Design Analysis of PV

DESIGN AND ANALYSIS OF PRESSURE VESSEL

BY

JIMIT VYAS AND MAHAVIR SOLANKI

GUIDED BY : MR BHAVESH PATEL

U V PATEL COLLEGE OF ENGINEERING

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ACKNOWLEDGEMENT Certainly, help and encouragement from others are always appreciated, but in different times, such magnanimity is valued even more. This said, this Dissertation would never have been completed without the generous help and support that I received from numerous people along the way.

I wish to express my deepest thanks and gratitude to my elite guide Mr Bhavesh P Patel, Mechanical Engineering Dept., U.V. Patel College of Engg., Mehsana, for his invaluable guidance and advice, without that the Dissertation would not have appear in present shape. He also motivated me at every moment during entire dissertation.

I also hearty thankful and express deep sense of gratitude to Mr. Bhavesh Prajapati, senior manager at GMM Pflauder, for giving opportunity to undertake a dissertation in the industry and furnishing the details and help. Special thanks to Mr. Ankit Prajapati, Design Engineer, at GMM Pflauder, for his keen interest and guidance in carrying out the work. I wish to thank the principal Dr. J. L. Juneja and all the staff members of Mechatronics & Mechanical Dept., U. V. Patel College of Engg., especially to , Prof. J. M. Prajapati, Prof. J. P. Patel, Prof. V. B. Patel, for their co-operation, guidance and support during the work.

Jimit Vyas & Mahavir Solanki


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ASTRACT The significance of the title of the project comes to front with designing structure of the pressure vessel for static loading and its assessment by Ansys , is basically a project concerned with design of different pressure vessel elements such as shell, Dish end ,operating manhole ,support leg based on standards and codes ; and evolution of shell and dish end analysed by means of ansys .The key feature included in the project is to check the behaviour of pressure vessel in case of fluctuating load .The [procedural step includes various aspects such as selecting the material based on ASME codes ,and then designing on the standards procedures with referring standard manuals based on ASME .Further we have included the different manufacturing methods practice by the industries and different aspects of it . And step by step approaches to the NTD method practice by the industries followed with standards and also included within the report work. This will be making

a

clear

picture

f

this

method

among

the

reader

.

conclusively, this modus operandi of design based on technical standard and codes ., can be employed on practical design of pressure vessel as per required by the industry or the problem statement given associated to the field of pressure vessel.


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INTRODUTION: The pressure vessels (i.e. cylinder or tanks) are used to store fluids under pressure. The fluid being stored may undergo a change of state inside the pressure vessel as in case of steam boilers or it may combine with other reagents as in a chemical plant. The pressure vessels are designed with great care because rupture of pressure vessels means an explosion which may cause loss of life and property. The material of pressure vessels may be brittle such that cast iron or ductile such as mild steel. Cylindrical or spherical pressure vessels (e.g., hydraulic cylinders, gun barrels, pipes, boilers and tanks) are commonly used in industry to carry both liquids and gases under pressure. When the pressure vessel is exposed to this pressure, the material comprising the vessel is subjected to pressure loading, and hence stresses, from all directions. The normal stresses resulting from this pressure are functions of the radius of the element under consideration, the shape of the pressure vessel (i.e., open ended cylinder, closed end cylinder, or sphere) as well as the applied pressure. Two types of analysis are commonly applied to pressure vessels. The most common method is based on a simple mechanics approach and is applicable to “thin wall” pressure vessels which by definition have a ratio of inner radius, r, to wall thickness, t, of r/t≥10. The second method is based on elasticity solution and is always applicable regardless of the r/t ratio and can be referred to as the solution for “thick wall” pressure vessels. Both types of analysis are discussed here, although for most engineering applications, the thin wall pressure vessel can be used.


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Classification of Pressure Vessels

Unfired Cylindrical Pressure Vessels (Classification Based on IS 2825-1969)

a) Class 1 : Vessels that are to contain lethal or toxic substances. Vessels designed for the operation below -20 C and Vessels intended for any other operation not stipulated in the code. b) Class 2: vessels which do not fall in the scope of clas1 and class 3 are to be termed as class2 vessels. The maximum thickness of shell is limited to 38 mm. c) class 3: there are vessels for relatively light duties having plate thickness not in excess of 16 mm, and they are built for working pressures at temperatures not exceeding 250 c and unfired . class3 vessels are not recommended for services at temperatutre below 0c.


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Categories Of Welded Joints The term categories specifies the location of the joint in a vessels, but not the type of joint. These categories are intended for specifying the special requirements regarding the joint type and degree of inspection. IS-2825 specifies 4 categories of welds. (Refer fig.)

a) category A: longitudinal welded joints within the main sheet, communicating chambers ,nozzles and any welded joints within a formed or flat head. b) Category B: circumferential welded joints with in the main shell, communicating chambers, nozzles and transitions in diameter including joints between the transtations and a cylinder at either the large of small end, circumferential welded joints connecting from heads to main shells to nozzles and to communicating chambers. c) Category c: welded joints connecting flanges, tubes sheets and flat heads to main shells , to formed heads , to nozzles or to communicating chambers and any welded joints connecting one side plate to another side plate of a flat sided vessel. d) Category d: welded joints connecting communicating chambers or nozzles to main sheels ,to heads and to flat sided vessels and those joints connecting nozzles to communicating chambers.


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STRESS Types of Stresses Tensile Compressive

Shear

Bending

Bearing

Axial

Discontinuity

Membrane

Tensile

Principal

Thermal

Tangential

Load induced

Strain induced

Circumferential

Longitudinal

Radial

Normal

Classes of stress Primary Stress General: Primary general membrane stress Pm Primary general bending stress Pb Primary local stress, PL Secondary stress: Secondary membrane stress. Qm Secondary bending stress Qb Peak stress. F

Definition and Examples PRIMARY GENERAL STRESS: These stress act over a full cross section of the vessel. Primary stress are generally due to internal or external pressure or produced by sustained external forces and moments. Primary general stress are divided into membrane and U V PATEL COLLEGE OF ENGINEERING

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bending stresses. Calculated value of a primary bending stress may be allowed to go higher than that of a primary membrane stress. Primary general membrane stress, Pm Circumferential and longitudinal stress due to pressure. Compressive and tensile axial stresses due to wind. Longitudinal stress due to the bending of the horizontal vessel over the saddles. Membrane stress in the centre of the flat head. Membrane stress in the nozzle wall within the area of reinforcement due to pressure or external loads. Axial compression due to weight. Primary general bending stress, Pb Bending stress in the centre of a flat head or crown of a dished head. Bending stress in a shallow conical head. Bending stress in the ligaments of closely spaced openings.

LOCAL PRIMARY MEMBRANE STESS, PL Pm+ membrane stress at local discontinuities: Head-shell juncture Cone-cylinder juncture Nozzle-shell juncture Shell-flange juncture Head-skirt juncture Shell-stiffening ring juncture Pm+ membrane stresses from local sustained loads: Support legs Nozzle loads Beam supports Major attachments

SECONDARY STRESS Secondary membrane stress Qm Axial stress at the juncture of a flange and the hub of the flange Thermal stresses. U V PATEL COLLEGE OF ENGINEERING

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Membrane stress in the knuckle area of the head. Membrane stress due to local relenting loads. Secondary bending stress, Qb Bending stress at the gross structural discontinuity: nozzle, lugs, etc., (relenting loadings only). The nonuniform portion of the stress distribution in a thick-walled vessels due to internal pressure. The stress variation of the radial stress due to internal pressure in thick-walled vessels. Discontinuity stresses at stiffening or support ring. Peak Stress F Stress at the corner of discontinuity. Thermal stress in a wall caused by a sudden change in the surface temperature. Thermal stresses in cladding or weld overlay. Stress due to notch effect. (stress concentration).

LOADINGS Loadings or forces are the “causes” of stress in pressure vessels. Loadings may be applied over a large portion (general area) of the vessel or over a local area of the vessel. General and local loads can produce membrane and bending stresses. These stresses are additive and define the overall state of stress in the vessel or component. The stresses applied more or less continuously and uniformly across an entire section of the vessel are primary stresses. The stresses due to pressure and wind are primary membrane stresses. O the other hand, the stresses from the inward radial load could be either a primary local stress or secondary stress. It is primary local stress if it is produced from an unrelenting load or a secondary stress if produced by a relenting load.


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If it is a primary stress, the stress will be redistributed; if it is a secondary stress, the load will relax once slight deformation occurs. Basically each combination of stresses ( stress categories will have different allowables, i.e., Primary stress: Pm < SE Primary membrane local (PL): PL=Pm+ PL <1.5 SE PL=Pm+Qm< 1.5SE Primary membrane + secondary (Q): Pm+Q< 3SE Loading can be outlined as follows: Categories of loadings General loads—Applied more or less continuously across a vessel section. Pressure loads—Internal or external pressure (design, operating, hydrotest, and hydrostatic head of liquid). Moment loads—Due to wind, seismic, erection, transportation. Compressive/tensile

loads—Due

to

dead

weight,

installed

equipment, ladders, platforms, piping and vessel contents. Thermal loads—Hot box design of skirt-head attachment. Local loads—Due to reactions from supports, internal, attached Piping, attached equipment, i.e., platforms, mixers, etc. a. Radial load—Inward or Outward. b. Shear load—Longitudinal or circumferential. c. Torsional load. d. Tangential load. e. Moment load—Longitudinal or circumferential. f. Thermal load. U V PATEL COLLEGE OF ENGINEERING

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Types of Loadings 1) Steady loads—Long-term duration, continuous. a. Internal/external pressure. b. Dead weight. c. Vessel contents. d. Loading due to attached piping and equipment. e. Loadings to and from vessel supports. f. Thermal loads. g. Wind Loads

Types of Loadings 1) Non-steady loads- Short-term duration, Variable. Shop and field hydro-test Earthquake Erection Transportation Upset, emergency Thermal Loads Startup, shut down

FAILURE IN PRESSURE VESSELS Categories of Failures: Material--Improper Selection of materials; defects in material. Design—Incorrect design data; inaccurate or incorrect design methods; inadequate shop testing. Fabrication – Poor quality control; improper or insufficient fabrication procedures including welding; heat treatment or forming methods. U V PATEL COLLEGE OF ENGINEERING

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Service—Change of service condition by the user; inexperienced operations or maintenance personnel; upset conditions. Some types of services which requires special attention both for selection of materials, design details, and fabrication methods are as follows: Lethal Fatigue (cyclic) Brittle (low temperature) High Temperature High shock or vibration Vessel contents Hydrogen Ammonia Compressed air Caustic Chlorides

TYPES OF FAILURES Elastic deformation—Elastic instability or elastic buckling, vessel geometry, and stiffness as well as properties of materials are protecting against buckling. Brittle fracture—Can occur at low or intermediate temperature. Brittle fractures have occurred in vessels made of low carbon steel in the 40-50 F range during hydrotest where minor flaws exist. Excessive plastic deformation—The primary and secondary stress limits as outlined in ASME Section VIII, Division 2, are intended to prevent excessive plastic deformation and incremental collapse. Stress rupture—Creep deformation as a result of fatigue or cyclic loading, i.e., progressive fracture. Creep is a time-dependent phenomenon, whereas fatigue is a cyclic-dependent phenomenon

o TYPES OF FAILURES o

Plastic instability—Incremental collapse; incremental collapse is cyclic strain accumulation or cumulative cyclic deformation. Cumulative damage leads to instability of vessel by plastic deformation.


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o

High Strain—Low cyclic fatigue is strain-governed and occurs mainly in lowerstrength/high-ductile materials.

o

Stress corrosion—It is well know that chlorides cause stress corrosion cracking in stainless steels; likewise caustic service can cause stress corrosion cracking in carbon steel. Materials selection is critical in these services.

o

Corrosion

fatigue—Occurs

when

corrosive

and

fatigue

effects

occur

simultaneously. Corrosion can reduce fatigue life by pitting the surface and propagating cracks. Material selection and fatigue properties are the major considerations.

