Hi Hasan,
We have had a Parker MAXIGAS in service at Iowa State Chemical Instrumentation
Facility/Department of Chemistry for 15 years now. It supplies about 115 psi
of 99.5% N2 which we use for MAS, cryoprobes, lift/VT air on the RT probes,
and a few mass spec and spectrophotometry applications. It is rated to 70 cfm,
but that would be 100% duty cycle on the system. It currently has a load of
approximately 30-35 cfm. We have only ever had three MAS-equipped spectrometers
going at the same time. We are just getting to the point of researching
replacements, as this model is no longer supported by the vendor and parts
are becoming scarce. Next door in Ames Lab where they are doing DNP, they use
boil-off for spinning due to the extremely high purity requirements. 99.5% is
fine for most MAS applications.
Things to consider:
- You will need relatively clean and DRY air going into the generator
- Scroll type air compressors are more expensive up front but can provide
oil-free and already pretty dry air going into the dryer (reduce wear and
tear on dryer)
- For a large capacity system like this you will need a pretty large dryer
- Dryer options include desiccant dryer and refrigerated dryer. Opinions will
vary but people I have talked to will say that desiccant dryer will produce
better quality air input to the generator.
- Generator/dryer will need annual-ish service to ensure the desiccant is
performing well, and to replace some valves in the generator.
- Every 5+ years (depending on average load) you will need to replace the
molecular sieves in the generator.
- Air that is not sufficiently dry will result in more rapid degradation of
the molecular sieves, which creates greasy black dust. My system is in a
mechanical room so this is not an issue in terms of cleanliness but just a
heads up if it's near instrumentation.
Hiccups:
- Our main issue has more frequently been the compressed air supply going down.
This is more of a facilities issue because the Chemistry dept maintains the
generator and related equipment but campus facilities maintains the compressors,
and compressor maintenance has fallen through the cracks on occasion.
- We have had some valves go on the nitrogen generator.
- We haven't had any (knock wood) major issues with the generator like Sparky
alluded to.
- We have had a couple of extended outages of nitrogen (a few weeks) which
means you cannot use cryoprobe, low temp VT, etc. Our labs have taps for both
building compressed air and compressed nitrogen. So we are able to switch to
air for the RT probes/spectrometers. MAS at 400 MHz or below does not need
nitrogen (unless you are doing a lot of VT, I suppose).
Price:
I have budgetary quotes from a couple of vendors, one where it is an integrated
compressor/refrigerated dryer/generator, and another that has separate
compressor/desiccant dryer/generator. Both of them came in ballpark $130k,
before installation. Feel free to reach out via email if you would like more
details or documentation.
Cheers,
Sarah
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Received on Wed Apr 15 2026 - 08:26:42 MST