Embed Size (px)
Citation preview
COMPUTER AIDED INTERACTIVE PRESSURE VESSEL DESIGN
TEOH SUN JIE
A report submitted in partial fulfillment of the requirements
for the award of the
Bachelor of Mechanical Engineering.
Faculty of Mechanical Engineering
Universiti Malaysia Pahang
NOVEMBER 2008
ii
SUPERVISOR’S DECLARATION
We hereby declare that we have checked this project and in our opinion this project is
satisfactory in terms of scope and quality for the award of the degree of Bachelor of
Mechanical Engineering.
Signature : _______________________________
Name of supervisor : MOHD. RUZAIMI BIN MAT REJAB
Position : LECTURER
Date : 7 NOVEMBER 2008
Signature : _______________________________
Name of panel : DR. MD. MUSTAFIZUR RAHMAN
Position : LECTURER
Date : 7 NOVEMBER 2008
iii
STUDENT’S DECLARATION
I hereby declare that the work in this thesis is my own except for quotations and
summaries which have been duly acknowledged. The thesis has not been accepted
for any degree and is not concurrently submitted for award of other degree.
Signature : __________________
Name : TEOH SUN JIE
ID Number : MA05026
Date : 7 NOVEMBER 2008
iv
To my beloved father and mother
Mr. Teoh Lam Ho
Madam Chi Siew Yoong
v
ACKNOWLEDGEMENTS
In preparing this thesis, I would like to express my sincere appreciation to my
supervisor, Mr. Mohd. Ruzaimi Bin Mat Rejab for his invaluable guidance, viable
ideas, advices, and continuous supports. Not forgotten, my gratitude to my co-
supervisor, Madam Azlyna Binti Senawi for her guidance and commitments.
Without their dedications and continuous supports, this thesis would not been the
same as presented here.
Beside that, I am thankful to the lecturers and lab instructors in Faculty of
Mechanical Engineering, UMP whose lending their hands in the process of
completing this report. My fellow friends should also be recognized for their
supports. My sincere appreciation also extends to those assisted me in various
occasions. Lastly, my gratefulness toward my beloved family members.
vi
ABSTRACT
Designing a pressure vessel using a handbook is troublesome and not
interactive. Therefore computer aided software is created to assist the users, however
due to business benefit, the computer aided software for designing pressure vessel
are not for sale or pricey. This project is to develop an interactive system to design
pressure vessels besides the understanding of the algorithm in designing pressure
vessel. Results generated by the system were to compare with manual calculations
using ASME VIII-1 design code. Beside that, a finite element model was created
using the results generated by the system and the maximum stress value in finite
element analysis was to compare with theoretical calculation. This project includes
comparison studies to compare self defined material with material library,
comparison for self defined load with load from substance library and comparison
for substance library liquid with substance library gas. Software Microsoft Visual
Basic 6.0 is used for the purpose of building the interactive interfaces and processing
the data. The system applied formulae from ASME VIII-1 design code and the finite
element analysis is using software ALGOR V16. As a conclusion, designing a
pressure vessel using computer aided tool is easier and interactive beside low time
consumption, therefore, the project Computer Aided Interactive Pressure Vessel
Design is able to contribute to the human kind beneficial and should extend the study
to become a tool that able to design for all kind of pressure vessel.
vii
ABSTRAK
Proses mereka bekas tekanan menggunakan buku panduan adalah sukar dan
tidak interaktif, maka perisian alat bantuan komputer telah dicipta untuk membantu
pengguna dalam menyelesaikan masalah tersebut. Namun disebabkan kepentingan
dalam perniagaan, perisian tersebut selalunya sulit ataupun dijual dengan harga yang
mahal. Kajian ini bertujuan untuk mecipta satu sistem yang interaktif di samping
memahami algoritma dalam rekaan bekas tekanan. Untuk memastikan sistem
tersebut memberikan hasil yang tepat, hasil daripada sistem tersebut akan
dibandingkan dengan pengiraan manual dalam kod ASME VIII-1. Perbandingan juga
dilakukan untuk teori dengan analisis unsur terhingga dalam model yang direka
menggunakan data daripada sistem. Kajian turut dilakukan untuk membuat
perbandingan di antara bahan logam yang didefinisikan oleh pengguna dengan bahan
logam daripada perpustakaan bahan logam, perbandingan di antara beban (tekanan
dalam) yang didefinisikan oleh pengguna dengan beban yang dijana daripada
perpuskataan bahan dan perbandingan di antara perpustakaan bahan cecair dengan
perpustakaan bahan gas. Perisian Microsoft Visual Basic 6 digunakan untuk
membuat pengantara muka dan pemprosesan data. Pengiraan di dalam sistem
menggunakan formula dari Kod ASME VIII-1 dan perisian ALGOR V16 digunakan
untuk tujuan analisis unsur terhingga. Sebagai kesimpulan, mereka bekas tekanan
menggunakan alat batuan computer adalah menyenangkan, interaktif dan jimat masa,
nescaya projek alat batuan reka bekas tekanan interaktif adalah bermanfaat dan
kajian seharusnya diteruskan supaya projek ini mampu mereka untuk semua jenis
bekas tekanan.
