This document provides an overview of pressure vessels, including their definition, classifications, materials, and design considerations. Pressure vessels are closed containers designed to hold gases or liquids above atmospheric pressure. They are commonly used in industries like petroleum refining, chemicals, power generation, and food and pharmaceuticals. Key aspects covered include vessel geometry, installation, thickness calculations, testing requirements, and applicable codes and standards like the ASME Boiler and Pressure Vessel Code.

1. An Introduction to Pressure Vessels
Definition:A pressure vessel is a closed container designed to hold
gases/liquids at a pressure other than atmospheric pressure.

2. Pressure vessels used in: Petroleum refining plant
Chemical plant
Power plant
Food Industries
Pharmaceuticals Industries
Classification of Pressure vessels
Based on Geometry:
Spherical (Most Economical due to lower thickness),
Rectangular (Most Costly due to higher thickness),
Cylindrical (Easy Manufacturing).
Based on Installation: Horizontal, Vertical, Inclined.
Based on Pressure: Internal, External, Both (Jacketed vessels)
Based on Wall thickness: Thin wall(R/t >=10), Thick wall (R/t <10)

3. Based on Method of Manufacturing:
Welded:It is a fabrication process that joins metalsby producing arc between base
metal and electroderesulting hightemperature (melting point)causing base
metalto join by fusion.
Forged:Forging is a manufacturing process in which metal is heated to plastic limit
and reshaped using external load.This method is used generally for High pressure
vessels where shell/Head/SRN nozzles with flange etc. are made by forging to avoid
welding.
Brazed:Brazing is a manufacturing process in which low melting point filler metal
used to join base metals, which do not melt the base metal. Metal-joining
techniques such soldering (Exp. Plate Heat Exchangers).
Based on Material:
Ferrous i.e. Carbon Steel, Low Alloy Steel, Stainless steel, Duplex SS
Non Ferrous i.e. Copper Alloys (Monel), Nickel alloys (Hastalloy).
Non Metallic i.e. Fiber Reinforced Plastics (FRP)
Based on Usage: Static, Mobile

4. Tall Tower/Column
Vertical vessel with Height (TL
to TL) / Diameter ratio > 5is
considered as Column.
Loading Condition:
Erection:un-corroded, erected
on foundation, without
insulation, platforms, trays
etc. Only welded
attachments & full wind on
column.
Operating: corroded, under
design pressure, including
welded items, trays, insulated
including all attachments shall
be considered.

5. Test: Column (corroded) under
test pressure, filled with water
plus 33% of specified wind load
on un-insulated column
including all attachments shall
be considered.
(iv) Earth quake And Wind
Shall Be Considered Not Acting
Concurrently.
Deflection of Column
Maximum allowable deflection
at top of column shall be equal
to column height / 200.
Dynamic Analysis of
Columncarried out for
transverse wind induced
vibrations.

6. Reactor:Process fluid
undergoes a chemical
reaction.
Reaction rate is
increased by catalyst.
Packed bed reactors are
most commonly
used.Cylindrical vessel
packed with catalyst.
Support grid and screen
is placed at the bottom to
support the catalyst.

7. SPHERICAL VESSEL:
The spherical shape has
the Highest
Volume/Surface area
and less metal is needed
to make the vessel. So,
it’s a most economical
shape.
The spherical shape is the
strongest shapeagainst
internal/external pressure
Mostly used for high
pressure storage
applications.

8. t = P*ri/Sh where, P = ρgh
t = P*ri/Sh = ρ*9.806*(h-0.3)*D/2*Sh
For Atm Pressure only. For Low pr.refer
Appendix F.
Storage Tank:
As per The American
Petroleum Institute(API
650), Design
Pressure ATM to 3.5
kN/m2.
Shell thickness
calculation shall be carried
out by1-foot method for
tank diameters less than
and equal to 60m (200
feet).

9. Vessel with Jacket:
Conventional Jackets:
Best forsmall volume
vessels (up to 300
gallons),Steam/Gas
heating and high-
internal pressure
applications where internal
pressure is double than
jacket pressure.
If ratio less than two
external jacket pressure
governs which may cause
increase in inner vessel
thickness.

