A Seminar on Design of Pressure Vessel
A Seminar onDesign of Pressure VesselBy: 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 EngineeringSchool of EngineeringGautam
Buddha UniversityGreater Noida (U.P.)Seminar HighlightsIntroduction
to Pressure Vessels and its classificationComponents of Pressure
VesselsASME Codes Design software and industrial
applicationsMaterials SelectionStress in Pressure VesselsDesign of
cylindrical shell.Calculation Program1. 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 [3] COMPONENTS OF
PRESSURE VESSELSThe main components of pressure vessel are [4]
ShellHeadsNozzlesStiffening ringsSupports
Photo courtesy: www.theculminates.comShellThe shell is the
primary component that contains the pressure. Pressure vessel
shells are welded together to form a structure that has a common
rotational axis.Most pressure vessel shells are cylindrical,
spherical and conical in shape
HeadAll pressure vessel shells must be closed at the ends by
heads (or another shell section). Heads are typically curved rather
than flat. Curved configurations are stronger and allow the heads
to be thinner, lighter, and less expensive than flat heads. Heads
are usually categorized by their shapes.
Fig: Different types of heads. (Modified from ASME Boiler and
Pressure Vessel Code, ASME, New York.)SupportThe type of support
that is used depends primarily on the size and orientation of the
pressure vessel. the pressure vessel support must be adequate for
the applied weight, wind, and earthquake loads.Typical kinds of
supports are as follow:a. Skirtb. Legc. Saddled. Lug
Photo courtesy:
www.pressurevesslesconsulting.comSaddleLegSkirtLug
Figure showing various pressure vessel supports.NozzleA nozzle
is a cylindrical component that penetrates the shell or heads of a
pressure vessel. The nozzle ends are usually flanged to allow for
the necessary connections and to permit easy disassembly for
maintenance or access. Nozzles are used for attaching piping for
flow into or out of the vessel and attach instrument connections,
(e.g., level gauges, thermowells, or pressure gauges).
Stiffener RingsRings made of flat bar or plate or structural
shapes welded around the Circumference of the vessel. These rings
are installed on vessels operating under external pressure to
prevent collapse of the vessel.
Photo courtesy: www.pressurevesslesconsulting.comFollowing parts
of ASME Code SECTION VIII DIV-1 are used in design [5]U-1Scope for
the design of pressure vesselsUG-16General regarding
designUG-20Design temperatureUG-21LoadingsUG-22Maximum allowable
stressesUG-23Maximum allowable stressesUG-27Thickness of shells
under internal pressureUG-28Thickness of shells under external
pressureUG-29Stiffening rings for cylindrical shells under external
pressureUG-32Formed heads, pressure on concave sideUG-33Formed
heads, pressure on convex side. Graph in Appendix VUG-45Nozzle neck
thicknessUW-12Welded Joint efficienciesUG-45Nozzle neck
thicknessUW-12Welded Joint efficienciesAppendix VCharts for
determining shell thickness of cylindrical and spherical vessels
under external pressureDESIGNING A PRESSURE VESSEL IN INDUSTRY
Software used in designing the pressure vessels: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, accurately and
profitably.
Fig:Screenshot of PV-Elite Software2. Materials
SelectionSelection of materials The broad classification of these
materials can be done in following categories: 1. Boiler Quality
Materials 2. Structural Quality Materials 1. Boiler Quality
Materials [5]These are the materials employed for pressure carrying
components. a) Carbon Steel Principal element is carbon, generally
ranging from 0.2 to 0.4.b) Low Alloy Steel Alloying elements are
used, but the total alloy content is limited to generally 5 %.c)
High alloy steel heavy alloying is done for example Stainless
Steels.Commonly used stainless steels for refinery, petrochemical
services are:-Austenitic Stainless Steels Ferritic Stainless
Steels.
2. Structural Quality Materials [5]These are the materials
employed for very general services and nonpressure services. The
Structural quality materials are generally only of Carbon
steel.They are very economical .Material testing for Pressure
vessel [5]PWHT Post Weld Heat Treatment. Radiographic testing is
done of the welding joints according to the pressure vessel.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.After this test heat treatment is done on the
welding joints to relieve the stresses.Recommended for corrosive
services like HS, amine, caustic services etc.
Impact Testing The impact testing of materials is done to take
care of low temperature service. This is because the material tend
to become more brittle at low temperature. Charpy V notch impact
test is the most common type of test used.
3. Stresses in PressureVesselsMainly there are 2 types of
stresses involved in a pressure vessel
Primary stressPrimary 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. They are produced by mechanical loads and are the most
hazardous of all types of stress.
Types of primary general stress1.Primary general membrane
stress, P : a. Circumferential and longitudinal stress due to
pressure.b. Compressive and tensile axial stresses due to wind.2.
Local primary membrane stress, PLIt is the combination of primary
membrane stress, P, plus secondary membrane stress, Q, produced
from sustained loadings.
2. Secondary stressSecondary 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. Types
of secondary stresses:1. Secondary membrane stress, QThese are the
stress which area. Thermal stresses.b. Membrane stress in the
knuckle area of the head.c. Membrane stress due to local loads.2.
Secondary bending stress, QLThese include :a. Bending stress at a
gross structural discontinuity:b. The stress variation of the
radial stress due to internal pressure.d. Discontinuity stresses at
stiffening or support rings.
STRESS/FAILURE THEORIES [5]
The major theories of failures used to design a pressure vessel
are :
Maximum principle stress theory: Both ASME Code, Section VIII,
Division 1, and division use the maximum stress theory as a basis
for design. While it accurately predict failure in brittle
materials, but it is not always accurate for ductile materials.
