Applies To Product(s): AutoPIPE, Version(s): 2004, XM, & V8i Environment: N/A Area: Modeling Subarea: Original Author: Bentley Technical Support Group The following section will contain questions and answers pertaining to modeling vessels and/or nozzles in AutoPIPE. ATTENTION: Please see the following AutoPIPE help section: Help Contents Contents Tab Modeling Approaches Modeling Approaches Vessel and Nozzle. It is strongly recommended that user take the time to actually perform this example model to better understand the comand and procedure of this modeling approach. See AutoPIPE's online help for additional information helpful when modeling nozzles on vessels / equipment.: a. Tools Model Options Results "Show rigid tee stress" check-box option b. Insert Extra Data Reference Point command Also, be cautious when applying Rigid properties to pipe (i.e. "Rigid options over Range" command), understand the commands settings; " Include Weight" and "Include Thermal Expansion". As mentioned in the online help: AutoPIPE will assign RIGID properties to this component, taking into account the weight and thermal expansion. The pipe modulus for the RIGID component is assumed 1000 times that of the regular pipe. No allowable stresses are computed for these components. If the total weight of the component RIGID is provided, it will be applied at the end point of the component. No warning will be issued if the weight of the component is zero Item #1: Could you please advise how to properly model a nozzle at the dished end. We have modeled using nozzle flexibility option (using "spherical" in flexibility method) Length = head thickness. Then we tried with the "user" input in the flexibility method using the stiffness values from the "spherical" option but the results are completely different between using "spherical" and "user" selection. Answer: As you already know the nozzle flexibilities calculated for a Spherical head are Radial and Bending stiffness of the nozzle, where User flexibilities fields are Radial, Circumferential, and Longitudinal stiffness of the nozzle. In the background, AutoPIPE use flexible joint elements to model a nozzle. The stiffness calculations for Nozzles connected to cylindrical vessels are more sensitive to diameter of the pipe. The difference with your modeling is to be sure that the Radial direction is the same for both User and Spherical stiffness's, and that Spherical Bending values/directions matches the User's Cir & Long values/directions. Consider the following, if you are using the flexibility method = User, what direction is Rad, Cir, Long given global X, Y, & Z. In AutoPIPE a vessel is modeled as a pipe component. So the program does not know which direction a nozzle element Rad, Cir, Long is until you specify the direction of the vessel. Direction of vessel = Global Y, that means Long. is Global Y and Rad. & Cir are set to Global X or Z. Direction of vessel = Global X or Z, That mean Rad. is set to Global Y, Long. is set to Global X or Z and Cir is set to Global axis left over. Again, by defining the nozzle element vessel direction, you are setting direction for Long and consequently Rad and Cir. Item #2: What is the best method of evaluating a nozzle load to see if they exceed manufacture stress requirement limits? Answer: Insert a Reference Point to Evaluate Equipment Loads Use the Insert Xtra data Reference Node feature to define reference points to evaluate loads at vessels or rotating equipment. Works in either Global or local coordinate systems. So anytime the nozzle is at a skewed angle to the vessel and the allowable loads at the nozzle are given relative to the nozzle axis then use the local coordinate axis system. You can define multiple "Reference Points" at any point. HINT : Useful for evaluating in-line pump nozzles and manufacturer stated limits on vessels or equipment. Item #3: How to model Vacuum Jacket on pipe connected to a Nozzle? Answer: Please see the following AutoPIPE help section: Help Contents Contents Tab Modeling Approaches Modeling Approaches Nozzles, Model 1: Cylindrical Vessel Surface. Using this model as a starting point, follow the instructions to model this example. Note, understand the modeling here, the flexible joint represents the wall thickness of the vessel. Therefore unless the vauccum jacketed pipie continues inside of the vessel, select Node point A03 as the starting point of the vacuum jacket. Select Pipe range from A00 to A03, Select Copy command / icon, Select Base point: A00 Besure the active point is A00 and select Paste command / icon, Select Segment B, all. Modify Pipe Properties Over Range PipeID =14"std, pipe OD = 14", press OK button o accept Note: Pipe segments are restrained by Pipe supports, Soil supports, etc... Pipe segments can be overlapped with out warning. It is the user responsibility to review any interference with-in