Of currently used tank designs, the fixed-roof tank is the least expensive to construct and is generally considered the minimum acceptable equipment for storing VOL's (volatile organic liquids). Most recently built tanks are of all-welded construction and are designed to be both liquid- and vapor-tight. However, older tanks may be of riveted or bolted construction and may not be vapor-tight. A breather valve (pressure-vacuum valve), which is commonly installed on many fixed-roof tanks, allows the tank to operate at a slight internal pressure or vacuum.Breather vents are typically set at 0.19 kPa (0.75 in. w.c.) on atmospheric pressure fixed-roof tanks. Because this valve prevents the release of vapors during only very small changes in temperature, barometric pressure, or liquid level, the emissions from a fixed-roof tank can be appreciable. for fixed-roof tanks, the nominal capacity is the geometric volume from the bottom of the tank up to the curb angle, which is a metallic angle that is welded along the periphery at the top of the cylindrical portion of the tank. Additionally, gauge hatches/sample wells, float gauges, and roof manholes provide accessibility to these tanks and also serve as potential sources of volatile emissions. Breather vents may be called conservation vents, although hardly any conservation of vapors occurs at such low pressure settings. Generally, the term conservation vent is used to describe a pressure setting of 17 kPa (67 in. w.c.) or less. Vents with settings greater than 17 kPa (67 in. w.c.) are commonly called `pressure' vents
Correction is made dated 08 march 2012 in the underlined para.
Lifting Lugs are designed in accordance to “fittings” as per UL 142 stated in the addendum issued on 2009. refer to table 7.1 “top shell connection” materials specs ASTM A53/A53M, A134, A135, or A139Also refer to code para 7 Question raised dated 08 March 2012
Above surface Storage Tanks - ASTs
Above Surface Storage Tanks Fundamentals to Essentials Design & Integrity ManagementOverview, discussion and tutorials based on RAGAGEP March 08-10, 2012
Course Plan Course Overview 01 Hrs Objectives Background and learning outcome Contents of this course RAGAGEP 16 Hrs Design and Construction of Large, Welded, Low-Pressure Storage Tanks Welded Steel Tanks for Oil Storage UL 142 Tank Inspection, Repair, Alteration and Reconstruction Tutorial & Exercises 04 Hrs Quiz & Closing Session 01 Hrs
Course Overview Designed for professionals having background of Asset Integrity Management Overall objective is to help participants with above background to maintain ASTs in an environmentally safe manner. *Estimations exercises as per RAGAGEP After completing this course , participants can participate in advance level courses pertaining to AST Design and Analysis and Integrity Management like FFS etc Intend is to master fundamentals *Limited overview on a an application (CAE tool) for design and estimations
Storage Tanks Types Fixed Roof Tanks Floating Roof TanksClassification based on internal pressure Atmospheric Tanks They are usually operated at internal pressure slightly above atmospheric pressure. The fire codes define an atmospheric tank as operating from atmospheric up to 3.5 kN/m2 above atmospheric pressure Low pressure tanks Within the context of tanks, low pressure means that tanks are designed for a pressure higher than atmospheric tanks. This also means that these tanks are relatively high- pressure tanks. Tanks of this type are designed to operate from atmospheric pressure up to about 100 kN/m2 Pressure vessels (High pressure tanks)
UL 142 An OverviewSteel Aboveground Tanks for Flammable and Combustible Liquids
Contents Introduction PART - V Scope Accessories PART – I Performance Testing Horizontal Cylindrical tanks Leak Testing Vertical Cylindrical tanks Hydro load / strength test Rectangular tanks Top load test PART – II Buoyancy test All secondary Containment Lift lug tanks Support test PART – III Diked tanks PART – IV Tank Supports
Introduction Scope These tanks are intended for installation and use in accordance with the Flammable and Combustible Liquids Code, NFPA 30; the Standard for Installation of Oil-Burning Equipment, NFPA 31; the Motor Fuel Dispensing Facilities and Repair Garages, NFPA 30A; the Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, NFPA 37; the Uniform Fire Code, NFPA 1; and the International Fire Code published by the International Code Council These requirements do not apply to tanks covered by the Specification for Field-Welded Tanks for Storage of Production Liquids, API 12D; and the Specification for Shop-Welded Tanks for Storage of Production Liquids, API 12F.
20,000 gallons, UL 142 Tank DW10,000 gallons, UL142 tank
Introduction Design Criteria UL-142 is used for the design of flat-bottomed tanks containing combustible or flammable liquids up to a design pressure of 1/2 psig. The maximum capacity of a UL-142 tank is 50,000 gallons. Roofs can be conical or domed
PART - I Horizontal Cylindrical Tanks Capacities and Dimensions A horizontal tank shall not exceed either the maximum capacity or the diameter for the corresponding thickness of steel specified in Table 13.1 The overall length of a horizontal tank shall not be greater than six times its diameter. Tank diameters exceeding 144 inches (3.66 meters) shall be further limited to a maximum of 72 feet (21.95 meters) in cylinder length.
