Dear AMMRL,
Thanks to the many who replied - we just ordered one (the Restek model, due
to local availability). Here are the anonymized responses for posterity.
Best,
Sameer
I have the GL Sciences LD239 and I'm pretty pleased with it. I'm not
sure how accurate it is, but it has helped me identify small leaks in my
helium recovery system.
We got one of these, which are tiny, and not appreciably magnetic:
https://www.glsciencesinc.com/ld239-helium-leak-detector
We have the Restek detector.
Since it is based on thermal conductivity it is not really a reliable tool.
It cannot distinguish between different gases and you should also keep in
mind that you might also have leaks where cold He gas is escaping. But
in overall it does a good job if you want to check an area where you suspect
a helium leak. Much better than spaying soap on the area and watch for
bubbles. We have been using it frequently and it is worth the investment.
I bought and use a second hand Agilent PHD-4. It's portable and has good
resolution. 10 -4 cm/min. It cost about $9K second hand. It has replaceable
filters and lithium ion batteries.
We have a good history with our Gow-Mac leak detector. You can test its
sensitivity with a small, deliberate helium leak in a hose or fitting. Or,
you can use a helium cylinder at a very small flow rate. The device does
quite well at simply detecting a gas that is of different composition than
the gas it was zeroed on.
You do not really need such a device to actually detect helium. The device
can also be used for other gases.
We purchased the Restek leak detector and have found it to be very useful in
finding leaks in our Helium recovery system. The line is long enough so I can
keep the body far enough away from our unshielded 500 without any interference
or draw hazard. It definitely works with in the 5 gauss radius of this magnet.
Not sure if stronger magnets would be an issue, but I think every lab with a
recovery system should have one these to periodically check for leaks.
I purchased a Restek (model 28500) He leak detector to test the connections
in my He recovery system. I've been using it for 2 years and it works great.
I did some calibrations with a fancier in-line flow meter I have (Omega FMA-1606A)
and found that a slow leak of 0.0006 - 0.0002 SLPM of He gas was detected as
3 LED lights on the Restek readout. A leak this slow would be ~860 mL of He gas
over the course of a day or about 1.1 mL of liquid He per day. That's less than
1/2 L of LHe over the course of a year, so the sensitivity is certainly enough
for our needs.
Like all detectors of this type, the only annoyance is how easy it is to flood
the detector with too high a concentration of He or with moist air, etc.
It's easy to recalibrate, but it can take a couple minutes and you have to
move the inlet far enough away that it's not affected by any He gas from the
leak, etc.
Another nice aspect of this Restek detector is you can detect N2 leaks as well.
I haven't used that feature nearly as much as the He detection, but there are
certainly times when that's useful.
We have used the Restek handheld unit very successfully. It has been a godsend.
It is certainly sensitive enough in our case to find almost every leak. I will say
that if your leak is very small it can be deceiving as to background drift. But
going back to the suspected leak point repeatedly does give you confidence.
There are some sudden drift issues. But more of an inconvenience and certainly
not bad enough given the price point.
We have 2 of the GLSciences units. They were indispensable when setting up
the helium recovery system. We never tried to use them to quantify anything
but they will find very small leaks! Never sniffed the magnet but we have
used them in the 5G line. These units will also do N2 and other gases, Helium
is red lights all others are green. These units are used often to check new
fittings and the whole system every year.
--
*Sameer Al-Abdul-Wahid* , Ph.D. *|* Manager
Nuclear Magnetic Resonance Centre *|* University of Guelph
50 Stone Rd E *|* Guelph, ON *|* N1G 2W1 *|* CANADA
519-824-4120 Ext. 58914 *|* s.wahid_at_uoguelph.ca ( s.wahid_at_uoguelph.ca )
http://nmr.uoguelph.ca/
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Received on Fri Aug 25 2023 - 13:53:46 MST