C-30 Guide to Ceaser 2

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STRESS ANALYSIS – GUIDE TO CAESAR II (Ver 4.10) PACKAGE

DOC No. : 29040-PI-UFR-0030 Rev. : R0 Page : 1 of 14

CONTENTS

Page

0.0

Cover Sheet

1

1.0

Introduction

2

2.0

Introduction to CAESAR II software

2

3.0

Using CAESAR II Program

2

3.1

Input

2

3.2

Output

8

4.0

Sample Problem

14

Annexure 1

1 - 69

Applicable Revision: Prepared:

Checked:

Approved:

Date:

Date:

Date:

Prepared: VPV

Checked: AKB

Approved: RUD

Date:

Date:

Date:

First Edition:

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1.0



INTRODUCTION This manual is meant to train a new CAESAR II user who has some technical exposure to stress analysis. The intent of this manual will be to go through the salient features of CAESAR II package as an introduction alone, and not as a full-fledged user manual. For details refer to the manuals provided by CAESAR II. The version of CAESAR II package referred to in this manual is version 4.10. The manual intends to cover the following activities - Using CAESAR II ’s input module - Interpreting of output for proper judgement of the system.

2.0

INTRODUCTION TO CAESAR II SOFTWARE One of the first professional stress analysis packages to emerge was SAP IV, developed in university of California. This was a finite element package, which could deal with piping, structural, plate and other elements. The package was made in FORTRAN and due to the inherent requirements of the language, inputting was cumbersome. Output interpretation was also very difficult. Moreover time required to process input was very high. Ever since, user friendly softwares have emerged and the one used in UIL is CAESAR II. CAESAR II deals with pipe elements alone.

3.0

USING CAESAR II PROGRAM CAESAR II is a stress analysis package, which does static and dynamic analysis for circular section piping. Static analysis stands for weight and thermal analysis. It can also analyze wind and static earthquake multipliers for computing stress and loads as part of static analysis. CAESAR II also does Dynamic analysis for detailed earthquake, water hammer analysis etc. This manual covers aspect related to static analysis alone. CAESAR II does analysis for both aboveground and underground piping. Pipes are modeled (broken) as elements, each element having 2 nodes, and each adjacent element having a common node for connecting them. All parameters required for analysis is fed into the software in it’s input module. This manual will deal with above ground piping static analysis alone. Details are as follows

3.1

INPUT The first step in the input module is to setup the standard setting. The main standard setting is done before entering input.

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3.1.1



Standard settings The standard settings are as follows.

3.1.1.1

Configure/Setup This feature, found in the main menu, has almost all the major setups for calculation. Input / Output unit files are set in this module. Some of the other features are, inclusion/exclusion of corrosion allowance in calculation for sustained/occasional stresses, setup of database files for valve data, bellows, springs, stiffness of restraints etc. It has all parameters and regulations required by various piping codes to handle stress analysis. This manual will refer to ASME B 31.3 for all setups.

3.1.1.2

Material database CAESAR II has an in built material database. This database has cold modulus of elasticity, Poisson’s ratio, and allowable stresses & coefficient of expansion tabulated at various temperatures. For an intermediate temperature, the program interpolates to get the values. These values will be used in the calculation. New materials can be input into the “Material database” feature, found in the main menu.

3.1.1.3

Kaux-Special execution parameters Once inside the input page, one can set ambient (installation) temperature, liberal stress flag (addition of Sh-SL in the allowable stress range), uniform load condition (explained later) etc in the “Special execution parameter” section of “Kaux” feature. The other features of “Kaux” are inputting other piping and structural files into the opened file, reviewing SIF for elbows and tees etc. Refer Annexure I, pages 1,2,3&4 for details.

3.1.1.4

Hanger design control data The “Hanger design control data” feature sets up the default hanger type to be used (example, Lisega, Sarathi etc). One can set up the desired combination of load cases for selection of springs and the nature of loading, allowable load variation etc. Refer Annexure I, page 5 for details.

3.1.2

Basic Input •

Nodes from and to – The piping network (or system) is broken into elements, each element having two node no: s, “from” node no: and “to” node no:. Node no: s should be unique, in the sense that a node once used will represent one point in space and hence cannot be used to identify a second point. As a standard practice nodes are numbered as 10, 20, 30 etc with a difference of 10. Refer Annexure I, pages 6&7 for details.

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•



Dimension of element “Dx,Dy,Dz” – These are the distance from the “from” node to the “to” node of the element. The direction cosines are as below. If the direction is negative, it has to be entered. Directions of moments are determined by right hand thump rule. Refer Annexure I, page 7 for details.

+y

+z

+x

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Diameter and thickness of pipe – The outside diameter and thickness can be entered as nominal diameter/schedule or as actual value. The software has a database, which will recognize the value entered as NB/Schedule, determine the actual value from the database and rewrite it in the input box. If the input is not entered as NB or as Schedule, the entered value will be maintained in the input. Refer Annexure I, page 8 for details.

•

Corrosion allowance – Enter the corrosion allowance in this field. As per ASME B 31.3, while calculating stresses for Sustained and Occasional cases, corroded thickness can be reduced from thickness of pipe. CAESAR II has given as option in the configuration feature to disable this usage. Refer Annexure I, page 8 for details.

•

Insulation thickness – Enter insulation thickness. Weight of insulation is calculated from density of insulation. Refer Annexure I, page 8 for details.

•

Temperature – Nine different temperature cases may be entered in this data box. CAESAR II gives flexibility for calculating multiple operating cases in the same file viz. startup conditions, steam out conditions, emergency shutdown conditions, stand-by situations, different temperature situations in the same line etc. If the material database is not available, then the coefficient of expansion may be directly input into the temperature field. (A value, less than 0.05 is recognized by the program as co-efficient of expansion). Refer Annexure I, pages 8&9 for details.

•

Pressure – Nine different pressure cases may be entered in this data box. The pressure value entered should be the gauge pressure. Refer Annexure I, pages 8&9 for details.

•

Bend – Activate this box for inputting bends/elbows. By default a standard 1.5D radius elbow is picked up. One can change the radius of the elbow in the input. Miter bends, where required, can be input in this sheet. Elbows can be identified as flanged elbows if applicable. Fitting thickness by default is taken as the pipe thickness. Thickness of each elbow may be changed locally. Provisions are provided in this sheet to identify intermediate points of the elbow by identifying the intermediate angle and providing it a unique node no:. The preceding element of the elbow must be input immediately after the element with elbow entry. Refer Annexure I, page 10 for details.

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•

Rigid – This field is used to enter weight of rigid fittings like valves, flanges etc. A standard database is available in the software (based on ASME valves and flanges). Apart from inputting weights, this field has an important function. If activated, the program understands that the element should be considered as a non-flexible element. Hence while modeling equipment, the equipment element is given a rigid weight of 0 (zero). The program considers the element as a rigid element and not as a flexible pipe element. Weight of fluid, insulation and pipe will not be considered for an element referred in the input as a rigid element. Refer Annexure I, pages 9 & 11 for details.

•

SIFs and tees – CEASAR II has a database for almost all common tees. By specifying the type of tee, it’s flexibility and SIFs are picked up from the database. For a tee outside the database one has to calculate the SIFs and feed it into the input. For reducers, as advised in the CAESAR II manual, average diameter and thickness is to be entered into the input and SIF value of 2 is to be provided at both nodes inlet and outlet. Refer Annexure I, page 24 for details.

•

Restraints – Restraint entry may be evoked by activating the restraint box. The most common restraints are resting (+Y), guides and limit stops and anchors. X stops or Z stops may be specified if the line is along X or Z axes. Rotational stops are RX, RY, and RZ. The other restraint types available in the CAESAR II database are XROD,YROD,ZROD etc (rigid rods, commonly used for finer adjustments of rotating equipment), X2,Y2,Z2 etc (used for soil modeling e.g.: in buried pipe modeling of CAESAR II package), XSNB,YSNB,ZSNB (snubbers – supports that allow slow movements like thermal expansions but do not allow quick movements like wind earthquake 15 etc). By default stiffness of the restraint is supposed to be 1e N/mm. If stiffness of the structure is known, it can be fed in at this box (This is not normally used, due to the difficulty of getting the right stiffness. Moreover any change in structure will effect the stress calculation). For all resting supports (especially for heavy pipes and for piping near equipment) one has to enter the co-efficient of friction. For CS to CS surface = 0.3, SS to CS surface = 0.15, and for PTFE to SS surface = 0.10. If the restraint has an initial displacement, the value can be fed vide a CNODE. A restraint connects the pipe to a rigid element in space, whereas by specifying connecting nodes (CNODE) the pipe is connected via the CNODE. All parameters specified in the CNODE apply to the restraint point. Refer Annexure I, page 12 for details.

•

Displacement – This field is used to input initial displacements at a specific point (e.g.: equipment nozzle displacement). Basically by providing displacement values in the input, one is providing restraints with initial movement. One has to enter the node no., displacements and rotations in the three directions. If any entry is left blank, the program assumes that that particular displacement/rotation is free. Refer Annexure I, page 13 for details.

