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ASME Section I & Section VIII Fundamentals
Jurandir Primo, PE
©2012 Jurandir Primo
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1.0 - INTRODUCTION: The ASME Code design criteria consist of basic rules specifying the design method, design loads, allowable stress, acceptable materials, fabrication, testing, certification and inspection requirements. The design method known as "design by rule" uses design pressure, allowable stress and a design formula compatible with the geometry to calculate the minimum required thickness of pressurized tanks, vessels and pipes. The ASME - American Society of Mechanical Engineers - International Boiler and Pressure Vessel Code is made of 12 sections and contains over 15 divisions and subsections. 1.1 - Code Sections I. Power Boilers II. Materials III. Rules for Construction of Nuclear Facility Components IV. Heating Boilers V. Nondestructive Examination VI. Recommended Rules for the Care and Operation of Heating Boilers VII. Recommended Guidelines for the Care of Power Boilers VIII. Pressure Vessels IX. Welding and Brazing Qualifications X. Fiber-Reinforced Plastic Pressure Vessels XI. Rules for In-service Inspection of Nuclear Power Plant Components XII. Rules for Construction and Continued Service of Transport Tanks SECTION I. Power Boilers This Section provides requirements for all methods of construction of power, electric, and miniature boilers; high temperature water boilers used in stationary service; and power boilers used in locomotive, portable, and traction service. SECTION II. Materials • • • •
Part A - Ferrous Material Specifications Part B - Nonferrous Material Specifications Part C - Specifications for Welding Rods, Electrodes, and Filler Metals Part D - Properties
SECTION III. Rules for Construction of Nuclear Facility Components •
Subsection NCA - General Requirements for Divisions 1 and 2
DIVISION 1 • • • • • • •
Subsection NB- Class 1 Components Subsection NC- Class 2 Components Subsection ND- Class 3 Components Subsection NE- Class MC Components Subsection NF - s Subsection NG - Core Structures Subsection NH - Class 1 Components in Elevated Temperature Service
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DIVISION 2 •
Code for Concrete Containments
DIVISION 3 •
Containments for Transportation and Storage
SECTION IV. Heating Boilers Requirements for design, fabrication, installation and inspection of steam generating boilers, and hot water boilers intended for low pressure service that are directly fired by oil, gas, electricity, or coal. It contains appendices which cover approval of new material, methods of checking safety valve, safety relief valve capacity, definitions relating to boiler design and welding and quality control systems. SECTION V. Nondestructive Examination Requirements and methods for nondestructive examination which are referenced and required by other code Sections. It also includes manufacturer's examination responsibilities, duties of authorized inspectors and requirements for qualification of personnel, inspection and examination. SECTION VI. Recommended Rules for the Care and Operation of Heating Boilers It defines general descriptions, terminology and guidelines applicable to steel and cast iron boilers limited to the operating ranges of Section IV Heating Boilers. It includes guidelines for associated controls and automatic fuel burning equipment. SECTION VII. Recommended Guidelines for the Care of Power Boilers Guidelines to promote safety in the use of stationary, portable, and traction type heating boilers. The section provides guidelines to assist operators of power boilers in maintaining their plants as safely as possible. Contains fuels for routine operation; Operating and maintaining boiler appliances; Inspection and prevention of boiler failure; Design of installation; Operation of boiler auxiliaries; Control of internal chemical conditions SECTION VIII. Pressure Vessels Division 1 - Provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures exceeding 15 psig. Division 2 - Alternative rules, provides requirements to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures exceeding 15 psig. Division 3 - Alternative rules for Construction of High Pressure Vessels, provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures generally above 10,000 psi. SECTION IX. Welding and Brazing Qualifications Rules relating to the qualification of welding and brazing procedures as required by other Code Sections for component manufacture. Covers rules are related to the qualification and re-qualification of welders and welding and brazing operators in order that they may perform welding or brazing as required by other Code Sections in the manufacture of components.
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SECTION X. Fiber-Reinforced Plastic Pressure Vessels Requirements for construction of FRP (Fiber-Reinforced Plastic) pressure vessels in conformance with a manufacturer's design report. It includes production, processing, fabrication, inspection and testing methods required. SECTION XI. Rules for In-service Inspection of Nuclear Power Plant Components Requirements for the examination, in-service testing and inspection, and repair and replacement of components and systems in light-water cooled and liquid-metal cooled nuclear power plants. SECTION XII. Rules for Construction and Continued Service of Transport Tanks Requirements for construction and continued service of pressure vessels for the transportation of dangerous goods via highway, rail, air or water at pressures from full vacuum to 3,000 psig and volumes greater than 120 gallons. 1.2 - The ASME B31 Code ASME B31 was earlier known as ANSI B31. The B31 Code for Pressure Piping, covers Power Piping, Fuel Gas Piping, Process Piping, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids, Refrigeration Piping and Heat Transfer Components and Building Services Piping. Piping consists of pipe, flanges, bolting, gaskets, valves, relief devices, fittings and the pressure containing parts of other piping components. It also includes hangers and s, and other equipment items necessary to prevent overstressing the pressure containing parts. It does not include structures such as frames of buildings, buildings stanchions or foundations. B31.1 - 2001 - Power Piping Required piping for industrial plants and marine applications. This code prescribes requirements for the design, materials, fabrication, erection, test, and inspection of power and auxiliary service piping systems for electric generation stations, industrial institutional plants, central and district heating plants. The code covers boiler external piping for power boilers and high temperature, high pressure water boilers in which steam or vapor is generated at a pressure of more than 15 PSIG; and high temperature water is generated at pressures exceeding 160 PSIG and/or temperatures exceeding 250 degrees F. B31.2 - 1968 - Fuel Gas Piping This has been withdrawn as a National Standard and replaced by ANSI/NFPA Z223.1, but B31.2 is still available from ASME and is a good reference for the design of gas piping systems (from the meter to the appliance). B31.3 - 2002 - Process Piping Code rules for design of chemical, petroleum plants, refineries, hydrocarbons, water and steam. This Code contains rules for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. It prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping. Also included is piping which interconnects pieces or stages within a packaged equipment assembly.
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B31.4 - 2002 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids This Code prescribes requirements for the design, materials, construction, assembly, inspection, and testing of piping transporting liquids such as crude oil, condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia and liquid petroleum products between producers' lease facilities, tank farms, natural gas processing plants, refineries, stations, ammonia plants, terminals (marine, rail and truck) and other delivery and receiving points. The requirements for offshore pipelines are found in Chapter IX. Also included within the scope of this Code are: • Primary and associated auxiliary liquid petroleum and liquid anhydrous ammonia piping at pipeline terminals (marine, rail and truck), tank farms, pump stations, pressure reducing stations and metering stations, including scraper traps, strainers, and proper loops; • Storage and working tanks including pipe-type storage fabricated from pipe and fittings, and piping interconnecting these facilities; • Liquid petroleum and liquid anhydrous ammonia piping located on property which has been set aside for such piping within petroleum refinery, natural gasoline, gas processing, ammonia, and bulk plants; • Those aspects of operation and maintenance of liquid pipeline systems relating to the safety and protection of the general public, operating company personnel, environment, property and the piping systems.
B31.5 - 2001 - Refrigeration Piping and Heat Transfer Components This Code prescribes requirements for the materials, design, fabrication, assembly, erection, test, and inspection of refrigerant, heat transfer components, and secondary coolant piping for temperatures as low as -320 °F (-196 °C), whether erected on the premises or factory assembled, except as specifically excluded in the following paragraphs. s are advised that other piping Code Sections may provide requirements for refrigeration piping in their respective jurisdictions. This Code shall not apply to: • Any self- contained or unit systems subject to the requirements of Underwriters Laboratories or other nationally recognized testing laboratory: • Water piping and piping designed for external or internal gage pressure not exceeding 15 psi (105 kPa) regardless of size; or • Pressure vessels, compressors, or pumps, but does include all connecting refrigerant and secondary coolant piping starting at the first t adjacent to such apparatus. B31.8 - 2003 - Gas Transmission and Distribution Piping Systems This Code covers the design, fabrication, installation, inspection, and testing of pipeline facilities used for the transportation of gas. This Code also covers safety aspects of the operation and maintenance of those facilities. B31.8S-2001 - 2002 - Managing System Integrity of Gas Pipelines This Standard applies to on-shore pipeline systems constructed with ferrous materials and that transport gas. Pipeline system means all parts of physical facilities through which gas is transported, including pipe, valves, appurtenances attached to pipe, compressor units, metering stations, regulator stations, delivery stations, holders and fabricated assemblies.
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The principles and processes are applicable to all pipeline systems. This Standard is specifically designed to provide the operator (as defined in section 13) with the information necessary to develop and implement an effective integrity management program utilizing proven industry practices and processes. The processes and approaches within this Standard are applicable to the entire pipeline system. B31.9 - 1996 - Building Services Piping This Code Section has rules for the piping in industrial, institutional, commercial and public buildings, and multi-unit residences, which does not require the range of sizes, pressures, and temperatures covered in B31.1. This Code prescribes requirements for the design, materials, fabrication, installation, inspection, examination and testing of piping systems for building services. It includes piping systems in the building or within the property limits. B31.11 - 2002 - Slurry Transportation Piping Systems Rule for design, construction, inspection and security requirements of slurry piping systems. This code covers piping systems that transport aqueous slurries of no hazardous materials, such as coal, mineral ores and other solids between a slurry processing plant and the receiving plant. B31G - 1991 - Manual for Determining Remaining Strength of Corroded Pipelines The scope of this Manual includes all pipelines within the scope of the pipeline codes that are part of ASME B31 Code for Pressure Piping, ASME B31.4, Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols; ASME B31.8, Gas Transmission and Distribution Piping Systems; and ASME B31.11, Slurry Transportation Piping Systems. Parts 2, 3, and 4 are based on material included in ASME Guide for Gas Transmission and Distribution Piping Systems, 1983 Edition. 1.3 - ASME Certification and Inspection Procedures: The symbols "A", "S", "U", "PP" and "H" Stamps covers the fabrication and alteration of high pressure boilers, unfired pressure vessels, power piping and heating boilers. Once any ASME Stamped Pressure Vessel is manufactured, it is checked, tested and approved by the ASME Authorized Inspector, who review all the procedures and all the documentation and sign the Data Report Form before to procedure to Stamp the name plate with the “U” or “UM” symbols, which means that the Pressure Vessel fully complies with the ASME Code rules for construction of Pressure Vessels. The National Board of Boiler & Pressure Vessel Inspectors uses the “NB” Symbol as well the “R” Symbol to repair or to alter any previous Stamped Pressure Vessel. All material used in manufacture must be documented. All welders must be certified. Manufacturers have an Authorized Inspector, who is the judge of code acceptability. The quality of weld is then checked for lack of weld penetration, slag inclusion, overlap and excessive reinforcement. At the final inspection the units are hydrostatically tested at 1.5 times working pressure and observed for leaks. 1.4 – Imperial and Metric Values: Professionals and students should be well versed in conversion practice. Many US customary unit values presented in the ASME codes do not convert directly into metric values in the ASME editions.