AutoPIPE or to export a model for clash detection by another program. Example, at this point select segment A, notice how it potruse through the pipe at the elbow locations. Select the large pipe elbows and change from Long radius to short radius. Next, in order to connect the larger jacket pipe to the smaller internal pipe, select node point A00, Insert Beam To Point J = B00, section Id = 0 - ridgid Repeat step to connect Node point A03 to B03. Add as any addtional node points for support spiders for the interanal pipe connected to the Jacketed pipe. Example: Select Node point A01, insert Run Dx = 3 ft, press OK button, creates node point A05 Select Node pont B01, insert Run Dx = 3 ft, press OK button, creates node point B04. To support the internal pipe (seg A) from the jacket pipe (seg B), select node point A05, Insert Support type =Vstop, Connected to point = B04 Vstop A05 is no supported by pipe node point B04. As B04 moves so does the support holding A05. See Jacketing piping WIKI page for more details on this topic. Item #4: Modeling a Nozzle per WRC 297? Answer: The following fields of data are available when WRC 297 is selected as a Flexibility Method on a nozzle dialog screen: Enter in values for L1, L2, and Direction of vessel axis to calculate the nozzle flexibility. Copied from the On-line help: L1 = distance from the center of the nozzle to either vessel end or to the face of the nearest internal stiffening attachment (e.g., ring). L2 = Enter the distance to the other end of the vessel (or nearest internal stiffening attachment in that direction). Meaning, measuring from the center of the nozzle in one direction along the axis of the vessel to a point where the vessel end or vessel internal stiffener ring, enter the value as L1. Repeat the same measurment in the opposite direction along the vessel to a point where the vessel ends or vessel internal stiffener ring, enter the value as L2 (note, L1 and L2 are interchangeable values with regards to the nozzle flexibility calculation, see online help "Nozzle Flexibility Calculations" for complete details). Note: When looking at the Nozzle Stiffness values on the dialog screen be sure to read the dialog text "Nozzle stiffness (E6):". The (E6) means that the value in the fields below are multiplied by E6, with the given units. Example, on the dialog screen Rad = 3.1223 lb /in, but in the output report it is printed as Krad=3122285.75 lb/in. Both values and units are correctly printed. Item #5: Questions: Can you provide more details on the Nozzle dialog fields, Length and Thickness? Answer : The Nozzle element is used to take credit for the flexibility of surrounding wall where the nozzle piping is attached. Therefore the modeling concept is that the expansion joint is used to represent the wall thickness and flexibility of the vessel / container where the nozzle is mounted. The Nozzle element length should not be equal to the distance from the vessel / container wall to the a mating flange face. From AutoPIPE online help: Length: Enter the length of the vessel shell wall. Nozzle length is not used in calculated the nozzle flexibility (which is really the vessel shell flexibility). The length defines a flexible joint to which the nozzle flexibilities (as calculated by AutoPIPE) are assigned. Vessel Radius/ Thickness: Enter the outside radius (or half the actual diameter) of the vessel and the thickness of the vessel wall in these two fields. For new user, there remains a lot of confusion around the Nozzle dialog entries for Thickness and Length. Simply put a nozzle element is modeled as a Flexible joint, as shown in the image below. The Nozzle Length field specifies how long the flexible joint being modeled will be (distance between A03 - A04) in the program. Aka, the physical length of the Flexible joint in the model. Again, the Length is usually equal to the wall thickness of the vessel / container where the nozzle is attached too. The Thickness value is used by the program to calculate the respective nozzle stiffness values that will become input into the flexible joint dialog screen (ex, calculated values for: Axial, Shear, torsional, bending stuffinesses). Again, Length and Thickness are 2 different fields used for 2 different reasons; one modeling and the other calculations. Under most circumstances Length & Thickness will be the same. However, be careful when entering these values, always look to see what units are being used. In English units, Length is entered in FT (mm) , where Thickness is entered in INCH (mm) . See Also Bentley AutoPIPE External Links Bentley Technical Support KnowledgeBase Bentley LEARN Server Comments or Corrections? Bentley's Technical Support Group requests that you please submit any comments you have on this Wiki article to the "Comments" area below. THANK YOU!
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