Jamming cryogenic service valves with bellow seal

[DesertEagle01]

Hi,

I am currently facing some problems with below sealed globe valves used in cryogenic service (down to -40°C).

After only two to three actuations, the spindle gets stuck to the plug in the area where the rotational is tranlated to a linear movement. We have around 14bar in the system and the dimension of the valve is DN80.
Is anybody aware of this kind of problem? I think for DN80 usually the connection between stem and plug should be made by hardened balls to prevent the contact surfaces from levigating. This is not the case for the valves in question (contact surfaces are directly touching)

 

[btrueblood]

That seems like a pretty poor construction for a cryo valve, if the two parts are both stainless steel. Either a soft bearing pad (teflon?) or harder material like you say. An alternative would be a gall-resistant alloy pair for the mating parts (e.g. Nitronic 50 or 60).

 

[gerhardl]

Even at fairly 'warm' cryogenic temperature as minus 40 deg C, one should use valves designed for low temp cryogenic purposes. 'Allowed for minus 40 deg C' will not ensure troublefree service. Is this a valve construction where the supplier really can show long-term references for trouble free cryogenic services?

 

[DesertEagle01]

Unfortunately I was not involved when the valve was purchased. The supplier told me they never faced this Problem before (but that's their Standard answer). In fact, every valve of above construction gets stuck within a few actuations when used at -40°C. I wonder whether this valve would Show better perfomance at higher temperatures?

 

[EdStainless]

It could be related to the materials and thermal expansion issues, or it could be the lack of lubricity.
Knowing the alloys for those three parts would be helpful.
My hunch is that the valve is not designed for this service.
It may be an issue of material compatibility when cold, or clearances, or something else.
The translation from rotation to lifting is usually done externally in low temp valves (rising stem).


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P.E. Metallurgy, Plymouth Tube