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sci.physics.plasma+ADw-br+AD4-
From news+AEA-reznor.larc.nasa.gov Wed May 31 08:16:45
1995+ADw-br+AD4-
From: edruf+AEA-hyp06.larc.nasa.gov (Ed Ruf)+ADw-br+AD4-
Organization: NASA
Langley Research Center, Hampton, VA+ADw-span style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs-
+ADw-/span+AD4-USA+ADw-br+AD4-
Subject: Re: ELECTRICAL ARCING BETW. CONTACTS +ACY-amp+ADs-
HOUSING.+ADw-br+AD4-
+ADw-br+AD4-
In article +ACY-lt+ADs-3q5g60+ACQ-3ba+AEA-mojo.eng.umd.edu+ACY-gt+ADs-
skymed+AEA-halcyon.com (BJ) writes:+ADw-br+AD4-
+ACY-gt+ADs-24 MAY 95, 23:20 PDT+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ACY-gt+ADs-I
am interested in getting advice or comments on the following engineering+ADw-br+AD4-
+ACY-gt+ADs-problem.+ADw-span
style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs- +ADw-/span+AD4-Two electrical contacts are housed in a
stainless steel+ADw-br+AD4-
+ACY-gt+ADs-housing.+ADw-span style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs-
+ADw-/span+AD4-In some cases the housing is grounded and the contacts are at+ADw-br+AD4-
+ACY-gt+ADs-something
like+ADw-span style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs- +ADw-/span+AD4-150 volts.+ADw-span
style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs- +ADw-/span+AD4-After laser welding the housing shut it
is+ADw-br+AD4-
+ACY-gt+ADs-back-filled with Nitrogen +ACY-amp+ADs- Helium trace (for leak
detection).+ADw-span style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADs- +ADw-/span+AD4-In field+ADw-br+AD4-
+ACY-gt+ADs-service,
arcing occurs between the contacts and the housing.+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ACY-gt+ADs-Is there
anything thing to consider that would suggest a different+ADw-br+AD4-
+ACY-gt+ADs-back-fill
gas if we wanted to stay with the SS?+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ACY-gt+ADs-Is it possible that
the back-fill gas is getting ionized before or during+ADw-br+AD4-
+ACY-gt+ADs-the back-fill
process?+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ACY-gt+ADs-If anyone has had this problem and solved it we
would be interested in+ADw-br+AD4-
+ACY-gt+ADs-hearing your approach.+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ACY-gt+ADs-R.
K.+ADw-br+AD4-
+ACY-gt+ADsAPA-br+AD4-
+ADw-span style+AD0AIg-mso-spacerun: yes+ACIAPgAm-nbsp+ADsAPA-/span+AD4-This is an old
area with alot of available info in the open literature. +ADw-br+AD4-
Typically,
Sulfur Hexachloride (SF6) is a gas used for such applications. +ADw-br+AD4-
It is a
heavy, dielectric gas which is nontoxic and used for such applications. My
experience with it was with pressurized high voltage spark gap switches, +ADw-br+AD4-
but
the literature has much info on all possible uses. SF6 is also +ADw-br+AD4-
non-corrosive,
though you may get a litle sulphur depositing+ADw-br+AD4-
out over time, total
compatible will aluminum and SS.+ADw-br+AD4-
+ADw-br+AD4-
Ed Ruf+ADw-span style+AD0AIg-mso-spacerun:
yes+ACIAPgAm-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADs-
+ADw-/span+AD4-edruf+AEA-hyp00.larc.nasa.gov+ADw-span style+AD0AIg-mso-spacerun:
yes+ACIAPgAm-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADs- +ADw-/span+AD4APA-br+AD4-
Lockheed Engineering
+ACY-amp+ADs- Sciences Company+ADw-span style+AD0AIg-mso-spacerun:
yes+ACIAPgAm-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADs- +ADw-/span+AD4-(804)864-6356 Voice+ADw-br+AD4-
Hypersonic
AirBreathing Propulsion Branch+ADw-span style+AD0AIg-mso-spacerun:
yes+ACIAPgAm-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADsAJg-nbsp+ADs- +ADw-/span+AD4-(804)864-6242 Fax+ADw-br+AD4-
MS 168 NASA Langley
Research Center+ADw-br+AD4-
Hampton, VA 23681-0001+ADw-br+AD4-
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++wA8-br+AD4-
All
opinions are my own and in no way reflect Lockheed, NASA or anyone else.+ADw-br+AD4-
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++wA8-br+AD4-
+ADw-br+AD4-
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