Steel Thickness A horizontal tank shall be constructed from steel not thinner than specified in Table 13.1 for its capacity and diameter. Head Joints A head of a horizontal tank shall be constructed of not more than three pieces for tank diameters of 48 to 96 inches (1.2 to 2.4 m); and four pieces for diameters of 97 to 156 inches (2.42 to 3.9 m)
PART - I Horizontal Cylindrical Tanks A head of a horizontal tank shall be flat flanged or flanged and dished A flanged flat head of a horizontal tank more than 72 inches (1.8 m) in diameter shall be made of steel not less than 5/16 inch (7.9 mm) thick or it shall be braced in accordance with Figure 13.1
MATERIALS All types of Tanks A tank shall be constructed of commercial or structural grade carbon steel per 5.2 or Type 304 or 316 stainless steel per 5.3. Only new material shall be used Carbon steel shall be in accordance with (a), (b), or both: A) Comply with the Specification for Carbon Structural Steel, ASTM A36M; or Specification for Steel, Sheet and Strip, Hot Rolled, Carbon, Structural, High-Strength Low-Alloy and High- Strength Low-Alloy with Improved Formability, ASTM A1011/A1011M; or Specification for Steel, Sheet and Strip, Heavy-Thickness Coils, Carbon, Hot-Rolled, ASTM A635/A635M. B) Have a carbon content of 0.3 percent or less, or a carbon equivalency (CE) of 0.53 percent or less as determined, and mechanical strength and welding characteristics at least equivalent to one of the steels specified in A above
MATERIALS All types of Tanks Stainless steel shall comply with the Specification for Stainless and Heat-Resisting Chromium-Nickel Steel Plate, Sheet, and Strip, ASTM A167; or Specification for Heat- Resisting Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels, ASTM A240/A240M
PART - I Vertical Cylindrical Tanks Capacities and Dimension The minimum diameter of a vertical tank shall not be less than one-quarter of its height The shell height of a vertical tank shall not be more than 50 feet ( 15.24 m), and the diameter shall not exceed 14 feet (4.27 m) Steel Thickness A vertical tank shall be constructed from steel not thinner than specified in Table 15.1
PART - I Vertical Cylindrical Tanks Tank Top The top of a vertical cylindrical tank shall be constructed of not more than four pieces. If two or more pieces are used, joints shall be one of the shell joint constructions described in Figure 6.1. The top of a single wall and outer shell of a secondary containment vertical tank shall be dished or conical. The height of a conical top shall not be less than one-sixth of the radius of the tank when the top is made of steel less than 0.167 inch (4.24 mm) thick and shall not be less than one-twelfth of the radius of the tank when the top is made of steel not less than 0.167 inch thick
PART - I Vertical Cylindrical Tanks Tank Bottom The bottom of a vertical cylindrical tank shall be constructed of not more than four pieces. If two or more pieces are used, joints shall be one of the shell joint constructions described in Figure 6.1, except that joint No. 6 shall not be used. Vertical cylindrical tanks elevated on supports shall meet the requirements of paragraph 30.3
PART - I Rectangular Tanks General Stiffening bars may be attached to the tank wall either by intermittent or continuous welding and may be placed on the inside or outside of the tank walls. Tie rods may be used inside of the tank. Baffles shall be intermittently welded or continuously welded on the inside of the tank Steel Thickness Tanks of this type shall be constructed from steel not thinner than 0.093 inch (2.36 mm) if of carbon steel or 0.071 inch (1.80 mm) if of stainless steel
PART - II The primary containment tank shell of a secondary containment tank shall be constructed in accordance with Part I – Primary Containment Tanks, Horizontal Cylindrical Constructions The outer shell and head of a secondary containment tank shall meet the requirements specified for Part I – Primary Containment Tanks, Horizontal Cylindrical Constructions
PART - III Capacity The actual dike capacity less the volume displaced by the supports or other internal apparatus except the tank shall be at minimum, 110 percent of the actual capacity of the tank. The dike walls and floor shall be constructed of steel not thinner than 0.093 inch (2.36 mm) if of carbon steel or 0.071 inch (1.80 mm) if of stainless steel
PART - III Open top Access and egress devices (ladder or stairs) shall be provided for the diked area if the height of the interior dike wall exceeds 6 feet (1.8 m). Closed top Closed top dike tanks shall be provided with steel covers over the dike area to keep precipitation debris, or other elements from entering the diked area, while also allowing for inspection. The dike shall be designed such that it cannot be pressurized, should fittings be capped.
