Tank Design Literature
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DESIGN AND ANALYSIS OF PRESSURE VESSEL
B Y JIMIT VYAS AND MAHAVIR SOLANKI GUIDED BY : MR BHAVESH PATEL
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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/t10. 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.
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 z Primary Stress { General: z
Primary general membrane stress Pm
z
Primary general bending stress Pb { Primary local stress, PL
z Secondary stress: { Secondary membrane stress. Qm { Secondary bending stress Qb z Peak stress. F
Definition and Examples z PRIMARY GENERAL STRESS: z
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
bending stresses. Calculated value of a primary bending stress may be allowed to go higher than that of a primary membrane stress. z Primary general membrane stress, Pm z Circumferential and longitudinal stress due to pressure. z Compressive and tensile axial stresses due to wind. z Longitudinal stress due to the bending of the horizontal vessel over the saddles. z Membrane stress in the centre of the flat head. z Membrane stress in the nozzle wall within the area of reinforcement due to pressure or external loads. z Axial compression due to weight. z Primary general bending stress, Pb z Bending stress in the centre of a flat head or crown of a dished head. z Bending stress in a shallow conical head. z Bending stress in the ligaments of closely spaced openings.
LOCAL PRIMARY MEMBRANE STESS, PL z 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 z Pm+ membrane stresses from local sustained loads: { Support legs { Nozzle loads { Beam supports { Major attachments
SECONDARY STRESS z Secondary membrane stress Qm z Axial stress at the juncture of a flange and the hub of the flange z Thermal stresses.
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z Membrane stress in the knuckle area of the head. z Membrane stress due to local relenting loads. z Secondary bending stress, Qb z Bending stress at the gross structural discontinuity: nozzle, lugs, etc., (relenting loadings only). z The nonuniform portion of the stress distribution in a thick-walled vessels due to internal pressure. z
The stress variation of the radial stress due to internal pressure in thick-walled vessels.
z
Discontinuity stresses at stiffening or support ring.
z Peak Stress F z Stress at the corner of discontinuity. z Thermal stress in a wall caused by a sudden change in the surface temperature. z Thermal stresses in cladding or weld overlay. z Stress due to notch effect. (stress concentration).
LOADINGS z 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. z The stresses applied more or less continuously and uniformly across an entire section of the vessel are primary stresses. z The stresses due to pressure and wind are primary membrane stresses. z 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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z 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. z Basically each combination of stresses ( stress categories will have different allowables, i.e., z
Primary stress: Pm < SE
z
Primary membrane local (PL):
z
PL=Pm+ PL 1/2 head diameter –shall be designed as a bolted flange connection. 9. Openings in torispherical heads.
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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.
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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
Based on inside diameter
Vessels (Thickness>50mm) Based on inside diameter
5.2
All Other Vessels
Based on outside diameter
Tanks & Spheres
Based on inside diameter
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 ).
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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
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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.
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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.
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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.
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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
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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.
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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.
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CHAPTER 3
DESIGN
PROCEDURE
AND
CALUCULATION
͵
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 V 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 = V t1 × 2t × l
….( of two section)
…ii
From equation (i) and (ii) , we have
͵
V t1 × 2t × l = p × d × l
or
V t1 =
pud 2t
or
t =
pud 2V 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
V t 2 = Longitudinal stress.
In this case, the total force acting on the transverse section = Intensity of pressure × Cross- sectional Area =p×
S (d)² 4
………i
and total resisting force = V t 2 × d.t
………ii
From equation (i) and (ii), we have V t 2 × d.t = p × Vt 2 =
S (d) ² 4
pud pud or t = 4V t 2 4t
͵ͺ
Design of Shell Due to Internal Pressure As discussed in article on thin vessel are cylindrical pressure vessel is subjected to tangential ( V t ) and longitudinal ( V L ) stresses.
Vt
Pi u Di and V L 2t
Pi u Di 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,
K uV
Pi u ( Di t ) 2t
K u V u 2t
Pi u ( Di t )
t
Pi u Di 2(K u V ) 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:
͵ͻ
t=
pi diW 2V J
where, di = Major axis of ellipse W= Stress intensification factor
W Where ,
k=
1 (2 k 2 ) 6 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 (2 22 ) 6
W
=1
t
Pi di W 2 V 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 u Di 2 u V uK Pi
ͶͲ
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
(whichever is smaller)
h2 = h
or
h 2actual
(whichever is smaller)
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
Ͷͳ
Area Calculation Area pertaining to material removed,
A = d u 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:
WW
w2
Where,
¦W P2 0.707 u tW u LW u n
KP1 H 2 Do mm 2
WW
¦W 0.707 u tW u LW u 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
Ͷʹ
(IF H 20 m)
Mw =
Pw1h1 2
(IF H> 20m)
Mw =
Pw1h1 h + Pw 2 ( h1 + 2 ) 2 2
Therefore, bending stress will be, Vbw =
Mw z
Where Z= section Modulus
The wind load would create tensile stress on the wind side and compressive on the other side.
