Jamie,

      The type of EAs I'm familiar with use an oxygen loop to deliver a set
amount of oxygen to the sample.  The loops require a constant trickle of
oxygen to refill them between samples.  On our EAs (Carlo Erba NA 1500 and
NA 2500) the flow rate through the loop is set with a hand operated
metering valve.  The NA 1500 uses a bleed rate of 25 to 30 mL/min and the
NA 2500 is a little higher because the waste oxygen is also used as a purge
gas for the autosampler before leaving the system.  If your system is of
the oxygen loop type, make sure your bleed rate is reasonable.  Other than
that, I think your looking at a leak.   Assuming that your tank, regulator,
and fittings leading to the EA are OK, if your copper is being consumed too
fast, it may be leaking internally.  For external leaks, a leak detector
(we use a Gow Mac) is very handy.  If you're planning to have a long
relationship with the machine, it's a good idea to take the time to map out
all the plumbing so you can make reasonable guesses about where to look.
Best of luck.


Steve

Steven Silva
U.S. Geological Survey
345 Middlefield Rd., Mailstop 434
Menlo Park, CA 94025
ph:  (650) 329-4558
fax: (650) 329-5590
email: [log in to unmask]





                      Jamie Kesae
                      Tanimoto                 To:       [log in to unmask]
                      <[log in to unmask]        cc:
                      EDU>                     Subject:  EA...O2 leak?
                      Sent by: Stable
                      Isotope
                      Geochemistry
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                      UVM.EDU>


                      03/09/2004 03:31
                      PM
                      Please respond to
                      Stable Isotope
                      Geochemistry






Hi all -

I'm relatively new to EA's and have what may be a excessively simple
question.  My oxygen tenk seems to be dropping quickly - it's gone from
2250 psi to 1400 psi in about 4 months.  I believe our previous tank
lasted much longer.  I've leak tested (with soapy tap H2O) all the
fittings that are between the oxygen tank and the EA and all the
fittings in the EA.  Does anyone have any suggestions for internal
sources of O2 loss?

Also, I noticed the metal fittings below the autosampler and above the
oxidation reactor tube are very hot to the touch.  Does anyone else
experience this?

Thank you!

J. Tanimoto