SPECIAL PROBLEMS Thick Walled Pressure Vessels

Mono-bloc- Solid vessel wall. Multilayer—Begins with a core about ½ in. thick and successive layers are applied. Each layer is vented (except the core) and welded individually with no overlapping welds. Multi-wall—Begins with a core about ½ in. to 2 in. thick. Outer layers about the same thickness are successive “ shrunk fit” over the core. This creates compressive stress in the core, which is relaxed during pressurization. The process of compressing layers is called auto-frettage from the French word meaning “selfhooping.” Multilayer auto-frettage—Begins with a core about ½ in. thick. Bands or forged rings are slipped outside and then the core is expanded hydraulically. The core is stressed into plastic range but below ultimate strength. The outer

rings are

maintained at a margin below yield strength. The elastic deformation residual in U V PATEL COLLEGE OF ENGINEERING

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the outer bands induces compressive stress in the core, which is relaxed during pressurization. Wire wrapped vessels: Begin with inner core of thickness less than required for pressure. Core is wrapped with steel cables in tension until the desired autofrettage is achieved. Coil wrapped vessels: Begin with a core that is subsequently wrapped or coiled with a thin steel sheet until the desired thickness is obtained. Only two longitudinal welds are used, one attaching the sheet to the core and the final closures weld. Vessels 5 to 6 ft in diameter for pressure up to 5000psi have been made in this manner.

THERMAL STRESS Whenever the expansion or contraction that would occur normally as a result of heating or cooling an object is prevented, thermal stresses are developed. The stress is always caused by some form of mechanical restrain. Thermal stresses are “secondary stresses” because they are self-limiting. Thermal stresses will not cause failure by rupture. They can however, cause failure due to excessive deformations.

DISCONTINUITY STRESSES Vessel sections of different thickness, material, diameter and change in directions would all have different displacements if allowed to expand freely. However, since they are connected in a continuous structure, they must deflect and rotate together. The stresses in the respective parts at or near the juncture are called discontinuity stresses. Discontinuity stresses are “ secondary stresses” and are self-limiting. Discontinuity stresses do become an important factor in fatigue design where cyclic loading is a consideration.

FATIGUE ANALYSIS When a vessel is subject to repeated loading that could cause failure by the development of a progressive fracture, the vessel is in cyclic service. Fatigue analysis can also be a result of thermal vibrations as well as other loadings.


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In fatigue service the localized stresses at abrupt changes in section, such as at a head junction or nozzle opening, misalignment, defects in construction, and thermal gradients are the significant stresses.

NOZZLE REINFORCEMENT

Fig : nozzle reinforcement Limits. a. No reinforcement other than that inherent in the construction is required for nozzles. 3-in. pipe size and smaller in vessel walls 3/8 in. and less. 2-in. pipe size and smaller in vessel walls greater than 3/8 in. b.

Normal reinforcement methods apply to


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Vessels 60-in. diameter and less-1/2 the vessel diameter but not to exceed 20 in. Vessels greater than 60-in. diameter-1/3 the vessel diameter but not to exceed 40.in a. 1b, reinforcement shall be in accordance with para. 1-7 of ASME Code. 2. Strength It is advisable but not mandatory for reinforcing pad material to be the same as the vessel material. a. If a higher strength material is used, either in the pad or in the nozzle neck, no additional credit may be taken for the higher strength. 3. Thickness It is recommended that pad be not less then 75% nor more than 150% of the part to which they are attached.

4. Width While no minimum is stated, it is recommended that re-pads be atleast 2in wide. 5. Forming: Reinforcing pads should be formed as closely to the contour of the vessel as possible. While normally put on the outside of the vessel, re-pads can also be put inside providing they do not interfere with the vessel’s operation. 8. Openings in flat heads: Reinforcements for the openings in the flats heads and blind flanges shall be as follows a. Openings < ½ head diameter- area to be replaced equals 0.5(tr), or thickness of head or flange may be increased by: Doubling C value Using C=0.75 Increasing head thickness by 1.414 b. Openings>1/2 head diameter –shall be designed as a bolted flange connection. 9. Openings in torispherical heads. U V PATEL COLLEGE OF ENGINEERING

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When a nozzle openings and all its reinforcement fall within the dished portion, the required thickness of head for reinforcement purpose shall be computed using M=1 10. Openings in elliptical heads When a nozzle openings and all its reinforcement fall within 0.8 D of an elliptical head, the required thickness of the head for reinforcement purpose shall be equal to the thickness required for a seamless sphere of radius K(D). 11. General Reinforcement should be calculated in the corroded condition assuming maximum tolerance (minimum t) 12. Openings through seams. a.

Openings that have been reinforcement may located in a welded joint. ASME code, division 1, does not allow a welded joint to have two different weld joint efficiencies

13. Re-pads over seams If at all possible, pads should not cover weld seams. When unavoidable, the seam should be ground flush before attaching the pad. 14. Openings near seams Small nozzles ( for which the code does not require, the reinforcement to be checked) shall not be located closer than ½ in. to the edge of a main seam. 15. External pressures. Reinforcement required for openings subject to external pressure only or when longitudinal compression governs shall only be 50 % of that required for internal pressure and tr, is thickness required for external pressure 16. Ligaments When there is a series of closely spaced openings in a vessel shell and it is impractical to reinforce each opening, the construction

is acceptable, provided the

efficiency of the ligaments between the holes is acceptable. 17. Multiple openings:


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a.

For two openings closer than 2 times the average diameters and where limits of reinforcement overlap, the area between the openings shall meet the following

1. Must have a combined area equal to the sum of the two areas 2. No portion of the cross-section shall apply to more than one openings. 3. Any overlap area shall be proportional between the two openings by the ratio of the diameters. b. When more than two openings are to be provided with combined reinforcement: 17 b.

When more than two openings are to be provided with combined reinforcement:

1.

The minimum distance between the two centers is 1 1/3 the average diameters.

2.

The area of reinforcement between the two nozzle shall be atleast 50% of the area

required for the two openings. c.

Multiple openings may be reinforced s an opening equal in diameter to that of a

circle circumscribing the multiple openings. 18.

Plane of reinforcement. A correction factor f may be used for “ integrally reinforced” nozzle to compensate

for differences in stress from longitudinal to circumferential axis of the vessel. Value of f vary from 1.0 for the longitudinal axis to 0.5 for circumferential.


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CHAPTER 2

ENGINEERING

GUIDELINES

FOR

DESIGN OF PRESSURE VESSELS


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Engineering Design Guidelines For Pressure Vessels

1.0

SCOPE This specification covers the design basis for following equipment: - Vessels - Columns - Reactors - Spheres - Storage Tanks - Steel silos, Bins. Hoppers - Steel Flare Stacks

2.0

CODES AND STANDARDS The following codes and standards shall be followed unless otherwise specified: ASME SEC. VIII DIV.1 /

For Pressure vessels

IS: 2825 ASME SEC. VIII DIV.2

For Pressure vessels (Selectively for high pressure / high thickness / critical service)

ASME SEC. VIII DIV.2

For Storage Spheres

ASME SEC. VIII DIV.3

For Pressure vessels (Selectively for high pressure)

API 650 / IS: 803

For Storage Tanks.

API 620

For Low Pressure Storage Tanks,


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API 620 / BS 7777

Cryogenic Storage Tanks (Double Wall)

ASME SEC. VIIIDIV.1

For workmanship of Vessels not categorized under any other code.

ISO R831/ IBR

For Steam producing, steam storage catch water vessels, condensate flash drums and similar vessels

IS: 9178 / DIN 1055

For Silos Hoppers and Bins

BS: 4994 / ASME SEC X

FRP vessels / tanks.`

ASME: B 96.1

Welded Aluminium Alloy Storage Tanks.

ASME SEC.II

For material specification

ASTM / IS

For material specification (Tanks)

IS: 875 / SITE DATA

For wind load consideration

IS: 1893 / SITE DATA

For seismic design consideration

ASME SEC. IX

For welding.

WRC BULLETIN# 107, 297 / PD 5500

3.0

For Local load / stress analysis

DESIGN CRITERIA

Equipment shall be designed in compliance with the latest design code requirements, and applicable standards/ Specifications. U V PATEL COLLEGE OF ENGINEERING

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4.0

MINIMUM SHELL/HEAD THICKNESS

Minimum thickness shall be as given below a) For carbon and low alloy steel vessels- 6mm (Including corrosion allowance not exceeding 3.0mm), but not less than that calculated as per following: FOR DIAMETERS LESS THAN 2400mm

Wall thickness = Dia/1000 +1.5 + Corrosion Allowance FOR DIAMETERS 2400mm AND ABOVE Wall thickness = Dia/1000 +2.5 + Corrosion Allowance All dimension are in mm. b) For stainless steel vessel and high alloy vessels -3 mm, but not less than that calculated as per following for diameter more than 1500mm. Wall thickness (mm) = Dia/1000 + 2.5 Corrosion Allowance, if any shall be added to minimum thickness. c) Tangent to Tangent height (H) to Diameter (D) ratio (H/D) greater than 5 shall be considered as column and designed accordingly. d) For carbon and low alloy steel columns / towers -8mm (including corrosion allowance not exceeding 3.0mm. e) For stainless steel and high alloy columns / towers -5mm. Corrosion allowance, if any, shall be added to minimum thickness.


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5.0

GENERAL CONSIDERATIONS

5.1

Vessel sizing All Columns

Based on inside diameter

All Clad/Lined Vessels


Vessels (Thickness>50mm) Based on inside diameter

5.2

All Other Vessels

Based on outside diameter

Tanks & Spheres


Vessel End Closures :

- Unless otherwise specified Deep Torispherical Dished End or 2:1 Ellipsoidal Dished End as per IS - 4049 shall be used for pressure vessels. Seamless dished end shall be used for specific services whenever specified by process licensor. - Hemispherical Ends shall be considered when the thickness of shell exceeds 70mm. - Flat Covers may be used for atmospheric vessels - Pipe Caps may be used for vessels diameter < 600mm having no internals. - Flanged Covers shall be used for Vessels /Columns of Diameter < 900mm having internals. - All columns below 900mm shall be provided with intermediate body flanges. Numbers of Intermediate flanges shall be decided based on column height and type of internals

5.3

Pressure

Pressure for each vessel shall be specified in the following manner:

5.3.1 Operating Pressure Maximum pressure likely to occur any time during the lifetime of the vessel

5.3.2 Design Pressure a) When operating pressure is up to 70 Kg./cm2 g , Design pressure shall be equal to operating pressure plus 10% ( minimum 1Kg./cm2 g ). U V PATEL COLLEGE OF ENGINEERING

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b) When operating pressure is over 70 Kg./cm2 g , Design pressure shall be equal to operating pressure plus 5% ( minimum 7 Kg./cm2g). c) Design pressure calculated above shall be at the top of vertical vessel or at the highest point of horizontal vessel. d) The design pressure at any lower point is to be determined by adding the maximum operating liquid head and any pressure gradient within the vessel. e) Vessels operating under vacuum / partial vacuum shall be designed for an external pressure of 1.055 Kg./cm2 g. f) Vessels shall be designed for steam out conditions if specified on process data sheet.

