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Bruce Tolleson,<br>
<br>
You'll have no issues with 5% H2 in N2 in a vacuum chamber. H2 in
air has a lower flammable limit (LFL) of 4.7. The lower explosive
limit is more like ~19% in air under ideal conditions. Given a
starting point o 5% H2 in pure N2 the LFL will be higher. <br>
<br>
To adjust this for reality I'll share my experiences. I routinely
used 20% H2 in N2 to seal vacuum tubes with an open flame and never
saw combustion. Ditto for 10%. These mixes were used for decades
before me in UC Tube Laboratory before I joined that group so there
is a long history of safety. Hi-vacuum brazing was routinely done
under vacuum with forming gas added as a reducing agent (and often
pure H2).<br>
<br>
Regards,<br>
Bob Hamilton<br>
<br>
<div class="moz-cite-prefix">On 5/1/2014 7:39 AM, Bruce Tolleson
wrote:<br>
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<p class="MsoNormal">Dear Labnetwork,</p>
<p class="MsoNormal"> I have a project that requires forming
gas (5% hydrogen, 95% Nitrogen) for gettering to reflow metal
in a vacuum chamber. Has anyone done forming gas in a vacuum
system and what precautions are required for the pumping
system?</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>Bruce E. Tolleson</span></p>
<p class="MsoNormal"><span>Rochester Institute of Technology</span></p>
<p class="MsoNormal"><span>82 Lomb Memorial Drive, Bldg 17-2627</span></p>
<p class="MsoNormal"><span>Rochester, NY 14623-5604</span></p>
<p class="MsoNormal"><span>(585) 478-3836</span></p>
<p class="MsoNormal"><span><img id="Picture_x0020_1"
src="cid:part1.05000609.08080806@berkeley.edu"
alt="http://www.rit.edu/~962www/logos/tiger_walking_rit_color.jpg"
height="60" width="90"></span><span></span></p>
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<pre class="moz-signature" cols="72">--
Robert Hamilton
University of California at Berkeley
Marvell NanoLab
Equipment Eng. Mgr.
Room 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
<a class="moz-txt-link-abbreviated" href="mailto:bob@eecs.berkeley.edu">bob@eecs.berkeley.edu</a>
Phone: 510-809-8600
Mobile: 510-325-7557 (Emergencies only)
e-mail preferred
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