Hello,all.

I have a question about using elbows whose material is not the same as piping.

Piping material is A312 TP304
Elbow material is A403 WP304, whose allowable is higher than the piping material.

In CAESAR bend options, there is only input for fitting thickness and K value. How does Caesar include in elbows using a different material?

If you have elbows with properties different from the attached pipe, you have to model them as fittings. So, assuming a 90 deg bend, you would:

• Code the straight incoming pipe up to the starting weld line.
• Then code the 1st element of the bend, using a delta dimension equal to the radius. Change the material and whatever other properties differ from the previous pipe.
• Next code the 2nd element of the bend, again using a delta dimension equal to the radius.
• Finally, code the outgoing pipe, from the ending weld line, changing the properties back.

Please note, for the two materials you referenced, my B31.3 2004 shows the same allowables (see pages 162-163 and 166-167).

babyfatface,

It's interesting that you have different allowables for the two materials that you listed because in my B31.3-2002 they have the same allowables.

Sorry for missing a L in the piping material:

Piping material is A312 TP304L, SC=16.7ksi
Elbow material is A403 WP304., SC=20ksi

BTW, even two material share the same allowables, is there any other parameter be considered? Say, K value.

You said:
1. Code the straight incoming pipe up to the starting weld line.//understand

2. Then code the 1st element of the bend, using a delta dimension equal to the radius. Change the material and whatever other properties differ from the previous pipe.// add bend at the "TO"?
what radius to use?


Next code the 2nd element of the bend, again using a delta dimension equal to the radius.
//so where is bend?

Finally, code the outgoing pipe, from the ending weld line, changing the properties back.

You use the bend radius. For example, if you have 8 inch pipe, the standard long radius value is 12 inches. So your delta dimension would be 12 inches.

On the incoming (12 inch) element (using the example numbers above).

so my understanding is

Code 12in pipe using new material, say node number 100-110, so add bend at 110. I am asking what is the bend radius to be used? 12 in? Any other changes to bend properities?

Then code another 12in pipe ,say 110-120, right to the previous one? Is there duplication?

No there wouldn't be any duplication. Take a look at the bend modeling detail in the Quick Reference Guide, this should all make sense then.

Here is an example, you can code both in and compare them.

Case 1 - same materials

Element 1 10-20, DY=10ft, diam=8, thk=std,
Material = A312 TP304L, BendBox is checked. This means there is a bend at the end of 10-20.

Element 2 20-30, DX=8ft


Case 2 - different materials

Element 1 110-120, DY=9ft, diam=8, thk=std,
Material = A312 TP304L, BendBox is not checked.

Element 2 120-130, DY=1ft, Material = A403 WP304, BendBox is checked. Note, the DY of 1ft happens to be equal to the bend radius (8 * 1.5).

Element 3 130-140, DX=1ft. This is the same delta value as used for Element 2.

Element 4 140-150, DX= 7ft, Material = A312 TP304L

Now, use the [Alt-G] key combination to set the coordinates of nodes 10 and 110, just enough to move the two segments apart. Say for node 10 use (0, 0, 0) and for node 110 use (0, 0, 5). You should see both segments, side by side and they will look identical. The only difference is that from 120-140, the bend fitting is a different material. You can show this graphically by clicking on the material button on the toolbar.

I got it when trying it in caesar. Thanks for your kind help.