[Amps] Dielectric grease for roller inductors?

[Jim Thomson]

##  already  read  it  several  times  in  the  last  year....  +  JIs  comments  on  qrz +  qth.    Conducto  lube  is  75%  pure  silver  and  25%  castor  oil......  NO  grease used.    The  silver  plated  edge  wound  roller  + 1  inch  square  silver  plated cu  tube  +  end pieces,  all  use sliding  contacts.....  everything is  silver  plated.  Sliding  contacts  ride  on  both  sides  of the  .375 inch, edge  wound  roller.    My old  roller  used a  pair  of  pulleys and a HUGE  SPRING between em to put a  lot of pressure  on the  pulleys..which  ride  on  the  EDGE of  the  edge  wound  roller.     

##  conducto  lube  is  used  in  industry  for  sliding  contacts  that  are  silver  plated.   noalox,  graphite,  penatrox, etc, are  not  used  on silver plated  anything.     At  the  telco  I  worked  at,  we  used...  copper  kote on  copper  buss  bars....  which  were  bolted.   Copper  powder in  grease. 

##  Im  up  for a  good  experiment.   I  have  2  of  these  silver  plated  rollers.  so  one  with dielectric  grease..and  the  other  with  conducto  lube.  Apx  15A  flowing through  the  roller..in  the  hb  amp.

##  Below  is  from  jis site In  the  url. 
Jim   VE7RF
 

    Contact arcs have the ability to alter composition of greases. Silicone greases can be converted by arcs to silicone carbide, which is highly abrasive. For this reason, SILICONE  GREASE  should be avoided when contacts are "hot switched" and have ANY  chance of arcing. 

 The suspended powder creates a problem that does not exist with dielectric grease. The suspended metal must be FULLY  COMPATIBLE  with the metals being clamped. This means conductive grease is application specific. If the metals being clamped are incompatible with the grease's suspended metal powder, the connection will eventually fail. This is what happened in our CATV system connectors. The connections were a mix of copper, aluminum, and steel. The cable shields were aluminum, the trunk center conductors cables were copper clad aluminum. Drop cables were aluminum shields and connectors, with copper clad steel centers. Our records showed a much higher incidence of corrosion failure using conductive grease. Corrosion failure rate dropped significantly, almost to zero, when we switched to pure dielectric grease.

In bolted or clamped connections,  I have no opinion if conductive greases help or are necessary. I feel like they help, but I'm not sure if that is true. I use Noalox on clamped aluminum slip joints in antennas because it is generally less expensive than silicone dielectric greases and it appears to last longer. I NEVER use conductive greases on push fit electrical connectors, or if I am unsure of metal to grease compatibility.  
Conductive greases should specifically match materials being clamped. Conductive greases should never be used in low pressure electrical connectors, or in connectors with multiple terminals



From: Kim Elmore 
Sent: Thursday, January 2, 2020 6:29 PM
To: Tom Hellem 
Cc: MU 4CX250B ; Jim Thomson ; amps at contesting.com 
Subject: Re: [Amps] Dielectric grease for roller inductors?

See https://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm for the full treatise. Bottom line is the“conductive” grease refers to its thermal, not electrical, characteristics.  

Kim N5OO