5.3.3 Test Pressure a) Pressure Vessels shall be hydrostatically tested in the fabricators shop to 1.5 /1.3/ 1.25 (depending on design code) times the design pressure corrected for temperature. b) In addition, all vertical vessels / columns shall be designed so as to permit site testing of the vessel at a pressure of 1.5/ 1.3 / 1.25 (depending on design code) times the design pressure measured at the top with the vessel in the vertical position and completely filled with water. The design shall be based on fully corroded condition. c) Vessels open to atmosphere shall be tested by filling with water to the top. d)

1. Pressure Chambers of combination units that have been designed to operate

independently shall be hydrostatically tested to code test pressure as separate vessels i.e. each chamber shall be tested without pressure in the adjacent chamber. 2. When pressure chambers of combination units have their common elements designed for maximum differential pressure the common elements shall be subjected to 1.5/ 1.3 times the differential pressure. 3. Coils shall be tested separately to code test pressure. e) Unless otherwise specified in applicable design code allowable stress during hydro test in tension shall not exceed 90% of yield point. f) Storage tanks shall be tested as per applicable code and specifications.


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5.4

Temperature

Temperature for each vessel shall be specified in the following manner:

5.4.1 Operating Temperature Maximum / minimum temperature likely to occur any during the lifetime of vessel.

5.4.2 Design temperature a) For vessels operating at 0C and over: Design temperature shall be equal to maximum operating temperature plus 15 0C. b) For Vessels operating below 0C: Design temperature shall be equal to lowest operating temperature. c) Minimum Design Metal Temperature (MDMT) shall be lower of minimum atmospheric temperature and minimum operating temperature.

5.5

Corrosion allowance :

Unless otherwise specified by Process Licensor, minimum corrosion allowance shall be considered as follows : - Carbon Steel, low alloy steel column, Vessels, Spheres : 1.5 mm - Clad / Lined vessel: Nil - Storage Tank, shell and bottom : 1.5 mm - Storage tank, Fixed roof / Floating Roof : Nil For alloy lined or clad vessels, no corrosion allowance is required on the base metal. The cladding or lining material (in no case less than 1.5 mm thickness) shall be considered for corrosion allowance. Cladding or lining thickness shall not be included in strength calculations. Corrosion allowance for flange faces of Girth / Body flanges shall be considered equal to that specified for vessel.


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5.6

Wind Consideration

Wind load shall be calculated on the basis of IS : 875 / site data. a) Drag coefficient for cylindrical vessels shall be 0.7 minimum. b) Drag coefficient for spherical vessel shall be 0.6 minimum.

5.7

Earthquake Consideration :

Earthquake load shall be calculated in accordance with IS : 1893 / site data if specially developed and available

5.8

Capacity

5.8.1 Tank Capacity shall be specified as Nominal capacity and stored capacity Nominal capacity for fixed roof tanks be volume of cylindrical shell. Nominal capacity for floating roof tanks shall be volume of cylindrical shell minus free board volume. Stored capacity shall be 90% of Nominal capacity.

5.8.2 Sphere Stored capacity shall be 85% of nominal capacity.

5.9

Manholes : a) Vessels and columns with diameter between 900 and 1000 mm shall be

provided with 450 NB manhole. Vessels and columns with diameter greater than 1000mm shall be provided with 500 NB manhole. However, if required vessels and columns with diameter 1200mm and above may be provided with 600NB manhole. b) For storage tanks minimum number of manholes (Size 500mm) shall be as follows: Tank Diameter

Shell

Roof

Dia. < 8m

1

1


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> 8m dia. < 36 dia

2

2

Dia. > 36m

4

2

Floating roofs (pontoon or double deck type) shall be provided with manholes to inspect the entire interior of the roofs. Size of manhole shall be 500 mm minimum.

5.10 Floating Roof : 5.10.1 Unless otherwise specified floating roof shall be of following construction. Tank Diameter

Type of Roof

12 M <

Double Deck Type

>12 M < 60M

Pontoon Type

> 60M

Double Deck Type

5.10.2 Floating roof design shall be in fabricators scope having proven track record. Foam seal of proven make shall be provided unless otherwise specified. 5.11

Nozzle size : Unless otherwise specified - Minimum nozzle Size : 40 NB - Minimum Nozzle Size, Column : 50 NB - Safety Valve Nozzle : Based on I.D. - Self Reinforced Nozzle Neck : Based on I.D.

5.11.1 a) All nozzles and man-ways including self-reinforced type shall be 'set in' type and attached to vessel with full penetration welds. b) Self reinforced nozzles up to 80mm NB may be 'set on' type.

5.12 Flanges


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5.12.1 Unless otherwise specified nozzle flanges up to 600NB shall be as per ASME /ANSI B16.5 and above 600 NB shall be as per ASME /ANSI B 16.47 (SERIES 'B') 5.12.2 For nozzles 100 NB and below, only weld neck flange shall be used. Slip on flanges may be used for nozzles above 100NB in Class 150 rating only. All flanges above Class 150 rating shall be weld neck type 5.12.3 Slip on flanges shall not be used in Lethal, Hydrogen, caustic, severe cyclic service and corrosive service (where corrosion allowance is in excess of 3mm).

5.13 Internals : Removable internals shall be bolted type and bolting shall be stainless steel Type 304, unless specified otherwise.

5.14 Spares : Gaskets :

Two sets for each installed gasket.

Fasteners:

10 % (Minimum two in each size) of installed fasteners.

Sight/Light Glass:

4 sets for each installed glass.

5.15 Vent/Drain Connections: Vessel shall be provided with one number each, vent/drain connection as per following : VESSEL VOLUME, m3

VENT SIZE, NB (mm)

DRAIN SIZE, NB

6.0 and smaller

40

40

6.0 to 17.0

40

50

17.0 to 71.0

50

80

71.0 and larger

80

100

(mm)


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5.16 Pipe Davit : Vertical Vessel / Column having safety valve size > 80 NB and or having internals, shall be provided with pipe davit per relevant standard.

6.0

INSULATION THICKNESS :

As indicated on process data sheet by process licensor

7.0

PAINTING

As per Standard Specification, unless otherwise stated.

8.0

MATERIAL SELECTION :

Material of various parts of equipment shall be selected per process data sheet guidelines and proper care shall be taken for the points as given in Annexure- I or as specified. 9.0

SPECIAL CONSIDERATION FOR TALL COLUMN DESIGN

Mechanical design of self supporting Tall Column / Tower shall be carried out for various load combinations as per Annexure-II 10.0

STATUTORY PROVISIONS :

National laws and statutory provisions together with any local byelaws for the state shall be complied with.

Annexure : I 1.

PRESSURE VESSEL STEEL PLATES ARE PURCHASED TO THE

REQUIREMENT OF THE STANDARD ASME SA-20, WHICH REQUIRES TESTING OF INDIVIDUAL PLATES FOR LOW TEMPERATURE SERVICE. CARBON

STEEL

MATERIAL

IS

ORDERED

TO

MEET

THE

IMPACT

REQUIREMENTS OF SUPPLEMENT OF STANDARD ASME SA 20. TYPICAL U V PATEL COLLEGE OF ENGINEERING

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MATERIAL SPECIFICATION IS AS FOLLOWS SA 516 GR.60. NORMALISED TO MEET IMPACT REQUIREMENTS PER SUPPLEMENT SS OF SA 20 AT-50F 2.

ALL PERMANENT ATTACHMENTS WELDED DIRECTLY TO 9 %

NICKEL STEEL SHOULD BE OF THE SAME MATERIAL OR OF AN AUSTENTIC STAINLESS STEEL TYPE WHICH CANNOT BE HARDENED BY HEAT TREATMENT. 3.

CHECK FOR IMPACT TESTING REQUIREMENT AS PER UCS-66 FOR

COINCIDENT TEMPERATURE AND PART THICKNESS. 4.

SELECTION OF STAINLESS STEEL MATERIAL SHALL BE BASED ON

PROCESS RECOMMENDATION/PROCESS LICENSOR. 5.

ATMOSPHERIC/LOW PRESSURE STORAGE TANKS. MATERIAL SHALL

BE SELECTED AS PER API 650 /API 620 AS APPLICABLE. 6.

MATERIALS FOR CAUSTIC SERVICE SOUR SERVICE OR SOUR + HIC

SHALL BE SELECTED BASED ON SPECIFIC RECOMMENDATION OF PROCESS LICENSOR. 7.

MATERIAL FOR PRESSURE VESSELS DESIGNED ACCORDING TO

ASME SECTION VIII DIVISION 2 SHALL BE GIVEN SPECIAL CONSIDERATION AS PER CODE. 8.

ALL PIPES SHALL BE OF SEAMLESS CONSTRUCTION.

9.

NONFERROUS MATERIAL AND SUPER ALLOYS SHALL BE SELECTED

BASED ON SPECIFIC RECOMMENDATION.


Page 30

10.

MATERIAL FOR VESSEL /COLUMN SKIRT SHALL BE THE SAME

MATERIAL AS OF VESSEL/ COLUMN SHELL FOR THE UPPER PART WITH A MINIMUM OF 500MM.

Annexure -II DESIGN PHILOSOPHY OF TALL COLUMNS Mechanical design of self-supporting tall column and its anchorage block shall be carried out considering combination of various loads. 1.0

Loadings

The loadings to be considered in designing a self-supporting tall column/tower shall include: 1.1

Internal and or external design pressure specified on process data sheets.

1.2

Self weight of column inclusive of piping, platforms, ladders, manholes, nozzles, trays, welded and removable attachments, insulation and operating liquid etc. The weight of attachments to be considered shall be as per Table -1 enclosed Other loading as specified in UG-22 of ASME Code Sec, VIII Div.1. wherever applicable.

1.3

Seismic forces and moments shall be computed in accordance with IS 1893 (latest edition). Unless otherwise specified importance factor and damping coefficient shall be considered as 2 and 2% respectively.

1.4

Basic wind pressure and wind velocity (including that due to winds of short duration as in squalls) for the computation of forces / moments and dynamic analysis respectively shall be in accordance with IS 875 (latest edition). Additional wind loading on column due to external attachments like platforms, ladders piping and attached equipment should be given due consideration.

1.5

Loadings resulting in localised and gross stresses due to attachment or mounting of reflux / reboiler / condenser etc.


Page 31

2.0

Loading Condition

Analysis shall be carries out for following conditions : 2.1

Erection Condition: Column (un-corroded) erected on foundation without insulation, platforms, trays etc. but with welded attachments plus full wind on column.

2.2

Operation Condition: Column (in corroded condition) under design pressure, including welded items, trays removable internals, piping, platforms, ladder, reboiler mounted on column, insulating and operating liquid etc. plus full wind on insulated column with all other projections open to wind, or earthquake force.

2.3

Test Condition: Column (in corroded condition) under test pressure filled with water plus 33% of specified wind load on uninsulated column considered.

2.4

EARTHQUAKE AND WIND SHALL BE CONSIDERED NOT ACTING CONCURRENTLY

3.0

Deflection of Column

Maximum allowable deflection at top of column shall be equal to height of the column divided by 200. 3.1

If the deflection of column exceeds the above allowable limit the thickness of skirt shall be increased as first trial up to a maximum value equal to the column thickness and this exercise shall be stopped if the deflection falls within allowable limit.

3.2

If the above step is inadequate, skirt shall be gradually flared to reduce the deflection. Flaring of skirt shall be stopped if the deflection falls within limits or half angle of cone reaches maximum limit of 9 deg.

3.3

If the above two steps prove inadequate in limiting the deflection within allowable limits, the thickness of shell courses shall be increased one starting from bottom course above skirt and proceeding upwards till the deflection falls within allowable limits.


Page 32

4.0

Stress Limits

The stresses due to pressure weight wind / seismic loads shall be combined using maximum principle stress theory for ASME Section VIII Div. I. Thicknesses are accordingly chosen to keep the within limits as per Table-2. 5.0

Skirt Support Base

Base supporting including base plate, anchor chairs compression ring, foundation bolting etc. shall be designed based on overturning moment (greater of seismic or wind). A minimum number of 8 foundation bolts shall be provided. Numbers of foundation bolts shall be in multiple of four. 6.0

Minimum Hydrotest Pressure

Minimum Hydrotest Pressure (in Horizontal position) shall be equal to 1.3 x design pressure x temperature correction factor as specified in ASME Code Section VIII Div. I (Clause UG-99) at top of column. 7.0

Dynamic Analysis

Dynamic analysis of each column shall be carried out for stability under transverse wind induced vibrations as per standard design practice. The recommended magnification amplitude shall be limited to tower diameter divided by five.

