Refrigeration 2

Did'nt you know about hermatic compressor?but can be application for Ultra Low Temperature?
for this now we should answer "i don't know".
i have 3 type of compressor common using for Ultra Low Temperature, not just say but i have prove for this case.
list 1. copeland RF41 type
2. danfoss GS type
3. embraco J type

all the compressor at list can be application on Ultra Low Temperature...., operating system is
-40 until -86 C.
just for share if you have any information.
please share with me...............................