Section 3 Options Data Form

Weld Size/SCF – The two data cells to the right are used for the weld size and the associated stress concentration factor (SCF). The SCF is only used to calculate peak stresses in 3D shell models. The weld size is only used for nozzle geometries, (not structural attachments).

The Weld Size is also used for the axisymetric 2d and brick nozzle models.

The weld size is the leg length of the fillet weld between the header and nozzle. Click on the button to see a drawing defining the weld dimensions. The SCF (Stress Concentration Factor) indicates the increase in peak stress due to the presence of the weld geometry and the effect of welding. Generally the SCF must come from a

comparison of fatigue test results and the finite element results. For PVP geometries and the element type and intersection model used in NozzlePRO an SCF of 1.35 has been found to envelop the existing fatigue test data without undue conservatism.

Pad Weld/SCF – The two data cells to the right are used for the pad edge weld size and the associated stress concentration factor (SCF). This weld size is only used for nozzle geometries with pads and is also used with axisymetric 2d and brick models.

Base Weld Leg Size – Typically the fillet weld leg length is the same along the nozzle and the header. If this is not the case then enter the length of the fillet along the header in the Base Weld Leg text box, and the length along the branch in the Weld Size text box. This option is also available for axisymetric 2d and brick models.

Free POSITIVE Cylinder End – When the Base Shell Type is Cylinder the “top” of the cylinder may be freed.

Any loads through the branch will be carried by the opposite side cylinder end. This is the typical boundary condition for a vertical vessel with a large nozzle. (The top of the vessel is essentially “free,” and the nozzle loads are carried through only the supported end of the vessel. This tends to produce higher stresses.) The freed end is

“capped.” See the button contents are shown below:

Free NEGATIVE Cylinder End – Mutually exclusive counterpart to POSITIVE end free option.

Calculate Pressure Stress ONLY – Click on this box to have NozzlePRO ignore all other loads except pressure.

Stresses will be calculated at the nozzle/shell penetration line in an attempt to trap the peak pressure stress on the inside longitudinal plane of cylindrical geometries. This option is used typically when pressure is cycling and the user is interested in a pressure only analysis. The user might consider also increasing the SCF at the nozzle welds to 1.6. This value can be adjusted based on brick model analyses of the nozzle intersection.

SIF’s for Cylinder Header – For cylindrical geometries this option produces SIF’s for loads through the header.

(The default is for the SIF’s to be produced for loads through the branch.) When d/D is 0.5 or less the SIF’s for moments through the header can be considerably smaller than the SIF’s for moments through the branch. The Code default is to use the same SIF for each, severely penalizing the user when the branch is not loaded. This option allows the user to enter more realistic values for header/run SIFs.

Do NOT Average Stresses – Check box to turn OFF stress averaging. Stress averaging generally produces more realistic values, especially for structural attachments, but may obscure inaccuracies in the solution. Users looking closely at solutions may want to turn averaging off to get a better view of the numerically unaided stress state.

Show FE/Pipe Screens During Run – Click this checkbox to see the progress of the finite element run using the FE/Pipe status screens. These screens provide more information to the user, but also take up more screen space.

Often this is used to aid in debugging a run that does not run to completion.

Show Intermediate Input Plots – The model plot will be displayed when the run is starting. This is included as a visual check of the job progress.

Show Intermediate Output Plots – The model results plots will be displayed as they are created. This is included as a visual check of the job progress.

Use FE/Pipe Editor During Run – Click on this check box to invoke the FE/Pipe data editor whenever the user

plots or runs a NozzlePRO job. When plot or run is selected, NozzlePRO builds the necessary input for FE/Pipe and then pauses at the FE/Pipe input data screen main menu:

From this menu, the user can modify the input using any of the options available in FE/Pipe that are available to NozzlePRO. This is used generally by the support engineer to tweak a model, or can be used by the FE/Pipe user to make quick changes to the automatically generated NozzlePRO model. AFTER changes have been made at the FE/Pipe level, the user can continue using the FE/Pipe version of the model by checking the box Use Existing FE/Pipe Input File.

Leave FE/Pipe Data Files – This check box is used in conjunction with the FE/Pipe data editor box above. To continue using the same FE/Pipe input in subsequent runs the FE/Pipe input file must not be deleted. This box is also used for debugging jobs that do not complete properly. When a job aborts in error, the last data file used may give an indication of the problem.

Use Existing FE/Pipe Input File – Once the user has edited an FE/Pipe input file he may want to continue to reuse those changes in subsequent runs. Click in this check box to reruse an existing input file. Note however, that NozzlePRO level changes will not be picked up if the user is running the input at the FE/Pipe data file level.

These options should only be used by experts with the program or at the direction of a support engineer.

Crude Mesh – Click this checkbox to use the crudest mesh possible for a given geometry. Enter a number in the box to the right as a multiplier to override the checkbox. The number entered will multiply the standard mesh density. Values can be between 0.01 and 10. The user is suggested to use large mesh multipliers with caution.

