# Am I Wrong Cleaning Silver Braised Contactor Pads with a Wire Wheel



## RUSKES (6 mo ago)

Thims said:


> I have been working with MV, 600v motor starters and trying to get them in better operating condition. One thing I tried was to clean the contact pads on a wire wheel. I noticed immediately following cleaning visible arc flash from the contactor cover holes(See link, 6 small holes). Operation is otherwise normal and efficient. Is this normal/safe? I see this as acceptable in there is a small point where the high volts and clean pads would arc the atmosphere gap, before physical contact from engagement. However, I want to ensure that I am not making a mistake. The contact pads appear to be solid silver braised onto copper arms. In this case I would consider continuing this regularly as Preventative Maintenance. However, I want to know for sure.
> 
> Am I safe in what I am doing and should I continue to do it for restoring these starters? Or am I building a “bomb” that will later become a bigger issue? What are your thoughts, concerns, advice?
> Thank you.
> ...


wire wheel is the wrong tool, it will make the surface to rough


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## Thims (2 mo ago)

RUSKES said:


> wire wheel is the wrong tool, it will make the surface to rough


Thank you Ruskes. I will start using brillow and be a bit more patient. I didn't think the wire wheel would be too abrasive...


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## backstay (Feb 3, 2011)

Somewhere on the truck I have a rubber stone that I use.


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## Thims (2 mo ago)

backstay said:


> Somewhere on the truck I have a rubber stone that I use.


I will give it a whirl. Thank you.


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## Wirenuting (Sep 12, 2010)

You got to be kidding me,,,,

Is this Hacks?


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## 460 Delta (May 9, 2018)

Those look like contacts out of a Furnas starter. The normal operating surface of contacts is “rough”. In operation, the hill and valleys interlock for an even greater amount of surface area.
My inspection is remove the arc cover and check for major wear or burning, and if none observed, reinstall the cover. No “dressing up” is done. I’m even reluctant to remove and reinstall used contacts because at least in my mind the relationship has now been shifted and the hill and valley interlocking is now off and will have to reseat itself at the cost of heat and wear.


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## kb1jb1 (Nov 11, 2017)

It is my understanding that the surfaces are plated with something that reduces the arc and burning. If you start to remove the plating, even at the microscopic level, you hasten the burning. 
Is this correct?


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## Thims (2 mo ago)

460 Delta said:


> Those look like contacts out of a Furnas starter. The normal operating surface of contacts is “rough”. In operation, the hill and valleys interlock for an even greater amount of surface area.
> My inspection is remove the arc cover and check for major wear or burning, and if none observed, reinstall the cover. No “dressing up” is done. I’m even reluctant to remove and reinstall used contacts because at least in my mind the relationship has now been shifted and the hill and valley interlocking is now off and will have to reseat itself at the cost of heat and wear.


They are 600v motor starters. Old, but they are pretty reliable of a build. I am just hoping to surf that 80's era build of solid silver contacts. 
I know I asked and am greatful for all input rendered forth. I would hate to then question. But I find myself confused on a few points.

- Why would you want the contact surfaces to be rough? Greater continuity would be achieved by a firmly seated, smooth/clean surface of conductive material. In which case, I would argue the positional alignment wouldn't hold as much bearing on continuity as a clean, smooth surface with proper pressure would. As the contactors, by design, will "reseat" the topical engagement evertime the coil energizes. In addition, as my experience has proven (with signals at least) regular "reseating" of continuity ensures good electrical "communication". 
Perphaps I am missunderstanding your words?

- Wouldn't the accumulated residual, more specifically in dirty environments, cause increased heat/wear on the dynamically contacting, high voltage contacts anyway?

Again, this is not in arrogance but learning.
Thank you.


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## Thims (2 mo ago)

kb1jb1 said:


> It is my understanding that the surfaces are plated with something that reduces the arc and burning. If you start to remove the plating, even at the microscopic level, you hasten the burning.
> Is this correct?


This is my biggest concern. But the contacts being dirty and the "day" short I don't have a good contrast to confirm the original state of the contactors.


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## CAUSA (Apr 3, 2013)

In brief
1-MV is not 600V it is higher.
2-The contacts have designed mating contacts by manufacture, with coating. They do have a cycle life and will erode over the cycle time. 
3-You replace contacts not clean. If you cannot get the contacts, then replace the contactor.

On a good quality contactor, you can get the components for them.

If you're burning up contacts find out why. There are many reasons. Start with the basics.

Size?
Duty cycle?
Load?


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## canbug (Dec 31, 2015)

If you don't have the correct tool a pencil erasure will work but nothing harder or more abrasive. 

