Thanks for your input, David. I noticed that in your exclusions for that rating, you didn't mention gas density. Are they using a _standard_ gas like nitrogen or air to benchmark this? If so, one would at least know if the required gas would leak more or less than the rating.
I've gotten extensive info on mag drive couplings. At $600+ per coupling, their benefits would have to really outweigh their cost. The two drawbacks were, first power loss due to eddy currents in the can and then with the high pressure, the can would have to be too thick which escalates problem #1. At a couple horsepower, a normal can may have losses of 2% -
10%, however it was quoted that in this scenerio, losses may reach 20%. Those losses are proportional to load seen by the coupling. All that aside, I _may_ be able to get away from transmitting significant power through the shaft and use it more as a timing assembly. That would mean coupling load wouldn't be more than a simple parasitic load.So, I may have to go back and rethink that option.
Another option an NG member brought to my attention was to place the outboard equipment on the shaft in it's own _tank_ and equalize the pressures seen by the seal. I think this is probably the best option for long term down the road cost effectiveness but not practical for the