TABLE-1 DETAILS AND WEIGHT OF COLUMN ATTACHMENT 1.

Shape factor for shell (for wind force calculation) : 0.7

2.

Weight of trays (with liquid) to be considered. : 120 Kg./m2

3.

Weight of plain Ladder: 15 Kg./m

4.

Weight of caged ladder: 37 Kg./m

5

Equivalent projection to be considered for wind load on caged ladder : 300 mm

6.

Distance of platform below each manhole : Approx. 1000 mm


Page 33

7.

Maximum distance between consecutive platform : 5000 mm

8.

Projection of Platform : 900mm up to 1meter dia. column; 1200 mm for column dia.> 1 meter, from column insulation surface.

9.

Equivalent height of platform (for wind load computation) : 1000 mm

10.

Weight of platforms : 170 Kg./m2.

11.

Platform shall be considered all around

TABLE -2 ALLOWABLE STRESSES FOR COMBINED LOADING VESSEL CONDITION / TEMP./

CONDITIONS

TYPE OF STRESSES

ERECTION

OPERATING NEW OR CORRODED

TEST NEW

CORRODED

AMBIENT

DESIGN

KxSxE

KxSxE

KxB

KxB

CORRODED TEMPERATURE AMBIENT LONGITUDINAL 0.90xY.PxE LONGITUDINAL COMPRESSIVE STRESS

B

Where S = Basic allowable Tensile Stress as per Clause UG 23 (a) of ASME Code Sec. VIII Div.1. B = 'B' value calculated as per Clause UG-23 (b). E = Weld joint efficiency of circumferential weld, depending on extent of radiography. U V PATEL COLLEGE OF ENGINEERING

Page 34

K = Factor for increasing basic allowable value when wind or seismic load is present, 1.2 as per ASME Sec VIII Div 1. Note : Allowable stresses in skirt to shell joint shall be as per following : a) 0.49S, if joint is shear type. b) 0.70S, if joint is compression type.


Page 35

CHAPTER 3

DESIGN

PROCEDURE

AND

CALUCULATION


Page 36

DESIGN THEORY Circumferential or Hoop Stress A tensile stress acting in a direction tangential to the circumference is called Circumferential or Hoop Stress. In other words, it is on longitudinal section(or on the cylinder walls).

Let, p = Intensity of internal pressure, d = Internal diameter of the cylinder shell, l = length of cylinder, t = Thickness of the shell, and σ t1 = hoop stress for the material of the cylinder. Now, We know that total force on a longitudinal section of the shell = Intensity of pressure × projected Area = p × d × l

…..i

and the total resisting force acting on the cylinder walls = σ t1 × 2t × l

….(Q of two section)

…ii From equation (i) and (ii) , we have


Page 37

σ t1 × 2t × l = p × d × l

or

σ t1 =

p×d 2t

or

t =

p×d 2σ t1

…..ii

Longitudinal Stress A tensile stress acting in a direction of the axis is called longitudinal stress. In other words, it is a tensile stress acting on the transverse or circumferential section.

Fig of Longitudinal stress Let

σ t 2 = Longitudinal stress.

In this case, the total force acting on the transverse section = Intensity of pressure × Cross- sectional Area =p×

π (d)² 4

………i

and total resisting force = σ t 2 × πd.t

………ii

From equation (i) and (ii), we have σ t 2 × πd.t = p × σt 2 =

π (d) ² 4

p×d p×d or t = 4σ t 2 4t


Page 38

Design of Shell Due to Internal Pressure As discussed in article on thin vessel are cylindrical pressure vessel is subjected to tangential ( σ t ) and longitudinal ( σ L ) stresses.

σt =

Pi × Di P × Di and σ L = i 2t 4t

where D= mean diameter = Di + t

Rule The design pressure is taken as 5% to 10% more than internal pressure, where as the test pressure is taken as 30% more than internal pressure. Considering the joint efficiency, The thickness of shell can be found by following procedure,

η ×σ =

Pi × ( Di + t ) 2t

η × σ × 2t = Pi × ( Di + t ) t=

Pi × Di 2(η × σ ) − Pi

Design of Elliptical Head: Elliptical heads are suitable for cylinders subjected to pressures over 1.5 MPa. The shallow forming reduces manufacturing cost. It’s thickness can be calculated by the following equation:


Page 39

t=

pi diW 2σ J

where, di = Major axis of ellipse W= Stress intensification factor 1 W = (2 + k 2 ) 6 Where ,

k=

Major Axis Diameter 0.5d i = Major Axis Diameter c

Rule > Generally, k = 2 ( how ever k should not be greater than 2.6) 1 W = (2 + 22 ) 6 =1

t=

Pi ⋅ di ⋅W 2 ⋅σ ⋅ J

Design of Manhole Let, d i = internal dia. Of nozzle d = d i + 2 CA where, CA = corrosion Allowance in mm t = Actual thickness of shell in mm tr = require thickness as per calculation in mm. tn = Actual thickness of nozzle trn = Required thickness as per calculation in mm

t

rn

=

Pi × Di 2 × σ ×η − Pi


Page 40

h1actual = Height of the nozzle above the shell in mm h 2actual = Height of the nozzle below the shell in mm h1 = Height till where the effect of the nozzle persists above the shell in mm h 2 = Height till where the effect of the nozzle persists below the shell in mm To calculate h1 and h 2 consider a term ‘h’ h = 2.5 ( t – CA)

or

h = 2.5 ( tn – CA)

(whichever is smaller)

h1 = h

or

h1actual


h2 = h

or

h 2actual


X = Distance where the effect of the nozzle persists in mm on each side of the centre line X = d. or

X=

di + t + tn -3CA 2

(whichever is maximum)

d op = outer dia. Of Reinforcing Pad in mm

d ip = inner dia. Of Reinforcing Pad in mm

t p = Thickness of Reinforcing Pad in mm


Page 41

Area Calculation Area pertaining to material removed,

A = d × tr

Excess area in the Shell,

A1 = (2X – d ) ( t – tr –CA)

Excess area in the Nozzle,

A2 = 2h1(tn – trn – CA)

Excess area in the nozzle inside the shell A3 = 2 h2 (tn – 2CA) Area Required,

A r = ( d op - d ip ) t p

Area required,

Ar = A – ( A1 + A2 + A3)

When Ar = 0 or negative, no reinforcement is necessary as the vessel thickness self compensates.

Design of Leg: A) Legs support In certain cases, legs can be made detachable to the vessel. These legs can be bolted to plates. The design for leg supports is similar to that for bracket support. If the legs are welded to the shell, then the shear stresses in the weld will be given by:

τ W = w2 Where,

∑W P2 = KP1 H 2 Do mm 2 0.707 × tW × LW × n

τW =

∑W 0.707 × tW × LW × n

tW = Weld Height LW = Weld Length.

These types of supports are suitable only for small vessels as there is a concentrated local stress at the joint.

B) Wind Load Wind load can be estimated as : Pw1 = K P H Do 1 This equation is valid for heights upto 20m. Beyond 20m, the wind pressure is higher and hence for heights above 20m. Pw 2 = KP2 H 2 Do

Generally, P1 lies between 400 N/ mm2 and P2 may be upto 2000 N/ m 2 . Therefore, the bending moment due to wind at the base will be U V PATEL COLLEGE OF ENGINEERING

Page 42

(IF H ≤ 20 m)

Mw =

Pw1h1 2

(IF H> 20m)

Mw =

Pw1h1 h + Pw 2 ( h1 + 2 ) 2 2

Therefore, bending stress will be, σbw =

Mw z

Where Z= section Modulus

The wind load would create tensile stress on the wind side and compressive on the other side.


Page 43

Design Calculation 1) Thickness of cylinder Given data Internal pressure (P) = 0.588 MPa Internal Diameter (Di) = 496mm Corrosion Allowance (CA) = Nil. Joint Efficiency for shell = 1. As per Equation, t=

Pi × Di + CA 2 × σ ×η − Pi

t=

(0.588) × (496) 2 ×137 × 1 − 0.588

(Q CA is NIL)

= 1.066 ∴

t = 1.066mm

2) Elliptical Head 1 W = (2 + k 2 ) 6 where , k=

0.5d i Major Axis Diameter = Major Axis Diameter c

k=2

Rule > Generally, k = 2 ( how ever k should not be greater than 2.6) 1 W = (2 + 22 ) 6 =1 t=

Pi ⋅ di ⋅W 2 ⋅σ ⋅ J

where, U V PATEL COLLEGE OF ENGINEERING

Page 44

di = Major axis of ellipse = 496mm W = Stress intensification factor = 1

t=

Pi ⋅ di ⋅W 2 ⋅σ ⋅ J

t=

0.588 × 496 × 1 2 ×137 × 1

= 1.06 mm ∴ t = 1.06 mm

3) Design Of Manhole INLET NOZZLE (N1)

GIVEN DATA Internal pressure (Pi) = 0.588 N/ mm 2 Internal diameter (Di) = 496 mm Thickness (t) = 6 mm. CA = NIL Joint Efficiency (η ) = 1 Internal diameter of nozzle (di) = 254.51 mm d = di + CA = 254.51 mm. tr = require thickness = 1.066 mm. tn = Actual thickness of nozzle = 9.27 mm. trn = Required thickness as per calculation in mm. 0.588 × 254.51

A = 2 ×137 ×1 − 0.588 t 1

t

rn

=

rn

=

Pi × Di 2 × σ ×η − Pi

0.588 × 254.51 2 × 137 × 1 − 0.588


Page 45

= 0.547 mm.

t

rn

= 0.547 mm.

Area Calculation Area Pertaining to material removed, A = d × tr = 254.51 × 1.066 = 271.3 mm2 Excess area in the shell, A1 = (2X – d ) ( t – tr –CA) Generally, X = d = 254.51 mm. X = di + t + tn -3CA 2 = 254.51 + 6 +9.27 – 0 2 = 142.52 mm. ( Take X whichever maximum) Therefore, A = (2 × 254.51-254.51)(6-1.066-0) = 1255.75 mm2 Excess area in the nozzle, A2 = 2h1(tn – trn – CA) h = 2.5 ( t – CA)

or

h = 2.5 ( tn – CA)

= 2.5 × 6

= 2.5 (9.27)

= 15mm

= 23.175 mm

( Take X whichever smaller)

h1 = h2 = h = 15 mm. Therefore, A2 = 2 × 15 ( 9.27 – 0.547 – 0) = 261.69 mm 2 Excess area in the nozzle inside the shell A3 = 2 h2 (tn – 2CA) = 2 × 15 ( 9.27-0) U V PATEL COLLEGE OF ENGINEERING

Page 46

= 278.1 mm 2 Area required Ar = A – ( A1 + A2 + A3) = -1524.24 As Ar is –ve or zero reinforcement is not necessary.

