When NozzlePRO is properly unlocked it will startup as shown below: (When NOT unlocked the word DEMO will appear across the window handle on the top of the screen and input will be limited.)
If the words DEMO show up across the top of the window handle DO NOT USE the results of the PROGRAM for engineering evalutions!
Begin by selecting the base shell and nozzle or structural attachment types, the units to be used and whether or not the shell material should be the same as the nozzle material. Once these inputs are chosen, for a straight nozzle in a cylindrical shell the main NozzlePRO form will appear as shown below:
Only the text fields described by black labels are required. Blue text labels are optional. Enter a 20 inch outside diameter cylinder with a 1.0 inch wall, and a 10 inch diameter nozzle with a 1.0 inch wall. This input is shown
below:
Click on the Loads button, and then enter a pressure of 100 psi. Leave the rest of the fields blank.
Click OK, then click the Plot Only button on the main form. A separate window with the plotted finite element model should appear on top of the main plot form as shown below.
The model should now be ready to run. Close the plot window by using the in the upper right corner of the plot window, or by using file:close. From the main form click on Run FE. A data check will be performed and the following dialog box should appear:
Click on OK, and depending on the speed of your machine the run will take between 1-to-10 minutes. A status bar will be shown in the middle of the main form, and plotted results will show up intermittently. When the run finishes the two bottom panels on the main form will be replaced by a web browser window with the NozzlePRO output displayed.
The output appears in three separate browser panes. The form may be maximized to get a better view of the output. Additionally the user may select “Graphical Results” from the leftmost pane (on the bottom in the image above), and a separate browser window will be brought up that contains only the graphical results. (The user can then toggle back and forth between the graphical and tabular results windows.) The vertical bar in the middle of the three panes can be moved using the mouse so that the full tabular results screen can be shown. The image below shows a maximized window with the tabular results bar stretched to the right and font size “4” selected. The tabular results have been scrolled down to the ASME Overstressed Areas Report.
Separate buttons appear with each graphical plot that let the user invoke a 3-dimensional view of the stress state displayed. The “3d Deformed” view of the pressure (Pl) stress state is shown below:
The 3d viewer was designed to let the user “hold the dynamically moving model” in his or her hand. The stress state may be rotated, zoomed, clipped, scaled or a thermometer may be used to selectively view the actual value of the stress state. If the load case selected has an associated displacement case, then the model will be shown dynamically displacing. The style of the dynamic displacement can be adjusted using the cockpit controls on the right side of the window. The 3d viewer uses DirectX technology. Version 7.0a or later of DirectX must be loaded on the host machine. (Windows2000 loads version 8.0 as part of the operating system.) Hold the left mouse button down and move the mouse to rotate the geometry. Dragging the right mouse button “pans” the geometry. The 3d Viewer is discussed in more detail below but is designed to be “played-with.” Users are encouraged to test the different features to get a “feel” for what works best for them.
Each output report is discussed in detail in the Output Review section below. Hopefully, a good portion of the NozzlePRO input and output is self-explanatory. Where help is available on an input form a key is shown next to the input text box. An example form with help, and the associated help window is shown below:
Most of the input for the default 3D shell calculation is self-explanatory. Particular items of engineering interest are discussed below. Input for Axisymetric brick and 2d element models are described later.
Load Definitions:
Operating loads should include the weight loads. The operating loads are the total loads that act on the intersection through the branch or attachment in the operating condition – usually the thermal plus pressure plus weight load case.
Loads are applied at the end of the nozzle or attachment and are typically the values that would be read directly from a pipe stress or structural steel program. These loads do not include the P*A axial component due to pressure for pipe. The P*A load is included automatically by NozzlePro in addition to any other loads applied to the pipe nozzle.
Loads are distributed across the structural attachment cross-section end in a manner consistent with the beam analogy. (Users do not have to be concerned with boring degrees of freedom, torsional moments, or shear loads causing excessive bending in the structural shape. Vertical shear loads are distributed over longitudinal plate members, for example. Moments on structural attachments are provided as a force couple where practical or as a linearly varying force over single members.