Tim.


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## Thims (2 mo ago)

CAUSA said:


> In brief
> 1-MV is not 600V it is higher.
> 2-The contacts have designed mating contacts by manufacture, with coating. They do have a cycle life and will erode over the cycle time.
> 3-You replace contacts not clean. If you cannot get the contacts, then replace the contactor.
> ...


Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?

They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.

The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.


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## Thims (2 mo ago)

canbug said:


> If you don't have the correct tool a pencil erasure will work but nothing harder or more abrasive.
> 
> Tim.


Is their a correct tool for this?


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## kb1jb1 (Nov 11, 2017)

Thims said:


> Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?
> 
> They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.
> 
> The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.


Years ago I was told silver but IDK for sure.


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## Thims (2 mo ago)

kb1jb1 said:


> Years ago I was told silver but IDK for sure.


I would tip you for this very comment! It would be good.


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## splatz (May 23, 2015)

Different voltages and currents use different metals for the contact surfaces, they are designed so that the arcing cleans the contact surface rather than galls it when the contacts open and close. With low voltages and currents (such as signal as you mention) it's probably less of a factor. 

Seems like what you're doing would be like taking a wire wheel to your tires for better traction, you're removing tread. You may or may not improve the surface (more likely not) but you'll definitely shorten the lifespan.


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## Almost Retired (Sep 14, 2021)

Thims said:


> Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?
> 
> They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.
> 
> The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.


possibly where it is black it is not contacting and does not matter
if they are cycling frequently, look for Excessive pitting, other than that "Let it Be"
as mentioned, do not clean .... replace
once you clean you have destroyed the mating surface it developed when new
now it has to do some destroying to reseat itself .. this will cause much more wear
not to mention, once it finally reseats, it appears burned almost as much as before

if these contacts are actually silver, melt them off and sell for scrap when replaced
none of the contacts are silver since the early 2000's that i am aware of


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## gpop (May 14, 2018)

We did it with emery cloth glued to a flat piece of steel. Lay the steel down then hold the contact and work it against the paper to ensure its 100% flat. 

If you have deiced that the contacts are burnt and need to be replaced then it really doesn't matter what you do to the old set. We could get well over 30 years out of a allen bradley 509 that's being abused. IEC and sq-D starters we just replaced the complete starter and hoped we could get a few years out of the new ones.


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## Wirenuting (Sep 12, 2010)

Zog gave a great answer to this 12 years ago.




Zog said:


> Using a file or sandpaper can cause abrasive material to fall into the mechanism, causing shorts (Files) or binding (Sandpaper).
> 
> Scotchbrite is the industry standard for dressing contacts, if necessary.
> 
> ...



from this thread








Dressing contact points


Does anyone know a good source for purchasing a small, flexible file for dressing contact points on electrical starters and pressure switches? I used to try and use Scotchbrite or sand-paper, but the majority of the time it is quicker to use a file to get the customer back on line and replace...




www.electriciantalk.com


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## SWDweller (Dec 9, 2020)

The other thing to check is to see that the contacts are flat when closing. Any angle on them will create more of an arc and shorten the life of the contacts.
I do not know who taught you to use a wire wheel on contacts, I suggest you never listen to them again unless they are paying for the drinks after work.

The roughest thing I have ever used on contacts was a eraser. Then clean the contact with some solvent. When the contacts get beyond that replace them. You do just pour more oil in your engine or do you change it.

What kind of load does the motor have? Working at the mine the motors for our conveyors, the contracts on 15kv starters were replaced on the same month of the year every year. 

Where are you that your using 600v motors, and being in the USA. Does the protection device on this motor limit the amount of starts per hour? Fastest way to shorten the life of the motor starting it more than the MFG rated number per hour. I usually subtract one from what the MFG states.
Some of the operators I have worked around in the past did not care about the equipment.


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## MikeFL (Apr 16, 2016)

Tyco (now TE) has some good info online about relays and the physics behind the make/ break.
You actually want to have a little bit of an arc to keep the contacts functioning at best performance.
Let's see what happens when I try to drag one on here...

It worked! 
@Dennis Alwon can you take these from here and put them in your list?


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## Wardenclyffe (Jan 11, 2019)

At Michelin I was told to replace, never resurface contacts. Store room was full so That's what I Did,...


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## paulengr (Oct 8, 2017)

Thims said:


> This is my biggest concern. But the contacts being dirty and the "day" short I don't have a good contrast to confirm the original state of the contactors.


