Assistance Required: Design guidance on Cryogenic system
To Mark/Jim and others who are interested
At the moment I am working on a design check of a liquid nitrogen cryogenic system.
The exact questions / issues that I am looking into are:
1. Standards / Regulations / design guidance as to the materials to be used for the liquid nitrogen line and the cyrovent line.
2. Standards/Regulations for frequency for Cryovent cut ins on Liquid Nitrogen Line
3. Standards / regulations of venting liquid nitrogen boiloff
I have looked at ASHRAE refrigeration guide Chap 47, but this does not seem to have the answers I need. the others around me aren’t sure where else to go.
THe Sub-contractor who is installing the system seems sure of themselves and is stating the original design was inadequate and it should be installed the way they are doing it (which oddly costs more).
(Definition of Cryovent – a port that allows the boiled off nitrogen to escape.)
Holdfast Training Services Trial Blog 
Ben
I have been out all today, but will drop onto this tomorrow.
Jim
Ben. For piping look up Asme 31.3. Precis it to 304, 316 ss and insulate, insulate, insulate.
For a first pass the vents are to maintain liquid and prevent 2 phase flow, position them at high points, throttles and long runs, its quite likely you need more than first thought to eliminate vapour, a bit like a steam system needs condensate pockets, steam traps etc (obviously in reverse!)
W.r.t regulation they aren’t prvs but they are still connected to a pressure system, check the us equivalent of the pressure system safety regulations for minimum pipe diameters, location of vent outlet and also consider any confined space issues.
Hope this gives you some starters for 10.
Mark
Ben
Chapter 47 of the ASHRAE Refrigeration Handbook (2010), contains a very extensive guide to how these sytems work. At the end of the chapter, there is also an extensive list of references. I reckon that this represents the best starting point for your research. I have also got a call out to a colleague for the current NHS design guides on these systems, if there is such a thing, which may make for an interesting comparison with the US standards (possible TMR subject). You can access the ASHRAE book via IHS (search using cryogenic design). The current password is flairtool and the login is rsme; you need UK Design Solutions in the product list. Cheers.
Jim
Thanks for both of those, i will dig deeper and see what comes up.
Interesting development:
The design contractor doesn’t /didn’t really know anything about cryogenic systems, so brought in a consultant.
The consultant is actually the same company that is now installing the system, and saying the first design was inadequate.
We of course only have a contractual relationship with the Head Contractor and the Design Contractor, so already this could get messy, and it may just be that we stump up the extra money and then take it up with the Design Contractor.
Ben