Resultados de la simulación

To skew a structural support, start with a regular support. A typical “T” type structural attachment is shown below:

When the graphic window is displayed the user can select Settings:Stamps to get the following dialog box:

When “Plate Points” is checked the points used by NozzlePRO and FE/Pipe are shown on the plot:

The first step will be to shift the points on the end of the T section in the “t” direction 7 inches. This will be the points 7, 8, 9 and 11. There is no facility in NozzlePRO to do this so the FE/Pipe editor will need to be used. In the optional form the user would set the “Use FE/Pipe Editor During Run” checkbox as shown below. Note that the “Leave Data Files” box is checked automatically. This is so that files edited by the user can be reused. (Once we’re happy with our changes we don’t want to have to continue remaking them.)

When the FE Run is started the following FE/Pipe screen is displayed:

The 7-Plate Geometry option should be selected:

“Plate Points” should be selected from this screen.

As can be seen in the bottom right-hand corner there are 15 plate point screens. (There are 15 points possible for the variety of structural cross sections available in NozzlePRO.) The PageUp and PageDn key moves between the different screens. Page down until the first point that should be moved is shown. This is point 7:

Note that point 7 has a “status” of 3 – it is removed from the surface as might be expected. The “?” key can be used when the cursor is in any of the data cells to get help for the particular cell. Since the end points should be shifted from their current positions by 7 inches in the “t” local direction the input for points, 7,8,9 and 11 will be changed as shown below:

These changes produce the skewed structural support shown below:

Using the changes in the r, s and t directions user’s can typically skew any NozzlePRO support in any manner needed. Since the movement of points is usually a trial and error procedure, we want to be able to do two things:

1) Go thru the change-plate point-plot procedure iteratively until the desired model is obtained.

2) Reuse the existing geometry once it is available.

At some point using the NOZZLE.IFU file produced by NozzlePRO will be easier than going through the NozzlePRO backdoor to make changes to the FE/Pipe model. The user will have to decide how to best proceed on a problem-by-problem basis. Using NozzlePRO for structural supports is convenient because NozzlePRO distributes moments and shears over the structural attachment in a manner consistent with load distribution through structural section shapes. Without this load distribution procedure flanges might end up carrying vertical shear loads that they will not typically support and high, unreasonable stresses will result. Anyway, it is for the user to decide which is the best way to proceed once he is aware of the available options.

The control of the input files occurs through the optional screen:

The last checkbox is the critical one. If left unchecked, whenever the NozzlePRO user requests a “plot” or an “FE-Run” NozzlePRO will overwrite any existing input file with the current data. If checked, then whenever the NozzlePRO user requests a “plot” or an “FE-Run” the existing FE/Pipe input file is used and the current NozzlePRO input is ignored. Using these options the user can make changes to thicknesses for example, and rerun the model without having to go through the model alteration process. If the user wants to change the loads on a structural attachment however, he can either change them in the FE/Pipe input if comfortable with this, or must go back to NozzlePRO to make the changes. In this case the FE/Pipe file must be overwritten with the new loads – and any geometry changes will have to be reentered. We generally go to this much trouble for two reasons:

1) We want to use the NozzlePRO load distribution algorithms.

2) We want the output in a NozzlePRO format.

At any point FE/Pipe can be used with the NOZZLE.IFU input file produced, but the user must be somewhat familiar with FE/Pipe to get the reports and graphics that come automatically from NozzlePRO.

User’s should find however, that once the changes that have to be made to a geometry are known, that remaking them after a load change is not such a big problem. This approach can also be used to add multiple nozzles or supports to a NozzlePRO geometry but support for this is not considered part of the standard NozzlePRO capability, and only FE/Pipe users should attempt these more significant modifications.

A more meaningful example will be shown below:

The model will be similar to the one shown above. The load will be carried through the bolt section. Since flanges don’t transmit vertical load in the persence of webs, the load will be carried through the web section at the bolt-hole section. This is demonstrated below:

The 14” length of the starting orientation was chosen arbitrarily. Once chosen however it is a significant number since the points 7,8,9 and 11 will have to be moved from the end of the 14” section to the location where we want them.

The point 9 will move from the (r,s,t) coordinate: (5,14,5.66) to the (r,s,t) coordinate:

(5,4sin(45),4sin(45)+11.313/2) = (5,2.828, 8.485), the point 8 will move from the (r,s,t) coordinate (5, 14, 0) to the (r,s,t) coordinate (5,8sin(45),8sin(45)) = (5,5.657, 5.657). The point 7 will move from the (r,s,t) coordinate (5,14,-11.313/2) to the (r,s,t) coordinate (5, 12sin(45),12(sin45)-11.313/2) = (5,8.485, 2.83). The point 11 is below

point 8 will be moved from an (r,s,t) coordinate of (-5, 14,0) to (0,8sin(45),8sin(45)) This will put node 11 on the centerline in the vertical direction and will create the proper shear area at the bolt centerline section.

The original input for this model in NozzlePRO is shown below:

The plot with Settings:Stamps:Plate Pts is given below: (Remember to check the box to use the FE/Pipe data editor so that plots can be generated from the changed geometry.)

The original plate point 9 is shown below:

The new point 9 location will just be typed over the original location. (The change from one to the other could be entered. The user should input whatever seems easiest for him.)

The support is shown below:

Chapter 6 – Section 1 WRC Comparisons

In general WRC 107 comparisons to FE/Pipe results are excellent when thin shells are analyzed and when the model is within the accepted parameters of WRC 107. Nozzles in the centers of heads are evaluated most accurately. Most WRC107 programs give the stress intensity at four points around the nozzle on both the inside and outside of the geometry. This stress is usually compared to 3Sm and is caused by all operating loads on the nozzle. The resulting stresses from a WRC 107 run of this type should be compared to the Pl+Pb+Q stresses from the finite element calculation. Note that Pl stresses evaluated in accordance with ASME Section VIII Division 2 are membrane stresses. These are the average stresses through the thickness and do not include the bending stress component at the junction. (See ASME Section VIII Division 2 Appendix 4 Table 4-120.1.)

WRC 297 comparisons in the vessel or header tend to be good but become overly conservative when the high stress moves into the branch when the t/T ratio becomes less than 1.0. This result is certainly demonstrated in the finite element calculation.

WRC 107 tends to be somewhat less conservative than finite element results, but that WRC 107 results parallel FE calculations through d/D ranges of 0.1 to 0.8, where the WRC and Finite element curves cross, the WRC 107 results becoming much more conservative beyond this range. (When the approach used outside of WRC curve parameters is “last curve value.”)

The following list summarizes areas where WRC 107 ad WRC 297 are considered weak, or where further concern should be displayed:

a) d/D > 0.5 b) t/T < 1.0

c) Pad reinforced nozzles d) Hillsides or laterals

e) Area replacement rules for pressure are barely satisfied and large D/T.

f) Temperatures are approaching the creep regime.

g) Cycles are greater than 5000.

h) Design and operating conditions are approximately the same.

i) The load consists of high-pressure stresses and high loads.

j) The Piping attached to the nozzle is long, flexible, and somewhat unrestrained.

Chapter 6 – Section 2