The grease is better than no grease. You want to protect the crimp from
the formation of oxides. In the Bell System we used a conductive grease
to help protect the connection. From the photo it appears that the
elements in this box allowed an oxide to form in the crimp and this
resulted in the failure. This type of terminal is not designed to
operate in a corrosive environment.
Check that application data sheets from suppliers like AMP to see limits
on usage.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Thursday, April 01, 2010 2:12 AM
To: [log in to unmask]
Subject: Re: [TN] Failed Ring Terminal
I have to disagree with Paul. That's the purpose of the Nye lubricant,
to keep the air away and it will do that for a very long time.
Solder makes the crimp stiff so then what happens is that the strands
just past the end of the crimp terminal are now brittle and don't bend.
If the wire is flexing a lot (vibration from the motor) then strands
break and you're right back where you started with the terminal heating.
Read these tech notes on the grease's properties
http://www.nyelubricants.com/pdf/NEW_8917_Marketing_WP.pdf
http://www.nyelubricants.com/pdf/nye_connector_lubes_v3.pdf
http://www.heavyequipmentforums.com/Forum/showthread.php?t=4394
"All electricians that work with high current and amps do have this type
of grease.
They add it to the cables before crimping together to get good
connection between the cable and crimped on shoes."
Crimp lugs are designed for crimping, not soldering. In the electrical
world, it is not compliant to solder a crimp connection.
Or, go ahead and solder the lug. The insulation on the PIDG crimp
terminal will melt and look awful, so cover it with shrink tubing.
Bob Landman
H&L Instruments, LLC
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
Sent: Wednesday, March 31, 2010 8:35 PM
To: [log in to unmask]
Subject: Re: [TN] Failed Ring Terminal
Bob,
I agree that it takes longer and is a pain to get it really nice but if
it was soldered you might not have to be the one that has to fix it...
The next owner would...
Paul
Paul Edwards
Surface Art Engineering
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Wednesday, March 31, 2010 2:37 PM
To: 'TechNet E-Mail Forum'; Paul Edwards
Subject: RE: [TN] Failed Ring Terminal
Paul,
I agree. Soldering takes SO much longer and it can make a mess of the
insulation, looks bad. But, if this terminal had been soldered it would
still be working.
Though, 40 Years in my Dad's barn is more than I would asks of
ANYTHING!
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
Sent: Wednesday, March 31, 2010 5:24 PM
To: [log in to unmask]
Subject: Re: [TN] Failed Ring Terminal
Bob,
A soldered crimp terminal is best for high reliability joints...
The surface of the individual strands of wire that makeup the conductor
oxidize (and/or corrode) because they are exposed to the environment and
increase the strand to strand resistance... As the current travels from
the conductor core to the contact surface area of the crimp connector it
differentially heats the strands in the conductor until you preferred
current paths... The Cu then starts to thermal cycle under load and
causes crystallization and failure of the Cu...
A solid solder joint eliminated this problem because of the soldered Cu
interfaces are complete involved in the solder joint.
Paul
Paul Edwards
Surface Art Engineering
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Wednesday, March 31, 2010 12:55 PM
To: [log in to unmask]
Subject: [TN] Failed Ring Terminal
Hi,
Why would a crimped ring terminal fail and over heat? Can anyone
suggest failure modes as to why the resistance would increase?
I would guess a soldered connection would be better?
See www.kondner.com/files/failedringterm.jpg
That insulator was yellow at one time it is now brown and the
insulation at that end of the wire is very brittle. The wire size is
#10.
This ring terminal came from a Furnas Electric motor starter for a 5hp
240V AC motor that draws about 28 amps. It was installed back in 1968.
It was installed in a dingy barn in a silo pit where most of the steel
enclosures are covered with rust. All kinds of nasty odors as there are
plenty of cows in the area. It is quite amazing that it went this long,
but I wonder why it failed.
The crimp seemed tight but it had obviously over heated. Other such
ring terminal on the same circuit are fine. The crimps were made in the
factory and not by some guy with a simple hand tool.
I ground off the edges which allowed me to open the crimp with minimal
wire damage. I was surprised that much of the wire looked quite clean.
I am just curious what folks would suggest.
Thanks,
Bob Kondner
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