DESIGN PROCEDURE FOR PRESSURE VESSEL

DESIGN PROCEDURE FOR PRESSURE VESSEL

TABLE OF CONTENTS S. NO TITLE PAGE NO 1. INTRODUCTION TO PRESSURE VESSELS 4 1.1. BASIC TERMINOLOGIES USED 5 1.2 CYLINDERS AND SPHERS 19 2. ANALYTICAL DESIGN OF METHANATOR 26 2.1 GIVEN DATA 28 2.2 REQUIRED DIMENTIONS OF METHANATOR 29 2.3 METHANATOR AS A THIN CYLINDER 30 2.4 THICKNESS OF SHELL 32 2.5 THICKNESS OF 2:1 ELLIPSOIDAL HEAD 34 1 2.6 OPENING IN THE PRESSURE VESSELS 35 2.7 SELECTION OF FLANGES 37 2.8 THICKNESS OF SKIRT OR DESIGN OF SUPPORTS 39 2.9 LOADINGS 44 2.10 STRESSES IN RESPONSE TO DIFFERENT LOADS 45 a) INTERNAL PRESSURE 45 b) WEIGHT 46 c) WIND LOAD 49 d) SEISMIC LOAD 54 2.11 COMBINATION OF STRESSES 57 2.12 COMPARISION 58 2.13 DESIGN OF ANCHOR BOLTS 58 2.14 WELDING OF PRESSURE VESSELS 62 3. ANALYSIS BY ANSYS 67 3.1 ANSYS 68 3.2 ANSYS INPUT METHODS 69 3.3 SHELL 51 70 3.4 ANALYSIS OF METHANATOR UNDER INTERNAL PRESSURE USING SHELL 51 71 3.5 ANALYSIS OF METHANATOR TO COMMAND WINDOW 72 3.6 ANALYSIS OF METHANATOR THROUGH GUI 72 3.7 TO FIND THE HOOP AND LONGITUDINAL STRESS ON ANSYS 88 3.8 DISPLACEMENTS OF NODES 91 2 4. COMARISION AND CONCLUSION 92 4.1 MEMBRENE STRESSE IN METHANATOR 93 4.2 COMARISION OF ANSYS AND ANALYTICAL SOLUTION 94 4.3 CONCLUSION 96 REFERENCES TABLES 3 INTRODUCTION TO PRESSUREVESSEL S 4 1.1 BASIC TERIMINOLOGIES USED VESSEL: A container or structural envelope in which materials are processed, treated, or stored; for example, pressure vessel, reactor vessel, agitator vessel, and storage vessels (tanks). PRESSURE VESSEL: A metal container generally cylindrical or spheroid, capable or withstanding various loadings. STRAIN: Any forced change in the dimensions of a body. A stretch is a tensile strain; a shortening is a compressive strain; an angular distortion is a shear strain. The word strain is commonly used to connote unit strain. STRESS: Internal force exerted by either of two adjacent parts of a body upon the other across an imagined plane of separation. When the forces are parallel to the plane, the stress is called shear stress; when the forces are normal to the plane the stress is called normal stress; when the normal stress is directed toward the part on which it acts is called compressive stress; when it is directed away from the part on which it acts it is called tensile stress. 5 STRESSES IN PRESSURE VESSEL: • Longitudinal S1 stress. • Circumferential (hoop) S2 stress. S1 and S2 called membrane (diaphragm) stress For vessel having a figure of revolution Bending stress Shear stress Discontinuity stress at an abrupt change in thickness or Shape of the vessel TENSILE STRENGTH: The maximum stress a material subjected to a stretching load can withstand without tearing. TENSILE STRESS: Stress developed by a material bearing tensile load. TEST PRESSURE: The requirements for determining the test pressure based on calculations are out lined in UG-99(c) for the hydrostatic test and UG-100(b) for the pneumatic test. The basis for calculated test pressure in either of these paragraphs is the highest permissible internal pressure as determined by the design formulas, for each element of the vessel using nominal thickness with corrosion allowances included and using the allowable stress values for the temperature of the test. (Code UA-60) 6 THERMAL STRESS: A self-balancing stress produced by a non uniform distribution of temperature or by differing thermal coefficients of expansion. Thermal stress developed in a solid body whenever a volume of material is prevented from assuming the size and shape that it normally should under a change in temperature. THICKNESS OF VESSEL WALL: 1. The “required thickness” is that computed by the formulas in this division, before corrosion allowance is added. 2. The “design thickness” is the sum of the required thickness and the corrosion allowance. 