above the minimum shell design metal temperature for the entire hot tapping operation. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 174

175. All nozzles shall be reinforced (per API 650) minimum thick of re-pad = shell thickness. minimum dia of re-pad = dia of cutout + 2” The maximum height of tank liquid above the hot tap location during the hot tapping operation shall be such that the hydrostatic tank shell stress is less than 7,000 lbf /in.2 at the elevation of the hot tap. 5) The minimum height of tank liquid above the hot tap location shall be at least 3 ft during the hot tapping operation. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 175

176. Hot taps a) not permitted on roof or in gas/vapor space. b) not to be installed on laminated/severely pitted shell plate. c) not permitted on tanks where the heat of welding may cause environmental cracking . ( Eg : caustic cracking or SCC.) TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 176

177. TANK REPAIR & ALTERATION 9 R e pai r s & Alteration 177

178. 99 RE C OR D S 10 178

179. 10 179 Title of the presentation - DD/MM/YY Records & Reports GENERAL Good records form the basis of an effective inspection program and allow for properly scheduled inspections. Accurate and complete records help predict when repairs and replacements may be needed, reducing the potential for safety and environmental hazards. RECORDS AND REPORTS API Std 653 A complete record file should consist of at least three types of records: design and construction records, repair/alteration records, and inspection records. R E C O RD S

180. 10 180 Title of the presentation - DD/MM/YY Form & Organization FORM AND ORGANIZATION The report should clearly breakdown the following categories of recommendations: Those areas that require immediate repair or change that are mandatory in order to maintain the continued safety, health and environmental concerns of the facility and that should not be delayed. Those areas that should be repaired to extend the tank life that may fail before the next internal inspection. Those areas that can be deferred until the next internal inspection without jeopardizing health, environment or safety and that the owner/operator wants to defer. Those items that are strictly non-threatening areas of concern such as cosmetic issues, settlement that is within the API Std 653 tolerances. All recommendations should be backed up with supporting calculations, photos and the rationale for such recommendations. R E C O RD S

181. 102 APPENDIX A 11 181

182. 9 182 Title of the presentation - DD/MM/YY Ultrasonic Thickness (UT) Measurement A.1 Ultrasonic Thickness (UT) Measurement Dual-element transducers can have the ability to measure thin sections from 0.050 in.-1.000 in. (1.3 mm Ð 25 mm). Holes in the material or sections of less than 0.050 in. (1.27 mm) measured with too low a frequency will provide either no reading or a false reading. Epoxy coatings have a velocity approximately half that of the steel, so that the ultrasonic tool will read the epoxy coating thickness as twice its actual thickness (0.015 in. [15 mils] epoxy would read as 0.030 in. [30 mils]). Selection of a single-crystal transducer operating in the so- called echo-to-echo mode can prevent this coating thickness error. However, the single-crystal transducer has poor resolution for small diameter deep pits. APPENDIX A

183. 9 183 Title of the presentation - DD/MM/YY Integrity of Repairs Ultrasonic Corrosion Testing (ASME) recommends 10% minimum overlap for readings based on the transducer diameter. Large diameter transducers will not find small diameter deep corrosion pits. Ultrasonic Shear Wave Testing Shear wave inspection can be used to assist in the discrimination between laminations and inclusions in material. Automated shear wave is especially effective for this purpose. The most general application of shear wave transducers is to detect defects in butt- welded joints, usually in lieu of radiography. APPENDIX A

184. 9 184 Title of the presentation - DD/MM/YY Integrity of Repairs Magnetic Flux Leakage Bottom Inspection The user should make sure that the scanner is calibrated properly and has a validation and/or calibration test plate. A primary advantage of these tools is the ability to detect product-side pitting, soil-side corrosion, and holes in the tank bottom in an efficient and economical manner. All of the systems require some additional inspection to quantify detected flaws. Robotic Inspection These robotic crawler devices are designed for total immersion in liquids and have been successful in providing ultrasonic thickness information on tank bottoms in clear finished product storage such as gasoline, naphtha and some crude oil. This equipment needs to be used under carefully controlled circumstances and within API safety guidelines for work on tanks in service. APPENDIX A