[labnetwork] Berkeley's reply - N2 Flow Meters and/or Flow Computers for tracking distributed nitrogen usage

[Robert M. Hamilton]

The UC Berkeley NanoLab supports two LN vessels. We meter 
nitrogen fed to the NanoLab and the labs in two associated 
buildings. In addition, we've built and manage a LN fill 
station used by an assortment of researchers to fill 
portable Dewars. We use nitrogen metrology and the billing 
methods we inherited from the Microlab, which we supersede. 
We bill N2 and LN at fixed-charge, i.e. we do not further 
break down our costs for those who wish to hook up to the 
nitrogen facilities we support.

N2 metering consists of a Hoffer-brand turbine meter within 
our LN vessel cage. The Hoffer monitors and totalizes all N2 
use. N2 mass flow meters are used in two of the three 
buildings supplied with N2. One of these is a Brooks 
thermal-mass-flow meter and the other a Kurtz.  Calculation 
for N2 use by the third building is done by decrementing the 
use of the other two from the Hoffer total. We installed a 
flow-fuse to the third building to keep their operation from 
downing ours should there be a breach in their distribution 
lines. This building operates with less professional staff 
and is therefore subject to issues with their N2 plumbing 
setups. Our computer resource utility monitoring system, 
"RUMS" monitors and allows us to remotely access data such 
as N2 use and vessel fill needs. I often use my smartphone 
to monitor utilities and our LN vendor uses a link to RUMS 
to determine vessel levels and coordinate fills.

We operate two LN vessels, a 9000 and a 3000 gallon vessel. 
The 3000 gallon vessel is held at ~60 psi while the 9000 is 
operated at 150 psi. There is a crossover manifold that 
allows us to feed N2 from either vessel in the case of an 
equipment failure. When we have to switch feeds we reset 
each vessels pressure-building circuit. The smaller vessel 
is run at lower pressure to minimize flash-loss for LN needs 
as two molecular beam epitaxial systems demand ambient 
pressure LN. Also, Dewar fills take much longer when the LN 
source for such fills is at high pressure.

It seems the broader question is the civics of operating a 
shared-research facility. The NanoLab, like the Microlab 
before is a self-supporting recharge operation. As such, we 
pay for all our nitrogen costs including the purchase of 
bulk LN and the cost of purchasing, facilitating and 
maintaining LN vessels and their associated plumbing . We've 
chosen to share our nitrogen based on the spirit of a 
"common good". The disadvantage is PI's who are not familiar 
with the complexity of an operation do not gain the sense 
for the real costs associated with a utility. Regrettably, 
there are even a few who knowledgeably take advantage of a 
situation.

It would be nice if nitrogen came from the air, for free. 
This would solve the issues of cost and I'd be grateful for 
not get those 4 AM phone calls, from the LN delivery 
drivers, about fill issues.

Best regards,
Bob Hamilton

Robert M. Hamilton
Marvel NanoLab
University of CA at Berkeley
Rm 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
bob at eecs.berkeley.edu
(e-mail preferred)
510-809-8600
510-325-7557 (Emergencies)


On 8/19/2011 1:51 PM, John Shott wrote:
> Labnetwork:
>
> Like many facilities, I suspect, we have a single LN2 tank 
> that is used for delivery of gaseous nitrogen to the 
> entire building.  While our shared laboratory is 
> undoubtedly the largest user of that nitrogen, there are 
> also a number of private labs in the building that consume 
> nitrogen.  Because they do not pay for it, however, they 
> have little incentive to conserve nitrogen.  Additionally, 
> because we don't have great metering of our own nitrogen 
> usage, we probably use more than we should in our facility.
>
> Do any of you have experience with either totalizing flow 
> meters and/or flow computers that can be used for tracking 
> nitrogen flow and usage at 15 or 20 distributed points 
> that end up communicating to a central data collection point?
>
> Any experience with systems of this type would be greatly 
> appreciated.
>
> Thanks,
>
> John
>
>
>
>
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