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•

Spring hangers – CAESAR II normally selects spring hanger by itself. A no: of controls like hanger/can, short range/middle range/ long range, % variance, no: of hangers at one point, free nozzle loads, rigid support displacement criteria, variable/constant operating load etc can be controlled while selecting the hanger. The user, on the other hand, has the option of selecting a hanger on his own. However, in such a case, the user himself will have to check whether the displacements and loads calculated are acceptable. There are 19 spring vendors database available with CAESAR II version 4.10. The spring, by default should be set to COLD load as installation load. Refer Annexure I, page 26 for details.

•

Expansion joint – CAESAR II has a set of standard expansion joint databases that can be used by the user. One can also input stiffness value manually. In that case the axial stiffness and translational or bending stiffness has to be entered. To model a break in pipe stiffness, enter the stiffness value as 1. This will give a completely flexible bellow. There are three main types of bellows commonly used, based on requirement. They are axial (e.g. near rotating equipment), lateral (only in horizontal directions) and universal (all directions). A fourth type angular bellows are rarely required. For lateral bellows one can take care of axial thrusts by providing tie rods, whereas for axial & universal bellows, supporting should be done properly to take care of these loads. Refer Annexure I, page 11 for details.

•

Nozzles – This is a feature that calculates the nozzle’s flexibility and takes advantage of it in the calculations. ASME codes specify WRC bulletin 297 for nozzle flexibility calculation. CAESAR II calculates nozzle flexibility as per API 650 and BS 5500 too. However as a standard practice nozzle flexibility is to be avoided. It should be considered only for large pipes, where change in routing is difficult and the pipe size is large compared to size of equipment and the forces imparted by the pipe can have large effects on the nozzle. Refer Annexure I, page 25 for details.

•

Forces/Moments – Concentrated forces viz. Safety valve pop-off forces, and moments can be input in this field. Nine sets of forces can be input in this field. Since for calculation of spring hangers, the program uses F1 for tabulating spring forces, it is advisable to avoid using the first set viz. F1 for force and moment input. Refer Annexure I, page 14 for details.

•

Uniform forces – Uniform forces can be entered either in units of force/unit length or as a multiplier of g (acceleration due to gravity). This can be achieved by toggling in the KAUX feature. For earthquake prone zones, depending on the criticality of the plant, either a detailed dynamic analysis can be done, or a static multiplier can be used to generate results similar to that of dynamic analysis, as far as forces and stresses on the piping is considered. For chemical and petrochemical plants in earthquake prone areas, usually a static earthquake multiplier is used. Refer Annexure I, page 14 for details.

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•

Wind – Wherever wind loads are expected to be large, the wind shape factor is to be entered in this field. Wind loads have to be considered for lines in open area prone to wind and having size, along with insulation, 24” and above. The parameters for calculating wind forces are entered while executing the program. One can either enter elevation vs. wind velocity, or elevation vs. wind pressure in a tabular form. Wind load parameters can also be computed using methods recommended in ACSE#7-1995. This is only applicable for certain zones in the globe for which the ASCE code has time history study values. Refer Annexure I, pages 15 & 16 for details.

•

Material – CAESAR II has an in build material databases in it, which contains the coefficient of expansion and allowable stresses for certain standard materials. Apart from standard materials, this database also has values for materials based on general category, e.g. low carbon steel, austenitic stainless steel etc. Allowable stresses will not be available for these no’s. For materials not included in the database one can enter one’s own data as explained in section 3.1.1.2 or provide coefficient of expansion in the temperature field. This field also has options to provide cold cuts in the line. Refer Annexure I, page 17 for details.

•

Allowable stress – For all standard materials available in CAESAR II database, allowable stresses are also available. Sc & Sh values are picked up from the database (however this has to be verified with code values for each calculation). For all other items, allowable stress values have to be picked from the respective codes (ref ASME B 31.3 Appendix A for allowable stresses. If the material is not included in the Appendix, then allowable values can be calculated as per clause no: 302.3.2 (d)). Refer Annexure I, page 18 for details.

•

Elastic modulus – As per ASME B 31.3 cold modulus of elasticity has to be used for stress calculations. If the value is not available in CAESAR II database, the same has to be filled in manually. However the database value has to be verified with the code. Refer Annexure I, page 17 for details.

•

Poisson’s ratio – If this value is not available in the database the same has to be entered manually. However the database value has to be verified with the code. Refer Annexure I, page 17 for details.

•

Pipe density – If this value is not available in the database the same has to be entered manually. However the database value has to be verified separately. Refer Annexure I, page 19 for details.

•

Fluid density – This has to be fed in manually. Fluid weight will not be considered for rigid elements. Refer Annexure I, page 19 for details.

•

Insulation weight – This has to be fed in manually. Insulation weight will not be considered for rigid elements. Refer Annexure I, page 19 for details.

•

Cartesian co-ordinates – This field has to be filled in for wind load calculations since wind velocity/pressure is input as a function of elevation.

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Moreover Cartesian co-ordinates helps one to make a quick check on input dimension accuracy. •

Title sheet – The input has a title sheet which can be used as a title document (However UIL has it’s own title document in GENL-PI-UZ-0102). The default file is title.hed available in the program’s directory. Copying it in the working directory can costumerise it. Refer Annexure I, page 5 for details.

•

PLOT – The package has a plot facility by which one can plot the system, view it’s parameters and toggle with colours for better interpretation. Refer Annexure I, pages 20,21 & 22 for details.

•

INPUT LIST – It is possible to view all inputs in the form of spreadsheets for a full view by using the list input format. Refer Annexure I, page 23 for details.

3.2

OUTPUT

3.2.1

Generation of output file

3.2.1.1

Checking input files The program first checks and verifies accuracy of input. Warning messages are shown for minor discrepancies, which have to be reviewed. Major discrepancies will be shown as errors. The program will not go ahead unless the error messages are taken care off. Common errors are loop closure errors, bend modeling not done properly etc. Refer Annexure I, pages 27,28 & 29 for details.

3.2.1.2

Setting of load cases Load cases are set by CAESAR II automatically. Only basic load cases will be provided, viz. OPE, SUS and EXP. All other requirements must be done manually. A typical load case is shown below.

Case 1 has W (weight) + T1 (temperature case 1) + P1 (pressure case 1) which is the normal operating case (OPE). Case 2 has W (weight) + P1 (pressure case 1) which is the sustained case (SUS). Case 3 is the difference between Case 1 and 2, which is the expansion case (EXP). DS1 stands for addition done at displacement level. (The hierarchy of

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calculation starts with computing displacements, and then forces and moments and then stresses.) A load case with spring hanger is shown below. Note that case 1 & 2 are reserved for hanger calculation. It there are more than one temperature cases (e.g. T1, T2 etc), the user can use either of it by specifying it in the hanger setup or at load case setting, by toggling the temperature case. F1 in case 3 & 4 is the load of the spring hanger.

Load cases with 2 temperature cases are shown below

A load case with occasional loading (OCC) is shown below. U1 & U2 stands for uniform load cases, WIND stands for wind case and ST stands for addition at stress level. Since stress calculation is done after displacement and force & moment calculation, cases 9, 10 & 11 will only give stress results and not displacement and force & moment results. Addition by these cases will be absolute addition. Case1 is normal operating. Case 2 is operating with U1. Case 4 is operating with WIND. Note the additions done in cases 9,10 &11. These are as per Eq(3) of clause 2.1.

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A load case with safety valve pop-off forces and other occasional loading are shown below. D1 is initial displacement. F2 & F3 are safety valve forces. WNC stands for weight without contents. One can enter fluid weight in input and run a case without considering its weight.

Refer Annexure I, pages 30 & 31 for details.

3.2.2

Output viewing The Static Output Processor screen has three tables, Load Cases Analyzed, Report Options, General Computed Results. Load cases analyzed gives the screens shown above in section 3.2.1.2. “Report Options” have displacements, restraint summary and stresses as the most commonly used ones. “Displacement” gives movements of each node for a particular load case in translation and rotation directions. “Restraint Summary” gives forces and moments for a single or combined group of load cases. (If evoked in 132 columns, it gives the translation displacement too). Restraint summary prints reports for nodes that are identified as having supports, anchors, displacements and nozzles alone. To view forces and moments for all nodes one can use “Global Element Forces” option load case wise. Stresses and its summary can

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be viewed load case wise by the “Stresses” option. The option “Sorted Stresses” gives a stress report sorted by combined stresses. “General Computed Results” has options for printing hanger output results, input echo and certain miscellaneous data (co-efficient of expansion, BOM of pipes etc). Refer Annexure I, pages 32,33,34,35,36 & 37 for details. 3.2.3

