Clarification for Warning in PVElite 1

[SmallInfo]

Hi Experts
I am in the process of designing a pressure vessel using PVELITE for LPG. The specified conditions involve an internal pressure of -20°C and an external pressure of 50°C. However, I am encountering a warning stating that the external pressure should always be equal to or greater than the internal pressure. Our design requirement calls for a lower internal pressure, so I'm seeking clarification on this discrepancy.

 

[SnTMan]

SmallInfo, I'm going to ignore the problems with your statement and just address the PVE error message.

I disagree with the last sentence of the message, "The temperature for internal pressure should always be greater than or equal to the design external temperature."

The two are completely separate design cases, at least for common components, shells, formed heads, opening reinforcement, etc.

I suspect either laziness on the part of the programmers or serious problems with your input data. In the case of the former, it seems to me you could:

1) Run each design case on its own and select the more stringent requirements from each.

2) Or possibly run both pressure cases at the higher design temperature and insure the vessel MDMT meets the -20 C design temperature at the design internal pressure.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[dig1]

SmallInfo,

I just ran a very quick model w/ SA240-UNS S32205 (ASME Section VIII, Div. 1, 2021 edition) where the design temperature for internal pressure was -20F and the external design temperature was 500F. The S value for internal pressure was correct and for the external pressure 'B' value from HA-5 appears reasonable at 500F.

What pressure vessel code are you designing to and what edition/service pack of PV Elite are you using?

I would contact support and send your file; they are usually very good at finding an issue.

In the past I've had issues w/ EN 13445 design using PV Elite but haven't done one in a while. When I brought up the issue they did correct it in the next service pack.

BR,

Patrick