4) Design of leg Wind load Here , K = Coefficient depending on shape factor = 0.7 P = Wind pressure = 730 N/ mm 2 1 H = Height of the vessel above foundation =2413 mm Do = Outer Diameter Of Vessels Wind load can be estimated as : Pw1 = K P H Do 1 = 0.7×730×2.413×0.508 = 626.38 N (IF H ≤ 20 m)

Mw =

Pw1h1 2

(IF H> 20m)

Mw =

Pw1h1 h + Pw 2 ( h1 + 2 ) 2 2

Here we use , Mw =

Pw1h1 2

= 626.38 × 1206.47 = 755.41 N.m Here we use I- Section, Therefore, Z = section Modulus Z=

bh 3 − b1h13 6h


Page 47

=

4t(5t)3 − 3t(3t)3 6(5t)

= 13.96 t 3 Therefore, Bending Stress will be , σbw =

350× 106 =

Mw z

(as σ bw = 350 N/mm²)

755.41 13.96t 3

t = 5.36 × 10−3 m ∴ L=

123 123 + + 1834 3 3

= 1916 mm


Page 48

SUMMARY

SHELL HEAD MAN HOLE REINFORCEMENT PAD LEG

INTERNAL DIAMETER (Di) LENGTH (L) THICKNESS (t) THICKNESS (t) HEIGHT (h) DIAMETER OF OPENING (di) THICKNESS OF NOZZLE (tn) AS AREA CALCULATED IS ‐ve RF PAD IS NOT REQUIRED THICKNESS OF LEGS


496mm 1734mm 6mm 6mm 173mm 254.51 9.27

5 .36mm

Page 49

DESIGN

APPROCH

2

BY

ASME

CODES


Page 50

DESIGN THEORY PRESSURE VESSEL HEAD DESIGN UNDER INTERNAL PRESSURE THICKNESS OF HEADS/ CLOSURES: ELLIPSOIDAL HEAD: t

= P.Di / (2SE- 0.2P) + CA OTHERS;

t

= P.K.Di/ (2SE-0.2P) + CA

K

=CONSTANT BASED ON THE

MAJOR &

RATIO

OF

MINOR AXIS (D/2H)

“VALUES OF FACTOR K” D/2H 3.0

K

2.6

2.5

2.4

2.2

2.1

2.0

1.83 1.64 1.46 1.37 1.29 1.14 1.07 1.00

D/2H 1.8

K

2.8

1.6

1.5

1.4

1.2

1.0

0.87 0.76 0.71 0.66 0.57 0.50

TORISPHERICAL HEAD: t=

0.885 PL/ (SE-0.1P) + CA

FOR KNUCKLE RADIUS, r = 6% OF CROWN RADIUS (L) t =PLM/ (2S.E- 0.2P) + CA where L=CROWN RADIUS M=CONSTANT BASED ON RATIO OF

CROWN

AND

KNUCLE

RADIUS(L/r)


Page 51

“VALUES OF FACTOR M” L/r 1.0 M

1.00 1.06 1.10 1.15 1.18 1.22

L/r 5.0 M

1.50 2.00 2.50 3.00 3.50

6.0

7.0

8.0

9.0

4.0 1.25

10.0

11.0

1.31 1.36 1.41 1.46 1.50 1.54

1.58

L/r 12.0 13.0 14.0 15.0 16.0 16.67 M

1.62 1.65 1.69 1.72 1.75 1.77

(USE NEAREST VALUE OF L/r; INTERPOLATION UNNECESSARY) NOTE: – MAXIMUM RATIO ALLOWED BY UG-32 (j) WHEN L EQUALS THE OUTSIDE DIAMETER OF THE SKIRT OF THE HEAD. KNUCKLE RADIUS, r SHALL NOT BE LESS THAN 3t.

CONICAL HEAD: t = PDi/ 2 COS α (SE-0.6P) + CA α = half apex angle

HEMISPHERICAL HEAD: t = P.Ri/ (2SE- 0.2P) + CA

FLAT HEADS & COVERS (UG- 34) CIRCULAR COVER/ HEADS t = Di * SQRT(CP/SE) + CA Where C = Factor, dependent on joint geometry of head cover to shell (range 0.1 – 0.33)

OBROUND/ NON-CIRCULAR HEADS (INCLUDING SQUARE/ RECTANGULAR) U V PATEL COLLEGE OF ENGINEERING

Page 52

t = Di * SQRT(Z*CP/SE)

+ CA

where Z = 3.4 - (2.4 d / D)

PRESSURE

VESSEL

SHELL

COMPONENT

DESIGN

UNDER

INTERNAL PRESSURE Pressure Vessel Definition: – Containers of Pressure Internal External

– Pressure Source External Application of Heat

Code Coverage: – Subsections Rule, Guidelines, Specifications

– Mandatory Appendices Specific Important Subjects to Supplement Subsections

– Non-Mandatory Appendices Additional Information, Suggested Good Practices

Inclusions: – Unfired Steam Boilers/ Generators Evaporators Heat Exchangers

– Direct Fired Vessels Gas Fired Jacketed Steam Kettles(Jacket Pressure less than 50 PSI)

Additional Interpretation: U V PATEL COLLEGE OF ENGINEERING

Page 53

– The code rules may not cover all designs & constructions procedures. Such additional design & construction procedure may be adopted which are safe and acceptable.

– Field fabrication are acceptable. – Other standards for components are acceptable

Guidelines for Designed Thickness (To be adopted): – (1/16)” excluding corrosion allowance for shell & head (Min.) – The above will not apply to heat transfer surface – (1/4)” min. for unfired steam boiler shell – (3/32)” min. excluding corrosion allowance for compressed air/ steam/ water service(for CS/AS)

– Corrosion allowance shall be based on experience/ field data(No value/ code recommended).

THICKNESS CALCULATIONS UNDER INTERNAL PRESSURE, CYLINDRICAL SHELL: Circumferential stress: t

= P.Ri / (SE- 0.6P) + CA

Longitudinal stress: t = P.Ri / (2SE+0.4P) + CA SPHERICAL SHELL: t = P.Ri

/ (2SE- 0.2P) + CA

CONICAL SECTION: (INTERNAL PRESSURE) t =P.Di/ 2COSα(SE- 0.6P) + CA

Stress Calculation UNDER INTERNAL PRESSURE, CYLINDRICAL SHELL: Circumferential stress: U V PATEL COLLEGE OF ENGINEERING

Page 54

Sc = P (Ri + 0.6t)/ Et Longitudinal stress: Sl = P (Ri - 0.4t)/ 2Et SPHERICAL SHELL: Sc = P (Ri + 0.2t)/ 2Et CONICAL SHELL SECTION: Sc =P (Di + 1.2 tCOSα)/2Et COSα Sl =P (Di – 0.8tCOSα)/4Et COSα


Page 55

ANALYSIS OF PRESSURE VESSEL

Project Author

jimit and mahavir Subject

shell analysis Prepared For

project report Project Created

Sunday, May 25, 2008 at 10:04:27 PM Project Last Modified

Sunday, May 25, 2008 at 10:04:27 PM


Page 56

1 Introduction The ANSYS CAE (Computer-Aided Engineering) software program was used in conjunction with 3D CAD (Computer-Aided Design) solid geometry to simulate the behavior of mechanical bodies under thermal/structural loading conditions. ANSYS automated FEA (Finite Element Analysis) technologies from ANSYS, Inc. to generate the results listed in this report. Each scenario presented below represents one complete engineering simulation. The definition of a simulation includes known factors about a design such as material properties per body, contact behavior between bodies (in an assembly), and types and magnitudes of loading conditions. The results of a simulation provide insight into how the bodies may perform and how the design might be improved. Multiple scenarios allow comparison of results given different loading conditions, materials or geometric configurations. Convergence and alert criteria may be defined for any of the results and can serve as guides for evaluating the quality of calculated results and the acceptability of values in the context of known design requirements. Solution history provides a means of assessing the quality of results by examining how values change during successive iterations of solution refinement. Convergence criteria sets a specific limit on the allowable change in a result between iterations. A result meeting this criteria is said to be "converged". Alert criteria define "allowable" ranges for result values. Alert ranges typically represent known aspects of the design specification.

All values are presented in the "SI Metric (m, kg, N, °C, s, V, A)" unit system. Notice

Do not accept or reject a design based solely on the data presented in this report. Evaluate designs by considering this information in conjunction with experimental test data and the practical experience of design engineers and analysts. A quality approach to engineering design usually mandates physical testing as the final means of validating structural integrity to a measured precision.


Page 57

2. Scenario 1

2.1. "Model" "Model" obtains geometry from the Pro/ENGINEER® cylinder\SHEEL.PRT.2".

part

"H:\shaell and

The bounding box for the model measures 1.73 by 0.52 by 0.52 m along the global x, y and z axes, respectively. The model has a total mass of 109.69 kg. The model has a total volume of 1.4×10-2 m³. Table 2.1.1. Bodies Name

Material

Nonlinear Material Effects Bounding Box(m) Mass (kg) Volume (m³) Nodes Elements

"SHEEL" "Structural Steel" Yes

1.73, 0.52, 0.52

109.69

1.4×10-2

4968

684

2.1.1. Mesh "Mesh", associated with "Model" has an overall relevance of 0. "Mesh" contains 4968 nodes and 684 elements.

No mesh controls specified.

2.2. "Environment" Simulation Type is set to Static Analysis Type is set to Static Structural

"Environment" contains all loading conditions defined for "Model" in this scenario.

2.2.1. Structural Loading Table 3.2.1.1. Structural Loads Name

Type

Magnitude

Vector

"Pressure" Pressure 600,000.0 Pa N/A

Reaction Force

Reaction Vector

N/A

N/A

Force Reaction Moment N/A

Reaction Vector

Moment

N/A

2.2.2. Structural Supports Table 3.2.2.1. Structural Supports Name

Type

Reaction Force

Reaction Force Vector

"Fixed Support"

Fixed Surface

1.71×10-3 N

[-1.71×10-3 N x, 1.16×10-7 N y, 1.81×10-5 N·m 3.67×10-9 N z]


Reaction Moment

Reaction Moment Vector [1.81×10-5 N·m x, 3.16×10-9 N·m y, 1.06×10-7 N·m z]

Page 58

2.3. "Solution" Solver Type is set to Program Controlled Weak Springs is set to Program Controlled Large Deflection is set to Off

"Solution" contains the calculated response for "Model" given loading conditions defined in "Environment". Thermal expansion calculations use a constant reference temperature of 22.0 °C for "SHEEL". Theoretically, at a uniform temperature of 22.0 °C no strain results from thermal expansion or contraction.

2.3.1. Structural Results Table 3.3.1.1. Values Minimum

Maximum

Minimum Occurs Maximum Occurs Alert On On Criteria

A1.1

"Model" 8.6×106 Pa

3.5×107 Pa

SHEEL

SHEEL

None

None

"Model" 4.96×106 Pa 1.87×107 Pa SHEEL

SHEEL

None

A1.2

"Model" 0.0 m

4.27×10-5 m SHEEL

SHEEL

None

Name

Figure Scope

"Equivalent Stress"

"Maximum Stress"

Shear

"Total Deformation"

Convergence tracking not enabled.

2.3.2. Equivalent Stress Safety Table 3.3.2.1. Definition Name

Stress Limit

"Stress Tool" Yield strength per material. Table 3.3.2.2. Results Name

Scope

Type

Minimum Alert Criteria

"Stress Tool" "Model"

Safety Factor

7.13

None

"Stress Tool" "Model"

Safety Margin 6.13

None


2.3.3. Shear Stress Safety Table 3.3.3.1. Definition Name

Shear Limit

Shear Factor


Page 59

"Stress Tool 2" Yield strength per material. 0.5 Table 3.3.3.2. Results Name

Scope

Type

Minimum Alert Criteria

"Stress Tool 2" "Model"

Safety Factor

6.69

None

"Stress Tool 2" "Model"

Safety Margin 5.69

None


stress Figure A1.1. "Equivalent Stress" Contours


Page 60

Scenario 1 Figures deformation Figure A1.2. "Total Deformation" Contours


Page 61

AppendicesA1.