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2.0 – SECTION I & SECTION VIII – Fundamentals: The formulae in ASME Section I and Section VIII are used to determine the minimum required thickness and design pressure of piping, tubes, drums and headers using the Maximum Allowable Working Pressure (MAWP). However, Paragraph UG-31 states, that these formulae may be also used for calculating wall thickness of tubes and pipes under internal pressure. 2.1 – Design: The ASME Boiler Code Section I, as well as Section VIII, requires longitudinal and circumferential butt ts to be examined by full radiograph. When the vessel design is required fully radiographed longitudinal butt-welded t, the cylindrical shell will have a t efficiency factor (E) of 1.0. This factor corresponds to a safety factor (or material quality factor) of 3.5 in the parent metal. When the vessel design is required non radiographed longitudinal butt-welded ts the vessel will have a t efficiency factor (E) of 0.7, which corresponds to a safety factor of 0.5 in., resulting in an increase of 43% in the thickness of the plates. 2.2 – Pressure Vessels Maximum Allowable Stress Values The maximum allowable stress values to be used in the calculation of the vessel’s wall thickness are given in the ASME Code for many different materials. These stress values are a function of temperature. Maximum Allowable Stress Value for Common Steels Material
Carbon Steel Plates and Sheets
Spec. Nbr
SA - 516
Grade 55 Grade 60 Grade 65 Grade 70
SA - 285
Grade A Grade B Grade C
SA - 36 SA - 203
High Alloy Steel Plates
Grade
SA - 240
Grade A Grade B Grade D Grade E Grade 304 Grade 304L Grade 316 Grade 316L
DIVISION 1 -20°F to 650°F 13,800 15,000 16,300 17,500
DIVISION 2 -20°F to 650°F 18,300 20,000 21,700 23,300
11,300 12,500 13,800 12,700 16,300 17,500 16,300 17,500 11,200 12,300 10,200
15,000 16,700 18,300 16,900 21,700 23,300 21,700 23,300 20,000 16,700 20,000 16,700
Division 1 governs the design by Rules, is less stringent from the standpoint of certain design details and inspection procedures, and thus incorporates a higher safety factor of 4. For example, if a 60,000 psi tensile strength material is used, the Maximum Allowable Stress Value is 15,000 psi. Division 2 governs the design by Analysis and incorporates a lower safety factor of 3. Thus, the maximum allowable stress value for a 60,000 psi tensile strength material will become 20,000 psi. ©2012 Jurandir Primo
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Many companies require that all their pressure vessels be constructed in accordance with Division 2 because of the more exacting standards. Others find that they can purchase less expensive vessels by allowing manufacturers the choice of either Division 1 or Division 2. Normally, manufacturers will choose Division 1 for low-pressure vessels and Division 2 for highpressure vessels. The maximum allowable stress values at normal temperature range for the steel plates most commonly used in the fabrication of pressure vessels are given in Table above. 3.0 – ASME SECTION I Power Boilers – Types, Design, Fabrication, Inspection & Repair Provides requirements for construction of power, electric, and miniature boilers; high temperature water boilers used in stationary service; and power boilers used in locomotive, portable, and traction service. Rules allow the use of the V, A, M, PP, S and E symbol stamps. The rules are applicable to boilers in which steam is generated at pressures exceeding 15 psig, and high temperature water boilers for operation at pressures exceeding 160 psig and/or temperatures exceeding 250 °F. This code covers power boiler superheaters, economizers, and other pressure parts connected directly to the boiler without intervening valves are considered as part of the scope of Section 1. 3.1 – SECTION I – Boiler Tubes up to and including 5 inches O.D. (125 mm): 4. To calculate the minimum required thickness, according to paragraph PG-27.2.1, use equation below:
b) To calculate the Maximum Allowable Working Pressure (MAWP):
Where: t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) D = Tube Outside Diameter (in) e = Thickness Factor (0.04 for expanded tubes; 0 = for strength welded tubes) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 1 - Boiler Tube: Calculate the minimum required wall thickness of a water tube boiler 2.75 in O.D., strength welded (e = 0) into place in a boiler. The tube has an average wall temperature of 650°F. The Maximum Allowable Working Pressure (MAWP) is 580 psi gauge. Material is carbon steel SA-192. Note: Before starting calculations check the correct stress table in ASME Section II, Table 1A: SA-192 = 11,800 psi – allowable stress – Div. 1. Solution: ©2012 Jurandir Primo
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For tubing up to and including 5 in O.D., use equation 1.1 above. P = [580 psi] D = [2.75 in] e = 0 (strength welded) S = [11,800 psi] at [650°F]) t=
2.75 x 580 2 (11,800) + 580
+ 0.005 (2.75) + 0
t = 0.079 in. Note: Where the manufacturing process produces only standard plate thickness, so should be used 1/8 in (3.2 mm) minimum. 3.2 – SECTION I – Piping, Drums, and Headers: The following formulae are found in ASME Section I, paragraph PG-27.2.2. The information for piping, drums, or headers may be given with either the inside I or outside (D) measurement. 4. Using the outside diameter:
b) Using the inside radius:
Where: t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) D = Tube Outside Diameter (in) R = Tube Radius (in) E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe) y = Wall Thickness Welding Factor (0.4 for 900°F & lower; 0.7 for 950°F & up) C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 2 – Steam Piping:
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Calculate the required minimum thickness of a seamless steam piping which carries steam at a pressure of 900 psi gauge and a temperature of 700°F. The piping is 10.77 in O.D., (10 inches nominal) plain end; the material is SA-335 – P1, alloy steel. Allow a manufacturer’s tolerance allowance of 12.5%. Note: Before starting calculations check the material stress table in ASME Section II, Table 1A: SA-335 – P1 = 13,800 psi – allowable stress – Div.1. Use equation 2.1:
P = [900 psi] D = [10.77 in] C=0 S = [13,800] – (SA-335 – P1 alloy steel at 700°F) E = 1.0 y = 0.4 (Ferritic steel less than 900°F) t=
900 x 10.77………. + 0 = 2(13,800)(1.0) + 2(0.4)(900)
t = 0.34 in. Therefore, including a manufacturer’s allowance of 12.5%; - 0.34 × 1.125 = 0.38 in. Example 3 – Maximum Allowable Working Pressure (MAWP): Calculate the Maximum Allowable Working Pressure (MAWP) for a seamless steel pipe of material SA209-T1. The outside pipe diameter is 12.75 in. (nominal diam. 12 in.) with a wall thickness of 0.46 in. The operating temperature is 850°F. The pipe is plain ended. D = 12.75 in (outside diameter) t = 0.46 in C = 0 (3 to 4 inches nominal and larger) S = 13,100 psi (Section II, Table 1A, Div.1, SA-209-T1 at 850°F) E = 1.0 (seamless pipe as per PG-9.1) y = 0.4 (austenitic steel at 850°F) Use equation 2.2: P=
2SE (t – C) = D – (2y) (t – C)
P = 2 (13,100) (1.0) x (0.46 – 0) = 12.75 – (2 x 0.4) (0.46 – 0) P = 26,200 x 0.46 = 12.75 – 0.368 P = 973 psi Example 4 – Welded Tube Boiler Drum:
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A welded water tube boiler drum of SA-515-60 material is fabricated to an inside radius of 18.70 in. on the tube sheet and 19.68 in on the drum. The plate thickness of the tube sheet and drum are 2.34 in. and 1.49 in., respectively. The longitudinal t efficiency is 100%, and the ligament efficiencies are 56% horizontal and 30% circumferential. The operating temperature is not to exceed 500°F. Determine the Maximum Allowable Working Pressure (MAWP) based on: Welded Water Tube Boiler Drum: DRUM & TUBESHEET
Note: This is a common example of a water tube drum fabricated from two plates of different thickness. Thicker material is required where the boiler tubes enter the drum than is required for a plain drum. This example has two parts: a) The drum – consider the drum to be plain with no penetrations. b) The tube sheet – consider the drum to have penetrations for boiler tubes. (a) Drum. Use equation 2.4 (inside radius R):
SE (t - C) Drum P = R + (1 - y) (t - C) Where: S = 15,000 psi (Section II, Table 1A, Div.1, SA-515-60 at 500°F) E = 1.0 t = 1.49 in C=0 R = 19.68 in y = 0.4 (Ferritic steel less than 900°F) Drum – P = (15,000) (1.0) (1.49 – 0).. = 19.68 + (1 – 0.4) (1.49 – 0) Drum – P = 15,000 x 1.49 19.68 + 0.894 Drum – P = 1,086 psi (b) Tube Sheet. Use equation 2.4 (inside radius R):
Where: ©2012 Jurandir Primo
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S = 15,000 psi E = 0.56 (circumferential stress = 30% and longitudinal stress = 56%; therefore = 0.56 < 2 x 0.30) t = 2.34 in C = 0 (3 to 4 inches nominal and larger) R = 18.70 in y = 0.4 (Ferritic steel less than 900°F) Tube Sheet – P = (15,000) (1.0) (2.34 – 0)… = 18.70 + (1 – 0.4) (2.34 – 0) Tube Sheet – P = 15,000 x 2.34 18.70 + 1.404 Tube Sheet – P = 1,746 psi Note: Consider the Maximum Allowable Working Pressure (MAWP) = 1,086 psi (lowest number). 4.0 – ASME SECTION VIII – Division 1, Division 2, Division 3: The ASME Section VIII, rules for fired or unfired pressure vessels, is divided into three divisions to provide requirements applicable to the design, fabrication, inspection, testing, and certification. The formulae and allowable stresses presented in this sketch are only for Division 1, the main code. It contains mandatory and non-mandatory appendices detailing supplementary design criteria, nondestructive examination and inspection acceptance standards. Rules pertaining to the use of the U, UM and UV Code symbol stamps are also included. 4.1 – SECTION VIII – Thin Cylindrical Shells: The formulae in ASME Section VIII, Division 1, paragraph UG-27, used for calculating the wall thickness and design pressure of pressure vessels, are: a) Circumferential Stress (longitudinal welds): •
When, P < 0.385SE:
b) Longitudinal Stress (circumferential welds): •
When, P < 1.25SE
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4.2 – SECTION VIII – Thick Cylindrical Shells: For internal pressures higher than 3,000 psi, special considerations must be given as specified in paragraph U-1 (d). As the ratio of t/R increases beyond 0.5, a more accurate equation is required to determine the thickness. The formulae in ASME Appendix 1, Supplementary Design Formulas used for calculating thick wall and design pressure, are: a) For longitudinal stress (longitudinal welds): When, P > 0.385SE:
and
b) For longitudinal stress (circumferential welds): When, P > 1.25SE:
and
Where: R = Design Radius (in.) Z = Dimensionless Factor 4.3 – SECTION VIII – Tube Spherical Shells: The standard design method uses an increased wall thickness at the equator line of the vessel to the additional stresses caused by the attachment of the legs. The formula for calculation the wall thickness of a segmented plate of a sphere to be welded in a heat exchanger tube is: t=
PL…… + C 2SE – 0.2P
L = Di/2 Where: ©2012 Jurandir Primo
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t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) Di = Inside Diameter of Sphere (in) L = Sphere Radius (in) E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe) C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 5 – Thin Cylindrical Shells: A vertical boiler is constructed of SA-515-60 according to Section VIII-1. It has an inside diameter of 96 in. and an internal design pressure of 1,000 psi at 450 F°. The corrosion allowance is 0.125 in., and t efficiency is E = 0.85. Calculate the required thickness of the shell. SA-515-60 = 15,000 psi – allowable stress, ASME Section II, Table 1A, Div.1. Since P < 0.385SE (6,545 psi) as 1,000 psi < 6,545 psi, use equation 1.3: t=
PR… + C SE – 0.6P
Considering the external radius = (48 in. + 0.125 in.). Corrosion allowance = 0.125 in. t=
1,000 x (48 in. + 0.125).. + 0.125 = 2(15,000)(0.85) – 0.6(1,000)
t = 0.0019 in. Example 6 – Thick Cylindrical Shells: a) When P > 0.385SE: Calculate the required shell thickness of an accumulator with P = 10,000 psi, R = 18 in., S = 20,000 psi, and E = 1.0. Assume a corrosion allowance of 0.125 in. For P > 0.385SE (7,700 psi) as 10,000 psi > 7,700 psi, use equation 1.7: t = R (Z
½
- 1) =
Z = (20,000)(1.0) + 10,000 = 30,000 = 3 (20,000)(1.0) – 10,000 10,000 t = (18) (3
½
– 1) + 0.125 = 8.08 in.