Worse. The contact tips wear as a matched set. You are not only stripping material you are altering that relationship, INCREASING arcing. At best you could remove and machine them down so you start out with a matched surface but it’s a waste of time and money.

Contact tip inspection is easy. ABB has some nice pictures. See bottom of page 8…



https://library.e.abb.com/public/ce3c940940e90386c1257d78002d8a93/1SFC101044M0201.pdf



Now here is the problem. Here is the latest Benshaw catalog. This is a common contactor you may recognize under several brand names. They put their list prices in the catalog. Street price is generally around 60% of this.



https://library.e.abb.com/public/ce3c940940e90386c1257d78002d8a93/1SFC101044M0201.pdf



So $592 list for a 180 A contactor, $452 for the contact tip kit. They don’t even sell kits for smaller models. And figuring 60%, you are saving a whopping $84 by buying a contact tip kit. You are also keeping the old springs, coil, strike plate, etc. These days usually I can call and buy a contactor off the shelf but the contact kits are almost all non-stocked.

That being said, I got a great photo of a severely arced contactor recently: Zoom in and you see perfect arc peaks.


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## Thims (2 mo ago)

splatz said:


> Different voltages and currents use different metals for the contact surfaces, they are designed so that the arcing cleans the contact surface rather than galls it when the contacts open and close. With low voltages and currents (such as signal as you mention) it's probably less of a factor.
> 
> Seems like what you're doing would be like taking a wire wheel to your tires for better traction, you're removing tread. You may or may not improve the surface (more likely not) but you'll definitely shorten the lifespan.


I truly love the analogy you just used. That makes A LOT of sense. I wish I could learn more about the pad coating, but am certain this is proprietary industry information...
Thank you Splatz.


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## Thims (2 mo ago)

Almost Retired said:


> possibly where it is black it is not contacting and does not matter
> if they are cycling frequently, look for Excessive pitting, other than that "Let it Be"
> as mentioned, do not clean .... replace
> once you clean you have destroyed the mating surface it developed when new
> ...


Truly appreciate. All of your inputs are guiding me in a solid direction. Though I am residing in slight "cleaning" with an eraser as a good practice. I think I am just going to drop the zeal and accept that they function. I have the eraser and budget for when they show signs of needing it.


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## Thims (2 mo ago)

gpop said:


> We did it with emery cloth glued to a flat piece of steel. Lay the steel down then hold the contact and work it against the paper to ensure its 100% flat.
> 
> If you have deiced that the contacts are burnt and need to be replaced then it really doesn't matter what you do to the old set. We could get well over 30 years out of a allen bradley 509 that's being abused. IEC and sq-D starters we just replaced the complete starter and hoped we could get a few years out of the new ones.


I had considered the Emery, however thought the wire wheel would be less abrasive with controlled pressure. I note your approach for those needed circumstances. Along this route I considered milling .005 (or so) off, however fixturing to ensure concentricity proved challenging. I am now since learning the peculiar maintenance practice of contactors. All of your advice and input has left me with "Let It Be" and use an eraser where needed during replacement.
Thank you.


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## Thims (2 mo ago)

Wirenuting said:


> Zog gave a great answer to this 12 years ago.
> 
> 
> 
> ...


This made my maintenance journal! I really appreciate your time and contribution, guiding my naivety in practice. Boyish ambition and professional aspiration brought me to this forum. Of which, I have found a good community and proven quality resource. I am eager to continue in a few conversations about the place and I appreciate the open commune of information. 
Thank you.


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## Thims (2 mo ago)

Wardenclyffe said:


> At Michelin I was told to replace, never resurface contacts. Store room was full so That's what I Did,...


This is the hardest part along this quest. The balance of cost effectivity to optimal preventative maintenance can be challenging. I would bet that is nice having a disposable store room. But a company of that size, such would be expected. 
Thank you Wardenclyffe.


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## KAE (Nov 24, 2021)

kb1jb1 said:


> It is my understanding that the surfaces are plated with something that reduces the arc and burning. If you start to remove the plating, even at the microscopic level, you hasten the burning.
> Is this correct?


Before I retired (after 43 yrs.) as a journeyman machine assembler (and millwright) I have built several hundred transfer switches. If there is arcing and pitting, more than likely it tried to switch under a load. I have also rebuilt hundreds of transfer switches and have always used scotch bright pads to clean them. If the surface is too pitted, the silver contact needs to be replaced for a solid contract surface,


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## Flashedout (4 mo ago)

I have also used baking soda and water as a solvent in the past which seemed to work well.. The eraser is always a good safe option, unless the contact are to the point of no return. Which in most cases replacement is your only option depending on the equipment.. I have also seen some 600v rated motor contacts fail shortly after someone decided to disassemble and clean... When I ask why did you take it apart in the first place? "They looked like they needed cleaning" was the answer.. So it turned out to become more maintenance than the PM that was performed.. The failure was caused by mis alignment and excessive arcing/heat.. I give you credit for taking the time to tend to your equipment.
My advice is to take good care with plenty of attention to detail when disassembling listed equipment, because you can end up with bigger headache than it's worth. Some times the saying "if it's not broke don't fix it" really does ring true.. Although proper PM's are a must..