A2. Definition of "Structural Steel" Table A2.1. "Structural Steel" Constant Properties Name

Value

Compressive Ultimate Strength

0.0 Pa

Compressive Yield Strength

2.5×108 Pa

Density

7,850.0 kg/m³

Poisson's Ratio

0.3

Tensile Yield Strength

2.5×108 Pa

Tensile Ultimate Strength

4.6×108 Pa

Young's Modulus

2.0×1011 Pa

Thermal Expansion

1.2×10-5 1/°C

Specific Heat

434.0 J/kg·°C

Thermal Conductivity

60.5 W/m·°C

Relative Permeability

10,000.0

Resistivity

1.7×10-7 Ohm·m

Table A2.2. Alternating Stress


Page 62

Mean Value 0.0 Table A2.3. "Alternating Stress" Cycles

Alternating Stress

10.0

4.0×109 Pa

20.0

2.83×109 Pa

50.0

1.9×109 Pa

100.0

1.41×109 Pa

200.0

1.07×109 Pa

2,000.0

4.41×108 Pa

10,000.0

2.62×108 Pa

20,000.0

2.14×108 Pa

100,000.0

1.38×108 Pa

200,000.0

1.14×108 Pa

1,000,000.0

8.62×107 Pa

Table A2.4. Strain-Life Parameters

Table A2.5. "Strain-Life Parameters" Strength Coefficient

9.2×108 Pa

Strength Exponent

-0.11

Ductility Coefficient

0.21


Page 63

Ductility Exponent

-0.47

Cyclic Strength Coefficient

1.0×109 Pa

Cyclic Strain Hardening Exponent

0.2


Page 64

Project Author Subject Prepared for First Saved Last Saved Product Version

Jimit vyas and mahavir solanki Ellipsoidal dish end project analysis Sunday, May 25, 2008 Sunday, May 25, 2008 11.0 Release


Page 65

Contents •

•

Model o Geometry ELIPTICALHEAD o Mesh CFX-Mesh Method o Static Structural Analysis Settings Loads Solution Solution Information Results Max Equivalent Stress Results Max Shear Stress Results Material Data o Structural Steel

Units TABLE 1 Unit System Metric (m, kg, N, °C, s, V, A) Angle Degrees Rotational Velocity rad/s

Model Geometry TABLE Model > Geometry > Parts

3 Object Name State Graphics Properties Visible Transparency Definition Suppressed Material Stiffness Behavior Nonlinear Material Effects Bounding Box Length X Length Y Length Z


ELIPTICALHEAD Meshed Yes 1 No Structural Steel Flexible Yes 0.508 m 0.508 m 0.173 m

Page 66

Properties Volume Mass Centroid X Centroid Y Centroid Z Moment of Inertia Ip1 Moment of Inertia Ip2 Moment of Inertia Ip3 Statistics Nodes Elements

1.9271e-003 m³ 15.128 kg -8.1168e-017 m 1.0962e-017 m -3.7996e-002 m 0.34417 kg·m² 0.343 kg·m² 0.6178 kg·m² 2289 6232

Mesh TABLE Model > Mesh

4 Object Name State Defaults Physics Preference Relevance Advanced Relevance Center Element Size Shape Checking Solid Element Midside Nodes Straight Sided Elements Initial Size Seed Smoothing Transition Statistics Nodes Elements

TABLE Model > Mesh > Mesh Controls Object Name State Scope Scoping Method Geometry Definition Suppressed Method Element Midside Nodes

Mesh Solved CFD 0 Fine Default CFD Dropped Active Assembly Medium Slow 2289 6232 5

CFX-Mesh Method Fully Defined Geometry Selection 1 Body No CFX-Mesh Dropped

Static Structural U V PATEL COLLEGE OF ENGINEERING

Page 67

TABLE Model > Analysis

6 Object Name State Definition Physics Type Analysis Type Options Reference Temp

TABLE Model > Static Structural > Loads Object Name State Scope Scoping Method Geometry Definition Define By Type Magnitude Suppressed

Static Structural Fully Defined Structural Static Structural 22. °C 8

Pressure Fully Defined

Fixed Support 2

Geometry Selection 4 Faces 1 Face Normal To Pressure Fixed Support 6.e+005 Pa (ramped) No

FIGURE Model > Static Structural > Pressure


1

Page 68

Solution TABLE Model > Static Structural > Solution Object Name Solution State Solved Adaptive Mesh Refinement Max Refinement Loops 1. Refinement Depth 2.

9

TABLE Model > Static Structural > Solution > Solution Information Object Name Solution Information State Solved Solution Information Solution Output Solver Output Newton-Raphson Residuals 0 Update Interval 2.5 s Display Points All

10

TABLE Model > Static Structural > Solution > Results Object Name Equivalent Stress State Solved Scope Geometry All Bodies Definition Type Equivalent (von-Mises) Stress Display Time End Time Results Minimum 3.101e+006 Pa Maximum 3.1378e+007 Pa Information Time 1. s Load Step 1 Substep 1 Iteration Number 1

11

FIGURE Model > Static equivalent stress

Structural

>

Maximum Shear Stress Total Deformation


1.6131e+006 Pa 1.6963e+007 Pa

Solution


>

Equivalent

0. m 4.1032e-005 m

Stress

>

2 Figure

Page 69

FIGURE Model > Static Structural maximum shear stress

>

Solution


>

Maximum

Shear

Stress

>

3 Figure

Page 70

TABLE Model > Static Structural > Solution > Stress Safety Tools Object Name Max Equivalent Stress State Solved Definition Theory Max Equivalent Stress Stress Limit Type Tensile Yield Per Material

12

TABLE Model > Static Structural > Solution > Max Equivalent Stress > Results Object Name Safety Factor Safety Margin State Solved Scope Geometry All Bodies Definition Type Safety Factor Safety Margin Display Time End Time Results Minimum 7.9674 6.9674

13


Page 71

Information Time Load Step Substep Iteration Number

1. s 1 1 1

TABLE Model > Static Structural > Solution > Stress Safety Tools Object Name Max Shear Stress State Solved Definition Theory Max Shear Stress Factor 0.5 Stress Limit Type Tensile Yield Per Material

14

TABLE Model > Static Structural > Solution > Max Shear Stress > Results Object Name Safety Factor Safety Margin State Solved Scope Geometry All Bodies Definition Type Safety Factor Safety Margin Display Time End Time Results Minimum 7.369 6.369 Information Time 1. s Load Step 1 Substep 1 Iteration Number 1

15

Material Data Structural Steel TABLE Structural Steel > Constants Structural Young's Modulus Poisson's Ratio Density Thermal Expansion Tensile Yield Strength Compressive Yield Strength Tensile Ultimate Strength Compressive Ultimate Strength Thermal


16

2.e+011 Pa 0.3 7850. kg/m³ 1.2e-005 1/°C 2.5e+008 Pa 2.5e+008 Pa 4.6e+008 Pa 0. Pa

Page 72

Thermal Conductivity Specific Heat Electromagnetics Relative Permeability Resistivity

60.5 W/m·°C 434. J/kg·°C 10000 1.7e-007 Ohm·m

FIGURE Structural Steel > Alternating Stress

4

TABLE Structural Steel > Alternating Stress > Property Attributes Interpolation Log-Log Mean Curve Type Mean Stress

17

TABLE Structural Steel > Alternating Stress > Alternating Stress Curve Data Mean Value Pa 0.

18

TABLE Structural Steel > Alternating Stress > Alternating Stress vs. Cycles Cycles Alternating Stress Pa 10. 3.999e+009 20. 2.827e+009 50. 1.896e+009 100. 1.413e+009

19


Page 73

200. 2000. 10000 20000 1.e+005 2.e+005 1.e+006

1.069e+009 4.41e+008 2.62e+008 2.14e+008 1.38e+008 1.14e+008 8.62e+007

FIGURE Structural Steel > Strain-Life Parameters

5

TABLE Structural Steel > Strain-Life Parameters > Property Attributes Display Curve Type Strain-Life

20

TABLE Structural Steel > Strain-Life Parameters > Strain-Life Parameters Strength Coefficient Pa 9.2e+008 Strength Exponent -0.106 Ductility Coefficient 0.213 Ductility Exponent -0.47 Cyclic Strength Coefficient Pa 1.e+009 Cyclic Strain Hardening Exponent 0.2

21


Page 74

FATIGUE ANALYSIS Project Author

JIMIT AND MAHAVIR

Subject

FATIGUE ANALYSIS

Prepared for

DESIGN AND ANALYSIS OF PRESSURE VESSEL

First Saved

Monday, March 17, 2008

Last Saved

Tuesday, March 18, 2008

Product Version 11.0 Release


Page 75

Contents • Model o

Geometry

FATIGUEANALYSIS o

Mesh

o

Static Structural

Analysis Settings Loads Solution Solution Information Results Max Equivalent Stress Results Max Shear Stress Results Fatigue Tool Results Result Charts goodman stress life rl Results • o

Material Data

Structural Steel 2

Units TABLE 1 Unit System

Metric (m, kg, N, °C, s, V, A)

Angle

Degrees

Rotational Velocity rad/s


Page 76

Model Geometry TABLE Model > Geometry Object Name

Geometry

State

Fully Defined

Definition Source

D:\pressurevesselanalysis\fatigueanalysis\FATIGUEANALYSIS.PRT.3

Type

ProEngineer

Length Unit

Millimeters

Element Control Program Controlled Display Style

Part Color

Bounding Box Length X

0.762 m

Length Y

0.782 m

Length Z

2.08 m

Properties Volume

0.30847 m³

Mass

2421.5 kg

Statistics Bodies

1

Active Bodies

1

Nodes

12181

Elements

6191

TABLE Model > Geometry > Parts Object Name

FATIGUEANALYSIS

State

Meshed


Page 77

Graphics Properties Visible

Yes

Transparency

1

Definition Suppressed

No

Material

Structural Steel 2

Stiffness Behavior

Flexible

Nonlinear Material Effects Yes Bounding Box Length X

0.762 m

Length Y

0.782 m

Length Z

2.08 m

Properties Volume

0.30847 m³

Mass

2421.5 kg

Centroid X

-2.3696e-003 m

Centroid Y

2.1709e-003 m

Centroid Z

-8.3295e-004 m

Moment of Inertia Ip1

522.75 kg·m²


522.8 kg·m²


80.459 kg·m²

Statistics Nodes

12181

Elements

6191

Common Decisions to Both Types of Fatigue Analysis Once the decision on which type of fatigue analysis to perform, Stress Life or Strain Life, there are 4 other topics upon which your fatigue results are dependent upon. Input decisions that are common to both types of fatigue analyses are listed below: • Loading Type • Mean Stress Effects U V PATEL COLLEGE OF ENGINEERING

Page 78

• Multiaxial Stress Correction • Fatigue Modification Factor Within Mean Stress Effects, the available options are quite different. In the following ections, we will explore all of these additional decisions.

These input decision trees for

both Stress Life and Strain Life are outlined in Figures 1 and 2.

fatigue analysis in both

predicted life and types of post processing available. We will look at each of these choices in detail below.

Mesh TABLE Model > Mesh Object Name

Mesh

State

Solved

Defaults Physics Preference

Mechanical

Relevance

0

Advanced Relevance Center

Coarse

Element Size

Default

Shape Checking

Standard Mechanical

Solid Element Midside Nodes Program Controlled Straight Sided Elements

No

Initial Size Seed

Active Assembly

Smoothing

Low

Transition

Fast

Statistics Nodes

12181

Elements

6191


Page 79

Static Structural TABLE Model > Analysis Object Name

Static Structural

State

Fully Defined

Definition Physics Type

Structural

Analysis Type

Static Structural

Options Reference Temp 22. °C TABLE Model > Static Structural > Analysis Settings Object Name

Analysis Settings

State

Fully Defined

Step Controls Number Of Steps

1.

Current Step Number 1. Step End Time

1. s Program Controlled

TABLE Model > Static Structural > Loads Object Name

Pressure

State

Fully Defined

Fixed Support

Scope Scoping Method Geometry Selection Geometry

10 Faces

2 Faces

Definition Define By

Normal To

Type

Pressure

Magnitude

-6.e+005 Pa (ramped)

Suppressed

No


Fixed Support

Page 80

FIGURE Model > Static Structural > Pressure

Solution TABLE Model > Static Structural > Solution Object Name

Solution

State

Obsolete

Adaptive Mesh Refinement Max Refinement Loops 1. Refinement Depth

2.

