We have E-ONEs dual hydrogen analyzers and the purity decays from 99% to 97% within a matter of 3-4 days on normal scavenge.
We have to constantly flow new H2 gas to the unit to maintain good purity levels. What could be causing this issue?
thanks

Pressure too high? Im guessing with experience I have on a different hydrogen analyzer...

I would start by checking your scavenge... try to increase it to see if it improves but monitor your bulk hydrogen usage. Then ensure your panel is oil and moisture free. sometimes there is the chance of seal oil entering into the analyzers. How is your dew points?

thanks for the input.. turns out we had oil contamination in the DHCP tubing. We cleaned the piping and flow meters with nitrogen and verified our sealing system. Purity decay is no longer an issue. thanks

oil in the sensing lines is always an issue. question is where is it coming from? it is very costly to clean the tubes and even more so if the contamination has reached the cells. Oil in the hydrogen within the generator is typical but a substantial amount can lead to purity decay. True, a high flow scavange can band-aid the issue but you need to look into the oil/hydrogen seal system. do you have proper differential pressure, are the clearances acceptable on the shaft to seals diaphragms? What is the vacuum and are your drain enlargements doing their thing?
I have head of users placing a filtration system upstream of the inlet sensing line but this is only masking a true problem.