Example 7 – Thick Cylindrical Shells: b) When P < 0.385SE: Calculate the required shell thickness of an accumulator with P = 7,650 psi, R = 18 in, S = 20,000 psi, and E = 1.0. Assume corrosion allowance = 0. For P< 0.385SE (7,700 psi) as 7,650 psi < 7,700 psi, use equation 1.3: ©2012 Jurandir Primo
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t=
PR… + C SE – 0.6P
t=
7,650 x 18………… + 0 (20,000)(1.0) – 0.6(7,650)
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t = 8.9 in. Example 8 – Comparison between Equation 1.3 and Equation 1.7: Calculate the shell thickness, comparing the equation 1.3 with another answer using equation 1.7. t = R (Z
½
- 1) =
Z = (20,000)(1.0) + 7,650 = 27,650 = 2.24 (20,000)(1.0) – 7,650 12,350 t = (18 + 0) (2.24
½
- 1) =
t = 8.9 in. This shows that the “simple use” of equation (1.3) is accurate over a wide range of R/t ratios. 5.0 – SECTION I: Dished Heads Formulae: Flanged and dished heads can be formed from carbon steel, stainless steel, and other ferrous and nonferrous metals and alloys. Flanged and dished heads can be formed in a size range from 4 in to 300 in diameter and in thickness range of 14 Gauge to 1-1/2” thick. Pressure vessel heads and dished ends are essentially the same – the end caps of a pressure vessel tank or an industrial boiler. They are supplied with a flanged edge to make it easier for the fabricator to weld the head to the main body of the tank. Dished heads can be manufactured using a combination of processes, spinning & flanging, where the spherical radius is made via the spinning process and the knuckle is created under the flanging method. 5.1 – Blank, Unstayed Dished Heads: Paragraph PG-29.1 states that the thickness of a blank, unstayed dished head with the pressure on the concave side, when it is a segment of a sphere, shall be calculated by the following formula:
Where: t = Minimum thickness of head (in) P = maximum allowable working pressure (psi) L = Concave side radius (in) S = Maximum Allowable Working Stress (psi)
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Paragraph PG-29.2 states: “The radius to which the head is dished shall be not greater than the outside diameter of the flanged portion of the head. Where two radii are used, the longer shall be taken as the value of L in the formula.” Example 9 – Segment of a Spherical Dished Head: Calculate the thickness of a seamless, blank unstayed dished head having pressure on the concave side. The head has an inside diameter of 42.7 in. with a dish radius of 36.0 in. The Maximum Allowable Working Pressure (MAWP) is 360 psi and the material is SA-285 A. The temperature does not exceed 480°F. State if this thickness meets Code. Solution: Use equation 1.11
P = 360 psi L = 36.0 in S = 11,300 psi – SA-285 A at 480°F t = 5 (360 x 36) = 4.8 (11,300) t = 1.19 in. PG-29.6 states: “No head, except a full-hemispherical head, shall be of a lesser thickness than that required for a seamless shell of the same diameter.” Then, the minimum thickness of piping is:
Where: P = 360 psi D = 42.7 in y = 0.4 (Ferritic steel less than 900°F) E = 1.0 (welded) t=
360 x 42.7 = 2(11,300)(1.0) + 2 (0.4)(360)
t = 0.67 in. Therefore, the calculated head thickness meets the code requirements, since 1.19 > 0.67. Example 10 - Segment of a Spherical Dished Head with a Flanged-in Manhole: Calculate the thickness of a seamless, unstayed dished head with pressure on the concave side, having a flanged-in manhole 6.0 in x 16 in. Diameter head is 47.5 in with a dish radius of 45 in. The MAWP is 225 psi, the material is SA-285-C, and temperature does not exceed 428°F. ©2012 Jurandir Primo
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First thing to check: is the radius of the dish at least 80% of the diameter of the shell? Dish Radius = 45 Shell Diameter 47.5 0.947 > 0.8 - The radius of the dish meets the criteria. Then, use equation 1.11:
P = 225 psi L = 45 in S = 13,800 psi (450°F - use the next higher temperature). t = 5 (225 x 45) = 4.8 (13,800) t = 0.764 in. This thickness is for a blank head. PG-29.3 requires this thickness to be increased by 15% or 0.125 in., whichever is greater. As 0.764 × 0.15 = 0.114 in., that is less than 0.125 in., then, the thickness must be increased by 0.125 in. Then, the required head thickness is, t = 0.764 + 0.125 = ~0.90 in. 5.2 - Seamless or Full-Hemispherical Head: The thickness of a blank, unstayed, full-hemispherical head with the pressure on the concave side shall be calculated by the following formula:
t = Minimum thickness of head (in) P = Maximum Allowable Working Pressure (psi) L = Radius to which the head was formed (in) S = Maximum Allowable Working Stress (psi) The above formula shall not be used when the required thickness of the head given by the formula exceeds 35.6% of the inside radius. Instead, use the following formula:
Example 11 - Seamless or Full-Hemispherical Head: Calculate the minimum required thickness for a blank, unstayed, full-hemispherical head. The radius to which the head is dished is 7.5 in. The MAWP is 900 psi and the head material is SA 285-C. The average temperature of the header is 570°F. Solution: Use equation 1.13. ©2012 Jurandir Primo
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P = 900 psi L = 7.5 in. S = 13,800 psi - (SA 285-C at 600°F). t=
900 x 7.5 = 2 (13,800) – 0.2 (900)
t = 0.24 in. Check if this thickness exceeds 35.6% of the inside radius = 7.5 x 0.356 = 2.67 in. It does not exceed 35.6%, therefore the calculated thickness of the head meets the code requirements. 6.0 - SECTION VIII-1: Dished Heads Formulae: The Section VIII-1 determines the rules for dished heads. The most common configurations are spherical, hemispherical, elliptical (or ellipsoidal) and torispherical shapes. How the shapes are, make some confusion for beginners and even professionals s of ASME VIII. To cast a little light on these subjects see the resume below:
Spherical or Hemispherical Heads
Semi-Elliptical Heads (2:1)
Torispherical Heads
Elliptical or Ellipsoidal Heads (1.9:1)
Flanged and Dished Heads
Dished Discs
Toriconical Heads
Flat Dished Heads Non Standard 80-10 Dished Heads
6.1 - Spherical or Hemispherical Heads: a) When t < 0.356R or P < 0.665SE:
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b) When t > 0.356R or P > 0.665SE:
and
Example 12 - Spherical or Hemispherical Head: A pressure vessel is built of SA-516-70 material and has an inside diameter of 96 in. The internal design pressure is 100 psi at 450°F. Corrosion allowance is 0.125 in. and t efficiency is E = 0.85. Calculate the required thickness of the hemispherical head if “S” is 20,000 psi? Solution: Since 0.665SE > P = 11305 psi > 100 psi, use equation 2.1. The inside radius in a corroded condition is equal to, R = 48 + 0.125 = 48.125 in. t= t=
PR = 2SE – 0.2P = 100 x 48.125 2(20,000) (0.85) – 0.2(100)
t = 0.14 in. Example: Spherical Shell: A spherical pressure vessel with an internal diameter of 120 in has a head thickness of 1 in. Determine the design pressure if the allowable stress is 16300 psi. Assume t efficiency E = 0.85. No corrosion allowance is stated to the design pressure. Solution: Since t < 0.356R use equation 2.2. P=
2SEt = R + 0.2t
P = 2(16,300)(0.85)(1) = 60 + 0.2(1) P = 460 psi The calculated pressure 460 psi is < 0.665SE (9213 psi); therefore, equation 2.2 is acceptable. Example 13 - Thick Hemispherical Head: ©2012 Jurandir Primo
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Calculate the required hemispherical head thickness of an accumulator with P = 10,000 psi, R = 18.0 in, S = 15,000 psi, and E = 1.0. Corrosion allowance is 0.125 in. Solution: As 0.665SE < P = 9975 psi < 10,000 psi, use equation 2.3.
Y = 2(15,000)(1.0) + 10,000 = 2(15,000)(1.0) – 10,000 Y = 40,000 = 2 20,000 t = R (Y1/3 – 1) = (18.0) (21/3 – 1) + 0,125 = 4.8 in. 6.2 – Elliptical or Ellipsoidal Heads: The commonly used semi-ellipsoidal head has a ratio of base radius to depth of 2:1 (shown in Fig. 2a). The actual shape can be approximated by a spherical radius of 0.9D and a knuckle radius of 0.17D. The required thickness of 2:1 heads with pressure on the concave side is given below: Semi-Elliptical or Semi-Ellipsoidal Heads – 2:1:
Example 14 - Elliptical or Ellipsoidal Heads: Calculate the head thickness considering the dimensions given below: ©2012 Jurandir Primo
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Inside Diameter of Head (Di): 18.0 in Inside Crown Radius (L): (18.0 x 0.9Di) in Inside Knuckle Radius (ri): (18.0 x 0.17Di) in Straight Skirt Length (h): 1.500 in Radius L - (18.0 x 0.9Di) = 16.20 in Radius ri - (18.0 x 0.17Di) = 3.06 in
Material and Conditions: Material: SA-202 Gr. B (Room Temperature) Internal Pressure: 200 psi Allowable Stress: 20,000 psi Head Longitudinal t Efficiency: 0.85 Corrosion Allowance: 0.010 in Variable: L/r = L/ri = 16.20/3.06 = 5.29 in a) Required Thickness: t=
PD + corrosion allowance 2SE – 0.2P
t=
200 x 18.0 + 0.010 2(20,000)(0.85) – 0.2(200)
t = 0.116 in. b) Maximum Pressure: P = 2SEt = D + 0.2t P = 2(20,000)(0.85)(0.116) = 18 + 0.2 (0.116) P = 219 psi. Note: Ellipsoidal heads and all torispherical heads having materials with minimum tensile strength > 80,000 psi shall be designed using a value of S = 20,000 psi at room temperature (see UG-23). ©2012 Jurandir Primo
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6.3 - Torispherical Heads: Shallow heads, commonly referred to as flanged and dished heads (F&D heads), are according to paragraph UG-32 (e), with a spherical radius L of 1.0D and a knuckle radius r of 0.06D. •
a) Flanged & Dished Head (F&D heads):
The dish radius of a Flanged and Dished Head is 1.0 D and the knuckle radius is 0.06% D. The required thickness of a Torispherical F&D Head with r/L = 0.06 and L = Di, is:
and
P = Pressure on the concave side of the head S = Allowable stress t = Thickness of the head L = Inside spherical radius E = t efficiency factor Example 15 - Torispherical Heads: A drum is to operate at 500°F and 350 psi and to hold 5000 gallons of water. The inside radius of the Dished Torispherical Heads is 78 in. The material is SA 285 Grade A. Assume “S” = 11,200 psi and “E” = 0.85. Solution: Dished Torispherical Heads with L = Di and r/L = 0.06, use equation 2.7. t = 0.885 PL = SE – 0.1P t=
0.885 (350) (78) = (11200)(0.85) – 0.1(350)
t = 2.54 in. •
b) Non Standard 80-10 Flanged & Dished Head:
On an 80-10 the inside radius (L) is 0.8 Di and the knuckle radius (ri) is 10% of the head diameter. For the required thickness of a Non Standard 80-10 Head, use equations 2.7 and 2.8. Deg 80-10 Torispherical Heads rather than standard shapes can be achieved by lowering the material costs. The 80-10 is typically only 66% the thickness of the standard Torispherical Heads.