TABLE Model > Static Structural > Solution > Solution Information Object Name

Solution Information

State

Not Solved

Solution Information Solution Output


Solver Output

Page 81

Newton-Raphson Residuals 0 Update Interval

2.5 s

Display Points

All

TABLE Model > Static Structural > Solution > Results Object Name

Equivalent Stress

State

Solved


Scope Geometry

All Bodies

Definition Type

Equivalent (von-Mises) Stress Maximum Shear Stress Total Deformation

Display Time

End Time

Results Minimum

4.7782 Pa

2.757 Pa

0. m

Maximum

6.4722e+007 Pa

3.5341e+007 Pa

4.4133e-004 m

Information Time

1. s

Load Step

1

Substep

1

Iteration Number 1 TABLE Model > Static Structural > Solution > Stress Safety Tools Object Name

Max Equivalent Stress

State

Solved

Definition Theory

Max Equivalent Stress

Stress Limit Type Tensile Yield Per Material TABLE Model > Static Structural > Solution > Max Equivalent Stress > Results Object Name

Safety Factor Safety Margin

State

Solved

Scope


Page 82

Geometry

All Bodies

Definition Type


Display Time

End Time

Results Minimum

3.8627

2.8627

Information Time

1. s

Load Step

1

Substep

1

Iteration Number 1 TABLE Model > Static Structural > Solution > Stress Safety Tools Object Name

Max Shear Stress

State

Solved

Definition Theory

Max Shear Stress

Factor

0.5

Stress Limit Type Tensile Yield Per Material TABLE Model > Static Structural > Solution > Max Shear Stress > Results Object Name


State

Solved

Scope Geometry

All Bodies

Definition Type


Display Time

End Time

Results Minimum

3.537

2.537

Information Time

1. s


Page 83

Load Step

1

Substep

1

Iteration Number 1 TABLE Model > Static Structural > Solution > Fatigue Tools Object Name

Fatigue Tool

State

Solved

Materials Fatigue

Strength

Factor (Kf)

1.

Loading History Data

Type History

Data C:\Program

Files\Ansys

Inc\v110\AISOL\CommonFiles\Language\en-

Location

us\EngineeringData\Load Histories\sampleHistory2.dat

Scale Factor

5.e-003

Definition End Time

Display Time Options

Stress Life

Analysis Type

Mean Stress Theory Goodman Stress Component

Equivalent (Von Mises)

Bin Size

32

Use Quick Rainflow Counting

1.e+009 cycles

Infinite Life Maximum

Yes

Data

Points To Plot

5000.

Life Units Units Name

cycles

1 block is equal to

1.e+006 cycles

Non-constant amplitude, Proportional Loading U V PATEL COLLEGE OF ENGINEERING

Page 84

Non-constant amplitude, proportional loading also needs only one set of FE results. But instead of using a single load ratio to calculate alternating and mean values, the load ratio varies over time. Think of this as coupling an FE analysis with strain-gauge results collected over a given time interval. Since loading is proportional, the critical fatigue location can be found by looking at a single set of FE results.

However, the fatigue

loading which causes the maximum damage cannot easily be seen. Thus, cumulative damage calculations (including cycle counting such as Rainflow and damage summation such as Miner’s rule) need to be done to determine the total amount of fatigue damage and which cycle combinations cause thatdamage. Cycle counting is a means to reduce a complex load history into a number of events, which can be compared to the available constant amplitude test data. Non-constantAmplitude, proportional loading within the ANSYS Fatigue Module uses a “quick counting” technique to substantially reduce runtime and memory. In quick counting, alternating andmean stresses are sorted into bins before partial damage is calculated. Without quick counting, data is not sorted into bins until after partial

damages

are

found.

The

accuracy

of

quick

counting is usually very good if a proper number of bins are used when counting. The bin size defines how many divisions the cycle counting history should be organized into for the history data loading type. Strictly speaking, bin size specifies the number of divisions of the rainflow matrix. A larger bin size has greater precision but will take longer to solve and use more memory. Bin size defaults to 32, meaning that the Rainflow Matrix is 32 x 32 in dimension. For Stress Life, another available option when conducting a variable amplitude fatigue analysis is the ability to set the value used for infinite life. In constant amplitude loading, if the alternating stress is lower than the lowest alternating stress on the fatigue curve, the fatigue tool will use the life at the last point. This provides for an added level of safety because many materials do not exhibit an endurance limit.

However, in non-constant

amplitude loading, cycles with very small alternating stresses may be present and may incorrectly predict too much damage if the number of the small stress cycles is high enough. To help control this, the user can set the infinite life value that will be used if the alternating stress is beyond the limit of the SN curve. Setting a higher value will make small stress cycles less damaging if they occur many times. The Rainflow and damage U V PATEL COLLEGE OF ENGINEERING

Page 85

matrix results can be helpful in determining the effects of small stress cycles in your loading history. FIGURE Model > Static Structural > Solution > Fatigue Tool

FIGURE Model > Static Structural > Solution > Fatigue Tool


Page 86

TABLE Model > Static Structural > Solution > Fatigue Tool > Results

Object Name Life State

Safety Factor Damage

Solved

Scope

Geometry

All Bodies

Definition

Type

Life

Safety Factor Damage 1.e+009 cycles

Design Life Results

Minimum

2.e+007 cycles 0.

Maximum

50.

TABLE Model > Static Structural > Solution > Fatigue Tool > Result Charts U V PATEL COLLEGE OF ENGINEERING

Page 87

Object Name

Rainflow Matrix Damage Matrix

State

Solved

Scope

Geometry

All Bodies

Options

Chart Viewing Style Three Dimensional Results

Minimum Range

0. Pa

Maximum Range

1.9246e+008 Pa

Minimum Mean

-3.2328e+008 Pa

Maximum Mean

6.1628e+007 Pa

Definition

Design Life

1.e+009 cycles

FIGURE Model > Static Structural > Solution > Fatigue Tool > Rainflow Matrix Rainflow Matrix Chart Rainflow Matrix Chart is a plot of the rainflow matrix at the critical location. This result is onlyapplicable for non-constant amplitude loading where rainflow counting is needed. This result may be scoped. In this 3-D histogram, alternating and mean stress is divided into bins and plotted. The Z-axis corresponds to the number of counts for a given alternating and mean stress bin. This result gives the user a measure of the composition of a loading history. (Such as if most of the alternating stress cycles occur at a negative mean stress.) From the rainflow matrix figure, the user can see that most of the alternating stresses have a positive mean stress and that in this case the majority of alternating stresses are quite low.


Page 88

FIGURE Model > Static Structural > Solution > Fatigue Tool > Damage Matrix

Damage Matrix Chart Damage Matrix Chart is a plot of the damage matrix at the critical location on the model. This result is only applicable for non-constant amplitude loading where rainflow counting is needed. This result may be scoped. This result is similar to the rainflow matrix except that the percent damage that each of the Rainflow bin cause is plotted as the Z-axis. As can be seen from the \corresponding damage matrix for the above rainflow matrix, in this particular case although most of the counts occur at the lower stress amplitudes, most of the damage occurs at the higher stress amplitudes.


Page 89

TABLE Model > Static Structural > Solution > Fatigue Tools

Object Name

goodman stress life rl

State

Solved

Materials

Fatigue Strength Factor (Kf) 1. Loading

Type

Fully Reversed

Scale Factor

1.

Definition

Display Time

End Time

Options

Analysis Type

Stress Life

Mean Stress Theory

Goodman


Page 90

Equivalent (Von Mises)

Stress Component Life Units

Units Name

cycles

1 cycle is equal to

1.e+006 cycles

Types of Cyclic Loading Unlike static stress, which is analyzed with calculations for a single stress state, fatigue damage occurs when stress at a point changes over time. There are essentially four classes of fatigue loading, with the ANSYS Fatigue Module currently supporting the first three: • Constant amplitude, proportional loading • Constant amplitude, non-proportional loading • Non-constant amplitude, proportional loading • Non-constant amplitude, non-proportional loading In the above descriptions, the amplitude identifier is readily understood. Is the loading a variant of a sine wave with a single load ratio or does the loading vary perhaps erratically, with the load ratio changing with time? The second identifier, proportionality, describes whether the changing load causes the principal stress axes to change.

If the principal stress

axes do not change, then it is proportional loading. If the principal stress axes

do

change,

then

the

cycles

cannot

be

counted simply and it is non-proportional loading. Constant amplitude, Proportional Loading Constant amplitude, proportional loading is the classic, “back of the envelope” calculation describing whether the load has a constant maximum value or continually varies with time. Loading is of constant amplitude because only one set of FE stress results along with a loading ratio is required to calculate the alternating and mean values. U V PATEL COLLEGE OF ENGINEERING

Page 91

The loading ratio is defined as the ratio of the second load to the first load (LR = L2/L1). Loading is proportional since only one set of FE results are needed (principal stress axes do not change over time). Common types of constant amplitude loading are fully reversed (apply a load, then apply an equal and opposite load; a load ratio of -1) and zero-based (apply a load then remove it; a load ratio of 0). Since loading is proportional, looking at a single set of FE results can identify critical fatigue locations. Likewise, since there are only two loadings, no cycle counting or cumulative damage calculations need to be done.

FIGURE Model > Static Structural > Solution > goodman stress life rl

Value of Infinite Life Another available option when conducting a variable amplitude fatigue analysis is the ability to set the value used for infinite life.

In constant amplitude loading, if the

alternating stress is lower than the lowest alternating stress on the fatigue curve, the U V PATEL COLLEGE OF ENGINEERING

Page 92

fatigue tool will use the life at the last point. This provides for an added level of safety because many materials do not exhibit an endurance limit. However, in non-constant amplitude loading, cycles with very small alternating stresses may be present and may incorrectly predict too much damage if the number of the small stress cycles is high enough. To help control this, the user can set the infinite life value that will be used if the alternating stress is beyond the limit of the SN curve. Setting a higher value will make small stress cycles less damaging if they occur many times. The rainflow and damage matrix results can be helpful in determining the effects of small stress cycles in your loading history. The rainflow and damage matrices shown in Figure 13 illustrates the possible effects of infinite life. Both damage matrices came from the same loading (and thus same rainflow matrix), but the first damage matrix was calculated with an infinite life if 1e6 cycles and the second was calculated with an infinite life of 1e9 cycles.

FIGURE Model > Static Structural > Solution > goodman stress life rl

TABLE Model > Static Structural > Solution > goodman stress life rl > Results

Object Name Life State

Damage Safety Factor Equivalent Alternating Stress

Solved

Scope

Geometry

All Bodies

Definition

Type Design Life

Life

Damage Safety Factor Equivalent Alternating Stress 1.e+009 cycles


Page 93

Results

Minimum

1.e+012 cycles

8.895

4.7782 Pa

1.e-003

Maximum

6.4722e+007 Pa

Material Data Structural Steel 2 TABLE Structural Steel 2 > Constants Structural

Young's Modulus

2.e+011 Pa

Poisson's Ratio

0.3

Density

7850. kg/m³

Thermal Expansion

1.2e-005 1/°C

Tensile Yield Strength

2.5e+008 Pa

Compressive Yield Strength

2.5e+008 Pa

Tensile Ultimate Strength

4.6e+008 Pa

Compressive Ultimate Strength 0. Pa Thermal

Thermal Conductivity

60.5 W/m·°C

Specific Heat

434. J/kg·°C

Electromagnetics

Relative Permeability

10000

Resistivity

1.7e-007 Ohm·m


Page 94

FIGURE Structural Steel 2 > Alternating Stress

TABLE Structural Steel 2 > Alternating Stress > Property Attributes

Interpolation

Log-Log

Mean Curve Type Mean Stress


Page 95

TABLE Structural Steel 2 > Alternating Stress > Alternating Stress vs. Cycles

Cycles

Alternating Stress Pa

10.

