Dear AMMRL Colleagues:
Below is a summary of what I have received in regard to a recent
inquiry, with certain personal details removed. I included the responses
that Greg Wiley posted recently and Dave Rice's workshop on IVAN website
which contains several presentations about this topic.
Weiguo
1. By far CryoMech and Quantum Design are the most popular companies
discussed here on AMMRL and probably have the most units out there. Both
are good companies and there are others. Having a good idea of how much
boiloff you have in a day/week is a big factor and the size of your magnets
will affect how much gas you get during a fill if you are trying to capture
fills as well. Lots of help for on AMMRL if you search.
2. Quantum Technology medium pressure system installed here at *** in
April, 2021. We have a 20L/day liquefier with a 150L production dewar, and
a 200L transport dewar. Purification is by LN2, and there are 7 medium
pressure storage tanks with a total volume equivalent to 60 liquid litres.
The system collects from 6 low field magnets (300-500 MHz) and one pumped
800. Total liquid helium usage per year ~ 2700L.
We used the Veiga ProPress 2" copper pipe, and it seems very good. We have
no problems with purity, and no leaks (other than one fitting that was not
crimped which we found the first time we tested the piping). We aren't
collecting quite as much total boiloff as we expect, but since we don't
lose anything during transfers (ie when pressure in the pipes is higher
than usual) we are sure there is not an issue with the joints. We don't
have any fancy manifolds- 20ft of 2" stainless flex goes from the exhaust
to the copper recovery header, and that is sufficient for warming active
boiloff. The frosting helps with knowing when a fill is over, but the
absolute best way (for magnets without a reliable level meter) we have
found to monitor is to watch the pressure in the recovery header, which
jumps significantly when the magnet is full.
The LN2 purifier seems to work very well, and the inlet purity is always
well above the limit, so we think the piping is very clean. We are still
figuring out the exact regeneration period. The main issue we have had
lately is that since the last regeneration the weather has been very humid,
and the building AC does not take it down to winter levels, so there has
been a lot of ice forming around the neck where there is a small flow of
cold nitrogen gas escaping. Even the exhaust pipe got very covered in ice,
but we have extended it and have a fan blowing gently on it now, which
keeps the ice down.
We purchased a scale to keep our transport dewar on (as it doesn't have a
level meter). That has been a bit tricky to sort out, as it is digital and
doesn't necessarily deal with slow changes in weight. But with some
additional instructions from the manufacturer we seem to have got it able
to measure changes of 1 lb or so after switching it off and on. Between
that, knowing what we have in storage, and the dial on the production dewar
the numbers add up to within 5L, allowing us to know how much helium is in
the system.
We are really happy with the direct to medium pressure storage option. The
liquefier constantly takes in the passive boiloff, producing around
6-8L/day, and during a transfer the medium pressure compressor turns on to
direct the excess into storage. The liquefier then ramps up to 20L+/day
until the storage is emptied.
It has taken quite a lot more of our time to monitor and figure out than we
had anticipated, it is a lot louder than we thought (sound proofing a work
in progress, potentially an expensive work in progress!) and there are a
number of small fixes to the HMI interface (which allows communication with
and monitoring of the liquefier and compressor) on our wishlist (and they
mostly will be incorporated on an update).
And finally, it took us a few unexpected events to appreciate- but if
something goes wrong and the system shuts down ... the worst that happens
is the header pressure goes up to 0.5psi and the mechanical relief valve
opens up and we lose some helium. But not nearly so much as we have already
saved by having the recovery system! This has happened a couple of times,
and the magnets are fine. The liquefier compressor seems a bit sensitive-
but the recovery compressor is not- so although there have been a few times
that the production dewar started to warm up because the compressor turned
off, the boiloff got passed back into storage. We can log in remotely to
check that everything is running (via a laptop we have connected to the
HMI), so when there is an issue we usually find out within 24 hours or so.
3.
https://mcgill.ca/mc2/helium-recovery-system
4. Here at *** we have 2 500 MHz NMRs in a lab with an EPR, which will get
occasional helium cryostat use, and the faculty member who got the
supplemental NIGMS grant for the recovery system does magnetic circular
dichroism (MCD), which has a supercon magnet which gets ramped up to field
when they need to do experiments.
