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11 most important questions & answers from ASME B 31.3 which ANALYSIS) › U/G PIPING a Piping stress engineer must know (http://www.whatispiping.com (HTTP://WWW.WHATISPIPING.COM/CATEGORY/UGb-31-3) Pressure Tests of Piping systems-Hydrotest Vs PIPING) › UNCATEGORIZED Pneumatic Test (http://www.whatispiping.com (HTTP://WWW.WHATISPIPING.COM/CATEGORY/UNCATEGORIZED) › UNDERGROUND tests-of-piping-systemshydrotest-vspneumatic-test) PIPING BASICS OF PIPE STRESS ANALYSIS: A PRESENTATION-Part 1 (HTTP://WWW.WHATISPIPING.COM/CATEGORY/UNDERGROUNDof 2 (http://www.whatispiping.com PIPING) › UNDERGROUND PIPING STRESS ANALYSIS PROCEDURE of-pipe-stress-analysis) Piping Elbows and Bends: A useful detailed USING CAESAR II literature for piping engineers (http://www.whatispiping.com (HTTP://WWW.WHATISPIPING.COM/UNDERGROUND-PIPING-STRESSelbows-and-bends) Step by Step Methods for WRC 107 and WRC ANALYSIS) 297 Checking in Caesar II (http://www.whatispiping.com 107-and-wrc-297) Flange Leakage checking in Caesar II using ASME Section VIII June 9, 2015 2 Comments (http://www.whatispiping.com/undergroundmethod piping-stress-analysis#comments) (http://www.whatispiping.com leakage-checking-in76 10 2 caesar-ii-using-asmesection-viii-method) (https://www.linkedin.com/cws/share? (http://www.facebook.com/sharer.php? (https://plus.google.com/share? Top 12 must have url=http://www.whatispiping.com/underground u=http://www.whatispiping.com/underground url=http://www.whatispiping.com/underground Refer my earlier article on buried piping to get preliminary theoretical Piping books for a knowledge on stress analysis of underground piping. Click here to visit pipingstress pipingstress pipingstress begineer into Piping that article. (http://www.whatispiping.com/underground-piping) In this industry analysis) analysis) analysis) article I will explain the steps followed for modelling and analysis the pipes (http://www.whatispiping.com in Caesar II. Inputs Required: Like all other systems you need to model the books) piping system in Caesar II initially following the same conventional method. Must have Load cases So you need the following inputs: for stress analysis of a
Underground Piping Stress Analysis Procedure using Caesar II
So you need the following inputs: Piping isometrics or GA drawings with dimensions. Pipe parameters like temperature, pressure, material, diameter, thickness, corrosion allowance, fluid density etc. Additionally you need the following soil parameters from civil department (geo-technology department) for creation of soil model. o Friction Co-efficient o Soil Density o Buried depth to Top of Pipe and o Friction Angle Equipment/Valve GA drawings as per application. Modelling of the system: Model the piping system from isometrics/GA drawings using the pipe parameters. Normally some part of the system will be above ground and some part will be buried. Let’s take an example of a typical system for easy understanding. Refer Fig 1. The stress system consists of 24 inch CS pipe connected to tank. The parts inside the rectangle are above ground and remaining parts are underground. Create a distinct node at all the junction points of underground and above ground piping. After you complete your model, save it, close and then enter the buried model by clicking the Underground Pipe modeler button as shown in Fig.2.
for stress analysis of a typical piping system using Caesar II (http://www.whatispiping.com cases) Stress Analysis of PSV connected Piping systems using Caesar II (http://www.whatispiping.com analysis-of-psvconnected-pipingsystems) Static Analysis of Slug flow: A Presentation for Beginners (http://www.whatispiping.com analysis-of-slug-flow)
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(http://www.whatispiping.com/wp-content/uploads/2014/09/TypicalCaesar-II-system-for-underground-piping-analysis.jpg) Fig.1: Typical Caesar II system for underground piping analysis
Fig.1: Typical Caesar II system for underground piping analysis
(http://www.whatispiping.com/wp-content/uploads/2014/09/Opening-theunderground-pipe-modeller..jpg) Fig.2: Opening the underground pipe modeler. Once you click on the underground pipe modeler the following screen (Fig. 3) will open. You will find all your input node numbers listed there.
