I am currently evaluating several pressure vessel design packages, and while testing PVElite I found some things I would like to ask some questions about...

1) Heat exchangers: We always build them with the tubesheet welded inbetween the shell and the channel (if integral on both sides). This is not possible to do in PVElite: the tubesheet needs to be drawn inside the shell. Can I presume the results are the same? If I try to simulate our configuration, the 3D preview shows a gap in the vessel.

2) Heat exchangers: For cases 4,5,6 and 7, it is allowed to use the operating temperatures in stead of the design temperatures. PVElite will calculate our existing heat exchangers as 'not OK for ASME' (see UHX-13.4(b))

3) Heat exchangers: PVElite uses different thermal expansion values then the ones I can find in ASME IID (customary). This causes different results between PVElite and our calculation sheets. In my test I used following materials (I use SI_ASME units):
A516-70 @231.2°C: alpha = 7.6166*10-6 according to ASME IID (=13.71*10-6 in metric units)
According to PVElite: alpha = 15.6267*10-6 (metric) = 8.68148*10-6 (customary).

4) While using ASME VIII div2, it is not possible to see which materials are selected. (If I switch from DIV1 to DIV2). A516-70 has the same name in both divisions. It would be very interesting to see the difference.
Even better would be that PVElite remembers the materials from different codes. This way we can show our customer the differences in thickness between DIV1 and DIV2, to decide if it is enough to cover the extra costs for DIV2 production).
It is very difficult to switch between codes if there are many parts involved.

5) in the DIV2 calculations for nozzles I came across following strange situation:
- in DIV1, a cilindrical shell needs to be 110mm thick. Therefor, I have a 20" nozzle that I can reinforce without problems.
- I switched to DIV, so the shell needs to be 99mm thick. But it isn't possible anymore to reinforce the 20" nozzle anymore. The nozzle can only be reinforced enough by increasing the shell thickness to 105mm.
After looking into the calculations, I saw that for calculation 4.5.5.1 (k) - step 11, Pmax2 is calculated with MIN(nozzle S-val, shell S-val). This isn't logical in my opinion. In the nomenclature, the S-value to be used is defined as the "allowable stress from Annex 3.A for the vessel at the design temperature".

These are some issues I found while checking PVElite against the ASME code. Could anybody tell me if these are (known) issues or if these are normal cases according to ASME?

I tested with PVElite 2009 build 090101


Jeroen.

We figured something out concerning the thermal expasion values:
PVElite uses the (old) TEMA values in stead of ASME values.

I also write 'old', because the values from TEMA ed.8 are used, not the ones from the latest version, ed.9. In this latest version, the thermal expansion values are the same as in ASME.

This would be an error in our opinion.

Hi McJe,

The default pointer to the Elasticity properties can be changed in the material properties dialog. Use the help (F1) screen to aid you in making a new selection. The next build of PV Elite will have updated pointers that refer to ASME Section II Part D properties by default.

Hi Jeroen,

I will go in detail to your questions,

1) make channel and shell cylinders separate. Then, connect the tubesheet to the end of the channel.

2. We will address the issue of operating pressures in future.

3) This has already been addressed by Scott.

4) Once you switch the material database or the design code, the materials have to be reselected from the database. A trick you can use is to go to the Design Constraints tab, change the Internal pressure Design Temperature to something else and choose to apply that to the whole vessel. This will force the program to get material properties from the new material database. Now, you can change the design temperature back to its original value.

5) For this case, send you job file and the question to the COADE tech support.

I would suggest making 2 copies of the file one with Div. 1 and one with Div. 2. Otherwise, you might get mixed up.