Hose for low pressure low temperature N2?

[earthwalker84]

I have very little cryogenic experience and I'm trying to find a well insulated hose that will remain very flexible at cryogenic temperatures.
I'm trying to supply roughly 0.5 CFM of nitrogen gas at about 100K and atmospheric pressure to a cryostat device. I was thinking that hose with ~1/2" ID would be an appropriate size.
The device is mounted on a motorized stage and will travel 1" in X,Y and Y axes so the hose needs to be very flexible as to not resist motion.
Does anyone have any ideas??
Thanks

 

[belowzero]

Approach someone like Air Products, BOC or Cryo Services and ask for an N2 hose and technical advise on its use, as this is predominantly made for liquid it may stand up to what you want but these people have a vast wealth of knowledge in these matters as they supply many varied types of customers doing very different things.
Most of my applications have been flexible until fixed onto the test equipment and then remain stationary for the low temp period, however that said the N2 pipes don't last very long.
B

 

[earthwalker84]

Thanks B! I'll give them a shot.

 

[iainuts]

Flow rate is very low, so if the nitrogen has to stay cold, you'll need a vacuum jacketed piece of hose. Even the ends of the hose will pick up significant heat if not insulated in some way, so if you're looking to keep the temperature at roughly 100K, there are two basic ways of getting your hose to do that.
1. Use VJ with bayonets on each end.
2. Use VJ with pipe fittings on each end, then insulate the pipe fittings with closed cell foam insulation.

You can purchase VJ hose from a wide variety of sources including ACME Cryogenics, Technifab, Cryofab or look for any of the suppliers here:

http://www.thomasnet.com/nsearch.ht...m+Jacketed&heading=58632803&navsec=prodsearch

I wouldn't suggest calling one of the industrial gas companies. They don't generally make their own VJ equipment, and for something like this, if they even quoted on it, they'd more than likely be just reselling you something from one of the above manufacturers.

If the gas doesn't have to stay cold, then just use a piece of stainless steel, flexible metal hose that can be obtained just about anywhere. Even McMaster Carr has it. You will need to clarify the requirements for flow rate (SCFM or lbm/sec would be better than CFM), heat leak, temperature and pressure if you need more advice.

 

[belowzero]

For your application with movement, I believe a jacketed hose will not work, it will fail very quickly at the joints as they are not designed for a constant cyclic movement(Which I think is the case here). These pipes are very thin rigid wall and are typically a welded construction, which is designed to be fixed.
You may find talking to AS Scientific a help as they deal with customers for scanners and large electromagnets but have a wealth of experience if you didn't want a gas manufacturer -

http://www.asscientific.co.uk/

The vacuum pipeline systems are a big part of what they manufacture.
B

 

[unclesyd]

I think you can approach your requirements for movement with a properly selected SS steel flexible hose design. If you look at this table on the Tygon site you will see a requirement for a dynamic bend radius which is used to extend the life and in your case remove stiffness. If you increase this radius up to a point to where mass doesn't become a problem up will increase the life of the hose and at the same time lower the resistance to movement. In an application such as yours the hose will still have a finite life.
We used these and similar type hoses in the same manner as your OP with a definite change out schedule.

http://www.tygon.com/Data/Element/N..._line_edit.asp?ele_ch_id=L0000000000000004864

Addenda:

Our loops were all vertical.

 

[earthwalker84]

Wow, this is a fantastic forum! Thanks so much for all of your input!!
I'll let you guys know how things turn out.