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6.4 – Conical or Toriconical Heads: The required thickness of the Conical or Toriconical Head (knuckle radius > 6% OD) shall be determined by formula using internal diameter of shell, α ≤ 30º. t=
PD 2 (SE - 0.6P) cos α
2.9
L = Di / (2 cos α) Di = Internal Diameter (conical portion) = D - 2 r (1 - cos α) r = Inside Knuckle Radius Toriconical Heads Definitions:
6.6 - Scope of ASME Section VIII: • Objective: Minimum requirements for safe construction and operation, Division 1, 2, and 3. • Section VIII Division 1: 15 psig < P ≤ 3000 psig ©2012 Jurandir Primo
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• Other exclusions: – Internals (except for attachment weld to vessel) – Fired process heaters – Pressure containers integral with machinery – Piping systems • Section VIII, Division 2, Alternative Rules: 15 psig < P ≤ 3000 psig - identical to Division 1, but the different requirements are: – Allowable stress – Stress calculations – Design – Quality control – Fabrication and inspection The choice between Divisions 1 and 2 is based mainly on economics of materials. • Division 3, Alternative Rules - High Pressure Vessels: Applications over 10,000 psi; Pressure from external source, process reaction, application of heat, combination of these; Does not establish maximum pressure limits of Division 1 or 2 or minimum limits for Division 3. • Structure of Section VIII, Division 1: Subsection A: Part UG applies to all vessels; Subsection B: Requirements based on fabrication method, Parts UW, UF, UB; Subsection C: Requirements based on material class, Parts UCS, UNF, UHA, UCI, UCL, UCD, UHT, ULW, ULT. Mandatory and Nonmandatory Appendices • Determination of Material Thickness: • Yield Strength, Ultimate Tensile Strength, Creep Strength, Rupture Strength and Corrosion Resistance. • Resistance to Hydrogen Attack: -Temperature at 300 - 400°F, monatomic hydrogen forms molecular hydrogen in voids; - Pressure buildup can cause steel to crack; - Above 600°F, hydrogen attack causes irreparable damage through component thickness. • Brittle Fracture and Fracture Toughness: The conditions that could cause brittle fracture are: – Typically at “low” temperature – Can occur below design pressure – No yielding before complete failure – High enough stress for crack initiation and growth – Low enough material fracture toughness at temperature – Critical size defect to act as stress concentration ©2012 Jurandir Primo
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• Factors That Influence Fracture Toughness: - Temperature - Type and chemistry of steel - Manufacturing and fabrication processes - Arc strikes, especially if over repaired area - Stress raisers or scratches in cold formed thick plate • Material Groups – The Most Common Used Materials: Curve A: SA-216 Gr. WCB & WCC, normalized and tempered; SA-217 Gr. WC6, normalized and tempered. Curve B: SA-216 Gr. WCA, normalized and tempered or water-quenched and tempered; SA-216 Gr. WCB & WCC for maximum thickness of 2 in. (water-quenched and tempered); SA-285 Gr. A & B; SA-414 Gr. A; SA-515 Gr. 60; SA-516 Gr. 65 & 70, not normalized. Curve C: SA-182 Gr. 21& 22, normalized and tempered SA-302 Gr. C & D SA-336 Gr. F21 & F22, normalized and tempered S A-3 8 7 G r. 21 & 22, normalized and tempered S A-5 1 6 G r. 55 & 60, not normalized SA-533 Gr. B & C SA-662 Gr. A Curve D: SA-203 SA-537 Cl. 1, 2 & 3 SA-508 Cl. 1 SA-612, normalized SA-516, normalized SA 662, normalized SA-524 Cl. 1 & 2 SA-738 Gr. A • Bolting: • See the ASME Code Section VIII, Div. 1, for impact and nuts test for specified material specifications. • Additional ASME Code Impact Test Requirements • For welded construction over 4 in. thick, or non welded construction over 6 in. thick, if MDMT < 120°F • Not required for flanges if temperature -20°F; required if SMYS > 65 ksi unless specifically exempt. • Weld t Efficiencies, E ©2012 Jurandir Primo
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6.5 – Resume of Pressure Vessels Formulae – ASME Section I & ASME Section VIII: Item
Cylindrical Shell Hemispherical Shell (or Head)
Flat Flanged Head Torispherical Head (a)
Torispherical Head (b) 2:1 Semi-Elliptical Head (a) Ellipsoidal Head (b)
Toriconical Head
Thickness - t (in)
Pressure - P (in)
Stress - S (in)
PR SE - 0.6P
SEt R + 0.6t
P(R + 0.6t) t
t ≤ 0.25 D;
PR
2.SEt
P(R + 0.2t)
t ≤ 0.178D;
2SE - 0.2P
R + 0.2t
2t
D√0.3P/S
t²S/0.3D²
0.3D² P/t²
Notes P ≤ 0.385 SE P ≤ 0.685 SE
r/L = 0.06;
L ≤ D + 2t
0.885PL
SEt
P(0.885L + 0.1t)
SE - 0.1P
0.885L + 0.1t
t
PLM 2SE - 0.2P
2.SEt LM + 0.2t
P(LM + 0.2t) 2t
M = 3 + (L/r)1/2 / 4
h/D = 4
PD
2.SEt
P(D + 0.2t)
2SE - 0.2P
D + 0.2t
2t
PDK 2SE - 0.2P
2.SEt DK + 0.2t
P(DK + 0.2t) 2Et
PD 2(SE - 0.6P) cos α
2.SEt cos α D + 1.2t cos α
P(D + 1.2t cos α) 2t cos α
K = [2 + (D/2h)²] / 6;
2 ≤ D/h ≤ 6
α ≤ 30°
OBS.: D = Shell / Head Inside Diameter, E = Weld t Efficiency (0.7 -1.0), L = Crown Radius, P = Internal Pressure, h = Inside Depth of Head, r = Knuckle Radius, R = Shell/Head Inside Radius, S = Allowable Stress, t = Shell / Head Thickness.
Common Materials - Temperature Limits: ©2012 Jurandir Primo
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7.0 - Shell Nozzles – Fundamentals: Vessel components are weakened when material is removed to provide openings for nozzles or access openings. To avoid failure in the opening area, compensation or reinforcement is required. The Code procedure is to relocate the removed material to an area within an effective boundary around the opening. Figure bellow shows the steps necessary to reinforce an opening in a pressure vessel.
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• Diameter of circular opening, d: d = Diameter of Opening – 2 (Tn + Corrosion Allowance) • Required wall thickness of the nozzle (min): tn =
PR...... SE – 0.6P
• Area of required reinforcement, Ar: Ar = d.ts.F (in²) = Where: d =Diameter of circular opening, or finished dimension of opening in plane under consideration, in. ts = Minimum required thickness of shell when E = 1.0, in. F = Correction factor, normally 1.0 Example 16 – Basic Pipe Nozzle:
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Design Pressure = 300 psig Design Temperature = 200° F Shell Material is SA-516 Gr. 60 Nozzle Diameter 8 in, Sch. 40 Nozzle Material is SA-53 Gr. B, Seamless Corrosion Allowance = 0.0625" Vessel is 100% Radiographed a) Wall thickness of the nozzle (min): tn = tn =
PR...... SE – 0.6P
=
300 x 4.312”…….. + 0.0625 (Corrosion Allowance) 12,000(1.0) – 0.6(300)
tn = 0.11” + 0.0625” = 0.17 in (min) – Pipe Sch. 40 is t = 0.32 in. b) Circular opening, d: d = Diameter of Opening – 2 (Tn + Corrosion Allowance) d = 8.625 – 2(0.32 + 0.0625) = d = 8.625 – 2 (0.3825) = 7.86 in c) Area of required reinforcement, Ar: Ar = d.ts.F (in²) = Ar = 7.86 x 0.487 x 1.0 = 3.82 in² • Available reinforcement area in shell, Ar, as larger of As or An: As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) = As = 7.86 (0.5625 – 0,487) – 2x 0,5625 (0.5625 – 0,487) = 0.50 in² An = Smaller of: 2 [2.5 (Ts) (Tn – tn)] An = 2 [2.5 (0.5625) (0.32 – 0.17)] = 0.42 in² •
Ar < (As + An) =
Ar < (0.50 + 0.42) = 0.92 in² < 3.82 in² (Reqd.) OBS.: Therefore, it´s necessary to increase Ts and / or Tn to attend the premise Ar < (As + An). Example 17 – Basic Shell & Nozzle: ©2012 Jurandir Primo
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Design Pressure = 700 psi Design temperature = 700 °F Nozzle Diameter = 8 in. (8.625 OD) Material: • Shell – SA 516 Gr.70 • Head – SA 516 Gr. 70 • Nozzle – SA 106 Gr. B • E = 1.0 (weld efficiency) Required Shell Thickness: ts =
PR… SE – 0.6P
ts =
700 x 30……..... = 1.30 (Use Ts = 1 1/2”) 16,600(1.0) – 0.6(700)
Opening Reinforcement:
Required Head Thickness:
Ar (Reqd.) = d.ts = 8.625 x 1.3 = 11.2 in²
th =
PR…… 2SE – 0.2P
As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) =
th =
700 x 30…….......... = 0.64 (Use Th = 7/8”) 2(16,600)(1.0) – 0.2(700)
Required Nozzle Thickness: tn =
PR… SE – 0.6P
tn =
700 x 4.312”……..... = 0.21 (Use Tn = 1/2”) 14,400(1.0) – 0.6(700)
As = 8.625 (1.5 – 1.3) – 2 (1.0) (1.5 – 1.3) = 1.325 in² An = Smaller of: 2[2.5 (Ts) (Tn – tn)] An = 2[2.5 (1.5) (1.0 – 0.21)] = 5.925 in² Ar < (As + An) = Ar < (1.325 + 5.925) = 7.25 in² < 11.2 (Reqd.) OBS.: Necessary to increase Ts and / or Tn to attend the premise (As + An) > Ar.
Example 18 – Nozzle Design:
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8.0 – ASME Materials: The following Tables indicates the most common ferrous materials used in Pressure Vessels design and fabrication, including structural plates, pipes, tubes, castings, forgings, flanges, fittings, bolts and nuts. Beyond the knowledge of the most common ferrous materials, the Tables also help the student how to search the materials MAWP (Maximum Allowable Stress Values) in ASME Section II, Table 1A.
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8.1 - Carbon Steels:
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8.2 - Low Alloy Steels:
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8.1 – MAWP – Maximum Allowable Stress Values The Section II, Part D contains properties of ferrous and nonferrous materials adopted by the Code for the design of boiler, pressure-vessel, and nuclear-power-plant components including tables of the maximum allowable stresses and design-stress intensities for the materials adopted by various Codebook sections. The tables below are an extract from ASME for the most common ferrous materials for a design purpose.
