A Seminar onDesign of Pressure Vessel By: Mayank Nirbhay (10/IME/032) Prashant Tripathi (10/IME/040) Vivek Kumar Gupta (10/IME/059) Faculty Advisor: Dr. R.K. Mishra Date: 22/10/2013 Department of Mechanical Engineering School of Engineering Gautam Buddha University Greater Noida (U.P.) Seminar Highlights • • • • • • • • Introduction to Pressure Vessels and its classification Components of Pressure Vessels ASME Codes Design software and industrial applications Materials Selection Stress in Pressure Vessels Design of cylindrical shell. Calculation Program 1. General Introduction of Pressure Vessel INTRODUCTION [1] • Vessels, tanks, and pipelines that carry, store, or receive fluids are called pressure vessels. • A pressure vessel is defined as a container with a pressure differential between inside and outside. • The inside pressure is usually higher than the outside, except for some isolated situations. • Pressure vessels often have a combination of high pressures together with high temperatures. • Because of such hazards it is imperative that the design be such that no leakage can occur. • Pressure vessels and tanks are, in fact, essential to the chemical, petroleum, petrochemical and nuclear industries. It is in this class of equipment that the reactions, separations, and storage of raw materials occur. CLASSIFICATION OF PRESSURE VESSEL Pressure vessel Function Geometry Construction Service [3] Storage tank Cylindrical Monowall Cryogenic Process vessel Spherical Multi Wall Steam Heat Exchanger Conical Forged Lethal Horizontal/Vertical Fired/Unfired . theculminates. iv. ii.COMPONENTS OF PRESSURE VESSELS • The main components of pressure vessel are i.com . iii. v. Shell Heads Nozzles Stiffening rings Supports [4] Photo courtesy: www. and less expensive than flat heads. • Most pressure vessel shells are cylindrical. lighter. • Heads are typically curved rather than flat. • Curved configurations are stronger and allow the heads to be thinner. Heads are usually categorized by their shapes. • Pressure vessel shells are welded together to form a structure that has a common rotational axis. . spherical and conical in shape Head • All pressure vessel shells must be closed at the ends by heads (or another shell section).Shell • The shell is the primary component that contains the pressure. Fig: Different types of heads. ASME. (Modified from ASME Boiler and Pressure Vessel Code. New York.) . and earthquake loads.Support • The type of support that is used depends primarily on the size and orientation of the pressure vessel. Skirt b. Lug Saddle Leg Figure showing various pressure vessel supports. • the pressure vessel support must be adequate for the applied weight. Photo courtesy: www.pressurevesslesconsulting. Saddle d. wind.com Lug Skirt . Leg c. • Typical kinds of supports are as follow: a. thermowells..g. Photo courtesy: www.com . • These rings are installed on vessels operating under external pressure to prevent collapse of the vessel. (e.pressurevesslesconsulting.Nozzle • A nozzle is a cylindrical component that penetrates the shell or heads of a pressure vessel. level gauges. • Nozzles are used for attaching piping for flow into or out of the vessel and attach instrument connections. or pressure gauges). • The nozzle ends are usually flanged to allow for the necessary connections and to permit easy disassembly for maintenance or access. Stiffener Rings • Rings made of flat bar or plate or structural shapes welded around the Circumference of the vessel. Graph in Appendix V Nozzle neck thickness Welded Joint efficiencies Nozzle neck thickness Welded Joint efficiencies Charts for determining shell thickness of cylindrical and spherical vessels under external pressure . pressure on concave side UG-33 UG-45 UW-12 UG-45 UW-12 Appendix V Formed heads. pressure on convex side.Following parts of ASME Code SECTION VIII DIV-1 are used in design [5] U-1 UG-16 UG-20 UG-21 UG-22 UG-23 UG-27 UG-28 UG-29 UG-32 Scope for the design of pressure vessels General regarding design Design temperature Loadings Maximum