PIPE STRESS ANALYSIS
STRESS ANALYSIS
INTRODUCTION OBJECTIVES PURPOSE REQUIREMENTS PROCEDURE CONCLUSION
INTRODUCTION WHAT IS STRESS?
Stress=Applied force/Cross Sectional Area Strain=Change in dimensions/Original dimensions. Stress of a material is the internal resistance per unit area to the deformation caused by applied load.
STRESS-STRAIN CURVE
IMPORTANCE OF PIPE STRESS ANALYSIS
Uniform Piping Layout Support Locations Calculation of Nozzle Loadings,Support Loadings,Stress,Displacement,Forces,Moments. Pipe Flexibility
OBJECTIVES
What is STRESS ANALYSIS: It provides the necessary technique for Engineers to design piping systems without overstressing & overloading the piping components & connected equipment.
OBJECTIVES: The Layout & Design of Piping shall be made to prevent the followings:
1.Piping Stress in excess of those permitted by the Codes 2.Leakage at Joints 3.Excessive forces & moments on connected Equipments. 4. Excessive Stresses in the piping supporting elements 5. Excessive with thermal Expansion & Contraction
FORMAL ANALYSIS IS NOT REQUIRED
Duplicates or Replaces without significance change,a system operating with a successful service records. Can readily be judged adequate by comparison with previously Analyzed systems. Thumb Rule: Dy/(L-U)²<=K1 D=Outside Diameter of the Pipe in mm y =Resultant of total displacement Strains in mm L=Developed length of Piping between Anchors in m U=Anchor distance,straight line between Anchors in m K1=208000 Sa/Ea in (mm/m)² Sa=Allowable Displacement Stress in MPa Ea=Reference Modulus of Elasticity in MPa
PURPOSE
Safety of Piping & Piping Components Safety of Connected Equipment & Supporting Structure Piping Deflections are within the Allowable limits
STRESS ANALYSIS FLOW CHART Preparation of Critical Line List
Documents(Isometrics) Pipe Stress Analysis(Software) Inputs in the Software Run,Checking the Errors & Warnings Analysis(Stress,Loads,Displacement) Generating Reports
REQUIRMENTS
CAESAR-II,AUTO PIPE,PIPE FLEX,CAE PIPE(Stress Analysis Software) Critical Line List GADs(General Arrangement Drawing) P & Ids(Process & Instrument Drawing) Isometrics PMS (Piping Material Specification) Others(Dimensions,Valve Weights)
PROCEDURE
MODELLING STRESS
ANALYSIS STRESS REPORTS
STRESS ANALYSIS Static
Analysis Dynamic Analysis Slug Flow Analysis
STATIC ANALYSIS
Buried(Underground) Flange Leakage Test API 610(Centrifugal Pumps) API 617(Centrifugal Compressor) API 661(Air-Cooled Heat Exchangers) API 560(Fired Heaters for general Refining Services)
STATIC ANALYSIS
WRC 107/297(Vessel Stress & Nozzle Loadings) B 31.G(Remaining Strength of Corroded Pipelines) Expansion Joint Rating AISC(American Institute of Steel Construction) NEMA SM23(Turbines) SIFs Intersections & SIFs Bends HEI Standards(Rotating Equipment Nozzle)
STATIC ANALYSIS
Stress Reports Restraint Summary Reports Displacement Reports Selection of Supports Wind,Wave,Earthquake Consideration
DYNAMIC ANALYSIS
Natural Frequency Calculation Harmonic Analysis Response Spectrum Analysis Time History Analysis
SLUG FLOW ANALYSIS
Spectrum Method
STRESS CATEGORIES
Primary Stress Secondary Stress Peak Stress
STRESS CATEGORIES PRIMARY 1.Sustained External forces & moments 2.Prevent plastic deformation & bursting
SECONDARY
PEAK
1. Local yielding 1.The additional stresses and minor distortion due to stress can satisfy the intensification in conditions which highly localized area. caused 2.Stress due to notch effect the stress to occur. (Stress concentration) 2.Thermal stress
ALLOWABLE STRESS Smax=1.6(Sc+ Sh) Sa= F(1.25 Sc + 0.25 Sh) Sa=Allowable Stress Sc=Cold Allowable Stress Sh=Hot Allowable Stress F=Stress Range Reduction factor for Cyclic Conditions CYCLES 7000 and less 7000 to 14000 14000 to 22000 22000 to 45000 45000 to 100000 100000 and over
F 1.0 (20Years) 0.9 0.8 0.7 0.6 0.5
Classification of Loads
Primary Loads 1.Sustained Loads(Pressure & Weight) 2.Occasional Loads(Earthquake & wind) Expansion Loads(Displacement,Thermal Expansion,Seismic Anchor movements,Building Settlement)
CODES
B31.1(Power Piping) B31.3(Process Piping) Petroleum Plant Refineries Plant Chemical Plant Pharmaceutical Plant Textile Plant Paper Plant Semiconductor & Cryogenic Plant
B31.4(Pipeline Transportation) B31.5(Refrigeration Piping) B31.8(Gas Transmission & Distribution System)
SUPPORTS
Restraints Guide Limit Stops Anchor Hanger Trunnion
PIPE FLEXIBILITY
The Purpose of Piping Flexibility Analysis is to produce a Piping Layout that cause neither excessive stresses nor excessive end reactions.
