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.
IMPORTANCE OF PIPE STRESS ANALYSIS
Uniform Piping Layout
Support Locations
Calculation of Nozzle Loadings,Support
Loadings,Stress,Displacement,Forces,Moments.
OBJECTIVES
What is STRESS ANALYSIS:
It provides the necessary technique for
Engineers to design piping systems without
overstressing & overloading the piping
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
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:
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
STRESS ANALYSIS FLOW CHART
Preparation of Critical Line List
Documents
(Isometrics)
Generating Reports
Analysis(Stress,Loads,Displacement)
Run,Checking the Errors & Warnings
Inputs in the Software
Pipe Stress Analysis(Software)
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)
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
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
STATIC ANALYSIS
Stress Reports
Restraint Summary Reports
Displacement Reports
Selection of Supports
DYNAMIC ANALYSIS
Natural Frequency Calculation
Harmonic Analysis
Response Spectrum Analysis
SLUG FLOW ANALYSIS
STRESS CATEGORIES
Primary Stress
Secondary Stress
PRIMARY
1.Sustained External
forces
& moments
2.Prevent plastic
deformation & bursting
STRESS CATEGORIES
SECONDARY
1. Local yielding
and minor distortion
can satisfy the
conditions which
caused
the stress to occur.
2.Thermal stress
PEAK
1.The additional stresses
due to stress
intensification in
highly localized area.
2.Stress due to notch effect
(Stress concentration)
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
F
7000 and less
1.0 (20Years)
7000 to 14000
0.9
14000 to 22000
0.8
22000 to 45000
0.7
45000 to 100000
0.6
Classification of Loads
Primary Loads
1.Sustained Loads(Pressure & Weight)
2.Occasional Loads(Earthquake & wind)
Expansion Loads(Displacement,Thermal
Expansion,Seismic Anchor
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)
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
Tear Away Indicator (double-click
anywhere in the box to activate)
Aux Screen Selector (Not tearable, but left-clicking and dragging will alter the order. Order change is not persistent)
Thumbtack for input pane.
Clicking will scroll the input into the frame, giving more space for the plot.
Input pane caption bar. Double-clicking will float the pane for “CAESAR II Classic Mode”
Toolbar
customization drop-down
CAESAR II 5.00 Interface
Navigation buttons – First, previous, next, lastDuplicate last element
These buttons…
…toggle these for each selected item(use the Selection Operator or right-click on something on the plot
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
–
Design-your-own spreadsheet with
“tearables”
“Mini-spreadsheet”, containing only key data.
CAESAR II 5.00 Interface
–
Graphic editing
Select element and choose operation…
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
–
Graphic editing
Add restraints (or any other
CAESAR II 5.00 Interface
Navigation buttons – First, previous, next, lastDuplicate last element
These buttons…
…toggle these for each selected item(use the Selection Operator or right-click on something on the plot
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
–
Design-your-own spreadsheet with
“tearables”
“Mini-spreadsheet”, containing only key data.
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
–
Graphic editing
Select element and choose operation…
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
–
Graphic editing
Add restraints (or any other
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
CAESAR II 5.00 Interface
–
Interactive error checking
Activate Error Checker
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.)
Summary from Error Check (only updates when error checking is complete)
Input/Error selector (holding left button and dragging will detach windows)