Ͷ͵
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 u Di + CA 2 u V uK Pi
t
(0.588) u (496) 2 u137 u 1 0.588
( CA is NIL)
= 1.066 ?
t = 1.066mm
2) Elliptical Head 1 (2 k 2 ) 6
W
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) W
1 (2 22 ) 6 =1
t
Pi di W 2 V J
where,
ͶͶ
di = Major axis of ellipse = 496mm W = Stress intensification factor = 1
t
Pi di W 2 V J
t
0.588 u 496 u 1 2 u137 u 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 (K ) = 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.
A
1
t
rn
0.588 u 254.51 2 u137 u 1 0.588
t
rn
Pi u Di 2 u V uK Pi
0.588 u 254.51 2 u137 u 1 0.588
Ͷͷ
= 0.547 mm.
t
rn
= 0.547 mm.
Area Calculation Area Pertaining to material removed, A = d u tr = 254.51 u 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 u 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 u 6
= 2.5 (9.27)
= 15mm
= 23.175 mm
( Take X whichever smaller)
h1 = h2 = h = 15 mm. Therefore, A2 = 2 u 15 ( 9.27 – 0.547 – 0) = 261.69 mm 2 Excess area in the nozzle inside the shell A3 = 2 h2 (tn – 2CA) = 2 u 15 ( 9.27-0)
Ͷ
= 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
Ͷ
=
4t(5t)3 3t(3t)3 6(5t)
= 13.96 t 3 Therefore, Bending Stress will be , Vbw =
350× 106 =
Mw z
(as V bw = 350 N/mm²)
755.41 13.96t 3
t = 5.36 × 103 m ? L=
123 123 + + 1834 3 3
= 1916 mm
Ͷͺ
SUMMARY
SHELL HEAD MANHOLE REINFORCEMENT PAD LEG
INTERNALDIAMETER(Di) LENGTH(L) THICKNESS(t) THICKNESS(t) HEIGHT(h) DIAMETEROFOPENING(di) THICKNESSOFNOZZLE(tn) ASAREACALCULATEDISve RFPADISNOTREQUIRED THICKNESSOFLEGS
496mm 1734mm 6mm 6mm 173mm 254.51 9.27
5.36mm
Ͷͻ
DESIGN
APPROCH
2
BY
ASME
CODES
ͷͲ
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)
ͷͳ
“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
z (USE NEAREST VALUE OF L/r; INTERPOLATION UNNECESSARY) z 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.
z CONICAL HEAD: t = PDi/ 2 COS (SE-0.6P) + CA = half apex angle
z HEMISPHERICAL HEAD: t = P.Ri/ (2SE- 0.2P) + CA
z 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)
z OBROUND/ NON-CIRCULAR HEADS (INCLUDING SQUARE/ RECTANGULAR)
ͷʹ
t = Di * SQRT(Z*CP/SE)
+ CA
where Z = 3.4 - (2.4 d / D)
PRESSURE
VESSEL
SHELL
COMPONENT
DESIGN
UNDER
INTERNAL PRESSURE z Pressure Vessel Definition: – Containers of Pressure z Internal z External
– Pressure Source z External z Application of Heat
z Code Coverage: – Subsections z Rule, Guidelines, Specifications
– Mandatory Appendices z Specific Important Subjects to Supplement Subsections
– Non-Mandatory Appendices
z Additional Information, Suggested Good Practices z Inclusions: – Unfired Steam Boilers/ Generators z Evaporators z Heat Exchangers
– Direct Fired Vessels z Gas Fired Jacketed Steam Kettles(Jacket Pressure less than 50 PSI)
z Additional Interpretation:
ͷ͵
– The code rules may not cover all designs & constructions procedures. z Such additional design & construction procedure may be adopted which are safe and acceptable.
– Field fabrication are acceptable. – Other standards for components are acceptable
z 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/ 2COS(SE- 0.6P) + CA
z Stress Calculation UNDER INTERNAL PRESSURE, CYLINDRICAL SHELL: Circumferential stress:
ͷͶ
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 tCOS)/2Et COS Sl =P (Di – 0.8tCOS)/4Et COS
ͷͷ
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
ͷ
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.
ͷ
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]
ͷͺ
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
Type
Minimum Alert Criteria
"Stress Tool" "Model"
Safety Factor
7.13
None
"Stress Tool" "Model"
Safety Margin 6.13
None
Scope
Convergence tracking not enabled.