allowable stresses Maximum allowable stresses Thickness of shells under internal pressure Thickness of shells under external pressure Stiffening rings for cylindrical shells under external pressure Formed heads. DESIGNING A PRESSURE VESSEL IN INDUSTRY . accurately and profitably.Software used in designing the pressure vessels: Fig: Screenshot of PV-Elite Software • Intergraph PV Elite is a complete solution for pressure vessel design. analysis and evaluation. . Users of PV Elite have designed equipment for the most extreme uses and have done so quickly. Materials Selection .2. b) Low Alloy Steel – Alloying elements are used.2 to 0. • The Structural quality materials are generally only of Carbon steel. • They are very economical . generally ranging from 0. a) Carbon Steel – Principal element is carbon. 2. Boiler Quality Materials [5] • These are the materials employed for pressure carrying components. Structural Quality Materials 1. petrochemical services are: Austenitic Stainless Steels Ferritic Stainless Steels. Structural Quality Materials [5] • These are the materials employed for very general services and non‐pressure services. c) High alloy steel‐ heavy alloying is done for example Stainless Steels.Selection of materials The broad classification of these materials can be done in following categories: 1. Boiler Quality Materials 2. • Commonly used stainless steels for refinery. but the total alloy content is limited to generally 5 %. .4. • If Vessel is designed according to ASME sec 8 div only spot radiography will be done for ASME sec 8 div 2 full radiographic testing is being done. 2.Material testing for Pressure vessel [5] 1. caustic services etc. PWHT‐ Post Weld Heat Treatment. . • After this test heat treatment is done on the welding joints to relieve the stresses. • Radiographic testing is done of the welding joints according to the pressure vessel. • Charpy V notch impact test is the most common type of test used. amine. • Recommended for corrosive services like HS. This is because the material tend to become more brittle at low temperature. Impact Testing‐ • The impact testing of materials is done to take care of low temperature service. 3. Stresses in Pressure Vessels . Compressive and tensile axial stresses due to wind. They are produced by mechanical loads and are the most hazardous of all types of stress.Primary general membrane stress. P. Circumferential and longitudinal stress due to pressure. Q. Primary stress Primary stresses are generally due to internal or external pressure or produced by sustained external forces and moments. . These stresses act over the full cross section of the vessel. plus secondary membrane stress. PL It is the combination of primary membrane stress.Mainly there are 2 types of stresses involved in a pressure vessel 1. b. 2. P : a. produced from sustained loadings. Types of primary general stress 1. Local primary membrane stress. c. Membrane stress due to local loads. Q These are the stress which are a. 2. Bending stress at a gross structural discontinuity: • b. Secondary stress Secondary mean stresses are developed at the junctions of major components of a pressure vessel and are produced by sustained loads other than internal or external pressure. b. QL These include : • a. • d. Secondary membrane stress. Secondary bending stress. Types of secondary stresses: 1. Discontinuity stresses at stiffening or support rings.2. . Thermal stresses. Membrane stress in the knuckle area of the head. The stress variation of the radial stress due to internal pressure. Division 1. Maximum shear stress theory This theory asserts that the breakdown of material depends only on the maximum shear stress attained in an element. Maximum principle stress theory: Both ASME Code. Section VIII. It is mainly used for Ductile material .STRESS/FAILURE THEORIES [5] The major theories of failures used to design a pressure vessel are : 1. 