PIPE FLEXIBILITY Parameters to be Considered for Flexibility Analysis:• The Appropriate Code that applies to the system. • The Design Pressure and Temperature. • The Type of material. • The Pipe Size and Wall Thickness of each Pipe Component. • The Piping Geometry including movements of Anchors and Restraints. • The Allowable Stresses for the design conditions set by appropriate Code. • Limitations of forces and moments on Equipment Nozzles set by API, NEMA or the equipment manufacturers.
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface Toolbar customization drop-down
Thumbtack for input pane. Clicking will scroll the input into the frame, giving more space for the plot. Tear Away Indicator (double-click anywhere in the box to activate)
Input pane caption bar. Doubleclicking will float the pane for “CAESAR II Classic Mode”
Aux Screen Selector (Not tearable, but leftclicking and dragging will alter the order. Order change is not persistent)
CAESAR II 5.00 Interface These buttons…
…toggle these for each selected item(use the Selection Operator or rightclick on something on the plot
Navigation buttons – First, previous, next, last
Perform the “List/Block” operations
Duplicate last element
CAESAR II 5.00 Interface
Drop down arrow allows selective opening or closing of individual lists
Individual lists may be opened, closed, or undocked in their own windows.
CAESAR II 5.00 Interface
– Design-your-own spreadsheet with
“tearables”
CAESAR II 5.00 Interface
“Mini-spreadsheet”, containing only key data.
– Design-your-own spreadsheet with
“tearables”
CAESAR II 5.00 Interface
Select element and choose operation…
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
Add restraints (or any other auxiliaries).
– Graphic editing
CAESAR II 5.00 Interface These buttons…
…toggle these for each selected item(use the Selection Operator or rightclick on something on the plot
Navigation buttons – First, previous, next, last
Perform the “List/Block” operations
Duplicate last element
CAESAR II 5.00 Interface
Drop down arrow allows selective opening or closing of individual lists
Individual lists may be opened, closed, or undocked in their own windows.
CAESAR II 5.00 Interface
– Design-your-own spreadsheet with
“tearables”
CAESAR II 5.00 Interface
“Mini-spreadsheet”, containing only key data.
– Design-your-own spreadsheet with
“tearables”
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
Select element and choose operation…
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
Add restraints (or any other auxiliaries).
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Graphic editing
CAESAR II 5.00 Interface
– Walk-through
CAESAR II 5.00 Interface
– Interactive error checking
Activate Error Checker
Closes Error Check output (re-running will re-open)
CAESAR II 5.00 Interface Summary from Error Check (only updates when error checking is complete)
Output from Error Check (selecting each line with a node number will highlight that element on the plot and switch the piping input screen (or floating parts) to the appropriate page). Errors are displayed in red, Warnings are green and Notes are blue. Clicking on a column header will sort based on the data in that column.)
Input/Error selector (holding left button and dragging will detach windows)
– Interactive error checking
CAESAR II 5.00 Interface
– Interactive error checking
Automatic Generation of Stress Isometrics
Isos developed using “de-facto standard” Isogen
Piping Code Changes
– New codes – EN-13480, GPTC/192, Z662
Ch 11
Piping Code Changes
– MAJOR revisions – B31.3, B31.8
Piping Code Changes
– “Minor” revisions – B31.1, B31.5, B31.11, ASME NC, ASME
ND, CODETI, TBK 5-6, API-610
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
MODELLING
CONCLUSION
Pipe Stress Analysis is Very important & Useful for Piping in Petroleum Refineries,Chemical,Pharmaceutical, Textile, Paper, Semiconductor & Cryogenic Plants as also in Off Shore & On Shore for Safe Working.
THANK YOU FOR YOUR PATIENCE
Prepared By BABASHIS RAYGURU.
