piping stress training

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CAESAR II 5.1 Training Vivek Paul Engineer (Tech.) KLG SYSTEL LTD

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Page 1: Piping Stress Training

CAESAR II 5.1 Training

Vivek Paul

Engineer (Tech.)

KLG SYSTEL LTD

Page 2: Piping Stress Training

AGENDA

Introduction to CAESAR II & Basic theories Data Inputting Usage of various spread sheets Modeling of piping system

– Modeling Miters– Reducers

Nozzle/Vessel Junction through C-nodes Rigid Elements Bellows Cold Springs Expansion Loop Hangers Static analysis along with wind loads Combining Load Cases as per codes Various Graphics Outputs Isometric generation Combining Dynamic Load as per code requirement Creating various reports (WRC 297, Loads on pumps compressors, Exchangers) Processing the result

Page 3: Piping Stress Training

Introduction to Pipe stress analysis

In order to properly design a piping system, the engineer must understand both a system behavior under potential loading as well as the regulatory requirements imposed upon it by governing codes.

System behavior can be quantified through the aggregate values of numerous physical parameter like acceleration, velocities, displacements, internal forces and moments, stress, and external reaction developed, under applied loads. Allowable value for each of them are set after review of appropriate failure criteria for the system. System response and failure criteria are dependent on type of loading which can be classified by Primary Vs Secondary,

Sustained Vs Occasional, Static Vs Dynamic.

Page 4: Piping Stress Training

Why do we perform Pipe Stress Analysis

In Order to Keep stress in the Pipe & Fittings within code allowable levels.

In Order to keep Nozzle loading on attached equipment with in allowable of manufactures or recognized standard (NEMA SM23, API610, API617)

In Order to calculate design loads for sizing supports and restraints. In order to determine piping displacement for interference checks In order to solve dynamic problems in piping, such as those due to

mechanical vibration, fluid hammer, pulsation, transient flow and relief valve discharge

In order to help optimize piping design.

Page 5: Piping Stress Training

Pipe Stress Design Data

Design Data typically required for pipe stress analysis consist of Pipe Material & Size Operating Parameter

Temperature Pressure

Fluid Contains Code Stress Allowable Loading Parameters

Insulation Weight External Equipment Movement

Wind & Earthquake criteria

Page 6: Piping Stress Training

But we can go ahead only when you know this

Basic Piping Isometric reading & Generation Piping components

Page 7: Piping Stress Training

CAESAR II Main Menu

After starting CAESAR II Main Menu appears, it is recommended to kept this Window minimum as this will used only for accessing toolbar and command

Page 8: Piping Stress Training

File Menu

Set Default Data Directory– Tool to set Default project directory where all the files of particular projects will be

saved. Selection of data directory is very important as configuration, units, data files found in the directory will be considered to be a Local to that Job

New– For creating a new Piping or structural files

Open– Open an existing piping or structural Job

Clean up (Delete) Files– Enables user to delete unwanted scratch, listing, input or output files to retain more

hard disk space Recent Piping or Recent structural Files

– Display the four most recently used Piping or structural files Exit

– Closes CAESAR II Application

Page 9: Piping Stress Training

Input Menu

Piping Inputs CAESAR II Piping Model

Underground Converts Existing Piping Model to buried piping

Structural Steel Input CAESAR II Structural Model

Page 10: Piping Stress Training

Piping Input

Data Fields Node Numbers Element Lengths Element Direction Cosines Pipe Section Properties Operating Conditions: Temperature & Pressure Special Element Information Boundary Conditions Loading Conditions Piping Material Material Elastic Properties Densities

Spreadsheet Overview Undo/Redo Customize Toolbar

Page 11: Piping Stress Training

Necessity of Node Points

Node points are required at any location where it is necessary to provide information to, or obtain information from pipe stress software. Node points are required to:

Define geometry System Start, End, Direction Changes, Intersection etc

Observing Changes in operating condition System start, isolation or pressure reduction valve

Define element stiffness parameters Change in pipe cross section or material, rigid element or expansion Joints