(http://www.whatispiping.com/wpcontent/uploads/2014/09/Underground-Soil-modeller-input-screen.jpg) Fig.3: Underground Soil modeler input screen Now your task is to create the soil model and input data received from civil. On clicking Soil Models button (Highlighted in Fig.3) you will get the window where you have to enter the data. You have two options to select as soil model type, Americal Lifelines alliance and caesar II Basic Model. We will use Caesar II basic model for this article. So select Caesar II Basic model. The modeler uses the values that you define to compute axial, lateral, upward, and downward stiffnesses, along with ultimate loads. Each set of soil properties is identified by a unique soil model number, starting with the number 2. The soil model number is used in the buried element descriptions to tell CAESAR II in what type of soil the pipe is buried. You can enter up to 15 different soil model numbers in any one buried pipe job. Input the parameters as shown in Fig. 4. If you require to add more
soil models simply click on add new soil model. Overburden compaction factor, Yield displacement factor and thermal expansion co-efficient will automatically be filled by default. You need to input all other fields. However, defining a value for TEMPERATURE CHANGE is optional. If entered the thermal strain is used to compute the theoretical “virtual anchor length”. Leave undrained sheer strength field blank. After all data has been entered click on ok button.
(http://www.whatispiping.com/wpcontent/uploads/2014/09/Caesar-II-Basic-Soil-Model.jpg) Fig.4: Caesar II Basic Soil Model Now inform Caesar II about the underground and above ground parts by selecting the nodes and defining proper soil model number. If you enter 0 as soil model number, the element is not buried. If you enter 1, then specify the buried soil stiffness’s per length basis in column 6 through 13. (preferable do not use 1). If you enter a number greater than 1, the software points to a CAESAR II soil restraint model generated using the equations outlined in Soil Models of Caesar II. Refer Fig. 5 for example. After all aboveground and underground parts along with proper soil model number are defined click on convert button and Caesar II will create the underground model.
(http://www.whatispiping.com/wp-content/uploads/2014/09/BuriedModel-Input-Spreadsheet-in-Caesar-II.jpg) Fig.5: Buried Model Input Spreadsheet in Caesar II When underground model conversion is over you will get the buried model. By default, Caesar II appends the name of the job with the letter B. For example, if the original job is named System1, the software saves the second input file with the name System1B. If the default name is not appropriate, you can rename the buried job. In the buried part Caesar II models bi-linear restraints with stiffness values which the software calculates while conversion into buried model. Refer Fig.6 to check the buried model of the system shown in Fig.1. These stiffness values depend on the distance between the nodes. Now open the file (original file appended by B) and perform static analysis in the same conventional way and qualify the system from code requirements.
(http://www.whatispiping.com/wp-content/uploads/2014/09/Buriedmodel-of-the-system-shown-in-Fig.1.jpg) Fig.6: Buried model of the system shown in Fig.1 Few Important points to keep in mind: Typical values of friction angle are as follows: o Clay – 0 o Silt – 26-25 o Sand – 27-45 Typical friction coefficient values are: o Silt – 0.4 o Sand – 0.5 o Gravel – 0.6 o Clay – 0.6 The default value of overburden compaction multiplier is 8. However this number can be reduced depending on the degree of compaction of the backfill. Backfill efficiency can be approximated using the proctor number, defined in most soils text books. Standard practice is to multiple the proctor number by 8 and use the result as the compaction multiplier. After entering data in soil model when you click ok, the Caesar II software saves the soil data in a file with the extension SOI. During the process of creating the buried model, the modeler removes any restraints in the buried section. Any additional restraints in the buried section can be entered in the resulting buried model. The buried job, if it exists, is overwritten by the successful generation of a buried pipe model. It is the buried job that is eventually run to compute displacements and stresses. Caesar II removes the density from the buried part model while converting into buried model.
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