As for the HeR system, it is a medium pressure system, which uses a helium
storage bag, with a LN2 purification system. I think this is called a
'manual' purification system, we couldn't afford the automatic one. We
purchased the system from CryoMech and it has the capacity to produce 15
liters of liquid per day.
The system was installed July 27-29 and I'm still grappling with figuring
out the LN2 fills for the LN2 purifier trap. We haven't had to replace the
trap yet and our numbers for the purity have been good so far (<10 nA, and
lately as low as 2.x nA). At this point we likely don't have enough helium
in the system quite yet, and are planning to add more, but the recovery
lines for MCD and the EPR have not been installed.
After seeing several different designs for manifolds for the NMR magnets,
we used the design and materials that you recommended, although I did have
several other very helpful interactions with other NMR facility managers
who went through the same thing. And received photos of manifolds from
several places, which were very helpful.
5.
https://nmr.chem.tamu.edu/HeliumRecovery.php
6.
https://ivanmr.com/category/ivan-nmr-operations-workshops/
7. I'm in the process of installing a Quantum Technologies system. I think
once you get a system installed and pure helium coming through each system
will be similar. I have 8 floors of plumbing to cover. Next week we will be
leak checking this plumbing with helium. Having a sealed, leak-free system
will be the key.
8. We've used Quantum Design and have been pleased with their direct
recovery system. It's easy to use and the ability to fill directly from
the recovery dewar saves a lot of time and helium. The biggest knock on
them is that you are on your own to set up for magnets and labs to tie into
their system. I believe Quantum Technologies may also do that as part of
the installation. Their system is not as functional once installed.
In all cases, these sales people are selling you a helium recovery system.
So long as it liquifies and recovers helium, they don't really care how it
interacts with your magnets. You've got to be very careful.
9. We've just installed a Cryomech system, and we've had both positive and
negative experiences.
On the positive side, the system seems to work really well. We haven't had
any problems since it started working, but it's only been completely up and
running since Sept. 3 though. We were very concerned about noise because
the system is in a big room that also contains two NMRs. So we built a room
within the room to keep all the Cryomech equipment in. But it turns out
that it's surprisingly quite. I don't think the chirping sound of the pulse
tube cryorefrigerator is even as loud as the chirping sound of my
cryoprobe. And we were really worried about the noise from the recovery
compressor - but you can barely hear it when it's on. The
room-within-a-room was probably not necessary.
On the negative side: it was actually installed in July, but it failed
right away and we couldn't use it for six more weeks. The recovery
compressor had a problem with one of its capsule compressors. It overheated
within just a few minutes of turning on. The installation engineer didn't
notice it when he was installing the system because we didn't have enough
helium gas in the recovery bag for the recovery compressor to be needed. He
only briefly tested the recovery compressor to make sure it would turn on.
We didn't notice the problem until a couple of days after he left. Then we
actually had to send the recovery compressor back to Cryomech and wait for
them to repair it. It took six weeks.
Also, they're not extremely helpful. We've had some computer issues - the
remote monitoring doesn't work, and I haven't been able to get a keyboard
to work with the monitoring computer so I can't back up the log files or do
anything else with the data on the monitoring computer. The engineers often
just ignore my emails if they don't know the answer to my questions.
So overall, the system works really well so far. No complaints there. But
the technical support seems a bit lacking.
10. I just finished installing a CryoMech LHeP22 system in February and
it's been working great. CryoMech was great to work with.
When getting quotes, I also looked at Quantum Design, but I didn't like the
design and price point as much. That being said, one of my colleagues has
a small Quantum Design system that's been running for 10+ years with no
problems (it was supposed to be refurbished after 8 years). So they're
definitely worth looking at.
--
Weiguo Hu
Director of NMR Labs/Chemistry & Materials
Conte Polymer Research Center
120 Governors Dr
University of Massachusetts
Amherst, MA 01003
Received on Mon Oct 18 2021 - 05:03:08 MST