Post on 03-Apr-2018
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M
echan
ical
En
gineering
News
FOR THE POWER,
PROCESS AND
RELATED INDUSTRIES
The COADE Mechanical Engineering
News Bulletin is published twice a yearfrom the COADE offices in Houston,Texas. The Bulletin is intended to provideinformation about software applicationsand development for MechanicalEngineers serving the power, process andrelated industries. Additionally, the Bulletinserves as the official notificationvehicle for software errors discovered inthose Mechanical Engineering programsoffered by COADE.
2001 COADE, Inc. All rights reserved.
V O L U M E 3 0 J A N U A R Y 2 0 0 1
Whats New at COADE
PVElite Version 4.10 New Features ............... 1
CAESAR II Version 4.30 New Features......... 4
TANK Version 2.20 Released ...................... 11
The New Pipe Stress Seminar Format......... 11
Technology You Can Use
Sustained Stresses ...................................... 12
Using the New CAESAR II Static Load Case
Builder ...................................................... 19
PC Hardware for the Engineering User
(Part 30) ................................................... 25
Program Specifications
CAESAR II Notices ...................................... 26
TANK Notices ............................................... 26
CodeCalc Notices ........................................ 27
PVElite Notices ............................................ 27
CAESAR IIVersion 4.30
New Features
>see story page 4
Sustained
Stresses
>see story page 12
Using the New
CAESAR II StaticLoad Case
Builder
>see story page 19
Article Here
PVElite Version 4.10 New Features(by: Scott Mayeux
PVElite Version 4.10 contains many new exciting additions. A brief list o
the enhancements is shown in the table below. This article will discuss a few
of these new features and how they may impact vessel designs.
ASME 2000 addenda has been incorporated
Provision to use the 1999 year material database
TEMA and ASME tubesheet programs updated to perform multiple load cases
Separate entry of m and y factors for partition gaskets
User bolt loads in the tubesheet programs
Simultaneous Corroded and UnCorroded thick expansion joint calculations
ASCE 98 wind code added
Rigging analysis with graphical results processor added
The input ( thicknesses, rings, repads ) can now be updated by the analysis
program
The 3-D viewer now has a transparency option
Ladder information is now collected
User time history input for IS-893 RSM
As always there have been changes to ASME VIII Division 1 and the materia
database(s). Typically, new materials are added and obsolescent materials are
withdrawn from the Code. In this revision to the program we have of course
updated the material tables and now offer the option of using the current (2000)
addenda, the pre-1999 addenda (lower allowable stresses) or the 1999 stress
tables. The option that allows this is found in theTools->Configurationdialog
Another major change was made to both the ASME and TEMA tubeshee
programs. ASME Appendix AA was modified substantially for 2000. The
new changes themselves do not typically generate answers that are significantly
different from the previous year addenda. While the alterations were being
I N T H I S I S S U E :
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made, we added new functionality in the way of multiple load cases.
If informed to do so, either of the ASME or TEMA tubesheet
programs can run up to 16 load cases for fixed tubesheet exchangers.
These load cases involve different combinations of temperature,
pressure (internal and external) as well as corrosion allowance. The
generated output for these 16 cases is reduced to a mere 2 or 3
pages. Previously, this could have generated up to 60 pages. Asample table of results and the dialog used to control the output is
shown below:
Fixed Tubesheet Required Thickness per TEMA 8th Edition:
Thickness Reqd ----- P r e s s u r e s Case Pass/
Case# Tbsht Extnsn Pt' Ps' PDif Type Fail----------------------------------------------------------------------1c 2.551 0.879 49.71 0.00 0.00 Fvs+Pt-Th+Ca Ok2c 0.850 0.879 0.00 -2.48 0.00 Ps+Fvt-Th+Ca Ok3c 2.610 0.879 49.71 -2.48 0.00 Ps+Pt-Th+Ca Fail4c 0.770 0.879 0.00 0.00 -0.48 Fvs+Fvt+Th+Ca Ok5c 2.550 0.879 49.71 0.00 -0.48 Fvs+Pt+Th+Ca Ok6c 0.850 0.879 0.00 -2.47 -0.48 Ps+Fvt+Th+Ca Ok7c 2.609 0.879 49.71 -2.47 -0.48 Ps+Pt+Th+Ca Fail8c 0.770 0.879 0.00 0.00 0.00 Fvs+Fvt-Th+Ca Ok1uc 1.662 0.879 19.81 0.00 0.00 Fvs+Pt-Th-Ca Ok2uc 1.279 0.879 0.00 13.43 0.00 Ps+Fvt-Th-Ca Ok3uc 1.662 0.879 19.81 13.43 0.00 Ps+Pt-Th-Ca Ok4uc 1.733 0.879 0.00 0.00 -49.37 Fvs+Fvt+Th-Ca Ok5uc 1.733 0.879 19.68 0.00 -49.37 Fvs+Pt+Th-Ca Ok6uc 1.954 0.879 0.00 13.35 -49.37 Ps+Fvt+Th-Ca Ok7uc 1.954 0.879 19.68 13.35 -49.37 Ps+Pt+Th-Ca Ok8uc 0.750 0.879 0.00 0.00 0.00 Fvs+Fvt-Th-Ca Ok----------------------------------------------------------------------Max: 2.610 0.879 in.
Given Tubesheet Thickness: 2.5625 in.
Note:Fvt,Fvs - User-defined Shell-side and Tube-side vacuum pressures or 0.0.
Ps, Pt - Shell-side and Tube-side Design Pressures.Th - With or Without Thermal Expansion.Ca - With or Without Corrosion Allowance.
Tube and Shell Stress Summary: Shell Stresses Tube Stresses Tube Loads Pass
Case# Ten Allwd Cmp Allwd Ten Allwd Cmp Allwd Ld Allwd Fail-1c 33 15900 0 -4968 10762 13500 0 -5458 1161 1020 Fail2c 0 15900 -290 -4968 1870 13500 0 -5458 202 1020 Ok3c 33 15900 -290 -4968 12633 13500 0 -5458 1363 1020 Fail4c 28 15900 0 -4968 0 13500 -116 -5287 0 1020 Ok5c 45 15900 0 -4968 10765 13500 -116 -5287 1162 1020 Fail6c 28 15900 -289 -4968 1870 13500 -116 -5287 202 1020 Ok7c 45 15900 -289 -4968 12634 13500 -116 -5287 1363 1020 Fail8c 0 15900 0 -4968 0 13500 0 -5458 0 1020 Ok
1uc 3389 15900 0 -5038 3467 13500 0 -5458 374 1020 Ok2uc 1507 15900 0 -5038 0 13500 -1975 -5458 213 1020 Ok3uc 4896 15900 0 -5038 3467 13500 -1975 -5458 374 1020 Ok4uc 2771 15900 0 -5038 0 13500 -11927 -5287 0 1020 Fail5uc 4473 15900 0 -5038 3436 13500 -11927 -5287 371 1020 Fail6uc 2771 15900 0 -5038 0 13500 -13885 -5287 211 1020 Fail7uc 4903 15900 0 0 3436 13500 -13885 -5287 371 1020 Fail8uc 0 15900 0 -5038 0 13500 0 -5458 0 1020 Ok-
MAX RATIO 0.308 0.058 0.936 2.627 1.337
Additionally, the thick expansion joint program can now a
accommodate calculations in both the corroded and uncorrod
conditions in the same run. The ability of the program to prov
this functionality will potentially reduce input errors.
Also in the Component Analysis program (CodeCalc), we ha
allowed the entry for separate m and Y factors as well and sketand column information for all components that have option
entries for partition gasket information. User defined bolt load d
is also available in the tubesheet modules.
In the main analysis section ofPVElite there have also been ma
changes. One time saving change is that after the analysis (in desi
mode) has changed any data values such as thicknesses, stiffeni
rings, basering data or reinforcing pad information, the input can
automatically updated by the program at the users request.
illustrate this, review the model below. We have requested t
program to add angle type stiffeners to this vessel.
After the program has generated the new input, it will ask f
confirmation to use the new data.
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After accepting the changes, here is how the model appears.
Other new items include the option of entering ladder data in the
platform dialog. As shown below, the 3-D graphics have also been
updated to draw the ladders. Note that the transparency option has
been turned on for the shell and cone elements.
