I'm working on a Prototype solid state hydrogen store which was built by some other group last year. My main objective is to analyze its performance. But the problem is this system needs to be leak proof before I can do any performance test. There are couple of issues I would like to discuss in this thread and seek experts advice. Firstly, the main problem is the sealing between cap and the vessel flange. I have used steel gasket but the system fails a pressure test. The gasket seats on a groove. The temp and pressure should be 350C and 15bar respectively inside the vessel. I really need to make it leak proof before doing anything. At this high temp. rubber o ring is unrealistic. Really seeking some expert opinion regarding sealing.

 

Hi, We have experience in a similar field. I'd suggest you take a look at Wills Rings from Trelleborg. They are basically hollow metal O-rings but are available vented to one side - think of an open "C" section with the open part of the "C" facing either the outside or the inside, depending on whether your pressure is external or internal. The idea is that the higher pressure exerts on the inside of the "C" section and results in a better seal. As they are metal they can be used at very high temperatures and pressures. They provide excellent sealing performance / very low hydrogen leak rates, especially when plated with, say, silver (plating helps fill roughness in mating surfaces). The only down-sides are that they require good finishes, can only be used once and are expensive relative to traditional / viton "O"-seals. I hope this helps. John.

 

@John: Thanks for your reply. I'm going through their product brochure now. I have also heard of gas filled o rings. Do you have any experience regarding that? I hope these wills rings are not that expensive.

 

Hi, expensive? Hmmmm .... Yes, but that depends on the value of what you are protecting. I guess these products are mostly bespoke, as there are many, many options for diameter, section geometry, material, finish etc. I know that the products I have specified have been made to order and there is a minimum order charge. You'll probably need to go right through the full selection process before you can get a price.
I have not tried the gas-filled ones - the vented ones attracted me as I could "see" how the pressure difference would work in my favour. Good luck. John.

 

I will try to convince my supervisor about this vented type o rings. But, if this internal pressure type o ring is used I need to change the groove (as it is a closed groove). The groove must be opened from the internal side. Correct me if I'm wrong. Thanks.

 

I'd recomend sending a sketch to one of their application specialists - I have found them to be very knowedgeable. They will ensure that you choose the right product for your application and use it in the most appropriate way. Trelleborg also have some good application examples that at one time were on-line. You'll likely find one similar to your application. John.

 

Did you use the O ring with a small vent in it or the C Ring?