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## Wirenuting (Sep 12, 2010)

Thims said:


> This made my maintenance journal! I really appreciate your time and contribution, guiding my naivety in practice. Boyish ambition and professional aspiration brought me to this forum. Of which, I have found a good community and proven quality resource. I am eager to continue in a few conversations about the place and I appreciate the open commune of information.
> Thank you.


The search function works well. 
Zog is a very well respected and knowledgeable member.


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## gpop (May 14, 2018)

Thims said:


> I had considered the Emery, however thought the wire wheel would be less abrasive with controlled pressure. I note your approach for those needed circumstances. Along this route I considered milling .005 (or so) off, however fixturing to ensure concentricity proved challenging. I am now since learning the peculiar maintenance practice of contactors. All of your advice and input has left me with "Let It Be" and use an eraser where needed during replacement.
> Thank you.


At some point in maintenance you will learn there is no right or wrong its more of a positive and negative thing.

Place i worked had over 1000 AB 509 contractors onsite plus another 60 large contractors. We were shut down 3 months of the year so we had time to pm everything and we were very much a run to failure plant.

Now dressing contacts in place would be a negative. 
Removing contacts is a positive as you get to clean them if required and you also get to check the bolts holding the contacts are tight. Its also a negative as the bolts are threaded into copper so you risk damaging the threads. (very easy to cross thread)

Our failure rate for a contactor not counting the one we abused the crap out of was less than 1 in 1000 per year. The abused one cycled for 3 seconds every 4 minutes and was so worn out after a year it was simply replaced. (never failed just got sloppy from so many cycles). 

After years of servicing the same equipment you get to know what needs cleaning, how the cleaning will hold up and what to expect in the future. My best advice is to never jump in head first. Try cleaning one then monitor it. 
If it looks good a week after see what it looks like in a month. If its already back to looking burnt up then you know its not working. I figure with a wire brush on a grinder its going to look just as bad as its impossible to keep it level and will have a scratched surface. 

Im not sure about eaton but i know better than to waste time on a sq-d or anything IEC.


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## paulengr (Oct 8, 2017)

gpop said:


> At some point in maintenance you will learn there is no right or wrong its more of a positive and negative thing.
> 
> Place i worked had over 1000 AB 509 contractors onsite plus another 60 large contractors. We were shut down 3 months of the year so we had time to pm everything and we were very much a run to failure plant.
> 
> ...


Too late! AB now sells IEC. There is nothing wrong with them except understanding.

If you are cycling THAT often it’s an IEC AC4 (NEMA ICS 2 has a similar category. If you look in the normal catalog info they show about 2 million cycles for AC3, normal duty. The recommended contactor for AC4 is usually about 100k to 150k cycles. Sizing up you can often greatly increase this to a million cycles. But don’t do this. Use a soft start or a VFD. You will make both the motor and starter last much longer.


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## JRaef (Mar 23, 2009)

Contacts should never be “cleaned”. Every time they are opened, there is an arc. The temperature of the arc is the same as the surface of the sun. Nothing survives it. So there is no reason to ever clean them. Carbon is not “dirt”, it is conductive. Leave it alone. 

These contacts are for either an old Allen Bradley starter or an old Furnas starter. They are set at an angle like that so that they “wipe” just a little every time they make (close). The contacts are INTENDED to have peaks and valleys corresponding to the other side. The more they “wear”, the deeper those peaks and valleys get and the BETTER they make contact. By “cleaning” them in any way, you are just removing material and hastening their demise.


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## dogleg (Dec 22, 2008)

Once a year I have to inspect a vintage 1924 controller for a 2400 volt 600 hp wound rotor motor. The contacts on the controller are for the resistor bank used in wound rotor motors. About every 3 years we have to resurface some of the contacts . We use a silver and copper phos flux rod and build up the pitted surface. Then we use a guide on a stationary belt sander to get the somewhat curved surface to match the original shape. The first time we flattened the surface it looked like the 4rth of July with nice sparks shooting off of the contacts. Once we matched the curvature of a less worn one it worked fine, I suppose they need to swipe not slam. Anyways no replacements for those nor the 250 volt dc coils for the contacts.