Output interpretation (1) Isometric check: - Before starting the input, one has to check and review the isometrics w.r.t supporting and flexibility. Basic supports and guides should be provided to cater for weight and loading on connected equipment. Supports should be feasible, economical and aesthetic to view. Large posts and cantilevers should be avoided. Pipes and supports should be grouped together to be supported by common supports rather than multiple individual supports. Springs should be avoided at initial stage itself. One should try to put in rigid supports, which would make the lines stable, however assuring that enough flexibility is provided to it so as not to over stress the piping system or over load equipment and structure. (2) Stress check: - On creation of output files, one has to first check the sustained stresses and expansion stresses. Sustained stress should be less than 65%. Only in exceptional cases can one go to 70%. ASME B 31.3 does not o cover SIF calculation for tees other than 90 . CAESAR II uses SIFs of normal tees for all angular tees. SIFs at the shorter angle side of such tees will be larger than SIFs of a normal tee. Hence one has to assure that sustained stresses calculated at such tee junctions, with this package, are low. However SIFs for all sections can be calculated using finite element packages. It would be best to calculate SIFs using a finite element package and input it in CAESAR II separately. Expansion stresses should be less than 75% except in exceptional cases. Although ASME B 31.3 allows one to use liberal stresses for calculation of stress range, a stress run, without liberal stresses should be taken, to make sure that too many node points are not found over stressed. (This run, without liberal stresses, should not be documented, or the soft file preserved unless specifically required in the project). (3) Displacement: - Displacement for pipes in vertical direction (sag) for sustained condition should be limited to the following - 3 mm for 3”NB and below - 5 mm for all other pipes Although deflection permitted is 5mm one should try to restrict deflection within 2 mm as a good engineering practice. Ideally a line should not lift in expansion condition at any support. If at all it lifts, one should recheck sustained stresses by running a dummy file without the lifting support in the input and ascertain that stresses are still within allowable values. A lift of less than 1 mm may be neglected. Allowable displacement of the pipe in expansion depends on the layout condition. For pipes on pipe rack, the horizontal movement in the perpendicular direction should be limited to 25mm. If the displacement is more, the possibility of fouling with a second pipe or structure should be checked. In axial direction, especially within loops, the displacement can be higher (100 to 120 mm).

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(4) Restraint summary (Loads): - Restraint summary of operating and sustained case will give the loads that would come at a support point/equipment nozzle. Loads on the support point should be practical. One should check for abnormally high expansion loads, which could come on guides or other supports, if supporting is not done properly. For example, two axial stops on a straight line, or a guide immediately after an elbow etc. Nozzle loads should not be higher than allowable values. (5) Spring support loads: - Once restraint summary checking is over, one should check the spring selected by the program. The deflection should be large enough to justify its requirement. If the deflection is very low, one should try to avoid the spring. An ideal spring would have zero displacement at sustained condition i.e. the sustained load is the same as that which would have appeared with a normal rigid support. If the load were different, it would result in push and pull of the pipe in sustained condition. (6) Occasional loading: - Stresses for occasional loading should be restricted to 85%. Deflection and loads due to occasional loading should be checked for its acceptability. It might not be possible to transfer very large magnitude loads to the structure. In such cases, the loads will have to be distributed with larger no. of supports. Guides and stops required for occasional load analysis should not adversely hamper thermal run requirements. A balance has to be made with both these situations. (7) Equipment check: - CAESAR II gives provisions for checking nozzle loads by some of the standard practices. If allowable loads are not available from vendor or MQ/PE, these subroutines wherever applicable can be used. However one should go through the code and understand it before using it. The subroutines are - NEMA SM23 - This covers nozzle load requirements of steam turbine. There are three stages of nozzle load checking, viz. Resultant force and moment imposed on the turbine by each nozzle, Combined resultant of forces and moments of all major nozzles (inlet, outlet, extraction etc), and check of Components of combined forces and moments of all nozzles, in each direction separately. Refer Annexure I, pages 38,39,40,41,42,43 & 44 for details. - API 610 - This code is the most commonly used code for centrifugal pumps. It specifies the minimum requirement for allowable loads. When the loads are more than the values specified in Table 2.1A, then the calculations in APPENDIX F of the code (to check nozzle loads with respect to misalignment) can be used to qualify the piping. This calculation can be done in the subroutine. Refer Annexure I, pages 45,46,47,48,49,50 & 51 for details. - API 617 - This covers nozzle load requirements of centrifugal compressors. Until 1988, nozzle loads for compressors were computed as 1.85 times NEMA SM23 values. Afterwards it has been covered in API 617 APPENDIX G. It has the same three conditions that is followed in NEMA SM23. Refer Annexure I, pages 52 & 53 for details.

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- API 661 - This covers nozzle load requirements of Air Coolers. It gives allowable loads in Figure 8 of the code. Refer Annexure I, pages 54,55,56,57, & 58 for details. - API 560 - This code covers nozzle load requirements for Fired Heaters. Allowable loads are listed in Table 7 of the code. It give loads and movements for both radial and convection terminals in vertical and horizontal directions. Refer Annexure I, pages 59 & 60 for details. - HEI Standards - This code covers requirement for nozzle qualification of Heat exchangers. Refer Annexure I, pages 61 & 62 for details. - WRC 107 - This bulletin covers steps for calculating stresses at nozzle equipment junctions of pressure vessels. This calculation is available in CAESAR II program. Refer Annexure I, pages 63,64,65,66,67,68 & 69 for details.

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4.0



SAMPLE PROBLEM A sample problem is shown below. This system consists of a pump line taking suction from a heat exchanger. The pump has two working situations. The first, case 1 is when the first pump is working and the second is stand by. The second, case 2 is when the first pump is stand by and the second is working. The load cases are as below.

T1 and T2 are the two temperature cases. SUS stands for sustained case, OPE for operating and EXP for expansion case. For the standby pump, the temperature from the valve to pump nozzle is considered as ambient.

Kaux Menu The Kaux menu provides some miscellaneous items.

Kaux Menu

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Review SIFs at Intersection Nodes— Allows the user to run “ what if” tests on the Stress Intensification Factors of intersections.

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Review SIFs at Bend Nodes— Allows the user to run “ what if” tests on the Stress Intensification Factors of selected bends.

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Special Execution Parameters— Allows the user to set options affecting the analysis of the current job. Items covered include ambient temperature, pressure stiffening, displacements due to pressure (Bourdon effect), etc.

Annexure 1 Page 1 of 69

Special Execution Parameters


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Include Piping Input Files— Allows the user to include other piping models in the current model.

Include Piping Files

The same file may be included more than once by highlighting it in the list, then changing the rotation angle (ROTY) or nodal increment (Inc) before clicking the ADD button. Note

Included piping files must be located in the same directory as the main CAESAR II piping file and are limited to names of eight characters or fewer.


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Include Structural Input Files— Allows the incorporation of structural models into the piping model.

Include Structural Files Note

Included structural files must be located in the same directory as the main CAESAR II piping file and are limited to names of eight characters or fewer.


Title

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Hanger Design Control Data— Prompts the user for system - wide hanger design criteria.

Hanger Design Control Data


Spreadsheet Overview In order to input a piping model, one must either open a new or existing piping file from the Main Menu, and then choose Input-Piping. The CAESAR II piping input spreadsheet then appears.

Input Spreadsheet

This spreadsheet is used to describe the piping on an element by element basis. It consists of data fields used to enter information about each piping element and menu commands/ toolbars which can be used to perform a number of supporting operations.


Data Fields The data fields are grouped logically into blocks of related data on the left side of the screen. The right side of the screen offers an auxiliary area, with changing data-fields that support items entered through check boxes (pressing [F12] alternatively displays the various auxiliary screens). The following are the data-field blocks:

Node Numbers

Each element is identified by its end “ node” numbers. Since each input screen represents a piping element, the element end points - the From node and To node - must be entered. These points are used as locations at which information may be entered or extracted. The From node and To node are both required data. Note

CAESAR II can generate both values if the AUTO_NODE_INCREMENT directive is set to other than zero using the Tools-Configure/Setup option of the Main Menu.

Element Lengths

Lengths of the elements are entered as delta dimensions according to the X, Y, Z rectangular coordinate system established for the piping system (note that the Y-axis represents the vertical axis). The delta dimensions DX, DY, and DZ, are the measurements along the X, Y, and Z axes between the From node and To node. In most cases only one of the three cells will be used as the piping usually runs along the global axes. Where the piping element is skewed two or three entries must be made. One or more entries must be made for all elements except “ zero length” expansion joints. Note

When using feet and inches for compound length and length units, valid entries in this (and most other length fields) include formats such as: 3-6, 3 ft. -6 in, and 3-63/16.

Offsets can be used to modify the stiffness of the current element by adjusting its length and the orientation of its neutral axis in 3-D space.


Pipe Section Properties

The element’s outside diameter, wall thickness, mill tolerance (plus mill tolerance is used for IGE/TD/12 piping code only), seam weld (IGE/TD/12 piping code only), corrosion allowance, and insulation thickness are entered in this block. These data carry forward from one screen to the next during the input session and need only be entered for those elements at which a change occurs. Nominal pipe sizes and schedules may be specified; CAESAR II converts these values to actual outside diameter and wall thickness. Outside diameter and wall thickness are required data. Note

Nominal diameters, thicknesses, and schedule numbers are a function of the pipe size specification. ANSI, JIS, or DIN are set via the Tools-Configure/Setup option of the Main Menu.

Operating Conditions: Temperatures and Pressures


Up to nine temperatures and pressures can be specified for each piping element. (The button with the ellipses dots is used to activate a window showing extended operating conditions input). The temperatures are actual temperatures (not changes from ambient). CAESAR II uses these temperatures to obtain the thermal strain and allowable stresses for the element from the material data base. As an alternative, the thermal strains may be specified directly (see the discussion of ALPHA TOLERANCE in the Technical Reference Manual). Thermal strains have absolute values on the order of 0.002, and are unitless. Pressures are entered as gauge values and may not be negative. Each temperature and each pressure entered creates a loading for use when building load cases. Both thermal and pressure data carries forward from one element to the next until changed. Note

CAESAR II uses an ambient temperature of 70° F, unless changed using the Special Execution Parameters Option.

