Magneblast AM-13.8 Timing and Motion Velocity

[bumblebee52]

We have a number of old style "last forever" mechanical Magneblasts. Per EPRI, AM-13.8 nominal timing is 100 ms for Close and 50 ms for Open. I spoke with GEXPRO and apparently these values are meant for a newly manufactured breaker or GE factory rebuild.

Does anyone out there have any information regarding timing values in terms of ranges min/max for these style magneblasts?
What would be a good minimum time for these breakers? I am assuming nominal is equivalent to a maximum value that you do not want to exceed.

How about velocity/motion tests? Anyone have any data with respect to this? I was under the assumption that 15kV did not really require velocity/motion. I spoke with DOBLE and they do have a setup to do this but it requires some drilling into the breaker.

What about tear down on these? Do we send back to factory or forklift them out to a well lighted warehouse and start disasembly? It looks like access to roller bearings will require this.

Is it really important to use the GE grease as specified in the GE Manual or can we use an equivalent like molykote 3451?

 

[DTR2011]

The grease is very important. There are many documented cases of unapproved grease being used and causing problems later on. I believe the "GE Red" is Mobile 28.

Main contact timing should probably be acceptable. If GE cannot supply the original velocity/acceleration curves you may be chasing your tail on this.

If you are in the US, there are many qualified service companies that can rebuild your breakers on site. Others may offer pick up / drop off services and rebuild them in their own shops.

I used to work in an OEM breaker shop and we did not (per our factory spec) perform time travel analysis on our 15kV class breakers. We measured main contact timing before and after a rebuild of the mechanism.

 

[dpmac]

We have a number of customers with late 60's early seventies AM breakers. Mostly 15kV, 1200A, 1000MVA 3H and 4H breakers. Although they only have a few hundred operations we have found that the sealed bearings become quite stiff and prevent proper operation and this in turn cause other issues. A total tear down and rebuild is required. There are a number of shops that can do this for you. I don't see the benefit of doing it on site unless you have a reasonable inventory of parts, proper test equipment and very skilled people with nothing else to do. The 1000MVA racking assy bushings and gears will also tend to fail depending on your standard procedures (open and lock out or open rack down and lock out) We have had to replace a number of these over the past few years so remember to check yours out. It is no fun getting a 1000MVA breaker out of cell with stripped racking mech gears.

I remember reading there was an instance of a repair shop doing complete rebuilds on Magnablasts using Mobil 28 throughout. They found the breakers actually traveled too fast and failed to latch. I believe Zogs people may have been involved in the research so he should be able to expand on that.

 

[Zogzog]

They sure don't build many things these days as well as they did those AM's.

I have never seen any minimum times for AM's, but have for other MV breakers, typically the minimum is around 50-60% of the maximum. I have tons of timing data for these, I have a 5kV 1200A nuclear safety related (1E) in my shop now that came in the shop in decent condition, 15 years since we last did a refirbishment on it and incoming timing tests were abour 80mS close and 42mS open, in the process of refirbishment so I don't have the "after" times on it yet. We do time travel on all MV breakers as part of our SOPs.

GE has some published velocity specs for these, but I have never seen any plant require these tests, even nuclear, they all refer to the EPRI table (times) you posted.

A proper refirbishment of these takes some special equipment and not something I would recommend doing in a warehouse. It is best to send them to a qualified shop (I recommend you check qualifications, procedures, references, etc) for a refirbishment, or if you want them done on site we have mobile breaker shops designed specifically for this sort of thing

http://photos.gcbsinventory.com/trailers/

I would stick with the Mobil 28, Molykote 3451 has very different properties than 28, I would not consider it an equivilant. Those 2 greaes also have different bases that can react with each other and cause issues so best to stick with the OEM recomendation.

If you need any more data or have questions you can contact me here.

http://www.cbsnuclear.com/contact-us.htm