Another major addition to this version is that the program can nowperform a rigging analysis. This is the computation of bending and
shear stresses in a vessel when it is being lifted from the horizonta
position. The rigging analysis requires that the location of the lugs
be entered in as well as the impact factor for lifting. The impac
factor accounts for how rough the vessel is lifted. This value
generally lies between 1 and 2, but values as high as 3.0 can be used
If the impact factor is less than 1.0 or the lug distances are not
defined, the program will not perform the analysis. The main
objective is to determine if the stress levels are excessive during
lifting. The program computes a combined bending plus shea
stress check. The result of this check should be less than or equal to
1.0. The result of a typical rigging analysis is shown below.
RIGGING ANALYSIS
Total weight of the vessel (No liquid) Twt 92238.39 lb.Impact weight multiplication factor Imp 1.50Design lifting weight, DWT = Imp * Twt 138357.58 lb.Elevation of the tail lug 0.50 ft.Elevation of the lifting lug 70.00 ft.Length of element used for the analysis, INC 1.00 ft.Overall height (node to node) 94.77 ft.Elevation of the vessel center of gravity 44.26 ft.
Design reaction force at the tail lug 51250.46 lb.Design reaction force at the lifting lug 87107.12 lb.
Critical values:Max stress Elevation Allowables
psi ft. psi|||Bending | -3772.13 | 30.38 | 14518.90 (UG-23)Shear | -470.55 | 69.95 | 11280.00 (0.4*Sy)|||
AISC Unity Check was 0.2600 at 29.44 ft. (must be
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The graph shown below depicts the combined bending plus shear
stress. The graph tool is invoked from the main screen after the
rigging results data file has been generated. The arrows on the
toolbar switch between the different graphs.
Another update to version 4.10 came in the form of the ASCE 98
wind design code. This code is nearly identical to its predecessor,
ASCE 95. However, the computation of the gust response factor
for both static and dynamic cases has been slightly altered. New
values of the dynamic gust factor have been found to be slightly
lower than those computed by the previous edition of ASCE. The
static gust factor is slightly higher than previous values.
There are several other enhancements to PVElite that have not beenmentioned here. The updates to the user guide will contain more
information. This product is scheduled for an early January 2001
release date.
CAESAR II Version 4.30
New Features(by: Tom Van Laan & Richard Ay)
CAESAR II Version 4.30 is a major release providing users withsignificantly enhanced analysis capabilities, as well as additional
user interface improvements. A list of the major additions and
improvements for Version 4.30 are listed in the table below.
CAESAR II Version 4.30 Features
Improved 3-D graphics
New Load Case Editor, offering different combination methods, load scale factors, andmore
Undo/Redo in the input module
Z-axis vertical
MS WORD as an output device
Code Compliance report (statics only)
Load Case Report
ODBC/XML wizard interface for CAESAR II input and output
Graphics in the WRC 107 Module
Animated Tutorials
New Configuration Options
User-Configurable Toolbar in Input Module
Updated piping codes: B31.1, B31.3, ASME NC, ASME ND
Graphics Improvements:
The 3D graphics have been improved to provide more informati
to the user. These improvements include:
When the button is in selected mode, the user can add annotatio
with leader lines, to the graphics.
Font type, size and color, may be changed for the annotati
through use of the button, followed by the Fonts tab.
Clicking the or the buttons (or using the Options-Diamet
or Options-Wall Thickness menu commands) highlights the pipi
model, by color, according to its diameters or wall thickness
respectively.
Three new standard views (YX, ZX, and ZY) have been adde
Standard views are accessed by the , , , , , , and
(isometric) buttons.
Changes to graphics settings are restored whenever users exit a
return to the graphics view. Alternatively, the user may se
standard setup to be always restored upon entering graphics. T
is done through the use of the button, followed by the U
Options tab.
The CAESAR II Animation module has been converted to u
these new 3D graphics. Zooming, rotating, and panning can now
easily controlled via the mouse, in exactly the same manner as t
input graphics.
Static Load Case Editor Enhancements:
The CAESAR II Static Load Case editor now offers much mo
user control. New features include use of scale factors wh
including load components in load cases or previous load cases
load combinations; user-defined load case names; user-controll
combination methods (for combination cases only); and grea
user control of what output data gets produced.
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Note that previous load cases are now referred to, in combination
cases, as L1, L2, L3, etc. (Load Case 1, Load Case 2, Load Case 3,
etc.) rather than DS1, FR2, ST3, etc., since it is no longer meaningful
to talk about combinations being done at the displacement level,
force level, or stress level.
Scale factors for load components and previous load cases incombinations: When building basic load cases, load components
(such as W, T1, D1, WIND1, etc.) may now be preceded by scale
factors such as 2.0, -, 0.5, etc. Likewise, when building combination
cases, references to previous load cases may also be preceded by
scale factors as well. This provides the user with a number of
benefits:
1) In the event that one loading is a multiple of the other (i.e., Safe
Shutdown Earthquake being two times Operating Basis Earthquake,
only one loading need be entered in the piping input module; it may
be used in a scaled or unscaled form in the Load Case Editor.
2) In the event that a loading may be directionally reversible (i.e.,wind or earthquake), only one loading need be entered in the piping
input module; it may be used preceded by a + or a to switch
directionality.
Load Rating Design Factor (LRDF) methods may be implemented
by scaling individual load components by their risk-dependent
factors, for example:
1.05W+1.1T1+1.1D1+1.25WIND1
User-defined load case names: CAESAR II now offers a second
tab on the Static Load Case screen Load Case Options. Among
other features, this screen allows the user to define alternative, moremeaningful Load Case names, as shown in the figure.
These user-defined names appear in the Static Output Processor in
the Load Case Report (for more information, see below), and may
also be used in place of the program load case names anywhere in
the Static Output Processor, by activating the appropriate option
therein.
Note, these load case names may not exceed 132 characters inlength.
User-controlled combination methods: For combination cases
CAESAR II now offers the user the ability to explicitly designate
the combination method to be used. Load cases to be combined are
now designated as L1, L2, etc. for Load Case 1, Load Case 2, etc.
with the combination method selected from a drop list on theLoad
Case Options tab. The available methods are:
Algebraic: This method combines the displacements, 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 andelement cross-sectional parameters) to calculate the piping
stresses. Load case results are multiplied by any scale factor
(1.8, -, etc.) prior to doing the combination. (Note that the
obsolete CAESAR II combination methods DS and FR used
an Algebraic combination method. Therefore, load cases buil
in previous versions of CAESAR II using the DS and FR
methods are converted to the Algebraic method. Also, new
combination cases automatically default to this method, unless
specifically otherwise designated by the user.) Note that in the
load case list shown in the figure, most of the combination
cases typically are built with the Algebraic method. Note tha
Algebraic combinations may be built only from basic (i.e.
non-combination) load cases or other load cases built using theAlgebraic combination method.
Scalar: This method combines the displacements, forces
moments, restraint loads, and stresses of the designated load
cases in a Scalar manner (i.e., not as vectors, but retaining
consideration of sign). Load case results are multiplied by any
scale factors prior to doing the combination (for example, for a
negative multiplier, stresses would be subtractive). 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 (i.e., scalar addition of the Sustained and Occasiona
stresses). (Note that the obsolete CAESAR II combination
method ST used a Scalar combination method. Therefore
load cases built in previous versions ofCAESAR II using the
ST method are converted to the Scalar method.)
SRSS: This method combines the displacements, forces
moments, restraint loads, and stresses of the designated load
cases in a Square Root of the Sum of the Squares (SRSS
manner. Load case results are multiplied by any scale factors
prior to doing the combination; however, due to the squaring
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used by the combination method, negative values vs. positive
values will yield no difference in the result. This method is
typically used when combining seismic loads acting in
orthogonal directions.
Abs: This method combines the displacements, forces,
moments, restraint loads, and stresses of the designated loadcases in an Absolute Value manner. Load case results are
multiplied by any scale factors prior to doing the combination;
however, due to the absolute values used by the combination
method, negative values vs. positive values will yield no
difference in the result. This method may be used when doing
an Occasional Stress code check (i.e., absolute summation of
the Sustained and Occasional stresses). Note that the Occasional
Stress cases in the figure are built using this method.
