I’m sure everyone remembers learning these simple facts from science lessons at school. Namely that air contains approximately 78% nitrogen, 21% oxygen, plus trace levels of water vapour, carbon dioxide, argon, helium, etc .
Other snippets which I squirrelled away about oxygen whilst in the classroom include the point that it sustains human life on earth, it causes iron to rust and it allows substances such as wood and coal to burn.
In short, when mixed naturally with nitrogen it’s an extremely useful element. However, if your business involves preparing or working with oxygen at higher concentrations, then it becomes a different matter entirely.
For example, as an Emerson Process Management Bulletin states, all organic and inorganic materials will react with gaseous or liquid oxygen at certain pressures or temperatures. That can result in a fire or even an explosion. This means process systems that need to contain oxygen have to be completely and totally free of grease – including the valves!
Later I found another document, this time from Flowserve, which mentions that the inspection level for valves for oxygen service depends on the intended application, be it for commercial oxygen or critical oxygen.
And before I knew it I found myself ploughing reading though a 100-plus page document issued by the NASA, termed “Safety Standards for Oxygen and Oxygen Service”, which contains a mine of information about valves and valve design considerations.
Now the more I delved into this topic, the more I understand just why valves destined for use with oxygen carry such a high premium. Which got me wondering – how on earth does a manufacturer set about making a grease-free valve?
And here’s where that wonderful thing called chance comes into play. Whilst on a recent visit to Metso in Helsinki to discuss control valves I happened to mention this query of mine to Mrs Taija Hämäläinen, who is Director, Neles and Mapag butterfly valves product center. It turns out that Metso has recently commissioned a brand new clean room facility where valves for oxygen service, amongst others, will be made.
Whilst this area is off-limits even to Valve World editors, Mrs Hämäläinen was kind enough to discuss how Metso approaches the design and fabrication of such valves. For example, she revealed the fact that Metso has managed to avoid using screws or bolts in the flow area. And Mrs Hämäläinen was kind enough to allow me to write up her thoughts for the March issue of Valve World magazine.
However, I still feel I’ve only understood half the story, namely from the manufacturer’s perspective. So I would be interested to hear of any user experiences. What do you look for in an oxygen valve? Do you consider any of the recommendations and standards excessive? Or perhaps you feel that the manufacturers are missing important issues? One way or the bother, I’d be delighted to hear from you – after all, listening to experts is the best way to learn!
Photo copyright: Metso and Wikipedia