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Post by coldspaces on May 24, 2018 22:31:53 GMT
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Post by ckfan on May 24, 2018 23:23:07 GMT
Wow, it’s always amazing to see one get taken apart. I hope the repair goes well!
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Post by birkie on May 25, 2018 2:05:24 GMT
Sorry to hear this machine got zapped, but glad to hear it is in good hands for a repair! The filter on the suction line is interesting - I'm guessing John put it there to protect against pieces of grit working their way out of the evaporator and into the check valve bore? It's good to know that it it is safe to do that, if it has been running these past few years without oil return issues. So after creating another crop circle Ooh - does this mean that the machine might have the possibility of R124 in its future...?
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Post by coldspaces on May 25, 2018 3:47:38 GMT
Sorry to hear this machine got zapped, but glad to hear it is in good hands for a repair! The filter on the suction line is interesting - I'm guessing John put it there to protect against pieces of grit working their way out of the evaporator and into the check valve bore? It's good to know that it it is safe to do that, if it has been running these past few years without oil return issues. So after creating another crop circle Ooh - does this mean that the machine might have the possibility of R124 in its future...? The filter was added to protect the check valve. Garrett feels it may have caused some restriction and wants to remove it If I think we should. If the Teflon coated windings are deemed to have been damaged by the so2 it will get 124.
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Post by turbokinetic on May 25, 2018 15:12:05 GMT
That is a good looking machine! So sorry to hear about it getting damaged. But, at least we know it is in good hands.
I'll be very interested to see what the inspection of the motor reveals. You would think that Teflon would not be affected by SO2 - unless there are some high temperature reactions, or some reaction which is being catalyzed by something else in the system.
My money would be on an effect of the power surge. Just curious about the backstory on the surge. In other words, how did Garrett determine that surges had happened?
Anxiously awaiting on the results!
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Post by timeswelding on May 25, 2018 20:15:20 GMT
That's a beautiful machine. With all due respect to the restorer, I can't imagine going to the trouble and expense of a motor rewind and then re-assembling with old wiring. Maybe it's just me. I sure hope you save it.
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Post by coldspaces on May 30, 2018 2:48:47 GMT
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Post by turbokinetic on May 30, 2018 3:51:54 GMT
Darn. Sad to see this.
How brittle has the insulating paper become? It seems like there has been some sort of deterioration of the material. Seems like the insulating paper got between the rotor and stator and made a line around the stator near the damaged area?
Does this look like a general deterioration issue (such as some chemical attack) or does it seem like a single point failure where there was a power surge which arced through the insulation paper?
Thanks for letting us know what you found!
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Post by coldspaces on May 30, 2018 4:33:15 GMT
Darn. Sad to see this.
How brittle has the insulating paper become? It seems like there has been some sort of deterioration of the material. Seems like the insulating paper got between the rotor and stator and made a line around the stator near the damaged area?
Does this look like a general deterioration issue (such as some chemical attack) or does it seem like a single point failure where there was a power surge which arced through the insulation paper?
Thanks for letting us know what you found!
The paper seems to be very brittle. It was all still in tact though as far as I could see. I broke the paper away from the shorted area to expose the burnt windings. The paper looked like the rest before i broke it away. Didn't look over heated near the bad windings even. The decision has been made by the owner to have it rewound for R124 rather than so2. A rewind for modern refrigerant allows the windings to be dipped and baked with a coating to hold the windings in place. No such coating is known for so2. The original windings were double layer of cotton insulation on the wire and wood insulators to separate them from the stator core and help hold them in place. The present Teflon coated windings move too freely up and down in the core. I could make the short go away by sliding them upward in the core. It may very well be that the weight and movement of the windings just plane wore through the paper as it got brittle.
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Post by ckfan on May 30, 2018 11:47:57 GMT
I’m sorry to hear this. I’m glad that the cause was found though. It’s so interesting to see the insides of a DR though. So if I’m following this correctly, you think that the cause of death was not directly related to the SO2 attacking the windings. Rather, since you can’t hold the windings in place as well they rubbed themselves to death. Eventually I want to rewind the DRA that I have and repair the evaporator leak and convert it to 124.
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Post by turbokinetic on May 30, 2018 14:14:38 GMT
The paper seems to be very brittle. It was all still in tact though as far as I could see. I broke the paper away from the shorted area to expose the burnt windings. The paper looked like the rest before i broke it away. Didn't look over heated near the bad windings even. The decision has been made by the owner to have it rewound for R124 rather than so2. A rewind for modern refrigerant allows the windings to be dipped and baked with a coating to hold the windings in place. No such coating is known for so2. The original windings were double layer of cotton insulation on the wire and wood insulators to separate them from the stator core and help hold them in place. The present Teflon coated windings move too freely up and down in the core. I could make the short go away by sliding them upward in the core. It may very well be that the weight and movement of the windings just plane wore through the paper as it got brittle.
You're probably right about the vibration playing a large cause in this failure. Also, when I expand the picture of the failure point, there appears to be a difference between the color of the paper used for the slot liners, and the paper used for the slot liner cover. It may just be the oil staining looks different. This effect (the difference in color between the liner and liner cover) seems to be present in all the slots, not just the damaged one.
I wonder if the liners and covers were in fact both actual PTFE-based materials? Were they possibly some other material which was not compatible with the SO2 or the temperatures involved? . One thing that comes to mind is this. The very common motor winding slot insulation material Nomex is (according to manufacturer's info) damaged by SO2 if there is any trace of water involved. If you know and trust the motor shop who did the wind, you can eliminate this as a possibility! Just thinking of all possibilities.
Having said that, it was probably a wise decision to start over with a dipped and baked winding and use a less chemically reactive refrigerant.
Was there a lot of debris in the sump, from the slot liners crumbling and falling into the oil from other places in the motor?
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Post by elec573 on May 31, 2018 3:05:24 GMT
It’s always amazing to me how prestine they look when opened up. Question do you try to mimize the open air it receives . Do you have a process you use to keep air to a minimum. To exposed parts ?
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Post by coldspaces on May 31, 2018 3:18:39 GMT
It’s always amazing to me how prestine they look when opened up. Question do you try to mimize the open air it receives . Do you have a process you use to keep air to a minimum. To exposed parts ? I did try to have it open for a short time only. Then I put the dome back on with 4 bolts only and purged it with nitrogen. It is setting with a 25 PSI nitrogen charge on it for now. I also ran the AC in the garage to lower the humidity before I opened it. I hope to open it again and look at things closer, then I will vacuum it and put a nitrogen charge in till the windings are ready.
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Post by coldspaces on May 31, 2018 3:25:00 GMT
Was there a lot of debris in the sump, from the slot liners crumbling and falling into the oil from other places in the motor?
The oil is very clean, there are what I thought were a few pieces of metal in the bottom. I will look at them closer next time I take the dome off.
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Post by birkie on May 31, 2018 3:51:40 GMT
Sad to hear of this failure mode, but now we know. That paper sure looks brittle in the pics! Thanks for sharing the updates. I'm a bit embarrassed that I haven't had a good block of time to get my DR3 on R124, but such is life. ckfan Are the windings bad on your DRA2, or are you looking to do so as a sort of prophylaxis?
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