3. The “nominal thickness” is the thickness selected as commercially available, and as supplied to the manufacturer; it may exceed the design thickness. UNIT STRAIN: Unit tensile strain is the elongation per unit length; unit compressive strain is the shortening per unit length; unit shear strain is the change in angle (radians) between two lines originally at right angles to each other. UNIT STRESS: The amount of stress per unit of area. 7 WELD METAL: The metal resulting from the fusion of base metal and the filler metal. WELDING: The metal joining process in making welds. In the construction of vessels the welding process is restricted by the code (UW-27) as follows; 1. Shielded metal arc, submerged arc, gas metal arc, gas tungsten arc, atomic hydrogen metal arc, oxy fuel gas welding, electro-slag, and electron beam. 2. Pressure welding process: flash, induction, resistance, pressure Thermit, and pressure gas. YIELD POINT: The lowest stress at which strain increases without increase in stress. For some purpose it is important to distinguish between the upper yield point, which is the stress at which stress-stain curve first become horizontal, and the lower yield point, which is the somewhat lower and almost constant stress under which the metal continues to deform. Only a few materials exhibit a true yield point; for some materials the term is sometimes used as synonymous with yield strength. SPECIFIC GRAVITY: The ratio of the density of a material to the density of some standard material, such as water at a specified temperature, for example, 4 ° C or 60°F. Or (for gases) air at standard conditions of pressure and temperature. 8 STABILITY OF VESSEL: (Elastic stability) The strength of the vessel to resist buckling or wrinkling due to axial compressive stress. The stability of a vessel is severely affected by out of roundness. SHELL: Structural element made to enclose some space. Most of the shells are generated by the revolution of plane curve. SHEAR STRESS: The component of the stress tangent to the plane of reference. RADIUS OF GYRATION: The radius of gyration of an area with respect to given axis is the square root of the quantity obtained by dividing the moment of inertia of the area with respect to that axis by the area. RESIDUAL STRESS: Stress remaining in a structure or member as a result of thermal or mechanical treatment, or both. RESISTANCE WELDING: A pressure welding process wherein the heat is produced by the resistance to the flow of an electric current. 9 SECONDARY STRESS: A normal stress or a shear stress developed by the constraint of adjacent parts or by self-constraint of a structure. The basic characteristic of a secondary stress is that it is self-limiting. Local yielding and minor distortions can satisfy the conditions which cause the stress to occur and failure from one application of the stress is not to be expected. Examples of secondary stress are: general thermal stress; bending stress at a gross structural discontinuity. POISSONS’RATIO: The ratio of lateral unit strain to longitudinal unit strain, under the conditions of uniform and uniaxial longitudinal stress within the proportional limit. POSTWELD HEAT TREATMENT: Heating a vessel to a sufficient temperature to relieve the residual stresses which are the result of mechanical treatment and welding. Pressure vessels and parts shall be post weld heat treated. PREHEATING: Heat applied to base metal prior to welding operations. PRESSURE RELIEF VALVE: 10 [...]... be used in the design formulas given in the code (UG-23) MAXIMUM ALLOWABLE WORKING PRESSURE: The maximum gage pressure permissible at the top of a completed vessel in its operating position for a designed temperature This pressure is based on the weakest element of the vessel using nominal thickness exclusives of allowances for corrosion and thickness required for loading other than pressure (Code... pdL Resisting force = stress * resisting area And = fh * 2tL For equilibrium of cylinder Bursting force = Resisting force pdL fh = fh*2tL = pd/2t eq.