Special Element Information

Special components such as bends, rigid elements, expansion joints and tees require additional information which can be defined in this block. If the element described by the spreadsheet ends in a bend, elbow or mitered joint, the Bend checkbox should be set by double-clicking. This entry opens up the auxiliary data field on the right hand side of the input screen to accept additional data regarding the bend. CAESAR II usually assigns three nodes to a bend (giving ‘near’, ‘mid’, and ‘far’ node on the bend). Double-clicking on the Rigid checkbox (indicating an element that is much stiffer than the connecting pipe such as a flange or valve), opens an auxiliary data field to collect the component weight. For rigid elements, CAESAR II follows these rules: •

When the rigid element weight is entered, i.e. not zero, CAESAR II computes any extra weight due to insulation and contained fluid, and adds it to the user’s entered weight value.

•

The weight of fluid added to a non-zero weight rigid element is equal to the same weight that would be computed for an equivalent straight pipe. The weight of insulation added is equal to the same weight that would be computed for an equivalent straight pipe times 1.75.

•

If the weight of a rigid element is zero or blank, CAESAR II assumes the element is an artificial “ construction element” rather than an actual piping element, so no insulation or fluid weight is computed for that element.

•

The stiffness of the rigid element is relative to the diameter (and wall & thickness) entered. Make sure that the diameter entered on a rigid element spreadsheet is indicative of the rigid stiffness that should be generated.


Auxiliary Data Area The Auxiliary data area is used to display or enter extended data associated with the check box fields. The data in this area can be displayed by single clicking the appropriate box, or by toggling through the screens with the use of the [F12] key. Note

When there is no auxiliary data, an input status screen appears.

Bend Data

This auxiliary screen is used to enter information regarding bend radius, miter cuts fitting wall thickness, or attached flanges. Intermediate node points may be placed at specified angles along the bend, or at the bend mid-point (“ M” ).


Rigid Weight

This auxiliary screen is used to enter the weight of a rigid element. If no weight is entered CAESAR II models the element as a weightless construction element. Note

Rigid weights are entered automatically if the Valve and Flange database is used.

Expansion Joint

This auxiliary screen is used to enter the expansion joint stiffness parameters and effective diameter. For a non-zero length expansion joint, either the transverse or bending stiffness must be omitted. Note

Setting the effective diameter to zero de-activates the pressure thrust load. This method may be used (in conjunction with setting a large axial stiffness) to simulate the effect of axial tie-rods.


Restraints

This auxiliary screen is used to enter data up to four restraints per spreadsheet. Node number and restraint Type are required, all other information is optional (omitting the stiffness entry defaults to “ rigid” ). Restraint types may be selected from the drop list or typed in. Note

Skewed restraints may be entered by entering direction cosines with the type, such as X (0.707,0.0,0.707) for a restraint running at 45o in the X-Z plane.


Displacements

This auxiliary screen is used to enter imposed displacements at up to two nodes per spreadsheet. Up to nine displacement vectors may be entered (load components D1 through D9). If a displacement value is entered for any vector, this direction is considered to be fixed for any other non-specified vectors. Note

Leaving a direction blank for all nine vectors models the system as being free to move in that direction. Specifying “ 0.0” implies that the system is fully restrained in that direction.


Forces

This auxiliary screen is used to enter imposed forces and/or moments at up to two nodes per spreadsheet. Up to nine force vectors may be entered (load components F1 through F9).

Uniform Loads

This auxiliary screen is used to enter up to three uniform load vectors (load components U1, U2 and U3). These uniform loads are applied to the entire current element, as well as


Error Checking, Static Load Cases, & Analysis

Providing Wind Data The only wind load information that is specified in the piping input is the shape factor. It is this shape factor input that causes WIND to be listed as an available load to be analyzed. More wind data is required, however, before an analysis can be made. When WIND is used in the model, CAESAR II makes available the screen to define the extra wind load data. Once defined, this input is stored and may be changed on subsequent entries into the static analysis processor. To specify the wind data needed for the analysis select the tab entitled Wind Load Editor. The screen shown below appears:

Wind Load Specifications

There are three different methods that can be used to generate wind loads on piping systems: 1. ASCE #7 Standard Edition, 1995 2. User entry of a pressure vs. elevation table 3. User entry of a velocity vs. elevation table The appropriate method is selected by placing a value of 1.0 in one of the first three boxes.


Error Checking, Static Load Cases, & Analysis

When defining a pressure or velocity vs. elevation table the user needs to specify only the method and the wind direction on the preceding screen. Upon exiting this screen, the user is prompted for the corresponding pressure or velocity table. If a uniform pressure or velocity is to act over the entire piping system, then only a single entry needs to be made in the table, otherwise the user should enter the pressure or velocity profile for the applicable wind loading. Note

To use the ASCE #7 wind loads, all but the second and third fields should be filled in.

For example, as per ASCE #7, the following are typical basic wind-speed values:

File - Analysis

California and West Coast Areas

-

124.6 ft./sec. ( 85 m.p.h.)

Rocky Mountains

-

132.0 ft./sec ( 90 m.p.h.)

Great Plains

-

132.0 ft./sec ( 90 m.p.h.)

Non-Coastal Eastern United States

-

132.0 ft./sec ( 90 m.p.h.)

Gulf Coast

-

190.6 ft./sec (130 m.p.h.)

Florida-Carolinas

-

190.6 ft./sec (130 m.p.h.)

Miami

-

212.6 ft./sec (145 m.p.h.)

New England Coastal Areas

-

176.0 ft./sec (120 m.p.h.)

Once the load cases (and any wind loads) have been successfully edited, executing the File Analysis command begins the analysis.


Loading Conditions

The checkboxes in this block allow the user to define loadings acting on the pipe. These loads may be individual forces or moments acting at discrete points, distributed uniform loads (which may be specified on force per unit length, or gravitational body forces), or wind loadings (wind loadings are entered by specifying a wind shape factor— the loads themselves are specified when building the load cases. The uniform load and the wind shape factor check boxes will be unchecked on subsequent input screens. This does not mean that the loads were removed from these elements, instead, this implies that the loads do not change on subsequent screens. Note

Uniform loads may be specified in g-values by setting a parameter in the Special Execution Options.

Piping Material

CAESAR II requires the specification of the pipe material’s elastic modulus, Poisson’s ratio, density, and (in most cases) expansion coefficient. The program provides a database containing the parameters for many common piping materials. This information is retrieved by picking a material from the drop list, by entering the material number, or by typing any or all of the material name and then picking it from the match list. (The coefficient of expansion does not appear on the input screen, but it can be reviewed during error checking.) Note that materials 18 and 19 represent cold spring properties, cut short and cut long respectively; material 20 activates CAESAR II’s orthotropic model for use with materials such as fiberglass reinforced plastic pipe. Material 21 permits a totally user defined material. Using a material with a number greater than 100 permits the use of allowable stresses from the database.


Allowable Stresses

This auxiliary screen is used to select the piping code (from a drop list) and to enter any data required for the code check. Allowable stresses are automatically updated for material, temperature and code if available in the material database. Material Fatigue Curve data may be entered by clicking on the Fatigue Curve button. This brings up a dialog where stress vs. cycle data (up to 8 points per curve) may be entered for Butt Weld and Fillet Weld components.


Material Elastic Properties

This block is used to enter or override the elastic modulus and Poisson’s ratio of the material, if the value in the database is not correct. These values must be entered for Material type 21 (user specified). Note

Material properties in the database may be changed permanently using the CAESAR II material database editor.

Densities

The densities of the piping material, insulation, and fluid contents are specified in this block. The piping material density is a required entry and is usually extracted from the material data base. Fluid density can optionally be entered in terms of specific gravity, if convenient, by following the input immediately with the letters: SG, e.g. 0.85SG (there can be no spaces between the number and the SG). Note

If an insulation thickness is specified (in the pipe section properties block) but no insulation density is entered, CAESAR II defaults to the density of calcium silicate.


Plot Plot

This menu option provides two types of graphics— the traditional CAESAR II graphics, as well as a "sneak preview" of CAESAR II’s new 3-D graphics library. When selected, these graphics will replace CAESAR II’s traditional graphics.

Pan

The model may be panned left, right, up, or down by using the [Home], [End], [PgUp], or [PgDn] keys respectively.

Zoom In

Zooming can be accomplished by clicking the mouse and dragging a box around the desired zoom area, or by using the + and - keys.

Zoom Out

The model can be rotated by pressing the arrow keys.

X-Axis Rotation Y-Axis Rotation Z-Axis Rotation

Note

Mouse-driven Panning, Zooming, and Rotating are also available by right-clicking the mouse and selecting an action from the popup menu. Pressing [ESC] or re-selecting from the popup menu exits the Panning, Zooming, or Rotating mode.