10. Half pipe: Half pipe are
recommended for high-
Pressure (up to 750 psig)
&High temperature. It is
mainly used forliquid
heat-transfer application.
Dimple jacketed: Most
Economical due to pitched
ligament joints. Used up to
300 psig.

11. Component of Pressure Vessel
Shell, Head, Nozzles, Flanges, Supports, Platform/Ladder.

13. Hoop or circumferential Stress:
Pr. Force = pr. x Projected Area
= Pr*d*L
Material Resisting Force = Sh*2*L*t
(At equilibrium both equal)
Pr*d*L = Sh*2*L*t
Sh = Pr . d / 2*t or t = Pr.*R/Sh
Longitudinal Stress:Pr. Force = pr. x
Projected Area = Pr* pi*d2 /4
Material Resisting Force
=SL*pi*d*t(At equilibrium both
Equal)pr* pi*d2/4
= SL*pi*d*tSl=Pr*d/4*t or t
=Pr*R/2*SL

14. Codes & Standards:
Code/STD Scope
Pressure Temp. Special Condition
API 650
Internal pressures not
exceeding 2.5 psig
0 to 93 deg C
entire bottom is uniformly
supported
API 620
Internal pressure exceed 2.5
psig but
not Exceeding 15 psig
maximum design
temperature Between -
45°C to 121°C
Above ground storage
tanks including flat-bottom
tank that have a single
vertical axis of revolution.
ASME
SEC. VIII -
DIV. 1
Internal pressures Between
1.01325 Barg (15 psig) to 206
Barg (3000 psig)
Flash point of content at
atmospheric pressure is
85 deg C or higher.
Not Applicable for inside
diameter, width, height, or
cross section diagonal below
6"
ASME SEC. VIII Div. 1 =<3000 psigDiv. 2 =< 10000 psigDiv. 3. ASME
SEC. IIA &IIBMaterial SpecificationsFerrous (SA-516 70, SA-105) Non Ferrous
(Monel SB-127, SB-165), Manufacturing requirements, Chemical Properties.
ASME SEC. IIC Specifications for Welding Rods, Electrodes, and Filler Metals
ASME SEC. IID Material Properties, Mechanical/Physical Properties.
ASME SEC.V NDT requirementsRT, MP, DP, UT etc.
ASME SEC. IXQualification Standard for Welding etc.
Welding Procedure Specification (WPS), Procedure Qualification Record (PQR)
Welding Performance Qualification (WPQ)
TEMA(Tubular Exchanger Manufacturer Association). Shell & Tube HX.
Supporting StandardsASME B16.5, B16.20, B16.9, B16.11, Wind & Seismic

15. ASME Code, Section VIII, Division 1 use the maximum principal stress
theory as a basis for design. This theory simply considers that yielding
occurs when the largest principal stress equals the yield strength.
Minimum Thickness of Pressure Components is 1.5mmexclusive of
any corrosion allowance.
Design Formulas:
Shell design thickness,Tr = PRi/ (SE-0.6P) +C.A
Hemi. Head design thickness,Tr = PRi/ (2SE-0.2P) +C.A
Elliptical Head design thickness,Tr = PRi/ (SE-0.1P) +C.A
Thin Cylindrical Shell:
Material of Shell SA-515-60,
Internal diameter Di= 96 inch
Internal design pressure P= 100 psig(Since P < 0.385SE =6545 psi)
Internal design Temperature = 450 F°.
Allowable Stress at design Temp.S= 15,000 psi (ASME Sec. II, Table 1A)
Corrosion allowance C.A= 0.125 in.
Joint efficiency is E = 0.85.
Corroded Radius Ri=Di/2+C.A = 96/2+0.125 = 48.125 inch.