Seldom are values greater than 2.0 required, and more often 1.5 –to- 1.8 is recommended.

Use Unstructured Mesh for Heads or Structure – Click on this checkbox to use an unstructured mesh for spherical, elliptical, or dished heads. (Unstructured meshes may also be used for structural attachments on cylinders, but this is only recommended for shorter cylinders, where the L/D ratio does not exceed 2.) The unstructured mesh option can be used for convergence studies and in situations where the structured, parametric cubic mesher is not well suited for the geometry.

Do NOT Use the Unstructured Mesh – There will be occasions where NozzlePRO will elect to use the

unstructured mesher instead of the structured mesher. If the user would prefer to try to use the structured mesher, they can deactivate the unstructured mesher use. This is NOT recommended, and users activating these options should check the resulting element mesh and results carefully.

Deactivate Element Smoothing– In certain instances the movement of nodes to form better elements results in element area overlap. Deactivate element smoothing if it is suspected that smoothing is causing this problem. This most often occurs when crude models are run. The crude model meshes are very bad to begin with, and often don’t smooth particularly well.

Print Stress Outside of Discontinuity Zone – NozzlePRO was designed to find the stress around nozzle or structural discontinuities in cylinders or heads. The general stress state in the cylinder or head removed from the discontinuity is generally not of interest because the Code controls this value. Depending on the model type and d/D ratio stress artifacts may exist at boundary conditions that do not effect the stress at the discontinuity. These values are generally not printed in either the static stress plots that appear in the browser window, or in the dynamic 3D plots. If the user wishes to have the stress calculated in the entire model for the dynamic 3D plots, then the Print Stress Outside of Discontinuity Zone box should be checked. The graphical result is shown below. The tabular results will also be changed. A stress region removed from the discontinuity will be added to the report, and the highest stresses in this area reported. If a stress artifact exists at a boundary, it will be included in the report when the Print Stress Outside of Discontinuity Zone box is checked.

Merge Nodes Tolerance-

The following diagrams illustrate concepts and most common reasons to change the Nozzle/PRO defaults (1.1) Concepts

(1.2) Error “3241” = COLLAPSED ELEMENTS

Solution: input a smaller merge tolerance (see below)

(1.3) Error “2010” = DISCONNECTED PIECE OF MODEL (1.3) Error “2010” = DISCONNECTED PIECE OF MODEL

This error occurs if TOO SMALL a value of MERGE NODES TOLERANCE is input... (don’t over-do it) This error occurs if TOO SMALL a value of MERGE NODES TOLERANCE is input... (don’t over-do it)

(1.4) How to Change Merge Nodes Tolerance in Nozzle/PRO (in Two Steps) Step 1... select “OPTIONS”

Step 2... input a “merge nodes tolerance”

Step 2... input a “merge nodes tolerance”

(for “English” units 0.005 usually works. For “SI” units, 0.1 usually works) (for “English” units 0.005 usually works. For “SI” units, 0.1 usually works)

Insert Length – For nozzles that have inside penetrations enter the insert length. Insert nozzle end sections are perpendicular to the nozzle centerline. (Not all insert nozzles ends are perpendicular to the nozzle centerline. Some are contoured to the head. In this case the user should vary the input length to determine the sensitivity of the solution to this parameter. If a dependable solution relies on an accurate modeling of this contoured end section then a support engineer should be consulted.)

Insert Thickness – The thickness of the inserted nozzle.

Do Not Cut Hole in Header for Branch – Click this checkbox if the pipe does not penetrate the shell. Used when pipe is welded to cylinders or heads for support, and are not pressure carrying members.

Branch Pressure – Enter a value if the branch pressure is different from the header pressure. Used for hot taps and some field welded pressure test connections when the hole is not removed from the header and the branch side may be pressurized.

3D Shell Elements – The usual model of choice. Eight-noded reduced integration doubly curved shell elements will be used to model the requested geometry. These element models are considered a sizeable improvement over an equivalent WRC 107 or 297 type model of the same geometry. Shell elements do not consider through-the-thickness direction stress gradients and tend to become more conservative when D/T ratios get in the range of 10 or smaller.

Axisymetric Heads and Skirts – If this option is selected the user can set the axisymetric head and skirt options and additional loadings required using the Axisymetric Head and Skirt Options button that will become activated. The axisymetric modeler in NozzlePRO allows the user to study various through-thickness phenomena more closely, such as:

1) Contoured weld radii

2) Integral or non-integral repads 3) Skirt-to-head weld stresses

4) Effect of nozzle flanged end connections.

5) Head bed supports.

6) Welded-in Contoured Fittings.

Saddle / Shoe Options – To access these options, the user must select either the saddle or pipe shoe attachment option in the main NozzlePRO screen. These options allow the user to modify the saddle or pipe shoe to account for tapered designs, multiple circumferential web plates, distance from head or front-end, and other many options.

Self-weight, liquid head, and saddle forces may also be modeled for a complete and accurate mode of horizontal vessels.

Chapter 2 – Section 4