Defining Boundary conditions Restraints and imposed displacements

Specify Mass points Refinement of mass modal

Note Loading condition Insulation Weight Imposed Forces Earthquake g-factor Response spectra Wind Exposure & Snow

Retrieve information from the stress analysis Stress at piping mid spans Displacements at wall penetration

Page 12: Piping Stress Training

Node Numbers

The FROM & TO node number defines the starting & end of the element respectively. Node numbers must be numeric, ranging from 1 to 32000. Normally, the FROM node number is "duplicated forward" by CAESAR II from the preceding element

Page 13: Piping Stress Training

NAME

This check box is used to assign non-numeric names to node points. Double-clicking this check box activates an auxiliary spreadsheet where names, of up to 10 characters, can be assigned to the FROM and/or TO nodes. These names will show up in place of the node numbers in graphic plots and reports

Page 14: Piping Stress Training

ELEMENT LENGTH

Length of element is entered as a delta dimension which are the measurement along X, Y and Z axis. one or more entries must be made except Zero length Expansion Joints.

Note: 3-2, -2, 2-3-3/16 are the acceptable format for Feet & Inches Entries. Simple forms of addition, multiplication, and division

may be used as well as exponential format.

Page 15: Piping Stress Training

Please Answer

6.3 = ? 6-10 =? 6-10-1/4 =? 6-10-1/4+3-7 =? 6.3*12 =?

Page 16: Piping Stress Training

ELEMENT DIRECTION COSINE

Direction Vector or direction

cosine which define the center

line of the element.

Page 17: Piping Stress Training

ELEMENT OFFSET

Thermal expansion will be “0” for the offset portion of an element. No element flexibility will be generated for offset part at the time of analysis.

Page 18: Piping Stress Training

PIPE SECTION DATA

Diameter Wt / Sch +Mill Tol %; WI -Mill Tol % Seam-Welded Corrosion Insul Thk

Page 19: Piping Stress Training

DIAMETER

The Diameter field is used to specify the pipe diameter. Normally, the nominal diameter is entered, and CAESAR II converts it to the actual outer diameter necessary for the analysis. There are two ways to prevent this conversion: use a modified UNITS file with the Nominal Pipe Schedules turned off, or enter diameters whose values are off slightly from a nominal size (in English units the tolerance on diameter is 0.04 in.)

ANSI Nominal Pipe ODs, in inches (file ap. bin) ½ ¾ 1 1 ½ 2 2 ½ 3 3 ½ 4 5 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 42

JIS Nominal Pipe ODs, in millimeters (file jp. bin) 15 20 25 32 40 50 65 80 90 100 125 150 200 250 300 350 400 450 500 550 600 650

DIN Nominal Pipe ODs, in millimeters (file dp. bin) 15 20 25 32 40 50 65 80 100 125 150 200 250 300 350 400 500 600 700 800 900 1000

1200 1400 1600 1800 2000 2200

Page 20: Piping Stress Training

Wt / Sch

tm = t + c

tm = minimum wall thickness, in.

t = minimum wall thickness required for pressure, in

C= sum of allowances for thread or groove depth, corrosion, erosion and manufacturer’s tolerance, in

Page 21: Piping Stress Training

Wt / Sch

The Wall Thickness/Schedule field is used to specify the thickness of the pipe. Normal input consists of a schedule indicator (such as S, XS, or 40), which will be converted to the proper wall thickness by CAESAR II. If actual thickness is entered, CAESAR II will accept it as entered. Available schedule indicators are determined by the active piping specification, set via the configuration program. The available schedules are listed below.

ANSI B36.10 Steel Nominal Wall Thickness Designation: S - Standard XS - Extra Strong XXS - Double Extra Strong

ANSI B36.10 Steel Pipe Numbers:10 20 30 40 60 80 100 120 140 160

ANSI B36.19 Stainless Steel Schedules:5S 10S 40S 80S

JIS PIPE SCHEDULES 1990 Steel Schedules:

10 20 30 40 60 80 100 120 140 160 1990 Stainless Steel Schedules:

5S 10S 40S DIN PIPE SCHEDULES

Page 22: Piping Stress Training

+Mill Tol %; Wl

The Positive Mill Tolerance is only enabled when IGE/TD/12 is active, and is used when the Base Stress/Flexibility On directive of the Special Execution Options is set to Plus Mill Tolerance. In that case, piping stiffness and section modulus is based on the nominal wall thickness, increased by this percentage. The user may change this value on an element-by-element basis.

