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dlj04(at)josephson.com
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 Posted: Thu Jul 07, 2016 8:30 am Post subject: dielectric grease vs conductive grease: when and where |
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| Quote: | dielectric grease vs conductive grease: when and where
Summarizing some discussions Bob and I had some time ago, there is
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approximately zero need or use for grease in a properly constructed
aircraft electrical system. There are very specialized exceptions
(heatsinks of power semiconductors inside electronics, heat transfer
compound on certain sparkplug threads) but the conductivity you're
promoting is thermal, not electrical. Aircraft electrical connections
have to be tight enough that they don't come apart, forcing a
metal-to-metal connection of higher pressure than any grease will
withstand. The grease only serves to prevent air and water from reaching
metal parts that aren't in contact -- but if they are not in contact
anyway the grease will not help.
In cars, we have battery posts and terminals made of rough cast lead
that won't support the kind of pressure that copper lugs will, so some
amine grease (a variant of cosmoline, such as No-Ox-Id A-Special) is a
good idea to help the battery terminal conform to the post and seal out
the battery acid, but we hope you don't have that kind of terminal post
in your plane. It's great for trailer and motorhome lights, truck
battery posts, etc but we hope you don't have any iffy connections like
that in your airplane.
Conductive grease (containing metal dust) is used to solve one very
specific problem in high current building power wiring and has no place
in an airplane. If the surfaces are so rough that they need conductive
grease to make contact, fix the surfaces instead.
'Dielectric grease' made with silicone oil came into use because it's
available in a convenient tube and electronics techs have it already for
heat sinks. But again, no reason in an airplane unless you need to make
the surfaces slippery or exclude moisture.
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kenryan
Joined: 20 Oct 2009
Posts: 426
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| Posted: Thu Jul 07, 2016 9:18 am Post subject: dielectric grease vs conductive grease: when and where |
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Thanks everyone for the comments. How about grease for the specific purpose of mitigating corrosion, for example on grounds? Also what about on D-sub connections?
Sent from my Android. Sorry Steve. On Jul 7, 2016 8:38 AM, "David Josephson" <dlj04(at)josephson.com (dlj04(at)josephson.com)> wrote: | Quote: | --> AeroElectric-List message posted by: David Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>
| Quote: | dielectric grease vs conductive grease: when and where
|
Summarizing some discussions Bob and I had some time ago, there is approximately zero need or use for grease in a properly constructed aircraft electrical system. There are very specialized exceptions (heatsinks of power semiconductors inside electronics, heat transfer compound on certain sparkplug threads) but the conductivity you're promoting is thermal, not electrical. Aircraft electrical connections have to be tight enough that they don't come apart, forcing a metal-to-metal connection of higher pressure than any grease will withstand. The grease only serves to prevent air and water from reaching metal parts that aren't in contact -- but if they are not in contact anyway the grease will not help.
In cars, we have battery posts and terminals made of rough cast lead that won't support the kind of pressure that copper lugs will, so some amine grease (a variant of cosmoline, such as No-Ox-Id A-Special) is a good idea to help the battery terminal conform to the post and seal out the battery acid, but we hope you don't have that kind of terminal post in your plane. It's great for trailer and motorhome lights, truck battery posts, etc but we hope you don't have any iffy connections like that in your airplane.
Conductive grease (containing metal dust) is used to solve one very specific problem in high current building power wiring and has no place in an airplane. If the surfaces are so rough that they need conductive grease to make contact, fix the surfaces instead.
'Dielectric grease' made with silicone oil came into use because it's available in a convenient tube and electronics techs have it already for heat sinks. But again, no reason in an airplane unless you need to make the surfaces slippery or exclude moisture.
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