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9.0 - Suplementary Design Formulas:
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Example 19 – MAWP (Maximum Allowable Working Pressure:
Example 20 – Thickness of a Cylindrical Shell Considering Internal Pressure
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Example 21 – Design of a Standard Torispherical Head
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Example 22 – Design of a Non-Standard Torispherical Head
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An Approved Continuing Education Provider
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ASME Section I & Section VIII Fundamentals
Jurandir Primo, PE
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1.0 - INTRODUCTION: The ASME Code design criteria consist of basic rules specifying the design method, design loads, allowable stress, acceptable materials, fabrication, testing, certification and inspection requirements. The design method known as "design by rule" uses design pressure, allowable stress and a design formula compatible with the geometry to calculate the minimum required thickness of pressurized tanks, vessels and pipes. The ASME - American Society of Mechanical Engineers - International Boiler and Pressure Vessel Code is made of 12 sections and contains over 15 divisions and subsections. 1.1 - Code Sections I. Power Boilers II. Materials III. Rules for Construction of Nuclear Facility Components IV. Heating Boilers V. Nondestructive Examination VI. Recommended Rules for the Care and Operation of Heating Boilers VII. Recommended Guidelines for the Care of Power Boilers VIII. Pressure Vessels IX. Welding and Brazing Qualifications X. Fiber-Reinforced Plastic Pressure Vessels XI. Rules for In-service Inspection of Nuclear Power Plant Components XII. Rules for Construction and Continued Service of Transport Tanks SECTION I. Power Boilers This Section provides requirements for all methods of construction of power, electric, and miniature boilers; high temperature water boilers used in stationary service; and power boilers used in locomotive, portable, and traction service. SECTION II. Materials • • • •
Part A - Ferrous Material Specifications Part B - Nonferrous Material Specifications Part C - Specifications for Welding Rods, Electrodes, and Filler Metals Part D - Properties
SECTION III. Rules for Construction of Nuclear Facility Components •
Subsection NCA - General Requirements for Divisions 1 and 2
DIVISION 1 • • • • • • •
Subsection NB- Class 1 Components Subsection NC- Class 2 Components Subsection ND- Class 3 Components Subsection NE- Class MC Components Subsection NF - s Subsection NG - Core Structures Subsection NH - Class 1 Components in Elevated Temperature Service
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DIVISION 2 •
Code for Concrete Containments
DIVISION 3 •
Containments for Transportation and Storage
SECTION IV. Heating Boilers Requirements for design, fabrication, installation and inspection of steam generating boilers, and hot water boilers intended for low pressure service that are directly fired by oil, gas, electricity, or coal. It contains appendices which cover approval of new material, methods of checking safety valve, safety relief valve capacity, definitions relating to boiler design and welding and quality control systems. SECTION V. Nondestructive Examination Requirements and methods for nondestructive examination which are referenced and required by other code Sections. It also includes manufacturer's examination responsibilities, duties of authorized inspectors and requirements for qualification of personnel, inspection and examination. SECTION VI. Recommended Rules for the Care and Operation of Heating Boilers It defines general descriptions, terminology and guidelines applicable to steel and cast iron boilers limited to the operating ranges of Section IV Heating Boilers. It includes guidelines for associated controls and automatic fuel burning equipment. SECTION VII. Recommended Guidelines for the Care of Power Boilers Guidelines to promote safety in the use of stationary, portable, and traction type heating boilers. The section provides guidelines to assist operators of power boilers in maintaining their plants as safely as possible. Contains fuels for routine operation; Operating and maintaining boiler appliances; Inspection and prevention of boiler failure; Design of installation; Operation of boiler auxiliaries; Control of internal chemical conditions SECTION VIII. Pressure Vessels Division 1 - Provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures exceeding 15 psig. Division 2 - Alternative rules, provides requirements to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures exceeding 15 psig. Division 3 - Alternative rules for Construction of High Pressure Vessels, provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures generally above 10,000 psi. SECTION IX. Welding and Brazing Qualifications Rules relating to the qualification of welding and brazing procedures as required by other Code Sections for component manufacture. Covers rules are related to the qualification and re-qualification of welders and welding and brazing operators in order that they may perform welding or brazing as required by other Code Sections in the manufacture of components.
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SECTION X. Fiber-Reinforced Plastic Pressure Vessels Requirements for construction of FRP (Fiber-Reinforced Plastic) pressure vessels in conformance with a manufacturer's design report. It includes production, processing, fabrication, inspection and testing methods required. SECTION XI. Rules for In-service Inspection of Nuclear Power Plant Components Requirements for the examination, in-service testing and inspection, and repair and replacement of components and systems in light-water cooled and liquid-metal cooled nuclear power plants. SECTION XII. Rules for Construction and Continued Service of Transport Tanks Requirements for construction and continued service of pressure vessels for the transportation of dangerous goods via highway, rail, air or water at pressures from full vacuum to 3,000 psig and volumes greater than 120 gallons. 1.2 - The ASME B31 Code ASME B31 was earlier known as ANSI B31. The B31 Code for Pressure Piping, covers Power Piping, Fuel Gas Piping, Process Piping, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids, Refrigeration Piping and Heat Transfer Components and Building Services Piping. Piping consists of pipe, flanges, bolting, gaskets, valves, relief devices, fittings and the pressure containing parts of other piping components. It also includes hangers and s, and other equipment items necessary to prevent overstressing the pressure containing parts. It does not include structures such as frames of buildings, buildings stanchions or foundations. B31.1 - 2001 - Power Piping Required piping for industrial plants and marine applications. This code prescribes requirements for the design, materials, fabrication, erection, test, and inspection of power and auxiliary service piping systems for electric generation stations, industrial institutional plants, central and district heating plants. The code covers boiler external piping for power boilers and high temperature, high pressure water boilers in which steam or vapor is generated at a pressure of more than 15 PSIG; and high temperature water is generated at pressures exceeding 160 PSIG and/or temperatures exceeding 250 degrees F. B31.2 - 1968 - Fuel Gas Piping This has been withdrawn as a National Standard and replaced by ANSI/NFPA Z223.1, but B31.2 is still available from ASME and is a good reference for the design of gas piping systems (from the meter to the appliance). B31.3 - 2002 - Process Piping Code rules for design of chemical, petroleum plants, refineries, hydrocarbons, water and steam. This Code contains rules for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. It prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping. Also included is piping which interconnects pieces or stages within a packaged equipment assembly.
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B31.4 - 2002 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids This Code prescribes requirements for the design, materials, construction, assembly, inspection, and testing of piping transporting liquids such as crude oil, condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia and liquid petroleum products between producers' lease facilities, tank farms, natural gas processing plants, refineries, stations, ammonia plants, terminals (marine, rail and truck) and other delivery and receiving points. The requirements for offshore pipelines are found in Chapter IX. Also included within the scope of this Code are: • Primary and associated auxiliary liquid petroleum and liquid anhydrous ammonia piping at pipeline terminals (marine, rail and truck), tank farms, pump stations, pressure reducing stations and metering stations, including scraper traps, strainers, and proper loops; • Storage and working tanks including pipe-type storage fabricated from pipe and fittings, and piping interconnecting these facilities; • Liquid petroleum and liquid anhydrous ammonia piping located on property which has been set aside for such piping within petroleum refinery, natural gasoline, gas processing, ammonia, and bulk plants; • Those aspects of operation and maintenance of liquid pipeline systems relating to the safety and protection of the general public, operating company personnel, environment, property and the piping systems.
B31.5 - 2001 - Refrigeration Piping and Heat Transfer Components This Code prescribes requirements for the materials, design, fabrication, assembly, erection, test, and inspection of refrigerant, heat transfer components, and secondary coolant piping for temperatures as low as -320 °F (-196 °C), whether erected on the premises or factory assembled, except as specifically excluded in the following paragraphs. s are advised that other piping Code Sections may provide requirements for refrigeration piping in their respective jurisdictions. This Code shall not apply to: • Any self- contained or unit systems subject to the requirements of Underwriters Laboratories or other nationally recognized testing laboratory: • Water piping and piping designed for external or internal gage pressure not exceeding 15 psi (105 kPa) regardless of size; or • Pressure vessels, compressors, or pumps, but does include all connecting refrigerant and secondary coolant piping starting at the first t adjacent to such apparatus. B31.8 - 2003 - Gas Transmission and Distribution Piping Systems This Code covers the design, fabrication, installation, inspection, and testing of pipeline facilities used for the transportation of gas. This Code also covers safety aspects of the operation and maintenance of those facilities. B31.8S-2001 - 2002 - Managing System Integrity of Gas Pipelines This Standard applies to on-shore pipeline systems constructed with ferrous materials and that transport gas. Pipeline system means all parts of physical facilities through which gas is transported, including pipe, valves, appurtenances attached to pipe, compressor units, metering stations, regulator stations, delivery stations, holders and fabricated assemblies.
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The principles and processes are applicable to all pipeline systems. This Standard is specifically designed to provide the operator (as defined in section 13) with the information necessary to develop and implement an effective integrity management program utilizing proven industry practices and processes. The processes and approaches within this Standard are applicable to the entire pipeline system. B31.9 - 1996 - Building Services Piping This Code Section has rules for the piping in industrial, institutional, commercial and public buildings, and multi-unit residences, which does not require the range of sizes, pressures, and temperatures covered in B31.1. This Code prescribes requirements for the design, materials, fabrication, installation, inspection, examination and testing of piping systems for building services. It includes piping systems in the building or within the property limits. B31.11 - 2002 - Slurry Transportation Piping Systems Rule for design, construction, inspection and security requirements of slurry piping systems. This code covers piping systems that transport aqueous slurries of no hazardous materials, such as coal, mineral ores and other solids between a slurry processing plant and the receiving plant. B31G - 1991 - Manual for Determining Remaining Strength of Corroded Pipelines The scope of this Manual includes all pipelines within the scope of the pipeline codes that are part of ASME B31 Code for Pressure Piping, ASME B31.4, Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols; ASME B31.8, Gas Transmission and Distribution Piping Systems; and ASME B31.11, Slurry Transportation Piping Systems. Parts 2, 3, and 4 are based on material included in ASME Guide for Gas Transmission and Distribution Piping Systems, 1983 Edition. 1.3 - ASME Certification and Inspection Procedures: The symbols "A", "S", "U", "PP" and "H" Stamps covers the fabrication and alteration of high pressure boilers, unfired pressure vessels, power piping and heating boilers. Once any ASME Stamped Pressure Vessel is manufactured, it is checked, tested and approved by the ASME Authorized Inspector, who review all the procedures and all the documentation and sign the Data Report Form before to procedure to Stamp the name plate with the “U” or “UM” symbols, which means that the Pressure Vessel fully complies with the ASME Code rules for construction of Pressure Vessels. The National Board of Boiler & Pressure Vessel Inspectors uses the “NB” Symbol as well the “R” Symbol to repair or to alter any previous Stamped Pressure Vessel. All material used in manufacture must be documented. All welders must be certified. Manufacturers have an Authorized Inspector, who is the judge of code acceptability. The quality of weld is then checked for lack of weld penetration, slag inclusion, overlap and excessive reinforcement. At the final inspection the units are hydrostatically tested at 1.5 times working pressure and observed for leaks. 1.4 – Imperial and Metric Values: Professionals and students should be well versed in conversion practice. Many US customary unit values presented in the ASME codes do not convert directly into metric values in the ASME editions.
