MG Set Busbar - Replace? - I need help fast

[mityeltu]

I have been asked to review some specifications for a situation that has come up during a refueling outage.

The MG set copper busbar has apparently lost some of the silver plating at the juctions. It has been cleaned and there is apparently no evidence of heating, leading everyone to believe it was vibration that has caused the loss.

Sadly, I have reviewed several specs but have not come across anything relating specifically to the silver plating.

The question is, what role does the silver play at the junctions of the bus, and what are the consequences of not having it?

Does it need to be replaced?

Does anyone know of a specifica reference in any standard (IEEE, ICEA, NEMA etc) relating to this issue?

I'm continuing to look in the plant specs, and will probably be contacting the manufacturer, assuming I can find out who made it, but I would like to have your input.

Thanks.

 

[BJ Conner]

Cool Amp - silver plating in a jar.

http://www.cool-amp.com/?gclid=CMSJq4rPyKQCFQr6iAodOTRe4A

 

[Jraef]

The silver plating is done to reduce joint resistance and protect from certain kinds of corrosion, i.e. oxidation and salts. If it is not vibration / abrasion that is removing the silver, I would be concerned for corrosive gasses. H2S is common if this is a WWTP or a geothermal or coal fired power plant. H2S not only can corrode the silver, it can grow "whiskers" that can end up causing faults.

Great white paper on the subject, including cool photos.

Cool-Amp is great stuff, but I would first eliminate the possibility that you have something else going on. If it is H2S, the silver in the Cool-Amp might make it worse.

 

[mityeltu]

Thanks, this is a PWR nuc.

I'll look into this and share with eng super to see wat they think about the cool amp.

Thanks for the white paper.

It's out of my expertise. How would I eliminate other causes? Is there tell tale signs for hydrogen sulfide or other gaseaous corrosives?

 

[BJ Conner]

Thanks, this is a PWR nuc.

I'll look into this and share with eng super to see wat they think about the cool amp.

Thanks for the white paper.

It's out of my expertise. How would I eliminate other causes? Is there tell tale signs for hydrogen sulfide or other gaseaous corrosives?

Your health and safety people should be able to tell you if there is H2S around. Very dangerous stuff.

If your plant was originally built in the 70s or 80s construction requiremnts were less stringent than now.
IF in 1970 I were installing an MG set and saw the buss was bare copper I would order some Cool-Amp write an FCN and do it. Suppliers of equipment were more approachable then and willing to make decisions. Now you have to wait months to get a decision. Everybody is running scared and afraid to make a decision.
Way back we connected silver plated bus (on a nuke)using Vasaline. Thats what the vendor rep said to use. Now you use the same stuff repackaged in vendor marked jar with a 12 diget part number.
In short ther may not be a record or spec on what you found.

 

[mityeltu]

That seems to be the case. I also have been informed that any replating of bus is sent out and handled by a third party.

Have been informed that no causetic meterials (gaseuos or otherwise) can be found in the area of interest. The only caustic material I know of in the plant (aside from the core) is the borated water. This bus is located up above the reactor in the rad containment area in the reactor trip switchgear.

I have alos been given additional information as to the location of the actual problem on the bus. The silver has apparently been "rubbed" off at the insulator support for the bus.

Since this is not an electrical connection, is this even a problem? Aside from the fact that something CAUSED the silver to be removed, and the unlikelihood that it was caused by a corrosive environment, can I just say that it was probably vibration, that the bus should have all attachments tightened to specs, have maintenance monitor the bus on a more frequent baseis than current plan, and put this to bed?

What are your thoughts?

Thank you for all the quick assistance. I really appreciate it.

 

[BJ Conner]

Sounds like it's time for a full blown root cause analysis. The insulator could have been o"off gassing" ( if made of plastic ), the insulator could have been tracking, is it installed in the correct orentation, etc etc. welcome to the nuke world of the 21st century.

 

[mityeltu]

I've never heard of any of the things you just mentioned. I didn't know there was a wrong orientation for a busbar. Can you elaborate?

Where would I go to get additional information on this subject? Is there a particular reference book, tech manual, national standard?

 

[danickstr]

A little Vaseline is a good idea if you think the plating loss is due to some sort of chemical reaction.

Funny I suggested using grease on outside wirenuts and switch screws in a aluminum bell box and some sparky chastised me for using "flammable" product in an electrical enclosure.
I didn't even bother to tell him that if the 1/20 of a gram of vaseline catches fire in one of my boxes, there has already been some sort of tragedy that will have destroyed the surrounding area.

 

[BJ Conner]

I've never heard of any of the things you just mentioned. I didn't know there was a wrong orientation for a busbar. Can you elaborate?

Where would I go to get additional information on this subject? Is there a particular reference book, tech manual, national standard?

I ment wrong orientation of an insulator. The one with fins are supposed to be vertical if they are subject to moisture. The "Cups" oriented downward so they don't collect water.
Bus bar installed flat could collect water or dust that would run or fall off if it were run on edge.
If the machine is fan cooled there could be dead spots on the bus.
A through "root Cause analsis " looks at all possible causes . The first thing you see when something goes wrong may be a symptom no the cause.

I am not trying to be silly but there are people in the nuke industry who think this way. Don't want to see you get supprized.

