Hello Matt,
The main reason for "standby flow" for your cryoprobe is to protect your sample.
If the sample heater turns off for any reason, then the VT control also
turns off and the normal gas flow turns off (as an aside, we typically
use 535 lph, we might sometimes increase this a bit, but we never set it
below 500 lph).
You need to have a standby gas flow that turns on when the VT gas turns
off because the coils are operating at about 20 K, and they are
millimeters away from the sample tube. Without the standby gas flow,
there is a real chance that the solvent in your NMR tube will freeze,
and then you are likely facing a very expensive repair bill.
We typically have the standby gas flow set to 200 lph.
Cheers,
Bob.
On 2023-05-23 1:46 p.m., Matt Cliff via groups.io wrote:
> Hi all,
>
> We are currently auditing out N2 gas use, and I'm looking at whether I
> can reduce the standby gas flow through our cryoprobe systems. What do
> people currently use?
>
> My cryoprobe manual says this is probe specific, and the probe
> specifications say 600 l/hr, but I have it set at 535 l/hr. EDTE window
> specifies a standby flow, how low can this be? Given that the cryoprobe
> is sort of cold anyway (~10 deg C) what does the standby flow achieve?
>
> Thanks, and best wishes,
>
> Matt
>
--
Dr. Bob Berno
Manager, NMR Facility
McMaster University, ABB-156
1280 Main St. West
Hamilton, ON L8S 4M1
T: 905-525-9140 x24158 or x24686
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