PART - IV Saddles Maximum height of saddles, when measured from the lowest portion of the tank shell, shall be 12 inches (305 mm) unless protected by materials having a fire resistance rating of not less than two hours The base plate length shall be at least 90 percent of the tank diameter The stiffener thickness shall be a minimum of 3/8 inch (9.5 mm) for tank diameters 6 feet (1.8 m) or less and a minimum of 1/2 inch (12.7 mm) for tank diameters greater than 6 feet The saddles shall be positioned a distance of D/4 from the end of the primary tank, where D is the diameter of the tank
PART - V Ladders Interior ladders shall comply with the exterior ladder requirements except that the climbing surface must be vertical and directly in line with the edge of the tank manhole. Manholes shall not be less than 24 inches (0.6 m) in diameter. Hatch covers, if used, shall not be of the self-locking type if they can be opened only from the outside of the tank. Static Load (Ladders) – Ladders with a length of climb of 10 feet (3 m) or less shall support a static load of 1000 pounds (454 kg). The load is to be applied for 1 minute to a 3-1/2 inch (89 mm) wide block resting on the center of the longest rung. Ladders with a length of climb of greater than 10 feet shall support a static load of 2000 pounds (909 kg). The load is to be applied for 1 minute to the center of two rungs spaced 10 feet apart using 3-1/2 inch wide blocks. Compliance to OSHA 29 of the Code of Federal Regulations (CFR), Part 1910, Subpart D, Section 1910.27 – Fixed Ladders
PART - V Stairs Static Load (Stairs) – A static load of 1000 pounds (454 kg) is to be evenly distributed over a one square foot (0.09 m2) area on the center of the longest step for a period of one minute. Static Load (Guardrail) – A static load of 200 pounds (91 kg) is to be applied in various directions at a point on top of the rail located midway between the supports for a period of one minute. The load is to be applied using a 3-1/2 by 3-1/2 inch (89 by 89 mm) steel plate Compliance to OSHA, 29 CFR Part 1910, Subpart D, Section 1910.24 – Fixed Industrial Stairs
PART – V Runways Static Load (Runways) – A static load of 1000 pounds (454 kg) is to be evenly distributed over a one square foot (0.09 m ) 2 area on the center of the longest step for a period of one minute Compliance to OSHA, 29 CFR Part 1910, Subpart D, Section 1910.23 – Guarding Floor and Wall Openings and Holes, sub-paragraph (c) – Protection of open-sided floors, platforms, and runways. Sumps A sump that is provided as part of a tank assembly shall be of steel having a thickness not less than that of the tank shell or bottom. It shall be attached to the tank using a continuous full fillet weld, inside and outside, or the equivalent
PART - V Heating Coils A heating coil or hot well that is provided as part of a tank assembly and handles a fluid other than that stored in the tank, such as steam or hot water, shall have no joints in that portion located within the tank unless such joints are continuously welded or razed. The coil or hot well connection shall exit from the tank above the liquid level, unless made of steel having a wall thickness not less than specified for that portion of the tank shell through which the connection exists. A continuous full fillet weld shall be made where a connection pierces the tank or a manhole cover.
Performance Testing Leak Test (Primary Containment Tanks) The leakage test is to be conducted before painting the tank Apply internal air pressure and use soap-suds, or equivalent material for the detection of leaks. For a horizontal or rectangular tank, the test gauge pressure is to be not less than 3 psi (21 kPa) or more than 5 psi (35 kPa). For a vertical tank, the test gauge pressure is not to be less than 1-1/2 psi (10 kPa) nor more than 2-1/2 psi (17 kPa) or that gauge pressure above 1-1/2 psi which first causes visible deformation of the tank OR
Performance Testing Leak Test (Cont.) Completely fill the tank with water, applying the pressure specified in item (a) hydrostatically, and examine the tank for leakage Each compartment of a tank having two or more compartments is to be tested separately for leakage.
Performance Testing Leak Test (Secondary Containment Tanks) The leakage test is to be conducted before painting the tank with same procedure as of primary CT Upon completion of the finished secondary containment tank, the primary tank is again to be pressurized as per above procedure and held for 1 hour to check for leakage A continuous drop in pressure will be considered evidence of leakage As an option to the leakage test described in above, the annular space may be tested by applying a vacuum of at least 13 inches of mercury for a minimum of 12 hours
Performance Testing Hydrostatic Strength Test The source of water pressure is to be capable of maintaining a gauge pressure of at least 25 psi (172 kPa) for a period of not less than 2 minutes. (this is done in incremental stages, 5 psi (2psi / minute) The pressure gauges are to be calibrated and have a dial range gauge pressure of 0 – 50 or 0 – 60 psi (345 or 415 kPa), a face size of at least 3-1/2 inches (89 mm) in diameter, graduations of a gauge pressure of 1 psi or 10 kPa maximum, and an accuracy of ±1 percent of the full scale reading. Piping and fittings as shown in Figure 40.1 are to be appropriate for the test pressure
Performance Testing Top Load Test The top surface of flat top tanks is to be subjected to a 1000 pound (454 kg) load, applied over a one square foot (0.09 m ) area at the weakest part of the tank top for a 2 period of 5 minutes. The load is then to be removed. There shall be no permanent deformation or leakage when subjecting the tank to the Tank Leakage Test, Section
Performance Testing Buoyancy Test The diked area is to be filled with water to its maximum capacity while the tank remains empty. This condition is to be maintained for a minimum of one hour. The tank shall not show uplifting from the dike floor. The dike is then to be emptied and the tank and dike are then examined. There shall be no evidence of structural damage
Performance Testing Hydrostatic Load Test This test is to be conducted immediately following the buoyancy test. The dike is to be emptied and the reference position of the dike determined. The dike shall then be filled with water and examined for structural damage or deflection. There shall be no structural damage or deflection of the dike walls exceeding L/100, where L is the length of the side wall. After the dike is emptied, there shall be no structural damage or permanent deflection of the dike walls. In addition, there shall be no leakage as evidenced by visual inspection of the dike. The dike is then to be emptied. There shall be no permanent deformation or leakage when subjecting the tank to the Tank Leakage Test
Performance Testing Tanks Supports Load Test This test is to be carried out as per below scheme: The tank is to be completely filled with water. An evenly distributed load equal to the weight of the filled tank is to be placed across the top of the filled tank on a line parallel to the longitudinal axis of the tank. The tank and supports shall withstand this load for 2 minutes
Performance Testing Lifting Lug Test Fittings intended to be used to lift and move a tank shall be subjected for not less than 1 minute to a load equal to twice the weight of the empty tank. Single or multiple fittings may be tested to establish a load rating for each fitting. A fitting or fittings shall be tested in a manner which simulates the worst case lifting configuration for which each fitting’s load rating will be determined The lift fittings and the tank shall not show evidence of damage, as defined by cracking or tearing of the lift fitting itself, of the tank wall itself, or of any metal weld attachment.