Additional commands are available for displaying, highlighting, or labeling the plot. Some of these are •

Volume— Toggles between volume and centerline representation while in line drawing mode.

Render

•

Render— Renders the piping model.

Wire Frame

•

Wire Frame— Draws the piping model in wire frame.

Line Drawing

•

Line Drawing— Switches to line drawing mode from render or wire frame.

•

Highlight— Changes drawing color based on element attributes.

•

Range— Displays elements based on node ranges.

•

X— View along X-axis.

•

Y— View along Y-axis.

•

Z— View along Z-axis.

•

Southeast— View in Southeast isometric mode.

•

4— View in all four modes simultaneously.

Restraints

•

Restraints— Displays non-anchor, non-hanger restraints.

Anchors

•

Anchors— Display anchors.

•

Hangers— Displays hangers.

Forces

•

Forces— Labels imposed forces.

Displacements

•

Displacements— Labels imposed displacements.

Nozzles

•

Nozzles— Display flexible nozzles.

Nodes

•

Nodes— Labels plot with node numbers.

Length

•

Length— Labels plot with element lengths.

Volume

Highlight Range X Y Z Southeast 4

Hangers


View Spreadsheet Print

The View Spreadsheet command allows the user to maintain both the plot and the spreadsheet on the screen simultaneously. The current plot may be output to the clipboard, a bitmap (.BMP) file, or a printer through use of the Edit-Copy, File-Save As Bitmap, or File-Print commands, respectively.

Print Preview


List Input Format Previous Element

Note

•

[Pg Dn], [Pg Up], Ctrl +[Home], Ctrl +[End]— Allow the user to move throughout the elements of the model.

Unlike the Continue command, [Pg Dn] does not create a new element once the end of the model is reached.


Stress Intensification Factors/Tees

This auxiliary screen is used to enter stress intensification factors, or fitting types at up to two nodes per spreadsheet. If components are selected from the drop list, CAESAR II automatically calculates the SIF values as per the applicable code (unless overridden by the user). Certain fittings and certain codes require additional data as shown. Fields are enabled as appropriate for the selected fitting.


Flexible Nozzles

This auxiliary screen is used to describe flexible nozzle connections. When entered in this way, CAESAR II automatically calculates the flexibilities and inserts them at this location. CAESAR II calculates nozzle loads according to WRC 297, API 650 or BS 5500 criteria.


Hangers

This auxiliary screen is used to describe hanger installations. Hanger data may be fully completed by the user, or the hanger may be designed by CAESAR II. In this case, two special load cases are run, the results of which are used as design parameters which are used to select the springs from the user specified catalog. Note

CAESAR II provides catalogs for 20 different spring hanger vendors.


Error Checking Static analysis cannot be performed until the error checking portion of the piping preprocessor has been successfully completed. Only after error checking is completed are the required analysis data files created. Similarly, any subsequent changes made to the model input is not reflected in the analysis unless error checking is rerun after those changes have been made. CAESAR II does not allow an analysis to take place if the input has been changed and not successfully error checked. Start Run Batch Run

Error Checking can only be done from the input spreadsheet, and is initiated by executing the Start Run or Batch Run commands from the toolbar, menu or the Quit options menu (the Quit options menu appears upon closing the spreadsheet).

Piping Quit Options Menu

The Start Run command exits the input processor, starts the error checking procedure, and returns the user to the Main Menu for further action. The Batch Run command causes the program to check the input data, analyze the system, and present the results without any user interaction. The assumptions are that the loading cases to be analyzed do not need to change and that the default account number (if accounting active) is correct. These criteria are usually met after the first pass through the analysis. Batch processing focuses the user’s attention on the creation of input and the review of output by expediting the steps in between. Once invoked, the error checker reviews the CAESAR II model and alerts the user to any possible errors, inconsistencies, or noteworthy items. These items are presented to the user as Errors, Warnings, or Notes. Errors are flagged when there is a problem with the model due to which analysis cannot continue. An example of this would be if no length is defined for a piping element. These errors are also called fatal errors, since they are fatal to the analysis, and must be corrected before continuing.


Fatal Error Dialog

Warnings are flagged whenever there is a problem with a model which can be overcome using some assumptions. An example of this would be if an element’s wall thickness is insufficient to meet the minimum wall thickness for the given pressure (hoop stress). Warnings need not be corrected in order to get a successful analysis, but all warnings should be reviewed carefully by the user as they are displayed.


Warning Dialog

Note Dialog The third category of alert is the informational note. These messages simply inform the user of some noteworthy fact related to the model. An example of a note may be a message informing the user of the number of hangers to be designed by the CAESAR II program. For notes, there is nothing for the user to “correct.”


Building Static Load Cases Analysis Statics

The first step in the analysis of an error-checked piping model is the specification of the static load cases. This is done by selection of the Analysis-Static options from the CAESAR II Main Menu (the piping input file must have successfully gone through error checking before this option can be chosen). A discussion of CAESAR II load cases is included at the end of this chapter. Please refer to it for a description of how the load cases are built.

Upon entering the static load case editor, a screen appears which lists all of the available loads that are defined in the input, the available stress types, and the current load cases offered for analysis. If the job is entering static analysis for the first time, CAESAR II presents a list of recommended load cases. If the job has been run previously, the loads shown are those saved during the last session. A typical load case editor screen is shown below:

Load Case Editor

The user can define up to ninety-nine load cases. Load cases may be edited by clicking on a line in the Load List area. Only the load components listed in the upper left-hand portion of the screen may be specified in the load cases. The entries must be identical to what is shown on the screen. Available stress types are specified at the end of the load case entry in parentheses. Stress type determines the stress calculation method and the allowable stress to use (if any).


Load cases may be built through drag and drop actions. Dragging a load component from the Loads Defined in Input list to a line on the load list automatically adds that load component to the load case, if it is not already included. Dragging a stress type from the Available Stress Type list to a load case in the list changes the stress type for that case. Highlighted basic load cases may be dragged down to be added to algebraic combination cases (if necessary, CAESAR II prompts for combination type DS, FR, or ST). Note

Defining a fatigue (FAT) stress type for a load case automatically displays a field in which the number of anticipated load cycles for that load case can be entered.

All basic (non-combination) load sets must all be specified before any algebraic combinations may be declared. This rule holds true for user defined and edited load cases. The following commands are available on this screen: •

Edit-Insert—This command inserts a blank load case preceding the currently selected line in the load list. If no line is selected, the load case is added at the end of the list. Load cases are selected by clicking on the number to the left of the load case.

Edit - Delete

•

Edit-Delete—This command deletes the currently selected load case.

File - Analysis

•

File Analysis—This command accepts the load cases and runs the job.

Recommend

•

Recommend—This command allows the user to replace the current load cases with the CAESAR II recommended load cases.

Load Cycles

•

Load Cycles—This button alternatively hides or displays the Load Cycles field in the Load Case list. Entries in these fields are only valid / required for load cases defined with the fatigue stress types.

Edit - Insert

Note

Load cases may be built through drag and drop actions. Dragging a load component from the Loads Defined in Input list to a line on the load list automatically adds the load component to the load case, if it is not already included. Dragging a stress type from the Available Stress Type list to a load case in the list changes the stress type for that case. Highlighted basic load cases may be dragged down to be added to algebraic combination cases (if necessary, CAESAR II prompts for combination type DS, FR, or ST).


Static Output Screen


Notes on CAESAR II Load Cases Definition of a Load Case In CAESAR II terms, a load case is a group of piping system loads that are analyzed together, i.e., that are assumed to be occurring at the same time. An example of a load case is an operating analysis composed of the thermal, deadweight, and pressure loads together. Another is an as-installed analysis of deadweight loads alone. A load case may also be composed of the combinations of the results of other load cases; for example, the difference in displacements between the operating and installed cases. No matter what the contents of the load case, it always produces a set of reports in the output which list restraint loads, displacements and rotations, internal forces, moments, and stresses. Because of piping code definitions of calculation methods and/or allowable stresses, the load cases are also tagged with a stress category. For example, the combination mentioned above might be tagged as an EXPansion stress case. The piping system loads which compose the basic (non-combination) load sets relate to various input items found on the piping input screen. The table below lists the individual load set designations, their names and the input items which make them available for analysis. Designation

Name

Input items which activate this load case

W

Deadweight

Pipe Density, Insulation Density (with insulation thickness), Fluid Density, or Rigid Weight

WNC

Weight

Pipe Density, Insulation Density (with insulation thickness), Rigid Weight

T1

Thermal Set 1

Temperature #1

T2

Thermal Set 2

Temperature #2

T3

Thermal Set 3

Temperature #3

T9

Thermal Set 9

Temperature #9

P1

Pressure Set 1

Pressure #1

P2

Pressure Set 2

Pressure #2

P3

Pressure Set 3

Pressure #3

P9

Pressure Set 9

Pressure #9

D1

Displacements Set 1 Displacements (1st Vector)

D2

Displacements Set 2 Displacements (2nd Vector)

D3

Displacements Set 3 Displacements (3rd Vector)

. . .

. . .


