If the vessel has a single nozzle projecting from the main cylinder (or no nozzle), then set the Type of model to generate drop-down box in the General tab to Single nozzle.
To generate a plate or shell element model, select the Plate/shell option in the Type of pipes generated drop-down box on the General tab. To generate a brick element model, select the Solid option. Note that the Preview Area does not show the thicknesses; it continues to show the plate/shell mesh.
The main dimensions of the cylinder will be defined in the Geometry tab. The pressure vessel is always drawn with the axis of the cylinder along the X axis, and any nozzle specified intersects the cylinder at the YZ plane; that is, at X=0. The total length of the cylinder is specified with two values: the length on the positive side of the nozzle intersection, and the length on the negative side of the nozzle intersection; that is, in the positive X and negative X directions.
If the pressure vessel does not consist of an entire cylinder, set the Angular extent of cylinder drop-down box to one of the following. Otherwise, leave the setting at Full 360 degree sweep for a complete vessel.
Specify the corresponding angles in the Angular extent in negative direction and Angular extent in positive direction fields. The angles follow the right-hand rule, so the angle in the negative direction goes about the -X, and the angle in the positive direction goes about the +X axis.
To create a pressure vessel with no nozzles, activate the Create model without nozzle check box on the General tab.
The intersection of the nozzle axis and the cylinder will be located in the YZ plane. The default axis of the nozzle will be collinear with the Z axis and will intersect the cylinder along the cylinder axis. This is controlled by the options in the Pipes Intersect at drop-down box on the General tab.
The Offset of nozzle specified using drop-down box on the Intersection tab is used to specify how to specify the offset out of the XZ plane. If the Distance option is selected, specify the location along the Y axis where the nozzle intersects the cylinder in the Nozzle's offset distance (DY) field. If the Angle option is selected in the Offset of nozzle specified using drop-down box, specify the angle at which the nozzle intersects the cylinder in the Angular offset of nozzle's axis (ADY) field. See Figure 1. Note that the nozzle is still parallel to the XZ plane. Note that this value follows the left-hand rule, so a negative angle rotates the nozzle about the +X axis.
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Offset of nozzle by distance |
Offset of nozzle by angle |
Figure 1: Offset of Nozzle |
For both cases, the nozzle can be rotated about the Y axis so that it is not parallel to the Z axis. Specify the angle in the Angular rotation of nozzle about Y-axis (AR) field. Note that this value follows the left-hand rule, so a negative angle rotates the nozzle about the +Y axis.
Figure 2: Rotation of Nozzle About Y Axis
A positive angle is shown. Note that the angle follows the left-hand rule.
The length of the nozzle, inside and outside of the cylinder, are specified on the Geometry tab using the Length of nozzle (L2) and Nozzle's length inside cylinder fields, respectively.
After a head is added to the main cylinder or to a nozzle on the main cylinder (see below), a nozzle can be added to the head! On the Heads dialog where the head is defined, activate the check box Include nozzles on head, and then click the Nozzles on head button. Refer to the page Nozzles on Heads for details.
Flanges can be added at either end of the cylinder and at the end of the nozzle. Repad can be added at the intersection of the nozzle and cylinder. The widths of these features can be specified in the Flanges/Repad tab. Activate the check boxes for the features that you want to add and specify the desired width in the corresponding field.
A feature region is a layer of elements surrounding the nozzle and cylinder intersection (see Figure 3). It could be used for additional reinforcement, a region of constant width, or as a region to hide/show the elements and stresses near the intersection. The following steps are used to create a feature region:
If the pressure vessel has heads on either end of the cylinder or on the nozzle, specify these with the Model Heads dialog. See the page Heads Dialog for details.
Each piece of the vessel - cylinder, nozzle, repads, and so on - can be created on a different part number. Recall that the part number controls parameters such as the material properties, and for plate/shell models, the thickness of the part and which side is top and bottom for pressure loading.
You can control the part number into which each piece is placed in the Parts dialog by accessing the MODEL pull-down menu and selecting the Parts command. When creating a solid mesh, use the Solid mesh composed of drop-down on the General tab to choose between creating the solid mesh on a single specified part number or on multiple parts.
You can control the mesh spacing used for each part of the pressure vessel in the Mesh Parameters dialog by accessing the MODEL pull-down menu and selecting the Mesh command. When the Meshing method drop-down is set to Only transition parameters NHTX specified or Only transition parameters NHTT specified, you will only be able to control the mesh size in one direction (NHTX or NHTT) of the transition area where the nozzle meets the cylinder. The rest of the mesh is based on the single input for the transition region mesh size.
To control the mesh in all areas of the model, select the All increments specified option in the Meshing method drop-down box. Go to the appropriate tab for the mesh that you want to specify.
Most of the input is a straight forward number of how many elements are desired along a particular dimension. Those numbers then propagate to other areas of the vessel. For example, NHTT and NHTX determine how many elements are around the perimeter of the nozzle and any head placed on the nozzle. (See Figure 3.) Other parameters on the Mesh Parameters dialog are clarified below.
If you are creating a brick model, the thickness of each part can be specified in the Solid Thickness dialog by accessing the MODEL pull-down menu and selecting the Thickness command. (For plate/shell meshes, the thickness of each region is specified in the FEA Editor under the Element Definition.)
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Key: 1 = nozzle mesh 2 = optional feature region on the nozzle 3 = optional feature region on the cylinder 4 = optional repad on the cylinder 5 = transition region on the cylinder NHTX = half the axial length of the transition region NX = distance between nozzle (or repad or feature region if it exists) and end of transition region in the axial direction NHTT = half the sweep length of the transition region NT = distance between nozzle (or repad or feature region if it exists) and end of transition region in the sweep direction |
Figure 3: Transition Mesh Between Nozzle and Cylinder |