Max: For each result value, this method selects the
displacement, force, moment, restraint load, and stress having
the largest absolute value from the designated load cases; so no
actual combination, per se, takes place. Load case resultsare multiplied by any scale factors prior to doing the selection
of the maxima. The report shows the signed value. This
method is typically used when determining the design case
(worst loads, stress, etc.) from a number of loads. Note that the
Maximum Restraint Load case shown in the figure uses a
Max combination method.
Min: For each result value, this method selects the displacement,
force, moment, restraint 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 factors prior to doing the selection of
the minima.
SignMax: For each result value, this method selects the
displacement, force, moment, restraint 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 factors prior to
doing the selection of the maxima. This combination method
would typically be used in conjunction with the SignMin
method to find the design range for each value (i.e., maximum
positive and maximum negative restraint loads).
SignMin: For each result value, this method selects the
displacement, force, moment, restraint 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
factors prior to doing the selection of the minima. This
combination method would typically be used in conjunction
with the SignMax method to find the design range for each
value (i.e., maximum positive and maximum negative restraint
loads).
User control of output availability:
CAESAR II allows the user to specify whether any or all of the lo
case results are retained for review in the Static Output Process
This is done through the use of two controls found on theLoad C
Options tab. These are:
Output Status: This item controls the disposition of the ent
results of the load case the available options are Keep
Discard. The former would be used when the load case
producing results that the user may wish to review; the lat
option would be used for artificial cases such as the prelimin
hanger cases, or intermediate construction cases. For examp
in the load list shown in the figure, the Wind only load ca
could have been optionally designated as Discard, since it w
built only to be used in subsequent combinations, and has
real value as a standalone load case. Note that load cases us
for hanger design (i.e., the weight load and hanger travel ca
designated with the stress type HGR) must be designated
Discard. Note that for all load cases created under previoversions ofCAESAR II, all load cases except the HGR ca
are converted as KEEP; likewise the default for all new ca
(except for HGR load cases) is also KEEP.
Output Type: This item designates the type of results that
available for the load cases which have received a KEE
status. This could be used to help minimize clutter on t
output end, and ensure that only meaningful results are retain
The available options are:
Disp/Force/Stress: This option provides displacemen
restraint loads, global and local forces, and stress
Example: This would be a good choice for Operaticases, when designing to those codes which do a co
check on Operating stresses, because the load case wou
be of interest for interference checking (displacement
restraint loads at one operating extreme (forces), and co
compliance (stresses). Note that basic (non-combinatio
and DS combination load cases developed under previo
versions of CAESAR II are converted with this Di
Force/Stress type. Likewise, new load cases created a
default to this Disp/Force/Stress type.
Disp/Force: This option provides displacements, restra
loads, and global and local forces. Example: This wou
be a good choice for Operating cases, when designing t
code which does not do a code check on Operating stress
because the load case would be of interest for interferen
checking (displacements) and restraint loads at one operati
extreme (forces).
Disp/Stress: This option provides displacements a
stresses only.
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Force/Stress: This option provides restraint loads, global
and local forces, and stresses. Example: This might be a
good choice for a Sustained (cold) case, because the load
case would be of interest for restraint loads at one operating
extreme (forces), and code compliance (stresses). Note
that FR combination load cases developed under previous
versions of CAESAR II are converted with this Force/Stress type.
Disp: This option provides displacements only.
Force: This option provides restraint loads, and global and
local forces only.
Stress: This option provides stresses only. Example: This
would be a good choice for a Sustained plus Occasional
load case (with Abs or scalar combination method), since
this is basically an artificial construct used for code stress
checking purposes only. Note that ST combination load
cases developed under previous versions ofCAESAR IIare converted with this Stress type.
Undo/Redo in the input module:
Any modeling steps done in the CAESAR II piping input module
may be undone, one at a time, using the Undo command, activated
by the button on the toolbar, theEdit-Undo menu option, or the
Ctrl-Zhot key. Likewise, any undone steps may be redone
sequentially, using the Redo command, activated by the button
on the toolbar, the Edit-Redo menu option, or the Ctrl-Yhot key.
An unlimited number of steps (limited only by amount of available
memory) may be undone.
Note that making any input change while in the middle of the undo
stack of course clears the stack of redoable steps.
Z-axis vertical:
Traditionally, CAESAR II has always used a coordinate system
where the Y-axis coincides with the vertical axis. In one alternative
coordinate system, the Z-axis represents the vertical axis (with the
X-axis chosen arbitrarily, and the Y-axis being defined according to
the right-hand rule). CAESAR II now gives the user the ability to
model using either coordinate system, as well as to switch between
both systems on the fly (in most cases).
Defaulting to Z-axis vertical: The users preferred Axis Orientation
may be set using the Tools-Configure/Setup option, on the
GEOMETRY DIRECTIVES tab. Checking the Z-axis Vertical
checkbox causes CAESAR II to default any new piping, structural
steel, WRC 107, NEMA SM23, API 610, API 617, or API 661
models to use the Z-axis vertical orientation. (Note that old models
will appear in the orientation in which they were last saved.) The
default value in Configure/Setup is unchecked, or Y-axis vertical.
Orienting a piping model to Z-axis vertical: A new piping mode
will determine its axis orientation based on the setting in theConfigure/Setup module, while an existing piping model will use
the same axis orientation under which it was last saved. The axis
orientation may be toggled from Y-Axis to Z-Axis Vertical by
activating the checkbox on the Kaux-Special Execution Parameters
screen, as shown in the figure.
Activating this checkbox causes the model to convert immediately
to match the new axis orientation (i.e., Y-values become Z-values
or vice versa), so there is effectively no change in the model only
in its representation, as shown in the following figures:
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This allows any piping input file to be immediately translated from
one coordinate system into the other.
When including other piping files in a piping model, the axis
orientation of the included files need not match that of the piping
model. Translation occurs immediately upon inclusion.
When including structural files in a piping model, the axis orientationof the included files need not match that of the piping model.
Translation occurs immediately upon inclusion.
The axis orientation of the Static Load Case Builder (i.e., wind and
wave loads), the Static Output Processor, the Dynamic Input Module,
and the Dynamic Output Processor is dictated by the orientation of
the models input file.
Orienting a structural model to Z-axis vertical: A new structural
model will determine its axis orientation based on the setting in the
Configure/Setup module, while an existing structural model will
use the same axis orientation under which it was last saved. The
axis orientation may be toggled from Y-Axis to Z-Axis Vertical bychanging the value of the VERTICAL command, activated by
clicking the button on the toolbar, or through the Commands-
Miscellaneous-VERTICALmenu command, as shown in the figure.
Note: Unlike the piping and equipment files elsewhere
CAESARII, toggling this setting does not translate the structu
input file, but rather physically rotates the model into the n
coordinate system, as shown in the figures below:
(Note to Beta testers: Is it OK to handle the axis orientatconversion differently in the Structural Input Module than how i
handled elsewhere in CAESAR II?)
When including structural files in a piping model, the axis orientati
of the included files need not match that of the piping mod
Translation occurs immediately upon inclusion.
When analyzing a structural model on its own, the axis orientati
of the Static Load Case Builder (i.e., wind and wave loads), t
Static Output Processor, the Dynamic Input Module, and t
Dynamic Output Processor is dictated by the orientation of t
structural models input file.
Orienting an equipment model to Z-axis vertical: The WR
107, NEMA SM23, API 610, API 617, and API 661 equipme
analytical modules may also utilize the Z-axis vertical orientatiA new equipment model will determine its axis orientation based
the setting in the Configure/Setup module, while an existi
equipment model will use the same axis orientation under which
was last saved. The axis orientation may be toggled from Y-Axis
Z-Axis Vertical by activating the checkbox typically found on t
second data input tab of each module, as shown in the followi
figures:
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Activating this checkbox causes the model to convert immediately
to match the new axis orientation (i.e., Y-values become Z-values,
or vice versa), so there is effectively no change in the model only
in the terms of its representation.
When using the Get Loads From Output File button to read in
piping loads from CAESAR II output files, the axis orientation of
the piping files need not match that of the equipment model.Translation occurs immediately during the read-in of the loads.
WORD as an output device:
For those users with access to Microsoft WORD, CAESAR II
provides the ability to send output reports directly to WORD. This
permits the use of all ofWORDs formatting features (font selection,
margin control, etc.) and printer support from the CAESAR II
program. This feature is activated through use of the button (or
some variant) instead of the (display), (print), or (print to
file) buttons when producing a report.