2. and division use the maximum stress theory as a basis for design. but it is not always accurate for ductile materials. While it accurately predict failure in brittle materials. BRITTLE RUPTURE : If the material used for the vessel is brittle than instead of plastic or elastic deformation. So excessive elastic deformation is undesirable. EXCESSIVE ELASTIC DEFORMATION • It is a type of expansion of vessel till limit of proportionality. vessel will ruptured instantly after increasing the slight load after yield point. PLASTIC INSTABILITY : • Plastic deformations occur in a pressure vessel if the Internal or external pressure becomes so high that resultant stresses acting on the pressure vessel exceeds the yield point. 2.MAJOR FAILURES ASSOCIATED WITH PRESSURE VESSELS [5] Major Failures associated with pressure vessel can usually be classified as 5 types : 1. • It affects the volume and density of fluid inside the vessel. • Plastic instability 3. . Hence for brittle material stresses should be kept low below the yield point. hence the purpose of the vessel will fail and effect the process. • Elastic instability in vessels is usually associated with the use of thin shells. CREEP: • Creep is a failure of material due to constant loading and unloading of material kept at one place for long time. • It arises due to periodic loading and loading. • It increases to cracks in the material after some time and finally material fails on load much lower than the yield point stress. . • At outside some corrosion resistant material are used to prevent the rusting. Generally taken 3mm at inside boundary layer. It starts initially from grain boundary where abnormal grains are there.4. CORROSION: • If excessive corrosion occurs than material thickness will decrease constantly and after a certain limit the material will fail • Due to this the vessels are provided with corrosion allowance thickness. 5. 4. Design of Shell . Ri. Pa1. S = allowable stress in the material t = thickness of the cylinder (mm) ρ=Density of liquid H=Height of liquid level CA = Corrosion allowance n = number of stiffening rings Leff = Overall effective length of pressure vessel L = Length of pressure vessel σhoop= Hoop or circumferential stresses σlong= Longitudinal stresses Pa. Pa2 = Allowable external pressure . Do = inside and outside diameter. Ro = inside and outside radius with corrosion allowance. (in) Di.VESSEL NOMENCLATURE E = Joint Efficiency Factor P = internal pressure (kg/cm2). of stiffening rings is calculated. VIII Div. 1. Design of shell under external pressure. Section VIII Division 1. UG-27. UG-28. For a optimum thickness the pressure vessel under external pressure is analyzed for satisfying the design using ASME BPV Code.Shell Design Basically the design of shell consists of following steps- Design of shell under internal pressure. Or for the optimum thickness no. Minimum thickness is calculated using ASME Boiler and Pressure Vessel Code. Pe Pi 1 2 . Sec. SHELL UNDER INTERNAL PRESSURE HOOP STRESS Calculate internal design pressure P = Pi + Pliquid level Classical Equation ℎ = ASME CODE EQUATION LONGITUDINAL STRESS Classical Equation = 2 ASME CODE EQUATION = ( − . ) . ) = ( + . 0 0 ≥ 10 < 10 . the critical pressure is calculated for two situations. [9]. involving the ratio of the outside diameter to the thickness (Do/t). 2. 1. In the ASME code.Design of cylindrical shell under external pressure • Designing vessels for external pressure is an iterative procedure • External pressure on cylindrical shells causes compressive forces that could lead to buckling • . [8]. the value of Pa is determined from = 7) Compare the calculated value of Pa (Allowable Pressure) obtained in Steps 6 or 7 with P. if Pa > P assumed thickness is optimum .Case-I: External Pressure for Cylinders with ≥ Steps [9]1) Assume a value of t for the cylinder. select the thickness. with the calculated values of L/Do and Do/t and establish an A value. If Pa is smaller than P. 2) Calculate the quantities L/Do and Do/t. 3) Use Fig. 4) Use an External Pressure Chart to determine the A value and determine the B value from the appropriate temperature chart. 