NozzlePRO calculates the difference between weight and operating loads as the “range” case required as part of the ASME Code secondary stress shakedown evaluation procedure. The difference between the weight and operating loads is also used to find the cyclic stress and is used in the ASME Code fatigue analysis. If there are significant weight and pressure loads but no thermal loads then the operating and weight loads should be the same. In this case the only load quantity causing cyclic stress is pressure – and pressure must cycle at least once.
The ASME Section VIII Division 2 Code directs that occasional loads should be combined with weight, pressure and other mechanical loads, and that the resulting stresses should be compared to 1.5(k)(Sm), where k=1.2, and Sm is the hot allowable for the material. The user should leave the Occasional Cycles data cell blank or zero to effect this evaluation. (The Occasional Cycles data cell is found on the Advanced Options Screen.) When the Occasional Cycles data cell is blank or zero the occasional load entered should be the largest signed component of the occasional load. In general this is the magnitude of the wind or earthquake load. NozzlePRO will treat the occasional load as a fatigue-causing load only if the user enters the number of occasional cycles. In this case the user should enter the number of occasional cycles and the full range of the occasional loading. Whenever NozzlePRO sees a nonzero number of occasional cycles it treats the occasional load as a full range cyclic load component. Earthquake loads, for example, are often evaluated as fatigue causing loads with 100 cycles. To evaluate an earthquake load as cyclic, the user should enter the full range of the load, usually twice the value from a static seismic pipe stress analysis.
Geometry:
The user should always check the mesh produced by NozzlePRO before running a job.
The element grid should be reasonably uniform without holes, doubled over areas, or obvious geometric anomalies.If the output is reasonable, the mesh typically is too.
A wide variety of geometries have been tested with the NozzlePRO mesher, but certain constructions may still cause errant meshes.A large number of mesh control options exist wit7•h version 4.0 of NozzlePro, but users suspecting mesh related problems are encouraged to email the model to [email protected]. (The model file is stored as
<jobname>.nozzlepro.) After only a little experience reviewing finite element results users will have sufficient experience to know when results are errant and due to mesh-related problems.
For spherical, elliptical, dished and conic heads, and for cylindrical geometries with structural attachments, the user can optionally use the unstructured mesher. Structured meshes are preferable, but in certain cases unstructured meshes produce better results. A comparison between structured and unstructured meshes is shown below:
The unstructured mesh option and several other mesh controls are available on the Options form:
The Crude Mesh check box will cause the program to use the coarsest mesh possible. The Opt. Mult box lets the user enter a value that will multiply the default mesh. Any value greater than 0.01 may be entered but users are cautioned against inputing values much greater than 2. (Usually values of 1.5 to 1.8 work best.) As a rule of thumb, the element side length immediately adjacent to a discontinuity should be smaller than (RT)1/2, where R is the mean radius and T is the thickness. (This is the side of the element that is pointing away from the
discontinuity. Element sides parallel to the discontinuity can generally be larger. The required size of the element is a function of the variation in the stress/deflection state.)
For head geometries the straight flange, transition and shell lengths can be omitted if desired, but it is
recommended that at least (3)(RT)1/2 of shell length be added to any head boundary. Conversely – just because there is 20ft. of 48” diameter shell attached to a 48” diameter head – there is no reason to enter 20 ft. of shell.
Usually only 3- to 4- times (RT)1/2 needs to be entered down the shell length to accurately trap discontinuity stresses in the vicinity of a nozzle or attachment on the head. When the d/D ratio is large, the nozzle may distort the cross section of the head and this distortion will extend down the shell. An accurate attached shell length must be entered to properly observe this effect.
Nozzle tilt angles can only be entered for cylinder or cone geometries, or for head geometries where the nozzle is off the centerline of the vessel by more than the diameter of the nozzle.
The NozzlePRO and underlying geometry evaluation software make every attempt to create a viable geometry for analysis. Where assumptions or adjustments to the user’s input are made notes are printed in the Model Data report. This report should be reviewed closely for proper interpretation of the user’s data.