Work Out Manufacturing and Production Tests Primary and Secondary tanks Diked tanks Markings Marking method and locations Appendix A (Capacity tables) Revisions and superseded sections/paragraphs
Welded Tanks for Oil Storage Overview, discussion as per RAGAGEP
Contents Scope Construction of tanks Appendices A to W Fabrication Responsibilities Inspection & Testing Important Definitions Design Materials Loads Capacity Special Considerations Shell design One Foot Method Variable point design method FEA (elastic)
Scope This standard establishes minimum requirements for material, design, fabrication, erection, and testing for vertical, cylindrical, aboveground, closed-and open- top, welded carbon or stainless steel storage tanks in various sizes and capacities for internal pressures approximating atmospheric pressure The internal pressures not exceeding the weight of the roof plates
Scope Applies only to tanks whose entire bottom is uniformly supported Tanks in non-refrigerated service that have a maximum design temperature of 93°C (200°F) or less The Standard has requirements given in two alternate systems of units of SI units, or US Customary units. The Purchaser and Manufacturer shall mutually agree on the units that will be used. All tanks and appurtenances shall comply with the Data Sheet and all attachments
Appendices Appendix A It provides alternative simplified design requirements for tanks where the stressed components, such as shell plates and reinforcing plates, are limited to a maximum nominal thickness of 12.5 mm (1/2 in.), including any corrosion allowance, and whose design metal temperature exceeds the minimums stated in the appendix
Appendices Appendix B It provides recommendations for the design and construction of foundations for flat-bottom oil storage tanks. Appendix C It provides minimum requirements for pontoon-type (single and double-deck-type) external floating roofs. Appendix D It provides requirements for submission of technical inquiries regarding this Standard.
Appendices Appendix E It provides minimum requirements for tanks subject to seismic loading. An alternative or supplemental design may be mutually agreed upon by the Manufacturer and the Purchaser. Appendix F It provides requirements for the design of tanks subject to a small internal pressure. This appendix applies to the storage of non-refrigerated liquids (see also API Std 620, Appendices Q and R). For maximum design temperatures above 93°C (200°F), see Appendix M. Appendix G It provides requirements for aluminum dome roofs
Appendices Appendix H It provides minimum requirements that apply to an internal floating roof in a tank with a fixed roof at the top of the tank shell Appendix I It provides acceptable construction details that may be specified by the Purchaser for design and construction of tank and foundation systems that provide undertank leak detection and subgrade protection in the event of tank bottom leakage, and provides for tanks supported by grillage. Appendix J It provides requirements covering the complete shop assembly of tanks that do not exceed 6 m (20 ft) in diameter. Appendix K It provides a sample application of the variable-design-point method to determine shell-plate thicknesses
Appendices Appendix L It provides the Data Sheet and the Data Sheet instructions for listing required information to be used by the Purchaser and the Manufacturer. The use of the Data Sheet is mandatory, unless waived by the Purchaser. Appendix M It provides requirements for tanks with a maximum design temperature exceeding 93°C (200°F) but not exceeding 260°C (500°F). Appendix N It provides requirements for the use of new or unused plate and pipe materials that are not completely identified as complying with any listed specification for use in accordance with this Standard.
Appendices Appendix O It provides recommendations for the design and construction of under-bottom connections for storage tanks. Appendix P It provides requirements for design of shell openings that conform to Table 5-6 that are subject to external piping loads. An alternative or supplemental design may be agreed upon by the Purchaser or Manufacturer.
