design and analysis of vertical pressure vesseljoics.org/gallery/ics-2639.pdf · 2 assistant...

DESIGN AND ANALYSIS OF VERTICAL PRESSURE VESSEL

D. Balaji1, G.S. Vivek2

1PG Scholar, Department of Mechanical Engineering, Chadalawada Ramanamma

Engineering College, Tirupati-517502, Andhra Pradesh, India

Email: [email protected]

2 Assistant Professor, Department of Mechanical Engineering, Chadalawada

Ramanamma Engineering College, Tirupati-517502, Andhra Pradesh, India

Abstract. This technical paper presents the design and structural analysis of Vertical

pressure vessel (Volume tank) to understand the structural behaviour of pressure

vessels under various loading conditions. In a pressure vessel high pressures are

developed during its operations and it has to with stand severe forces. In the design of

pressure vessel safety is the primary consideration, due the potential impact of possible

accidents at working environment. There have a few main factors to design the safe

pressure vessel. Efforts are made in this paper to design a Solid model as per ASME

Code & Standard guide lines and analysis has been carried out at various pressure

conditions by using ANSYS to analyse the safety parameter of allowable working

pressure and Max. Allowable stress. The bursting of the vessel are probability occur at

maximum pressure which is the element that only can sustain that pressure.

Keywords: Pressure Vessel; Volume tank; ASME BPVC; Solid works; ANSYS.

1. INTRODUCTION

Tanks, vessel and pipelines that carry, store or receive flu-ids are called pressure vessel. 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. As high operating pressures are a danger,

utmost care should be taken while designing the pressure vessels. Any mechanical structure

fails if there are stresses induced in them. The pressure vessel life under cyclic load is related

to the number of cycles it is exposed to and to the intensity of the stress [9]. The pressure vessel

is assumed to be a thin cylinder, and therefore the analysis follows the thin cylinder formulae.

The fluid inside the vessel may undergo a change in state as in the case of steam boiler or may

combine with other reagent as in the case of chemical reactor. Pressure vessel often has a

combination of high pressure together with high temperature and in some cases flammable

fluids or highly radioactive material. Because of such hazards it is imperative that the design

be such that no leakage can occur. In addition vessel has to be design carefully to cope with

the operating temperature and pressure.

Pressure vessels are usually spherical or cylindrical with dome end. The cylindrical vessels are

generally preferred because of the present simple manufacturing problem and make better use

of the available space. Boiler, heat exchanger, chemical reactor and so on, are generally

cylindrical.

The modelling was done on a modelling software Solid works, and a finite element analysis

was carried out to highlight the various points of stress concentration. As anticipated the highest

stress value occurs at the junction of the nozzle attachment, to analyze the aspects of stress

concentration which may develop when the end closure of a high-pressure vessel is attached to

a conically shaped nozzle. The main reason for this occurrence is that the conical nozzle must

Journal of Information and Computational Science

Volume 10 Issue 3 - 2020

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mailto:[email protected]

be connected separately. This process would result in geometrical discontinuities between the

pressure vessel and the nozzle at the point of attachment. The solution for the value of stress at

the connection of a cylindrical nozzle to an ellipsoidal shape pressure vessel. The stress

calculations were carried out using finite element method, and a parametric model was

developed.

The accuracy of a finite element model depends on how the mesh is. If the mesh is coarse, the

efficiency of the results decreases. At one point, we reach the point of diminishing returns

where no matter how good the mesh is, it won‘t have a significant effect on the accuracy of the

results. The mesh is said to be converged at this point. For all the models analyzed below,

convergence will be observed as the mesh get refined.

From the result, the convergence seen is a monotonous one rather than an oscillating one. As

the number of nodes and elements increases, the accuracy of the result also increases. From the

analysis, the maximum stress occurs at the junction of the nozzle and pressure vessel. High-

stress concentration is developed due to the abrupt change of the geometry and change in the

stress. Symmetry is a significant factor than some nozzles as it is observed that peak stress for

a symmetrical nozzle is very low and the stress increment factor also lowers.

The finite element analysis based workbench is used for analyzing pressure vessel components.

It discusses modelling methods for various parameters in a cracked pressure vessel. It also

gives few rules for performing analysis using fem like starting with a simple design and using,

closed-form solutions for analysis.