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2.0 – SECTION I & SECTION VIII – Fundamentals: The formulae in ASME Section I and Section VIII are used to determine the minimum required thickness and design pressure of piping, tubes, drums and headers using the Maximum Allowable Working Pressure (MAWP). However, Paragraph UG-31 states, that these formulae may be also used for calculating wall thickness of tubes and pipes under internal pressure. 2.1 – Design: The ASME Boiler Code Section I, as well as Section VIII, requires longitudinal and circumferential butt ts to be examined by full radiograph. When the vessel design is required fully radiographed longitudinal butt-welded t, the cylindrical shell will have a t efficiency factor (E) of 1.0. This factor corresponds to a safety factor (or material quality factor) of 3.5 in the parent metal. When the vessel design is required non radiographed longitudinal butt-welded ts the vessel will have a t efficiency factor (E) of 0.7, which corresponds to a safety factor of 0.5 in., resulting in an increase of 43% in the thickness of the plates. 2.2 – Pressure Vessels Maximum Allowable Stress Values The maximum allowable stress values to be used in the calculation of the vessel’s wall thickness are given in the ASME Code for many different materials. These stress values are a function of temperature. Maximum Allowable Stress Value for Common Steels Material
Carbon Steel Plates and Sheets
Spec. Nbr
SA - 516
Grade 55 Grade 60 Grade 65 Grade 70
SA - 285
Grade A Grade B Grade C
SA - 36 SA - 203
High Alloy Steel Plates
Grade
SA - 240
Grade A Grade B Grade D Grade E Grade 304 Grade 304L Grade 316 Grade 316L
DIVISION 1 -20°F to 650°F 13,800 15,000 16,300 17,500
DIVISION 2 -20°F to 650°F 18,300 20,000 21,700 23,300
11,300 12,500 13,800 12,700 16,300 17,500 16,300 17,500 11,200 12,300 10,200
15,000 16,700 18,300 16,900 21,700 23,300 21,700 23,300 20,000 16,700 20,000 16,700
Division 1 governs the design by Rules, is less stringent from the standpoint of certain design details and inspection procedures, and thus incorporates a higher safety factor of 4. For example, if a 60,000 psi tensile strength material is used, the Maximum Allowable Stress Value is 15,000 psi. Division 2 governs the design by Analysis and incorporates a lower safety factor of 3. Thus, the maximum allowable stress value for a 60,000 psi tensile strength material will become 20,000 psi. ©2012 Jurandir Primo
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Many companies require that all their pressure vessels be constructed in accordance with Division 2 because of the more exacting standards. Others find that they can purchase less expensive vessels by allowing manufacturers the choice of either Division 1 or Division 2. Normally, manufacturers will choose Division 1 for low-pressure vessels and Division 2 for highpressure vessels. The maximum allowable stress values at normal temperature range for the steel plates most commonly used in the fabrication of pressure vessels are given in Table above. 3.0 – ASME SECTION I Power Boilers – Types, Design, Fabrication, Inspection & Repair Provides requirements for construction of power, electric, and miniature boilers; high temperature water boilers used in stationary service; and power boilers used in locomotive, portable, and traction service. Rules allow the use of the V, A, M, PP, S and E symbol stamps. The rules are applicable to boilers in which steam is generated at pressures exceeding 15 psig, and high temperature water boilers for operation at pressures exceeding 160 psig and/or temperatures exceeding 250 °F. This code covers power boiler superheaters, economizers, and other pressure parts connected directly to the boiler without intervening valves are considered as part of the scope of Section 1. 3.1 – SECTION I – Boiler Tubes up to and including 5 inches O.D. (125 mm): 4. To calculate the minimum required thickness, according to paragraph PG-27.2.1, use equation below:
b) To calculate the Maximum Allowable Working Pressure (MAWP):
Where: t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) D = Tube Outside Diameter (in) e = Thickness Factor (0.04 for expanded tubes; 0 = for strength welded tubes) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 1 - Boiler Tube: Calculate the minimum required wall thickness of a water tube boiler 2.75 in O.D., strength welded (e = 0) into place in a boiler. The tube has an average wall temperature of 650°F. The Maximum Allowable Working Pressure (MAWP) is 580 psi gauge. Material is carbon steel SA-192. Note: Before starting calculations check the correct stress table in ASME Section II, Table 1A: SA-192 = 11,800 psi – allowable stress – Div. 1. Solution: ©2012 Jurandir Primo
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For tubing up to and including 5 in O.D., use equation 1.1 above. P = [580 psi] D = [2.75 in] e = 0 (strength welded) S = [11,800 psi] at [650°F]) t=
2.75 x 580 2 (11,800) + 580
+ 0.005 (2.75) + 0
t = 0.079 in. Note: Where the manufacturing process produces only standard plate thickness, so should be used 1/8 in (3.2 mm) minimum. 3.2 – SECTION I – Piping, Drums, and Headers: The following formulae are found in ASME Section I, paragraph PG-27.2.2. The information for piping, drums, or headers may be given with either the inside I or outside (D) measurement. 4. Using the outside diameter:
b) Using the inside radius:
Where: t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) D = Tube Outside Diameter (in) R = Tube Radius (in) E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe) y = Wall Thickness Welding Factor (0.4 for 900°F & lower; 0.7 for 950°F & up) C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 2 – Steam Piping:
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Calculate the required minimum thickness of a seamless steam piping which carries steam at a pressure of 900 psi gauge and a temperature of 700°F. The piping is 10.77 in O.D., (10 inches nominal) plain end; the material is SA-335 – P1, alloy steel. Allow a manufacturer’s tolerance allowance of 12.5%. Note: Before starting calculations check the material stress table in ASME Section II, Table 1A: SA-335 – P1 = 13,800 psi – allowable stress – Div.1. Use equation 2.1:
P = [900 psi] D = [10.77 in] C=0 S = [13,800] – (SA-335 – P1 alloy steel at 700°F) E = 1.0 y = 0.4 (Ferritic steel less than 900°F) t=
900 x 10.77………. + 0 = 2(13,800)(1.0) + 2(0.4)(900)
t = 0.34 in. Therefore, including a manufacturer’s allowance of 12.5%; - 0.34 × 1.125 = 0.38 in. Example 3 – Maximum Allowable Working Pressure (MAWP): Calculate the Maximum Allowable Working Pressure (MAWP) for a seamless steel pipe of material SA209-T1. The outside pipe diameter is 12.75 in. (nominal diam. 12 in.) with a wall thickness of 0.46 in. The operating temperature is 850°F. The pipe is plain ended. D = 12.75 in (outside diameter) t = 0.46 in C = 0 (3 to 4 inches nominal and larger) S = 13,100 psi (Section II, Table 1A, Div.1, SA-209-T1 at 850°F) E = 1.0 (seamless pipe as per PG-9.1) y = 0.4 (austenitic steel at 850°F) Use equation 2.2: P=
2SE (t – C) = D – (2y) (t – C)
P = 2 (13,100) (1.0) x (0.46 – 0) = 12.75 – (2 x 0.4) (0.46 – 0) P = 26,200 x 0.46 = 12.75 – 0.368 P = 973 psi Example 4 – Welded Tube Boiler Drum:
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A welded water tube boiler drum of SA-515-60 material is fabricated to an inside radius of 18.70 in. on the tube sheet and 19.68 in on the drum. The plate thickness of the tube sheet and drum are 2.34 in. and 1.49 in., respectively. The longitudinal t efficiency is 100%, and the ligament efficiencies are 56% horizontal and 30% circumferential. The operating temperature is not to exceed 500°F. Determine the Maximum Allowable Working Pressure (MAWP) based on: Welded Water Tube Boiler Drum: DRUM & TUBESHEET
Note: This is a common example of a water tube drum fabricated from two plates of different thickness. Thicker material is required where the boiler tubes enter the drum than is required for a plain drum. This example has two parts: a) The drum – consider the drum to be plain with no penetrations. b) The tube sheet – consider the drum to have penetrations for boiler tubes. (a) Drum. Use equation 2.4 (inside radius R):
SE (t - C) Drum P = R + (1 - y) (t - C) Where: S = 15,000 psi (Section II, Table 1A, Div.1, SA-515-60 at 500°F) E = 1.0 t = 1.49 in C=0 R = 19.68 in y = 0.4 (Ferritic steel less than 900°F) Drum – P = (15,000) (1.0) (1.49 – 0).. = 19.68 + (1 – 0.4) (1.49 – 0) Drum – P = 15,000 x 1.49 19.68 + 0.894 Drum – P = 1,086 psi (b) Tube Sheet. Use equation 2.4 (inside radius R):
Where: ©2012 Jurandir Primo
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S = 15,000 psi E = 0.56 (circumferential stress = 30% and longitudinal stress = 56%; therefore = 0.56 < 2 x 0.30) t = 2.34 in C = 0 (3 to 4 inches nominal and larger) R = 18.70 in y = 0.4 (Ferritic steel less than 900°F) Tube Sheet – P = (15,000) (1.0) (2.34 – 0)… = 18.70 + (1 – 0.4) (2.34 – 0) Tube Sheet – P = 15,000 x 2.34 18.70 + 1.404 Tube Sheet – P = 1,746 psi Note: Consider the Maximum Allowable Working Pressure (MAWP) = 1,086 psi (lowest number). 4.0 – ASME SECTION VIII – Division 1, Division 2, Division 3: The ASME Section VIII, rules for fired or unfired pressure vessels, is divided into three divisions to provide requirements applicable to the design, fabrication, inspection, testing, and certification. The formulae and allowable stresses presented in this sketch are only for Division 1, the main code. It contains mandatory and non-mandatory appendices detailing supplementary design criteria, nondestructive examination and inspection acceptance standards. Rules pertaining to the use of the U, UM and UV Code symbol stamps are also included. 4.1 – SECTION VIII – Thin Cylindrical Shells: The formulae in ASME Section VIII, Division 1, paragraph UG-27, used for calculating the wall thickness and design pressure of pressure vessels, are: a) Circumferential Stress (longitudinal welds): •
When, P < 0.385SE:
b) Longitudinal Stress (circumferential welds): •
When, P < 1.25SE
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4.2 – SECTION VIII – Thick Cylindrical Shells: For internal pressures higher than 3,000 psi, special considerations must be given as specified in paragraph U-1 (d). As the ratio of t/R increases beyond 0.5, a more accurate equation is required to determine the thickness. The formulae in ASME Appendix 1, Supplementary Design Formulas used for calculating thick wall and design pressure, are: a) For longitudinal stress (longitudinal welds): When, P > 0.385SE:
and
b) For longitudinal stress (circumferential welds): When, P > 1.25SE:
and
Where: R = Design Radius (in.) Z = Dimensionless Factor 4.3 – SECTION VIII – Tube Spherical Shells: The standard design method uses an increased wall thickness at the equator line of the vessel to the additional stresses caused by the attachment of the legs. The formula for calculation the wall thickness of a segmented plate of a sphere to be welded in a heat exchanger tube is: t=
PL…… + C 2SE – 0.2P
L = Di/2 Where: ©2012 Jurandir Primo
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t = Minimum Design Wall Thickness (in) P = Design Pressure (psi) Di = Inside Diameter of Sphere (in) L = Sphere Radius (in) E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe) C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum) S = Maximum Allowable Stress According to ASME Section II, Table 1A Example 5 – Thin Cylindrical Shells: A vertical boiler is constructed of SA-515-60 according to Section VIII-1. It has an inside diameter of 96 in. and an internal design pressure of 1,000 psi at 450 F°. The corrosion allowance is 0.125 in., and t efficiency is E = 0.85. Calculate the required thickness of the shell. SA-515-60 = 15,000 psi – allowable stress, ASME Section II, Table 1A, Div.1. Since P < 0.385SE (6,545 psi) as 1,000 psi < 6,545 psi, use equation 1.3: t=
PR… + C SE – 0.6P
Considering the external radius = (48 in. + 0.125 in.). Corrosion allowance = 0.125 in. t=
1,000 x (48 in. + 0.125).. + 0.125 = 2(15,000)(0.85) – 0.6(1,000)
t = 0.0019 in. Example 6 – Thick Cylindrical Shells: a) When P > 0.385SE: Calculate the required shell thickness of an accumulator with P = 10,000 psi, R = 18 in., S = 20,000 psi, and E = 1.0. Assume a corrosion allowance of 0.125 in. For P > 0.385SE (7,700 psi) as 10,000 psi > 7,700 psi, use equation 1.7: t = R (Z
½
- 1) =
Z = (20,000)(1.0) + 10,000 = 30,000 = 3 (20,000)(1.0) – 10,000 10,000 t = (18) (3
½
– 1) + 0.125 = 8.08 in.