If the B31.3 piping code is activated, this field is used to specify the "weld strength reduction factor" (Wl), to be used in the minimum wall calculation for straight pipe.

Page 23: Piping Stress Training

-Mill Tol %

The Negative Mill Tolerance is read in from the configuration file for use in minimum wall thickness calculations. Also, for IGE/TD/12, this value is used when the Base Stress/Flexibility On directive of the Special Execution Options is set to Plus Mill Tolerance. In that case, piping stiffness and section modulus is based on the nominal wall thickness, decreased by this percentage. The user may change this value on an element-by-element basis.

Page 24: Piping Stress Training

SEAM-WELDED

If the B31.3 piping code is active, the "seam-welded" check box is used to activate the Wl field. The Wl field is the "weld strength reduction factor" used to determine the minimum wall thickness of the element.

Page 25: Piping Stress Training

CORROSION

Enter the corrosion allowance to be used order to calculate a reduced section modulus. A "setup file" directive is available to consider all stress cases as corroded

Page 26: Piping Stress Training

Insul Thk ()

Enter the thickness of the insulation to be applied to the piping. Insulation applied to the outside of the pipe will be included in the dead weight of the system, and in the projected pipe area used for wind load computations. If a negative value is entered for the insulation thickness, the program will model refractory lined pipe. The thickness will be assumed to be the thickness of the refractory, inside the pipe.

Page 27: Piping Stress Training

OPERATING CONDITION

Temperature Pressure

Page 28: Piping Stress Training

TEMPERATURE

CAESAR II uses these temperatures to obtain the thermal strain and allowable stresses for the element from the Material Database. Thermal strain can be specified directly as well. thermal strain have absolute values on the order of 0.002 and are unit less. CAESAR II uses an ambient temperature of 70 F, unless changed using the special execution parameter option.

There are nine temperature fields, to allow up to nine different operating cases. Temperature values are checked (by the error checker) to insure they are within the code allowed ranges. Users can exceed the code ranges by entering the expansion coefficient in the temperature field in units of length/length. The expansion coefficient can be a useful method of modeling cold spring effects. Also when material 21(user-defined material) enter temperature *expansion coefficient as in the example below.

Values entered in the temperature field whose absolute values are less than the Alpha Tolerance are taken to be thermal expansion coefficients, where the Alpha Tolerance is a configuration file parameter and is taken to be 0.05 by default. For example, if the user wanted to enter the thermal expansion coefficient equivalent to 11.37in./100ft., the calculation would be:

11.37in./100ft. * 1 ft./ 12in. = .009475 in./in.

This would be entered into the appropriate Temperature field.

Page 29: Piping Stress Training

PRESSURE

There are ten pressure fields, to allow up to nine operating, and one hydro test, pressure cases. When multiple pressures are entered, the user should be particularly careful with the set up of the analysis load cases, and should inspect CAESAR II's recommendations carefully before proceeding.

Access to operating pressures 3 through 9 is granted through the Extended Operating Conditions input screen, accessible via the Ellipses Dots button directly to the right of the standard Temperature and Pressure input fields. This dialog box may be retained open or closed at the convenience of the user.

Entering a value in the Hydro Press field signals CAESAR II to recommend a Hydro test load case.

Page 30: Piping Stress Training

COMPONENT INFORMATION

Bend Rigid Element Expansion Joint Reducer SIF & Tees

Page 31: Piping Stress Training

Bend

If element described by input sheet ends with bend, elbow, mitered joint bend check box to be checked.