Appendices Appendix R It provides a description of the load combinations used for the design equations appearing in this Standard. Appendix S It provides requirements for stainless steel tanks. Appendix T It summarizes the requirements for inspection by method of examination and the reference sections within the Standard. The acceptance standards, inspector qualifications, and procedure requirements are also provided. This appendix is not intended to be used alone to determine the inspection requirements within this Standard. The specific requirements listed within each applicable section shall be followed in all cases
Appendices Appendix U It provides requirements covering the substitution of ultrasonic examination in lieu of radiographic examination. Appendix V It provides additional requirements for tanks that are designed to operate under external pressure (vacuum) conditions. Appendix W It provides recommendations covering commercial and documentation issues. Alternative or supplemental requirements may be mutually agreed upon by the Manufacturer and the Purchaser
Limitations The rules of this Standard are not applicable beyond the following limits of piping connected internally or externally to the roof, shell, or bottom of tanks constructed according to this Standard: a. The face of the first flange in bolted flanged connections, unless covers or blinds are provided as permitted in this Standard. b. The first sealing surface for proprietary connections or fittings. c. The first threaded joint on the pipe in a threaded connection to the tank shell. d. The first circumferential joint in welding-end pipe connections if not welded to a flange.
Responsibilities The Manufacturer is responsible for complying with all provisions of this Standard. Inspection by the Purchaser’s inspector does not negate the Manufacturer’s obligation to provide quality control and inspection necessary to ensure such compliance. The Purchaser retains the right to provide personnel to observe all shop and job site work within the scope of the contracted work (including testing and inspection). Such individuals shall be afforded full and free access for these purposes, subject to safety and schedule constraints
Responsibilities In this Standard, language indicating that the Purchaser accepts, agrees, reviews, or approves a Manufacturer’s design, work process, manufacturing action, etc., shall not limit or relieve the Manufacturer’s responsibility to conform to specified design codes, project specifications and drawings, and professional workmanship.
Important Definitions Design Thickness The thickness necessary to satisfy tension and compression strength requirements by this Standard or, in the absence of such expressions, by good and acceptable engineering practice for specified design conditions, without regard to construction limitations or corrosion allowances Design Metal Temperature The lowest temperature considered in the design, which, unless experience or special local conditions justify another assumption, shall be assumed to be 8°C (15°F) above the lowest one-day mean ambient temperature of the locality where the tank is to be installed. The temperatures are not related to refrigerated-tank temperatures
Important Definitions Maximum Design Temperature: The highest temperature considered in the design, equal to or greater than the highest expected operating temperature during the service life of the tank. Requirement: The criteria must be used unless the Purchaser and the Manufacturer agree upon a more stringent alternative design. Recommendation: The criteria provide a good acceptable design and may be used at the option of the Purchaser and the Manufacturer. Tack Weld: A weld made to hold the parts of a weldment in proper alignment until the final welds are made.
Service Conditions The Purchaser shall specify any applicable special metallurgical requirements. When the service conditions might include the presence of hydrogen sulfide or other conditions care should be taken to ensure that the materials of the tank and details of construction are adequate to resist hydrogen-induced cracking. The Purchaser should consider limits on the sulfur content of the base and weld metals as well as appropriate quality control procedures in plate and tank fabrication. The hardness of the welds, including the HAZ, in contact with these conditions should be considered. As a reference, Rockwell C 22 and can be expected to be more susceptible to cracking than unwelded metal is. Any hardness criteria should be a matter of agreement between the Purchaser and the Manufacturer
Materials Use of cast iron for any pressure part or any part attached to the tank by welding is prohibited Because of hydrogen embrittlement and toxicity concerns, cadmium-plated components shall not be used without the expressed consent of the Purchaser. The tensile tests shall be performed on each plate if heat treated Subject to the Purchaser’s approval, controlled-rolled or thermo-mechanical-control-process (TMCP) plates (plates produced by a mechanical-thermal rolling process designed to enhance notch toughness) may be used where normalized plates are required. Each plate-as-rolled shall receive Charpy V-notch impact energy testing. The test specimens shall be Type A specimens (see ASTM A 370)
Materials ASTM Specs ASTM A 36M/A 36 for plates to a maximum thickness of 40 mm (1.5 in.). ASTM A 131M/A 131 ASTM A 283M/A 283, Grade C, for plates to a maximum thickness of 25 mm (1 in.) ASTM A 285M/A 285, Grade C, for plates to a maximum thickness of 25 mm (1 in.) ASTM A 516M Grades 380, 415, 450, 485/A 516, Grades 55, 60, 65, and 70 ASTM A 537M/A 537, Class 1 and Class 2, ASTM A 573M Grades 400, 450, 485/A 573, Grades 58, 65, and 70 ASTM A 633M/A 633, Grades C and D,
Materials ASTM Specs ASTM A 662M/A 662, Grades B and C, for plates to a maximum thickness of 40 mm (1.5 in.) ASTM A 678M/A 678 Grade A/B ASTM A 737M/A 737, Grade B, for plates to a maximum thickness of 40 mm (1.5 in.) ASTM A 841M/A 841 Grade A, Class 1 and Grade B, Class 2
Toughness Requirements The thickness and design metal temperature of all shell plates, shell reinforcing plates, shell insert plates, bottom plates welded to the shell, plates used for manhole and nozzle necks, plate-ring shell-nozzle flanges, blind flanges, and manhole cover plates shall be in accordance with Figure 4-1. In addition, plates more than 40 mm (1.5 in.) thick shall be of killed steel made to fine-grain practice and heat treated by normalizing, normalizing and tempering, or quenching and tempering, and each plate as heat treated shall be impact tested
Toughness Requirement Plates less than or equal to 40 mm (1.5 in.) thick, except controlled-rolled plates may be used at or above the design metal temperatures indicated in Figure 4-1 without being impact tested.
