crigenic valves 1

[Estibaliz]

We are manufacturing an special valve or alloy still for an homologation We must down the temperature of the valve to -196ºC, make 500 cilcles of open- close, and ut the valve to 400ºC.before those temperatures changens and those cicles intenal part of the valves suffer a high damages.

on The stellite of the disc and the guides appears small crack that make impossible close the valve before this tests. can some one help me with this?

Must i try with stellite 12, or other material, it is necessary give to all parts of the valve a criogenic treatment?

 

[gerhardl]

With your information it is fairly impossible to answer your question.

There exists a number of companies already manufacturing and supplying all sorts of cryogenic valves. It seems unlikely that you are trying to solve a problem not already solved other ways by other manufacturors.

Look at what you cand find on similar valves on the net.

From your question I am anyway guessing at perhaps the two most important points, others may have other opinions, and I might be wrong, but:

a) it seems unlikely that a cryogenic valve should not have the demand that the completed valve (all parts) should be able to andure the full temperature range.

If 400 deg C plus is the top temperature required, this seems high to me. Is this part of a firetest or something, not requiring full operating ability afterwards?

(Check and explain test details and requirements!)

b) cracking of material composites undergoing a temperature change indicates obviously that the material combination (put together) are not strong enough to undergo the temperature changes required, or at least not the change in temperature per total time. (Temperature/time cycle)

Advice on material selection need more details.

 

[Estibaliz]

we already manufacture cryogenic valves but we can not achive the requisitions of this test for an homologation of a client.
The valve is manufacture of alloy steel and the closures and guides are averllaied with stellite. We think that the problem is the hardness of the stellite but we are not sure. I am thinking in make a cryigenic treatment to wedge(with stellite overllay) rings (with stellite overllay) and to the guide (with stellite overllay) but i am not sure it this was the solution. I am looking for some information in the net but i can not find anything. It is not impossible but really complicate. All us know that the cryogenic valves are not going to support 400ºC but it is the requisition.The valve shall be abailable to support this temperatures changes.

 

[gerhardl]

I suggest that you try a renewed posting of the question in this sites forums for cryogenic engineering and metal and metallurgical engineering for a possibel better answer on the interacting caracteristics by very low and high temperatures.

Another thing: the demand is either stated because 'someone in some way' already have solved the problem, or it is perhaps 'untried for valves but realistic for piping' and possibly very difficult or impossible to obtain with operational valves.

Suggest also that you before further postings ask for all details around the requirements origin.

 

[abscott]

I agree the required temperature range is extreme. While Stellite 6 (welded overlay) is common practice for seating surfaces it is hard and somewhat brittle and will crack when exposure to rapid temperature changes. I would expect Stellite 12 (solid form) would also crack while underging a rapid temperature change.

I do not know what base materials you are using for trim parts, but I would recommend a surface treatment like "nitriding" or similar. The nitrogen is incorporated into the material matrix and makes the material harder but I don't think you would experience cracking. Check with material science engineers.
Hope this helps.
ABScott

 

[Estibaliz]

thanks for your answer the malril base is WC9. we are going to try it with ST12. About to treat the peace we are thinking in cryogenic treatment. I dont know if with this option we solve our problem, but thanks all.