– Bend angle is always defined by element entering and leaving the bend.– By default the bend radius (Basically it is long radius) is 1.5 times of Pipe nominal

diameter.– CAESAR II automatically creates two nodes on bend at 0 degree location and bend

mid point. (Bend)– TO node of the element entering the bend located at far point on the bend. This is for

stress and displacement output. Far point is the weld line of bend and adjacent to element leaving the bend.

– 0 degree Node will not be created if Total length of element specified is equal to R tan(β/2)

– Nodes on bend curvature can not be place closer together then specified angle in CONFIG/SETUP File.

– Minimum and Maximum bend angle also need to be specified in CONFIG/SETUP File only.

Page 32: Piping Stress Training

BEND- TYPE

For most codes, this refers to the number of attached flanges, and can be selected from the drop list. If there are no flanges on the bend then leave the Type field blank. It has been seen that elbows tends to ovalize during bending.

– Single & Double flanged bends can be enter by entering 1 or 2 respectively for the type.

– When specifying single flanged bends it does not matter which end of bend the flange is installed

– If user wants to include the weight of rigid flange then he has to put rigid element with equal length of flange on desired side of bend.

Page 33: Piping Stress Training

Some practice

45 degree elbow U type/180° return bend Circular ring

Page 34: Piping Stress Training

Mitered Bends

A Miter Joint is a change in pipe direction through proper cutting and welding of straight pipe.

Closely Spaced Widely Spaced

– R = r[1 + cotθ] 2

Page 35: Piping Stress Training

FITTING THICKNESS

Thickness of the bend will be changed without affecting preceding & following pipe

CAESAR applies this change on current bend only

As per B31 Stress at elbow are calculated on basis of section modulus of matching pipe however the stress intensification factor & Flexibility factor for bend is based on wall thickness of elbow.

Page 36: Piping Stress Training

K-FACTOR

K-Factor shows flexibility of bend w.r.t same length of pipe. If K-factor value is 1.5, it means bend is 1.5 times as flexible as same length of pipe. Bend flexibility factor are calculated as per code but user can overwrite it.

Page 37: Piping Stress Training

RESTRAINTS

Restraints we are using to provide boundary condition. Anchor Double Acting & Single Acting – Transitional/Rotational Guide LIM XSNB, YSNB, ZSNB X2, Y2, Z2 K2 XSPR, YSPR, ZSPR X (cosx, cosy, cosz) or X (vecx, vecy, vecz) RX (cosx, cosy, cosz) or RX (vecx, vecy, vecz) XROD, YROD, ZROD

Page 38: Piping Stress Training

ANCHORS

Anchors is an rigid element hence displace should not be defined at an anchor node.

For anchors with displacement following point should be considered

Enter only displacement for the node Do not apply any restraint or anchors at the node to

be displaced All 6 degree of freedom at the node should be

defined. Leaving the displacement field blank will default to

zero.

Page 39: Piping Stress Training

DOUBLE ACTING RESTRAINT

Transitional Rotational

Page 40: Piping Stress Training

SINGLE ACTING RESTRAINT

Always gives information about Free Axis Can be defined along +ve, -ve & skewed axis If CNode left blank then the restrained node

is connected via the restraint stiffness to a rigid point in space. If the CNode is entered then the restrained node is connected via the restrained stiffness to the connecting node

Page 41: Piping Stress Training

GUIDE Double Acting

Guided pipe in the horizontal or skewed direction will have a single restraint, acting in the horizontal plane, orthogonal to the axis of the pipe.

A guided vertical pipe will have both X & Z direction supports

Page 42: Piping Stress Training

DIRECTIONAL LIMIT STOPS

Limit stops are single pr double acting restraint whose line of action is along the axis of the pipe, these restraint can have gaps which permits free movement along the restraint line of action.– Directional Limit stop with gap– Two limit stops acting in opposite direction

Page 43: Piping Stress Training

WINDOW

Equal leg windows are modeled using two double-acting restraints with gaps orthogonal to the pipe axis

Unequal leg windows are modeled using four single-acting restraints with orthogonal to the pipe axis