viii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
TITLE i
SUPERVISOR’S DECLARATION ii
STUDENT’S DECLARATION iii
ACKNOWLEDGEMENTS v
ABSTRACT vi
ABSTRAK vii
TABLE OF CONTENTS viii
LIST OF TABLES xii
LIST OF FIGURES xiii
1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problem Statement 2
1.3 Objectives 3
1.4 Project Scope 3
1.5 Project Limitations
2 LITERATURE REVIEW 4
2.1 Introduction 4
2.2 Establishing Minimum Shell Thickness 4
2.2.1 Establishing Minimum Shell
Thickness by Table and Chart 5
ix
2.2.2 Establishing Minimum Shell
Thickness by Formulae 6
2.3 Establishing Minimum Head Thickness 9
2.3.1 Minimum Head Thickness for
Hemispherical Head 9
2.3.2 Minimum Head Thickness for
Torispherical Head 10
2.3.3 Minimum Head Thickness for
Ellipsoidal Head 11
2.4 Head Volume 12
2.5 Allowable Stress 13
2.6 Calculation for Load (Internal Pressure) 14
2.6.1 Static Fluid Pressure 14
2.6.2 Static Gas Load 16
2.7 Hoop Stress in Thin Walled Pressure Vessels 19
3 METHODOLOGY 21
3.1 Introduction 21
3.2 Operation Flowchart of the System 22
3.3 Computer Programming and Interfaces 23
3.3.1 Computer Programming 23
3.3.2 Interfaces in Microsoft Visual Basic 6 25
3.4 Comparing the System Results with ASME
Code VIII-1 27
3.5 Comparing Finite Element Analysis and
Theoretical Calculation 27
3.6 Comparing the System with Existing Work 28
x
4 RESULT AND DISCUSSION 29
4.1 Introduction 29
4.2 Samples and Results 29
4.2.1 Sample 1. Designing a Pressure Vessel
using Self Defined Material and Self
Defined Load (Internal Pressure) 30
4.2.2 Sample 2. Design a Pressure Vessel
using Material Library and Liquid Load 35
4.2.3 Sample 3. Design a Pressure Vessel
using Material Library and Gas Load 39
4.3 Hoop Stress in Thin Walled Pressure Vessels 44
4.3.1 Theoretical Calculation for Hoop Stress 44
4.3.2 Finite Element Analysis (ALGOR V16)
for Hoop Stress 45
4.4 Comparison and Validation 46
4.4.1 Comparison for Self Defined Material
and Material Library 46
4.4.2 Comparison for Self Defined Load and
Substance Library 46
4.4.3 Comparison for Substance Library
Liquid and Substance Library Gas 47
4.4.4 Comparison and Validation of
Theoretical Calculation with Interactive
Computer Aided Pressure Vessel Design
System. 48
4.4.5 Comparison of Theoretical Calculation
and Finite Element Analysis 49
xi
4.4.6 Comparison of Existing Work and the
System Created 50
5 CONCLUSION 52
5.1 Summary of the Project 52
5.2 Recommendation 54
REFERENCES 55
xii
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Shell thickness table 5
2.2 Constant factor at various stresses 5
2.3 Head volume in unit meter 12
2.4 Head volume in inches 12
2.5
2.6
2.7
Criteria for establishing allowable stress value for VIII-1
Material properties-yield strength (shear)
Substance properties – density
13
14
15
2.8 Molar mass, gas constant and critical-point properties 18
4.1 Results for Example 1 48
4.2 Results for Example 2 48
4.3 Results for Example 3 49
4.4 Comparison of theoretical calculation and finite element
analysis 49
xiii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1 Shoes factory after boiler explosion of March 20, 1905 2
2.1 Constant factor versus stress 6
2.2 Hoop stress, σ1 7
2.3 Hemispherical head 9
2.4 Torispherical head 10
2.5 Ellipsoidal head 11
2.6 Static fluid pressures in various shapes 15
2.7 Horizontal inflection point at the critical point 17
2.8 Diagram defining Hoop stress, σ1 20
3.1 Operation Flowchart of the System 22
3.2 Substance Library 24
3.3 Welcoming interface and the limitation of the system 25
3.4 Input interface for dimensions and yield strength 25
3.5 Input interface for substance liquid or gas 26
3.6 Interface for the results 26
3.7 Finite element model 27
4.1 Input interface for dimensions, material and yield
strength 30
4.2 Input interface for self defined material and self defined
load 31
4.3 Interface for choosing pressure vessel head 32
4.4 Material definitions for Hemispherical head 33
4.5 Results for Sample 1 34
4.6 Input interface for dimensions and allowable stress using
material library 35
xiv
4.7 Input interface using substance library (liquid) 36
4.8 Material definitions for Ellipsoidal head 37
4.9 Results for Example 2 39
4.10 Input interface for dimensions and allowable stress using
material library 40
4.11 Input interface for user to insert substance using
substance library (gaseous), specific volume and
operating temperature. 41
4.12 Material definitions for Torispherical head 42
4.13 Results for Example 3 43
4.14 Concept model 45
4.15 Finite element analysis and result 45
4.16 Flowchart for generating load for liquid and gaseous
substance 47
4.17 Interface created using FORTRAN (Existing work) 50
4.18 Input data and result (Existing work) 51
CHAPTER 1
INTRODUCTION
1.1 Introduction
Pressure vessels are leak proof containers used to hold gases or liquids at a
pressure different from the ambient pressure. The end caps fitted to the cylindrical
body are known as heads.