WORD is available as an output device from the following modules
Static Output Processor: Multiple reports may be appended to
form a final report by selecting the desired reports, clicking the
button, closing Word, selecting the next reports to be added, clicking
the button again, etc. A Table of Contents, reflecting the
cumulatively produced reports always appears on the first page of
the WORD document.
Dynamic Output Processor: This processor operates exactly as
does the Static Output Processor: Multiple reports may be appended
to form a final report by selecting the desired reports, clicking the
button, closing WORD, selecting the next reports to be added
clicking the button again, etc. A Table of Contents, reflecting
the cumulatively produced reports always appears on the first page
of the WORD document.
Intersection SIF and Bend SIF Scratchpads, WRC 297, Flange
Analysis, B31G, and Expansion Joint Rating: Clicking the
button performs the calculation and sends the results to WORD.
WRC 107: Clicking the button, rather than the button
performs the initial WRC 107 calculation and sends the results to
WORD. Subsequently, clicking the button performs the Section
VIII, Division 2 summation and appends those results to the WORD
document.
NEMA SM23, API 610, API 617, API 661, HEI, and API 560
Pressing the button performs the calculation and sends the
results to WORD.
Code Compliance report:
Stress checks for multiple static load cases may be included in a
single report using the Code Compliance report, available from the
Static Output processor. For this report, the user selects all load
cases of interest, and then highlights Code Compliance underRepor
Options. The resultant report shows the stress calculation for al
load cases together, on an element-by-element basis.
Load Case Report:
TheLoad Case Reportdocuments the Basic Names (as built in the
Load Case Builder), User-Defined Names, Combination Methods
Load Cycles, and Load Case Options of the static load cases. This
report is available from the General Computed Results column o
the Static Output Processor.
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ODBC/XML Wizard for CAESAR II input and output:
CAESAR II now offers an ODBC Wizard for immediate
interfacing (in addition to the in-line interfacing offered previously)
of both input and output piping model data. (Note that the input
data may only be accessed through the Wizard; while the in-line
interface still transfers only the output data.)
This Wizard, besides being compatible with ODBC (Microsoft
Access and Excel) can also export data in XML format. (Note that
theExcel interface, which was excruciatingly slow under the previous
version ofCAESAR II has been changed to produce a semi-colon
delimited text file, which can be imported into Excel very quickly.)
The interface is accessed via the Tools-External Interfaces-Data
Export Wizardmenu command from the CAESAR II Main Menu.
This brings up the initial Wizard screen; the exported data set can
be developed by simply responding to the questions and clicking
the Next buttons.
The setup procedure defined in the previous newsletter is still
required prior to accessing the new wizard.
Graphics in the WRC 107 Module:
The WRC 107 Analysis module now provides a graphicrepresentation of the nozzle and its imposed loads. This can
accessed via the button on the toolbar.
The displayed load case (SUS, EXP, OCC) can be varied
selecting the tab for that load case immediately before activating t
graphics.
Animated Tutorials:
Under theHelp-Animated Tutorialsmenu of the CAESAR II M
Menu, the user can find a list of a number ofViewlets which u
animation, text, and voice over to demonstrate answers to common
asked questions. (Clicking on the topic runs the tutorial.) The
tutorials, which typically have durations ranging from 30 seconds
5 minutes, cover a variety of topics.
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TANK Version 2.20 Released(by: Richard Ay)
In September 2000, TANK Version 2.20 was officially released.
This version ofTANK incorporated Addendum 1 to the 10th Edition
of API-650. Changes in this Addendum include material
modifications and changes to the way corrosion is handled in the
Seismic computations of Appendix E. Since the release of Version
2.20 in September, two updates have been issued and are available
for download from the COADE web site. These updates correct a
data problem in non-US structural steel databases, modify roof
allowable stress checks, and modify live-load reporting for roof
designs.
Anyone using a version ofTANK prior to Version 2.20 should
upgrade immediately. All users of Version 2.20 should ensure they
have the build of 001205 installed.
New Pipe Stress Seminar Format(by: Dave Diehl)
Many of you received our new CAESAR II seminar mailer in late
November or early December. If you havent, you can review its
content on our web site or contact us to mail or fax one to you.
Beyond the 4-color presentation, the most striking component is the
label New Format for 2001. We have expanded the static
analysis section from three days to five days and the dynamic
analysis section from two days to three days. We have four static
sessions and three dynamics session scheduled through 2001.
Reasons for the change
At the conclusion of each seminar we ask all students to evaluate
our course content, instructors and materials. It is the response we
read again and again that indicates people want more time using the
program in group exercises and in individual workshops. Another
common comment is the course pace is too rapid, that there is too
much information to assimilate. We are addressing these issues by
extending the duration of the two segments to allow more time to
develop the topics and work with the software. Another common
suggestion is to provide both an introductory course and an advanced
course. That approach was tried several years ago when we had a
three-day introductory course just ahead of the standard five-daycourse. We were dissatisfied with the result of those arrangements,
as many students who did not attend the introductory course still
required introductory training to the chagrin of the other students.
We have always had to deal with varying levels of student experience.
By slowing down the pace of the course and increasing time on the
computers, we hope to improve the confidence and competence of
all students.
The new static analysis session format
The seminar now has more structure in the day-to-day format. The
first day will introduce the subject of pipe flexibility and stress
analysis focusing on the piping code requirements and generating
proper and effective CAESAR II input. Morning will be lecture
and afternoon will be spent working with the program. Tuesdaywill have the same morning/afternoon split but now the focus is on
properly designing piping systems. We will still focus on design
considerations for each of the basic load categories. Program work
will highlight output review and the redesign cycle; that is, identifying
the significant results and using them to direct system modification
All of Wednesday will be on the computers. We will review and
use many of the added modeling and analysis features of the program
This day will be spent with a job very similar to the tutorial found in
the CAESAR II Applications Guide. Thursday and Friday, the
added static analysis days, will be set aside for group exercises and
workshops. Four different subjects will be coveredtransmission
piping, occasional load evaluation, fiberglass pipe, and jacketed
riser design. We understand that these items are not of universainterest but they are important components of the program and
provide additional insight to the operations of the program, such as
buried pipe, jacketed pipe, and fatigue analysis. Friday afternoon
will be set aside for suggested approaches to documenting and
reproducing an analysis. The week will end with two or three smal
workshop problems to reinforce the learned skills of piping system
modeling, evaluation and redesign.
The new dynamic analysis session format
The three dynamics sessions are scheduled on Monday to Wednesday
of the week following the static analysis sessions. There is no carry-
over from the previous week so students can attend either the staticsor dynamics segment or both, if they wish. The content from the
old, two-day session remains but the pace is reduced and new
material is added. Monday morning covers the required theory and
the afternoon is a harmonic analysis exercise. Tuesday develops
seismic analysis of piping systems and surveys several approaches
to relief valve discharge analysis. This survey was published in the
December 1998 newsletter and provides an intuitive look at the
different types of dynamic analysis. The third day has a group
exercise reviewing time history analysis in CAESAR II and the
afternoon gives us an opportunity to practice what was learned
two or three small workshop problems.
Schedule for 2001
One item that has changed in our seminar brochure is the extent of
our seminar schedule. We normally print a two-year calendar bu
with this new format we thought it best to treat it with some healthy
skepticism and only announce the schedule for 2001. This schedule
appears below:
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Statics Dynamics
5-9 Feb. 12-14 Feb.
14-18 May 21-23 May
17-21 Sept. 24-26 Sept.
12-16 Nov. Not offered
COADE also provides in-house training at your site and training
organized by your local CAESAR II dealer. In both cases, a full
eight-day course may not be practical. For in-house applications,
this course can be tailored to focus the content and fit the available
schedule. Dealers will probably maintain the current five-day
course covering statics and dynamics or break the seminar into two
independent courses. Contact your dealer to learn more.
Continuing Education Units
You may be interested in knowing that our courses are monitored
by an outside organization for consistency and effectiveness. In
March 1997 the International Association for Continuing Education
and Training (IACET) certified COADE as an Authorized CEU
Sponsor. The Continuing Education Unit or CEU is a standard
measure of contact hours in training; basically ten contact hours
equal one CEU. IACET is quite rigorous in their criteria for
authorizing CEU sponsors. COADE has adjusted the course content,
presentation, and documentation to meet their standards. This year
we have renewed our application as an IACET Authorized Provider.
