Can any kind soul with cryogenic experience provide some guidance with respect to the installation temperature to be used in a system designed for minus 79 deg C. The query i have is whether you should design for the maximum ambient (as this would be most onerous) or if a nominal value is acceptable.

Responses arguing the toss over the definition of cryogenic not required.

Many thanks.

Normally , according ASME31.3, The installation temperature should be average ambient temperature per year.

I don't think there has big trouble since your design temperature is just -79. We always select 21 as our ambient temperature for cryogenic piping.

Let me give you some guidance:

First it's important to stablish the Installation Temperature. This is the ambient tempeture during the installation of the piping at the particular geographic location. In other words, is the temp. at the original (as-installed) condition or zero expansion strain state. It should be indicated in your Stress Specification document. For example, if the construction is taking place in the UAE during winter (last months of the year), what is the average ambient temperature during that time? For now, let's keep it simple (it can be more complicated when the construction could take place during winter and summer). Once you have stablished this temp. you can set your Caesar configuration file. Go to Tools>Configuration setup>Computational Control>(New Job) Ambient Temperature. For an existing job, use the Ambient Temperature field on the Special Execution Options dialog.

Now let's talk about your temp. cases. I'm going to consider that -79 C is a normal operating condition which is T1. From this normal operating condition, the system could experience deviation to a higher temp condition. This could be the maximum amb. tempeture or any other high expected temperature condition which can be T2. In this scenario and assuming that T2 > Installed Temp., you should have the following basic load setting:

1) W + T1 + P
2) W + T2 + P
3) W + P
4) L1 - L3 ===> Expansion stress form Installed Temp. to T1
5) L2 - L3 ===> Expansion stress from Installed Temp. to T2
6) L2 - L1 ===> Total stress range from T1 (cryogenic temperature) to T2 ( T2 > Installed Temp.). This is the load case that consider the greater differential effect for this particular example.

I posted a topic about frequency cutoff, please take a look at it and let me know any advice...

Best regards,