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## pokeytwo (Dec 6, 2015)

Contact surfaces self wipe when operated. Should never be abraded as the silver coating is thin. There are places that refurbish these. If the surfaces seem to be rough and dirty the coating may be near finished.


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## tonytonon48 (Jan 4, 2022)

I work on Automatic Transfer Switches and with the contactor type power panels, to clean the carbon off the arcing contact surface and main contacts (silver plating) we used Scotch Bright (green pad.) This works for NORMAL CONTACT WEAR! As others have mentioned, if it is abnormal wear, then the contact may have to be replaced. And, of course check for the CAUSE of the abnormal wear. We use a digital Ductor (AVO DLRO) instrument to measure the Ohms resistance of each pole. Sometimes the resistance increases after the cleaning because the Scotch Bright is too rough on the surface. In which case we end up using #600 grit sandpaper or emery cloth to bring the Ohms reading down. Make sure all of the grit is removed after the job is done.
I wrote this post before I read the one from Zog years ago and the 2nd page of this thread. All good info here, but for me, the bottom line when you're done is the micro-ohm Ductor reading.


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## Thims (2 mo ago)

SWDweller said:


> The other thing to check is to see that the contacts are flat when closing. Any angle on them will create more of an arc and shorten the life of the contacts.
> I do not know who taught you to use a wire wheel on contacts, I suggest you never listen to them again unless they are paying for the drinks after work.
> 
> The roughest thing I have ever used on contacts was a eraser. Then clean the contact with some solvent. When the contacts get beyond that replace them. You do just pour more oil in your engine or do you change it.
> ...


When I was first experimenting (on bench), I learned that faces should be parallel, otherwise they naturally vibrated or chattered. I turned to the possibility of machining the faces conecntric. However, the time demand to the respective benefit ruled towards not. But I am also working with early 80's, silver pads. No one taught me, though my own question led. In such, discretion guides. From comments made on this Forum, I have learned appropriate practices. I have been trying for pouring more oil in, yeah... But I now see why changing the oil is the better practice. 

Nah, this machine is a joke to Kv. It is simply running starters for a nominal 20 Amps per motor. Total machine ampacity is "maybe" 700 Amps. But from where I started, she is running the better.
Old, heavily used, rivaling, propriety she is... And it has been a headache, but Hell'a lesson. The 600v I don't know. Probably short steps by the engineers in play. 3 Phase 480v seems sufficient, however the rotational torque required probably is the draw for 600v... No pun intended.

Starts per hour? Hell, she turns on in the morning and starts when a part shows. I would love to apply your advice in experience, but this is not starts per hour type stuff. If money is being made she runs when product shows!


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## paulengr (Oct 8, 2017)

Under normal wear you shouldn’t be doing anything with contact tips. There is no carbon there. It is/should be pure metal. Some oxidation is normal. As contacts open/close there is always an arc. This heats up the surface and melts it a little. As the contacts close/open in many designs there is a slight sliding action that wipes the oxidation off. Each time it closes/opens you lose a tiny amount of material and the contacts slowly erode away. Inspection is visual. ABB has nice photos in their guidelines. Cleaning should not be necessary. You are just accelerating west. If you ripped off so much material you have to sand it down then replace lace contacts. 

The contact resistance test checks for spring pressure. If it is insufficient or contacts are badly damaged it fails, it isn’t a test for contact wear.

Instead of doing some crap that mostly causes damage try reading the entire maintenance section of the instructions. If it refers to standards such as NEMA AB4, or ICS2, read and follow those too. Follow maintenance standards such as NFPA 70B and stop doing things by the seat of your pants.

A certain switchgear maintenance company in the Virginia/West Virginia area often uses WD-40 to “lubricate” bearings on insulated case breakers. They find lots of breakers which tend to open/close slowly. They often fail DLRO tests because they like to sand contact tips smooth. Usually as they come back on repeat trips as the breakers “age” many more failures occur, not fewer. They are literally washing the grease out of the bearings replacing it with a light oil that evaporated and tearing up the contact tips. Then the only repair is to tear apart the breaker cleaning and regressing (replacing) bearings and contacts. That’s a shop job. You are basically doing almost the same thing


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## Wirenuting (Sep 12, 2010)

paulengr said:


> A certain switchgear maintenance company in the Virginia/West Virginia area often uses WD-40 to “lubricate” bearings on insulated case breakers.


WD-40 is great if your using it to protect the outer skin of the Atlas missile from rust and corrosion.


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