Hi Greg,

We convinced our lab designers to plumb the pump exhaust as an open split into a general-purpose ventilation system, with the notion that during initial pump down the exhaust might momentarily exceed the flow rate of the ventilation system and spill into the room (no big deal, since this is just atmosphere), and that during normal operation (99.99999999% of the time) there is hardly measurable flow.

Regards,
Ben

On Tue, Nov 1, 2016 at 1:02 PM, Gregory Henkes <[log in to unmask]> wrote:
Hi All,

Thanks for the usual rapid and detailed responses. Gerry, the LFM vs. CFM confusion was also where my mind went first when they said 250, fortunately I have the note in writing. CFM it is. 

50 m3/h or ~28 CFM seems to be the answer, for Thermo branded setups at least. 

Greg

On Nov 1, 2016, at 12:49 PM, gerard olack <[log in to unmask]> wrote:

HI Greg--

CFM or LFM?

A 4 or 5" diameter snorkel will need a linear flow rate around 250 LFM to get ca. 28 CFM, or around 50m3/h.

Otherwise you're right, it is way overkill--that one exhaust would be responsible for a complete air exchange in your room once every 5 or 10 min (ok I don't know the size of the lab).  And as Wolfram pointed out--there is basically no pump exhaust in normal operations.

Good luck!

take care,

gerry


On 11/1/2016 11:22 AM, David Gillikin wrote:
Hi Greg,

Here’s the info I got from Thermo when  building my lab:

rotary pump should be connected to an exhaust gas line leading
out of the building.
The inner diameter of the pipe should be at least 1.5 cm.

** Exhaust for EA/TCEA [CO,SO2,H2] to be positioned over or connected
to the conflo-IV = (50 mm ID for direct connect) with a slight negative
pressure and a suction rate of 50 m3/h. More than this will disturb
the Conflo split wells.

Cheers
Dave

_____________________________________________________________________
David P. Gillikin, Ph.D.
Associate Professor of Geology
Director: Union Stable Isotope Laboratory
Union College
Department of Geology
807 Union St.
Schenectady, NY 12308

Office phone: (518) 388-6679
Lab phone:     (518) 388-8741
______________________________________________________________________


From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Gregory Henkes <[log in to unmask]>
Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
Date: Tuesday, November 1, 2016 at 12:13 PM
To: <[log in to unmask]>
Subject: [ISOGEOCHEM] Exhaust venting of IRMS gases

Hello Isogeochemers,

Here’s one for the group that I can’t seem to find a solid answer to: What is the minimum flow rate of the vent used to remove pump exhaust from an irms? Bonus points if you can point me to a place where it is stated as part of some manufacturer’s spec. We’re building a new stable isotope facility at Stony Brook and this question has come up in the budgeting of air along with fume hoods, gas cabinets, etc. For whatever reason, our engineers have spec’d out 250 CFM from a relatively small diameter snorkel vent that will drop down near the instrument from the ceiling. Myself and others have pointed out that seems like absolute overkill - I’ve got visions of the Suck Cut from Wayne’s World if one were to get their head near this thing while working on the instrument. 

Seriously though, any insight would be really appreciated - my urging of something benign will be heard more clearly with some hard numbers… activate the hive mind!

Thanks,
Greg