2. Maximum shear stress theoryThis theory asserts that the
breakdown of material depends only on the maximum shear stress
attained in an element. It is mainly used for Ductile material
Major Failures associated with pressure vessel can usually be
classified as 5 types :1. EXCESSIVE ELASTIC DEFORMATIONIt is a type
of expansion of vessel till limit of proportionality.It affects the
volume and density of fluid inside the vessel, hence the purpose of
the vessel will fail and effect the process. So excessive elastic
deformation is undesirable.2. 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.Elastic instability in
vessels is usually associated with the use of thin shells.Plastic
instability3. BRITTLE RUPTURE :If the material used for the vessel
is brittle than instead of plastic or elastic deformation, vessel
will ruptured instantly after increasing the slight load after
yield point. Hence for brittle material stresses should be kept low
below the yield point.
MAJOR FAILURES ASSOCIATED WITH PRESSURE VESSELS [5]4.
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 starts initially from grain
boundary where abnormal grains are there. It increases to cracks in
the material after some time and finally material fails on load
much lower than the yield point stress.
5. CORROSION:If excessive corrosion occurs than material
thickness will decrease constantly and after a certain limit the
material will failDue to this the vessels are provided with
corrosion allowance thickness. Generally taken 3mm at inside
boundary layer. At outside some corrosion resistant material are
used to prevent the rusting.
4. Design of Shell
E = Joint Efficiency FactorP = internal pressure (kg/cm2).Ri, Ro
= inside and outside radius with corrosion allowance. (in)Di, Do =
inside and outside diameter.S = allowable stress in the materialt =
thickness of the cylinder (mm)=Density of liquid H=Height of liquid
levelCA = Corrosion allowancen = number of stiffening ringsLeff =
Overall effective length of pressure vesselL = Length of pressure
vesselhoop= Hoop or circumferential stresseslong= Longitudinal
stressesPa, Pa1, Pa2 = Allowable external pressureVESSEL
NOMENCLATUREShell DesignBasically the design of shell consists of
following steps-Design of shell under internal pressure.Minimum
thickness is calculated using ASME Boiler and Pressure Vessel Code,
Section VIII Division 1, UG-27. Design of shell under external
pressure.For a optimum thickness the pressure vessel under external
pressure is analyzed for satisfying the design using ASME BPV Code,
Sec. VIII Div. 1, UG-28. Or for the optimum thickness no. of
stiffening rings is calculated.12PiPeDesign of cylindrical shell
under external pressureSteps [9]-Assume a value of t for the
cylinder.Calculate the quantities L/Do and Do/t.Use Fig. with the
calculated values of L/Do and Do/t and establish an A value.Use an
External Pressure Chart to determine the A value and determine the
B value from the appropriate temperature chart.Calculate the
allowable external pressure from the equation
When A falls to the left of the curves, the value of Pa is
determined from
Compare the calculated value of Pa (Allowable Pressure) obtained
in Steps 6 or 7 with P. If Pa is smaller than P, select the
thickness. if Pa > P assumed thickness is optimum
FACTOR A CHART [5]FACTOR B CHART [5]
SUMMARY OF DESIGN PROCEDURE FOR SHELL
SUMMARY OF DESIGN PROCEDURE FOR SHELLStep-4: Select the maximum
thickness as obtained from the step-1 & 2. t = maximum (thoop
,tlong) SUMMARY OF DESIGN PROCEDURE FOR SHELLSUMMARY OF DESIGN
PROCEDURE FOR SHELLFig: A pressure vessel with the use of
stiffening rings. [8]
Calculation Program using Mathcad.Program 1: Design of shell
under internal pressure.
Program 2: Design of shell under external pressure
POST SEMINAR PROSPECT WILL COVERDesign of Stiffening ringsDesign
of Heads Design of NozzlesDesign of various types of
supportsProgramming the various design procedure and calculation
involved.Sample data results, comparison and
validationConclusionReferencesNitant M. Tandel, Jigneshkumar M.
Parmar, A Review on Pressure Vessel Design and Analysis, Paripex -
Indian Journal Of Research, May 2013J. Philip Ellenberger PE,
Robert Chuse, Bryce E. Carson Sr., Pressure Vessels The ASME code
simplified, 8th edition, Mc Graw- Hill Professional
EngineeringB.S.Thakkar, S.A.Thakkar, DESIGN OF PRESSURE VESSEL
USING ASME CODE, SECTION VII DIVISON 1, International Journal of
Advanced Engineering Research and Studies, 2012.Ghader Ghanbari,
Mohammad Ali Liaghat, Ali Sadeghian, Pressure Vessel Design, Guides
& ProceduresDennis R. Moss, Pressure Vessel Design Manual, 3rd
Edition-2004, Gulf Professional Publishing (An imprint of
Elsevier)Dr. R. K. Bansal, A Textbook of Strength of Materials, 4th
Edition-2009.Somnath Chattopadhyay, Pressure Vessel Design and
Practice, CRC Press.Henry H. Bednar, Pressure Vessel Design
Handbook, 2nd Edition-1991. Krigerer Publishing companyJames R.
Farr and Maan H. Jawad, Guidebook for the design of ASME Section
VIII pressure vessels, 2nd Edition-2001, ASME Press New York.An
international code 2010 ASME Boiler & Pressure Vessel Code,
2010 Edition, VII Section VIII, Div.1, Rules for Construction of
Pressure Vessels, ASME New York
Thank You