Design Wind Wind (v) speed in km/hr or mph as per ASCE figure 6.1 These design wind pressures are in accordance with ASCE 7 for wind exposure Category C. The design uplift pressure on the roof (wind plus internal pressure) need not exceed 1.6 times the design pressure P Windward and leeward horizontal wind loads on the roof are conservatively equal and opposite and therefore they are not included in the above pressures Fastest mile wind speed times 1.2 is approximately equal to 3-sec gust wind speed
Tank Capacity The Purchaser shall specify the maximum capacity Maximum capacity is the volume of product in a tank when the tank is filled to its design liquid level as defined (see Figure 5-4). The net working capacity is the volume of available product under normal operating conditions. The net working capacity is equal to the maximum capacity less the minimum operating volume remaining in the tank, less the overfill protection level (or volume) requirement (see Figure 5-4).
Quiz ? Estimate the net working capacity of a AST. The minimum operating volume is 4.2% at normal operating conditions (88 F). Assume 4.1% overfill levels as per LTs installed. The reading is measured at 0630Hrs. The tank can have a maximum of 87,200 gallons. SG is 0.88. Net Working Capacity = (Max.) Capacity – (Min.) Op. Volume – Overfill (Max.) Capacity = 87,200 gal (Min.) Op. Volume = 0.042 x 87,200 = 3662.4 gal Overfill = 0.041 x 87,200 = 3575.2 gal Net Working Capacity = 87,200 – 3,662.4 – 3,575.2 = 79,962.4 gal
Foundation and Corrosion Allowance Foundation The adequacy of the foundation is the responsibility of the Purchaser Sliding friction resistance shall be verified for tanks subject to lateral wind loads or seismic loads Corrosion Allowance Guidance to the Purchaser for considering corrosion allowance Corrosion allowance for anchor bolts shall be added to the nominal diameter. Corrosion allowance for anchor straps and brackets shall be added to the required strap and bracket thickness. For internal structural members, the corrosion allowance shall be applied to the total thickness unless otherwise specified
Shell Design One foot method is allowed for shells with diameters lesser than 60m (200ft) Sd and St is selected from the table 5-1 of permissible materials and allowable stresses The 1-foot method calculates the thicknesses required at design points 0.3 m (1 ft) above the bottom of each shell course. Appendix A permits only this design method The required shell thickness shall be the greater of the design shell thickness, including any corrosion allowance, or the hydrostatic test shell thickness, but the shell thickness shall not be less than the following :
Unless otherwise agreed to by the Purchaser, the shell plates shall have a minimum nominal width of 1800 mm (72 in.) Plates that are to be butt-welded shall be properly squared
Variable Design Pt Method – Shell plate ThickShells with diameters greater than 60m (200 feet), Variable Design-Point Method,See Appendix K. This method may only be used when the Purchaser has notspecified that the 1-foot method be used and when the following is true
Bottom course thicknessThe bottom-course thicknesses t1d and t1t for the design and hydrostatic testconditions shall be calculated using the following formulas For the design condition, t1d need not be greater than tpd. For the hydrostatic test condition, t1t need not be greater than tpt. To calculate the bottom-course thicknesses, preliminary values tpd and tpt for the design and hydrostatic test conditions shall first be calculated from the formulas in one foot equations
Second Course ThicknessTo calculate the second-course thicknesses for both the design condition andthe hydrostatic test condition, the value of the following ratio shall be calculatedfor the bottom course
Elastic Analysis Method (FEA) For tanks where L/H is greater than 1000/6 (2 in US Customary units), the selection of shell thicknesses shall be based on an elastic analysis that shows the calculated circumferential shell stresses to be below the allowable stresses given in Table 5-2. The boundary conditions for the analysis shall assume a fully plastic moment caused by yielding of the plate beneath the shell and zero radial growth.