. . . D9

Displacement Set 9

Displacements (9th Vector)

F1

Force Set 1

Forces/Moments (1st Vector), cold spring (Material # 18 or 19), and spring initial loads

F2

Force Set 2

Forces/Moments (2nd Vector)

F3

Force Set 3

Forces/Moments (3rd Vector)

F9

Force Set 9

Forces/Moments (9th Vector)

WIN1

Wind Load 1

Wind Shape Factor

WIN2

Wind Load 2

Wind Shape Factor

WIN3

Wind Load 3

Wind Shape Factor

WIN4

Wind Load 4

Wind Shape Factor

WAV1

Wave Load 1

Wave Load On

WAV2

Wave Load 2

Wave Load On

WAV3

Wave Load 3

Wave Load On

WAV4

Wave Load 4

Wave Load On

U1

Uniform Loads

Uniform Loads (1st Vector)

U2

Uniform Loads

Uniform Loads (2nd Vector)

U3

Uniform Loads

Uniform Loads (3rd Vector)

. . .

Note

Available piping system loads are displayed on the left hand side of the Static Load Case screen.

Basic load cases may consist of a single load such as WNC for an as-installed weight analysis, or they may include several loads added together such as W+T1+P1+D1+F1 for an operating analysis. The stress categories: SUStained, EXPansion, OCCasional, OPErating, and FATigue are specified at the end of the load case definition. The complete definition of the two examples are: WNC (SUS) and W+T1+P1+D1+F1 (OPE). Each basic load case is entered in this manner in a list for analysis. Note

Available stress types are displayed in the lower left hand side of the Static Load Case screen.

Results of the basic load cases may be combined using algebraic combination cases. These algebraic combinations are always entered following the last of the basic load cases. Combinations of basic load cases are designated using the prefix DS, FR or ST to indicate whether the combination is done at the displacement, force, or stress level respectively followed by a number indicating the order of the basic load case in the load list. The two former combinations (DS and FR) are done algebraically (signs are considered), while the


last (ST) is combined absolutely. Combination load cases should also have stress types assigned. Note

Summing load cases at the DS level is important when signs must be considered, such as for an EXPansion case. Summing load case results at the ST level is important when stresses must be combined absolutely, as for an OCCasional case.

Forces and moments are computed from displacements, and stresses are computed from forces and moments. Displacement combinations therefore also have force and stress results to review, while stress combinations only have stress results to review. Note

All load cases with stress type FATigue must have their expected number of Load Cycles specified.

The following family of load cases provides a valid example of algebraic combinations. Load Case

Designation

Comments

1

W+T1+P1+D1+F1 (OPE)

The operating Load Case

2

W+P1+F1 (SUS)

The installed Load Case (for sustained stress calculations)

3

U1(OCC)

A uniform Load Case modeling a seismicload

4

DS1-DS2(EXP)

The difference between the displacements of Load Case #1 (operating) minus the displacements of Load Case #2 (installed); the displacement range of the piping; used to calculate expansion stress range going from cold to hot.

5

ST2+ST3(OCC)

The stresses from Load Case #2 (sustained) plus the stresses from Load Case #3 (occasional); used to compare the occasional stresses with their allowables.

CAESAR II permits the specification of up to ninety-nine load cases for analysis. In the rare situation where more cases are required, the model should be copied to a new file in order to specify the additional load cases.

Recommended Load Cases When the user first enters the static load case editor CAESAR II recommends, based on the loads defined in the model, three types of load cases: Operating, Sustained, and Expansion (but not occasional).


Operating load cases represent the loads acting on the pipe during hot operation, including both primary (weight pressure, and force) loadings and secondary (displacement and thermal) loadings. Operating cases are used to find hot displacements for interference checking, and hot restraint and equipment loads. Generally when recommending operating load cases, CAESAR II combines weight, pressure case #1, and force set #1, with each of the thermal load cases (displacement set #1 with thermal set #1, displacement set #2 with thermal set #2, etc...). Sustained load cases represent the primary (force-driven loadings acting on the pipe), i.e., weight and pressure alone. This usually coincides with the cold (as-installed) load case. Sustained load cases are used to satisfy the code sustained stress requirements, as well as to calculate as-installed restraint and equipment loads. Sustained load cases are generally built by combining weight with each of the pressure and force sets. Expansion load cases represent the range between the displacement extremes (usually between the operating and sustained cases). Expansion load cases are used to meet expansion stress requirements. Most users will specify only one temperature and one pressure. Such input would simplify the recommended cases to: Case # 1

W+D1+T1+P1+F1 (OPE) ....OPERATING

Case # 2

W+P1+F1 (SUS)....SUSTAINED LOAD CASE

Case # 3

DS1-DS2 (EXP)....EXPANSION LOAD CASE

The user should review any load recommendations made by CAESAR II. Note

CAESAR II does not recommend any occasional load cases. Definition of these are the responsibility of the user.

If these recommended load cases do not satisfy the analysis requirements, they may always be deleted or modified. Conversely, the load cases may always be reset to the program’s recommended set at any time.

Recommended Load Cases for Hanger Selection If spring hangers are to be designed by the program, two additional load cases must first be analyzed in order to obtain the data required to select a variable support. The two basic requirements for sizing hangers are the deadweight carried by the hanger (hot load) and the range of vertical travel to be accommodated. The first load case (traditionally called “Restrained Weight”) consists of only deadweight and applied forces (W+F1). For this analysis CAESAR II includes a rigid restraint in the vertical direction at every location where a hanger is to be sized. The load on the restraint from this analysis is the deadweight that must be carried by the support in the hot condition. For the second load case, the hanger is replaced with an upward force equal to the calculated hot load, and an operating load case is run. This load case (traditionally called “Free Thermal”) includes the deadweight and thermal effects, the first pressure set (if defined), any displacements, and the applied forces (W+D1+T1+P1+F1). The vertical displacements of the hanger locations, along with the previously calculated deadweights are then passed on to the hanger selection routine. Once the hangers are sized, the added forces are removed and replaced with the selected supports along with their pre-loads (cold loads). CAESAR II then continues


with the load case recommendations as defined above. A typical set of recommended load cases for a single operating load case spring hanger design appears as follows: Case # 1 W+F1 ....WEIGHT FOR HANGER LOADS Case # 2 W+D1+T1+P1+F1 ....OPERATING FOR HANGER TRAVEL Case # 3 W+D1+T1+P1+F1 (OPE) ...OPERATING (HGRS. INCLUDED Case # 4 W+P1+F1 (SUS) ....SUSTAINED LOAD CASE Case # 5 DS3-DS4 (EXP) ....EXPANSION LOAD CASE These hanger sizing load cases (#1 & #2) supply no information to the output reports other than the data found in the hanger tables. Note how cases 3, 4, & 5 match the recommended load cases for a standard analysis with one thermal and one pressure defined. Also notice how the displacement combination numbers in case 5 have changed to reflect the new order. If multiple temperatures and pressures existed in the input, they too would appear in this set after the second spring hanger design load case. Two other hanger design criteria also affect the recommended load cases. If the “actual cold loads” for selected springs are to be calculated, one additional load case (WNC+F1) would appear before case #3 above. If the piping system’s hanger design criteria is set so that the proposed springs must accommodate more than one operating condition, other load cases must additionally appear before the case #3 above. An extra hanger design operating load case must be performed for each additional operating load case used to design springs. Refer to the discussion of the hanger design algorithm for more information on these options.


data bases (or compute unity checks on angles using the 1977 code) will generate an error message and the program will abort. Users are urged to consult the applicable AISC manuals when using this program.

NEMA SM23 (Steam Turbines) There are two types of force/moment allowables computed during a NEMA run: •

Individual nozzle allowables.

•

Cumulative equipment allowables.

Each individual suction, discharge, and extraction nozzle must satisfy the equation: 3F + M < 500De Where: F

=

resultant force on the particular nozzle.

M =

resultant moment on the particular nozzle.

De =

effective nominal pipe size of the connection.

A typical discharge nozzle calculation is shown as follows: INDIVIDUAL NOZZLE CALCUATIONS NOZZLE

NODE COMPONENTSRESULTANTSVALUES/ALLOWABLES (lbs. & ft.lb.)(lbs. & ft.lb.)

EXHAUST

50

FX = 1923F + M = 1216 FY= -7 F= 192

FZ = 11

500*(used) = 4,000

MX = -369

% OF ALLOW. = 30.40 MY= 522 M= 640

MZ = -39 The cumulative equipment allowables require that forces and moments on all turbine connections, resolved at the intersection of the largest nozzle and the equipment centerline, be within a certain multiple of Dc; where Dc is the diameter of an opening whose area is equal to the sum of the areas of all of the individual equipment connections. A typical turbine cumulative (summation) equipment calculation is shown as follows: SUMMATION CALCUATIONS DIAMETER DUE TO EQUIVALENT NOZZLE AREA, DC =

8.944in.

NOZZLE LOADS SUMMATIONSALLOWABLES % OF ALLOW.STATUS lbs.&ft.lb.) SFX SFY SFZ FC(RSLT) SMX

= = = = =

84 -74 -82 138 -447

50*DC = 125*DC = 100*DC =

447 18.79 1118 6.62 894 9.17

250*DC =

2236 20.00


SMY SMZ MC(RSLT) FC + MC/2

= = = =

170 631 792 535

125*DC = 125*DC =

1118 56.51 1118 56.51

125*DC =

1118 47.85

SFX, SFY, and SFZ are the respective components of the forces from all connections resolved at the discharge nozzle. FC(RSLT) is the result of these forces. SMX, SMY and SMZ are the respective components of the moments from all connections resolved at the discharge nozzle. Dc is the diameter of the equivalent opening as discussed above.