5) Calculate the allowable external pressure from the equation = 4 3 2 3 6) When A falls to the left of the curves. FACTOR A CHART [5] . FACTOR B CHART [5] . 10.167 = − 0. the value of factor A can be calculated using the following formula [9]: 1.0833 Where B is obtained as discussed above. use a value of 0. .1 = 2 For values of A greater than 0.Case-II: External Pressure for Cylinders with < For values of Do/t less than 4. When Do/t is less than 10. the allowable external pressure is taken as the smaller of the values determined from the following two equations: 1 2.10. . = + () = + . < 0.385 ( − 0.SUMMARY OF DESIGN PROCEDURE FOR SHELL Step-1: Calculate the total internal design pressure (P). = . P = pressure inside the vessel+ pressure due to liquid Pressure due to liquid level = × /2 6 10 Where ρ=Density of liquid H=Height of liquid level Step-2: Calculate the minimum shell thickness considering hoop or circumferential stress when the shell is under internal pressure.5 < 0. Total internal pressure. .6) . SUMMARY OF DESIGN PROCEDURE FOR SHELL Step-3: Calculate the minimum shell thickness considering longitudinal stress when the shell is under internal pressure. t = maximum (thoop .5 < 1.25 . = + () = + . . = .4) < 0.tlong) . (2 + 0. Step-4: Select the maximum thickness as obtained from the step-1 & 2. . Then consider one of the case from below conditions.SUMMARY OF DESIGN PROCEDURE FOR SHELL Step-5: Calculate the allowable external pressure when the shell is under external pressure. Calculate the ratio Do/t assuming the thickness obtained in step 4. Case-I: External Pressure for Cylinders with Case-II: External Pressure for Cylinders with 0 0 ≥ 10 < 10 Follow the steps as described in the section design of cylindrical shell under external pressure. or (b) Elect to use stiffening rings to reduce the L dimension.SUMMARY OF DESIGN PROCEDURE FOR SHELL Step-6: Select the assumed thickness if Pallowable > Pexternal . But if Pallowable < Pexternal Either (a) select a new thickness and start the procedure from the beginning to satisfy the design. Step-6(a) Select a new thickness and repeat step-4 to 6 for calculating allowable pressure Step-6(b) Calculation for the use of stiffening rings i) Taking number of stiffening rings = n ii) Now. = +1 iii) Repeat step-4 to 6 for calculating allowable pressure using new value of L. . [8] .Fig: A pressure vessel with the use of stiffening rings. Calculation Program using Mathcad. Program 2: Design of shell under external pressure . Program 1: Design of shell under internal pressure. comparison and validation • Conclusion .POST SEMINAR PROSPECT WILL COVER • • • • • Design of Stiffening rings Design of Heads Design of Nozzles Design of various types of supports Programming the various design procedure and calculation involved. • Sample data results. Dr. ASME Press New York.Thakkar. CRC Press. Moss.1. Gulf Professional Publishing (An imprint of Elsevier) 6. Philip Ellenberger PE. Bednar. 2nd Edition-2001. Bansal. 4. A Textbook of Strength of Materials. Bryce E. Pressure Vessel Design Manual. 8. DESIGN OF PRESSURE VESSEL USING ASME CODE.Hill Professional Engineering 3. 9. Pressure Vessel Design and Practice. 8th edition. An international code 2010 ASME Boiler & Pressure Vessel Code. 3rd Edition-2004. Pressure Vessel Design Handbook. May 2013 2. Farr and Maan H. Tandel. Carson Sr. Nitant M. S. 2nd Edition-1991. International Journal of Advanced Engineering Research and Studies.References 1. SECTION VII DIVISON 1. Somnath Chattopadhyay. 4th Edition-2009. ASME New York . 2012. “Pressure Vessel Design. Guides & Procedures” 5. 2010 Edition. 7. Mc Graw. Guidebook for the design of ASME Section VIII pressure vessels.A. Pressure Vessels – The ASME code simplified.Thakkar.. Robert Chuse. Mohammad Ali Liaghat. Henry H. B. Rules for Construction of Pressure Vessels. A Review on Pressure Vessel Design and Analysis. J. Krigerer Publishing company James R. Jawad.Indian Journal Of Research. Dennis R.S. 10. Ghader Ghanbari. Div. Jigneshkumar M. Ali Sadeghian. Paripex . VII Section VIII. Parmar. R. K. Thank You .