We are currently in the renewal cycle of that certification. Among
other uses, these CEUs serve as credit toward the maintenance of a
Professional Engineering license in those states where suchcontinuing education is required. To learn more about IACET you
can visit www.iacet.org. The five-day course will yield 3.5 CEUs
and the three-day course will 2.1 CEUs. If you do the math, thats
seven contact hours a day. In a change from previous courses, we
will start at 9AM rather than 8AM. This will decrease the sessions
from four hours to three-and-a-half hours and ease the intensity of
each session.
Responding to your comments
Once again, it is in response to the evaluations completed by our
students that we have introduced these changes. This new format is
not intended to pull old students back for additional training as the
new content is not segmented into a discreet section. But this
course will provide more complete coverage of those existing topics,
introduce new topics and allocate more time to using the program.
Obviously, one of the major concerns we have with this new course
format is the amount of time we are taking from your regular
schedule. Oftentimes the situation is such that when you really need
the training (a hot project is starting) you dont have the time
attend, and when you have the time to attend (no project; you are
overhead) you dont have the funding. We hope that your compan
commitment to quality work and continuing education will allow
broader outlook on the value of this course.
Sustained Stresses(by: John C. Luf of Washington Industrial Proce
Cleveland, O
Whats A Sustained Stress and why do we care about it?
Due to what may seem to some people, the controversial nature
this articles contents I would like to make it perfectly clear THE
ARE MY OWN OPINIONS! Although, I am sure some may ag
and yet others will disagree with some of the content of this artic
My intent in writing this article is to provide a forum for discussio
give sound advice, and some insight into the subject matter from t
past, present, and possibly the future points of view.
Well where to start? Perhaps we should start with a definition of
word Sustained. From my Random House Dictionary...- Sustain
To keep up or keep going as an action or process.
So how does this apply to the design of piping systems? Stres
caused by thermal displacements of the system are often call
secondary or self limiting. This is because ordinarily the
stresses decrease (slightly) over time. This is illustrated in
figure below, excerpted from one of Markls original papers on t
subject ofFlexibility or Stress Analysis.
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You can see that the stress level is not sustained it decreases over
time. As for why, a detailed discussion on this subject can be found
in various publications. Suffice it to say because these stresses are
displacement limited their very nature is self-limited. If the reader
wishes to ponder this a bit more, a simple example would be to, take
an L bend geometry anchored on each end. Imagine it heated or
cooled to the same temperature time and time again. The stresseswill never increase over the maximum from the first heat up so long
as the maximum temperature of the first heat up is never exceeded.
If the strains in the L bends elbow exceed the yield stress of the
metal (as is permissible by the B31 codes) the small area of highest
stress that exceeds the yield strength of the metal in the elbow
yields or deforms. This deformation then redistributes the internal
strain energy to a larger surface and hence the peak stress value
decreases as shown in the hypothetical graph in the figure above.
This cycle of load application, material yielding, and strain
redistribution will occur repeatedly during the first few cycles.
After the strain has been fully redistributed the system will have
been shaken out. This entire phenomenon is often described as a
strain controlled phenomena. After full shakeout occurs allsubsequent cycles will behave in an elastic manner.
Well what types of stresses are sustained? Or better yet what
types of imposed loads on a piping system are sustained and
unrelenting? For an earth bound or planetary-based piping system
everything within that planets field of gravity is constantly loaded
by the gravitational field in a sustained manner. Therefore weight
is a sustained load. Based on the science of Strength of Materials
we know that the bending stress for a simply supported beam has
the maximum stress, located along the bottom of the pipe, at the
midpoint of the span, in the outermost fiber of the pipe.
Mmax at point (C)
M maxw l
2
8:=
and MaxMmax
Z
What other loads are sustained in nature, that act on piping systems?
In general piping systems which become candidates for analysis are
pressurized. This internal pressure loads the pipe walls in tension.
Therefore pressure is generally considered a sustained load (L).
A fair question might be asked, If these loads do not produce
stresses which are self limited what would be the consequences of
an overstressed system? Lets say there is a hypothetical pipingsystem with a span in it that imposes a weight induced bending
stress well above the SMYS (Specified Minimum Yield Strength)
of the metal. Let us also assume during construction the fitter
worried about the saggy, droopy, pipe and add some chainfalls at
the midspans of the longer spans. After hydrotesting is finished the
fitters start cleaning up, they pull the first chainfall out and the next
and so on... The pipe is highly over stressed.... Guess what? When
they take off their chainfalls they also get an extra work order! The
extra work is to replace the pipe, which has collapsed, torn out and
is lying in a pile of twisted metal on the floor below. This is one o
the major concerns of sustained loads; they are also known as
collapsing loads. Other real life examples are buildings, which
suddenly collapse under their weight loads.
I will digress for a moment to talk about the sustained loads of
pressure and weight. Piping systems that are filled and then drained
as a part of their normal operation have that portion of their weight
which is the fluid, acting as a cyclic load. In like manner these types
of systems would have the internal pressure acting as a cyclic load
These cyclic loads are fatigue based loads. Indeed extreme
pressure cycling (unsteady flow pulsation) has been known to cause
failures. However most piping systems do not operate in these
manners (except incidentally), but if a system does operate in this
manner, the issue of sustained versus fatigue type loads should be
considered, however for most systems a few cycles of filling and
draining are of no significance.
Now what does B31.3 say about sustained stresses? 302.3.5 (c
The sum of longitudinal stresses in any component in a piping
system, due to pressure, weight and other sustained loadings shall
not exceed Shin (d) below. The thickness of pipe used in calculating
SL
shall be the nominal thickness T minus mechanical, corrosion
and erosion allowance c, for the location under consideration. The
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14
loads due to weight should be based on the nominal thickness of all
system components unless otherwise justified in a more rigorous
analysis. Axial deadweight loads should be included with bending
in calculating these stresses.
Phew, just think my co-workers and family accuses me of being
long winded! Well let's take the long paragraph (consisting of only3 long sentences) apart one step at a time.
The first sentence combines bending stress due to weight, and
longitudinal stress due to internal pressure. This combination is
based upon the principle of superposition. The stress in the outermost
surface on the bottom of the pipe, (according to simple beam
theory) at the midspan due to a bending moment is a tensile stress.
(Whereas the outermost top of the pipe is under compression.) This
tension stress is combined with the longitudinal stress due to pressure.
These summated stresses are compared against the allowable value
of Sh. This is a more profound thing than people realize. First S
h
stands for the hot stress or... the basic allowable stress at the
maximum elevated temperature expected during the displacementcycle being analyzed. For most materials it is 2/3 of the SMYS
(specified minimum yield strength) of the material.
This is why when CAESAR II detects internal pressure in the input
file it recommends the code load case of W+P. Because this load
case in the program (W+P) contains no thermal displacements some
people refer to this load case as the cold stress load case. This is
wholly incorrect! The Code requires these sustained type stresses
to be reviewed not against the S value of the metal at 70F but rather
at the operating temperature of the metal. The code S value itself
may seem overly conservative (in most cases it is 2/3 of the SMYS
or 1/3 of the tensile strength of the material, whichever is lower at
temperature) but dont forget these loads are sustained loads. Ifthe metal yields due to these applied loads it will continue to yield
until it fails.
The curve above is a typical carbon steel yield curve. As you c
see, once you exceed yield strength the metal continues to stret
under the applied load for a long time. If the redistribution of
load into the yielded metal does not decrease the stress to bel
yield (as the code assumes it does not for sustained loads) the pipi
will fail at the ultimate strength line.
The allowed stress value used is Sh. Why does the code use w
may be a lower allowed S value for metal at a higher temperatu
Well the code seems to presume that once the system heats up it w
also be operating with internal pressure inside the system. In ord
to assure the structural integrity of the piping to these sustain
loads under these circumstances the Sh
is used.
In the remaining code sentences we see some additional interesti
things. The Code uses the approach that it is possible to have
majority of metal in place in a system in a non-corroded state w
the point(s) of highest Sustained stresses being corroded as far
strength is concerned. This approach may be called conservative
some, but it cannot be faulted as being unsafe!
Markl3 (for those who dont know, A.R.C. Markl and his colleagu
were the founding fathers of stress evaluation in the B31 cod
separated the sustained stresses in his original work from the therm
displacement and operating allowable stress range. This approa
guards against incremental collapse due to ratcheting effects.