Fabrication Shop Inspection Materials Welders qualification Factory acceptance during fabrication, shaping (can be done) Erection Tanks and their structural attachments shall be welded by the shielded metal-arc, gas metal-arc, gas tungsten-arc, oxyfuel, flux-cored arc, submerged-arc, electroslag, or electrogas process using suitable equipment Use of the oxyfuel process is not permitted when impact testing of the material is required
Fabrication Erection No welding of any kind shall be performed when the surfaces to be welded are wet from rain, snow, or ice; when rain or snow is falling on such surfaces; or during periods of high winds unless the welder and the work are properly shielded Each layer of weld metal or multilayer welding shall be cleaned of slag and other deposits before the next layer is applied. The edges of all welds shall merge smoothly with the surface of the plate without a sharp angle. All welding shall be free from coarse ripples, grooves, overlaps, abrupt ridges, and valleys that interfere with interpretation of NDE results. During the welding operation, plates shall be held in close contact at all lap joints
Fabrication Erection If protective coatings are to be used on surfaces to be welded, the coatings shall be included in welding-procedure qualification tests for the brand formulation and maximum thickness of coating to be applied. Low-hydrogen electrodes shall be used for all manual metal- arc welds in annular rings and shell courses, including the attachment of the first shell course to bottom or annular plates, as follows: Where the plates are thicker than 12.5 mm (1/2 in.) (based on the thickness of the thicker member being joined) and made of material from Groups I–III For all thicknesses when the plates are made of material from Groups IV, IVA, V and VI.
Fabrication Erection (Shell) Plates to be joined by butt welding shall be matched accurately and retained in position during the welding operation. Misalignment in completed vertical joints for plates greater than 16 mm (5/8 in.) thick shall not exceed 10% of the plate thickness or 3 mm (1/8 in.), whichever is less; misalignment for plates less than or equal to 16 mm (5/8 in.) thick shall not exceed 1.5 mm (1/16 in.). In completed horizontal butt joints, the upper plate shall not project beyond the face of the lower plate at any point by more than 20% of the thickness of the upper plate, with a maximum projection of 3 mm (1/8 in.); however, for upper plates less than 8 mm (5/16 in.) thick, the maximum projection shall be limited to 1.5 mm (1/16 in.).
Fabrication Erection (Shell) The reverse side of double-welded butt joints shall be thoroughly cleaned in a manner that will leave the exposed surface satisfactory for fusion of the weld metal to be added, prior to the application of the first bead to the second side. This cleaning may be done by chipping; grinding; melting out; or where the back of the initial bead is smooth and free from crevices that might entrap slag, another method that, upon field inspection, is acceptable to the Purchaser. For circumferential and vertical joints in tank shell courses constructed of material more than 38 mm (11/2 in.) thick (based on the thickness of the thicker plate at the joint), multipass weld procedures are required, with no pass over 19 mm (3/4 in.) thick permitted
Inspection Butt Welds Complete penetration and Fusion RT, UT Fillet Welds VI DPT (if required) RT (one joint per 30m/100ft , if required ) Tank Bottom VI Vacuum box test Tracer gas test Water test (A head of 150 mm (6 in.) of liquid shall be maintained using a temporary dam to hold that depth around the edge of the bottom.
Inspection Reinforcement plates After fabrication is completed but before the tank is filled with test water, the reinforcing plates shall be tested by the Manufacturer by applying up to 100 kPa (15 lbf/in.2) gauge pneumatic pressure between the tank shell and the reinforcement plate on each opening using the telltale hole Hydro-testing of Tank This hydrostatic test of the tank shall be conducted before permanent external piping is connected to the tank
Inspection Hydro-testing of Tank This hydrostatic test of the tank shall be conducted before permanent external piping is connected to the tank Any welded joints above the test-water level shall be examined for leakage by one of the following methods: 1. coating all of the joints on the inside with a highly penetrating oil, such as automobile spring oil, and carefully examining the outside of the joints for leakage; 2. applying vacuum to either side of the joints or applying internal air pressure as specified for the roof test in 7.3.7 and carefully examining the joints for leakage; or 3. using any combination of the methods stipulated in Subitems 1 and 2
Design Operating Temperature The temperature of liquids, gases, vapors stored or entering in the tank shall not exceed 250 F Pressure Used in Design Above Maximum liquid level Below Maximum liquid level Weight for liquid storage Minimum weight 48 lb/ ft3
Loadings Maximum Allowable Stress for Walls Max Tensile Stress (see Table 5-1) Max Compressive Stress Max Shear Stress Max Allowable Stress for Wind or Earth quake loading Max allowable stress values for structural members and bolts
UL 142 API 650 API 620Used for the design of Used for the design, Used for the design ofvertical, horizontal, vertical storage tanks vertical storage tanksrectangular storagetanksWith a design pressure With pressures up to 2.5 With a pressure ofof 1/2 psig psig and a maximum up to 15 psig and a temperature of 500 maximum temperature degrees F. of 250 degrees F.For flat-bottomed tanks Tanks have flat- Tank bottoms can becontaining combustible bottomed either flat, conical oror flammable liquids dished.Roofs can be conical or Roofs can be open- Roofs can be open-domed topped, self-supported topped, self-supported conical or domed roofs, conical orThe maximum capacity or structurally domed roofs, orof a UL-142 tank is supported cones structurally supported50,000 gallons. cones