Page 44: Piping Stress Training

ROTATIONAL DIRECTIONAL RESTRAINT

These restraints can be considered specialty items and are typically only used in sophisticated expansion joints or hinge models.– Bidirectional rotational restraint with Gap– Hinged Assembly with directional rotational

restraint

Page 45: Piping Stress Training

Single-Directional restraint with predefined displacement

Page 46: Piping Stress Training

Single-Directional restraint and Guide with Gap and Predefined Displacement

Page 47: Piping Stress Training

RESTRAINT ON BEND AT 45 DEGREES

Page 48: Piping Stress Training

RESTRAINT ON BEND AT 30 & 60 DEG

Page 49: Piping Stress Training

Vertical Dummy Leg On Bends

Page 50: Piping Stress Training

Reducer

Page 51: Piping Stress Training

Load Case Editor

Scale Factor for load components When building load cases, load components (W,T1,D1,WIND1

etc.) may be preceded by scale factors such as 2.0, -, 0.5 etc. One loading is multiple of other Loading may be directionally reversible (i.e. wind or earthquake), “+”

& “-” will be used to specifydirection

1.5W+1.1T1+1.1D1+1.25Wind1

Page 52: Piping Stress Training

User defined load case names

Note: Load case name should not exceed 132 characters

Page 53: Piping Stress Training

User-controlled combination methods

Algebraic Scalar SRSS Abs Max Min Sign Max Sign Min

Page 54: Piping Stress Training

Algebraic

This method combines the displacement, forces, moments, restraint loads and pressures of the designated load cases in an algebraic (vectorial) manner. The resultant forces, moments, and pressures are then used (along with the SIFs and element cross-sectional parameters) to calculate the piping stresses. New combination cases automatically default to this method, unless specifically designated by user.

Page 55: Piping Stress Training

SCALAR

This method combines the displacement, forces, moments, restraint loads and stresses of the designated load cases in a scalar manner but retaining consideration of sign. This method might typically be used when adding “plus” or “minus” seismic loads to an operating case, or when doing an occasional stress code check.

Page 56: Piping Stress Training

SRSS

This method combines the displacements, forces, moments, restraint loads and stresses of defined load cases in Square root of the sum of the squares manner; however due to squaring “-ve” vs. “+ve” values yield no difference. This load typically used when combining seismic loads acting in orthogonal directions.

Page 57: Piping Stress Training

Abs

This method combines the displacements, forces, moments, restraint loads and stresses of defined load cases in Absolute manner; however due absolute values used by the combination method “-ve” & “+ve” values yield no difference in the results. This load typically used when combining loads acting in orthogonal directions. This method may be used when doing an occasional stress code check (i.e. absolute summation of the sustained and occasional stresses)

Page 58: Piping Stress Training

MAX

For each result value, this method selects the displacement, force, moments, restraints load, and stress having the largest absolute value from the designated load cases; so no actual combination, per se, takes place. Load case results are multiplied by any scale factor prior to doing the selection of MAXIMA. This method is typically used when design case (worst loads, stress etc.) from number of loads.

Page 59: Piping Stress Training

MIN

For each result value, this method selects the displacement, force, moments, restraints load, and stress having the smallest absolute value from the designated load cases; so no actual combination, per se, takes place. Load case results are multiplied by any scale factor prior to doing the selection of MINIMA.

Page 60: Piping Stress Training

Sign MAX

For each result value, this method selects the displacement, force, moments, restraints load, and stress having the largest actual value considering the sign from the designated load cases; so no actual combination, per se, takes place. Load case results are multiplied by any scale factor prior to doing the selection of MAXIMA. This method is typically used in conjunction with the SignMin method to find the design range for each value (i.e. maximum positive and maximum negative restraint loads)

Page 61: Piping Stress Training

SignMin

For each result value, this method selects the displacement, force, moments, restraints load, and stress having the Smallest actual value considering the sign from the designated load cases; so no actual combination, per se, takes place. Load case results are multiplied by any scale factor prior to doing the selection of MAXIMA. This method is typically used in conjunction with the SignMax method to find the design range for each value (i.e. maximum positive and maximum negative restraint loads)