Sustained Stress Multipliers (Indices):
Sustained Stress Indices (SSI) (or whatever they end up bei
called):
Why the long Code paragraph instead of a simple formula for SAfound under 302.3.5 (1a) i.e., S
A=f (1.25S
c+0.25S
h)? My belief
that some of the reluctance of the committee to provide an equati
for SL
is because of something we have not yet discussed and is n
yet in the Code (ASME B31.3) at the present time.
I hope the readers are all familiar with the term Stress Intensificati
Factor (SIF). These SIFs are used to multiply the beam elem
based calculated thermal (or) other type of displacement stresses
order to approximate the actual level of (higher stresses) that w
occur in the piping component. These SIFs as published in Appen
D of the code are based on physical fatigue tests of actual componen
Once the fitting breaks (a through wall leak develops) a simp
calculation is made as follows:
SM
Z
ia
S Nb( )
a 245000psi
N number_cycles_to_failure
b 0.2
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Factors a, and b are material specific, values shown are for carbon
steel.
This calculation is unique from some standpoints. First in lieu of
polished bars, actual welded piping components are tested. Second,
all SIFs are calibrated against a pipe butt weld. The standard pipe
butt weld is assigned an SIF of 1.0.
I have just spent a large amount of effort discussing SIFs, why?
Well as you can see a fatigue test multiplier (SIF) has very little to
do with a Sustained type load. Testing for a sustained type load
might be something on the order of adding weight onto the end of a
fitting in a test setup and seeing how much weight it takes to cause
the fitting to collapse. Then compare that load (perhaps assuming
that it has reached and exceeded the SMYS of the test specimen)
versus a calculated beam element stress. A formula might look like
Sustained Stress Index (SSI) SSI = SMYS/Calculated Stress (based
upon the actual collapsing load) and shall be no less than 1.0.
If we consider this in a thought experiment with some variouscommon piping components we can develop a feel for what an SSI
might be. Consider first an elbow. With a Standard Wt 6NPS LR
elbow we can see where the effect might not be too large. However
conversely a 6x6 NPS standard weight unreinforced intersection
would probably collapse with a much greater difference between it
and a calculated single piece beam element.
Failing all else I suppose we could set up a testing program.
However, to my knowledge such a testing program does not exist.
So to recap the current state as far as SSI factors are concerned...
1) SIFs are not applicable to Sustained collapsing type loads.
2) SSI factors may vary significantly based on the fitting geometry
and may be of greater significance for some fittings than
others.
3) The ASME B31.3 committee does not have a testing program
to derive SSIs currently, although it could be said various
agencies such as the Welding Research Council or the Pressure
Vessel Research Council stand ready to develop these factors
if funding becomes available (corporate donations welcome).
4) The code currently does not address SSIs or have an expression
written for the calculation of SL.
What to do about the SSI?
So whats a poor design stiff supposed to do? I have found over the
years to truly understand the issues of applying code rules to a
design one must be a historian and must be widely read of various
piping codes. When you buy a copy of a B31 code book you buy
the latest version of that code. Unfortunately the many accumulated
years of history of interpretations do not necessarily shine boldly
and visibly in the latest edition. For instance the B31.3 committee
has rendered two opinions on the subject of a SSI. In one
Interpretation (#1-34 (2/23/81)) they said the designer could ignore
the effect of any SSI and use a factor of 1.0. In another separate
interpretation (# 6-03 (12/14/87)) they said the designer could use a
factor of 0.75 x SIF. This seems confusing, but in part it is causedby a lack of information. Maybe if we look elsewhere we can gain
some help?
Turning to ASME B31.1 we find some interesting things on this
subject matter. We find first of all an expression for SL! Also we
find the calculated SL
stresses being multiplied by a factor of
0.75SIF. So if we base our engineering on nothing other than
populism it seems like we should use a SSI = 0.75 SIF 1.0, at leas
for right now1. So for the time being I would recommend that thi
factor of 0.75 SIF 1.0 = SSI be used in analysis. This can easily be
set in the CAESAR II configuration setup.
Set up of the configuration file (file name CAESAR.CFG) is readilyaccomplished through the Main menu as follows
1. From the main menu window select the configure set up icon
2. Next select the SIFs and Stresses tab.
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3. Select the 0.75 option from the drop down box and dont
forget to exit with save.
If for no other purpose this factor can act as a screening tool. For
instance I would be less concerned over a slightly over stressed tee/
intersection using 0.75 SIF as the SSI than an elbow1. In case of
doubt, though, a more rigorous review using alternate methods
should be made (When in doubt make it stout, or refine your
calculations).
Non - Linear Pipe Supports (+ys):
Personal Computers are the constant companions of design engineers
today. The advent of this ubiquitous technology is both a blessingand a curse. Currently in our world of compressed schedules and
segmented work efforts, pipe supports, their locations and types,
are often selected by a designer on the basis of span charts. The
Stress Analyst / Piping Engineer then accounts for thermal
displacements (as well as their impact) after the fact.
This approach while it may be more efficient (a maybe at best) can
cause significant difficulties to occur as far as sustained stresses in
the piping system are concerned. What am I talking about? When
displaced by thermal effects the system may completely or partially
lift off certain non-linear pipe supports.
What types of supports are non-linear? Pipe racks, trapezes, clevishangers, or any other support which supports the pipe fully only in
one direction. These types of supports are unable to provide the
same supporting force at the displaced position versus the non-
displaced position. I should also point out a legitimate use of a +y
support that is lifted off is a maintenance or turn around support.
These supports allow maintenance of flanged connections by
providing support for one or more sides of a flange which is un-
bolted during maintenance shut downs.
Pump
Hot Oil @ 600 F
Carbon Steel A53 Gr BPipeCarbon Steel Fittngs,Valves, and Pump
Load OnSupport Beam
Time
Temperature
Side Elevation of HypotheticalPump Support
2'-9"
Max Ld
No Ld
MaxOpTemp
AmbTemp
12'-0"
In the example above the load on the support beam carrying the pi
and some of the valve weight quickly decreases as the system com
up in temperature until finally it is lifted off and drops to zero lo
before the system gets to its maximum temperature! (Guess w
happens to the pump loading? I suppose thats what spring cans
used for!)
The result of this type of support lift off is that if one evaluates
system for SL
stresses in only one state you may not be seeing t
complete picture. The code requires evaluations for SL
at vario
temperatures. Some people call these evaluations as cold sustain
and hot sustained stress checks.
The following example illustrates the problems associate with supp
lift off. I have been permitted to borrow it from its current auth
Mr. Don Edwards of ASME B31.3 task group B. The task gro
has been working on a non mandatoryAppendix S whose purpo
will be to illustrate the code and its relationship to computeriz
analysis. Note in no way, shape, or form is this supposed
represent good practice! It is only a hypothetical layout!
10'-0"
40'-0"
10'-0"
20'-0"
Typ.
Stated Data:
Material-Carbon Steel A106Grb, AstmA234 Gr WPBNPS-16Wall-Standard Wt (0.375" Nom Wall)Elbows LRInsulation-3" Thk Density = 11.0 #/Ft3Corrosion Allowance = 1/16"Fluid Density=1.0 S.G.Maximum Op. Pressure = 500 P.S.I.G.Maximum Op. Temperature = 600 FMinimum Operating Temp = 70FInstallation Temp = 70 F
Fix Y
+Y
Anchor6 D.O.F.
Proposed Appendix S Model
1020
45 55
8040'-0"
Typ.
10'-0"
Typ.
90
Y
X
Z
+Y
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When the loop heats up, it will lift off the upper supports. The first
pass SL
code stress calculation is made with the upper supports
active i.e., supporting the pipe. This is required to obtain the
thermal displacements from the installed position to the displaced
position. When SL
is evaluated with the pipe sitting on these
supports SL
stresses are within the code allowable.
However when we look at the CAESAR II Restraint Summation
(in the 132 column format) at nodes 45 and 55 we see the loads go
to zero in the operating case and a look over at the displacements
shows a +y movement.
The liftoffs effects should be re-evaluated by performing another
SL
analysis with the supports at nodes 45 and 55 removed from the
model. When this is done it turns out the code SL
stress limit is
exceeded (this evaluation is made using a SSI = 0.75 SIF 1.0).