2. MODELLING:

SolidWorks is a 3D solid modelling Computer Aided Design (CAD) and Computer Aided

Engineering (CAE) program that runs on Microsoft Window, published by Dassault systems.

It is feature based, parametric solid modelling design tool that makes advantage in learning

windows graphical user interface easily. SolidWorks helps in creating fully associative 3D

solid models by enabling with or without constraint sketch features while utilizing automatic

or user-defined relations to capture design intent.

2.1 MODELLING OF VERTICAL PRESSURE VESSEL IN SOLIDWORKS:

Creation of 3D model of pressure vessel using SolidWorks software as per the required

dimensions. This contains individual part creation like Elliptical dish ends, Shell, leg supports

which requires the sectional views of the volume tank components drawn in the sketcher and

cylindrical cross section is obtained by using Revolve Boss feature. Selection of materials can

be done with the help of Material option in Feature manager tree area. The created parts are

assembled as per the requirement of the project.

2.2 DIMENSIONS OF THE SOLID MODEL:

In view of the conditions laid down in the objectives solid model has been created with the

given dimensions.



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Table 2.1: DESIGN DATA

DESCRIPTION VALUE UNIT

CONSTRUCTION CODE ASME VIII DIC.1 EDITION

2017

Design Pressure P 0.8 MPa

Operating Temperature T 50 to 65 oC

Design Temperature Td 132 oC

Min. Design Metal Temperature Tm

0 oC

Max. Allowable Stress at design temperature. (ASME

SEC II D) S 138 MPa

Joint Efficiency E 1.0 -

Corrosion Allowance CA 1.0 mm

Medium Air -

Vessel Size

ID Di 600 mm

Nominal Thickness t 10 mm

T/L - T/L L 1000 mm

Support Detail - Leg Support

PRESSURE VESSEL SHELL DESIGN THICKNESS CALCULATION:

Thickness of Shell under Internal Pressure as per ASME SEC VIII DIV 1 UG-27:

For Circumferential Stress tr =

=

P x R

S x E – 0.6P

= 3.3 mm

For Longitudinal Stress tr =

=

P * R

2S x E + 0.4P

= 2.9 mm

2.3 SOLIDWORKS PART MODELLING AND ASSEMBLY:

Elliptical Dish end Cylindrical Shell Pressure Vessel Assembly



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3. ANALYSYS:

We used ‘Finite Element Method (FEM) for the analysis of vertical pressure vessel. FEM is

widely used to solve problems of engineering mechanics. FEM is the numerical technique used

to perform analysis of many physical phenomenon. Structural & Fluid behaviour, thermal

transportation, wave propagation etc. processes are described using partial differential

equation. For a computer to solve PDE, one numerical technique have been developed, which

is called ‘Finite Element Method’. The geometry divided into thousands of small parts and

calculation is done on each part thousands of time, which is called as ‘iteration’. It uses some

mathematical approximation method to converge the solution. This method restricts some

‘Degrees of Freedom’ of the component when we select different boundary conditions like

fixed support or hinged supports etc.

FEM is a general method used for static, dynamic, fluid flow and heat flow analysis. We use

‘Static Structural Analysis’ for the vertical pressure vessel which means when the body is in a

Rigid condition fixed at some point and the given load is quasi(Very Slow), inertial forces can

be neglected. To restrict the motion of the component leg supports are fixed at some points and

applied particular amount of force to calculate Stress, Strain and Deformation. The procedure

for static analysis consists of these main steps.

1. Building the model

2. Obtaining the Solution

3. Validation of the results.

3.1 Material Properties 3.2 Mesh Data for Analysis

Fig 3.1: Mesh View Fig 3.2: Fixed Support Fig 3.3: Load Criteria

4. ANALYSIS OF PRESSURE VESSEL:

Static analysis is carried out at various locations such as Change in area of cross section, weld

zones of upper and lower elliptical dish, upper and lower nozzle connections to determine the

stress concentration, developed forces, Strain and displacements by keeping the thickness of

the vessel as constant (i.e. t = 10mm).

