Deryck:
We are in the process of setting up a He reliquification system from Quantum Design for the NMR instruments at the CCRC, with initial low pressure helium storage in bags, a Bauer compressor feeding 12 high pressure gas cylinders, and then going to a purifier and liquifier. We are set up to collect boil off during fills through a commercially available water to air heat exchanger to warm the gas. This is used with He gas going through the water circuit. When filling the 800 and 900 MHz magnets approximately 1 L liquid (750L gas) is boiled off per minute, with the amount less for lower field magnets that are filled at a slower rate. There is a back pressure of less than 0.5 psi going into the heat exchanger (800 and 900 fills), with very little pressure after this in the main line (probably less than 0.1 psi) going to the bags. (There is some flow restriction in the heat exchanger, but this does not seem to have any adverse effect on fills we have done with the heat exchanger connected to the exhaust.) This does depend on the sizing of your piping, of course, and back pressure vs flow for pipe can be calculated with tools available on the web. To isolate other magnets from any pressure fluctuations, particularly during fills, we will have back pressure regulators/manostats on them. Such were provided with 800 and 900 magnets anyway when they were installed. Quantum design is providing the regulators for the 600 and 500 MHz systems. The magnets have a three way valve at the exhaust port of the cryostat, with one position where normal boil off is directed to the pressure regulator, and the other directing the gas to the heat exchanger during fills.
David Live
David Live
Complex Carbohydrate Research Center
University of Georgia
315 Riverbend Rd.
Athens, GA 30602
706-542-6262
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From: Deryck Webb [dwebb_at_ualberta.ca]
Sent: Thursday, June 06, 2013 1:32 PM
To: ammrl_at_ammrl.org
Cc: Martha Morton; John Fowble; NORMAN CHU; Harker,Robert A; Bill Stevens
Subject: AMMRL: LHe Recovery/Reliquefaction - System pressure swings
Hello everyone,
Here at the University of Alberta we're on the verge of completing a campus wide helium recovery project, which includes almost 3km of recovery piping, a 500 cuft. gas bag, Bauer compressor, 500A purifier, RS compressor and 1410 liquefier (from Linde cryogenics). It has taken us this long to have everything in place as funding comes in fits and spurts. We'll be in operations in middle August.
One thing we want to bring into place is helium gas transfer during filling procedures. The process itself can be simple, but I'm finding resistance from other local users on the recovery line that don't want to be exposed to the increased pressure created from the influx of gas. Our preliminary experiments see an increase in recovery line pressure from 0.25 psi to 0.40 psi. Sometimes we get up to 0.5 psi (relief valves on the recovery piping open at 0.5 psi) at the end of a NMR fill.
In our local lab with 3 NMR systems this is not an issue as all systems are shutdown for cryogen filling at the same time. In the Chemistry department, however, application usage is so high that a helium fill can be happening, while another system meters away is still collecting potentially sensitive data. As well, MS and magnetometer users on different floors, who may not be coordinated with the NMR users, don't want any surprises with slight pressure increases on the helium recovery line they are attached to. It's hard to tell across the various applications what these pressure changes have.
We're now working on procedures and components that will mitigate pressure swings in the helium recovery piping throughout campus. It may be a combination of increased coordination of helium usage across campus coupled with the proper infrastructure to mitigate pressure swings from high flow recovery events.
A final consideration is the components involved with helium capture from lab to lab. The Iowa State system is amazing (LINK<
http://scs.illinois.edu/nmr/docs/HeliumRecoverySystemIowaState_JenniferRappDLO.pdf>) however our helium facility doesn't have the funds to install this extensive infrastructure into every lab space which has helium recovery. Our hope is to design a mobile apparatus which can be moved to a lab where a helium fill is occurring so we can invest once as opposed to 40 times. During a filling procedure a helium facility technician would assist local technicians with the filling of their application. This would give us better control over high flow events as well as simplify helium recovery to the end user who only has to monitor nominal day to day helium recovery.
Does anyone else recovering during high flow events have issues with other proximal helium applications on the same recovery line?
What have you done to minimize any effects?
Any recommendations on operations, infrastructure components or implementation are absolutely welcome.
Best Regards,
Deryck Webb
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Deryck Webb B.Sc, MBA - Operations and Services Supervisor
NANUC - Canada's National High Field NMR Centre
Room 103 Email: dwebb_at_ualberta.ca<mailto:dwebb_at_ualberta.ca>
NANUC Bldg. Phone: (780) 492-8530
University of Alberta Fax: (780) 492-9174
Edmonton, Alberta
Canada T6G 2E1
Received on Thu Jun 06 2013 - 10:48:30 MST