16. Shell design thickness,
Tr = PRi/ (SE-0.6P) +C.A
= 100 x 48.125 + 0.125 =0.504 inch
(15,000 x 0.85 – 0.6 x 100)
Hemispherical Head design thickness,
Tr = PRi/ (2SE-0.2P) +C.A
= 100 x 48.125 + 0.125 =0.314 inch
(2 x15,000 x 0.85 – 0.2 x 100)
Elliptical Head design thickness,
Tr = PRi/ (SE-0.1P) +C.A
= 100 x 48.125 + 0.125 =0.503 inch
(15,000 x 0.85 – 0.1 x 100)
Hydrostatic Test Pressure:
Pressure per UG99b = 1.3 * M.A.W.P. * Sa/S kgf/cm² gPressure
per UG99c = 1.3 * M.A.P. - Head(Hyd) kgf/cm² g
Pressure per UG100 = 1.1 * M.A.W.P. * Sa/S kgf/cm² g

17. Weld Category:

19. Nozzle ReinforcementIt works on the basis of replacement of opening
c/s with equal c/s area in shell/Nozzle/fillet welds.

20. Local loads on vessel due to piping

21. WRC 107/WRC-537(Accurate) WRC 297
Applicable for cylindrical & spherical shells.
Analyzes cylindrical or rectangular
attachments which can be rigid or hollow.
Applicable cylindrical shell Intersectingeach
other.
Analyzes cylindrical hollow attachments
Boundary conditions
d/D<0.33
Dm/T>50
Boundary conditions
d/D<=0.5, d/t>=20 up to d/t<=100
D/T>=20 up to D/T<=2500, d/T>=5
Nozzle must be isolated
Considers no opening in shell. Considers circular opening in shell.
Calculates only the vessel stresses. Calculates Vessel stresses &nozzle stresses.
Methods of reducing local stresses in Vessel.
1. Increase the size of the attachment. (forLug/Leg Support, Lifting Lug etc.)
2. Increase the number of attachments. (forLug/Leg Support,Lifting Lug etc.)
3. Change the shape of the attachment to distribute stresses. (To cover higher surface area)
4. Add reinforcing pads.(for Nozzles Lug/Leg Support,Lifting Lug etc.)
5. Increase shell thickness locally or use thicker shell course.(for Nozzles)

22. Material of ConstructionStress Strain Diagram:

25. Impact & Hardness test methods:

26.  Vessel in Hydrogen & H2S service: hydrogen atoms in a solid
metal dissolved in the metal grid and accumulate between Iron atoms
results in the reduction of its ductility by decreasing the energy of
cohesion and consequently in the increase of its probability of brittle
fracture.

27. Material Requirements:

28. Heat Exchanger is a device for transferring heat from one medium to another in a direct or indirect contact.

30. Fixed type Shell & Tube Heat Exchanger
AEM
BEM
Construction:Non-
removable Bundle,
Fixed Tubesheets
Advantages: Less costly than
removable bundle heat exchangers.
Provides maximum heat transfer
surface per given shell and tube size.
Provides multi-tube-pass
arrangements.
Limitations: Shell side can be cleaned only
by chemical means.
Higher Differential
thermal expansion between shell and
tubesrequires Bellow.

31. U-Tube type Shell & Tube Heat Exchanger
AEU
BEU
CEU
Construction:Removable
Bundle,
U-Tube
Advantages: Less costly than floating
head designs.
Provides multi-tube pass
arrangements.
Allows for differential thermal
expansion between the shell and
tubes &individual tubes.
High surface per given shell and tube
size.
Capable of withstanding thermal
Limitations: Tube side cleaned by
chemical means only.
Individual tube replacement is not
practical.
Cannot be made single pass on tube
side.
Tube wall at U-Bend is thinner than at
straight portion of the tube.
Draining tube side difficult in vertical
(head up) position.

32. shock.
Floating Head type Shell & Tube Heat Exchanger
AES
BES
CES
Construction:Removable
Bundle,
Floating Head Cover
Advantages:
Allows for differential thermal
expansion between the shell & tubes.
Limitations:
Higher maintenance cost.
More costly than fixed tube sheet or U-

33. Excellent Inflammable and/or toxic
service
tube heat exchanger designs.

34. ASME Sec. VIII Div.1 Appendix 13-Air Cooled Heat Exchanger:
Air Cooled Heat Exchangers
Advantages Limitations
Attractive option for locations where cooling water
is not available or expensive to treat.
High initial purchase cost due to relatively
large area occupied.

35. Low maintenance and operating costs (typically
30-50% less than cooling water)
Higher process outlet temperature (10-20 oF
above the ambient dry bulb temperature)