Rjack has the ticket. I wanted to pump raw helium 1st because it simplifies mixing a lot. With the extreme cost and availability issues with He doing it this way you can easily identify exactly where the gas is being used or wasted.
while I haven’t tried CB’ing tri-mix with all the gases flowing through the stick at the same time, I highly suspect that it can’t possibly be as accurate as isolating one of the gasses individually first.
Additionally since I’m only dealing with pure He on the first phase of fill my need for a He analyzer is debatably minimal. If I nail my target temps and pressure on the He fill it’s just basic math and an O2 analyzer for the last phase of fill. For the time being I’m using an He analyzer in addition to an O2 sniffer to ensure my process is viable.
I’ll post up compressor specs later but the monitoring was exactly what you’d expect. Laser thermometer on the key component surfaces and visually examining the oil sight gauge “bulls eye.”
I’ve got several samples drawn however I’ll have to wait until Tuesday to send them out. I’m sending out a samp of: raw unpumped fresh out of the K He, raw He pumped out of the compressor, a final sample of the finished 21/35, and an air samp off the compressor.
I’m tempted to send off a lean nitrox sample too but that’s probably overkill. I might do that if this report indicates my O2 CB’ing muttled my 21/35’s numbers.
I was tempted to “stir” the tanks but they were all doubles and my back can only handle so much fun. It was easier to just park em over night.
I only started this experiment because the timing was right. I got the He on trade, I was planning on overhauling the compressors top end this winter anyways, and I got a few deeper dives I’ve been wanting to do but didn’t want to foot the gas bill.