Some years ago, I had occasion to do a lot of work with cryogenic piping sstems. Cryogenic properties are available at good university libraries and in other places. Since you re in Houston, I suggest you spend a few hours at the Rice University library.

Without digging through a lot of old files, I cannot give a definitive answer, and I have no intention of doing your research for you. But my recollection strongly suggests that you do NOT take the course of action you appear to be contemplating without the extracurricular work. You could wind up with a whole lot of egg on your face.

The Code does allow the stress engineer to select properties for conditions outside the range of data that it mandates. But it DOES NOT suggest that you may select them out of a hat. It presumes that you will approach the determination of such properties in a professional fashion. In this case, the implicit assumption is that you will do a little research rather than simply guessing.