At Operating Pressure 8 Bar: (Change in area of cross section):

Material SA516 Gr 70

Density 7.8 g/cc

Young's Modulus 200 GPa

Poisson's Ratio 0.29

Min Yield Strength (ASME SEC IID) 260 MPa

Max. Allowable Stress at 65o C (ASME SEC IID) 138 MPa

Mesh Data for Analysis

Number of Nodes 2002375

Number of elements 1152760

Size Function Adaptive

Relevance Centre Medium

Element size 3 mm



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Equivalent Stress Equivalent Elastic Strain

At Operating Pressure 8 Bar: (Bottom nozzle Weld Zone)


At Operating Pressure 8 Bar: (Bottom Elliptical Dish End)




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At Operating Pressure 8 Bar: (Upper nozzle Weld Zone)


At Operating Pressure 8 Bar: (Upper Elliptical Dish End Weld Zone)


At Operating Pressure 8 Bar: (Complete Vessel)

Total Von-Mises Stress Total Equivalent Strain Total Deformation

Similarly the analysis is carried out at various pressure conditions and the results are obtained

as shown below.



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5. ANALYSIS RESULT

ANALYSIS RESULTS

S.No Point of Analysis Parameter Obtained results

At 8 bar At 10 bar 15 bar

1 Bottom Nozzle Weld

Zone

Equivalent Stress

Concentration in N/mm2 5.86 17.1 19.92

Equivalent Elastic Strain 3.7977x10-5 8.013x10-5 7.0161x10-5

2 Change in area of cross

section

Equivalent Stress


Total Strain 9.475x10-5 1.1847x10-4 1.7372x10-4

3 Upper Elliptical head

weld zone

Equivalent Stress


Total Strain 1.114x10-4 1.641x10-4 2.3273x10-4

4 Lower Elliptical weld

zone

Equivalent Stress


Total Strain 1.156x10-4 1.25x10-4 2.3008x10-4

5 Upper Nozzle weld

zone

Equivalent Stress


Total Strain 3.08x10-4 3.8545x10-4 5.7814x10-4

6 Complete Vessel

Total Von-Mises stress

(3D) 60.9 76.12 114.2

Total Equivalent Strain 3.08x10-4 3.854x10-4 5.7814x10-4

Total deformation 1.577x10-4 1.9818x10-4 2.9922x10-4

CONCLUSION:

In this way a case study has been performed by conducting a linear static analysis on a vertical

pressure vessel for stress analysis which carried out as per the ASME codes and from this



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analysis it is concluded that the FEA Analysis results shows that equivalent stress concentration

in pressure vessel at various pressure conditions are less than maximum allowable stress of the

SA 516 Gr 70 (i.e. 138 MPa at 65 Dec). This helps in understanding the max. Design pressure

that can be used to operate the pressure vessel. From the above results it is clear that the pressure

vessel can be operated till 15 bar above which the equivalent stresses will go higher than the

max. Allowable pressure which in turn lead to failure of pressure vessel. From this analysis,

the mechanical design of a pressure vessel can be easily verified by a third party organization

to ensure the quality of a pressure vessel system that it can easily fulfils the requirements as

per ASME codes and standards .

References

[1] Yun-Jae Kim, Kuk-Hee Lee and Chi-Yong Park, “Limit loads for thin-walled piping branch

junctions under internal pressure and in-plane bending ‟‟, International Journal of Pressure

Vessels and Piping 83 (2006) 645–653 [2] Z. F. Sang, et.al, “Limit & burst pressure for a cylindrical shell interaction with intermediate

diameter ratio”, International Journal of Pressure Vessel and Piping (Aug 2002), Vol. 79 pp.

341-349.

[3] ASME Boiler & Pressure Vessel Code, Section VIII Devision-1, “Rule for Construction of

Pressure vessel.” 2017 Edition,

[4] ASME Boiler & Pressure Vessel Code, Section VIII Devision-2, “Rule for Construction of

Pressure vessel.” 2017 Edition.

[5] ASME Boiler & Pressure Vessel Code, Section II Part- A, “Ferrous Material Specifications

(Beginning to SA-450)” 2017 Edition.

[6] ASME Boiler & Pressure Vessel Code, Section II Part- D, “Ferrous Material Specifications

(Beginning to SA-450)” 2017 Edition.

[7] ASME B16.25-2017 Buttwelding Ends.

[8] John F. Harvey, “Theory and Design of Modern Pressure Vessels”, Second Edit ion.



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