Example 7 – Thick Cylindrical Shells: b) When P < 0.385SE: Calculate the required shell thickness of an accumulator with P = 7,650 psi, R = 18 in, S = 20,000 psi, and E = 1.0. Assume corrosion allowance = 0. For P< 0.385SE (7,700 psi) as 7,650 psi < 7,700 psi, use equation 1.3: ©2012 Jurandir Primo
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t=
PR… + C SE – 0.6P
t=
7,650 x 18………… + 0 (20,000)(1.0) – 0.6(7,650)
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t = 8.9 in. Example 8 – Comparison between Equation 1.3 and Equation 1.7: Calculate the shell thickness, comparing the equation 1.3 with another answer using equation 1.7. t = R (Z
½
- 1) =
Z = (20,000)(1.0) + 7,650 = 27,650 = 2.24 (20,000)(1.0) – 7,650 12,350 t = (18 + 0) (2.24
½
- 1) =
t = 8.9 in. This shows that the “simple use” of equation (1.3) is accurate over a wide range of R/t ratios. 5.0 – SECTION I: Dished Heads Formulae: Flanged and dished heads can be formed from carbon steel, stainless steel, and other ferrous and nonferrous metals and alloys. Flanged and dished heads can be formed in a size range from 4 in to 300 in diameter and in thickness range of 14 Gauge to 1-1/2” thick. Pressure vessel heads and dished ends are essentially the same – the end caps of a pressure vessel tank or an industrial boiler. They are supplied with a flanged edge to make it easier for the fabricator to weld the head to the main body of the tank. Dished heads can be manufactured using a combination of processes, spinning & flanging, where the spherical radius is made via the spinning process and the knuckle is created under the flanging method. 5.1 – Blank, Unstayed Dished Heads: Paragraph PG-29.1 states that the thickness of a blank, unstayed dished head with the pressure on the concave side, when it is a segment of a sphere, shall be calculated by the following formula:
Where: t = Minimum thickness of head (in) P = maximum allowable working pressure (psi) L = Concave side radius (in) S = Maximum Allowable Working Stress (psi)
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Paragraph PG-29.2 states: “The radius to which the head is dished shall be not greater than the outside diameter of the flanged portion of the head. Where two radii are used, the longer shall be taken as the value of L in the formula.” Example 9 – Segment of a Spherical Dished Head: Calculate the thickness of a seamless, blank unstayed dished head having pressure on the concave side. The head has an inside diameter of 42.7 in. with a dish radius of 36.0 in. The Maximum Allowable Working Pressure (MAWP) is 360 psi and the material is SA-285 A. The temperature does not exceed 480°F. State if this thickness meets Code. Solution: Use equation 1.11
P = 360 psi L = 36.0 in S = 11,300 psi – SA-285 A at 480°F t = 5 (360 x 36) = 4.8 (11,300) t = 1.19 in. PG-29.6 states: “No head, except a full-hemispherical head, shall be of a lesser thickness than that required for a seamless shell of the same diameter.” Then, the minimum thickness of piping is:
Where: P = 360 psi D = 42.7 in y = 0.4 (Ferritic steel less than 900°F) E = 1.0 (welded) t=
360 x 42.7 = 2(11,300)(1.0) + 2 (0.4)(360)
t = 0.67 in. Therefore, the calculated head thickness meets the code requirements, since 1.19 > 0.67. Example 10 - Segment of a Spherical Dished Head with a Flanged-in Manhole: Calculate the thickness of a seamless, unstayed dished head with pressure on the concave side, having a flanged-in manhole 6.0 in x 16 in. Diameter head is 47.5 in with a dish radius of 45 in. The MAWP is 225 psi, the material is SA-285-C, and temperature does not exceed 428°F. ©2012 Jurandir Primo
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First thing to check: is the radius of the dish at least 80% of the diameter of the shell? Dish Radius = 45 Shell Diameter 47.5 0.947 > 0.8 - The radius of the dish meets the criteria. Then, use equation 1.11:
P = 225 psi L = 45 in S = 13,800 psi (450°F - use the next higher temperature). t = 5 (225 x 45) = 4.8 (13,800) t = 0.764 in. This thickness is for a blank head. PG-29.3 requires this thickness to be increased by 15% or 0.125 in., whichever is greater. As 0.764 × 0.15 = 0.114 in., that is less than 0.125 in., then, the thickness must be increased by 0.125 in. Then, the required head thickness is, t = 0.764 + 0.125 = ~0.90 in. 5.2 - Seamless or Full-Hemispherical Head: The thickness of a blank, unstayed, full-hemispherical head with the pressure on the concave side shall be calculated by the following formula:
t = Minimum thickness of head (in) P = Maximum Allowable Working Pressure (psi) L = Radius to which the head was formed (in) S = Maximum Allowable Working Stress (psi) The above formula shall not be used when the required thickness of the head given by the formula exceeds 35.6% of the inside radius. Instead, use the following formula:
Example 11 - Seamless or Full-Hemispherical Head: Calculate the minimum required thickness for a blank, unstayed, full-hemispherical head. The radius to which the head is dished is 7.5 in. The MAWP is 900 psi and the head material is SA 285-C. The average temperature of the header is 570°F. Solution: Use equation 1.13. ©2012 Jurandir Primo
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P = 900 psi L = 7.5 in. S = 13,800 psi - (SA 285-C at 600°F). t=
900 x 7.5 = 2 (13,800) – 0.2 (900)
t = 0.24 in. Check if this thickness exceeds 35.6% of the inside radius = 7.5 x 0.356 = 2.67 in. It does not exceed 35.6%, therefore the calculated thickness of the head meets the code requirements. 6.0 - SECTION VIII-1: Dished Heads Formulae: The Section VIII-1 determines the rules for dished heads. The most common configurations are spherical, hemispherical, elliptical (or ellipsoidal) and torispherical shapes. How the shapes are, make some confusion for beginners and even professionals s of ASME VIII. To cast a little light on these subjects see the resume below:
Spherical or Hemispherical Heads
Semi-Elliptical Heads (2:1)
Torispherical Heads
Elliptical or Ellipsoidal Heads (1.9:1)
Flanged and Dished Heads
Dished Discs
Toriconical Heads
Flat Dished Heads Non Standard 80-10 Dished Heads
6.1 - Spherical or Hemispherical Heads: a) When t < 0.356R or P < 0.665SE:
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b) When t > 0.356R or P > 0.665SE:
and
Example 12 - Spherical or Hemispherical Head: A pressure vessel is built of SA-516-70 material and has an inside diameter of 96 in. The internal design pressure is 100 psi at 450°F. Corrosion allowance is 0.125 in. and t efficiency is E = 0.85. Calculate the required thickness of the hemispherical head if “S” is 20,000 psi? Solution: Since 0.665SE > P = 11305 psi > 100 psi, use equation 2.1. The inside radius in a corroded condition is equal to, R = 48 + 0.125 = 48.125 in. t= t=
PR = 2SE – 0.2P = 100 x 48.125 2(20,000) (0.85) – 0.2(100)
t = 0.14 in. Example: Spherical Shell: A spherical pressure vessel with an internal diameter of 120 in has a head thickness of 1 in. Determine the design pressure if the allowable stress is 16300 psi. Assume t efficiency E = 0.85. No corrosion allowance is stated to the design pressure. Solution: Since t < 0.356R use equation 2.2. P=
2SEt = R + 0.2t
P = 2(16,300)(0.85)(1) = 60 + 0.2(1) P = 460 psi The calculated pressure 460 psi is < 0.665SE (9213 psi); therefore, equation 2.2 is acceptable. Example 13 - Thick Hemispherical Head: ©2012 Jurandir Primo
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Calculate the required hemispherical head thickness of an accumulator with P = 10,000 psi, R = 18.0 in, S = 15,000 psi, and E = 1.0. Corrosion allowance is 0.125 in. Solution: As 0.665SE < P = 9975 psi < 10,000 psi, use equation 2.3.
Y = 2(15,000)(1.0) + 10,000 = 2(15,000)(1.0) – 10,000 Y = 40,000 = 2 20,000 t = R (Y1/3 – 1) = (18.0) (21/3 – 1) + 0,125 = 4.8 in. 6.2 – Elliptical or Ellipsoidal Heads: The commonly used semi-ellipsoidal head has a ratio of base radius to depth of 2:1 (shown in Fig. 2a). The actual shape can be approximated by a spherical radius of 0.9D and a knuckle radius of 0.17D. The required thickness of 2:1 heads with pressure on the concave side is given below: Semi-Elliptical or Semi-Ellipsoidal Heads – 2:1:
Example 14 - Elliptical or Ellipsoidal Heads: Calculate the head thickness considering the dimensions given below: ©2012 Jurandir Primo
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Inside Diameter of Head (Di): 18.0 in Inside Crown Radius (L): (18.0 x 0.9Di) in Inside Knuckle Radius (ri): (18.0 x 0.17Di) in Straight Skirt Length (h): 1.500 in Radius L - (18.0 x 0.9Di) = 16.20 in Radius ri - (18.0 x 0.17Di) = 3.06 in
Material and Conditions: Material: SA-202 Gr. B (Room Temperature) Internal Pressure: 200 psi Allowable Stress: 20,000 psi Head Longitudinal t Efficiency: 0.85 Corrosion Allowance: 0.010 in Variable: L/r = L/ri = 16.20/3.06 = 5.29 in a) Required Thickness: t=
PD + corrosion allowance 2SE – 0.2P
t=
200 x 18.0 + 0.010 2(20,000)(0.85) – 0.2(200)
t = 0.116 in. b) Maximum Pressure: P = 2SEt = D + 0.2t P = 2(20,000)(0.85)(0.116) = 18 + 0.2 (0.116) P = 219 psi. Note: Ellipsoidal heads and all torispherical heads having materials with minimum tensile strength > 80,000 psi shall be designed using a value of S = 20,000 psi at room temperature (see UG-23). ©2012 Jurandir Primo
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6.3 - Torispherical Heads: Shallow heads, commonly referred to as flanged and dished heads (F&D heads), are according to paragraph UG-32 (e), with a spherical radius L of 1.0D and a knuckle radius r of 0.06D. •
a) Flanged & Dished Head (F&D heads):
The dish radius of a Flanged and Dished Head is 1.0 D and the knuckle radius is 0.06% D. The required thickness of a Torispherical F&D Head with r/L = 0.06 and L = Di, is:
and
P = Pressure on the concave side of the head S = Allowable stress t = Thickness of the head L = Inside spherical radius E = t efficiency factor Example 15 - Torispherical Heads: A drum is to operate at 500°F and 350 psi and to hold 5000 gallons of water. The inside radius of the Dished Torispherical Heads is 78 in. The material is SA 285 Grade A. Assume “S” = 11,200 psi and “E” = 0.85. Solution: Dished Torispherical Heads with L = Di and r/L = 0.06, use equation 2.7. t = 0.885 PL = SE – 0.1P t=
0.885 (350) (78) = (11200)(0.85) – 0.1(350)
t = 2.54 in. •
b) Non Standard 80-10 Flanged & Dished Head:
On an 80-10 the inside radius (L) is 0.8 Di and the knuckle radius (ri) is 10% of the head diameter. For the required thickness of a Non Standard 80-10 Head, use equations 2.7 and 2.8. Deg 80-10 Torispherical Heads rather than standard shapes can be achieved by lowering the material costs. The 80-10 is typically only 66% the thickness of the standard Torispherical Heads.