Tank Inspection, Repair, Alteration, and Reconstruction An overview
Section – IV Inspection Inspection Frequency Internal Inspection Internal Inspection Interval Risk Based Inspection Alternative to internal inspection (table 4.1) External Inspection Non Destructive Examination Please Move to Inspection Slides for further Details
Tutorial # 1.1 Ground Bottom Contact Consider the 150,000 barrel tank in Case 1. Using API STD 653 requirements, determine the MRT at the end of the initial 10 year period assuming no corrosion protection. Ground/Bottom Contact - 150,000 Barrel Tank Quantities for the MRT equations are :
SolutionThe above results indicate that a hole will be produced in the bottom beforethe next scheduled inspection at the end of 10 years; therefore, additionalprotection must be provided.Using a value of 0.10 inches for MRT, the equation can be solved for O, (10yrs) or the anticipated in-service period of operation.In fact, if the tank is placed in service without corrosion protection, API STD653 would require an out-of-service internal inspection in about 3 years
Tutorial 1.2 Ground Bottom Contact Given the tank in Case 2, determine the MRT at the end of an initial 10 year period assuming no corrosion protection. Ground/Bottom Contact - 10,000 Barrel Gasoline Tank Quantities for the MRT equations are :
SolutionAPI STD6 53 requires a minimum thickness of 0.10 inch; therefore, anadditional corrosion protection must be provided in order to maintain the 10year inspection intervalUsing a value of 0.10 inches for MRT, the equation can be solved for O, (x)yrs) or the anticipated in-service period of operation.An anticipated in-service-period of 7.9 years results from the MRT value of0.10 inch
NOTE:It is important to note that many productiontanks will not be at the same location for theperiod of time that is calculated for theinternal inspection interval. Tanks that arerelocated should have an Internal ConditionExamination and, if warranted, a ConditionInspection when relocated.
Tutorial 1.3 Ground Bottom Contact Determine the out-of-service internal inspection interval for Case 3, using the procedure given in API 12R1. The corrosion rate is 0.005 inches per year. Ground/Bottom Contact - 500 Barrel Production Tank Determine t minimum , Where t minimum is based on the structural considerations of the annular ring.
Tutorial 1.4 Cathodic Protected Bottom Using the data given in Case 1 , determine the MRT at end of an initial 10 year period assuming the bottom is cathodically protected. Quantities for the MRT are:
SolutionAdditional protection is needed in order to prevent leaks before the nextshutdown.The example can also be worked using a nominal external pitting rate of0.001 inches per year.
Tutorial 1.5 & 1.6 background API STD 653 sets the tank bottom internal corrosion and pitting rate to zero if the bottom is internally lined with a thick film reinforced lining greater than 0.05 inches (in accordance with API RP 652). As per API STD 653; MRT requirement of 0.10 inch if the bottom is internally lined. The selection of an internal liner or cathodic protection system should be based on an economic analysis Next tutorials 1.5 show the impact of a bottom lining on the two tanks in Cases 1 and 2.
Tutorial 1.5 Tank Bottom Lining For the tank proposed in Case 2, determine the MRT at the end of an initial 10 year period assuming a suitable lining is applied to the interior of the bottom. The quantities in the equation are :
SolutionThis value is greater than the 0.10 inch requirement of API STD 653.Therefore, the tank may be operated for the 10 year period without ascheduled out-of-service internal inspection.
Tutorial 1.5 Tank Bottom Corrosion The bottom of a 100 foot diameter tank was measured using a floor scanning system. The tank had been in service for 10 years. The next internal inspection is scheduled in 10 years. Evaluate the minimum thickness criteria DATA
Background for Tutorial 1.6 & 1.7 Tutorial 1.6 shows calculations for determining the minimum shell thickness( t minimum) of an existing tank using the procedure given in API RP 12R1. API STD 653 provides a procedure for evaluating a change in service, repair, or alteration to determine if the change increases the risk of a brittle failure to an API STD 650 tank. Tutorial 1.7 illustrates the procedure by applying it to an existing 100 foot diameter tank and shows the use of Figure 5-1 of API STD 653 (Ed 2001)
Tutorial 1.6 Min Shell Thick. Determine the minimum thickness of an existing tank using the parameters in Appendix 6 of API RP 12R1. Quantities for the thickness calculation are:
SolutionThe minimum acceptable value is 0.062 inch. The calculated value is lessthan this, so 0.062 inch should be used as the minimum value
Tutorial 1.7 Brittle Fracture A 100 foot diameter by 48 foot high steel tank must be placed in service to store a petroleum product with a specific gravity of 0.85 and at ambient temperature. The tank does not meet API STD 650 (7th edition) material requirements. The owner has no records regarding a prior hydrostatic test on the tank, but the following data for minimum shell course thickness are available: For the purpose of this example, assume that each shell course is 8 feet high and that the original joint efficiency is 1 Assume a location where the lowest one-day mean temperature is 15°F Evaluate the tanks suitability for resisting brittle fracture. Evaluation starts at Step 4 of API STD 653, Figure 5-1 (Ed 2001)