Pressure vessels are used in various fields such as chemical industry,
pharmaceutical industry, oil and fuel industry, and plastic industry. Other example of
pressure vessels are diving cylinder, recompressed chamber, distillation towers,
nuclear reactor vessel, hydraulic reservoir and storage vessels for liquefied gases
such as ammonia and chlorine.
An inadequately designed pressure vessels are hazardous and can cause lose
of life. Figure 1.1 shows an accident due to inadequately designed pressure vessel,
killing 58 persons and injured 117 others. Therefore, design codes are being
introduced for the pressure vessel design, safety factor is applied in the design to
offer higher reliability of the pressure vessel. Commonly used design codes are
ASME Boiler and Pressure Vessel Code, the Pressure Equipment Directive of EU
(PED), Japanese Industrial Standard (JIS), CSA B51 in Canada, AS1210 in Australia
and other international standards.
2
Figure 1.1 Shoes factory after boiler explosion of March 20, 1905 [1]
In this research, an interactive pressure vessel design system will be
developed. Users will be offered a user friendly and interactive interface to insert the
data and the system will generate adequate information to build the pressure vessel.
For example the user provides length and diameter, thus the system will generate the
maximum capacity for the pressure vessel. Beside that, users no need to provide
density for each material used since the system will have a list of materials together
with density to be chosen in building the pressure vessel.
The system is developed base on ASME Code Section VIII, Division 1.
Theoretical calculation and finite element analysis will be used to support this study.
1.2 Problem Statement
Most of the methods available to design pressure vessel are in handbook
where they are troublesome and not interactive. Although there are computer aided
pressure vessel design available in the market, but due to business benefit, the system
may not be saleable or pricey. In addition the formulas and concepts applied in the
system are always unknown by the users.
3
1.3 Objectives
i. To build an interactive system using computer programming system to
design pressure vessel.
ii. To compare results of design analysis in the system with the ASME
VIII-1 design code
iii. To validate the results in the system using theoretical calculation and
finite element analysis.
1.4 Project Scopes
i. To build an interactive computer aided pressure vessel design using
Microsoft Visual Basic 6.0
ii. To build pressure vessel design system according to rule, ASME Code
section VIII-1
iii. To compare results of design analysis in the Interactive Computer
Aided Pressure Vessel Design System with the ASME VIII-1 design
code.
iv. To compare the result in theoretical calculation with finite element
analysis (ALGOR V16).
1.5 Project Limitations
i. Design by rule, ASME Code section VIII-1
ii. Cylindrical horizontal orientated
iii. Only subjected to static internal load
iv. Corrosion allowance is zero
v. Weldments efficiency is considered 100%
vi. No attachments/ special components on the pressure vessel
vii. Three types of head (Hemispherical, Ellipsoidal and Torispherical
head)
4
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
In this section, design rules in ASME code VIII-1, allowable stress,
calculations of internal pressure and hoop stress theory will be reviewed. ASME
Code Section VIII provides requirements applicable to the design, fabrication,
inspection, testing, and certification of pressure vessels by utilizing formulas, charts,
tables and graphs to establish the minimum thickness of pressure vessel.
2.2 Establishing Minimum Shell Thickness
ASME code section VIII-1 is used to establish the minimum thickness in the
pressure vessel design. ASME code section VIII-1 is chosen in this study because
ASME design code is one of the most widely used in the world and its reliability.
Below is the utilities used to design pressure vessel by ASME Code VIII-1.
5
2.2.1 Establishing Minimum Shell Thickness by Table and Chart
Table 2.1 is used to establish minimum shell thickness for joint efficiency =
1.0, allowable stress value = 13800 psi and unit in Inches.