3.999e+009

20.

2.827e+009

50.

1.896e+009

100.

1.413e+009

200.

1.069e+009

2000.

4.41e+008

10000

2.62e+008

20000

2.14e+008

1.e+005 1.38e+008 2.e+005 1.14e+008 1.e+006 8.62e+007 FIGURE Structural Steel 2 > Strain-Life Parameters


Page 96

TABLE Structural Steel 2 > Strain-Life Parameters > Property Attributes

Display Curve Type Strain-Life TABLE Structural Steel 2 > Strain-Life Parameters > Strain-Life Parameters

Strength Coefficient Pa

9.2e+008

Strength Exponent

-0.106

Ductility Coefficient

0.213

Ductility Exponent

-0.47

Cyclic Strength Coefficient Pa

1.e+009

Cyclic Strain Hardening Exponent 0.2


Page 97

Wind analysis Contents 1. File Table 2. Mesh Table 3. Physics Table Table 4. Solution Table 5. User Figure Figure Figure 4

1 File 2 Mesh

Information

for

Information

for

3 Domain 4 Boundary

Physics Physics

for for

5 Boundary

Flows

for

Report windanalysiscfx11_001 Report windanalysiscfx11_001 Report windanalysiscfx11_001 windanalysiscfx11_001 Report windanalysiscfx11_001 Data 2 3

Fig: Wind analysis


Page 98

1. File Report Table 1. File Information for windanalysiscfx11_001

Case

windanalysiscfx11_001

File Path

D:/pressurevesselanalysis/windanalysiscfx11_001.res

File Date

15 March 2008

File Time

03:46:08 PM

File Type

CFX5

File Version 11.0 Fluids

Air at 25 C

Solids

None

Particles

None

Figure 2. pressure distributation on face of vessel U V PATEL COLLEGE OF ENGINEERING

Page 99

2. Mesh Report Table 2. Mesh Information for windanalysiscfx11_001

Domain

Nodes

Elements

pressurevessel

7338

28308

Figure 3. streamline and pressure representation


Page 100

3. Physics Report Table 3. Domain Physics for windanalysiscfx11_001

Name

Location Type Materials

pressurevessel B4

Models

Heat Transfer Model = Isothermal Turbulence Model = SST Fluid Air at 25 C Turbulent Wall Functions = Automatic Buoyancy Model = Non Buoyant Domain Motion = Stationary

Table 4. Boundary Physics for windanalysiscfx11_001

Domain

Name

pressurevessel inlet

Location

inlet

Type

Settings

Inlet

Flow Regime = Subsonic Normal Speed = 47 [m s^-1] Mass And Momentum = Normal Speed Eddy Length Scale = 0.1 [m] Fractional Intensity = 0.05 Turbulence = Intensity and Length Scale Flow Regime = Subsonic Mass And Momentum = Static Pressure Relative Pressure = 0 [Pa]

pressurevessel outlet

outlet

Outlet

pressurevessel symp

symp

Symmetry

pressurevessel body

body

Wall

Wall Influence On Flow = No Slip

pressurevessel freewalls

freewalls

Wall

Wall Influence On Flow = Free Slip

F41.4, F45.4

Wall

Wall Influence On Flow = No Slip

pressurevessel

pressurevessel Default


Page 101

4. Solution Report Table 5. Boundary Flows for windanalysiscfx11_001

Mass Flow

Momentum

Location

Type

body

Boundary 0.0000e+00

-1.7561e+03 2.7605e+02

-8.3776e+01

freewalls

Boundary 0.0000e+00

-1.4953e+02 0.0000e+00

0.0000e+00

inlet

Boundary 1.7405e+02

-5.1811e-07 -8.5229e+03 1.5579e-06

outlet

Boundary -1.7405e+02 1.3129e+01

X

Y

8.1929e+03

Z

-2.3151e+00

pressurevessel Default Boundary 0.0000e+00

-1.9325e-02 5.4447e+01

8.5967e+01

symp

1.8922e+03

0.0000e+00

Boundary 0.0000e+00

0.0000e+00

By interpolation we get: for 41 m/s of wind speed the wind pressure is 730 N/ m2

and from the standard wind

load table we compare the result which is very accurate.


Page 102

INTRODUCTION TO GLASS LINING

Introduction of Glass lining (Glasteel) In recent years, because of the expansion of the chemical process and pharmaceutical industries world-wide and increased concerns for safety and quality control, Pfaudler began investigating new approaches in glass development that would lead to a glass composition that could be made available to all users of glass-lined equipment.


Page 103

Together with the chemical process industry and with the co-operation of Pfaudler divisions around the world, Pfaudler established the criteria for a new composition: A non-crystalline structure. Increased resistance to acid and alkali corrosion. High resistance to impact. High resistance to thermally induced stresses. A formulation that could be easily produced by all Pfaudler manufacturing plants.

The result is Glasteel 9100®, Pfaudler's first "international glass", offering an unmatched combination of corrosion resistance, impact strength, thermal shock resistance, nonadherence and heat transfer efficiency. Now GMM Pfaudler customers, regardless of where their processing operations are located, can purchase a single glass system and be assured of getting the same high quality worldwide. With Glasteel 9100 ®, GMM Pfaudler sets a standard the world can depend on.

glass. However, these are very recipe sensitive and general statements cannot usually be made. An exception to this are chemistries that involve the element silicon (Si), especially when ionised, e.g. Si, SiO. Relatively small amounts of dissolved SiO can be highly effective in reducing the corrosion rate of the Glasteel 9100 system, thereby greatly extending its usage range. It has also been shown that colloidal silica additions to recipes containing the highly corrosive fluorine ion (F-) can drastically reduce the corrosive rate.


Page 104

Water Pure Water Pure water in the liquid phase is not very aggressive. Its behaviour resembles highly diluted acid and corrodes only the surface layer of the glass ("ion exchange process"). At 170°C, a corrosion rate of 0.1 mm/year can be expected. But because this water is an unbuffered, pH-unstable system, even a slight alkalization can change the situation. If there is a shift toward higher pH values, the isocorrosion curves for diluted alkaline solutions have to be consulted for orientation purposes. Glasteel 9100 ® is highly resistant to condensing water vapour. However, to counter the possible danger of the condensate shifting to an alkaline pH, it is recommended that the vessel contents be slightly acidified with a volatile acid, e.g. hydrochloric or acetic acid. It is also highly recommended that the unjacketed top head be insulated or heat traced to reduce condensation formation. Agueous Neutral pHMedia With these type media, e.g. tap water, salt solutions, corrosion rate depends greatly on the type and quantity of the dissolved substance. Carbonates and phosphates usually increase the rate while alcohols and some ionic species, e.g. A13+, Zn2+ Ca2+, may reduce it.

Alkalis As alkali concentration rises, corrosion rate increases. Also, the temperature gradient for alkaline glass corrosion, is steeper. The result is that concentrated alkalis require a more definite setting of the temperature limits. The corrosion rate of concentrated alkaline solutions cannot be expressed by the pH value alone. For aqueous solutions of alkaline materials with a pH value of 14, the particular concentration must also be considered to establish appropriate operating temperatures. Other factors affecting alkaline corrosion are the specific reaction and the dissolving ability of the chemical, the influence of the nature and amount of other dissolved substances and agitation.


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Isocorrosion curves for sodium hydroxide, potassium hydroxide, sodium carbonate and ammonia take into account technically relevant parameters influencing the rate of corrosion; for example, the volume/ surface area ratio, inhibition effects by calcium ions, alkaline concentration and temperature. Under actual operating conditions, even very slight contamination (tap water in sodium hydroxide, for example) can cause major changes in the rate of corrosion. Other factors, such as product velocity and splash zone, can affect the corrosion rate as well. Due to these interactive complexities, meaningful testing is strongly advised. To eliminate the influence of the testing equipment on the rate of corrosion, procedures are carried out in polypropylene bottles. For solutions above the boiling point, autoclaves with PTFE inserts were used. By comparing the results with control experiments, it is proven that the testing equipment does not have an inhibiting effect. Pfaudler Ultra-Glas 6500 ®

1 . Extends the range of Glasteel® applications. 2. Allows safe and easy handling of high temperature processes never before approved for Glasteel equipment. 3. Provides potential for reduced cycle time compared to conventional vessel glass. 4. Provides extended thermal shock protection for faster heating and cooling. 5. Provides increased operating safety margin through its enhanced thermal protection. 6. Is ideal for the higher temperatures required by today's chemical process applications.


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The features of GMM Pfaudler Ultra-Glas 6500 ® are the result of changes in glass composition and material preparation, altered applications and firing procedures, as well as changes in equipment design and materials of construction. These changes permit trouble-free application of the required high-stress coating and provide the highly corrosive-resistant glass-lined surface for which Pfaudler has been respected for years. Technical details of corrosion rates in common chemicals and thermal operation limits are available on request.

Temperature Limits

Although Ultra-Glas 6500 ® has a high degree of helpful compressive stress in the glass layer there are definite limits to the level of thermal stress which the glass can withstand without incurring damage: Only two thermal conditions must be considered when determining the temperature limits: A. Introduction of media into a vessel. B. Introduction of media into a jacket. CAUTION: "Safe" operating temperatures vary with conditions. Because so many variables are involved, temperature ranges are given only as a guide. Where in practical, operation below the maximum and above the minimum is recommended. Contact Pfaudler for details. Type 4300 Glass Coatings Type 4300 ® glass coatings represent a new aspect of this tradition and are designed to bridge a perceived gap in the application range. GMM Pfaudler Type 4300 ® glass is still an acidic type of glass, but its primary application is based on improved alkali resistance. Type 4300 glass coatings are advisable wherever alkaline conditions prevail during the


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cycle, or as a result of concentration and temperature, or where concentration and/or temperature conditions exceed permissible limits for conventional glass. In addition, Type 4300 ® glass coatings are advisable where any of the following conditions exist: Protection of alkaline products against metal contamination. Danger of discoloration of alkaline products due to incorporation of metals. Stabilization of high-molecular alkalis sensitive to metal contact. Inadequate redox stability of the vessel material in the alkaline range.

Compared to our world renowned standard glass, Type 4300 ® has three times better alkali resistance. This means that higher process temperatures can be used, or that, under otherwise equal conditions, these glass coatings will have three times the life expectations. The Type 4300 ® glass does make a slight concession in the area of acid resistance. Although it is adequate for mild service, it is not recommended for aggressive acid conditions.

Corrosion Resistance For pure acids and bases most commonly used in the chemical industry , technically relevant parameters influencing the rate of corrosion (for example, the volume/surface area ratio, inhibition effects, concentration, and temperature) are considered. In practical operation these materials are always encountered with liquid additives, dissolved substances or gases which may have positive or negative effects on resistance. We therefore recommend performing corrosion tests or contacting a Pfaudler consultant to assure material suitability for individual processes. The Need For PPG


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When the requirements of the Bulk Drug industry were studied recently, in context of the stringent requirements of GMP and FDA, the need for a different glass was evident. Two of the requirements of the pharmaceutical industry are increased purity in order to comply with the FDA and GMP requirements and alternating alkali/acid operation. The process equipment of the chemical and pharmaceutical industries has so far been very similar - especially in terms of glasslined reactors and components. In light of the survey, Pfaudler's response was a novel glass tailored to the needs of manufacturing pharmaceutical products, vitamins and fine chemicals.


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Appendix


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BIBLOGRAPHY Dennis Moss Hiadri Farzdak C.S Sharma Somnath chatopadhay

For Ansys : Tutorials of cfx 11.0


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Design Analysis of PV

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