I am still not sure what kind of hoses I could use for my cascade.
Basically, there are three suitable hose types:

1) Rubber with barrier lining to prevent leakage
2) PTFE with stainless steel braid.
3) Pure stainless steel hoses.

Barrier lined rubber hoses are not very suitable since their useable temperature range does not go lower than -40C / -40F

Stainless steel braided PTFE hoses seem already a better choice, and in fact it is what our phase-change guru Bowman uses. But I have read that PTFE is a permeable material; it leaks small amounts of gas over time.

For example, check page 8 in this document
There they test a meter of hose with 30 bar (~450 psi) helium. To prove their hose superiority, that state that permeability has decreased from 317 milliliters/hour to 138 milliliters/hour. Thus, it would take 27 hours to leak a gallon of gas with Bioflex super-duper-hose. Damn, that's much.
Now, we use lower pressures and larger molecules, but these only move out slower.

It might lead to nice explosion risks when using a closed and airtight mainboard housing like I do, and ethane as the low stage refrigerant.


The last hose type is full stainless steel. Do these hoses have their share of problems also?