Thanks for all the responses,
I got about 14 pretty enthusiastic responses in favour of the electric pressure builders and 10 tried them but felt control was much better with a helium cylinder.
As most commercially available dewars come with two settings of 4 and 8 psi, many people are turning them on and off to maintain a lower flow rate, especially for lower field magnets. I assume that people that have been using this technique over the years build up a routine for each dewar size/magnet and manage to keep a pretty steady control of their fill rate. With higher field magnets the 4 psi setting is fine. Having a UHP helium cylinder available in case of heater failure is necessary.
We'll probably leave off the extra: since we will be recovering our boiloff, we are not terribly concerned about the extra helium use. Our chemistry stores keep the cylinders in stock, so we rarely have trouble getting one, and they last us for ages.
Several people mentioned that it is possible to get a level meter on the helium dewars, and recommended that as a more useful extra, and we will probably go that route.
Best wishes,
Tara
*********************************************
Dr. Tara Sprules
QANUC
Quebec/Eastern Canada High Field NMR Facility
www.nmrlab.mcgill.ca
phone: (514) 398-1721
fax: (514) 398-8254
3420 University St., Rm 023
McGill University
Montreal, QC, H3A 2A7
*********************************************
________________________________
From: Tara Sprules, Dr. <tara.sprules_at_mcgill.ca>
Sent: Friday, January 17, 2020 8:41 PM
To: ammrl_at_ammrl.org <ammrl_at_ammrl.org>
Subject: AMMRL: electric pressure builder for helium transfers
Hello,
We are looking into purchasing a 250L helium dewar to complement our helium recovery system (call for tender in preparation at last).
What are people's experience with the electric pressure builder for liquid helium transfers? Does anyone use them? Are their advantages/disadvantages? We've always pressurized with a tank of grade 5 UHP helium gas.
The system will be designed to capture all boiloff possible.
Thank you!
Tara
*********************************************
Dr. Tara Sprules
QANUC
Quebec/Eastern Canada High Field NMR Facility
www.nmrlab.mcgill.ca
phone: (514) 398-1721
fax: (514) 398-8254
3420 University St., Rm 023
McGill University
Montreal, QC, H3A 2A7
*********************************************
Received on Tue Jan 21 2020 - 12:44:12 MST