2.3.3. Shear Stress Safety Table 3.3.3.1. Definition Name
Shear Limit
Shear Factor
ͷͻ
"Stress Tool 2" Yield strength per material. 0.5 Table 3.3.3.2. Results Name
Type
Minimum Alert Criteria
"Stress Tool 2" "Model"
Safety Factor
6.69
None
"Stress Tool 2" "Model"
Safety Margin 5.69
None
Scope
Convergence tracking not enabled.
stress Figure A1.1. "Equivalent Stress" Contours
Ͳ
Scenario 1 Figures deformation Figure A1.2. "Total Deformation" Contours
ͳ
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
ʹ
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
͵
Ductility Exponent
-0.47
Cyclic Strength Coefficient
1.0×109 Pa
Cyclic Strain Hardening Exponent
0.2
Ͷ
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
ͷ
Contents x
x
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
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
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
ͺ
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
Maximum Shear Stress Total Deformation
1.6131e+006 Pa 1.6963e+007 Pa
Solution
>
Equivalent
0. m 4.1032e-005 m
Stress
>
2 Figure
ͻ
FIGURE Model > Static Structural maximum shear stress
>
Solution
>
Maximum
Shear
Stress
>
3 Figure
Ͳ
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
ͳ
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
ʹ
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
͵
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
Ͷ
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
ͷ
Contents x Model o
Geometry
FATIGUEANALYSIS o
Mesh
o
Static Structural
Analysis Settings
Loads
Solution
Solution Information
Results
Max Equivalent Stress
Max Shear Stress
o
Results
Fatigue Tool
Results
Result Charts
goodman stress life rl
x
Results
Results
Material Data
Structural Steel 2
Units TABLE 1 Unit System
Metric (m, kg, N, °C, s, V, A)
Angle
Degrees
Rotational Velocity rad/s
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
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
Moment of Inertia Ip2
522.8 kg·m²
Moment of Inertia Ip3
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
ͺ
• 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
ͻ
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
ͺͲ
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
ͺͳ
Newton-Raphson Residuals 0 Update Interval
2.5 s
Display Points
All
TABLE Model > Static Structural > Solution > Results Object Name
Equivalent Stress
State
Solved
Maximum Shear Stress Total Deformation
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
ͺʹ
Geometry
All Bodies
Definition Type
Safety Factor Safety Margin
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
Safety Factor Safety Margin
State
Solved
Scope Geometry
All Bodies
Definition Type
Safety Factor Safety Margin
Display Time
End Time
Results Minimum
3.537
2.537
Information Time
1. s
ͺ͵
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 Type History
History Data Data C:\Program
Files\Ansys
Inc\v110\AISOL\CommonFiles\Language\en-
Location
us\EngineeringData\Load Histories\sampleHistory2.dat
Scale Factor
5.e-003
Definition Display Time
End Time
Options Analysis Type
Stress Life
Mean Stress Theory Goodman Stress Component
Equivalent (Von Mises)
Bin Size
32
Use Quick Rainflow Counting Infinite Life Maximum
Yes 1.e+009 cycles
Data
Points To Plot
5000.
Life Units Units Name
cycles
1 block is equal to
1.e+006 cycles
Non-constant amplitude, Proportional Loading
ͺͶ
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
ͺͷ
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
ͺ
TABLE Model > Static Structural > Solution > Fatigue Tool > Results
Object Name Life State
Safety Factor Damage
Solved
Scope
Geometry
All Bodies
Definition
Type
Life
Design Life
Safety Factor Damage 1.e+009 cycles
Results
Minimum
2.e+007 cycles 0.
Maximum
50.
TABLE Model > Static Structural > Solution > Fatigue Tool > Result Charts
ͺ
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.
ͺͺ
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.
ͺͻ
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
ͻͲ
Stress Component
Equivalent (Von Mises)
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.
ͻͳ
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
ͻʹ
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
ͻ͵
Results
Minimum
1.e+012 cycles
Maximum
8.895
4.7782 Pa
1.e-003
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
ͻͶ
FIGURE Structural Steel 2 > Alternating Stress
TABLE Structural Steel 2 > Alternating Stress > Property Attributes
Interpolation
Log-Log
Mean Curve Type Mean Stress
ͻͷ
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
ͻ
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
ͻ
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
ͻͺ
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
ͻͻ
2. Mesh Report Table 2. Mesh Information for windanalysiscfx11_001
Domain
Nodes
Elements
pressurevessel
7338
28308
Figure 3. streamline and pressure representation
ͳͲͲ
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
ͳͲͳ
4. Solution Report Table 5. Boundary Flows for windanalysiscfx11_001
Location
Type
Mass Flow
Momentum X
Y
Z
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
8.1929e+03
-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.
ͳͲʹ
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.
ͳͲ͵
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.
ͳͲͶ
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.
ͳͲͷ
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.
ͳͲ
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
ͳͲ
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
ͳͲͺ
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.
ͳͲͻ
Appendix
ͳͳͲ
ͳͳͳ
ͳͳʹ
ͳͳ͵
¾ BIBLOGRAPHY ¾ Dennis Moss ¾ Hiadri Farzdak ¾ C.S Sharma ¾ Somnath chatopadhay
For Ansys : Tutorials of cfx 11.0
ͳͳͶ
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