(A) LONGTUDINAL STRESS: Cross sectional area =Π /4 d2 Total force at the end of cylinder = p* Π/4 d2 22 This force tries to burst the cylinder at the ends of cylinder and is called ‘bursting force’ Bursting force = F = p* Π/4 d2 Resisting force = stress... = r Force acting on elemental ring = p *area 21 = prδθL Vertical component of this force = prδθL Sinθ Total vertical force =prL 0∫180Sinθδθ = -prl (cos 180 – Cos 0) = 2prL = pdL eq.(1) But dL = horizontal projected area So Total vertical force = pdL = intensity of pressure * horizontal projected area This force tries to burst the cylinder into two halves and is called ‘bursting force’ Bursting force... efficiency In which case we use the formula for thickness is t = PR/ (2SE +.4P) As for methanator P < 0.385SE 33 435 < 0.385(16394.966) (1.0) 435 < 6312.06 Satisfied therefore hoop stress will be governing therefore design is based on the longitudinal joint & we find the thickness as follows t = PR / (SE – 0.6P) Where t = min required thickness of shell, in P = internal design pressure, psi R = inside radius... steel,= 0.3 Therefore, t2/t1 = 7/17 The maximum hoop stress will then occur in the ends, i.e f = pd/4t2 = (17/7) (pd/4t1) Which is greater than the hoop stress fh in the cylinder For equal maximum stress t2 should equal to 0.5 ANALYTICAL DESIGN OF METHANATOR 26 27 2.1 GIVEN DATA PARAMETETS:Working temperature = 364 °C Design temperature = 454 °C Working pressure = 380 Psi.g 28 Design pressure = 435 Psi.g... cylindrical or a spherical shell due to internal pressure or to distributed live load; bending stress in the central portion of a flat head due to pressure OPERATING PRESSURE: The pressure at the top of a vessel at which it normally operates It shall not exceed the maximum allowable working pressure and it is usually kept at a suitable level below the setting of the pressure relieving devices to prevent their... the vessel or 1 ½ the design pressure by agreement between the user and the manufacturer (Code UG-99) IMPACT STRESS: Force per unit area imposed to a material by a suddenly applied force IMPACT TEST: Determination of the degree of resistance of a material to breaking by impact, under bending, tensile and torsion loads, the energy absorbed is measured by breaking the material by a single blow GAGE PRESSURE: ... Cross-sectional area = Π /4d2 Bursting force = p* Π /4d2 Resisting force = stress * resisting area = f * dt For equilibrium of shell Bursting force = resisting force P * Π /4d2 = f * dt f = pd/4t CYLINDERICAL SHELL WITH HEMISPHERICAL ENDS: As shown in the fig let t1 be the thickness of the cylinder and t2 be the thickness of the hemisphere, the internal diameter being assumed the same for both STRESSES IN THE CYLINDERICAL... Where D = internal diameter in inches 2.6 OPENINGS IN A PRESSURE VESSEL The clause of the code concerning with the design of openings is UG-36(a) (b) a) shape of openings 1) Openings in cylindrical or conical portions of vessels, or in formed heads, shall preferably be circular, elliptical or round opening exceeds twice the short dimensions, the reinforcement across the short dimensions shall be increased... of the strength of a riveted, welded, or braze joint to the strength of the parent metal LOADING: Loading (loads) are the results of various forces The loadings to be considered in designing a vessel : internal or external pressure, impact loads, weight of the vessel, wind and earthquake, superimposed loads, local load, effect of temperature gradients.(Code UG-22) LOW-ALLOY STEEL: A harden able carbon . treated, or stored; for example, pressure vessel, reactor vessel, agitator vessel, and storage vessels (tanks). PRESSURE VESSEL: A metal container generally. basis for calculated test pressure in either of these paragraphs is the highest permissible internal pressure as determined by the design formulas, for