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6.4 – Conical or Toriconical Heads: The required thickness of the Conical or Toriconical Head (knuckle radius > 6% OD) shall be determined by formula using internal diameter of shell, α ≤ 30º. t=
PD 2 (SE - 0.6P) cos α
2.9
L = Di / (2 cos α) Di = Internal Diameter (conical portion) = D - 2 r (1 - cos α) r = Inside Knuckle Radius Toriconical Heads Definitions:
6.6 - Scope of ASME Section VIII: • Objective: Minimum requirements for safe construction and operation, Division 1, 2, and 3. • Section VIII Division 1: 15 psig < P ≤ 3000 psig ©2012 Jurandir Primo
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• Other exclusions: – Internals (except for attachment weld to vessel) – Fired process heaters – Pressure containers integral with machinery – Piping systems • Section VIII, Division 2, Alternative Rules: 15 psig < P ≤ 3000 psig - identical to Division 1, but the different requirements are: – Allowable stress – Stress calculations – Design – Quality control – Fabrication and inspection The choice between Divisions 1 and 2 is based mainly on economics of materials. • Division 3, Alternative Rules - High Pressure Vessels: Applications over 10,000 psi; Pressure from external source, process reaction, application of heat, combination of these; Does not establish maximum pressure limits of Division 1 or 2 or minimum limits for Division 3. • Structure of Section VIII, Division 1: Subsection A: Part UG applies to all vessels; Subsection B: Requirements based on fabrication method, Parts UW, UF, UB; Subsection C: Requirements based on material class, Parts UCS, UNF, UHA, UCI, UCL, UCD, UHT, ULW, ULT. Mandatory and Nonmandatory Appendices • Determination of Material Thickness: • Yield Strength, Ultimate Tensile Strength, Creep Strength, Rupture Strength and Corrosion Resistance. • Resistance to Hydrogen Attack: -Temperature at 300 - 400°F, monatomic hydrogen forms molecular hydrogen in voids; - Pressure buildup can cause steel to crack; - Above 600°F, hydrogen attack causes irreparable damage through component thickness. • Brittle Fracture and Fracture Toughness: The conditions that could cause brittle fracture are: – Typically at “low” temperature – Can occur below design pressure – No yielding before complete failure – High enough stress for crack initiation and growth – Low enough material fracture toughness at temperature – Critical size defect to act as stress concentration ©2012 Jurandir Primo
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• Factors That Influence Fracture Toughness: - Temperature - Type and chemistry of steel - Manufacturing and fabrication processes - Arc strikes, especially if over repaired area - Stress raisers or scratches in cold formed thick plate • Material Groups – The Most Common Used Materials: Curve A: SA-216 Gr. WCB & WCC, normalized and tempered; SA-217 Gr. WC6, normalized and tempered. Curve B: SA-216 Gr. WCA, normalized and tempered or water-quenched and tempered; SA-216 Gr. WCB & WCC for maximum thickness of 2 in. (water-quenched and tempered); SA-285 Gr. A & B; SA-414 Gr. A; SA-515 Gr. 60; SA-516 Gr. 65 & 70, not normalized. Curve C: SA-182 Gr. 21& 22, normalized and tempered SA-302 Gr. C & D SA-336 Gr. F21 & F22, normalized and tempered S A-3 8 7 G r. 21 & 22, normalized and tempered S A-5 1 6 G r. 55 & 60, not normalized SA-533 Gr. B & C SA-662 Gr. A Curve D: SA-203 SA-537 Cl. 1, 2 & 3 SA-508 Cl. 1 SA-612, normalized SA-516, normalized SA 662, normalized SA-524 Cl. 1 & 2 SA-738 Gr. A • Bolting: • See the ASME Code Section VIII, Div. 1, for impact and nuts test for specified material specifications. • Additional ASME Code Impact Test Requirements • For welded construction over 4 in. thick, or non welded construction over 6 in. thick, if MDMT < 120°F • Not required for flanges if temperature -20°F; required if SMYS > 65 ksi unless specifically exempt. • Weld t Efficiencies, E ©2012 Jurandir Primo
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6.5 – Resume of Pressure Vessels Formulae – ASME Section I & ASME Section VIII: Item
Cylindrical Shell Hemispherical Shell (or Head)
Flat Flanged Head Torispherical Head (a)
Torispherical Head (b) 2:1 Semi-Elliptical Head (a) Ellipsoidal Head (b)
Toriconical Head
Thickness - t (in)
Pressure - P (in)
Stress - S (in)
PR SE - 0.6P
SEt R + 0.6t
P(R + 0.6t) t
t ≤ 0.25 D;
PR
2.SEt
P(R + 0.2t)
t ≤ 0.178D;
2SE - 0.2P
R + 0.2t
2t
D√0.3P/S
t²S/0.3D²
0.3D² P/t²
Notes P ≤ 0.385 SE P ≤ 0.685 SE
r/L = 0.06;
L ≤ D + 2t
0.885PL
SEt
P(0.885L + 0.1t)
SE - 0.1P
0.885L + 0.1t
t
PLM 2SE - 0.2P
2.SEt LM + 0.2t
P(LM + 0.2t) 2t
M = 3 + (L/r)1/2 / 4
h/D = 4
PD
2.SEt
P(D + 0.2t)
2SE - 0.2P
D + 0.2t
2t
PDK 2SE - 0.2P
2.SEt DK + 0.2t
P(DK + 0.2t) 2Et
PD 2(SE - 0.6P) cos α
2.SEt cos α D + 1.2t cos α
P(D + 1.2t cos α) 2t cos α
K = [2 + (D/2h)²] / 6;
2 ≤ D/h ≤ 6
α ≤ 30°
OBS.: D = Shell / Head Inside Diameter, E = Weld t Efficiency (0.7 -1.0), L = Crown Radius, P = Internal Pressure, h = Inside Depth of Head, r = Knuckle Radius, R = Shell/Head Inside Radius, S = Allowable Stress, t = Shell / Head Thickness.
Common Materials - Temperature Limits: ©2012 Jurandir Primo
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7.0 - Shell Nozzles – Fundamentals: Vessel components are weakened when material is removed to provide openings for nozzles or access openings. To avoid failure in the opening area, compensation or reinforcement is required. The Code procedure is to relocate the removed material to an area within an effective boundary around the opening. Figure bellow shows the steps necessary to reinforce an opening in a pressure vessel.
• Definitions: ©2012 Jurandir Primo
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• Diameter of circular opening, d: d = Diameter of Opening – 2 (Tn + Corrosion Allowance) • Required wall thickness of the nozzle (min): tn =
PR...... SE – 0.6P
• Area of required reinforcement, Ar: Ar = d.ts.F (in²) = Where: d =Diameter of circular opening, or finished dimension of opening in plane under consideration, in. ts = Minimum required thickness of shell when E = 1.0, in. F = Correction factor, normally 1.0 Example 16 – Basic Pipe Nozzle:
Basic design: ©2012 Jurandir Primo
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Design Pressure = 300 psig Design Temperature = 200° F Shell Material is SA-516 Gr. 60 Nozzle Diameter 8 in, Sch. 40 Nozzle Material is SA-53 Gr. B, Seamless Corrosion Allowance = 0.0625" Vessel is 100% Radiographed a) Wall thickness of the nozzle (min): tn = tn =
PR...... SE – 0.6P
=
300 x 4.312”…….. + 0.0625 (Corrosion Allowance) 12,000(1.0) – 0.6(300)
tn = 0.11” + 0.0625” = 0.17 in (min) – Pipe Sch. 40 is t = 0.32 in. b) Circular opening, d: d = Diameter of Opening – 2 (Tn + Corrosion Allowance) d = 8.625 – 2(0.32 + 0.0625) = d = 8.625 – 2 (0.3825) = 7.86 in c) Area of required reinforcement, Ar: Ar = d.ts.F (in²) = Ar = 7.86 x 0.487 x 1.0 = 3.82 in² • Available reinforcement area in shell, Ar, as larger of As or An: As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) = As = 7.86 (0.5625 – 0,487) – 2x 0,5625 (0.5625 – 0,487) = 0.50 in² An = Smaller of: 2 [2.5 (Ts) (Tn – tn)] An = 2 [2.5 (0.5625) (0.32 – 0.17)] = 0.42 in² •
Ar < (As + An) =
Ar < (0.50 + 0.42) = 0.92 in² < 3.82 in² (Reqd.) OBS.: Therefore, it´s necessary to increase Ts and / or Tn to attend the premise Ar < (As + An). Example 17 – Basic Shell & Nozzle: ©2012 Jurandir Primo
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Design Pressure = 700 psi Design temperature = 700 °F Nozzle Diameter = 8 in. (8.625 OD) Material: • Shell – SA 516 Gr.70 • Head – SA 516 Gr. 70 • Nozzle – SA 106 Gr. B • E = 1.0 (weld efficiency) Required Shell Thickness: ts =
PR… SE – 0.6P
ts =
700 x 30……..... = 1.30 (Use Ts = 1 1/2”) 16,600(1.0) – 0.6(700)
Opening Reinforcement:
Required Head Thickness:
Ar (Reqd.) = d.ts = 8.625 x 1.3 = 11.2 in²
th =
PR…… 2SE – 0.2P
As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) =
th =
700 x 30…….......... = 0.64 (Use Th = 7/8”) 2(16,600)(1.0) – 0.2(700)
Required Nozzle Thickness: tn =
PR… SE – 0.6P
tn =
700 x 4.312”……..... = 0.21 (Use Tn = 1/2”) 14,400(1.0) – 0.6(700)
As = 8.625 (1.5 – 1.3) – 2 (1.0) (1.5 – 1.3) = 1.325 in² An = Smaller of: 2[2.5 (Ts) (Tn – tn)] An = 2[2.5 (1.5) (1.0 – 0.21)] = 5.925 in² Ar < (As + An) = Ar < (1.325 + 5.925) = 7.25 in² < 11.2 (Reqd.) OBS.: Necessary to increase Ts and / or Tn to attend the premise (As + An) > Ar.
Example 18 – Nozzle Design:
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8.0 – ASME Materials: The following Tables indicates the most common ferrous materials used in Pressure Vessels design and fabrication, including structural plates, pipes, tubes, castings, forgings, flanges, fittings, bolts and nuts. Beyond the knowledge of the most common ferrous materials, the Tables also help the student how to search the materials MAWP (Maximum Allowable Stress Values) in ASME Section II, Table 1A.
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8.1 - Carbon Steels:
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8.2 - Low Alloy Steels:
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8.1 – MAWP – Maximum Allowable Stress Values The Section II, Part D contains properties of ferrous and nonferrous materials adopted by the Code for the design of boiler, pressure-vessel, and nuclear-power-plant components including tables of the maximum allowable stresses and design-stress intensities for the materials adopted by various Codebook sections. The tables below are an extract from ASME for the most common ferrous materials for a design purpose.
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9.0 - Suplementary Design Formulas:
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Example 19 – MAWP (Maximum Allowable Working Pressure:
Example 20 – Thickness of a Cylindrical Shell Considering Internal Pressure
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Example 21 – Design of a Standard Torispherical Head
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Example 22 – Design of a Non-Standard Torispherical Head
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