 

[hurk27]

Your health and safety people should be able to tell you if there is H2S around. Very dangerous stuff.

If your plant was originally built in the 70s or 80s construction requirements were less stringent than now.
IF in 1970 I were installing an MG set and saw the buss was bare copper I would order some Cool-Amp write an FCN and do it. Suppliers of equipment were more approachable then and willing to make decisions. Now you have to wait months to get a decision. Everybody is running scared and afraid to make a decision.
Way back we connected silver plated bus (on a nuke)using Vaseline. Thats what the vendor rep said to use. Now you use the same stuff repackaged in vendor marked jar with a 12 digit part number.
In short ther may not be a record or spec on what you found.

The reason most applications will require parts and material to have part numbers, are tracking, very common in government installations, this is so if there is a failure, the failed cause can be tracked back to the source, I.E.. the manufacture, to make sure required specs were followed and met the required standard, it all has to have a paper trail.

Never worked in a Nuc plant but have worked for company's who did make parts for government contracts and have done some installs on government property's, which all had their special specs and requirements, and following the paper work was critical.

I got my butt reamed once for using dielectric grease (non flammable) on a buss connection on one of those jobs, and was told if it wasn't in the specs it doesn't get installed even if it is a better idea.

 

[mityeltu]

I appreciate that.

I got the RCA, one of my colleagues is working on one right now due to rotor damage.

I was serious too though. Is there a good reference for all the stuff you mentioned? A good book on buswork and problems associated with it?

Thanks again for all the help.

 

[BJ Conner]

I appreciate that.

I got the RCA, one of my colleagues is working on one right now due to rotor damage.

I was serious too though. Is there a good reference for all the stuff you mentioned? A good book on buswork and problems associated with it?

Thanks again for all the help.

Good free stuff here.
http://www.hubbellpowersystems.com/catalogs/connectors/DJ.pdf


http://www.hubbellpowersystems.com/literature/connectors/AEC-41.pdf

Powel switchgear has a lot of technical info on line.

 

[zog]

Is this a safety related system? That will make a world of difference on how to handle, including which 3rd parties are certified to do the work and how you aquire parts. (10 CFR appendix B)

Some photos would be helpful.

 

[dmagyar]

What's the preventative mainteance program?

What's the preventative mainteance program?

Along with the refueling are you doing any PM?

It wasn't mentioned in the earlier text.

When you're considering what caused the plating getting removed and possibly being caused by motion/vibration, re-torquing all the buss connections seems warranted.

On the number of the nuk's I worked on in the mid seventies I never noticed any PM on anything that had been previously installed during earlier stages of construction. With the construction duration covering six or more years there's plenty of time for movement and mechanical connections to loosen up.

In another industry & while continuing the installation of fit-up (over about six years) on a class one clean room here in California. We did PM on all the sub-stations and associated switchgear about once a year, this included re-torquing all buss connections, including insulators. Every year we used a different paint stick to mark the newly torqued joints. Easy way to determine what was completed vs still needing attention.

 

[mityeltu]

no pictures. Sorry. Yes, TONS of PM. In fact, because we are behind a good deal, we are simply replacing many of the breakers - not my idea. The PM schedule is 3/6 or 5/10 years depending on the equipment. No safety related (as defined in 10cfr), but I personlly tend to hold all bus, breakers and related equipment as safety related.

Anyway, the issue seems to have resolved. The bus is not going to be replated as the silver was "rubbed" from where the insulator was bolted. As this is an indoor installation, weather is not an issue. The plan is to retorque all connections on the bus. and inspect all bus-bus connections (I'm sure that will get done in a timely fashion, just like the 3 year late pm's)

Oh well, getting better at putting out the fires. Thanks for all the fast help. I hope I can repay sometime.

 

[hurk27]

no pictures. Sorry. Yes, TONS of PM. In fact, because we are behind a good deal, we are simply replacing many of the breakers - not my idea. The PM schedule is 3/6 or 5/10 years depending on the equipment. No safety related (as defined in 10cfr), but I personally tend to hold all bus, breakers and related equipment as safety related.

Anyway, the issue seems to have resolved. The bus is not going to be replated as the silver was "rubbed" from where the insulator was bolted. As this is an indoor installation, weather is not an issue. The plan is to retorque all connections on the bus. and inspect all bus-bus connections (I'm sure that will get done in a timely fashion, just like the 3 year late pm's)

Oh well, getting better at putting out the fires. Thanks for all the fast help. I hope I can repay sometime.

Very understandable, (well not for a nuc site) but many company's are run like this, and as far as repaying, just stick around and share the knowledge you have gained over the years, to maybe help another get through a situation they don't understand that you might have the correct answer for.

 

[zog]

no pictures. Sorry. Yes, TONS of PM. In fact, because we are behind a good deal, we are simply replacing many of the breakers - not my idea. .

Replacing breakers because you are behind on the PM's? That is nuts.

 

[dmagyar]

Make sure you've got a check list !

Make sure you've got a check list !

Another thing to make sure is to check in tools after completion of the individual PM operations. With the short time table, mistakes seem to multiply (Haste makes overtime) is an addage that is true more times than not.

If someone forgets a torque wrench it usually gets left across the bussing. That is something we really were on the lookout for.

Keep everyone safe, it's better to skip some of the items on the "wish list" vs trying for everything and someone getting hurt.