Cryogenic service surprises people because the cold itself is rarely the problem. Austenitic stainless has no ductile-to-brittle transition — it stays tough all the way down to liquid nitrogen, which is exactly why it is used. What catches lines out is that everything gets shorter.
What this service does to a hose
Cooling a ten-metre stainless run from ambient to −196 °C pulls roughly thirty millimetres out of it. That movement has to go somewhere, and if the hose was sized for the process movement alone it will be asked to absorb the contraction as well. The result is a hose working outside its live length, usually in tension, which is the one thing a braided assembly must never be asked to do.
The second issue is ice. A cold braid in humid air grows a jacket of frost that stiffens the assembly and, on a flexing line, can lock it solid. The hose then bends somewhere other than where it was designed to.
The third is thermal shock. Filling a warm line with liquid is a violent event, and a line that cycles warm-to-cold daily accumulates fatigue in the same way a vibrating line does — just at a few cycles a day instead of two million.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | 304L or 316L annular corrugated, DN6–DN350 | Tough to −196 °C, and pressure-tight, which interlock is not |
| Braid | Matching grade, single or double | Carries the thrust; sized on the cold pressure |
| Liner | None | A liner traps liquid and gives it nowhere to boil off from |
| Length | Sized for process movement plus contraction | The contraction is the part people leave out |
| Ends | Vacuum-rated where the line sees vacuum | Full vacuum is a different sealing problem from pressure |
For large bore, this becomes an expansion joint rather than a hose — see bellows and expansion joints, which we build DN50 to DN3000 and rate from full vacuum to 50 barg.
What we would not fit, and what happens
Interlock hose. It is not pressure-tight, and on a liquefied gas that means the product leaves through the seam. Interlock has a place on cryogenic sites — as mechanical protection over something else — but never as the pressure boundary.
Anything with a packed seam. Packings that are fine at 400 °C behave quite differently at −196 °C.
A hose installed straight and taut. It has nowhere to go when the line shrinks. The movement types page shows the geometries that survive.
What we need to size it
| We need | Because |
|---|---|
| Medium — LNG, LIN, LOX, argon, helium | Oxygen in particular carries its own cleaning requirement |
| Operating temperature and fill temperature | The difference between them is the movement |
| Pressure, and whether the line sees vacuum | Vacuum and pressure are separate cases, not one range |
| Length of the run either side of the hose | That is where the contraction comes from |
| How often it cools down and warms up | Daily cycling is a fatigue duty, not a static one |