This second analysis determines the sustained stress (B31.3 Code
stress) redistribution, it is not used for any other purpose (i.e. code
stress review of displacement stresses). Leave the thermal data in
the job so that the proper Sh
is used. To sum up, the supports at
nodes 45 and 55 are used for evaluating the thermal displacements,
but are removed to evaluate the code sustained stress level. (It
should be noted that restraint summaries shown herein show the
pure thermal forces to illustrate the book keeping on the restraints.
These thermal loads would not be used for support design).
When this sample problem was discussed at the committee's last
meeting a visitor asked, Well what should be done? Some of the
committee members stated that first, an evaluation with the lifted
off supports removed from the model should be made and then
finally some members saidThat redesign of the system should
be made to eliminate the over stressed condition. Clearly some of
the committee members opinions do not agree with ignoring lift
off. The visitor then mentioned, You should put a spring can(s) onthe top of the loop! I myself countered that spring cans might not
be necessary! I disagreed strongly and suggested that jiggling
support locations around would probably solve the overload. Indeed
moving the supports at 20 and 80 inwards a couple of feet (towards
the loop) make the overstressed condition go away (Although the
midpoint sag would probably be unacceptable by most criterias for
drainage). Sometimes spring cans are good things (especially
adjacent to rotating and other sensitive/delicate equipment), and
other times adding a fixed pipe support(+y) or moving supports
around will easily solve a SL
overstress. In any event it is unlikely
that if or when Appendix S is published that the sample problems
will show a preferred solution. This is because the committee's role
is to tell the users to do their homework, give advice on how to do
the homework, but the committee will never do the users' homework
for them.
Judicious use of Engineering Judgement:
It is the authors opinion that engineering judgement can and
should play a role in the process of sustained stress evaluations
Turning to another example:
5'-0" 5'-0" 5'-0"
3'-0"
8'-0"
3'-0"
5'-0" 5'-0"
10 20 30
40 50
60
70 80
90
Design Data:Code: ASME B31.3Pipe: A53Gr B SmlssWall : Standard Wt.NPS: 6Elbows: L.R. 90Degree B.E.
Process Data:Maximum operating temperature :180FMinimum operating temperature: 70 FInstallation temperature : 70 FMaximum operating pressure 250PSIG
Y
X
Z
We have another hypothetical layout; this contrived geometry is
for illustration only. Other than the close support spacing in thi
example I have seen lines run in racks supported in similar fashion
on either side of the riser elbow pair.
If we look at a deflected plot of the operating case we see that the
pipe has clearly lifted off and when we take a look at the restraint
summation we see this as well.
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Load shift to
0, sticks out!
Small +
movement
Looking closely we see the liftoff(s) in the operating case are by
extremely small amounts. So what would be the appropriate way todeal with this design?
Well the first step has already been taken. That is a review of the
restraint summation. This essential step I suspect is often ignored!
I have heard people occasionally say that CAESAR II does not
evaluate support lift off correctly. However, I feel that a piping
engineer reviewing, and supervising the non-sentient computer is
essential to the work process. The review process and the ability of
who does the review is very important. When the lift off
displacement is equal to or less than the fabrication tolerance of the
piping, the designers gray matter is much more important than the
computers chip speed (D. Edwards).
One method of evaluation could be by feel, which is, it is readily
apparent that the bending stress portion of SLis minuscule. Therefore
the liftoff adjacent to the elbow becomes of no concern. However I
suppose there are those persons who are trying to develop feel. In
that case I suggest another way that you could look at this would be
to use a span chart such as found in MSS SP 69 2. Looking at its
span limits for 6NPS Std. Wt. Steel pipe that is used in water service
we see that we could have spans seventeen feet (17) in length. The
distance from node 40 to node 80 is only eleven feet (11 ) well
within the span chart limit. What about the effect of the SSI on the
elbows calculated code stresses? Well it feels like it should be low,
but in order to evaluate it numerically we will have to remove the
support lifted off at node 70, copy the file into a new name, and
reanalyze it using the SSI = 0.75 SIF 1.0 CAESAR II
Configuration option. When we do this and examine a stress report
we see all is well.
It should be noted that if one were to calculate the SIF for the
elbows per the Code you would get the number shown in the repo
CAESAR II will use a numerically adjusted value per t
configuration setup as a multiplier despite the fact that the code S
is shown on the report. Why not adjust the value shown on
report? Well the column heading says SIF, not SSI therefore
essence because the codes have not adopted the use of a SSI wh
do you call the ad hoc SSI in code terminology?
At this point I would suggest that we have met the intent of ASM
B31.3. We have evaluated the SL
stresses in two states and ha
complied with the code stress limit in both cases. I would suggnotations be placed on the restraint summation report at the lift
off nodes, such as Support liftoff is incidental, spans as lifted
comply with ASME B31.3 SL
limits
So a summation of one mans opinions:
9 Adult supervision of the computer is always required. W
I mean by this statement is, that I consider the computer to
like a young child who requires adult or parental supervis
at all times.
9 Use the CAESAR II, 0.75SIF option in the configurati
setup as a multiplier for the SL case. Its probably not 100right but it is more appropriate than 1.0. Besides whi
usually a maximum deflection criterion dominates the pi
support layout and design. (Editor's Note: CAESAR
defaults to use of the full SIF, not 1.0 as the SSI.)
9 Review the 132 column restraint summary reports looking
load shifts or lift off at non-linear +Y supports. Pay clo
attention to supports adjacent to rotating equipment.
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9 Evaluate the amount, type and locations of lift offs. If lift off
versus the system's design is minor or incidental write your
comments on the archival report.
9 If the lift offs are more than minor, such that their effects on
the code SL
cannot be readily discerned, remove the supports
(+ys) that are lifted off from the model. Rerun the sustained
stress case.
9 If redesign is required, modify the support scheme by support
relocation, or adding +y supports, or spring cans with the
thought in mind that spring cans (except when adjacent to
sensitive equipment nozzles) are usually less desirable.
References (additional reading):
1) Pressure Vessel and Piping Codes Journal of Pressure
Vessel Technology August 1988 Commentary on Class 2/3
Piping Rules Authors comment this provides some of the
technical background behind the use of the factor of 0.75 as a
SIF multiplier.
2) Manufacturers Standardization Society of the Valve and
Fitting Industry, Inc. Standard Practice SP69 "Pipe Hangers
and Supports Selection and Application".
3) Transactions of the ASME, February 1955,Piping Flexibility
Analysis
A huge thanks to my editors
Rich Ay, COADE
Dave Diehl, COADE
Don Edwards, Phillips Petroleum
Phil Ellenberger, WFI
Late Breaking News
Over a year ago COADE started the process to register its name
and all product names as trademarks with the U.S. Patent and
Trademark Office. We are pleased to report that both
CAESAR II and PVElite are now registered to COADE. Other
names should be registered soon.
Vessel seminar dates are announced. Our three day vessel
seminar using CodeCalc and PVElite is scheduled for 21-23
February and 10-12 October 2001. The first two days cover
component analysis (found in CodeCalc and PVElite) and theoptional third day continues with a whole vessel approach to
design in PVElite. Ask for a brochure or view a copy on our web
site for more information.
Please register as a user of our software. Registered users receive
a brief e-mail identifying new program releases and Builds as
they become available. This heads up will keep you up to date
with the current software and eliminate your need to monitor our
web site for new postings.
Utilizing the New Load Case Editor
in CAESAR II Version 4.30(by: Richard Ay
For Version 4.30, the Load Case Editor in CAESAR II experienced
significant revisions. These modifications simplify the specificationof load cases, streamline the output data, and allow additiona
analysis capabilities. The revised load case editor dialog is shown
in the figure below. In this figure, areas that have been changed are
indicated with numerals, and are explained in the following
paragraphs.
Item 1: In previous versions of the software, the available stress
types were listed on the lower left side of the dialog. (The stress
type determines what stress equations are used in the solution
module.) Users could either drag the stress type onto a load case
or manually type in the abbreviation. As of Version 4.30, the
stress type for each load case is selected from a drop list
Simply clicking on the stress type grid cell activates this drop
list.