Table 2.1: Shell thickness table [1]
INSIDE DIAMETER, IN.12. 18. 24. 30. 36. 42. 48. 54. 60.
psi15 0.007 0.010 0.013 0.016 0.020 0.023 0.026 0.029 0.03320 0.009 0.013 0.017 0.022 0.026 0.030 0.035 0.039 0.04425 0.011 0.016 0.022 0.027 0.033 0.038 0.044 0.049 0.05430 0.013 0.020 0.026 0.033 0.039 0.046 0.052 0.059 0.06535 0.015 0.023 0.030 0.038 0.046 0.053 0.061 0.069 0.07640 0.017 0.026 0.035 0.044 0.052 0.061 0.070 0.078 0.08745 0.020 0.029 0.039 0.049 0.059 0.069 0.078 0.088 0.09850 0.022 0.033 0.044 0.054 0.065 0.076 0.087 0.098 0.109
Steps to establish minimum shell thickness:
1. Determine the right table according to the desired joint efficiency.
2. Locate the desired diameter.
3. Locate the desired pressure.
4. Read the thickness value corresponding to the diameter and internal
pressure.
Table 2.1 is based on allowable stress value 13,800 psi. For other stress
values, the thickness read is multiply by the following constant factors in Table 2.2
or factors read from the graph. Figure 2.1 shows graph for constant factor versus
stress.
Table 2.2: Constant factor at various stresses [1]
Stress, psi 11300 12500 13800 15000 16300 17500 18800Constant 1.224 1.105 1.000 0.919 0.846 0.787 0.733
6
Figure 2.1 Constant factor versus stress [1]
If a constant factor for an allowable stress is not given, equation 2.1 [1] is
applied:
1.003stress)(Allowable
14178factorConstant (2.1)
2.2.2 Establishing Minimum Shell Thickness by Formulae
In the Beer [2] studies, an equation applying Hoop stress concept is derived to
establish minimum shell thickness in a thin cylinder, given by:
SE
PRts
where ts = minimum shell thickness
P = internal pressure
S = allowable stress
E = joint efficiency
R = inside radius
7
Figure 2.2 shows the Hoop stress induced on the circumference section when
an internal pressure applied on the pressure vessel.
Figure 2.2 Hoop stress, σ1 [2]
ASME applied equation 2.2 to establish minimum shell thickness [2].
PSE
PRts 6.0 (2.2)
The difference is the additional term of 0.6P in the denominator. This term
was added by the ASME to take into consideration of the nonlinearity in stress that
develops in thick cylinder [2]. This make the equation is valid for thin and thick
cylinder.
A more accurate equation that determines the thickness in a thick cylinder,
known as Lamé’s equation, is given by:
ts = R (Z0.5 – 1)
where PSE
PSEZ
σ1
8
A sample problem is used to compare the difference using equation in ASME
code and Lamé’s equation.
Sample problem [2]:
Calculate the required shell thickness of an accumulator with P = 8000psi, R = 20in,
S = 20000psi and E = 1.0.
Equation in ASME Code
PSE
PRts 6.0
)8000(6.0)1)(20000(
)20)(8000(
st
ts = 10.526in
Lamé’s equation
PSE
PSEZ
800020000
800020000
Z
3333.2Z
ts = R (Z0.5 – 1)
ts = 20 (2.33330.5 – 1)
ts = 10.550in
The comparison demonstrates the accuracy of equation in ASME code over a
wide range of R/t ratios.
9
2.3 Establishing Minimum Head Thickness
Computer Aided Interactive Pressure Vessel Design System that will be
developed in this project provides three heads to be chosen by user. They are
Hemispherical, Ellipsoidal and Torispherical head.
2.3.1 Minimum Head Thickness for Hemispherical Head
Hemispherical head having sphere shape which is the ideal shape for a head,
because the pressure in the vessel is divided equally across the surface of the head.
Figure 2.3 Hemispherical head
Minimum head thickness, th [1] of a thin spherical shell due to internal
pressure is given by:
PSE
PRth 2.02 (2.3)
where th = minimum head thickness
P = internal pressure
S = allowable stress
E = joint efficiency
R = inside radius
10
As the ratio t/R increase beyond 0.356, the thickness given by (2.3) becomes
non conservative. The ASME VIII-1 equation for thick spherical shell [2] is given
by:
th = R (Y1/3 – 1) (2.4)
where PSE
PSEY
2
2
2.3.2 Minimum Head Thickness for Torispherical Head
Common Torispherical head can be approximated by a spherical radius, L of
1.0D and a knuckle radius of 0.06D [3].
Figure 2.4 Torispherical head
Minimum head thickness, th [1] is obtained from the following equation:
PSE
PLth 1.0
885.0
Where L = D + 2t