NEMA Turbine Example Consider a turbine where node 35 represents the inlet nozzle and node 50 represents the outlet nozzle. The output from a CAESAR II analysis of this piping system includes the forces and moments acting on the pipe elements that attach to the turbine: NODE FX

FY FZ

MX

30

-108 -49 -93 73

35

108

50

-192 7

55

192

67

93

MY

MZ

188

603

162 -47

-481

-11 369 -522 39

-63 11

78

117

-56

To find the forces acting on the turbine at points 35 and 50 simply reverse the sign of the forces that act on the piping: LOADS ON TURBINE @ 35 -108

-67

-93

-162

47

481

LOADS ON TURBINE @ 50 192

-7

11

-369

522 -39

There are two input spreadsheets for the NEMA turbine and they appear as follows. Applied loads should be entered in global coordinates or extracted directly from the CAESAR II output file (using the on-screen button).


NEMA Input Spreadsheet #1


NEMA Input Inlet Nozzle


NEMA Input Exhaust Nozzle

The two page NEMA output report for the above turbine example shows that the turbine passed. The highest summation load is only 56% of the allowable. If the turbine had failed, the symbol **FAILED** would have appeared in the “ STATUS” column opposite to the load combination that was excessive.




API 610 (Centrifugal Pumps) In August of 1995, API released the 8th edition of API 610 for centrifugal pumps for general refinery service. The API 610 load satisfaction criteria is outlined below: If clause F.1.1 is satisfied, then the pump is O.K. Clause F.1.1 states that the individual component nozzle loads must fall below the allowables listed in the Nozzle Loadings table (Table 2) shown below:

If clause F.1.1 is NOT satisfied, but clauses F.1.2.1, F.1.2.2, and F.1.2.3 ARE satisfied then the pump is still O.K. Clause F.1.2.1 states that the individual component forces and moments acting on each pump nozzle flange shall not exceed the range specified in Table 2 by a factor of more than 2. Referring to the API 610 report, the user can see if F.1.2.1 is satisfied by comparing the Force/Moment Ratio to 2. If the ratio exceeds 2, the nozzle status is reported as “ FAILING” . The F.1.2.2 and the F.1.2.3 requirements give equations relating the resultant forces and moments on each nozzle, as well as on the pump base point respectively. The requirements of these equations, and whether or not they have satisfied API 610, are shown on the bottom of the report. The following example is taken from the API 610 code and shows the review of an overhung end-suction process pump in English units. The three CAESAR II input screens are shown, followed by the program output.


API 610 Input Data


API 610 Suction Nozzle


API 610 Discharge Nozzle


CAESAR II VERSION : 3.24 API 610 (8th Edition)File : APITST8A Date : FEB 28,1997 User Entered Description :Time : 11:31 am API-610 8TH example F.5.1.1 from page F-4. Note, API input transformed into CAESAR II global coordinate system for input. Node # OrientationNominal Diameter Suction Nozzle

1 End10

Discharge Nozzle 4 Top8 Table 2 Allowable ( ratio ) = 2.00 Pump Axis is in the X direction. (Local Coordinates) SuctionTable 2 Force & Moment Status Values Ratios X Distance = 10.5 in. Y Distance = 0.0 in. Z Distance = 0.0 in. X Force = 2900.0 lb. 1500 1.93 Passed Y Force =

0.0 lb. 1200 0.00 Passed

Z Force = -1,990.0 lb. 1,000 1.99 Passed X Moment =- 1,000.0 ft.lb. 3,700 0.27 Passed Y Moment = -3,599.0 ft.lb. 1,800 2.00 Passed Z Moment =- 5,500.0 ft.lb. 2,800 1.96 Passed (Local Coordinates)DischargeTable 2Force & MomentStatus Values Ratios X Distance =

0.0 in.

Y Distance = -12.2 in.


Z Distance =

15.0 in.

X Force = 1,600.0 lb. 850 1.88 Passed Y Force =

-100.0 lb. 700 0.14 Passed

Z Force = 1,950.0 lb. 1100 1.77 Passed X Moment =

500.0 ft.lb. 2,600 0.19 Passed

Y Moment =-2,500.0 ft.lb. 1,300 1.92 Passed Z Moment =-3,600.0 ft.lb. 1,900 1.89 Passed Check of Condition F.1.2.2 Requirement Status (FRSa/1.5FRSt2) + (MRSa/1.5MRSt2) = 1.952 < or = 2.00 Passed (FRDa/1.5FRDt2) + (MRDa/1.5MRDt2)= 1.919 < or = 2.00 Passed Check of Condition F.1.2.3 Requirement Status 1.5 ( FRSt2 + FRDt2 ) = 5,640. > 4,501. (FRCa) Passed 2.0 ( MZSt2 + MZDt2 ) = 6,200. >-2,358. (MYCa) Passed 1.5 ( MRSt2 + MRDt2 ) = 12,750. > 8,180. (MRCa) Passed Overall Pump Status ** PASSED **


Vertical In-Line Pumps Note that on the first screen there is a check box for a vertical in-line pump. This is to be used when the pump is the vertical in-line type supported only by the attached piping. API states that if this is the case then 2.0 times the loads from Table 2 can be used. However, even if the pump fails the 2.0 Table 2 criteria, it may still pass. If the principal stress on the nozzle is less than 6,000 psi, then that nozzle passes. If the principal stress on either nozzle is greater than 6,000 psi, the overall status will be reported as “ Failed.” In API 610 there is an example problem which illustrates the way that the stresses are computed on these in-line pump nozzles. The two basic equations for determining stress are •

Normal stresses (s) = Force / Area + Moment / Section Modulus

•

Shear Stresses (t) = Force / Area + Torque * distance / J

Where J is the polar moment of inertia. In equation number 2, both terms of the equation will always add together. On the other hand, the Force/Area term in equation 1 will depend on the sign of the force (tension or compression) that the user enters in the force and moment spreadsheet. The sign of the force is determined from the user-entered Centerline Direction Cosine, which for vertical in-line pumps should be entered in the direction extending from the discharge to the suction nozzle. The distances that are usually entered for pedestal mounted pumps can be left blank since they are not used.


API 617 (Centrifugal Compressors) The requirements of this standard are identical to those of NEMA SM-23 (1991), except that all of the NEMA allowables are increased by 85%. API 617 Allowables = 1.85 * NEMA SM-23 Allowables The input screens for this evaluation are shown below:

API 617 Input


API 617 Suction/Discharge Input


API 661 (Air Cooled Heat Exchangers) This calculation covers the allowed loads on the vertical, co-linear nozzles (item 9 in the figure) found on most single, or multi-bundled air cooled heat exchangers. The several figures from API 661 illustrate the type of open exchanger body analyzed by this standard.

API 661 Heat Exchangers

The input for API 661 is self-explanatory. The “ Heat Exchangers” figure and the Resultant Force/Multiplier inputs for Spreadsheet #1 are optional (default equals 1). The two requirements for API 661 to be satisfied are as follows: 5.1.11.1 - “ Each nozzle in the corroded condition shall be capable of withstanding the moments and forces defined in Heat Exchangers figure.” 5.1.11.2 - The sum of the forces and moments on each fixed header (i.e. each individual bundle) will be less than 1,500 lb. transverse to the bundle, 2,500 lb axial to the bundle, and 3,000 pound axial on the nozzle centerline. The allowed moments are 3,000, 2,000,


and 4,000 ft.lb. respectively. “ This recognizes that the application of these moments and forces will cause movement and that this movement will tend to reduce the actual loads.”

API 661 Input Data


API 661 Inlet Nozzle Data


API 661 Outlet Nozzle Data


A typical API 661 report is shown as follows: Y Distance =18.0 X Force

=100.0

Y Force

1280.

0.08

PASSED

=-302.0 3,000.

-0.10

PASSED

Z Force

=50.0

1,800.

0.03

PASSED

X Moment

=203.0

2,250.

0.09

PASSED

Y Moment

=300.0

4,500.

0.07

PASSED

Z Moment

=2,300.01,650.

1.39

FAILED

Discharge

Table 3 Force & MomentStatus Values Ratios

Y Distance =0.0 X Force

=0.0

1,280.

0.00

PASSED

Y Force

=0.0

3,000.

0.00

PASSED

Z Force

=0.0

1,800.

0.00

PASSED

X Moment

=0.0

2,250.

0.00

PASSED

Y Moment

=0.0

4,500.

0.00

PASSED

Z Moment

=0.0

1,650.

0.00

PASSED

Resultant Force/Moment Check :

Resultant

Table AllowableRatios

Status

X Force

=100.0

2,250.

0.04

PASSED

Y Force

=-302.0

4,500.

0.07

PASSED

Z Force

=50.0

3,750.

0.01

PASSED

X Moment

=278.0

4,500.

0.06

PASSED

Y Moment

=300.0

6,000.

0.05

PASSED

Z Moment

=2,150.0

3,000.