Item 2: In previous versions of the software, algebraic load case
combinations could be combined at various levels; displacement
force, or stress. This was indicated on the right side of the dialog
where DS indicated the displacement level, FR indicated the force
level, and ST indicated the stress level. As of Version 4.30, thi
combination level idea is obsolete, and has been replaced by an
output type indicator. The type of output desired for a particula
load case can be specified on the Load Case Options tab, whose
dialog is shown in the figure below.
Item 3: The Load Case Options tab is new for Version 4.30
Clicking on this tab presents additional load case controls. These
new controls are shown in the figure below.
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Item 4: Any load case component can be preceded by a numeric
multiplier. This means that safety factors can be applied at the load
case level, instead of in the input.
Load Case Name: This grid column can be used to define a name
for a particular load case. For example, instead of wondering what
W+T1+P1+D1+F1 might represent, you can now type in a name
such as Operating + Cold Spring. Both the formal load case
component definition and the load case name can be used at the
output level for review and report generation.
Output Status: This grid column is used to specify whether or not
a particular load case will have output available for review. The
Discard setting allows intermediate and construction load cases
to be ignored by the output processor, which simplifies outputreview and evaluation.
Output Type: For load cases where the Output Status is set to
Keep, this grid column specifies exactly what type of output will
be available. So for a typical operating case, this setting should
indicateDisplacement/Force, while a typical expansion case should
indicate only Stress. With these settings, stresses would be
unavailable for the operating case, while displacements, forces, and
restraint loads would be unavailable for the expansion case.
Combination Method: Previous versions ofCAESAR II used an
algebraic combination method when combining load cases at
either the displacement or force level, and an absolute or scalarcombination method when combining load cases at the stress level.
{The use of an algebraic combination is required by the B31
codes (for instance see ASME B31.3 Paragraph 319.2.3) for review
of displacement stresses. In the review of B31 piping systems the
user is strongly encouraged to continue the use of the algebraic
summation method for the review of displacement stresses.}
As discussed above, this level idea is now obsolete, bei
superceded by the output status and output type settin
However, there are instances where it is necessary to control t
combination method used, as well as other methods in addition
algebraic and scalar. The additional combination methods
absolute, SRSS (square root sum of squares), Min, Ma
Signed Min, and Signed Max, have been added for Versi4.30.
Complete documentation on the correct usage of these options c
be found in the CAESAR II documentation, as well as the on-l
help. However, an example will be used to illustrate the usage
these new capabilities.
Assume we must statically analyze a model (with only line
boundary conditions) for a seismic event. (A plot of this symmetr
simple model is shown below.) For this seismic event, G load
have been specified for each global direction, X, Y, and Z. The
loads have been defined as U1, U2, and U3 respectively, as show
in the figure below.
To properly address the code requirements for occasional stre
checks, and to evaluate the restraint loads on the system, the followi
set of load cases have been defined.
Case Components Stress Type Comments
1 W+P1+T1 OPE Operating
2 W+P1 SUS Sustained
3 U1 OCC Seismic load X
4 U2 OCC Seismic load Y
5 U3 OCC Seismic load Z
6 L1-L2 EXP Expansion range code case
7 L3+L4+L5 OCC Resultant seismic load, SRSS combination
8 L1+L7 OCC Operating plus seismic combined absolutehot restraint loads
9 L2+L7 OCC Sustained plus seismic combined absolutecold restraint loads, code case
10 L9, L8 OCC Maximum restraint loads
With the new load case editor, these load cases can be defin
exactly as laid out in the table above. This load case layout
defined on two related dialogs, as shown in the figures below.
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The figure above is the familiar load case editor screen. Note
however that the load case stress type is now selected from a droplist for each specific load case. This drop list is shown activated
for the last load case in the figure above. The above screen is
essentially the same as in previous versions ofCAESAR II. The
two obvious differences are the stress type drop list and the setup
of the combination load cases. Consider for example load case 6
above. Previous versions ofCAESAR II would have listed case 6
as DS1 - DS2. As of Version 4.30, this same load case is listed as
L1 - L2. The combination methods and the output type (formerly
combination level) are defined on the second load case definition
dialog, shown in the figure below.
The second dialog shows the advanced load case controls offered
by Version 4.30. First, note that the load cases can be given
meaningful names - these names are user defined. Second, the
Output Status column provides two settings for each load case
keep and discard. In this context, keep means that the data
from the load case will be available for review in the output processor
while discard means that the data from the load case will not beavailable for review. The discard setting would typically be
applied to construction load cases, those cases used solely to
build other cases.
The Output Type column indicates what type of data will be
available for review in the output processor (assuming the Outpu
Status is set to keep). Setting a load case to Disp/Force/Stress
means that displacements, forces (and restraint loads), and stresses
will be available at the output level for review. Setting a load case
to Disp/Force means that only displacements and forces (and
restraint loads) will be available at the output level for review. This
is the preferred setting for typical B31.1/B31.3 operating cases
(OPE), where the stress results are not code related and are ofminimal use. Conversely, setting a load case to Stress means tha
only stresses will be available at the output level for review. This is
the preferred setting for typical B31.1/B31.3 expansion cases, where
only the stress range is needed. The displacements and forces fo
this case are also ranges and are typically of minimal use.
The final column on this dialog Comb Method defines for each
combination load case, the combination method to be employed. In
versions of CAESAR II prior to 4.30, combination load cases
combined at the displacement or force level were combined
algebraically. Load cases combined at the stress level were combined
in a scalar fashion. As of Version 4.30, the user has control over the
combination methods. Additionally, the combination methods havebeen expanded to also include Absolute, SRSS, Min, Max, signed
Min, and signed Max.
The best way to understand the new capabilities of the static load
case editor is through the use of the example started above
Examining the load cases in more detail shows:
Load cases 3, 4, and 5 are comprised of only a single seismic
load (direction). By themselves, these load cases provide
minimal information, they exist solely as construction cases
Load case 6 is the standard expansion load case, which
determines the extreme displacement stress range bysubtracting case 2 from case 1. In previous versions o
CAESAR II, this load case would have been denoted as DS1
- DS2.
Load case 7 is a combination case, constructed by computing
the square root sum of squares of load cases 3, 4, and 5. (Prio
versions ofCAESAR IIcould not perform this computation.
This load case yields the combined effect of the three seismic
loads.
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Load case 8 is a combination case, constructed by adding the
operating case to the combined seismic case. This combination
is made taking the absolute values from each of the component
load cases. (Prior versions ofCAESAR II could not perform
this computation.) This load case yields the absolute value of
hot restraint loads.
Load case 9 is a combination case, constructed by adding the
sustained case to the combined seismic case. This combination
is made taking the absolute values from each of the component
load cases. (Prior versions ofCAESAR II could not perform
this computation.) This load case yields the cold restraint
loads. This case is also the code compliance case satisfying
the requirements thesustained plus occasionalcode equation.
Prior versions of CAESAR II performed this code computation
at the stress level, i.e., ST2 + ST7.
Load cases 10 is a combination case, constructed by taking the
maximum results from cases 8 and 9. The absolute magnitude
of the values from each case are used in determining themaxima. (Prior versions ofCAESAR II could not perform
this computation.) This load case yields the maximum
restraint loads.
For this particular job, a review of the restraint summary for load
cases 3, 4, 5, and 7 shows expected results for this symmetric
model, as illustrated in the figure below.
Similarly, a restraint summary comprised of load cases 1, 2, and 7
yields expected results in cases 8 and 9, as illustrated in the figure
below.
And finally, a restraint summary comprised of case 8, 9, and
shows the maximum restraint loads as expected, illustrated in t
figure below.
In a production environment, with a real job, we can take mo
advantage of these new load case capabilities. In this sim
example, the results of load cases 3, 4, 5, and 7 are of minim
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interest - these are just construction load cases. Additionally, we
dont care what the stresses in the Operating case are, nor do we
care what the displacements and forces are in the Expansion case.
We can make these eliminations on the Load Case Options tab of
the static Load Case Editor. The figure below shows this dialog
after these changes have been made.
Upon running the analysis with this load case setup, the resulting
output menu is modified, as shown in the figure below.
Here we see that the load cases set to discard in the Load Case
Editor are labeled Not Active at the output level. We cannot
review data for these load cases. This greatly simplifies reporting,
and the need to explain why stresses for these cases are of no
importance. Another option that makes interpreting the results
easier is the user specified load case names. These user defined
names can be shown in the output by selecting the Load Case
Names option from the Options menu, or by clicking on the load