0.72

PASSED

Overall Loading Status

**

FAILED **.


API 560 (Fired Heaters for General Refinery Services) This module of the CAESAR II Rotating Equipment program provides a method for evaluating the allowable loads on Fired Heaters. Input consists of the tube nominal diameter and the forces and moments acting on the tube, as shown in the figure below:

API 560 Input Data


Upon execution of the analysis, CAESAR II compares the input forces and moments to the allowables as published in API 560. Example output is shown below.

API 560 Equipment Report


Heat Exchange Institute Standard For Closed Feedwater Heaters This module of the CAESAR II Rotating Equipment program provides a method for evaluating the allowable loads on shell type heat exchanger nozzles. Section 3.14 of the HEI bulletin discusses the computational methods utilized to compute these allowable loads. The method employed by HEI is a simplification of the WRC 107 method, in which the allowable loads have been linearized to show the relationship between the maximum permitted radial force and the maximum permitted moment vector. If this relationship is plotted (using the moments as the abscissa and the forces as the ordinate), a straight line can be drawn between the maximum permitted force and the maximum permitted moment vector, forming a triangle with the axes. Then for any set of applied forces and moments, the nozzle passes if the location of these loads falls inside the triangle. Conversely, the nozzle fails if the location of the loads falls outside the triangle. The CAESAR II HEI output has been modified to include both the plot of the allowables and the location of the current load set on this plot. The HEI bulletin states that the effect of internal pressure has been included in the combined stresses; however, the effect of the pressure on the nozzle thrust has not. This requires combination with the other radial loads. CAESAR II automatically computes the pressure thrust and adds it to the radial force if the Add Pressure Thrust checkbox is checked. A sample input for the HEI module is shown below. Note that since the pressure is greater than zero, a pressure thrust force will be computed and combined with the radial force.


HEI Nozzle/Vessel Input


WRC 107 (Vessel Stresses) The Welding Research Council Bulletin 107 (WRC 107) has been used extensively since 1965 by design engineers to estimate local stresses in vessel/attachment junctions. Note

There are three editions of WRC 107 available from the program; the default is set by the user in the Configure-Setup option.

WRC 107 Bulletin provides an analytical tool to evaluate the vessel stresses in the immediate vicinity of a nozzle. This method can be used to compute the stresses at both the inner and outer surfaces of the vessel wall, and report the stresses in the longitudinal and circumferential axes of the vessel/nozzle intersection. The convention adopted by WRC


107 to define the applicable orientations of the applied loads and stresses for both spherical and cylindrical vessels are shown in the figure. M

M TAXIS V (or V ) 1

C

B

A V (or V ) 2

T

V L

L

VC

A

Upper

B C

C

Lower

M LAXIS

M CAXIS

M 1AXIS (or M ) C

P AXIS

P AXIS

M 2AXIS (or M ) L

M AXIS 1

A

A B

B M LAXIS

M2AXIS

M CAXIS

D

D

C

C

SPHERICAL SHELLS

CYLINDRICAL SHELLS

To Define WRC Axes: 1) P-axis: Along the Nozzle centerline and positive entering the vessel. 2) M1-axis: Perpendicular to the nozzle centerline along convenient global axis. 3) M2-axis: Cross the P-axis into the M1 axis and the result is the M2-axis.

To Define WRC Axes: 1) P-axis: Along the Nozzle centerline and positive entering the vessel. 2) MC-axis: Along the vessel centerline and positive to correspond with any parallel global axis. 3) M2-axis: Cross the P-axis with the MC axis and the result is the ML-axis.

To Define WRC Stress Points: u-upper, means stress on outside of vessel wall at junction. l-lower, means stress on inside of vessel at junction. A-Position on vessel at junction, along negative M1 axis. B-Position on vessel at junction, along positive M1 axis. C-Position on vessel at junction, along positive M2 axis. D-Position on vessel at junction, along negative M2 axis.

To Define WRC Stress Points: u-upper, means stress on outside of vessel wall at junction. l-lower, means stress on inside of vessel at junction. A-Position on vessel at junction, along negative MC axis. B-Position on vessel at junction, along positive MC axis. C-Position on vessel at junction, along positive ML axis. D-Position on vessel at junction, along negative ML axis. Note: Shear axis “ VC” is parallel, and in the same direction as the bending axis “ ML” . Shear axis “ VL” is parallel, and in the opposite direction as the bending axis “ MC” . WRC Axes Orientation

It has also been a common practice to use WRC 107 to conservatively estimate vessel shell stress state at the edge of a reinforcing pad, if any. The stress state in the vessel wall when the nozzle has a reinforcing pad can be estimated by considering a solid plug, with an outside diameter equal to the O.D. of the reinforcing pad, subjected to the same nozzle loading.


Note

Before attempting to use WRC 107 to evaluate the stress state of any nozzle/vessel junction, the user should always make sure that the geometric restrictions limiting the application of WRC 107 are not exceeded. These vary according to the attachment and vessel types. The user is referred to the WRC 107 bulletin directory for this information.

The WRC 107 method should probably not be used when the nozzle is very light or when the parameters in the WRC 107 data curves are unreasonably exceeded. Output from the WRC 107 program includes the figure numbers for the curves accessed, the curve abscissa, and the values retrieved. The user is urged to check these outputs against the actual curve in WRC 107 to get a “ feel” for the accuracy of the stresses calculated. For example, if parameters for a particular problem are always near or past the end of the figures curve data, then the calculated stresses may not be reliable. The WRC 107 program can be activated by selecting Analysis - WRC 107 from the Main Menu. The user may be prompted to enter a job name, and then the following data entry screen appears:

Analysis - WRC 107

The input data is accumulated by the processor in six spreadsheets. The first sheet is a title block, the second and third sheets collect the vessel and the nozzle (attachment) geometry data, respectively. The user only needs to define two vectors specified on the geometry data sheets. The first vector defines the direction of the centerline of the vessel. The sec-


ond vector defines the direction of the piping/nozzle orientation, with the positive direction of this vector pointing from the nozzle connection towards the vessel centerline.

Vessel Data


Nozzle Data

The nozzle loading is specified on the last three spreadsheets, according to specific load cases, which include sustained, expansion and occasional cases. These loads are found in the CAESAR II output restraint load summary under the corresponding load cases or may be extracted from the static output files automatically by pressing the Get Loads From Output File button.


Nozzle Loads (SUS)

The WRC 107 specific input coordinate system has been incorporated into the program, so loads should be entered in global orientation. Notice that the curves in WRC Bulletin 107 cover essentially all applications of nozzles in vessels or piping; however, should any of the interpolation parameters, i.e. Beta, etc. fall outside the limits of the available curves, some extrapolation of the WRC method must be used. The current default is to use the last value in the particular WRC table. If one wishes to control the extrapolation methodology interactively, you may do so by changing the WRC 107 default from “ USE LAST CURVE VALUE” to “ INTERACTIVE CONTROL” on the Computation Control tab page located inside the Configure-Setup module of the Main Menu. After entering all data, the WRC 107 analysis may be initiated through the Analyze-WRC 107 menu option. Any errors or warnings are reported in their own tab; double-clicking on them returns the user to the appropriate field. Output reports may be viewed at the terminal or printed.

WRC 107 Stress Summations Because the stresses computed by WRC 107 are highly localized, they do not fall immediately under the B31 code rules as defined by B31.1 or B31.3. The Appendix 4-1 of ASME Section VIII, Division 2 (“ Mandatory Design Based on Stress analysis” ) does however provide a detailed approach for dealing with these local stresses. The analysis procedure outlined in the aforementioned code is used in CAESAR II to perform the stress evalua-


tion. In order to evaluate the stresses through an elastic analysis, three stress combinations (summations) must be made: •

Pm

•

Pm + P l + P b

•

Pm + P l + Pb + Q

Where Pm is defined as the general membrane stress due to internal pressure removed from discontinuities, and can be estimated for the vessel wall from the expression (PD) / (4t) for the longitudinal component and (PD) / (2t) for the hoop component, where P is the design pressure of the system. The allowable for Pm is kSmh where Smh is the allowable stress intensity (See CAESAR II Technical Reference Manual for definition). The value of k can be taken from Table AD-150.1 of the code (which ranges from 1.0 for sustained loads to 1.2 for sustained plus wind loads or sustained plus earthquake loads). Pl is the local membrane stress at the junction due to the sustained piping loads, Pb is the local bending stress (defined as zero at the nozzle to vessel connections per Section VIII, Division 2 of ASME Code), while Q is defined as the secondary stress, due to thermal expansion piping loads, or the bending stress due to internal pressure thrust and sustained piping loads. The allowable stress intensity for the second stress combination is 1.5kSmh, as defined by the Figure 4-130.1 of the Code, while Smh is the hot stress intensity allowable at the given design temperature. Both Pl and Q will be calculated by the WRC 107 program. The third combination actually defines the “ range” of the stress intensity, and its allowable is limited to 1.5(Smc+Smh). See the Technical Reference Manual for detailed discussion. This summation can be done automatically following the WRC 107 analysis through the Analyze-Stress Summation option. This calculation provides a comparison of the stress intensities to the entered allowables, along with a corresponding PASS-FAIL ruling.


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